Anyone do any charting if Timing, RPM, Throttle Position (TP)? I' trying to figure out a couple of things and would like to compare notes. Here's some of my data points:

TP - RPM - Timing (3rd gear)
100% - 3000 - 21'
100% - 4000 - 6'
100% - 5000 - 9'
100% - 6000 - 14'
100% - 6600 - 23'

TP - RPM - Timing (4th gear)
100% - 5000 - 8'
100% - 6000 - 13'
100% - 6500 - 19'

The car feels a little sluggish in the mid RPM range and then goes like hell as the RPMs move up. Is my timing a little weak in the mid RPMs? I have not been doing an ECU reset when changing MAF's. Could this be an issue? I'm going to do a reset in the morning and see if it makes a difference.

 

wow how many mafs so far? with every one you car loses some of it's soul.

 

I think it's normal for the timing to pull back some near the torque peak. The ECU should adapt to the new MAF fairly quickly.

 

It's not the peak timing I'm worried about. It's the single digit MID RPMs I'm questioning.

 

Take the car to 6000 rpm in second gear and shift to 3rd, measuring the timing. You'll find that once the variocam has kicked in, it won't drop the timing like it does on the initial enagagement.

 

The cylinder pressures are highest at the (mid range) torque peak. With the high summer temperatures the ECU is probably using a conservative timing map. I think it's OK to have a dip in the timing curve around the same RPM as the torque peak.

 

The variocam goes to full advance at about 1100 RPM under full throttle.

 

Not true. It does not kick in full till almost 3000 rpm. Once engaged, it should stay lifted through your upshifts. Kicking in at slightly above idle would defeat the purpose of the variocam.

 

On this graph of the 996TT variocam operating system the engine torque at full throttle is on line D. Area 3 on the curve is full lift full cam advance. at full power above 1100 - 1200 RPM the engine operates in area 3.
The purpose of the variocam on the 996TT is not to improve full throttle low end torque. It makes the engine more efficient at part throttle and idle. Unlike the996TT the 997 TT and some 996 NA models have a continously variable intake cam timing, which may improve low RPM full throttle power. The 996TT cam timing has only 2 positions.

 

Here's a chart I created from an extended data log I made a few days ago. There seems to be a bid of a "dead zone" in the 3500 - 4500 RPM range. Do these timing numbers look correct?

 

Im no expert but form a basic look of things... your timing goes up as RPMs increase..... Im not sure what these cars should be running but in my evo Im doing 13 to 16 degrees max... too much timing causes things to POP. U add timing... u gain power.... but add too much and u break things... Also if ur up on the knock sensor then ur pulling timing again and again loss of power= not good.
maybe someone with serious understanding can make sense of it.
markski

 

From What I understand, the basic shape od the curve is correct. It's the degree to which timing is being pulled in the mid RPM range that I would like to compare with others who have done some data logging. I don't believe I'm getting into a detonation issue.

 

Any Ex-Purts wanna comment??

 

Lke I said earlier.....run a graph of timing and rpm at WOT going from a 2nd gear high rpm shift into 3rd gear. Let's see what the timing does then.

 

i don't know much about porsche engines...

that said, i'd say any timing in the single digits means something isn't right. that is seemingly *a lot* of timing to be pulled. some reasons for this might include:
- low octane gas
- bad gas
- very hot weather
- bad knock sensor
- faulty or incorrect measuring device
- and probably other things

as ebaker says, timing will be reduced during peak torque; however, single digits seems excessive.

- chuck