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DonE DonE is offline
Wo ist die Rennstrecke?
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Join Date: Mar 2004
Location: Brooks, GA
Posts: 1,211
Originally Posted by RarlyL8 View Post
Nothing was changed but the headers. The existing Euro system was in excellent condition with no leaks. The new ones have all new hardware and I've detected no leakes. There is no O2 sensor or smog equipment of any kind on my engine.
The headers were responsible for the change in idle mixture. Don't know why myself as I did not expect the change to be significant. These headers are obvioulsy vastly different in design than the J-pipe configuration that was replaced, we do know that much. You can hear the pulses hit the turbo at low idle like a cammed engine.
Don I would think you should hear this cammed sound with your headers as well. Have you not experienced this?
No doubt it sounds great and sounds much better than the B&B I had.

I remember when I got my new stainless headers from Marco and how I couldn't wait to replace the short B&B header with my new custom equal length MM header. I spent all night ripping out the B&B and carefully installing the new set. Within a week, I went back to the dyno to see the improvements.

Initially, I found the spool was slower, but from 5000 rpm on, it felt good. When I got to the dyno, it was confirmed. I lost power up to 5000 but from there on, wholly crap it took off, nearly straight up. My problem was that I hardly ever drive at those RPMs on the street. But it sounded mean.

About 6 months later, I was in FL at a builder's dyno where the customer had his 3.3L CIS built and he replaced his B&B header and put 1 3/4 inch equal length pipes. The motor was at the builder not to initially be built, but to find out why the car was not putting out more power (owner spent huge $$). I went back home to GA and I later found out from the builder that they found the problem - the header was too big at 1 3/4in primaries. When they went to 1 1/2 short pipes, the power came up big time and they found they needed a different turbo (turbonetics) to handle the new-found wide power band (2800 to 7000 rpm). They also told me that the back pressure (the pressure between the head and turbo) also increased (sorry, can't remember the pressure they measured, but I think was around 8 psi?????).

So, even though I don't know all the physics and thermal dynamics of building a header, I know what I've seen and learned from my own experiences - short, direct pipes that keep heat and velocity up to a properly chosen turbo works best. I wish I would have kept a record of all those dyno's I did because data is the only way to argue these points.

Last edited by DonE; 01-16-2010 at 02:10 PM..
Old 01-16-2010, 02:08 PM
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