Dyno with alky?

[SPOOLFOOL2]

Getting ready to tune the new motor on the dyno in a few weeks. Last time I dyno tuned, I was showing some KR on my Dirrect Scan in the very first part of the pulls do to (I'm guessing) the alky not coming up as fast as the engine rpms when the gas is matted from about a 45mph roll. I tryed turning the initial knob up to 1:30 but still had KR that took a good part of the run to compleatly go away. Someone recomended pushing the test button right before WOT, or just unplug the knock detector once I had a "good" tune on it. Figured that it's better to ask a stupid question, then to get stupid with the new motor.

Thanks Mike Barnard


On a side note: Car was running 22 lbs boost on 91 oct last time at the dyno. The guy that ran the thing had never had one of these cars on the rollers. After the first pull laid down 450 hp, he looked over at the data, looked at me, looked back at the data, and said "Huh, That can't be right!....(5 second pause and looks back at me grinning) Can it?

 

[GNVYUS 1]

What boost do you think it started knocking at?

I'd guess it's not cylinder pressure related since it's going to be hard to knock with low boost and 8:1 compression on 91 oct and alky starting at 6psi so I'd guess you probably have a false knock issue.

 

[Razor]

You need to look at airfuel data when making decisions. See if the air fuel is leaning out, then trying to correct the issue with alky is going about it in the wrong direction.

Dyno's and our cars on stock ecm's.. is questionable. The way the dyno loads the engine has a lot to do with it. And you'll find if you tune the car on the edge of being lean.. on the road it will get really lean.

The example is the MAF controls injector pulse width. If the MAF/Chip is not dead on.. meaning someone is there physically burning proms to dial in your monster... then you could very well have a lean condition coming up on boost. Then trying to fix this lean isse by flooding it with alky .. I hope you see the point.

You use alky to suppress detonation, not fix a fueling issue. This is the law

Not to mention the knock could very well be false.

On cars with stock ecm's i've never had great results on dyno's.. unlike cars with aftermarket ECM(FAST, BS3, Gen7) Those you need to have a dyno to get you into the ballpark.

Put the car on the track and do some low boost datalogging(powerlogger, directscan,etc).. once that looks correct.. start turning up the boost.. and work with your chip maker to dial it in 100%. Understand every engine is different, and there is no chip that 100% first shot drops in and is 100% perfect. Having gone through 100's of different chip images.. I know this.