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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Not an expert, just my thoughts.

Originally Posted by RarlyL8 View Post
The most glaring example that we are all familiar with is the USA vs Euro 930 heat exchangers. The '78-9 Euro 930 is rated at 300HP while the USA version is rated at 265HP. The major difference is the headers/exchangers. That is the #1 upgrade I suggest to folks who have the US system.
I am not saying that header or muffler design dose not effect performance on a turbo. Most have to agree that the original US 930 HE's were very poor. Bruce Anderson / Jerry Woods sense the 70's have also make also been suggesting changing these to euro style HE's as a first mod. They also note if this is not done, adding SC cams will not be of benifit.

I suspect there is much more dammage with a poor design on a 930 than potental to be achived through a perfict desigh.

I also believe the euro cars also did not have as much restriction on the cat/muffler side as the US cars and I am not sure but I seem to recall the factory boost spec range for US and euro cars was just a little bit higher (.8 v .85 bar max?) on the euro cars. There may even have been a bit of a difference with the ignition spec for the better euro gas but I do not know this. Thus, this may not be a perfect example of header opertunity on 930's.

However, when is comes to the 930 Euro style, SSI style, and 993 style, and B&B style HE's, if you adjust for equal boost delivery, I suspect there is not much difference in potential on a CIS 930.

I belive:

Header design with high lift cams on normally aspirated (NA) motors is important to potential.

Header design with low-overlap cams on NA motors is of moderate importance to potential. (SSI & 3.2 HE's make the same HP except at 3500rpm.)

Header design on a turbo car, that creates significant back pressure and is running low overlap cams, is of small importance to potential.

Muffler design is important to both turbos and NA motors potential.

Old 01-03-2009, 02:23 PM
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