Tuning issues

gt90stang · 07-06-2007, 01:44 PM

Hi all,

Been busy but finally got a little time to tune. I’ve been fighting a over 4500 RPM detonation problem at full throttle in 1st gear only. I tried TTNOV pulling timing and it worked but performance really suffered so it wasn’t acceptable. The most timing I could run in the WOT spark advance vs RPM function was 21*, but I still got detonation over 4500 RPM in first gear.

I got to thinking about what was going on, looking over the datalogs and nothing made much sense (looked ok). So I decided to back up a bit and remove the tweak I did to the spark advance rate vs RPM function. When I originally did this my thinking was to allow the PCM to remove timing faster.

The spark advance rate vs RPM function settings I was using:
0, 0.5 992, 0.5 3008, 0.375 4000, 0.125 8160, 0.125

Versus the original of:
0, 2 0, 2 992, 2 3008, 1.5 4000, 1 8160, 1

So basically 4 to 8 times faster advance rate than stock. So when I went back to the original spark advance rate vs RPM function I am now able to run 23* in the WOT spark advance vs RPM function with no detonation. All I can think of is that the PCM can’t deal with the higher slew rates of the modified spark advance rate vs RPM function. Datalogs before and after these changes are virtually identical. Anybody have any insight here?

Gt90stang, Don

Engine: 306 ci w/ timing at 10*, Sterling pistons H273CP w/8.9:1 compression, FMS Harmonic balancer, Edelbrock 6037 heads w/2.02" intake valves, Explorer lower intake manifold (GT-40), FMS 1.6 roller rockers, Crane 444221 (2030) 216/220 @ 0.05" with 112 lobe separation 0.533"/0.544" lift, Ron Davis aluminum radiator, Lincoln Mark VIII electric fan, 130G alternator Tweecer RT, Performance Distributor TFI module & Scream’n Demon Coil, Denso Iridium Spark Plugs IK-20, FMS oil cooler.

Fuel and Air: KenneBell Blowzilla @ 8psi with a 10# pulley, 42# FMS injectors, Edelbrock 70mm TB, C&L 76mm MAF, Stock fuel pressure regulator, 190 lph fuel pump, Stock airbox w/ K&N filter (silencer removed), 91 Octane Fuel.

Exhaust: 1 5/8" JBA Titanium ceramic coated shorty headers, MagnaFlow SS 2 1/2” catback and X-pipe w/Cats.

Drive Train: D&P Products 2500 RPM stall 9 1/2” torque converter w/damper, AOD w/ TransGo HP shiftkit, Earl’s 19 row transmission cooler, FMS 3.73 gears.

Wheels and Tires: 17” x 9” Replica Cobra R, 555 Nitto Drag Radials 275/40ZR17 rear & 555 Nitto 255/40ZR17 front.

Brakes: Front 73mm calipers from 1991 Lincoln Mark VII, Sn95 MC w/3-2 port conversion & Russell SS hoses, adj. Proportioning Valve in series with the stock Combo Valve.

Chassis: FMS Subframe connectors, Energy Suspension engine, transmission and front sway bar mounts.

07-06-2007, 01:44 PM	#1
gt90stang Member Join Date: Aug 2005 Posts: 72	Tuning issues Hi all, Been busy but finally got a little time to tune. I’ve been fighting a over 4500 RPM detonation problem at full throttle in 1st gear only. I tried TTNOV pulling timing and it worked but performance really suffered so it wasn’t acceptable. The most timing I could run in the WOT spark advance vs RPM function was 21, but I still got detonation over 4500 RPM in first gear. I got to thinking about what was going on, looking over the datalogs and nothing made much sense (looked ok). So I decided to back up a bit and remove the tweak I did to the spark advance rate vs RPM function. When I originally did this my thinking was to allow the PCM to remove timing faster. The spark advance rate vs RPM function settings I was using: 0, 0.5 992, 0.5 3008, 0.375 4000, 0.125 8160, 0.125 Versus the original of: 0, 2 0, 2 992, 2 3008, 1.5 4000, 1 8160, 1 So basically 4 to 8 times faster advance rate than stock. So when I went back to the original spark advance rate vs RPM function I am now able to run 23 in the WOT spark advance vs RPM function with no detonation. All I can think of is that the PCM can’t deal with the higher slew rates of the modified spark advance rate vs RPM function. Datalogs before and after these changes are virtually identical. Anybody have any insight here? Gt90stang, Don Engine: 306 ci w/ timing at 10*, Sterling pistons H273CP w/8.9:1 compression, FMS Harmonic balancer, Edelbrock 6037 heads w/2.02" intake valves, Explorer lower intake manifold (GT-40), FMS 1.6 roller rockers, Crane 444221 (2030) 216/220 @ 0.05" with 112 lobe separation 0.533"/0.544" lift, Ron Davis aluminum radiator, Lincoln Mark VIII electric fan, 130G alternator Tweecer RT, Performance Distributor TFI module & Scream’n Demon Coil, Denso Iridium Spark Plugs IK-20, FMS oil cooler. Fuel and Air: KenneBell Blowzilla @ 8psi with a 10# pulley, 42# FMS injectors, Edelbrock 70mm TB, C&L 76mm MAF, Stock fuel pressure regulator, 190 lph fuel pump, Stock airbox w/ K&N filter (silencer removed), 91 Octane Fuel. Exhaust: 1 5/8" JBA Titanium ceramic coated shorty headers, MagnaFlow SS 2 1/2” catback and X-pipe w/Cats. Drive Train: D&P Products 2500 RPM stall 9 1/2” torque converter w/damper, AOD w/ TransGo HP shiftkit, Earl’s 19 row transmission cooler, FMS 3.73 gears. Wheels and Tires: 17” x 9” Replica Cobra R, 555 Nitto Drag Radials 275/40ZR17 rear & 555 Nitto 255/40ZR17 front. Brakes: Front 73mm calipers from 1991 Lincoln Mark VII, Sn95 MC w/3-2 port conversion & Russell SS hoses, adj. Proportioning Valve in series with the stock Combo Valve. Chassis: FMS Subframe connectors, Energy Suspension engine, transmission and front sway bar mounts.