Supercharged 87 GTA need boost help!!!
 

okay so heres a little more information i just bought the car its an 87 gta has a stock 350 tpi but with an sn 93 paxton supercharger. the guy i bought it off of said that it had a water injection at one point but the pump went out and he never got around to fixing it.

so heres the problem it for sure needs tuned because wen it hits more than one pound of boost it like loses power so i feel like its detonating like crazy so no good (stopped putting it under boost after that not treying tofry the bottom end yet). so wat from here should i do?? i know it does have the hobbs water injection kit but im lost how to hook it up?? and as for a tune wat would be the best?? i understand since its a stock bottom end and its not reasonable to say i can run reliably more than 5-7 lbs of max boost!

any input would help guys i appreciate it!

Re: Supercharged 87 GTA need boost help!!!
 

intercool it, you'll always have coler air. Hook up a scanner (snap on red brick) to see if it detonates or if it's something else.

Does it have an FMU? What's the ign. timing set at?

Re: Supercharged 87 GTA need boost help!!!
 

yeah i for sure planned on intercooling it and not sure at all wat time is set at?? wat should it be set at? adn alright i believe wednesday i can get ahold of a scanner... buty still wat should be done for a tune, injectors and so forth??

Re: Supercharged 87 GTA need boost help!!!
 

SOunds like you are in abit over your head with this one.

Motor is a stock L98? Set timing to 6 deg base. If you dont have a timing control box, I'd get one and set it up to pull a deg of timing per each pound of boost you run. A bandaid right now would be to set base timing to 0 deg so its pulling 6 deg total and run 6-7psi max. I'm not sure how much those paxton kits put out but I think most stock L98 blower systems were 5-7psi.

You will need to adjust the FMU pressures to get the right air fuel ratio. If the motor runs good without the blower, then all you really need to do is adjust FMU.
I would also suggest tightening your plug gaps to .030-.035" or so, and maybe run 1 step colder than stock rated plug for safety. Detonation control is important.

If theres anyway you can unhook the blower belt and run on motor first, verify the tune is working then, before getting back into boost.

Also check to see if you have stock injectors as some guys replace the injectors on the blower kits without retuning so it could be pig rich under throttle.

Proper way to tune the motor is with chip burning equipment and software. Create a new custom chip to optimize performance on motor and then hook up the blower and FMU and see where that gets you. Adjust fuel and timing accordingly.

Re: Supercharged 87 GTA need boost help!!!
 

i have the same kit on my car now till my motor is done id run 2 heat ranges colder since you dont have either meth inj or intercooler i might have the instructions layin around for the meth injection i tapped a hole in my manifold for the hobbs switch and ran the pump to a tee in my washer bottle thats how mines setup but you need to find out exactly why the car isnt running right first like orrs said take the belt off and run just the motor and see whats happening then go from there and 5to 7psi is normal unless you change the pully you could get maybe 10 but without an intercooler your pushin the limits there

Re: Supercharged 87 GTA need boost help!!!
 

thats your air fuel ? if you don't have a wideband you need to get one . if your only reaching 1lbs. of boost then you have a pipe blown off ( boost leak ) somewhere an you may be running pig rich . get a wideband ! good luck