Compensating BPT valve for higher-flowing exhaust?

[slipnfall]

Hi folks, Quick question here. The EGR system is primarily reliant on the BPT valve to route vacuum to it's top port. Of course the more backpressure, the more the EGR operates. I'm installing a 2.5" cat-back, with cat test pipe(for now, can't afford a new cat too just yet), so I'm anticipating my backpressure will be significantly less.

What do you reccomend I do to compensate for the lower/lack of back-pressure? I'v disabled the BPT valve before, and the car ran significantly worse.... I don't want that to be an issue once this exhaust is installed... any ideas/suggestions? Also EGR is used to heat the air to provide a more distributor burn(to eleviate hot-spots).

EGR removal is out, I have emissions(and will have to get a cat by next year). Untill then though...

Thanks.Jamie

[NateDogg]

As Tony Soprano says, "Don't worry bout it."

[slipnfall]

For real? I would just hate to gain a 'lil hp from the exhaust, then have it drive like sheit from the egr/bpt.

[InsanityInc]

Just an exhaust won't affect it much, as the port is in a part of the manifold where backpressure is very high. If you're worried about it, don't get an aftermarket header though. I can speak from experience that the hotshot header (not sure about the DC sports one) causes problems with EGR operation.

[slipnfall]

Good deal, thanks. I was actually hoping to hear a response from you(I recall you always chime in about backpressure 'issues') I suppose I tend to over-analyse things like this.

While we're on the subject, we may as well round out the discussion.. When the EGR isn't operating as it should, and the ECM has told the vacuum solonoid to open(so it's expecting the EGR to be open/semi-open), what affect does this have on how the engine runs? Does the ECM blindly(or with closed-loop feedback) lean out the mix, or advance the timing?

Thanks again, good to know. I plan on taking some vac readings from the BPT when it's installed, just to ease my own curiosity. I believe I read it only takes about -5inHg to open the EGR.

Cheer,'slip

[InsanityInc]

I'm not entirely sure what the ECU does on the KA, but it varies from engine to engine as to how it's handled. It seems to make the car run worse when it doesn't work, that's for sure. However, I also have a CA model, so it may do something even funnier to try and reduce NOx when it detects an EGR malfunction.