Hi guys, I have a 5 spd manual trans behind my MAF HSR'd 6E 327. I have 58cc 305 HO heads on it right now, which gives me 9.6:1 static CR with the flat top pistons. I have a 232@0.05 108 LSA cam. I have total timing at 30 right now at WOT, with no PE spark adder. I have been backing the timing down from 36 WOT down to 30 and still see 3-4 degrees knock retard when shifting gears in the 3000-4500 range. Ie, the knock comes in immediately after a WOT gear change when I get back into the throttle (I get 2 knock counts and just about 4 degrees KR gets pulled and then immediately ramped back in).

The only irregularity I see is that I have 140ish integrators right before PE kicks in-- I know my AE is lean because the huge plenum of the stealth ram requires more AE fuel than I currently have added. Could lean AE cause enough leanness to start a preignition event even when stomping the gas, which would be mostly PE dominated? I suppose I might not have enough PE fuel, although the NB is up in the 800-900 range under WOT. I am around 20% PE fuel in the 3000-4500 range.

I think the 305's with the 416/081 heads were running 35-36 total timing, although they probably had 9:1 compression instead of my nearly 10:1. Could my 10 points (1.0) compression gain from the 305 really require 6 degrees less total timing, even though I am running premium 93 fuel, or should I be looking for mechanical interference (ie exhaust hitting the floorboard) triggering knock? The only reason I begin to suspect this is that the KR is consistently only when getting hard back on the gas when banging gears.

 

I don't know the complete dynamics when shifting gears, but I usually got a few degrees of timing retard/knock when shifting the auto TH-350. I never cared because losing 2-3 degrees is like losing almost zero HP for a few hundred milliseconds.

 

There could be two things that I can think of. First would be gear noise from the shift. This is cause by the slack in the drivetrain being taken up. The knock sensor picks it up and retards the timing.

The second being caused transport delay for fuel while the PE SA is immediate. This is because the PE SA can be commanded back in immediately while there is a lag before the fuel arrives.

For the fuel lag issue, try to make as much of the AE delta TPS% commanded. This is added in as async pulses which lowers the transport delay.

Some ECMs have the capability to attack in or delay PE SA. If the mask you are running can do this then slow down how quickly the PE SA comes in. This gives the fuel a chance to arrive.

To discover if it is false knock from someting hitting, or drivetrain noise, pull the plugs and look for signs of detonation.

RBob.

 

Thanks guys! I think it is drivetrain slack, because I am looking at datalogs from back when I had 7.8:1 compression and what do you know, I still had 4 degrees retard under hard shifts. Oh well I guess I'll just live with it. I hadn't thought of that but it makes sense. The T5 has all new gears but the rear in this car has some slack in it, which you do feel banging gears. I have zeroed out PE SA so that isn't it.

 

Yes, you may have an AE problem.
And you might look at the Burst Knock Retard settings you have, and try tinkering with them.