Thread: Fuel enrichment
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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269

I do not believe the problem with the K27-7200 is it going out of the compressor efficiency range at 1 bar or going postal and overly heating the charge air.

Before that happens the turbine hot side chokes and limits the compressor sides potential.

The key to running a 7200 seems to be on the hot side and making the exhaust work as well as possible.

Note how well it responds to Brian's equal length headers and an open muffler. My point of reference is on my car I switch from a B&B muffler to a straight through Borla muffler I built and picked up 30hp on the dyno. It just dose not seem to make sense that headers or a muffler change could make that much differance.

In further support of my thought on this, the 7200's compressor is probably more modern and more capable than the K27-7006. However the 7006 makes more HP. This seems to be due to its larger flow hot side which dose not choke as soon and also makes for less exhaust reversion at the same boost levels.

As another point of reference, on my car, which was kind of out there for CIS (cams, ports, euro injectors and lines, larger bar and plate re-core of my C2 intercooler, custom programmable WUR/fueler, headers...), all a 1 bar spring did was fill in my mid range some. Even with a EBC and Tial trying there best to pull 1 bar I could not maintain even .9 bar at HP peak on a load dyno.

In the end I preferred the K27-7200's kick over my K29 and HF prototype which both had a bigger top end. Not that it was better, it just suited my in town and back road driving style better. As a side benifit, at full boost and with control pressure lowered as far as possable I was able to maintain 12.2/1 AFR to 6700rpm. With the K29 an addational injector was needed to keep the AFR's in line (not suggested).

In fact I kind of suspect the larger turbos that can achieve and hold more boost at higher rpm might even make for more of a need for improved intercooler capacity than the 7200 now that I think of it.

I guess I do not believe running a 7200 at 1 bar puts a CIS turbo and any more risk than a larger turbo at 1 bar. It is actually probably safer if anything as it limits boost to keep the motor withing the fuelling limits of the stock CIS system.

Thus, I whole still would not run 1 bar without an intercooler upgrade and I have no issue with running a K27-7200 at 1 bar.

But, that is just my opinion.

Last edited by 911st; 08-22-2010 at 08:30 PM..
Old 08-22-2010, 07:27 PM
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