Compressor Surge

[bigtommy83]

It's only daily driving, not even boosted, it's still in vacuum when i shift, gas mileage you know. I don't get any surge at high rpm shifts, the BOV does it's job. I think I am just paranoid. First turbo car and all. I haven't worked on any turbo cars either because I missed the Kcar turbo era at work. Thanks for all your guys and gals help.

[Dalite]

quote:Originally posted by bigtommy83

It's only daily driving, not even boosted, it's still in vacuum when i shift, gas mileage you know. I don't get any surge at high rpm shifts, the BOV does it's job. I think I am just paranoid. First turbo car and all. I haven't worked on any turbo cars either because I missed the Kcar turbo era at work. Thanks for all your guys and gals help.

Tommy, the design of the turbo being integrated in the exhaust manifold makes the BOV only useful for making noise. All venting is done within the turbo/exhaust manifold, and there is no chance of the turbo being stalled.

The same goes for over-speeding the turbo input with intake mods. Whenever more pressure is measured in the intake than the PCM is programmed to see, it is vented.

Do a search for posts by 3barboost. He did a great job of explaining this, and how the system worked.

What you are probably hearing is the noise being amplified throught the up-pipe. Also, Stage I is programmed to go to a rich mixture when you "back off" the gas, to produce a burble through the exhaust. This is something you hadn't heard before, and may be confusing. And, we are all always more critical or aware of things that meke new noised whenever we complete a mod.

If you have bypassed the vacuum plumbing at the passenger firewall, you may have some problems in the timing of the Surge valve and the venting of pressure, but you would usually see either p1188 or p0234 errors (or both). If you aren't seeing these, chances are that you are not getting any actual surge problems. Most of these problems were due to the speed that the PCM alternated the TIP sensor between barometric pressure and actual Throttle Inlet Pressure.

Remmeber that the turbo starts spooling at 2300 RPM, and the real power comes after 3500 RPM. The band between 2300 and 3500 RPM seems to be the area where trouble is most likely to pop up; especially if you are in too high of a gear. This seems to be one of the weakest links in the PCM programming.