[RETed]

Originally Posted by NoDOHC

I do not have means to monitor EGT at WOT. The headers were white hot on the dyno with the old ignition, but only over 6500 rpm, below that they were normal looking grey.

That sounds really too hot.
Is this a daily driver or a dedicated race car?

Why does advancing the timing increase the EGT? My experience would indicate that EGT goes down with advanced timing. Coolant temp and oil temp go up, but EGT goes down. (This is piston engine experience again...)

In my experience, EGT's will start to climb when you start to edge into early preignition.
Once you overly advance the ignition timing, then you start to get serious preignition which misfires and drops power drastically.

I made peak power at 38 degrees total advance last time on the dyno. There was about 4% improvement between 30 degrees and 38 degrees. This was with no hint of pre-ignition, 43 degrees lost power but did not cause any pre-ignition. I was running 8.2:1 polished rotors at that time.

My only recent experience with non-turbo application was a 20B in an FC.
I settled in at 30-degrees total advance.
I tried to edge the total advance to 35-degrees, but EGT's started to climb - sorry, I forgot the actual EGT #'s.
The set-up eventually settled at 232hp at the wheels on a DynoJet.
It did pick up about 5hp at 35-degrees, but EGT's were just too hot for my liking - this was a dual purpose track / daily driver, so reliability was a concern.
Stock 20B, no turbos, stock 20B intake, engine was never opened up - stock 9.0:1 rotors, restrictive cone filter, FC chassis, custom tube header into a 3" exhaust, Haltech E6K, no split on trailings, BUR9EQ's in all 6 positions

I never heard any pre-ignition on the dyno with 9.4:1 non-polished rotors before the seals failed in the front rotor either (although the AFR was so rich that I really shouldn't have worried about it anyway).

I tried running a higher octane fuel (89) and have not experienced any pre-ignition since. It might just have been that batch of fuel.

"Hear" preignition?
Not the real early preignition events...
On a dyno, you'll see it on the graph.

Side story...
I just got done tuning a customer's car a few weeks ago.
FC, built 13BT, 60-1 but O-trim turbine, HKS turbo exhaust manifold, 3" exhaust, eBay FMIC, Haltech E8, Walbro, 720 primary / 1600 secondary, BUR9EQ all 4 positions, Mallory Hy-Fire VIa on leadings
Wastegate was a Tial 44mm (I think) with a supposedly 10psi spring.
The car eventually put down 267 at the wheels on a Dynapack dyno.
Dynapack also indicated 11.5psi of boost, so it was slightly higher than the 10psi spring rate.
Anyways, I was trying to lean the fuel down more when it started to misfire.
We eventually figured out that the customer still had some old fuel left over in the tank...87 octane.
DOH.
We pulled the plugs, and the plugs still looked slightly rich for that boost level.
I knew I could still get some low-end power, but it just did not like it when I kept trimming the fuel maps down.
We came to the conclusion that it was just misfiring due to the low octane fuel it was trying to burn and trying to lean it too much.
The set-up put down almost a ruler flat torque line from around 3,800 RPM all the way to the 7k RPM redline - that surprised me because the O-trim is typically too small for a 13B.
I'm sure we'll start to see the power choke as we crank the boost up, but for now the owner is really happy for the results.
12psi of boost at around an estimate 300bhp at the flywheel is not bad for 87 octane pump gas...


-Ted