We're a team (re)building a Fiero for the Lemons series. It ran previously with a 3.4 TDC and a 282, currently we're working towards converting it to a L26 3800 with an F23 5 speed. We've sourced a couple engines, though we're unsure at this point of their mechanical state. We also have four F23 transmissions, two cavalier, one FY1 and one M84 (junkyard sent us the wrong one). No one on the team has any experience with Fieros so this will likely be a thread of many questions. I appreciate any and all help.
To start, my understanding of the coolant elbows is that they only feed the heater core. If so, I'd like to remove them entirely and bypass the heater core by threading each inlet and running a short hose between to maintainbypass flow. I found a few mentions indicating this has been done, but I'm struggling to find actual documentation of it beyond some specs such as thread size and type (3/4" and 1" NPT) and a warning about the metal being thin. Anyone have any further details?
Secondly, are there any recommendations for a cable throttle body besides the northstar 96-99 or 2k+? We're running a Microsquirt for engine management and the stepper motor IAC eats up a significant amount of I/O on the ECM. The MAF sensor also appears to be a frequency type which is incompatible with our ECM, although we'd like to be able to run a blended MAF/MAP setup, it isn't strictly necessary. I suppose the ideal setup would be a 75mm cable throttle body with a 2 or 3 wire PWM IAC valve and a lip to mount intake tubing so we can run an in-line voltage-based MAF, if we decide to run a blended MAF/MAP setup.
I'm sure we'll have many more questions to come as the build progresses. We're also currently debating how we want to frankenstein the transmissions to get our 3.63 FDR while getting the cavalier bellhousing and maintaining reasonable mounting options, if anyone wants to weigh-in on that, I'm happy to hear it.
[This message has been edited by 87FieroLemons (edited 04-21-2025).]
I'd like to remove them entirely and bypass the heater core by threading each inlet and running a short hose between to maintain bypass flow.
I just wanted to comment on the necessity of maintaining enough flow for the bypass. I found out what happens when the bypass flow is restricted too much when I temporarily bypassed a leaky heater core with too small of a fitting used to connect the hoses. It resulted in excessive pressure against the thermostat.
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[This message has been edited by Patrick (edited 04-21-2025).]
I just wanted to comment on the necessity of maintaining enough flow for the bypass. I found out what happens when the bypass flow is restricted too much when I temporarily bypassed a leaky heater core with too small of a fitting used to connect the hoses. It resulted in excessive pressure against the thermostat.
Yes, I've definitely read about this happening, collapsing the thermostat. Any recommendation on a minimum diameter? I am definitely concerned about keeping the engine cool. The previous 3.4 TDC seized from overheating. The biggest struggle in this series with Fieros seems to be the cooling system. The best recommendations I've read are a mixture of a coolant swirl pot and bypass hoses in critical spots to allow for air to separate itself from the system. Not going to pretend I understand any of that well enough to implement it as of yet, but I'm trying. The other, less conventional idea is moving the radiator much closer to the engine.
We're a team (re)building a Fiero for the Lemons series. It ran previously with a 3.4 TDC and a 282, currently we're working towards converting it to a L26 3800 with an F23 5 speed. We've sourced a couple engines, though we're unsure at this point of their mechanical state. We also have four F23 transmissions, two cavalier, one FY1 and one M84 (junkyard sent us the wrong one). No one on the team has any experience with Fieros so this will likely be a thread of many questions. I appreciate any and all help.
To start, my understanding of the coolant elbows is that they only feed the heater core. If so, I'd like to remove them entirely and bypass the heater core by threading each inlet and running a short hose between to maintainbypass flow. I found a few mentions indicating this has been done, but I'm struggling to find actual documentation of it beyond some specs such as thread size and type (3/4" and 1" NPT) and a warning about the metal being thin. Anyone have any further details?
Secondly, are there any recommendations for a cable throttle body besides the northstar 96-99 or 2k+? We're running a Microsquirt for engine management and the stepper motor IAC eats up a significant amount of I/O on the ECM. The MAF sensor also appears to be a frequency type which is incompatible with our ECM, although we'd like to be able to run a blended MAF/MAP setup, it isn't strictly necessary. I suppose the ideal setup would be a 75mm cable throttle body with a 2 or 3 wire PWM IAC valve and a lip to mount intake tubing so we can run an in-line voltage-based MAF, if we decide to run a blended MAF/MAP setup.
I'm sure we'll have many more questions to come as the build progresses. We're also currently debating how we want to frankenstein the transmissions to get our 3.63 FDR while getting the cavalier bellhousing and maintaining reasonable mounting options, if anyone wants to weigh-in on that, I'm happy to hear it.
my 2.8 is running 5/8 inch heater hose and the oem fittings for the heater, ugly but functional, my solution to the smaller size was a few more hose clamps, the correct way to do that would probably be finding a 5/8s to 1/2 adapter or sautering a bigger fitting on inplace of the smaller one honestly? no. you can modify the throttle body to make it cable driven though depending on the style (did it on a 07 triton to get it working in a 80s truck even though it hurt me very much to put that junk in that f150) as for the overheating? ford taurus fan. moves 4000 cfm ir something ridiculous and solved a overheating 350 in a fiero with a stock rad, plus a 454 swapped s10 (looking forward to doing it myself)
[This message has been edited by cartercarbaficionado (edited 04-21-2025).]
You might get away with 1/2", but considering that the two I.D. hose sizes on the heater core are 5/8" and 3/4", you probably should go no less than 5/8" to be totally safe.
Very excited to see this car getting back on the track. Since you are running a Microsquirt you need to look to see if MS2 coding accepts a MAF table, I honestly haven't looked, the only MAF Megasquirt set up I have done was MS3 code. Also since you are planning a 3800 the cool thing about their ignition system is you get to use the original ICM and only require a single output from the Microsquirt to control timing, the cranking bypass isn't super needed for a race car, ive done one 3800 powered buggy that way. If you have questions there is a weird thing with that ICM when tuning, every time you flash the ecu it think the ICM has had an error and goes to base timing, so you need to restart the car each time you flash a tune or you will be at static 10 degrees advanced, that took awhile to learn
New is the throttle body, you can get a Northstars throttle body, drive the IAC in to fully closed and work it with just the throttle screw since again you are a race car, if you want you can then set up a 2 or 3 wire PWM IAC externally routed to the intake past the throttle body and use the FIDLE off the Microsquirt
As for that car, I actually did the original wiring harness on the stock ecu and helped with the Microsquirt as well and ran the car one race. The motor actually died from the water in the block freezing from what I understood not from overheat at a race, I do think they had one engine fail early in the cars career from overheating, but by the time I was a part of anything all of that was sorted out
The 3800 heater core lines, since you won't likely be needing or using a thermostat shouldn't have any problem with both of them being capped, in theory you will have plenty of flow through the factory thermostat housing and the factory water pump and timing cover. Some of the 3800sc swaps I have done we used the lower intake manifold to feed coolant to the heater core, some of the buggy swaps I have done we capped all those ports, no issues with overheating, and Buggy's are hard to keep cool
Oh... I somehow missed that this was going to be swapped over to a 3800 (and possibly without a thermostat). My experiences with a 2.8 may not then apply here.
[This message has been edited by Patrick (edited 04-21-2025).]
It will be fun to watch the build! Post lots of photos!!!
There is a nice Fiero Lemons car that runs here in the San Francisco Bay Area. It does quite well.
I have a 1987 Fiero GT track car but don't race it.
We're definitely aware of a couple other teams that run these cars with some success. It's our first venture into road racing, much less Lemons. Our family has a bit of a background with drag racing but that's a very different world. I'll see what I can do about getting some photos posted.
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Originally posted by cartercarbaficionado:
my 2.8 is running 5/8 inch heater hose and the oem fittings for the heater, ugly but functional, my solution to the smaller size was a few more hose clamps, the correct way to do that would probably be finding a 5/8s to 1/2 adapter or sautering a bigger fitting on inplace of the smaller one honestly? no. you can modify the throttle body to make it cable driven though depending on the style (did it on a 07 triton to get it working in a 80s truck even though it hurt me very much to put that junk in that f150) as for the overheating? ford taurus fan. moves 4000 cfm ir something ridiculous and solved a overheating 350 in a fiero with a stock rad, plus a 454 swapped s10 (looking forward to doing it myself)
We're more concerned about air developing in the system from boiling the water. With such a long cooling system and cast iron heads, it seems like there's a high likelihood. We do need to source another fan and I am aware of some of the junkyard favorites (Taurus, Lincoln MK VIII, etc.).
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Originally posted by Patrick:
You might get away with 1/2", but considering that the two I.D. hose sizes on the heater core are 5/8" and 3/4", you probably should go no less than 5/8" to be totally safe.
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Originally posted by Patrick:
Oh... I somehow missed that this was going to be swapped over to a 3800 (and possibly without a thermostat). My experiences with a 2.8 may not then apply here.
Understood! Any and all information is welcome. The 3800 does bring unique challenges but the Fiero is kind of a challenge irrespective of powertrain.
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Originally posted by eph_kay:
Very excited to see this car getting back on the track. Since you are running a Microsquirt you need to look to see if MS2 coding accepts a MAF table, I honestly haven't looked, the only MAF Megasquirt set up I have done was MS3 code. Also since you are planning a 3800 the cool thing about their ignition system is you get to use the original ICM and only require a single output from the Microsquirt to control timing, the cranking bypass isn't super needed for a race car, ive done one 3800 powered buggy that way. If you have questions there is a weird thing with that ICM when tuning, every time you flash the ecu it think the ICM has had an error and goes to base timing, so you need to restart the car each time you flash a tune or you will be at static 10 degrees advanced, that took awhile to learn
New is the throttle body, you can get a Northstars throttle body, drive the IAC in to fully closed and work it with just the throttle screw since again you are a race car, if you want you can then set up a 2 or 3 wire PWM IAC externally routed to the intake past the throttle body and use the FIDLE off the Microsquirt
As for that car, I actually did the original wiring harness on the stock ecu and helped with the Microsquirt as well and ran the car one race. The motor actually died from the water in the block freezing from what I understood not from overheat at a race, I do think they had one engine fail early in the cars career from overheating, but by the time I was a part of anything all of that was sorted out
The 3800 heater core lines, since you won't likely be needing or using a thermostat shouldn't have any problem with both of them being capped, in theory you will have plenty of flow through the factory thermostat housing and the factory water pump and timing cover. Some of the 3800sc swaps I have done we used the lower intake manifold to feed coolant to the heater core, some of the buggy swaps I have done we capped all those ports, no issues with overheating, and Buggy's are hard to keep cool
Chris
Chris, very cool to run into someone who's familiar with this car.
We definitely intend to maintain the microsquirt. All the documentation I've read seemed to indicate that microsquirt and MS2 support MAF standalone or blended MAF/MAP. However, B&G firmware supports frequency MAFs but only on a specific pin and MSExtra firmware doesn't support them at all. So, seems like a voltage MAF, if any, is the safest route. This is my first time wiring/tuning an engine so I welcome any advice you have to offer.
As to the throttle body, I'm not sure it's in our interest to maintain MAF but my counterpart purchased a 96-99 northstar throttle body whose front is designed only to connect to it's bolt-on MAF. The more I research the more I think we may need to just toss it and push forward in a different direction. Ideally a 75mm +/- that comes stock with a PWM IAC to avoid unnecessary complexity. I definitely want to try and reduce I/O requirements for items that aren't offering us a speed or reliability advantage, my teammate has even discussed boost in the future so the more pins available in the future, the better. We don't have an adapter plate as of yet, so we're not committed and I think we should be able to fab one ourselves.
It's interesting to hear your recounting of the engine failure. We were told it had seized from overheating, although I would be unsurprised to hear it sat and froze. We've definitely discussed the pain it is likely going to be, cycling coolant and water constantly, to be in compliance with Lemons' requirements while keeping the cooling system from electrolysis or freezing.
I hadn't necessarily considered eliminating the thermostat. We're pretty green to this, so I won't pretend to know if that's common or the accepted practice. My initial concern would be dramatic temp swings, from leaving track to pitting and being back on track, making thermal cycling a problem for expansion sensitive items (rings, gaskets, etc.). Considering how often we're going to have to pit with a relatively meager fuel capacity, it may be quite a few temp swings although I acknowledge your experience doesn't reflect that.
Originally posted by 87FieroLemons: Chris, very cool to run into someone who's familiar with this car.
Yeah I can't take credit for the build, but Adrian and Keith did awesome with the set up and it was a blast with the TDC in there on track
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Originally posted by 87FieroLemons: We definitely intend to maintain the microsquirt. All the documentation I've read seemed to indicate that microsquirt and MS2 support MAF standalone or blended MAF/MAP. However, B&G firmware supports frequency MAFs but only on a specific pin and MSExtra firmware doesn't support them at all. So, seems like a voltage MAF, if any, is the safest route. This is my first time wiring/tuning an engine so I welcome any advice you have to offer.
What you will likely learn is MAF tuning isn't enough more accurate for 90% of builds to need it and you will be able to do a Speed Density tune that is more than adequate. My VW Rabbit has a VR6 with turbo with motorcycle throttle bodies, I used a MAF on the build as I was quite happy with how MAF tuning goes with HP tuners on the 3800sc swaps I had done, with MS3 code the MAF table is its own table, then you build a MAP table that is a modifier for the MAF table, then when you tune the MAF table you can't use Autotune, you have to data log the runs, then pull the log into Megalog Viewer and looks at a histogram plot to find where the MAF is off by, then hope you haven't compensated in the MAP tune for a MAF issue and chase your tail. Its much easier to just go full Speed density, of the 35 megasquirts I have installed only 1 uses MAF, a couple use Alpha N(TPS only) but most use Speed Density tables
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Originally posted by 87FieroLemons: As to the throttle body, I'm not sure it's in our interest to maintain MAF but my counterpart purchased a 96-99 northstar throttle body whose front is designed only to connect to it's bolt-on MAF. The more I research the more I think we may need to just toss it and push forward in a different direction. Ideally a 75mm +/- that comes stock with a PWM IAC to avoid unnecessary complexity. I definitely want to try and reduce I/O requirements for items that aren't offering us a speed or reliability advantage, my teammate has even discussed boost in the future so the more pins available in the future, the better. We don't have an adapter plate as of yet, so we're not committed and I think we should be able to fab one ourselves.
You will not find a single PWM IAC built into a throttle body that I logical to use, Ford has it on a few things, but its big and clunky and large ford throttle bodies tend to be expensive, plus the Northstar(not the one you have, the next generation unit) fits to the fiero v6 throttle cable with such little modification its a no brainer
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Originally posted by 87FieroLemons: It's interesting to hear your recounting of the engine failure. We were told it had seized from overheating, although I would be unsurprised to hear it sat and froze. We've definitely discussed the pain it is likely going to be, cycling coolant and water constantly, to be in compliance with Lemons' requirements while keeping the cooling system from electrolysis or freezing.
If I understand the story correctly years ago a local ish dealership ended up having 3.4 TDC crate motors cheap, they popped up at a few different locations around the same time, which is why you see so many of them out there. They built the car with a complete Z34 donor car with the TDC and the getrag 284(I think thats the number). That motor was run for a long time but I think it's the one that overheated and seized. I bought a few of the crate motors, Adrian bought a few of the crate motors, well maybe 1 and I bought 2, but he ended up buying both of mine from me. So one went into the car(I think its the current engine you have in the car) it ran for years and many races, its the car that got the Microsquirt installed onto, and it went up until the drained block had just enough water in it to crack the block while the car was parked over one winter.
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Originally posted by 87FieroLemons: I hadn't necessarily considered eliminating the thermostat. We're pretty green to this, so I won't pretend to know if that's common or the accepted practice. My initial concern would be dramatic temp swings, from leaving track to pitting and being back on track, making thermal cycling a problem for expansion sensitive items (rings, gaskets, etc.). Considering how often we're going to have to pit with a relatively meager fuel capacity, it may be quite a few temp swings although I acknowledge your experience doesn't reflect that.
Not sure if no thermostat is the exact answer, but if you run a controller on the fan(I use Hayden 3653 mounted in the front to trigger the ground trigger form the original AC wiring of the car to activate the fan) they you can run your fan on a switch and on the controller, turn the switch of when you go to the pits and the fan will cycle keeping the temp within check, you will be surprised having the radiator at the front it will be super efficient, and being disconnected from engine its even more efficient. Then you will be putting enough heat into the system that the short amount of driving from track to pit to refuel you won't lose too much temp and won't have the car running some of the time so I don't think you need to worry about much. There is a theory that gets proven on different engines where if the thermostat isn't in the system the size of that point of flow is too big and will flow TOO much coolant too quickly not giving enough time for the radiator to dissipate the heat and people will put a flat plate with a smaller hole in it to restrict flow to keep the coolant from flowing too quickly. I would imagine the extra length of line in a mid engine application will slow flow a little, and the fact that you are going to be staying between 3k and 7k rpms 90% of your time you are going to be flowing ALOT of coolant and I doubt the "non restricted" flow will cause any problems, but it will be a play it by ear kind of situation
Originally posted by eph_kay: Yeah I can't take credit for the build, but Adrian and Keith did awesome with the set up and it was a blast with the TDC in there on track
They seemed like good folks and definitely enjoyed reminiscing about the car.
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Originally posted by eph_kay: What you will likely learn is MAF tuning isn't enough more accurate for 90% of builds to need it and you will be able to do a Speed Density tune that is more than adequate. My VW Rabbit has a VR6 with turbo with motorcycle throttle bodies, I used a MAF on the build as I was quite happy with how MAF tuning goes with HP tuners on the 3800sc swaps I had done, with MS3 code the MAF table is its own table, then you build a MAP table that is a modifier for the MAF table, then when you tune the MAF table you can't use Autotune, you have to data log the runs, then pull the log into Megalog Viewer and looks at a histogram plot to find where the MAF is off by, then hope you haven't compensated in the MAP tune for a MAF issue and chase your tail. Its much easier to just go full Speed density, of the 35 megasquirts I have installed only 1 uses MAF, a couple use Alpha N(TPS only) but most use Speed Density tables
Yeah, that matches up with everything I've been reading about MAF and megasquirt. Sounds like something that definitely isn't for a fresh initiate to engine tuning. I had mentioned multiple times that we may just want to stay speed density, particularly with boost being in the possible future, but I'll relay that it's definitely not a useful investment in time or energy for us. Honestly, I was heavily hoping autotune would do a fair amount of the heavy lifting. While I'm not afraid to learn anything new, my head seems to be getting pretty full anymore with the multitude of things I'm expected to know.
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Originally posted by eph_kay: You will not find a single PWM IAC built into a throttle body that I logical to use, Ford has it on a few things, but its big and clunky and large ford throttle bodies tend to be expensive, plus the Northstar(not the one you have, the next generation unit) fits to the fiero v6 throttle cable with such little modification its a no brainer
I just figured with us being in a position to make our own adapter plate, we may as well exercise the flexibility and pick something that ticks all of the boxes.
So the options seem to be: 1) A throttle body with no IAC or a fully closed IAC and a standalone pwm bypass valve 2) Adjust the throttle plate for a reasonable hot/cold idle and run without a valve
I think we're inclined to want to retain some level of idle control so the standalone valve may be the direction we need to investigate.
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Originally posted by eph_kay: If I understand the story correctly years ago a local ish dealership ended up having 3.4 TDC crate motors cheap, they popped up at a few different locations around the same time, which is why you see so many of them out there. They built the car with a complete Z34 donor car with the TDC and the getrag 284(I think thats the number). That motor was run for a long time but I think it's the one that overheated and seized. I bought a few of the crate motors, Adrian bought a few of the crate motors, well maybe 1 and I bought 2, but he ended up buying both of mine from me. So one went into the car(I think its the current engine you have in the car) it ran for years and many races, its the car that got the Microsquirt installed onto, and it went up until the drained block had just enough water in it to crack the block while the car was parked over one winter.
They recounted a late night venture to a GM dealership wherein some cash changed hands and ~3 engines, if I remember right, were acquired. They seemed to think it was a 282 trans in the car and they also had a spare for it that we now have, as well as the spare crate engine you likely used to own still sealed up and everything. We just felt like the 3800 was a better direction from a cost, availability and reliability perspective and should also lose a little weight from the specs I can find online compared to the TDC. The F23 was an easy choice considering how dried up the 282/284 stock is and the shift quality improvements. They said the microsquirt was the result of chasing a misfire that ended up being an intermittently bad coil if I remember right, tried everything before they stumbled on it.
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Originally posted by eph_kay: Not sure if no thermostat is the exact answer, but if you run a controller on the fan(I use Hayden 3653 mounted in the front to trigger the ground trigger form the original AC wiring of the car to activate the fan) they you can run your fan on a switch and on the controller, turn the switch of when you go to the pits and the fan will cycle keeping the temp within check, you will be surprised having the radiator at the front it will be super efficient, and being disconnected from engine its even more efficient. Then you will be putting enough heat into the system that the short amount of driving from track to pit to refuel you won't lose too much temp and won't have the car running some of the time so I don't think you need to worry about much. There is a theory that gets proven on different engines where if the thermostat isn't in the system the size of that point of flow is too big and will flow TOO much coolant too quickly not giving enough time for the radiator to dissipate the heat and people will put a flat plate with a smaller hole in it to restrict flow to keep the coolant from flowing too quickly. I would imagine the extra length of line in a mid engine application will slow flow a little, and the fact that you are going to be staying between 3k and 7k rpms 90% of your time you are going to be flowing ALOT of coolant and I doubt the "non restricted" flow will cause any problems, but it will be a play it by ear kind of situation
We definitely have no intentions of spinning the 3800 to 7k! lol. Considering the stock cam starts falling off ~5200 rpm, we weren't aiming to shift much higher than 5500. So I think, as we're fans of the fairly conservative route, a bypass hose and a thermostat will likely be the route we go, pending complications to that plan. I do know the microsquirt can trigger the fan relay, if we have the I/O to spare, but we could also go the temp switch route. I researched that in the past for a different project, using a temp switch that can trigger a multi speed fan via a Volvo 740 relay.
I may have missed something in reading through the post, but why don't you use the PCM which goes with the 3800 motor? You may have a fairly difficult time to set up the ignition without it; sensors, no ICM, etc... Not impossible to do, but quite a lot of trouble never the less.... The GM PCM (+ ICM) is hyper reliable and tunable.
For the cooling, make sure the system maintains pressure. I had a bad radiator cap and it would loose a little pressure on the track when pushed hard. You are right that the heads start to "boil" in this case. Once fixed, and the pressure maintained, my 3800 turbo never overheated again. Keep the thermostat as well, just drill a small 3mm bypass hole in it. (Old school hotrod knowhow.) Oh, and make sure to replace the plastic coolant elbows from the lower intake with something stronger. If not, this will be the first thing to go wrong once you race a 3800.
Anyway, good luck with this build and I can't wait to see the car doing the 24H race.
------------------ "Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero https://youtu.be/hUzOAeyWLfM
[This message has been edited by Frenchrafe (edited 04-22-2025).]
I'll jump in and say that the car already has the Microsquirt ECU on it. And yes the OEM system is nice and tunable, but it doesn't have Wideband integration or control for the fuel tables, I've heard you can do live tuning on the 3800sc ECU, but personally have never done it. I have tuned about a dozen 3800sc and turbo Fieros on the stock GTP ECU(including a m122 big cam intercooler dune buggy which was a huge pain ) and making the tables happy, trying to watch the Wideband during power pulls to remember when you go to change the tables and trying to make the car have the ignition timing that is simple and consistently expected can be annoying.
Now I am not saying the stock ECU is bad, I just personally like a Megasquirt over a stock ECU for a lot of reasons. This isn't my build and for their set up a stock ECU might be a better option, but there are limitations to it for sure(there are plenty of limitations to megasquirt as well).
Also Frenchrafe, the Microsquirt can run the stock ICM and it does work awesome, keeps the dual crank triggers and everything so the motor starts fast and is super consistent and stable readings
I may have missed something in reading through the post, but why don't you use the PCM which goes with the 3800 motor? You may have a fairly difficult time to set up the ignition without it; sensors, no ICM, etc... Not impossible to do, but quite a lot of trouble never the less.... The GM PCM (+ ICM) is hyper reliable and tunable.
For the cooling, make sure the system maintains pressure. I had a bad radiator cap and it would loose a little pressure on the track when pushed hard. You are right that the heads start to "boil" in this case. Once fixed, and the pressure maintained, my 3800 turbo never overheated again. Keep the thermostat as well, just drill a small 3mm bypass hole in it. (Old school hotrod knowhow.) Oh, and make sure to replace the plastic coolant elbows from the lower intake with something stronger. If not, this will be the first thing to go wrong once you race a 3800.
Anyway, good luck with this build and I can't wait to see the car doing the 24H race.
Honestly, no desire to jump through any hoops for a factory PCM when a proven aftermarket option is in place with all of the support eph_kay already mentioned above. While I understand it is the standard practice in this world (Fiero conversion) and brings with it emissions compliance and other benefits, they just aren't relevant to us and our needs. We will be running the stock C3I with the ICM however, just triggered by the microsquirt.
A bad radiator cap is actually what they claimed cause the overheat and seize on the TDC. We did already find that one of the under-car coolant tubes is bad and appears significantly corroded. My teammate found some aluminum tubes of a similar diameter that we think we're going to swap in place. The bypass hole is definitely an idea to consider, I just know I want to eliminate the coolant elbows, whether by capping or tapping for alternative fittings and a bypass hose. The cooling system is probably my greatest concern for the car, Fieros are notorious for overheating in Lemons apparently.
Thanks for the well wishes, we'll do our best to bring justice to the car.
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Originally posted by olejoedad:
I am also curious about the rationale behind using an aftermarket computer rather that the rock solid, highly tunable GM PCM.
As explained above, no real reason to run a factory PCM, ignoring that we don't have one.
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Originally posted by eph_kay:
I'll jump in and say that the car already has the Microsquirt ECU on it. And yes the OEM system is nice and tunable, but it doesn't have Wideband integration or control for the fuel tables, I've heard you can do live tuning on the 3800sc ECU, but personally have never done it. I have tuned about a dozen 3800sc and turbo Fieros on the stock GTP ECU(including a m122 big cam intercooler dune buggy which was a huge pain ) and making the tables happy, trying to watch the Wideband during power pulls to remember when you go to change the tables and trying to make the car have the ignition timing that is simple and consistently expected can be annoying.
Now I am not saying the stock ECU is bad, I just personally like a Megasquirt over a stock ECU for a lot of reasons. This isn't my build and for their set up a stock ECU might be a better option, but there are limitations to it for sure(there are plenty of limitations to megasquirt as well).
Also Frenchrafe, the Microsquirt can run the stock ICM and it does work awesome, keeps the dual crank triggers and everything so the motor starts fast and is super consistent and stable readings
Chris
My guess would be that this comes down to familiarity. Many folks in the GM world are familiar and comfortable with the tuning options available to them and, in most cases, an aftermarket non-emissions compliant device isn't even an option. Naturally, preference goes to what's most often employed and proven to work well enough. I'll out myself in saying that I have a classic project car that's a Mopar and tuning is much more constrained in the Chrysler world so my natural tendency is definitely to jump straight to an aftermarket ECU, when that's an option.
If you have any wiring diagrams/documentation/configurations surrounding how you tied the 3800 to a Microsquirt, I'd love to peruse them. Do the stock crank and cam sensors work without any mods? I haven't looked to see if they (you?) did any mods to the microsquirt in the car to make it work with the TDC. Do you pull them directly from the sensors or do you pull them from signals output from the ICM? If from the ICM, how does the sensor vref and sensor ground play into that? I'm full of questions... The only actual documentation I can find about C3I is from 2005 and it was referencing different hardware than a V3 microsquirt, of course.
[This message has been edited by 87FieroLemons (edited 04-22-2025).]
For the factory GM PCM, it's not a question of emissions*, it's a question of not blowing your engine up with a bad or under developped tune. Auto tune won't cut it in my experience. Reach out to Darth Fiero here (Sinister Performance http://www.gmtuners.com). He'll sell you a good tune with the PCM for less money than you would spend on custom sensors, non standard ignition parts and all the hassle to have to redo every thing from the ground up in terms of fuel maps, ignition tables, etc... Other YouTubers have tried going MicroSquirt, LS coils and custom pickups on the 3800 only to have real problems with the ignition and finally melting a piston.
I've run MegaSquirt on old 6.6L V8s with carb to EFI conversions; it works OKish. But for a 3800 turbo application, with the particularities of the 3800, I studied the options and I decided that those who came before me (Dark Horizon, JustinBart, etc...) knew which was the better solution. They had already blown enough engines and tried a ton of different mods to show that in the end, the factory PCM is still the best.
*You get the EGR deleted and you go for a huge 3 inch Corvette MAF in the tune with Darth Fiero. So not at all emission compliant.
------------------ "Turbo Slug" - '87 Fiero GT. 3800 turbo. - The fastest Fiero in France! @turboslugfiero https://youtu.be/hUzOAeyWLfM
For the factory GM PCM, it's not a question of emissions*, it's a question of not blowing your engine up with a bad or under developped tune. Auto tune won't cut it in my experience. Reach out to Darth Fiero here (Sinister Performance http://www.gmtuners.com). He'll sell you a good tune with the PCM for less money than you would spend on custom sensors, non standard ignition parts and all the hassle to have to redo every thing from the ground up in terms of fuel maps, ignition tables, etc... Other YouTubers have tried going MicroSquirt, LS coils and custom pickups on the 3800 only to have real problems with the ignition and finally melting a piston.
I've run MegaSquirt on old 6.6L V8s with carb to EFI conversions; it works OKish. But for a 3800 turbo application, with the particularities of the 3800, I studied the options and I decided that those who came before me (Dark Horizon, JustinBart, etc...) knew which was the better solution. They had already blown enough engines and tried a ton of different mods to show that in the end, the factory PCM is still the best.
*You get the EGR deleted and you go for a huge 3 inch Corvette MAF in the tune with Darth Fiero. So not at all emission compliant.
Yeah, I expected pushback. While I respect there's a beaten path, we're going to maintain the microsquirt. As to the complexities, it's really not, I'm guessing I've misrepresented that somewhat with my questions. The factory sensors all work, Megasquirt as a collective is designed around using GM sensors. The ICM stays in the car and is simply triggered by the microsquirt instead of the GM PCM. With regards to boost, it's a way down the road pipe dream that truthfully isn't really a smart idea for this car. Intercooling will be as much of a pain as the engine cooling system is and high IAT's and endurance racing don't exactly go together. Ignoring the additional fuel consumption in a car that already has a small fuel system and added complexity in the powertrain which is kind of the opposite direction of where we need to go. It's why we're running a pushrod 3800, it doesn't get much more simple. I've already argued for staying naturally aspirated and I suspect we'll have our hands full just keeping the car out on the track. Additionally, this car actually has a competitive history, with the microsquirt in it, I seriously doubt we're going to encounter any roadblocks that are squarely the fault of the ECU. If we do, I'll post about it so everyone can say I told you so.
quote
Originally posted by pmbrunelle:
How do you meet the cost restrictions of Lemons with engine, ECU, and transmission swaps?
None of these cars meet the cost restrictions, it's just a game of who's the best at lying. It's why they have multiple classes and bump you up if you actually win. Or penalty laps if you're being blatant in your lies. We're truthfully not expecting to win, hopefully just have fun and maybe, if we're lucky, be reliable and competitive. We will fab a majority of the components other people pay for that make these swaps expensive (mount, brackets, etc.). Additionally, we paid $40 for an engine with a harness. So, deals, however unlikely, do exist. Lastly, the car was purchased with the ECU and, as such, is already included in the equation. We'll sell some items off the car to get us where we need to be and the judges will make their decision.
If you have any wiring diagrams/documentation/configurations surrounding how you tied the 3800 to a Microsquirt, I'd love to peruse them. Do the stock crank and cam sensors work without any mods? I haven't looked to see if they (you?) did any mods to the microsquirt in the car to make it work with the TDC. Do you pull them directly from the sensors or do you pull them from signals output from the ICM? If from the ICM, how does the sensor vref and sensor ground play into that? I'm full of questions... The only actual documentation I can find about C3I is from 2005 and it was referencing different hardware than a V3 microsquirt, of course.
Shoot me a PM, I should still have the "wiring diagram" I wrote up for the 3800 buggy, if not I have my generic and I can help fill stuff out, luckily the ICM takes in the dual crank and cam signal, processes it and if I remember right you give sensor ground, 5v, and ignition 1 to the ICM and you are ready to roll Oh and then it has a "basic trigger" I think 6x maybe 3x to run to the Microsquirt to give RPM signal,
I can't quite remember on that car on the Microsquirt, if any modifications were made to it it would have been adding a pull up resistor inside the case to run IGN 3 for the 3rd pair of cylinders, but I think it used the factory ICM as well, which again processes the crank signal and outputs to the Microsquirt so no need for 3 ignition outputs.
Shoot me a PM, I should still have the "wiring diagram" I wrote up for the 3800 buggy, if not I have my generic and I can help fill stuff out, luckily the ICM takes in the dual crank and cam signal, processes it and if I remember right you give sensor ground, 5v, and ignition 1 to the ICM and you are ready to roll Oh and then it has a "basic trigger" I think 6x maybe 3x to run to the Microsquirt to give RPM signal,
I can't quite remember on that car on the Microsquirt, if any modifications were made to it it would have been adding a pull up resistor inside the case to run IGN 3 for the 3rd pair of cylinders, but I think it used the factory ICM as well, which again processes the crank signal and outputs to the Microsquirt so no need for 3 ignition outputs.
Chris
PM Sent.
I think on the TDC that it used an older version of DIS, before C3I, without the ICM. So it may well have required three ignition outputs and the according pullup on ALED or WLED for the 3rd ignition output. Regardless, it's very interesting to think the ICM allows you to trigger the entire thing with one ignition output. I do wonder if that has any implications when using spark cut for rev limiter or anything else.
EDIT: This post on msextra by "WopOnTour" pretty well breaks down each system. It seems like the prior DIS does process and pass out the signals to the ECU, albeit with different connectors and maybe a little less granularity? I'm guessing they differ and are presumably not inter-compatible because of the different crank wheels that were used.
[This message has been edited by 87FieroLemons (edited 04-23-2025).]
My experiences with a 2.8 may not then apply here.
