91 vette
Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 949
Likes: 0
From: smithtown ny
91 vette
i have a question i hope you guys can help?? i have the tpis longtube headers with muffler eliminators and i seemed to have lost some bottom end the car is a 6spd, now should i put on a set of magnaflow mufflers for backpressure will i pick up some more bottom end also what would make my car not rev past 4000 rpm it stops pulling feels like the rev limiter is kicking in everything is new,cap rotor, wires ,plugs,coil,fuel filter,fuel pump it is a msd coil with the msd button?????? my friend had this same problem with his auto had a chip done by tpis no more problem but it should still rev to 4800 rpm okay two questions
Safety Car
Joined: Feb 2000
Posts: 4,564
Likes: 110
From: Austin Texas
Re: 91 vette (6spd)
First thing is to put a scanner on the car and see what the computer is doing.
Mine had a lot of knock-sensor data that had to be "isolated" by putting some insulation around the knock-sensor.
Before you start spending a lot of time/money trying to fix it, see what the computer is doing to the car....
Mine had a lot of knock-sensor data that had to be "isolated" by putting some insulation around the knock-sensor.
Before you start spending a lot of time/money trying to fix it, see what the computer is doing to the car....
Team Owner
Joined: Dec 2000
Posts: 90,675
Likes: 304
From: SE NY
Cruise-In II Veteran
Re: 91 vette (6spd)
Even though David Vizard recommends 1 5/8" headers for the mild SBC he says that most "losses" are due to lack of tuning instead of a need for back pressure.
Use the scanner to check the O2 sensor readings at WOT and if below 900mV use an AFPR to bump fuel pressure.
Also, bump base timing till you just see a little more knock retard at WOT; then back off a degree or so till knock retard returns to normal.
Use the scanner to check the O2 sensor readings at WOT and if below 900mV use an AFPR to bump fuel pressure.
Also, bump base timing till you just see a little more knock retard at WOT; then back off a degree or so till knock retard returns to normal.
Safety Car
Joined: Dec 2000
Posts: 3,767
Likes: 5
From: Jacksonville Fl
Re: 91 vette (6spd)
It could be timing or a mixture problem. Are you sure the timing is right? It can be tricky because a lot of times the balancer will slip on the rubber isolator and the timing will show incorrectly. Are you sure the injectors are flowing at full capacity? What are the adaptive/learned counts?
If the injectors are good...and you r not loosing fuel pressure at WOT, it could be as simple as chip tuning.
If the injectors are good...and you r not loosing fuel pressure at WOT, it could be as simple as chip tuning.
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Thread Starter
Burning Brakes
Joined: Jun 2003
Posts: 949
Likes: 0
From: smithtown ny
Re: 91 vette (BBA)
i had a idea that i might need a chip the injectors are from 5-o-motorsport they are 21lb and are brand new. i also have 52mm throttle body, accel lg tube runners that have been ported, ported plenum, and the relcator for the plenum, the vortex air box,160 stat. and i have the stock prom