For reference, I run up to 45 degrees of timing at cruise on just about any 3800 out there.
The aluminum head motors are fast burn and run around 15 deg less peak timing than the iron head motors. There is a point where significantly advanced ignition is counter productive even if no detonation exists at that point and since Code59 has a cell follower I can watch it while replaying a datalog and note where off throttle detonation occurs. As long as my exhaust temps continue to hoover around 6-700 deg during normal driving I should be in good shape and once tuning is on track I can start advancing timing to what's seen in the turbo grand prix code.
[This message has been edited by Joseph Upson (edited 12-03-2010).]
I'm still chipping at it but the process has been the same as usual, a little progress then out of time. The latest efforts were productive and the timing changes eliminated the off throttle detonation I was getting and as before there was no detonation at wide open throttle eventhough I bumped the timing up a little at that point. I did have a startling moment when after coming to a stop the engine started knocking and rattling at idle.
I shut it down and then experienced a hard start. It turns out the vacuum hose from the 3 bar MAP sensor to the fuel pressure regulator came loose sending a near 300 Kpa MAP signal to the ECM which referenced an area of the fuel and spark table that has seen no tuning at all, an Autotune calculation showed this. I'm going to continue to tune without boost until it runs well enough to apply full throttle without detonation as well as idle and decel smoothly.
I discovered that I errored in measuring oil pan volume and placed the oil return from the turbo a little too low. I'm currently running the oil level about a quart low to prevent it from backing up into the drain. I planned to relocate it but given how low the turbo sits decided it would be better to leave it as is. Once the oil cooler is added into the system the additional volume will nearly restore the missing quart without raising the level in the pan. I've just about burned off the residual oil in the turbine housing and if push comes to shove I can add a small reservoir below the turbo and scavenge pump the oil back into the pan but at this point it does not appear it will be necessary. Oil temps are running at 200 deg while driving so far.
I finally addressed the muffler dilemma as seen in the video below. Interestingly you can't tell much of a change in noise level between the round mufflers and the Cherry Bomb Turbo II mufflers in the video, but in person it is significantly different. The low level drone from the round mufflers is too intense from inside the car despite the seemingly tame sound in the video. The Cherry Bombs take a considerable bite out of the cabin noise level as well as what you hear from the back of the car. I paid $60 ea for the round mufflers, what a waste. The Cherry bombs were $20 ea from Autozone at 18"x7.75x3.75 with 2.25" end fittings. I hung them on the car for testing, they haven't been installed yet.
I'm also hoping I'll have it primered at a minimum during the next visit. It would look much better with some uniformity to go along with the 18x8 and 18x9 EVO IIs, it's also getting a 1" drop. The plan is to paint the car gloss black.
Current wheels
New wheels, they're not on the car.
[This message has been edited by Joseph Upson (edited 01-04-2011).]
did you get this to run with boost i know that i talked to a water/ meth injection guy and they claimed that they had a car out there running 11 to 1 with boost and prem pump gas
Originally posted by engine man: did you get this to run with boost i know that i talked to a water/ meth injection guy and they claimed that they had a car out there running 11 to 1 with boost and prem pump gas
Yes, at least 11.5:1 and so far 4.5 psi on premium (91) without meth. It can do more but I'm still at the bottom of the tuning slope and can't go all out just yet.
Fortunately I have the car with me now and can take my time and work on it. As of yesterday I ditched code59 because it was too temperamental resulting in irregular performance and terrible in town gas mileage. The trip from FL to Atlanta yielded 20 mpg with the 6 speed for the first 160 miles running at about 13.2:1 AFR. Fortunately Darth's work on the digital cruise swap worked out for me and once I got my laptop unjammed I was able to adjust the steady state cells on the hwy to get the AFR up to 14.7:1 and that was good for an amazing 5 mpg gain to get me 25 mpg hwy for the rest of the trip. Saved a bit of cash there. The around town driving was horrible afterwards though due to the difficulty in getting the AFR to stay in the stoich range and Autotune which compliments code59 didn't help by taking me in the wrong direction when used. I expect fuel economy to get back up to the 29 mpg I got on the first test if not better before fiddling with the tune afterwards since 8F has a lean engine run mode.
Switching back to 8F Turbo Grand Prix code made a tremendous improvement and that's with the old rough tune which still accelerated the car smoothly, something I was not able to get 59 to do. Not saying it's a bad code at all, it just requires too much work I believe to be effective with the aluminum head motor given how much of it is still tuned for the iron head 4.3L. It was 8F code that provided the most impressive throttle response in the beginning and for all the time I spent with code59 it never produced any offline performance near what 8F did so I should have switched a long time ago.
The meth kit is installed preturbo at the moment, except for the activation electronics. The nozzle is positioned about .5" from the compressor wheel. There is a check valve in place but I'm not impressed with it's performance as an out of car test still produced droplets at pump shut off. I don't feel it will be a problem given how thick my compressor blades are and its close proximity to the compressor wheel which will reduce the size of the droplet that can form at pump shutoff on decel.
Compressor blade condition for reference before preturbo meth spray.
I have a fluid level sensor from a 93 Caprice to adapt to the tank.
I had room thank goodness to plumb 3" tubing all the way up to the stock airfilter canister. It turns out the previous filter I absentmindedly put on the end of the turbo after calculating the area by counting the number, length and width of the pleats amounted to about 15% of the area of the stock Fiero air filter. It was much smaller than what was previously pointed out to me.
My plumbing for the meth system is pretty short thanks to the convenient location.
My oil temps were running as high as 240 deg and since I have oil squirters for the pistons there's an additional benefit to keeping the oil temps at the minimum recommended. I took the fan off because it did nothing for the 200 deg idle temps when I tested it so there was no point in keeping it. I believe a copper/brass cooler would have done better as I've also found the aluminum 3 row radiator doesn't seem to perform any better than the brass two row radiator it replaced. My understanding and experience is that aluminum has a great weight benefit over the copper/brass piece but side by side with the same config does not cool as well and that's been my experience.
Next was my coolant temps, some of which is apparently inherit of the 3900 coolant flow design as joshua also expressed some concern with seemingly higher engine temps but then it comes with a 190 stat. In my case I removed the t-stat and still my engine temps would hold pretty steady at about 190 with the fan only able to pull temps down to about 188 at idle on an 85 deg day. Interestingly, when I installed the new front bumper I noticed the verticle partitions that helped direct air into the radiator were missing which would allow recirculation of hot air. I installed some make shift pieces out of sheet aluminum and noticed an immediate improvement in idle temps in that it didn't take as long to pull the coolant temps down and shut off the fan.
[This message has been edited by Joseph Upson (edited 03-30-2011).]
It's starting to look nicer to from the side anyway.
This was taken before the car was lowered.
Sure hated having to pull these back off to cut the bump stops. I also ran into a problem with the coil overs as the 12" springs put the spring perch right against the 18x9 tire/wheel combo. A 10" spring would have been perfect. The spring must rest against the upper plate without the cone seat that comes with the coleman racing kit. I'll probably have to add a spacer behind the wheel in order to drop the rear to the same height as the front though it is close. I have Eibachs on the front for a 1" drop and 275 lb springs and Kyb struts on the rear. The ride is nice only reminding me of the modification when going over sizeable bumps in the road.
Previous air temps at just over 7 psi were around 214 deg so the 40 deg lower temps are likely the result of the combined preturbo water/meth injection and a little better compressor efficiency than the twin T3s. I'm not sure an intercooler is worth the trouble at this point since even if it were able to reduce air temps by 50-60 degrees it may not be enough to offset what I'd loose as a result of the restriction to airflow. There's also the added traditional benefit of the second meth injection nozzle placed just before the throttlebody which hasn't been installed yet.
The engine is being tuned on 89 octane to insure 91-93 octane is an absolutely safe all out grade fuel at my boost level. I purchased my 35mm wastegates a few years ago without researching based on the typical T3 size wastegate port. Low boost = large port, high boost = small port. I have a 4.5 psi wastegate spring installed but as you can see that didn't stop boost pressure from hitting an unintended 8 psi, so the wastegate is too small. The engine pulls strong so far but there's still a good bit more tuning to go and I'm having a terrible time sorting out the hunting closed loop idle and off throttle stall. It's fine in openloop but that's not acceptable with todays gas prices and how much around town driving I do.
Top to bottom: RPM, Boost pressure, Coolant temp, Manifold air temp and at the very bottom knock retard. Manifold temp moves toward the bottom of the screen as it increases.
On second glance it appears that the monitor in TunerproRT 5 would be a good way to measure 0-60 times with the count at the bottom of the screen. Unfortunately when I switched back to 8F from code59 I had to change the Vss configuration. The problem now is that the odometer reads correctly as long as the ppm is set to ~4000 in the chip, but I'm not sure what the IP pulse divisor should be set to so the ECM does not post a speed in the log, although the Dakota Digital calbrator sends it a 4000 ppm signal. Setting the pulse divisor to 0 and 1 had no effect on the odometer reading but still did not correct the output in the data.
[This message has been edited by Joseph Upson (edited 04-06-2011).]
Setting the pulse divisor to 0 and 1 had no effect on the odometer reading.
Some of the pulse divisor settings for some code masks need to be made in steps; below is a list of valid IP divisor settings for some of the code masks I've worked with (in decimal):
0 32 64 96 128 160 192 224 256
Try some of these and see if you can find something that works.
-ryan
------------------ OVERKILL IS UNDERRATED Custom GM OBD1 & OBD2 Tuning | Engine Conversions & more | www.gmtuners.com
Some of the pulse divisor settings for some code masks need to be made in steps; below is a list of valid IP divisor settings for some of the code masks I've worked with (in decimal):
0 32 64 96 128 160 192 224 256
Try some of these and see if you can find something that works.
-ryan
Thanks Darth, I know 192 doesn't work since that's what it was set to initially.
The odometer and speed that registers in the datalog is now accurate for those who may find themselves in this situation. The ppm value only addressess the speed that registers in the ecm, the IP divisor affects the odometer after the pulse signal received from the VSS and for this application must be set to 0 or 1 or else the odometer will not work even with the conversion circuit in place.
The ppm had to be set to about 120000 for the correct speed to register in the ecm as well as show in the datalog with the Dakota Digital converter in place and this in my opinion is more important than an accurate odometer reading because the engine behaves differently with the proper speed registering at the ecm and without it you may experience stalls between shifts or while coasting as the idle rpm is held higher during these periods when the ecm can sense the car is moving.
I had to remove the turbo due to repeated bouts of oil smoke, Performance Techniques went through it and installed a gapless ring seal at the turbine end, rebalanced and warranteed it eventhough the warranty period had been exceeded. That was a blessing as the naturally aspirated condition revealed how far off the tune was and that it was being masked by boost. There was tremendous power off the line but after that it would fall over. That situation is nearly corrected and is a matter of proper fueling and spark timing which I found to be too far advanced despite fairly low spark retard.
Reducing the timing more produced better performance without a noticeable increase in exhaust temps characteristic of an engine with excessively retarded timing. I have since switched to 5W20 full synthetic and will install an oil scavenge system to address the previous oil drainback arrangement which wasn't ideal and was probably compromised when the car was on an incline.
I heard a lot about Shurflo pumps being used successfully as oil scavenge pumps but recently came across a few threads referencing the Holley red or blue pumps which have an all metal pump mechanism instead of a diaphragm so I'm going to give it a try. I ordered the Black pump which has higher flow and is methanol resistant. My oil cooler so far keeps oil temps at 200 deg or lower depending on the weather or traffic and I believe it's reasonable to suspect the heat stress will be offset by the near 0 pressure the pump will be operating under. I didn't like the price and poor availability of dedicated oil scavenge pumps and designed this system so that in the event of a pump failure the oil would build up in the tank to the bypass level and feed to the pan through the previous less efficient location and be okay when driven conservatively until the problem could be addressed.
The car should perform even better now than it did during the previous 8 psi with a better tune below 100 kPa and no oil in the exhaust. I hope to have the turbo and 1 step lower heat range spark plugs installed by tomorrow.
[This message has been edited by Joseph Upson (edited 05-17-2011).]
One more thing, no matter what compression ratio you're running, a hot engine within reasonable design limits is a good thing. I overlooked the fact that in the quest for keeping this engine on the cool side by removing the thermostat that I would sacrifice maximum fuel efficiency capability since the best economy is at the higher temps around 200 deg due to thermodynamic efficiency and that it would be more temperamental and difficult to tune because coolant temperature would be 155 deg one moment and 190 the next and that involved a large swing in spark advance as the coolant vs spark advance table was at work adjusting timing accordingly. A 185 deg stat produced a steady 196 deg driving temp above about 45 mph.
Originally posted by Joseph Upson: Compression test results:
1. 220 2. 230 3. 220 4. 255 5. 240 6. 250
Some of you are aware that I damaged the engine before getting any appreciable stats. Before I broke it 8 psi produced brutal acceleration.
1. The first mistake, setting PE to about 13.2:1 for lean best torque ignoring the fact that I have a turbo. Either that or overly aggressive timing burnt a/some rings.
2. Forged pistons require more clearance. The thought never crossed my mind despite my knowledge of it. Can't imagine why not. GM built the motor on the tight side if the .006 ring gap is any indication so I'll be looking for scuffing signs disassembly.
3. At this time blow-by was getting a little excessive and pressure building up in the crank case caused the turbo to smoke, (I thought it was a turbo problem).
4. Drove the car without the turbo while it was being checked out and discovered the car was only a rocket off the line and about 100 yds from there without it and that was it, no top end without the turbo. I'm speculating on the cause being not enough cam for the compression ratio, 216/213 along with whatever damage was present by this time.
5. Put the turbo back on (has a gapless exhaust seal now). Smoked right away. I eventually figured out the blow-by problem was worse and pressure built in the crankcase immediately, blowing oil out of the turbo and into the exhaust. This was an intermittent problem suggesting some degree of ring instability.
6. I installed a Holley Black fuel pump after removing the fire screen as a direct oil scavenge pump isolating the turbo drain from crankcase pressure. Smoking stopped immediately.
7. Now I have an idea, I can use one of the extra turbo drains at the pan as an additional crank case pressure relief, I can even run it up to the air filter canister and let the engine inhale the gasses vented. Then a little voice says " What if oil covers the hole and is blown up to the filter", and I say it'll bubble through before it gets that high. Wrong, the next day after the turbo was installed and the car seems to be running pretty good, I pulled off from a light hard and threw the oil to the back of the pan and I'd say about half a quart was blown right up to the air filter and sucked in the engine. There was an immediate and brief buck from the engine followed by a strong smell of burning oil (it was 5 a.m. so I couldn't see it) for about 2 minutes. On inspection the air filter was saturated and I could no longer go full-throttle from a stop without detonation. The datalog showed the problem occuring consistently within a specific rpm range and continuing off throttle for a few seconds in the lower cells also (using tunerpro5) indicating oil contamination and the side effects. Gradual acceleration would allow me to go into boost but 5 psi felt like 1 psi and now the car has no top end with the turbo either. I couldn't out run a Ford Ranger without difficulty at speed. I don't know how the car managed 33 mpg on the trip home.
The engine is out of the car now and will be disassembled tomorrow. I did a compression test and here's what I found:
If enough oil was gulped in, it's possible to bend a rod. That will drop compression too. Easy to check. When the heads are off, turn engine by hand and make sure the pistons all come up to the same height. If a rods bent, that piston will not come up as high.
Originally posted by 1fatcat: If enough oil was gulped in, it's possible to bend a rod. That will drop compression too. Easy to check. When the heads are off, turn engine by hand and make sure the pistons all come up to the same height. If a rods bent, that piston will not come up as high.
I'd be very surprised to find one of my H-beam rods bent. Even if that was the case it wouldn't explain the detonation which I'm sure is from oil contamination. I'd expect a ring land to have broken first. There is also a mix of very clean intake ports in the heads and some pretty dirty ports characteristic of oil residue build up from excessive regurge. Water/meth injected engines usually have pretty clean chambers and I have one or two that look like they were just polished. Cylinder 5 also pumped up a little slow.
[This message has been edited by Joseph Upson (edited 08-02-2011).]
Your cam/cam timing is not a good match for your static compression ratio.
I mentioned that, however it was only evident without the turbo and didn't cause a problem. I'm guessing at what kind of internal damage the oil ingestion caused and whether or not the forged pistons expanded enough to scuff the bore. I believe I'll find a broken ring land at this point.
Originally posted by 1fatcat: Ah, yes. See what happens when I don't read. LOL. Sorry, I thought they were stock rods.
You can look at the pictures to. I should have it apart today to get to the bottom of the problem. It won't be going back in the car for a long time though.
Following your thread with great interest. Not having the benefit of your knowledge, I went with a car tuning kit for my ls4 turbo and it's been a lot of fun even without its final tune from Kevin. I deviated from Kevins kit by going to an air to water instead of his air to air intercooler. For what it's worth, Kevins kit injects the meth at the intake rather than the turbo.
[This message has been edited by dratts (edited 08-03-2011).]
Considered it but at such low speed I'd expect a ring land or head gasket to give especially with the oil contamination which low compression shouldn't cause. We'll see shortly.
I've only removed the weak pressure piston so far and no broken ring, ring land or bent connecting rod. It appears at this point to have been burnt rings, possible couple of burnt valves and severe carbon build up on the pistons that's partly responsible for the problem I experienced. There could still be some undiscovered problem.
[This message has been edited by Joseph Upson (edited 08-04-2011).]
Bearings for piston 5, it looks like overly aggressive timing stress from under camming for the compression ratio.
Unusually clean port, this is what they all should look like, two others are pretty close. The rest show oil residue suggestive of oil in the cylinder.
The future rebuild will have the pin ends of the rods rebushed to use the stock pistons to drop the compression down into the 10 range as well as have the benefit of the low tension rings and proper valve reliefs to allow some VVT use as planned for the backup motor.
Follow up years later 6/2020 from rereading this. The reground cam was fine, I just installed it fully advanced instead of at the straight up position, which magnified low end torque even further in addition to the high compression ratio, in the fashion that VVT is designed to do. The bearings were damaged, because my understanding of oil film strength was still in its infancy, which allowed me to risk using 5w20 motor oil with very tight bearing clearances, which was marginally okay, until the motor experienced a severe overheat with temps reaching near 280 F. I babied the car a little more than a quarter mile home, ending with temps near that range and that's what helped create this bearing damage, as with 5w20 a fairly low viscosity, there was little to no oil film protection left. The oil light flickered on for the first time at idle the very next day. So no doubt my experiment with low viscosity oil and unfortunate overheat lead to this result.
[This message has been edited by Joseph Upson (edited 06-06-2020).]
I found the three metal pieces in the oil pan. They are sitting next to an intact oil squirter as a reference to what they were attached to and what they looked like at one time. Apparently they made contact with the pistons which pushed them into contact with the counter weights. I'm not sure why. They were aimed at the bottom of the piston. I must have missed the clearance being very close while the motor was on the stand or something happened under load that caused this. From what I can tell from the pieces, all three are the shorter nozzle.
This may explain my intermittent low oil light that I shrugged off as a sensor problem as this didn't happen right away because I removed the oil pan to add an additional drain fitting and they were not present. Although the nozzle are pressure activated the missing tips permit more flow and that might have dropped the pressure by 5-6 psi. The engine only runs about 45psi steady. All of the pistons have been removed and as far as I can tell the burnt rings combined with the oil ingestion permitted excessive carbon build up that lead to preignition.
or to a lesser extent burned rings. IMO, a boosted engine with 11.5 C/R is going to be hard to keep out of detonation but Joe seems to disagree. Maybe he will get it right but my experience shows that much over 9:1 C/R with a turbo isn't an easy workable combo. Applying a turbo to any engine can boost the effective C/R several points. In this case the engine may have an effective C/R of 14-15:1. IMO, that' presents a very a difficult engine management situation to work with. Hope that Joe proves me wrong.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, 3.4" Pulley, N* TB, LS1 MAF, Flotech Exhaust Autolite 104's Custom CAI 4T65eHD w. custom axles, HP Tuners VCM Suite. "THE COLUSSUS" 87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H " ON THE LOOSE WITHOUT THE JUICE "
Originally posted by Dennis LaGrua: or to a lesser extent burned rings. IMO, a boosted engine with 11.5 C/R is going to be hard to keep out of detonation but Joe seems to disagree. Maybe he will get it right but my experience shows that much over 9:1 C/R with a turbo isn't an easy workable combo. Applying a turbo to any engine can boost the effective C/R several points. In this case the engine may have an effective C/R of 14-15:1. IMO, that' presents a very a difficult engine management situation to work with. Hope that Joe proves me wrong.
Burned rings it is but not because of the compression ratio. As I mentioned earlier, it was the result of a misunderstanding that resulted in my setting boost range AFR to 13.2:1 instead of ~11.5:1.
Compression ratio limits are very much a part of cylinder head design and as I've already proven in the initial 3900 thread, the engine is detonation resistant with its stock 9.8:1 compression ratio, no intercooler and 212 degree intake temps on 89 octane and stock Turbo Grand Prix spark table. Also note that despite the compression ratio the engine is rated for 87 octane fuel from the factory.
My mistake here Dennis in addition to the wrong AFR setting is that I did not change to a more appropriate camshaft for the compression ratio, look at the initial compression test numbers, they're sky high. I just had no idea how severely under cammed the engine was for such a high compression and just lost site of the fact that all else the same, as the displacement increases, the more the existing cam moves toward a being a bottom end camshaft. Here I increased displacement and compression ratio at the same time, double trouble. I just didn't cover all of the basis but now everyone else coming up behind me will if they read this.
Had it not been for those two mistakes I'm confident from what it did on 8 psi from the driver seat it would have put down some serious power numbers.
[This message has been edited by Joseph Upson (edited 08-04-2011).]
Originally posted by Will: Pre-ignition would mean holes in your pistons.
At some point I imagine so, but my choice of preignition references the fact that on a moderately hard acceleration from a stop the engine would buck before an appreciable load was reached and I would immediately let off the throttle. When I observed what I knew was detonation the car didn't buck but experienced a reduction in power during acceleration and I could see the the timing being pulled on the computer screen during the datalog. There was a lot of flaky carbon deposits as well as the appearance of burnt valves or at least a couple that got very hot as can be seen in the picture. None the less, the pistons are fine.
Originally posted by Will: Did you ever calculate your dynamic compression?
Yes, ~10.5, static ~ 11.6 but it didn't matter because I still hadn't considered the camshaft duration. Instead I was theorizing based on the stock engine's performance. The engine was very practical and tame during the time it was driven off boost but as I explained things didn't go wrong until I added boost with the wrong PE AFR. Right after the 8 psi runs my valve cover breather was saturated with oil signaling that I was suddenly getting lots of crank case pressure. Timing retard under boost was very conservative though at less than 2 deg. I believe timing was too high overall in that area though.
[This message has been edited by Joseph Upson (edited 08-04-2011).]
Even builders who are going for all motor power don't go that high on the dynamic compression... Whether the cam was otherwise correct for the application or not--in terms of where in the RPM range it put the engine's powerband--was irrelevant. Just because you blew it up immediately doesn't mean it would have lasted 100K miles if you hadn't.
So are you going to learn from this and try again?
I've learned my share building engines, and I'm sure I'll learn more. One of my favorites was having a custom set of pistons cut, then having another custom set of pistons cut because I realized I hadn't spec'd the right compression on the first set. Now I have a $1000 set of 8 ceramic and moly coated paperweights.
[This message has been edited by Will (edited 08-04-2011).]
Originally posted by Will: Whether the cam was otherwise correct for the application or not--in terms of where in the RPM range it put the engine's powerband--was irrelevant. Just because you blew it up immediately doesn't mean it would have lasted 100K miles if you hadn't.
So are you going to learn from this and try again?
My reference to the cam was more for the dynamic compression, more duration would have lowered it as well as produced a proper powerband without the turbo as that was the only time the short powerband was noticed. In regards to whether or not the engine would have lasted 100 K had I not made the mistakes I did there's absolutely no way of knowing that for sure but with my driving habits and the parts used I would have expected it to.
Yes I have learned from this and will try it again.
A cylinder hone (if that's all it needs) and a set of new rings and bearings and I'll be back in business but with different pistons to drop the compression by about 1 point since I'm not going with another cam and don't want to be locked into 93 octane anymore.
[This message has been edited by Joseph Upson (edited 08-05-2011).]
Well i hope you can do it but don't think it will work when starting with 10.5 or 11.5 to one and 7 psi your effective compression is going to be really high some where around 16 to 1 article on effective compression http://www.kb-silvolite.com...?action=read&N_id=30 I am sure that you can find the mathematical formula to find exactly what your effective compression ratio that may help you in knowing how much water / meth injection is needed and what mixture of water and methanol
Well i hope you can do it but don't think it will work when starting with 10.5 or 11.5 to one and 7 psi your effective compression is going to be really high some where around 16 to 1 article on effective compression http://www.kb-silvolite.com...?action=read&N_id=30 I am sure that you can find the mathematical formula to find exactly what your effective compression ratio that may help you in knowing how much water / meth injection is needed and what mixture of water and methanol
Thanks for the link and those are the calcs I used. The engine worked fine and ran hard. I just leaned it out in error in the code and burned the rings. I know I keep saying it but it seems to keep getting missed. I wasn't paying close enough attention and I set the air fuel ratio to 13.2:1 and ran it good and hard. The rest is history. There is a log further up showing the run. There was no problem with detonation before the rings were damaged. Remember, this engine is rated for 87 octane with 9.8:1 static compression although I'm sure GM used the VVT to help make the possible as retarding the cam beyond a certain point puts a real dent in dynamic/effective compression.
OK now i think i understand what you are doing is trying to be as efficient as you can be at making 400 HP with the best driveability and not trying to make the most HP that the engine can make that being said i think it will work if that is what you are after . If you where after max HP i would say it isn't the way to go due to the compression makes it boost limited where the lower compression would allow much higher boost that over comes the HP loss in a lower compression ratio but the low compression max HP engine is going to be much softer in low speed torque I hope this is correct in what you are thinking
OK now i think i understand what you are doing is trying to be as efficient as you can be at making 400 HP with the best driveability and not trying to make the most HP that the engine can make that being said i think it will work if that is what you are after . If you where after max HP i would say it isn't the way to go due to the compression makes it boost limited where the lower compression would allow much higher boost that over comes the HP loss in a lower compression ratio but the low compression max HP engine is going to be much softer in low speed torque I hope this is correct in what you are thinking
That is correct, low boost efficiency, trying to get a lot for a little. Now with the stock motor a couple of hours from being installed I'll be able to run more boost than intended, as well as post some facts regarding intercooler efficiency just in front of the cradle. Without an intercooler my intake air temps ran about 50 degrees above ambient at 70 mph. Around town it gets a little higher.
It sure is hot here in Tampa, whether the son is shinning or not and it doesn't cool off much at night. It also rained nearly everyday for the past week. Otherwise this engine change would have been done by now.
