Stock Engine Limitations, 2001 GTP

[OJ_]

Greetings,

I have a fair amount of questions, hopefully someone can help me in these matters..

Does anyone know the HP and torque limitations on the 97-2003 model series GTPs? At what HP and torque should I begin upgrading the internals of the engine?

Also, does the supercharger require a certain amount of backpressure? or can I go willy nilly with my exhaust with no worries...

Last but not least, should I be considering strut tower brace and sway bars as I approach 300hp?

Thank for your time

OJ

[theblurr87]

Originally Posted by OJ_

Greetings,

I have a fair amount of questions, hopefully someone can help me in these matters..

Does anyone know the HP and torque limitations on the 97-2003 model series GTPs? At what HP and torque should I begin upgrading the internals of the engine?

Also, does the supercharger require a certain amount of backpressure? or can I go willy nilly with my exhaust with no worries...

Last but not least, should I be considering strut tower brace and sway bars as I approach 300hp?

Thank for your time

OJ

head over to cantsayItHere dot com (different website found by googling) and do a search or post..there's a ton of knowledgeable modders there.. from what i read the internals are good to well over 300 whp, with a few exceptions and of course it depends on the application. if you're going for a cam you might need stiffer valve springs, etc. you should prolly do the sway bars and strut tower anyway for a better ride. even on a stock GP they would be good... as for the exhaust you want to open it up with headers or at the very least a downpipe.. most people say the catback is good up to a certain hp well over 300

[BNaylor]

Originally Posted by OJ_

Does anyone know the HP and torque limitations on the 97-2003 model series GTPs? At what HP and torque should I begin upgrading the internals of the engine?

The L67 SII 3800 is very reliable and will handle 350 whp and up, however, the primary concern is getting the tuning of the engine done right to take advantage of the mods and limit potential problems areas like knock retard (KR). KR is the most overlooked area of modding a L67 and the biggest reason why owners blow their engines. To make more hp and torque above a certain level you will eventually need to go into the internals of the engine. Most likely cam and valvetrain. The ultimate solution to control KR and maintain high hp will be an intercooler.

Here is a general article on mods from ZZP which should answer some of your questions. Also, do a search function on past threads going back concerning mods. Lots of good info is stored if you take the time to look for it.

Click here

Originally Posted by OJ_

Also, does the supercharger require a certain amount of backpressure? or can I go willy nilly with my exhaust with no worries...

Exhaust backpressure has nothing to do with your Eaton M90 Gen3 blower. The engine does require some backpressure but you can do certain exhaust mods to limit backpressure. On a L67 exhaust mods are beneficial for more power and to help control KR. IMO CATBack exhausts do little to give you any significant power gains for the cost. More noise and MAYBE a better sound but it will never sound like a V8 powered car.

Originally Posted by OJ_

Last but not least, should I be considering strut tower brace and sway bars as I approach 300hp?

The strut cross bar and aftermarket or GMPP stabilizer bars will help your overall handling but have nothing to do with the relationship of what hp and torque you are making. The biggest problem as you approach power levels around 300hp will be keeping power to the ground and limiting loss of traction. Tires are a major factor. With my mods I have to use drag radials or the quarter miles and 0-60 ft times suffer.


Another area that is overlooked is the autotransaxle. It is the weak link even though GTPs have the 4T65E-HD version. A limited slip differential like from Quaife or other aftermarket companies will help versus the stock differential. The torque convertor is another factor and often overlooked.

Proper fuel supply will eventually be a concern. Fuel pump, fuel pressure regulator and bigger fuel injectors. As you can see there are alot of factors to consider.