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how to turn the boost up

'00 GTP
04-09-2003, 08:49 AM
is there any way to turn the boost up on a GTP? I know they run a max pressure of 7.5 psi. I was wantering if you could increase that some way......


04-09-2003, 10:19 AM
Ive heard ideas of changing the pully wheels around but Im not sure, Ill get a little more information on it and post back.

'00 GTP
04-09-2003, 11:55 AM
I know about the pullys, but is that the only way? I am thinking about putting a 3.0 pully on it. I have heard that it adds 40-50 hp to your car. I have also heard that you have to put a tranny cooler, and a cold air intake on it. do you all know how much that is going to cost me?

04-09-2003, 09:21 PM
Originally posted by '00 GTP
I know about the pullys, but is that the only way? I am thinking about putting a 3.0 pully on it. I have heard that it adds 40-50 hp to your car. I have also heard that you have to put a tranny cooler, and a cold air intake on it. do you all know how much that is going to cost me?

Well, you can put the pulleys on, but you have to make sure you dont add too much boost, because if you do you can burn pistons up and mess up gaskets and have all kinds of messes on your hands. But if you do do it, it would be a good idea to get the tranny cooler and the intake.

04-11-2003, 10:41 AM
There is NO way you can just bolt a new 3.0" pulley on your car without the supporting mods. All the mods in my sig were required in order for me to safely run a 3.25" pulley. BTW I'm seeing 12psi with this pulley.
I'll be hitting a local track on April 19th to see what my car will do modded. My best stock was 14.5 @ 93 mph with a 2.1 60' time. There are a few sites with really good information for GTP's and modding
They are.... www.oqcgp.com and www.clubgp.com. Check these sites if you are seriously considering modding your GP.

06-11-2003, 11:03 PM
In order to run a 3.4in pulley you need; U-bend removed, CAI, 1-2 degree cooler spark plugs, HD spark plug wires, and tranny cooler. To do a 3.25 You will need everything above plus; Cat-back exhaust, either water injection(about $350) or an intercooler(about $1100), DHP pcm, RT downpipe and to get the full effect do rockers or a cam at the same time.

If you dont do these support mods the first major issue you will run into would be boost stacking wich leads to Knock Retard, this is when the pcm senses that your engine is knocking and it retards your timing. If you ignore the KR then that would lead to engine failure.

Also with the 3.25 and supporting mods you will probably also need a Bullet proof tranny rebuild,
Level 10 performance (http://www.level10performance.com)
and an LSD because these will could break with that amount of HP.
For questions ask Zoomer (http://www.ZZperformance.com) there is a ton of good info on his site.
It is possible to go smaller than a 3.25 but you will need to do serious bottom end work because the stock 3.8 cant handle it.

06-17-2003, 12:16 AM
He doesn't necessarily need an I/C with a 3.25" pulley. I've seen people go to 2.8" pulley's without 'em. However, HEADERS, downpipe, O/R pipe (or high-flow cat), and catback will help.

Cam and rockers however should be done at this point though.

BTW, if you do rockers alone, go 1.9ratio, if you ever then had a cam, go with 1.75ratio.

gtp 2000
06-20-2003, 11:41 AM
i wouldnt touch the boost on the car, you can really hurt the way the car runs and cause some major damage to the motor, i dont feel it is worth it

99' Z-28
06-20-2003, 03:12 PM
i wouldnt touch the boost on the car, you can really hurt the way the car runs and cause some major damage to the motor, i dont feel it is worth it
I don't feel its worth it either. ChaosStarter, '00' GTP don't need headers in order to un that amount of boost. He is just going to need two new mufflers that flow about 300 cfm more than stock and a Ultra Flow Converter. He also don't have to have the U-Bend taken off although he will need to have his resonator removed.

06-20-2003, 03:39 PM
Not necessarily. For the 97+ GTPs, when it comes to turning up the boost and running into Knock Retard, the headers, downpipe, cat, and u-bend are the more restrict parts of the exhaust system. Our catback actually flows very well, it's everything before that that is restricted. Many people still have teh stock mufflers on.

If you were to go onto ClubGP or any other GTP website, you'll see that headers are usually always done at the 3.25" pulley or so, because it's one of the most effective mods for reducing KR.

99' Z-28
06-20-2003, 04:55 PM
If you were to go onto ClubGP or any other GTP website, you'll see that headers are usually always done at the 3.25" pulley or so, because it's one of the most effective mods for reducing KR.
Right, who is actually going to spend all that money on a set of headers?
The Cat-Back for the Grand Prix's 97+ is just basically getting rid of the U-bend and resonator and having a better ''T'' Pipe. People think the U-bend restricts alot of air and it really don't. The T pipe don't restrict exhaust flow much at all, but its not restricting enough to were you can't run 12 psi or even 15 psi of boost. A person can go out and buy 2 very good mufflers for about $80 and have resonator removed for $15 at a muffler shop.

06-20-2003, 05:21 PM
Do you own a car with an L67 or know anyone that has a highly modified L67? I just have a hard time taking advise from anyone who doesnt own the car especially from someone who owns a comaro with a V-8.

06-20-2003, 06:12 PM
Listen, by the looks of you Camaro, you know what you're doing, for that car. However, this is a whole different type of car that responds to things much different than your Camaro.

The resonator is not a flow-restriction point on our exhaust. The U-Bend, manifolds, and downpipe ARE. If all you do is replace the stock mufflers with anything, all you're doing is sound, with maybe a slight gain in HP. The pipes are still the same size, and you're still causing a restriction.

BTW, you couldn't even run 15lbs out of the M90, and if you were to, all you'd be getting is a hair dryer and a side dish of boost stacking.

navyblue 00gtp
06-20-2003, 06:27 PM
What in the world is a "t" pipe? :confused:

The downpipe is the most restrictive part of the exhaust, followed by the ubend. Replacing the ubend showed 6 hp on the dyno, so yes I would say thats a restriction. Removing the resonator doesnt really do alot, if you look at one, its simply a straight muffler used to reduce drone inside the car.

The cat back exhaust for the GP DO NOT replace the ubend. Its not simply replacing the ubend and resonator. Piping is increased to either 2.5 or 3" .

You can run a 3.4 pulley with few mods, as long as the car doesnt get any knock retard. I have a 3.4 with colder plugs, 160 thermo, cold air box, ubend and resonator removed. I have ZERO knock.

Like whats already been said, if you go below 3.4, you ll almost for sure need headers. And there are quite a few who run headers.

Going to a 3.0 pulley without the right mods will actually hurt hp bc of the amount of knock retard you ll get.

Changing the boost isnt going to cause any damage as long as you do it right. If you do it right it is well worth it.

Actually, you want to run less boost. Most of the guys who do headers, exhaust, smaller pulleys, rockers or cam have their boost drop. You run into heat problems or boost stacking if the exhaust isnt free flowing.

Just go to www.clubgp.com and do a search on pulleys.


99' Z-28
06-21-2003, 08:44 AM
Oh yeah, i almost forgot...I'm a :newbie: I don't know shit about Grand Prix's :shakehead

99' Z-28
06-21-2003, 08:47 AM
The cat back exhaust for the GP DO NOT replace the ubend. Its not simply replacing the ubend and resonator. Piping is increased to either 2.5 or 3" .
Your going to lose Horse Power if you increase the piping to 3inches or even 2.5. :lol: The reason being is that V-6 will lose and gain backpressure more than V-8's. If you have Too big of piping you will not have enough.
What in the world is a "t" pipe?
Its the pipe that makes your Y-Pipe a Y-Pipe.

06-21-2003, 10:17 AM
I would agree with that statement as far as teh 3" piping goes unless you are pushing SERIOUS hp. However, every catback system out there for the GTPs increases piping size to 2.5".

99' Z-28
06-21-2003, 10:35 AM
every catback system out there for the GTPs increases piping size to 2.5".
Yes, 2.5'' is fine. No bigger though.

navyblue 00gtp
06-21-2003, 01:47 PM
You want as little back pressure as possible with a supercharged motor. You re not going to lose hp with 3" pipe, you may lose some low end power/torque but pick it back up on the top end and hp actually increases. Which with the torque of the L67 and front wheel drive, this is a good thing. The MSP cat back is 3" so not every catback offered is 2.5". I agree 3" maybe overkill but it can be and is being done everyday.

The y pipe is a y pipe, not a t. Not being picky but it simply doesnt form a T.

The biggest restriction in the exhaust system is the downpipe. Its 2 1/4 on the outside but it is double walled. So actually, its a little over 2".

Do you have any basis for your arguements or are you arguing for the sake of arguing?


06-21-2003, 01:50 PM
Originally posted by 99' Z-28
Oh yeah, i almost forgot...I'm a :newbie: I don't know shit about Grand Prix's :shakehead

Not much shit anyway. :wink:

Smaller pulleys and other mods don't 'hurt' your car, they improve it. All the power adding mods I've done have improved my gas mileage. Now if you push your car too much you can hurt it, but you can do that to an unmodded Grand Prix too. I have a Thrasher CAI for intake.

My car could easily use a 3" exhaust system. Instead, I open a cutout before the Y pipe to eliminate the Borla mufflers for track racing. I have a cam, intercooler, TOG headers, 3" downpipe and a carsound high flow cat.

To handle the added power I have just rebuilt my transmission. I installed a hardened input shaft, 3.29 heavy gears and single heavy drive chain, Raybestos High Energy clutches for input, 2nd, 3rd, and 4th clutch packs, a Quaife torque biasing differential (posi), and a Pro Torque 245 mm TCC 300 torque converter. This transmission can probably handle 1000 HP safely. By the time I'm through modding and adding a ported blower, ported heads and an LS1 throttle body bored out to 82 mm, I'l be pushing close to 550 HP, so the transmission should be able to handle it easily.

06-21-2003, 11:20 PM
Although I like you plans for future mods The_Pope, but I really don't think, even with that many mods and future mods, that you won't be close to 550hp. I could see in the area of 350-400 (maybe), but remember, we lose a lot of hp to the ground with these trannies...

06-22-2003, 05:02 PM
Wont the tranny re-build help gain back some of that lost horsepower or does it just reinforce and nothing else?

Oh and Z you being new doesnt matter, you not owning a Grand Prix does. http://www.ebaumsworld.com/forumfun/newbie.jpg

06-22-2003, 06:18 PM
It just reinforces it. The only way to gain back lost HP is to put a manual tranny in there, and as pretty much anyone with a modified GTP knows, no FWD manual tranny will be able to hold up to the power that we will/do make...

GTP Racer
08-13-2003, 08:25 PM
The fastest way i found to add power to my 2000 GTP was to..

-K&N Cold Air Intake
-Magnuson Nose Drive
-Pulley Boys 3.75" Pulley
-Borla Cat-Back Exhaust
-Borla Headers

although this isn't cheap my GTP is running at 350+hp.. ( i have yet to dyno it)

08-13-2003, 08:53 PM
Dyno that thing, because I doubt you are over 230hp if even.

GTP Racer
08-13-2003, 09:15 PM
230hp tops?? haha wow buddy.. r u drunk.. u must have a SE 3100 Series Grand Prix

I have a GTP! with 240hp STOCK!, i had it dyno'd before any serious mods, only a K&N air filter and it had 244hp..

trust me with the money i spent i would drive my car into the atlantic if it decreased the horsepower

08-13-2003, 09:22 PM

crank hp vs. at wheel hp

usually when people refer to dyno numbers they give the hp at the wheels

good luck

'00' GTP
08-14-2003, 08:48 AM
I am throwing the BS flag on this one. first off these cars push 200-210 bone stock at the wheels. you only have a CAI not a FWI you are only looking at a 10 hp gain, prob 7 (I am being generous) at the wheels.

3.75 pully are you kidding me? that is like a 10 HP if that..

Exhaust I will give you no more than 15 HP ahh what the hell I will double the actule HP gain, and say that you are not loosing anything from crank to wheels so 30 HP

47 HP that will make it 257 HP..... unless you have a magic car, There is no way that you are any higher than that. and before you say it, yes I have a 2000 GTP 3.8 liter, I have a 3.4 pully, FWI, and a few other things... have you touched your boost controller, or the throtle body screen???????


10-06-2003, 01:39 PM
First off dont listen to that guy about exhuast size. GTPs have a SC, forced induction cars are totally different than N/A cars. 3' is fine on a GTP even more so if you do CAI, ubend, 3.4 pulley.
Second some of the GTP owners are a bit off on some things...
someone said youd get max 10hp from a CAI on the GTP, read here
http://easyperformance.com/CAI/Head_to_Head_Content.htm this shows about 17hp gained over another CAI, NOT OVER STOCK over another CAI over stock would be even more... gm intake is very restrictive, mind you that GTP was slightly modded making for better gains of more air. that car had a PCM, exhuast 3.25 pulley, getting 262hp at the wheels with no IC.
anyone with a GTP needs to goto this site and do some research, http://www.zzperformance.com/ They are simply the best Ive found when it comes to GTPs, they have people getting 12s with no IC and no KR.

Heres what i would do with your GTP, get the wizard CAI if you have the money other wise build your own with a 9" K&N and only goto a *3.4 pulley for now cause smaller will give you almost no gain without certain other mods like CAMs/rockerarms.

remove u-bend: $ exhuast shop can do this <8hp
180-160 thermostat:$12 < 1 or 2 hp
throttle body spacer: $50 <shown 30 degrees cooler inlet temps
3.4 pulley* use gatorback belts <25hp
cooler plugs like NGK TR6
For safty but dont need a tranny cooler from ZZP $220. and fuel cooler.

From there if you have the money and want more power
Mini-AFC 2.0: $150
VS CAMs: $300 from ZZP <40-50hp

from there you could also do plug wires and heat wrap. by the time you do cams it may be about time for an Intercooler. But only if youre getting Knock and want to go to really small pulleys like 3.0 and smaller.
You can get the 1st gen IC from ZZP for $1200 or there new 2nd gen for about $1600. With this you can take youre pulley sizes way down and start thinking 12's-11's in the 1/4 mile no BS!!! read up on it on ZZP. This might also be time to get high flowing injectors and new fuel pump. $300 for matched and balanced injectors. Im leaving my GTP stock looking on the outside and removing the GTP badge then once the IC in ordered and Im hauling ass people wont know what hit em! MUAHAHAA! BTW the numbers i quoted here are actually shown and tested on a dyno other wise i wouldnt put them up and wouldnt buy the parts myself for my car.

If you really have the money and want more ZZP has headers showing a huge 18hp gain over stock at the wheels thats about $730 though of course with all those other mods it would only help replease more HP. ZZP also has tons of porting mods to do to the SC and Intake monifolds and throttle body. These mods arent cheap but the more you mod the more these will add to the gains and should help reduce Knock if you dont have money for an IC. Oh you can also get a shift kit to get firmer shifts from pfyc.com and something to raise line pressure.

10-06-2003, 01:54 PM
BTW i when talking about the exhuast when i said "even more" when saying 3" was fine i didnt mean even bigger i meant its even more ok to have 3" if you have mods....

When youre at ZZP check out the members cars, some dont have even as much done as i say to do and get very good 1/4 miles.

heres a list in order that I am purchasing my Mods for a 99 GTP, if you have 98 or older add a ported 99 throttle body from ZZP.

I also think exhuast is about the last thing to buy on the GTP but it wouldnt hurt of course, getting the modded headers for $250 from ZZP and heat wrapping them or getting the coated ones would be about as much as I would do on the GTP other than u-bend removal. I mean 18 HP for over $700?!?! Not when this is all just for fun having exhuast isnt a bragging right its saying you cant find things that cost less than half as much for the same gains... I mean get cams and rocker arms and some head work for the same price and get twice the HP, come on people!
hehe thats all sorry if i seemed rude, i was just trying to inform a fellow GTP driver what his car can really do. I think the GTP is the cheapest car to buy then put the least amount of money into to be the fastest, cause you can get a 98 for 9k and put 4k into it and get 12s-11s and have a totally street rideable car still in stock trim. Maybe not the only car you can do this too much one of the better looking and Newer cars at least. Later guys hope I helped out. I just ordered a Gtech Pro competition so maybe Ill post my numbers soon! weeee

'00' GTP
10-07-2003, 11:01 AM
good god I can't believe that this post is still around.... :iceslolan

10-29-2011, 08:56 AM
Hey all, newbie here to this forum and GTP's. Just bought a 99 GTP coupe for $1200 bucks and after 2 new wheel hubs, ball joints, and outer tie rods its a really good running and driving car. I bought it to use as a work car but after driving it i thought "Damn, this thing is a monster!" So I'd like to do a few things to it, first let me explain whats been done already. Its got 193k miles on it, the guy I got it from said he had a new tranny put in at 130k, its got a tuned pcm, 3.4 pulleys, trans cooler, and the u bend delete, he said he turned the boost down but I can't find any info on how he would have done that. Anyone know about a way to change the boost without an aftermarket boost controller? Also it has no cat on it and the pod gauges the dude put in light up but don't actually work. I would like to put a CAI on it, but can't afford one right now, any good links on how to make one for the GTP?

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