Big pump blues. Too much fuel = knock Options

[AWD DSM 1]

A set of 550's and some kind of fuel tuning was next on the list when I had it. It's hard to do much without a way to adjust the fuel settings in some way. Honestly, there are a million things that you could do that might help and might not. I guess you need to start buying parts and find out!!

[awd4kicks]

It feels rich when I'm riding in it, but after your experiment I would tend to think the opposite.

The Blaha is supposed to make the ECU think the incoming air is very cold, but this is really to avoid over running the MAF and causing fuel cut. The MAF is going to read a certain amount of air no matter what, and with the Blaha your actually sucking in a ton more unmetered air the ECU doesn't know about which should really lean it out. For instance if you didn't have the flapper door on the Blaha it wouldn't idle for crap when it's cold, but when you block some of the air the car runs better with the reduced air and fatter mixture.

This sounds like a good spot for Nate to go engineer on us...

[natedogg]

Notedugg, DS&M tOOninG eNjinEar heAr.

I agree with Marcus. While running too rich can cause knock, that doesn't seem to be your problem. Consider that we turned the boost up and saw more knock. That means one of two things A. you are running too lean at WOT or B. you are heat soaking the IC (less likely considering the cold temps the night we were logging.)

Seeing black smoke between shifts is normal for modded DSM's because as you get off the throttle the turbo is still spooling and sucking a lot of air in through the MAF but the throttle plate is closed, so the loads of metered air never makes it to the combustion chamber. Nevertheless, the engine is still supplying enough fuel for all the air the MAF just metered, hence richness and black smoke out the tailpipe.

Anyway, in its current state of tune your GSX feels very strong to me. Stronger than the GST IMHO. Plus, consider the GST got taken from a roll by the GSX. An AFPR and a 16g wouldn't hurt though.

As for the Blaha causing extra knock, I can only theorize this. At the same boost pressure on the 14b turbo you will be flowing the same amount of air whether running the Blaha or not. The difference comes in that the Blaha doesn't count as much air as the stock MAF so it causes less fuel to be supplied even with the cold temp sensor resistor in there. This is how it gets around fuel cut. So basically with the Blaha you were flowing the same amount of air but less fuel, which causes leaner mixtures, and more knock.

Since you are not hitting fuel cut with the stock MAF, I'd ride it out for now. But if you do decide to upgrade to a 16g you will most likely have to upgrade your MAF as well. I was running stock injectors, stock fuel pump, and stock fpr when the 16g was on my black wreck and it ran great at 17 psi of boost, but I was running a Blaha MAF. That may work for your car or it may not. Maybe I was lucky. You may have to upgrade to 550's and a fuel controller of some sort considering the knock you are getting with the 14b and the Blaha MAF. Course there are other routes to take as well: like a 2G MAF and an SAFC or a GM MAFT. Your call buddy.

[awdnot2]

Don't know if this means much, but I had a combo that worked well back in the day.

Non-turbo FPR (10 psi more fuel pressure)
MAS (NO Honeycombs at all)
450 cc
HK$ FCD(Fuel Cut Defencer) It limits the Frequency based on rpms. It will lean the car out some. I have one available if you'd like to try it. Its wired to plug right into your car Dan.
Upgraded fuel pump. Not the big ones that are available now.
14b unported
IC pipe
Archer Racing SS tubular manifold (some called a header_
HKS 2 1/3 inch exhaust, stock DP

This was good for a 12.98@104. Unfornately I do not have any data other than O2 voltage.

If your current setup seems a little rich the Fuel Cut Defencer my be right up your alley.


Darryl

[natedogg]

MAS (NO Honeycombs at all)

We found this to be a problem when we first logged Rob's car right before we bought it. The turbulent, non straightened air (due to no upper honeycomb) flowing through the MAF was getting counted then recounted and causing a very erratic airflow signal and injector DC signal on the logger. This caused a lot of knock. We replaced it with another MAF with just the lower honeycomb removed. This got rid of almost all the knock and the car pulled quite a bit harder.

[awdnot2]

Yes I understand the the upper honeycomb can casue problems, but if too much fuel is there which was my case removing the upper raised my fuel cut because the car ran leaner due to air getting into the motor that the MAS didn't know about. I don't advise this, but with the right combo it may work.

The 12.98 runs were with 5 gallons of 108 added to 1/4 tank of pump 93. The boost was at 18-19psi peak.


Darryl

[AWD DSM 1]

Dan, If you take that car out and run a 12.X with it I'm going to bomb your house....

[AWD DSM 1]

Fire bomb, shrapnel, or just high explosive?

I was thinking more along the lines of a stink bomb...