Factory Boost Settings

[Bob Sweet]

I have an 88 Shelby Z 2.2 T2. I just got it back up and running after resetting the timing belt which was off. It runs much better. I hve timing set at 12 degrees. The car will only boost to about 5 psi at lower rpms. Is this normal? I can get about 10 psi in the higher rpm ranges. Does the factory limit boost in the lower rpms? I am using the factory wastegate solenoid to control boost. I put a red restrictor in the waste gate line at the turbo. Should the restrictor be facing the wastegate can or the solenoid? Does it matter? I have a grainger valve that I can put back on. If I use the grainger valve do I leave the restrictor in the line? Thanks guys.

Bob

[shadow88]

Factory turbo 2 boost setting is aprox. 11 psi. It varies with temperature. As for you restrictor concern, I don't think a restrictor matters which way it points. I used a vent the the wastegate actuator.

[GLHSKEN]

All the cals have limited boost below 4000 RPM. This was done to save thr trannies. I know for a fact the GLHS LM's limited boost to 7psi below 4k RPM.

Stock is 12 psi boost for all t II cars..

[Bob Sweet]

Thanks guys. I have the cam tming off. I am going to fix that and then see what I get.

[GLHNSLHT2]

boost is limited to 10psi then ramps to 12psi. You'll also need a yellow restrictor (T1 suckthrough cars have them too) into the line that goes from the actuator to the turbo. Just follow the vac diagrams on www.thedodgegarage.com or the back of the factory FSM's.

[Bob Sweet]

I have a red restictor in there now. That is what the part catalog called for.

[oldgregg]

boost is limited to 10psi then ramps to 12psi.

It's the other way around, 12 then back to 10.

[GLHNSLHT2]

would you like to see the factory boost curve ?????? Try D-Cal on Yahoogroups and download the 87 T2 171 calibration. It's on the "boostvsrpm" table. The only time the boost ramps down is if the car get's hot or it knocks.

[Bob Sweet]

I got my boost back. I had tee'd the vacuum source to the wastegate solenoid and the purge solenoid together beacause I was out of ports on my vacuum block. I ran seperate sources for the both of them and hooked the vacuum source for my blow off valve up to the nipple on the turbo. It will now boost to 6 psi till around 3500 rpm and then goes up to 12 psi above 3500 rpm and drops back to 10 psi or so after a few seconds. I am going to hook up my grainger valve and set it for 12 psi. Do you need to remove the factory restrictor when you use a grainger valve? I was going to put it close to the wastegate solenoid for easy adjustment. Should I bypass the wastegate solenoid all together. Thanks for everyones help.

[GLHSKEN]

I allways left the restrictor in. I'm also one of the few that left the entire wastegate solenoid vac lines in place. Plumbing the grainger between the solenoid and turbo. This makes it easy to swap back to computer control in about a minute.

[superD]

whats the maximum boost the stock t-2 can make?

[Dave]

would you like to see the factory boost curve ?????? Try D-Cal on Yahoogroups and download the 87 T2 171 calibration. It's on the "boostvsrpm" table. The only time the boost ramps down is if the car get's hot or it knocks.

It doesn't matter what your D-cal tells you. I've seen it myself, boost drops down.

Of course this if for a 89+ T1 car. Still on one of these it goes to 11psi then drops to 7psi. Chrylser wouldn't change it.

[GLHSKEN]

whats the maximum boost the stock t-2 can make?

Maximum boost pressure is deceiving. Max whp is 270-280 range and that is way overspinning the turbo. Some cars do it at 18-20 psi (lighter cars) Others have seen 25psi out of the turbo (heavier cars that put more load on the drivetrain)

Example, My car (GLHS) would ramp to 21 psi in the 1/4mi. From the 1/8 mile to the line, the boost would fall to 18-19 psi slowly. The car was maxxed out for what it had and consistantly ran 108-109mph at 2600lbs. At 5000+ RPM, I was burning every bit of air the turbo could pump through the engine.

[GLHNSLHT2]

It doesn't matter what your D-cal tells you. I've seen it myself, boost drops down.

Of course this if for a 89+ T1 car. Still on one of these it goes to 11psi then drops to 7psi. Chrylser wouldn't change it.

Read a bit more clearly, we're talking T2 cars. You are correct the 89 T1 cars boost level does start ramping down at 5300rpms. And Dcal takes all the data points and interpets them into a graph line. It shows you exactly what the computer is doing. So yes it does matter what dcal says.

[oldgregg]

Read a bit more clearly, we're talking T2 cars. You are correct the 89 T1 cars boost level does start ramping down at 5300rpms. And Dcal takes all the data points and interpets them into a graph line. It shows you exactly what the computer is doing. So yes it does matter what dcal says.

I've owned a few TII cars & on ALL of them I've seen it ramp down to 10 psi after 5 -10 sec or so while at WOT.
IIRC it's done that way on purpose so people don't ruin their engines running at max boost & WOT for extended periods.

I don't know what dcal is but it obviously is misinterperting this part.

[GLHNSLHT2]

Dcal is a calibration editing tool like CHEM. you have a bin and a tbl file and you can see what the settings are in the computer. Boost goals, AIS kicks, fuel graphs etc. I've looked through lots of different calibrations over this and the only thing that would have boost ramp off that's not in the boostvsrpm table is detonation and coolant temps. The 89 T1 does ramp boost down after 5300rpms, the 89 T2 does ramp it down after 6300rpms (who's ever over that?) But the 87 and 88 T2 cals have full boost through the entire rpm range after ramping up from 10psi at 4000ish. They don't ramp down.