Not seeing full boost

[Crx89]

Hi I was wondering if anyone can steer me in the right direction to figure out why I am not seeing full boost, I should be seeing around 8 psi. I had the car tuned a year ago and I was getting full boost. I verified there is no belt slip. Car was tuned on 92 and E85 flex fuel sensor. I did not have a flex tune though. Car runs good otherwise

Zc dohc Obd0 to Obd1
jrsc
Colt cams

[Spunkster]

Could be a problem with the bypass valve or a worn supercharger.

[Crx89]

Thanks for the reply, the supercharger was rebuild right before I had it tuned. I checked the bypass valve, it seems to working correctly, will need to verify the valve is fully closing. I was thinking maybe it had something to do the TPS , it looks like it never sees full throttle from the data log. Any thoughts?

[Spunkster]

Your TPS never goes above 80% in the datalog. That could be an issue.

[Crx89]

Yes I was wondering that also.

[Crx89]

Can anyone explain why my tps can read 100% when I am in neutral costing and punch it but when I have it under load it will not get past 80% and will not get above 6000 rpms.

[Spunkster]

Check that the cable is not loose. You could have a bad TPS sensor.

[Crx89]

The TPS sensor is new and calibrated. I double checked the throttle cable and is working fine.

Can you answer another question, is the stock map sensor a accurate way to measure boost or could it be off a few psi? The reason I ask is my mechanical boost gauge reads higher than the map sensor. When I had the car tuned the tuner told me the mechanical gauge was reading 2 psi lower than the map, now its the opposite. Trying to figure out why the boost is reading lower on the map than what the tuner said it was making.

[Spunkster]

The MAP sensor should be accurate. More than likely the mechanical gauge is off. It also depends on where it is getting its pressure reading from.

[Crx89]

Thanks Spunkster, The mechanical boost gauge is connected post blower to one of the manifold ports. I am getting approx 6 1/2 psi of boost which leads me to believe there is no problem with the blower. The tuner told me the car was making 8.7 psi and he was going off the map, so something is up since the data log shows around 5 1/2 psi. According to my pulley combination 8 to 9 psi should be correct.
The car has other issues as well, it will not reach 100% on the tps under load and never reach's 7000rpms.