Burst Knock & Boost
Thread Starter
10 Second Club
iTrader: (4)
Joined: Feb 2004
Posts: 9,448
Likes: 0
From: Marysville, WA
Burst Knock & Boost Here's the situation - I have my timing set to 20* +/-2 in WOT power band, tuned it with HPTuner 1.7 on a dyno to make sure it was rich, not getting any KR, , etc, and I'm running 20% race gas mix at the track to make sure I get no detonation.
Anyway, now with 2.1 I see up to 8* of KR at launch, and it slowly decays thru the 1/4 mile, but the timing is locked at 18*. New math, 22 - 8 = 18?
I was thinking it was the IAT table, but again with 1.7 I couldn't read the IAT sensor. Now I can, and it stays well below the threshold.
I've been struggling this issue ever since I installed my new s/c'd stroker motor. And unitl I downloaded HPT 2.1x, I wasn't able to see where it was coming from. I think I found it last night. As I'm looking at all the data, I think I've narrowed it down to Burst Knock from Delta Air. Makes sense that a s/c would exceed the stock table setting for how fast the air flow increases. Tho I cannot find where anyone has teaked this table, or to what if they have.
And then I find what I believe is the other part of the puzzle. The Minimum Timing table. Low & behold it says 18* across the entire RPM range. So no matter what I set the timing to, or the KR level, it will have at least this much timing @ WOT. Almost sounds dangerous, since before with 1.7 I didn't even know this table was there.
So I'm thinking that tweaking the Delta Air cells would fix it. But what should I change it to for a boosted motor? There must be an equation. What's in there is for NA, so do I multiply the cells by 1.5 for 7 psi? And X 2 for 14 psi?
Any thoughts?
Mark
Anyway, now with 2.1 I see up to 8* of KR at launch, and it slowly decays thru the 1/4 mile, but the timing is locked at 18*. New math, 22 - 8 = 18?
I was thinking it was the IAT table, but again with 1.7 I couldn't read the IAT sensor. Now I can, and it stays well below the threshold.I've been struggling this issue ever since I installed my new s/c'd stroker motor. And unitl I downloaded HPT 2.1x, I wasn't able to see where it was coming from. I think I found it last night. As I'm looking at all the data, I think I've narrowed it down to Burst Knock from Delta Air. Makes sense that a s/c would exceed the stock table setting for how fast the air flow increases. Tho I cannot find where anyone has teaked this table, or to what if they have.
And then I find what I believe is the other part of the puzzle. The Minimum Timing table. Low & behold it says 18* across the entire RPM range. So no matter what I set the timing to, or the KR level, it will have at least this much timing @ WOT. Almost sounds dangerous, since before with 1.7 I didn't even know this table was there.
So I'm thinking that tweaking the Delta Air cells would fix it. But what should I change it to for a boosted motor? There must be an equation. What's in there is for NA, so do I multiply the cells by 1.5 for 7 psi? And X 2 for 14 psi?
Any thoughts?
Mark
Log your Dynamic Cylinder Air values; export to Excel and
make a new column vector where (say) column F is CylAir
logged and new column Q is =(F9-F8)/8 pasted down. This
is making you a delta CylAir on the same basis as the PCM
uses for the Burst Knock trigger threshold (presuming you
are at a 10/sec frame rate; the /8 factor is for the
12.5mS PCM main vs the 100mS scanner frame rate, use
/20 for 5/sec and /5 for a 20/sec, few-PIDs frame rate.
I recommend the latter as it will give you a little better
resolution especially about throttle-mash events.
Anyway, line-plot this new vector and look at what, and
where your peak positive values are, relative to the burst
knock threshold you have in place; then figure if you are
better off raising the threshold, or if it's been busy saving
your ***. That's where it gets "interesting" I expect.
make a new column vector where (say) column F is CylAir
logged and new column Q is =(F9-F8)/8 pasted down. This
is making you a delta CylAir on the same basis as the PCM
uses for the Burst Knock trigger threshold (presuming you
are at a 10/sec frame rate; the /8 factor is for the
12.5mS PCM main vs the 100mS scanner frame rate, use
/20 for 5/sec and /5 for a 20/sec, few-PIDs frame rate.
I recommend the latter as it will give you a little better
resolution especially about throttle-mash events.
Anyway, line-plot this new vector and look at what, and
where your peak positive values are, relative to the burst
knock threshold you have in place; then figure if you are
better off raising the threshold, or if it's been busy saving
your ***. That's where it gets "interesting" I expect.
Watch the burst knock PID in the scanner when you run it through the gears, it will probably be going nuts with the stock delta airflow table in there, fairly common with an F/I setup. Also change your minimum timing table back to stock or down to 10 or 0 or whatever you want it set to.
A year or so back the hot tip was to use the max retard
(whatever its name was/is) to clip the torque management
spark pullout. That may be why +18 or whatever is in there
(stock is -10, which sucks). I think I put mine to +10 but
refining the torque managamant retard vs reduction % is
where it's at, for TM.
(whatever its name was/is) to clip the torque management
spark pullout. That may be why +18 or whatever is in there
(stock is -10, which sucks). I think I put mine to +10 but
refining the torque managamant retard vs reduction % is
where it's at, for TM.
