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picked up new car/got ?'s

N

nyls1346

New member
hey i just picked up a 99 gtp 4door with some mods

after reading on here for a little im actually a little concerned of them lol

mods

headers
exhaust
cai
3" blower pulley

the cars feels pretty quik, but it sounds like theres a bad lifter cause i took the blower belt off and the noise is still there

i am not sure if there are any other mods cause i didnt take car apart yet lol, I bought it from an auction in jersey so there was no description of the mods

I think it prob has a 180 or 160 stat cause the temp stays around 180 while cruising, it might have a small cam cause the idle seems slightly rough ( not as smooth as a regular gtp would idle), and it is definately tuned because i pulled the tune with my hptuners and the secondary o2 is set to not report any faults..

I did a little datalogging and it made between 12-13psi boost at full throttle, and it showed up to 7.5* knock

so i know i have somethings to look at, but not sure if its setting the knock sensors off cause of the possible bad lifter
 


supercharger pulley is way too small. do not go into boost. the thermostat is also too cold.

pulley up back to stock and retune. then drop pulleys SLOWLY until you run into knock and back it off another 0.1" or 0.2".
 
its a billet 2 piece pulley, I measured the diameter of pulley and got 3" so i would imagine it is a 3" pulley ( theres no writing on it)
wut size is stock, I was gonna say try out a 3.4" pulley cause it seems that would work the best with my mods from what ive read on here..

does a 3" pulley typically produce 13psi

Im an f-body guy and i tune with hp tuners on ls engine cars..

im gonna pull a stock tune file from the tune depository and see what was touched and everything
 
stock is 3.8"

typically you want to keep the car around 10 pounds of boost for best results. you pushing 13 on a 3.0" makes me think you have some internal work.
 
Im gonna pull the plugs tomorrow as well cause myy gas mileage seems kinda poor, do you think some ngk br7ef plugs will be good,(ii have a bunch of them new for my camaro)

Wut is the reason for not going above 10psi, is it because the ve table, i noticed it only goes up to 140kpa

Btw thanks for ur help
 
sadly you'd need TR6's

your MAP sensor is a 2 bar map sensor (granted its stock) so it'll detect up to 14.6 PSI of boost.
 


Yeah well the map table only goes up to 140kpa and thats maybe 6psi so ur stock operatting system will only read up to that much unless there is an upgraded os, but seeing as how these cars have a maf sensor as well u can tune with the maf which is how the ecu reads beyond the stock ve table limits in kpa
 
I've seen map readings higher than 6 PSI on a regular basis.

these cars don't use the VE tables for fueling unless the MAF has been disabled.
 
Yes that is true, the map is a 2bar so in the scnner you can read up to 210kpa, but like you just said, they are using the maf above certain rpms ( i know in the other LS gen cars, they run in a hybrid mode, it uses both tables up until certain rpm and other factors)

But is there anyway for me to tell if this car has a cam beside tearing it apart...
Maybe vacuum a idle, usually bigger cams have less idle vacuum, what do these cars do stock
 
the reason why i said around 10 pounds of boost is because that seems to be the sweet spot for us. anything more and we usually just start creating too much heat for it to be worth it.

besides vacuum differences, you wont be able to tell unless you take the cam out. even knowing that the vacuum is 'off' from stock, you wont be able to tell what cam it'd be. normally youd see closer to 20 in/hg on a stock cam, but it varies a lot based on the condition of the motor. for example, mine only idled at around 16 in/hg. it's really different for each car.
 
oh ok i see wut ur saying on the heat with boost, so if i added the intercooler setup then i would be fine with this amount of boost..

also bio whats ur take on the plugs, do u think running the br7ef's is not a good idea, i really dont see what would be the problem ( i actually think it would be safer for less chance of detonation than with a tr6)

and what size injectors are in these cars stock, i noticed my duty cycle was peaking at about 115%

also wut kinda p can the stock fuel pump handle, and would a walbro 255 drop in the tank
 


the plugs, im not sure. ive never heard of the BR7EFs before. i always ran autolites.

the injectors are 33# stock.

the stock fuel pump can take a lot of power before it starts to not be able to keep up. the walbro can be dropped in, but it's not as easy as dropping it in.
 
ngk br7ef is a stage colder than a tr6, tr7 and br7ef are same heat range but the tr7 are projected and the br7 isnt (it goes something like that lol)

i pulled up a stock tune file from a 98 gtp and my car was definately tuned cause they touched alot of different tables, has a bit more timing than stock, maf and ve tables are different

unless the 98's are different
 


ok well i couldnt find a stock 99 gtp file, what about the 2000 models, is there any differences..

update!
i pulled the plugs and they were autolite 103's and are in decent shape and it appears all cylinders are firing the same and no internal issues are noted from the look of the plugs

I then performed a cylinder leakdown test and all cylinders except 1 & 3 only show 1 - 3% leakdown which is awsome for 160k miles (if original engine)
cylinder 1 shows 10% leakdown and it leaking past the exhaust valve
cylinder 3 shows 20% leakdown past the exh valve as well

now should i pull the head/heads and freshen up or try to run some gm top end cleaner or sefoam product to try and clear off possible carbon on those valves

the car has 160k on it and i gotta pull the manifold off anyways because the lifters are making some noise

i also see these heads are cast iron, do they sell aftermarket aluminum ones, i can see that beeing a great advantage and eliminating all of the detonation issues with these cars
 
Yeah at a $2100. Price tag i tbhink ill stick with what i got lol, imsurprised theres no stock aluminum castings that can be swapped on...

But wuts ur opinion on my leaky exhaust valves, should i try some top end cleaner stuff or just yank the head since ill be changing the lifters anyways
 
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