supercharger for 3.4 DOHC

[bszopi]

If you custom made a lower manifold that would allow you to mount the blower to it...

[brian89gp]

Tuning would be an issue, do you guys think it is better/easier to go to OBD I or II, not the 1.5 that I have.

Your so called 1.5 is OBD I true and true, somebody coined up that 1.5 term a long time ago and it seems to have stuck. The majority of the 94-95 DOHC chip is based off of the the last years of the OBD I 3800 ECM.

Your PCM that you have now is the best bet. You should be able to run a small amount of boost (6-8ish) without much trouble, and I don't know if Ben has gotten around to it but its not hard to modify.

[Fierobsessed]

I was just browsing through some old threads and found this one, It strongly relates to my project that has been going on... like forever.

Quotes and responces...

"I have not heard of any supercharged 3.4's"

There was one known to exist, Matt Hawkins origionally pioneered the Roots charged 3.4 DOHC ( Eaton M62). For some reason or another, he scrapped it and went with a turbo. The engine wound up in a Fiero, and ran a 13.2. He has had problems with breaking axles. But the car is fast. That was the only one I knew of. He had a website with a picture of the engine, but has since gone 404.

"Just drop an Eaton SC right on top of the lower intake. Less pipe. I'm sure all that extra pipe will cause some lag while the airspace inside the tubing compresses.
However such an indevor would require fabrication of a manifold."

That is what my project is all about. The custom manifold. I am pretty dam good at fabrication. I have a Lathe, a Mill, a MIG and a TIG welder, That and some raw plate aluminum, this project is underway.
Heres the basic manifold I have started working on. This will have a piece of 1/2" plate aluminum ontop of it for the blower mounting surface.


"And a hole in the hood, or a large cowl."

You're telling me!!!
This was a mockup with an M90 in my old car back when it had a 3.4 DOHC. Note* I will still be able to see out my rearview mirror.


"eaton gives you full boost very quickly, and is tried and true. Plus, very affordable."

It's all about driveability. Torque makes a car driveable, responsive, and feel fast. I figure with its wide open ports, and a couple PSI down low, this engine should make a whole lot of torque. The M90 cost me 175$ a few years ago. I recently bought an M112 to replace it. That cost about $500. Ive been getting more serious about how much power I expect to make. This is the new blower mounted ontop of the crate motor.



"I don't see why a roots style blower can't be intercooled...."

I don't either. But it's certainly not as easy as it would be with a turbo or a centrifugal SC. In particular, water/alcohol injection is looking like a really good alternative. I suppose I could sandwitch a small Liquid to air Intercooler somewhere in the intake manifold. But I really don't have the room, and I don't want to make the thing any taller then it already is I am thinking more along the lines of a Ventauri style water injection system. I have never seen one before, but It's my plan to make one.

"funny I was just measuring this the other night, and with the upper intake off you have about 10 inches wide 3 inches below the tops of the heads. assuming the m90 is 6 inches tall, the max height cowl I'd have to make in my J body would be about 2 inches. the thing is their would be virtually no volume between the supercharger and the combustion chamber. this would mean more psi but less effectiveness in the upper rpm."

Aggreed, there is 10" from one valve valve cover to the other, and 3" down to the lower intake. The Eaton M90 AND the M112 both have a 10.25" wide stance on there mounting flanges, and are both about 6" tall. But put it all togather, and it still dont fit.

I don't see the reasoning that higher RPM's might suffer, I have short short runners, and boost waiting right at the valves.

"Tuning would be an issue, do you guys think it is better/easier to go to OBD I or II, not the 1.5 that I have."

Tuning is an issue for sure. But I think that the Turbo Grand Prix code will be my best bet. Its OBDI. Whats nice about the 1227727 (TGP computer) and the 16194396 (91-93 DOHC) computer's? They are practically interchangeable. The ONLY differences are that the '396 will control a 4T60-E, and only the 3 solenoid style EGR, while the '727 will not control any Electronic transmission, and will operate either the 3 solenoind EGR OR an "EVRV" style EGR. The pinouts on the EGR and Trans are also different. The rest of the pinout on the computer's are identicle. Also, the Turbo Grand Prix code is for automatic's only. It would have to be modified for a manual transmission. THEN tuned to the 3.4 DOHC with boost. It should be fun.

I will be running custom forged pistons, modified SBC 4340 Steel H beam rods, 3100 mains, and perhaps oil pan too. All of witch I hope will make this engine durable enough to sustain well over 350 horses without fatigue, or failure. Overall, my goals are LOTS of power, acceptable to good economy, a hotrodder look and perfect driveability. The transmission is a custom ratio Getrag 282 with a late model differential. The clutch is yet to be determined, but this setup will be migrating its way into my 88 Fiero GT.

[Wolf]

Fierobsessed, those are some nice pics, I was planing on putting a m90 and intercooler from a ford thunderbird supercoupe on my 3.4, IF Ihave the room(IE if It'll fit infron of the cowl,then use a cowl hood) sence the tb sc m90 dosn't have the lower mounting flange, i'll tuck down further between the heads

intercooled from the factory, a positive displacement blower outa fatten the power curve nicly

[Fierobsessed]

Don't forget the injectors and the fuel rail, you know where they stand on the lower intake manifold. As the picture I showed with the blower sittng in the valley, the fuel rails would be holding the blower up... I don't know if its ok to spray fuel in through the blower inlet on a EATON blower. They have teflon coated rotors (not sure if the thunderbird blower even had that feature yet) But If it can be done that way, then feel free to stick that blower as low as you can dare to plumb it in.

[brian89gp]

If you are good at machining you can probably get the newer/shorter style injectors and place them underneith the lower intake with the fuel spraying up into the port.

[Wolf]

There was one known to exist, Matt Hawkins origionally pioneered the Roots charged 3.4 DOHC ( Eaton M62). For some reason or another, he scrapped it and went with a turbo. The engine wound up in a Fiero, and ran a 13.2. He has had problems with breaking axles. But the car is fast. That was the only one I knew of. He had a website with a picture of the engine, but has since gone 404.
[/qoute]
if you still have the link,post it, and I can run it thru an internet arcive to try and get the pic

Don't forget the injectors and the fuel rail, you know where they stand on the lower intake manifold. As the picture I showed with the blower sittng in the valley, the fuel rails would be holding the blower up... I don't know if its ok to spray fuel in through the blower inlet on a EATON blower. They have teflon coated rotors (not sure if the thunderbird blower even had that feature yet) But If it can be done that way, then feel free to stick that blower as low as you can dare to plumb it in.

I was gonna put the blower right on top the fuel rail,and run a square intake tube under it (all the plumbing is external on the tb sc m90)
but it all just a theory on my part, I don't have the blower yet, and my main priority is getting the motor in the car.

btw, what size injectors are you gonna run? I was thining of 36 lbs from a l67, but they my not be big enugh?

[Fierobsessed]

I am still unsure of what size injectors I should be running. The smallest ones I can find that will support 450 hp out of a V6 would be the obvious choice. I don't know what that works out to be. But It scares me to think about Idling with the HUGE injectors I will need. My best guess indicates 36's will support my requirements, but if it makes more then the 400 max target HP, then It will be maxing out the 36's. I will be doing my break in without boost, and will be running it with the stock 23's (24's?). Ffter the break in period, I will re-enable the bypass valve, then assess where my PWM on the injectors gets me based on PSI of Boost at 100% PWM Vs. Target boost, figured by proportion. It's going to be a BITCH to tune this motor, Its so radically different then the program I will be running, but its the closest program I can find without venturing into the land of OBDII. (yuck!) I only have to get it right once though.

BTW, Matts old web page was http://mae.wvu.edu/~mhawkins/super34.htm
The story of his car AFTER the scrapping the SC resides here:

http://www.fiero.nl/forum/Archives/Archive-000001/HTML/20030531-2-027692-2.html

And if you look at the date, you can see how long I have been thinking about SC'ng the 3.4 DOHC... Now that I finally had all the tools and enough funds and info to do it. Then I went and moved to Las Vegas for an awesome job, and my priorities are all re-arranged. So my engine sits 2700 miles away. And I won't get to see it for another 7 months... EVENTUALLY this will get done. I keep telling myself.

[Wolf]

http://web.archive.org/web/20010808200048/http://mae.wvu.edu/~mhawkins/super34.htm

of cource the pic of the motor dosn't show :P

[brian89gp]

Running in batch fire mode 36's are too big, it idles but does so extremely rich. Mine was trying to pull .7msec pulse widths when most injectors won't cycle faster then 1.2msec or so.

[Fierobsessed]

Just curious, why is it that the PW's would be any shorter then they are for batch fire? If they fire the batch 1X each crank revolution, then I could see how the durations could be too short for the proper injector reaction, but if they fire 1X per 2 crank revolutions, then they would be firing exactly the same number of times as they would if they were SFI, but just in a different order. But as it is, I dont know if its 1 or 2 crank revolutions per batch fire, or if its 3 injectors firing on one rotation 3 on the other, These things are still unclear to me. Is there a way to get the computer to fire every other rotation if it does not already??? It might have to be something as ghetto as a pulse splitter. breaking up the pulses into 3 and 3 to get the PWM's up to an acceptable level. hmm... but that would only yield a maximum of 50% duty cycle... so that Idea is shot... more thinking....

I suppose I could use an fuel pressure riser FMU to try to squeeze more out of the smaller injectors. I however very much dislike using any sort of mechanical method to modify the amount of fuel being delivered, because its not as clear cut and measurable as just having it all in the computer, and there is just that much more of a chance of something going wrong. As long as the computer is programmed with the FMU taken into account, I could see the 24 lb/h's or somewhere about there having a good idle, and having the umph to get close to 400 horses. But its a sacrifice to do it that way in my opinion. And I will not consider using OBD 1.5, because its a bastard.

[brian89gp]

All 6 injectors fire at once, so each cylinder gets sprayed 6 times between intake valve events. There are 2 injector driver circuits but they are either connected together externally in the wiring harness or inside the ECM, most non-gm wiring diagrams usually leave that out and claim that there are 2 banks of 3. Other GM engines did use the dual bank firing arrangement, but the 60v6 got the shaft in the ECM/electronics department.

OBD 1.5 is a made up term that was coined 5 or so years ago. There was some overlap between OBD1 and OBDII; advanced features on a MEMCAL based ECM or OBD1 code on a flash based ECM, but its always one or the other. OBDII got the advanced emission controls and an encrypted datastream, OBD1 did not.

The 94-95 DOHC ECM, which has gotten a bad reputation for some reason, is the most powerfull (MAF, SFI, and some advanced features) yet easily modifiable ECM (MEMCAL based and a raw datastream) for the 60v6 out there. Amazingly enough it is based a great deal off of the 3800 OBD1 ECM. When you get down to the code the 3800 was programmed correctly when it came to powertrain management, the 60v6 ECM is a hodge-podge that shares a lot of stuff with ECM's from the late 80's and is a real nightmare to work with. With a little bit of work it would easily run a 3100/3400 in full SFI or even the 2.8/3.1/3.4 in batch fire mode.

[Fierobsessed]

You are saying that the Inj's fire at every reference pulse? Thats 600 Fires per second at 6,000 RPM's. That leaves 0.00166 s as the frequency of the pulse, and of that time, the injector must open, spray and close a metered amound of fuel. That's crazy. I might have to verify the pulse frequency in relation to the RPM frequency. Because I can't nelieve it would be that much.

[Wolf]

I thougt batch fire fired only one bank of injectors every crank rotation?(IE 135,then 246 next rotation)

[bszopi]

You'd think that would be how it works. But if you look at a wiring diagram, you'd see different. There are 2 banks showncoming out of the ECM, but then they tie into each other, then head to the injectors, where they seperate back out to the 6 injectors.