So Im having trouble procuring a big enough pulley for the blower... The best alternative I can think of isnt nearly as efficient, but it would be extremely simple and easily adjustable.
Basically, I would run a pipe with an adjustable valve from the manifold post supercharger to the adaptor Ill be making thats between the supercharger and throttle body.
Ill be able to open this valve just enough to keep the pressure where I want it, and instead of releasing the excess pressure to the atmosphere itll keep it in the system. That way its accounted for by the throttle body. My thought was that if the air thats already been accounted for get released into the atmosphere the air/fuel ratio will be all wrong. This way itll just get sucked in by the supecharger again, and the ratios will stay correct. This will be a serious loss of efficiency but who really cares at this point. Itll take 10hp to run the blower, and about 3 to move its extra weight along with that of the adapters. 6psi of boost should add at least 50-60hp so itll still be a huge performance increase.
There is already a pneumatically-actuated boost bypass valve on the supercharger. You can control it by applying PWM to the control solenoid. I don't think it's meant for controlling boost at WOT...
But just get the right pulley sizes already. If you can't figure out how to get appropriate pulleys, you're in over your head, and something else in this complicated plan will stop you instead.
The throttle body is not an air measuring device; feel free to bleed out any air that has gone through it.
What you don't want are leaks downstream of a mass airflow sensor (MAF). Will you be using a MAF? Probably the ideal would be to grab the 3800 ECM, trigger wheel and peripherals... the longevity is all in the controls. Obviously it will be easier to tune/adapt controls that worked with a supercharged engine from the factory.
Oh geez im an idiot. All the cars Ive ever had have had MAF sensors built into the throttle body.. I totally forgot the fiero has a map sensor instead. I guess Ill just have to plug the vacuum line for the map sensor in before the supercharger inlet. Probably in the same place as I was going to put that valve. Yeesh. I cant believe I actually thought that all through without realizing theres no maf sensor
[This message has been edited by Boot (edited 09-12-2016).]
Actually, you'd want a 2 BAR MAP sensor on the pressure side and change your PROM program setting to 2 BAR.
Okay. I see why Id want to do that. But just out of curiosity, why wont the regular map before the blower work? Wouldnt the manifold vacuum still reflect the amount of air going in?
If you leave the boost bypass valve shut all the time, then you could connect your existing 1 bar MAP sensor pre-supercharger, but post-TB. This would not be reading the plenum pressure, but you would be reading something repeatable that could be used as the basis of a tune.
However, if you are going to twiddle around with the boost bypass valve, then the plenum pressure will not be a strict function of the post-TB pressure. The plenum pressure will also depend on whether the boost bypass valve is open or closed.
In this case, you should use the 2 bar MAP sensor plumbed to the plenum.
If you leave the boost bypass valve shut all the time, then you could connect your existing 1 bar MAP sensor pre-supercharger, but post-TB. This would not be reading the plenum pressure, but you would be reading something repeatable that could be used as the basis of a tune.
However, if you are going to twiddle around with the boost bypass valve, then the plenum pressure will not be a strict function of the post-TB pressure. The plenum pressure will also depend on whether the boost bypass valve is open or closed.
In this case, you should use the 2 bar MAP sensor plumbed to the plenum.
But if any boost that was bypassed was put back into the chamber with the map, wouldnt that adjust the pressure to reflect whats actually going into the engine? The air would get sucked back into the SC instead of being released to the atmosphere. Im thinking say screw the built in bypass and build a manual one myself. Itll be an adjustable valve, not just an open/closed one. This valve will then be adjusted so that at WOT I max out at 7lbs of boost, and left at that setting. So the percentage of the boost pressure that escapes through the valve will be a constant as well.
[This message has been edited by Boot (edited 09-13-2016).]
I wouldn't trust anything but a positive displacement blower to be remotely consistent, but you decide for yourself...
I guess in the stock ECM, you'll get power enrichment above 0.8 bar absolute manifold pressure (or maybe it's TPS)???
If you want to duplicate this behaviour, how will you relate the pressure post-TB to the plenum pressure?
You should wipe all the tables (make a backup) of your stock ECM clean, and tune the engine from zero. The exercise of tuning the N/A engine will serve as forgiving training to teach you how to later tune the supercharged engine. Furthermore, this exercise will allow you to become familiar with what the Fiero ECM can and cannot do; which may drive decisions such as 1 bar or 2 bar MAP. You may even decide the Fiero ECM is not adequate.
[This message has been edited by pmbrunelle (edited 09-13-2016).]
Correction: you SHOULD decide the Fiero ECM is inadequate for this... because it is. The electronic controls will most likely be what makes or breaks this engine, literally. At the very least, I'd suggest a GM 7730 ECM with turbo code, and a 2-Bar MAP sensor. It would also be a good idea to get a wideband O2 sensor for data logging.
Yup, I finally just figured out how Im making the manifold adaptor the other day. Its rather difficult to explain, but Ive been recording my progress and Im going to upload a video on youtube when its done. Progress is just going to be slow, because after a rather unfortunate turn of events the Fiero is now my daily. So before I actually take it apart I need to come up with another daily for obvious reasons.
Quick update... I'm still dailying the Fiero, but since I bought the extra manifold I can keep working some anyways!
So I was having a hard time figuring out how I was going to make spacers that would let me use the original bolt holes on the manifold. It looked like it was just going to be a b*tch and there was nothing I could do about it, until I had a small stroke of genius. Why not drill out the holes on the manifold, and use studs with nuts on the bottom instead? That way I could just use this 2x3ish square tube I had around and just weld bolts to the inside for the studs.
As you can see I had to do some ghetto machining on the drill press with a special drillbit I made, and some clearancing with the death wheel in order to get the nuts to sit flat against the manifold because it wasnt meant to have nuts on that side. Its sort of ugly but it works.
I just took these screencaps from the last video I made. Its all going to get put together into a short film on youtube that goes through the thinking I did to make this thing work... For under $200 Ghettocharging at its best!
Next up is making the plate to bolt the supercharger to, and the stuff to mate it all together.
------------------ I have no idea what Im doing, but Im doing it.
My turbo 3.2 sounded the best. Like I mentioned, I never could get a good idle out of it, so at lights I would always be blipping the throttle. I was sitting at a light once, doing such, and I found myself next to one of those magnum Hemi things. I did not want to race, but pulled out quickly. He never gave pursuit. I would get all kinds of crazy looks and I guess it was pretty intimidating. But, that happened a lot.
The thing is with most cars, if you have a little knowledge, you know what's under that hood. With a Fiero, or a real hotrod, you never know. Especially when the engine is looping, huffing and puffing.
The Fiero ECM can be programmed to work with boost. You will need to plug in a GM 2 BAR MAP sensor and reprogram the MAP vs RPM vs Timing table in the ECM chip. The timing table is split by a factor of two to have RPM and Timing for conditions of both boost and vacuum. Tunercat makes a program designed for such an application and has definition codes for the 85 and the 86-88 ECM's .Programmers like Sinister Performance can most likely help you with a chip to work with the 2 BAR MAP. Note that you cannot just plug in the 2 BAR MAP and expect it to work.
------------------ " THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, Autolite 104's, MSD wires, 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 "
This is mythical and somewhat reminiscent of that old cartoon I watched as a kid -- Speed Racer. They built an engine so powerful that it could propel a car so fast it would make people delirious. They would go insane. Even so everyone wanted it and they were trying to steal the engine. So to keep it from falling into the wrong hands "Pops" destroyed it. But, at the same time he secretly etched the plans for the engine onto the windshield of the Mach 5. That still did not stop them. When someone tried to steal the plans, "Pops" shattered the windshield with a wrench. The secret was lost, but it left you thinking should something so powerful ever be built?
I think this should be discussed before we progress any further.
This is mythical and somewhat reminiscent of that old cartoon I watched as a kid -- Speed Racer. They built an engine so powerful that it could propel a car so fast it would make people delirious. They would go insane. Even so everyone wanted it and they were trying to steal the engine. So to keep it from falling into the wrong hands "Pops" destroyed it. But, at the same time he secretly etched the plans for the engine onto the windshield of the Mach 5. That still did not stop them. When someone tried to steal the plans, "Pops" shattered the windshield with a wrench. The secret was lost, but it left you thinking should something so powerful ever be built?
I think this should be discussed before we progress any further.
Based on this, we should definitely progress! That way the Fiero will get all the respect it deserves!!!
Figured I should add some closure to this thread...
I met a guy at a car show who did nearly the exact same thing I was doing here... Just to a rwd 2.8 in a rat rod. Same blower and everything. He said he revved it once and blew both headgaskets, replaced them with better ones, and then it snapped off the crank within 100 miles.
So that was a little disappointing to hear. And since the Fiero is still my daily, I stopped working on it
Just last weekend, I traded the supercharger to a buddy of mine for an old Garret gt1752 turbo off of some sort of volvo, with a top mount intercooled turbo build in mind. Had the worst shaft play either of us had ever seen. More than an eigth of an inch. Whatever, I thought, rebuild kits are only $60. Took it home and pulled the compressor housing off to find out the the shaft is actually broken in half. So thatll be $120 for a new core section. But in the end Ill have a working turbo, and when I get a new daily (looking at an '02 BMW 540i with a 4.4 dohc v8 and a 6 speed manual ) Ill get cracking on the fiero. If/when the 2.8 kerplodes, itll probably get a 3400 turbo.
Thanks to everyone who contributed to this thread!!! It was a lot of fun figuring out all the little challenges. With an m62 I could see it working much better. Maybe some other time...
------------------ I have no idea what Im doing, but Im doing it.
Finally some sanity. This thread was painfl to watch, but people will do what they want despite advice to the contrary.
It is a waste of time playing with the 2.8 when a stronger stroked crank is available from the 3.1/3.4 (same crank) and using stock pistons ensures failure - you need some forged slugs that will take the boost.
Turbo is a nice way to go on these (I ran one as my primary street car for more thn 20 years, boosted to 10-12 psi) but you can't just grab the first used turbo you find, you need to spend a lot of time with turbo charts figuring out which one is optimal (hint - it won't be as big a turbo as you think).
At least you got a learning experience without spending a ton of money.
im an idiot. All the cars Ive ever had have had MAF sensors built into the throttle body.. I totally forgot the fiero has a map sensor instead. I guess Ill just have to plug the vacuum line for the map sensor in before the supercharger inlet. Probably in the same place as I was going to put that valve. Yeesh. I cant believe I actually thought that all through without realizing theres no maf sensor 
Ghettocharging at its best!
So thatll be $120 for a new core section. But in the end Ill have a working turbo, and when I get a new daily (looking at an '02 BMW 540i with a 4.4 dohc v8 and a 6 speed manual 
