GN Turbo Power for road racing an 87 GN?

[vintageracer]

I am new to the GN seen as far as performance upgrades. I am and have always been a "road racer", not a drag racer. I have not been down 1/4 mile in over 20 years! I do however road race 4-6 times a year in Vintage races across the country in addition to marque specific club road racing events . I have just purchased my 2nd 87 GN. I will be doing suspension upgrades for handling/braking while maintaining a stock or close to stock drivetrain. Overall power is not a problem, just when and how that power comes on is a BIG problem.

I have seen MANY engine performance upgrades for drag racing a GN. Has anyone or is anyone doing engine modifications for a car that will be used for serious road course driving? The Buick turbo power is incredible however it seems to be incredible (too much) at the wrong time when braking or coming out of a corner. Are there modifications to flatten/equilize/feather the turbo boost for more even power or am I stuck with power that is more on/off?

Thanks for your advice and input.

Mike

 

[bruce]

I am new to the GN seen as far as performance upgrades. I am and have always been a "road racer", not a drag racer. I have not been down 1/4 mile in over 20 years! I do however road race 4-6 times a year in Vintage races across the country in addition to marque specific club road racing events . I have just purchased my 2nd 87 GN. I will be doing suspension upgrades for handling/braking while maintaining a stock or close to stock drivetrain. Overall power is not a problem, just when and how that power comes on is a BIG problem.

I have seen MANY engine performance upgrades for drag racing a GN. Has anyone or is anyone doing engine modifications for a car that will be used for serious road course driving? The Buick turbo power is incredible however it seems to be incredible (too much) at the wrong time when braking or coming out of a corner. Are there modifications to flatten/equilize/feather the turbo boost for more even power or am I stuck with power that is more on/off?

http://www.t6p.com/forums/showthread.php?t=6570

There's a whole series of threads there, that you might find interesting.

 

[vintageracer]

Bruce,

Thanks for the link. Just what I was looking to find.

I have several other GM cars set up with the Pole Position arms, tall ball joints etc and they drive very nice and aggressive. I saw the listing on one gentleman's engine setup. What can be done to a stock 87 GN engine to "level" the turbo power so it does not come on so hard and fast? It's pretty easy to blow the rear tires out of a corner when the turbo hits hard. Not really looking for more power just ideas to lessen the aggressive nature of the stock engine power as the turbo spools.

Merry Christmas!

Mike

 

[JDSfastGN]

You can put a slightly bigger turbo on the car to produce a little lag (still may blow the tires off when it hits full tilt towards the top of first gear) or have a chip burned to be a little fat on the bottom end to kill a bit of low end. Honestly i would work on the suspension and tires to put it to the ground as well as you can (a good set of nitto road race tires should plant the rear pretty good on a stockish GN i would think?). It may just be me but i would think you would rather have too much power causing controlable oversteer rather than a lack in power. Good luck with it man.

 

[vintageracer]

Lot's of power is great however it depends on how quick the power hits as it can and will provide a lot of oversteer. Brakes and suspension upgrades are area of primary interest for upgrade. The roll center is way off, bumpsteer to great, scrub radius bad and brakes to poor on a stock G body/GN so upgrades will start there.

I have found over the years that you can go a whole lot faster on a road course track with a good suspension setup/BIG BRAKES than just adding horsepower. I run group 6 in SVRA/HSR with big (cheater) V8's and lots of suspension goodies. In both cases the vintage cars run a whole lot faster now than they did when they ran Trans Am in 60's/70's.

My concern with the turbo car is the quick spool of the turbo with an automatic. I've driven 930 Turbo Porsche's and they also come on hard but the gearing of the manual transmission makes that manageable. Besides Porsche's have their own unique handling due to the rear engine. I have been told that the Buick turbo engine with a manual transmission IS NOT a good idea. After questioning the folks who tell me it's not a good idea it always goes back to a reason for drag racing. Since most of the Buick Turbo guys are drag racers I was hoping to find a few road warriors who could offer informtion.

I'll ask the question, why not put a manual transmission in a GN that has a road/track car setup that will not be drag raced?

Thanks for the input and responses.

Mike

 

[UNGN]

There is nothing wrong with putting a stage II motor with a manual transmission, especailly if you run low boost (to save the trans). You can have an easy 500 RWHP in a light package that is bullet proof. Many SCCA and IMSA races have been won using this combo. The only drawback is the $$$$$$.

A production motor kind of sucks for this application, however. The block is weak in thrust and the the crank breaks after 6K RPM, so don't miss a shift.

 

[bruce]

Not really looking for more power just ideas to lessen the aggressive nature of the stock engine power as the turbo spools.

I've wound up with a TA-62 in large part to kill the bottom end.
Then with a F/M intercooler, it just helps to dampen the inertia of the incoming air column, in addition to keeping the air a bit cooler. A low resistriction exhuast helps the top end. Often ignored, is having enough injector, while lots of people size their injectors, via estimated ET, you, IMO, should be more concerned with the accleration enrichment, and go with the 60 PPH injectors. A smaller converter with a conservative stall, helps to get things spinning a lil quicker, when in and NO IN boost. With the F/M you can run on of the RJC light AL crank pullies. You need to make sure the fuel system is to to snuff. Same with the ignition. You'll be putting things under load alot more then the normal street guy, so attention to details for ignition, and fuel are gonna be really critical. Some will say running a double pumper fuel pump would be over kill since your not running in the 10s, but, in sustained WOT conditions, I'd suggest it (it made a difference for me). Then the biggest AL rad you can get.

The tune really gets to be an issue......
The *normal* chips are again based on alot of drag racing... So you'll probably want a Translator +, or MAP PRO. Be prepared for alot of work for running in boost conditions for mins at end, to take time to sort thur. A WB, EGT, and good datalogging are great assets....

 

[Lee_Burough]

I am new to the GN seen as far as performance upgrades. I am and have always been a "road racer", not a drag racer. I have not been down 1/4 mile in over 20 years! I do however road race 4-6 times a year in Vintage races across the country in addition to marque specific club road racing events . I have just purchased my 2nd 87 GN. I will be doing suspension upgrades for handling/braking while maintaining a stock or close to stock drivetrain. Overall power is not a problem, just when and how that power comes on is a BIG problem.

I have seen MANY engine performance upgrades for drag racing a GN. Has anyone or is anyone doing engine modifications for a car that will be used for serious road course driving? The Buick turbo power is incredible however it seems to be incredible (too much) at the wrong time when braking or coming out of a corner. Are there modifications to flatten/equilize/feather the turbo boost for more even power or am I stuck with power that is more on/off?

Thanks for your advice and input.

Mike

The TTA seems much better suited to your interests....Have you considered one?

 

[Ormand]

You listed a lot of the reasons that the GN is not a very good road race machine. Bad weight balance (about 55/45) high center of gravity, poor suspension geometry, and bad brakes. UNGN mentions the problems with the engine. The crank and rods are cast, not forged, and the engine is just not suited for high rpm. That's one of the reasons the automatic transmission is well matched to the engine, for street and strip. A stage II, with forged crank, etc, would be better for a road race engine. In the Buick book, "Power Source", there are specs on a Stage II engine used in trans am racing, as well as a photo of the trans am regal. The body is FAR from stock, and the suspension is probably full race. That engine made peak power at about 7500 rpm, and peak torque near 5500. Of course, the car had no A/C or radio, and a stripped interior. With that kind of set-up, a manual trans would work fine. But by the time you do that much work, the car won't be a GN any more. :frown:

 

[turbofish38]

Bruce,
What can be done to a stock 87 GN engine to "level" the turbo power so it does not come on so hard and fast? It's pretty easy to blow the rear tires out of a corner when the turbo hits hard. Not really looking for more power just ideas to lessen the aggressive nature of the stock engine power as the turbo spools.

I have done a few open track events with my GN. Pretty much stock motor and the usuall bolt ons for the suspension and stock brakes. The stock turbo Buick has a pretty much for a lack of a better description, flat torque curve.Or it can be tuned that way with the usuall bolt ons. From what I hear not as spikey has the 930 you have seat time in. Try just easing into the gas. Use the oversteer to your advantage in the corners. Ride the brakes to keep the boost up, but dont just pump the pedals around the course. Just like the 930 the TR does violent things when you let off the gas. I was able to get away for years on the basically stock suspension by using a technique of keeping the boost up in the corners and using the throttle to keep the understeer under control without making me look like I was "drifting" around course. If I made the mistake of getting off the gas to quick than the car would plow into the turn and I would loose the momentum I gained on the straight. As far a sitting the engine up there aint any. How much HP can you and the car handle? Pick a power level and go for it. I would tune my GN so I was just a tad faster than the fastest car that would show up which was usually a Viper GTS or other exotic car. A fast spooling engine is an advantage for any type of racing. You just have to disipline your self when you are on the track. The boost isn't like a switch on our cars with only an on or off position. Think of it as the knob on that switch that you can gradually turn up or down the boost as you need it.

 

[mybuick]

ive always wanted to do road racing with mine but every body around me with tr's say "its only a drag car!!! why would you road race it!!!! its a brick!!!!" so i drag it anyway...

 

[VadersV6]

They do make real boost controllers (a bleeder valve is not a boost controller).
They are electronic units that can control most aspects of the boost curve. You can dampen it or strengthen it at a given rpm, or do whatever you want with it.

 

[SPEEDSTAR]

I am building my turbo-t as a road race car, I believe they can be made to handle reasonably well, with wide sticky tires, adj. coil-overs, 700 lbs. frt. springs, large disc brakes, and plenty of chassis stiffening,and a big alum radiator to keep it cool,........besides handling well, it will still go fast in a straight line......Jeff

 

[UNGN]

The TTA seems much better suited to your interests....Have you considered one?

After 5 years of Open Road Racing my '86 Pontiac 2+2, I've decided to start heading this route.

The 2+2 is fast and fun and will run with Vipers and regular C5's on a FAST course (especially if its slick and rough) and is WAYYY easier to make fast and handle good vs. a classic "Muscle car", but it's still kind of a truck.

We'll probably always use the 2+2 on 100+ mile ORR's, but for the shorter ones, I'd like a car that will do 100-140 a little faster than we currently do, something wider with a lower center of gravity and something I can put tires bigger than 255 wide on without making it look too much like a race car. A 2.72:1 geared TTA should be the answer. I just need to find the time to begin the modifications.

 

[Lee_Burough]

Nice looking car!

I remember reading how a TTA won the National meet for road racing or autocross (two or three years ago).... The TTA beat Corvettes, Vipers....Everything!

 

[bruce]

The trouble with the TTA as well as any 3rd/4th Gen F-Body is that if you don't just run the highest rate spring, stiff shock you can find, then you wind up with axle tramp under serious braking. If you race on pool tables, and don't drive too fast on the street, it's livable. But, the only good real answer for the rear suspension is using/ finding one of Herb Adam's Reese Bar Rear Suspension kits. That kit allows for decoupling the braking forces from the torque arm, and allows for using a shorter torque arm, both are great additions to the rear suspension *design*.

Then as far as the front end, a Morrison coil-over conversion makes all the difference in the world. Trouble with that is the lack of springs, in different rates.

Having a double A-Arm set-up, IMO (having used both) outweights the lower C/G and any other alleged advantage of the TTA. Then the 4 link GN rear suspenion while not perfect is still better then the oem torque arm.

And while the GN is no torsional regidity champ, chassis wise, the 3rd Gens for road racing need a serious amount of work to get to the level of a GN, IMO.

 

[vintageracer]

UNGN,

Nice 2+2! I also have an 86 2+2 as my daily driver. Just got out of the car 5 minutes ago from a 300 mile "walkabout". For me that's a road trip to look at cars for sale. I do this at least once every 3 weeks. I thought I was the only guy who knew or cared about 86 Pontiac 2+2's! Found another one this week that is REAL rough however it may be REAL CHEAP.

What brand/size of wheels are you running on the car. I have just ordered a set of 18x9.5 and 18x8's ACE wheels for the 2+2 and/or my GN.

Mike

 

[UNGN]

What brand/size of wheels are you running on the car. I have just ordered a set of 18x9.5 and 18x8's ACE wheels for the 2+2 and/or my GN.

Mike

The wheels in the Picture are factory GTA "front's" (16X8) with 255/50 tires all around.

We have since gone to GTA "rears" in the front because the Baer brakes space the tires out enough we would get a little fender lip rub in hard cornering (cars behind us thought it was oil smoke, but the tires were smoking). With the rears on the front, the rub is completely gone.

The grand prix's rear fenders seem to be a little narrower than a buick because our 255's are against the frame as close as I feel comfortable (3/8") and yet the outer edge of the tread is even with the fender lip while 275's fit easily in a buick. 9.5" wheels might need a frame notch or the fenders massaged out to work on a 2+2.

 

[turbofish38]

something wider with a lower center of gravity and something I can put tires bigger than 255 wide on without making it look too much like a race car.

Here is pic of my car the way it was set up about 5 years ago. Those are Pantera/930 meats on the back. The rears are 285/40-15's and the fronts 245/50-15. Its hard to tell but it sits about 2-3" lower than stock and there is probally another inch left before the tires would start rubbing. I never went in and measured anything so I dont know what effect it had on the center of gravity. I have another Regal that I would like to knotch the frame and mini tub so I can stuff something in the 325/355 range with maybe 295/315 on the front. I also would like to try to do this with air bags as I'm getting lazy in my years and I want to see how infinetly adjustable that system is. Now all I need to do is find the time and money to do it all at once.