Silver7even

Hello, I just installed a PFC w/ commander in the 93FD. It is running fantastic. However I am getting a high knock detection as boost is coming down. I have drawn a picture (see knockboost.JPG attached). I only see this spike when I don’t shift at the end of the boost period, if I do shift, I don't see this. Any ideas on what’s going on, or if this is just blow off noise or something?

Thanks
George

Silver Touring 93; ported, ceramic seals , medium Greddy intercooler, down pipe, Boenz cat, M2 cat back, Pettit ceramic twin turbo, M2 intake, Racing beat springs in rear, R1 springs in front, Tokico adj shocks, 18" P Zero Corsa, new Power FC & commander, waiting shipment of Datalogit

rynberg

You can ignore knock readings during any kind of off throttle or shift events. It's just a microphone, so it can give high readings from drivetrain noise in general. The knock readings are only useful during constant steady throttle.

cewrx7r1

iTrader: (2)

If you look at the upper right hand quadrant of your timing maps, you will see it going into the 40s and 50s. If you rev high and get off the throttle without shifting, it will fall through this area. Some engines give high knock/noise values here.

You can change both the IGL/IGT for this area so that the max IGL is 38 and this should help. Be sure to keep split in range.

Silver7even

how does this map change look? (see attached .xls) I noticed there was 0 split in the upper right area.

cewrx7r1

iTrader: (2)

No stock map has 0 split.
Best to not run it even off boost to insure that the leading fires first.
Negative split is not good, and is very bad under boost.
But both show up on some PFC maps!
You need to add a split calculation to your EXCEL worksheet.
I have it but did not add it to my attachment below.

I actually run less split than what I gave you, but this is very safe under boost and has better throttle responce.

Silver7even

Thanks for the .xls

Would a flat -3 correction be OK for calculating IGT from IGL? or is there a preferd profile? I am looking for low end drivability.

cewrx7r1

iTrader: (2)

Do some re-search on timing. Think about two flame fronts burning towards each other which increases the speed of pressure buildup in the chamber and reduces the time to burn the air/fuel mixture. What is pressure build up that happens too fast? Too little split can cause the same affect.

Spit of 3 is fine for idle, cruise, and low boost up to about 2psi than start increasing it up to 8 by 6psi boost. I run 10 split up to my overboost safety row then go to 15. Most common high boost split is 15 down to 8.

Silver7even

As cewrx7r1 suggested, retarding the timming along the top of the map, from middle to right, and using proper split, eliminated the knock. Thanks

Lynn Bordes

Good call Chuck.
Barry