Just bought my first GTP, not a real newbie but need some advice

[scottyk]

Hey everyone, Im not new to the car game but I am defiently new to GTP's in general and I joined this site to learn about the smart way of modifying these things, typical problems and so on.. I am very impressed with it so far, I've had about a month so far, 2001 red GTP with 142,000 on it.

I have generally been a v-8 guy in terms of preference, I have a 2003 cobra with typical bolt on stuff, and a Fox body mustang that is a street/strip heavy nitrous car I built from the ground up and I could talk forever about these but probably no one cares...

Now I use this GTP to drive to work and back everyday, 120+ mile round trip so mileage is a conern as well.. Its runs well right now, I noticed the car seems to run very cool and leaks a small amount of coolant "intake" so I plan replacing the thermostat and lower intake gaskets, figured while Im in there I might as well put some headers on it, straight pipe from there to catback "no resonator or cat" put a 3.4 or 3.3 pulley along with my own intake kit. I have been debating doing some blower porting while Im inside.

Anyway what I need to know is, do I really need a aftermarket ECU with these mods?

and is there enough risk to justify a scan tool for KR?

has experience shown to effect mileage much with these mods??

Thanks, Scott K

 

[Bluemagic]

Dropping a pulley requires a tune.
Also scanning is mandatory when dropping pullies.

 

[machinegunsquid]

Anytime you drop a pulley size, you SHOULD tune the computer. You don't HAVE to, but if you don't, you will end up with a blown motor.

Adding an intake, with headers, and removing those flow restrictions will free up a few MPGs.

And your first mod should be a Scan-gauge, or a scanner/datalogger.

Also, you don't want to be dropping pulley sizes greatly. Don't go below a 3.4 setup, unless you go with additional mods (intercooler, cam, rockers, etc)


This shall be your best friend in the GTP world.
Otherwise known as the Grand Prix Modding Bible.
http://www.grandprixforums.net/safely-modding-your-3800-powered-car-17482.html

Welcome to the site, and glad to see you're enjoying the Grand Prix.

 

[scottyk]

I was looking into HPtuners, heard alot about them from LS-1 guys.. I dont know much about this software but it looks like it should control everything I would need as far as timing and fuel and much more, can it be used for multiple vehicles? and can it be used for scanning KR?

 

[txslow6]

Yes the HP tuners can be used on multiple vehicles. It's big in the GM world. You do however have to buy credits for the cars you want to use them on. So even after purchasing the tuner you will be required to pay $100 for each vehicle IIRC. Someone please correct me if I'm wrong.

Scanning isn't mandatory but helps you keep tabs on the car and is always a good idea.

As far as your fox goes. There are a few of us around here that enjoy them. I've got a 85 coupe with a 87 EFI F-150 block.

 

[scottyk]

I have a wideband I could put in for tuning, you guys usually tune the timing off of KR and then fuel tables off wideband readings I assume? How much change is generally required from stock settings?

 

[sLpGPGT]

i love cobras and f-bodys, so i would love to see pics of them ontop of ur gtp, and i wouldnt straight pipe the car, it would be very very raspy and wont sound good at all

 

[scottyk]

Typical bolt ons, lowered, pulley, tune, exhaust, intake, elec cutouts, shifter, rear brace, subframes, clutch, etc...

Fox body is a little more wild, garage built world block 429 with hand ported Victor Sr heads, 2 direct port kits, powerglide, held back by the 8.50 cage right now. Ran best of 8.22 at 164.xx last year before getting the boot, but has been faster since "I race 275 class 1/8th mile" These pics are from NLR meltdown race in Indiana and a couple from great lakes MDRA 275 class.. neither of which I won and yes it does RUN on pump gas and is street legal

 

[scottyk]

I dont have any of the GTP yet, guess I kind of consider it sort of a "beater" car, dont take offense though I love the car so far.. If its anything like the Cobra Im sure it will respond well to small bolt on parts

 

[sLpGPGT]

cobra needs COBRA inlays and vht tails, both cars look amazing, and yea alot of ppl use these cars as beaters or DD's, its a grand prix and not a racekar, although alot of ppl on here made there car pretty damn fast

 

[fastmvr]

Great looking stangs.....my GTP is a DD......my fun vehicles only have 2 wheels. Of course, having a GTP as a DD makes getting to and from work a lot more fun than my grocery getter Suzuki XL7......how the heck did that happen?

 

[matt5112]

Odd everyone jumped to tell you that you require a tune.

On the topic of aftermarket ECU, the stock ECU can handle 512 g/s of air before you have to play with any scaling.

On the topic of the tune, stock is sufficient for a 3.4 pulley. This "tune" everyone refers to is really just adding excess fuel to kill knock or pulling timing to kill knock. (<11.0 AFR gasoline, <16* timing advance WOT)

Adding an intake might affect your MAF calibration enough to require a tune.

Given the age of these cars, its a good idea to just throw a scan gauge at it and adjust pulley size accordingly.

Alternative is to use HPT to log enough time in the car to have a real nice safe tune for all conditions.

Yes the HP tuners can be used on multiple vehicles. It's big in the GM world. You do however have to buy credits for the cars you want to use them on. So even after purchasing the tuner you will be required to pay $100 for each vehicle IIRC. Someone please correct me if I'm wrong.

Comes with eight credits, which will allow you to make unlimited changes to four vehicles in most cases.

More on credits: http://www.hptuners.com/products/vcmsuite_vehicles.php