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911st 911st is offline
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Join Date: Jan 2004
Location: Sacramento
Posts: 7,269
Originally Posted by Cobalt View Post
As others said for not being an expert you have sure done a ton of research. There is always so much more to learn.

I have gone over this multiple times with some local shops I have complete faith in and they don't seem to have the concerns that you do about the 964 but totally agree about the 930's. One shop in particular does primarily turbos and have built some serious cars.

I totally agree with the AFR's on the 3.3 and how he survived a season let alone a week with those numbers I have no idea. I would have expected the car to have detonated long ago. Although he might have made adjustments later he never noted them to me. I only posted that chart to show that higher numbers can be achieved although I agree it is way to lean for my comfort zone. But when you think he is getting nearly 535BHP out of a 3.3 on CIS is just crazy but apparently doable although highly risky if not bordering on stupidity.

IIRC after speaking to Stephen at IA some 4-5 years ago, he also felt that the 964 could flow more fuel than the 930 although recommends the fuel head mod. He supplied me with the spring when I purchased the HF K27. All I can go by are the readings I get from my gauges and dyno charts. David's (C2turbo) Inyourfacegauges are very accurate and my AFR's look much different than the 3.3l I posted. .

I don't have the charts on this PC to post otherwise I would, but the readings are similar to the ones for the other 3.6T I posted. Here is the chart of the AFR's and torque. I would be curious to your opinion of these numbers but I think they are relatively consistent with what I want to see to be safe. The problem with the CIS is there is no way to flatten the curve and are limited by how the system is functioning and must make compromises. Although as you can see this particular 3.6 T is making just over 445bhp. I do know this motor did die eventually after many track hours although from what I was told it was a mechanical failure and had nothing to do with fueling issues.

Typical boosted CIS fuel curve. With the triggering of boost enrichment it first goes to rich untill the metering plate stalls out. Then the motor has to increass rpm enough to use up the to much fuel to get the AFR's back to something that makes sense. Would be more fun to run a boost controller that would boost higher at low rpms and pull back as the fuel runs out.

A factory stock C2 Turbo's AFR curve is a beautfull thing and near perfict bot pre- and post-boost to red line. Once we turn up the boost the metering plate gets out of the area where the cone around it is calibrated to air flow expectation. It dose not travel very far before it starts to stall. I wonder if the 3.6 made some changes in the cone area.

That cone around the metering plate is like the rpm by air flow map on EFI, or a space cam on MFI. Change the air flow expectations and ya get our of wack.

If I was running a CIS turbo on the track, I would want AFR and EGT readings. Running some race fuel is also a must on a track turbo from what I hear. Again, anyone that runs a CIS turbo on the track without a EGT is playing about $10k or more worth of chicken.

If you have tested your AFR's with a wide band and are and they are good, that is great. I am supprized if it can support 450fwhp with out some fueling help above 5k.

Stephen was a help in my being able to learn about CIS. I used to frequent a Turbo board where we used to hang out and play what if. I am thinking your may have been there to. Back then he and others thought the USA head, lines, and injectors were a limitation and the euro head was the thing. I did not belive this as the cross section of the USA lines though smaller than the euro, still where plenty large for to deliver more than enough fuel with fuel pressure delivery an the spraying full time like CIS dose.

With the IA head came disabling the Lambda function by closing the internal passage and in effect making the USA heads euro heads. I am not a big fan of this as it kills the Lamda function and cold start function on a C2T.

Most do not know this but there even more fuel flow is available from a stock USA head than the IA head by ensuring full travel of the metering plate at upper air flows and playing with the lambda frequency valve which can do the same thing as recalabrating the the euro head dose.

Thinking back to somthing you said earlyer. It sounds like you might be getting a little boost creep with your HF. Though it seems a very acceptable level. This is best watched under full throtle in a higher gear.

Old 02-27-2009, 12:20 PM
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