ASC/McLaren Grand Prix STE Turbo project

[TurboSedan]

in an attempt to compete with my brother's Spirit R/T i have decided that the stock GEN-II 3.1L LG5 Turbo engine is just not going to cut it it has a horrbily restrictive intake and heads - very long skinny runners. great for torque as my Cutlass has proven, but not so good for upper RPM power.

soooo...today my brother and i went and picked up a complete LA1 3400 V6. it's a GEN-III 60* V6 - the engine found in newer Grand Ams and Impalas etc. unlike my LG5, it has a much higher flowing intake and heads plus a larger intake valve with higher ratio roller rockers & roller lifters. at first i thought i'd just use the 3400 heads and intake on my LG5 and make a GEN-II/GEN-III hybrid but i think i'm going to take advantage of the increased displacement and use the whole thing. this block also has a better oiling system.

the old:
http://www.turbosedan.com/ste/DSC02569.JPG

and the new:
http://www.turbosedan.com/ste/3400/DSC02565.JPG

i made 227whp with the 240,000 mile GEN-II LG5 in my daily driver Cutlass and besides having the old GEN-II intake/heads, it has an extremely small Garrett T25 and a sidemount intercooler similar to the Turbo Mopars. my goal is to reach 350whp with the 3400 using a 3500 plenum, Garrett GT3076R-WG turbo, FMIC and 3" exhaust. i will be using the TGP wiring harness and ECM so the 3400 will no longer be SFI. EEPROM tuning will be with TunerPro RT using Innovate Motorsports LC1 WB. i will also be swapping out the 4T60-HD automatic for the extra Getrag 282 5-speed i have.

all of this going into my 3400lb Grand Prix STE.

http://www.turbosedan.com/ste/DSC02567.JPG
http://www.turbosedan.com/ste/DSC02568.JPG

it's sitting a little high in the rear since i just installed 1.8" drop Intrax front springs. i will be removing the stock transverse fiberglass monoleaf spring and installing adjustable coilovers like i did with my Cutlass. and yes, it really needs paint
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Joshua Mitchell
'90 ASC/McLaren Grand Prix STE Turbo - 1 of 1000
'91 Cutlass Supreme sedan - 3.1 Intercooled Turbo/HM-282 5-speed - 227whp/325wtq

[WVRampage]

That looks like it will be a fun car to drive,show us more pics a buddy of mine is wanting to do a 3100 turbo in his beretta.

[TurboSedan]

i haven't done much work at all with the drivetrain yet. i've done alot to the suspension and brakes though!

original 10.1" rear disc brakes and TINY sway bar:
http://www.turbosedan.com/ste/brakes_susp/DSC02383.JPG

the '88-'93 W-body rear calipers are notorious for siezing up and this is a perfect example. i upgraded to the redesigned '94+ style W-body calipers and 11" rear rotors. the only downside is i have to do something to get the parking brake to work i put the 22mm Addco sway bar in at the same time:
http://www.turbosedan.com/ste/brakes_susp/DSC02389.JPG

the original front brakes used 10.5" rotors. the '95+ W-bodies used a larger 11.25" rotor but the same caliper. in order to upgrade to the larger rotor i had to swap out the entire strut/knuckle assemblies from a '96 Cutlass. while i had the strut/knuckles out i installed the Intrax springs, KYB strut mounts, KYB strut boots, and new GM greaseable balljoints:

http://www.turbosedan.com/ste/brakes_susp/DSC02508.JPG

i'll be buying 245/50 tires to replace the stock 215/60s. i'm replacing the ugly 16x6 STE wheels with white 16x7 5-spoke wheels from a GTP:
http://www.turbosedan.com/ste/brakes_susp/DSC02572.JPG

i have quite aways to go yet with the suspension. tires, coilovers, KYB GR-2 struts and rear strut mounts are probably going to cost me another $1100.

btw, this is the Grand Prix that i traded for my old T2/A555 '89 Lebaron GTS last October. i miss owning a TD but my first love is the TGP.
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Joshua Mitchell
'90 ASC/McLaren Grand Prix STE Turbo - 1 of 1000
'91 Cutlass Supreme sedan - 3.1 Intercooled Turbo/HM-282 5-speed - 227whp/325wtq

[Force Fed Mopar]

Cool project man. A guy I know down the road from me is selling one, a '90, me and him have worked on it a good bit to get it back running. Has a new crank sensor, wires, fpr, I think a new fuel pump, etc etc. He says it's still not right, he says it will foul out the plugs really quick.

They're a cool looking car and rare too, good luck with it.

[Turbodave]

I was looking at a turbo grand Prix in locally about a year ago, the price was right but it needed a lot of work and I didn't want to get too wrapped up in another project. I still think they are cool cars. I'm a Mopar guy to the core, but anything with forced induction is cool in my book.

[Directconnection]

Sorry for not knowing...but there were factory turboed 3.1 cars from GM?

[GLHSKEN]

Yes, early 90's. It was their answer to the turbo spirits and other quick "family" cars. Then dodge went 16v on them and cleaned their clocks... Nice looking cars.

[Directconnection]

What was their performance #s?

The SHO and Lumina Z34 I thought was the competition?

[GLHSKEN]

Z34 twin cam was chevy's answer. Pontiac got 205 hp from turbo-charging.

[TurboSedan]

Cool project man. A guy I know down the road from me is selling one, a '90, me and him have worked on it a good bit to get it back running. Has a new crank sensor, wires, fpr, I think a new fuel pump, etc etc. He says it's still not right, he says it will foul out the plugs really quick.

They're a cool looking car and rare too, good luck with it.

sounds like he might have the original crossover pipe in there. the original pipe has really crappy flex bellows. a cracked flex bellow will draw air in, fool the O2 sensor and cause the engine to run really rich.

original crossover pipe (heat shield removed):
http://www.turbosedan.com/cutlass/en...s/DSC00894.JPG

rebuilt crossover pipe:
http://www.turbosedan.com/cutlass/en...builtXover.jpg

yes the TGP was rated at 205hp/225tq. i made 227whp/325wtq with:

- K&N cone directly on compressor inlet
- custom burnt TGP memcal for use with 5-speed
- M&M Racing MBC @ ~11psi
- no cat + generic straight through muffler on stock piping
- 5-speed swap (less drivetrain loss)

www.turbosedan.com/cutlass/dyno3.jpg

the engine had about 230,000 miles on it at the time of the dyno. it's actually the original Cutlass Supreme 3.1 shortblock (it's never been rebuilt). i turbocharged the previously NA 3.1 engine at 227,000 miles using TGP parts. i'm up to about 250,000 miles now and it's doing great. although no traction until 3rd gear
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Joshua Mitchell
'90 ASC/McLaren Grand Prix STE Turbo - 1 of 1000
'91 Cutlass Supreme sedan - 3.1 Intercooled Turbo/HM-282 5-speed - 227whp/325wtq

[iTurbo]

I get to drive TurboSedan's car once in a while and it is a blast, although the driveability leaves a little to be desired since the custom memcal isn't quite right. It has soooo much more torque than the original n/a 3.1 setup. It is also much easier to launch than any of my Turbo Mopars. If I were at a red light next to say, a '99 Mustang GT, I would feel way more confident in the Cutlass than my Shelby Lancer.

Even though the turbo is a little T25, it is a fairly large T25 and comparable to the TII turbo as far as power output. It spools up instantaneously, no need for brake torquing from a roll.