333pg333

'In Helmets, no one can hear you scream'
er I mean I couldn't hear the car pinging it's head off (or trying to anyway) that time on the track when the Tial jammed shut and the car boosted to 2.1 bar. I did notice it after a while and we tried to fix it trackside if you remember. The other time was when that vacuum hose came off and the car was feeling really quite nice and it was also boosting to 2 bar, but on the E85 there was no sign of any pinging whatsoever.
I quite like 30psi though if you could arrange that on a regular basis.
Anyway this is why I've always wondered just how this boost/timing cut is meant to come in??

special tool

Jim - of course noone (who knows what they are talking about) will be able to answer this obtuse question.
There are too many variables: what is ambient temp., what is IAT, what is cylinder head temp., etc.
I could give you a ball-park answer based on actual experience, but I won't endure being questioned by the children on this forum who have doubted me in the past based on......nothing???

Obviously checking for knock in low-load gears as 1st and second is ridiculous, and a waste of your time.

A timing light works very well on a 944, but you must first establish that the software is a proper match. In other words, you must use an afm chip on an afm car and a true maf chip on an maf car. (I will not elaborate on this because I have revisited the theme already excessively).
If your timing is skewed incorrectly, the timing light test is moot.

I have read many of your postings, so I will assume your chip is properly matched to your mechanicals.

Please elaborate on what led you down the "timing" route.

333pg333

Those doubting Thomas'.

special tool

I heard ALL about YOU.......

333pg333

Now now, no telling tales out of School.
Back to the plot, how have I had a couple of bouts of 30psi and not felt any retardation at all. Pinging or no Pinging?

TurboTommy

I would think: Unless you have a fancy engine management that automatically retards ignition as boost increases, your ignition advance would have been set to the boost level you run under normal circumstances (lower than 30 psi). If your KLR wants to cut timing because of the unexpected 30 psi boost, it wouldn't bring timing (OP said 6 degrees) down below much more than where you would experience power drop off, anyway (at that high boost level).

Realy good info on timing vs power is hard to come by.

Oddjob

Have a car that has had a low power problem for some time. Pretty much stock K26/8 car, chipped (have used various chips) running approx 15 psi. Last fall I dyno’d the car back to back with my other car – and it pulled 17 rwhp less when running 0.5 – 1.0 psi higher boost. Over time I have swapped/changed pretty much everything (chips, DME/KLR, WG, TPS, knock sensor, Turbo, injectors, fuel pump, FPR, AFM, coil, plugs, wires, etc, etc) to include rebuilding the engine (still fresh w/ exc. leakdown #s).

The original onset of the problem and the engine’s “feel” keep me coming back and looking for some sort of electrical/sensor/ignition problem - which is why I have put some more thought and effort into the knock system. If there was a problem with the knock sensor wiring, the KLR/DME might be retarding the timing, which might account for the power loss.

Tried unplugging the knock sensor (which I assumed would pull –6 deg) and also tried using the FQS to pull –3 deg (while the sensor was plugged in), and I could not feel a seat of the pants difference when testing on the street. I did this test on both cars with the same result, or lack of. So just trying to make sense of that; my post was just to get a ballpark feel for how much power might be lost if the timing is retarded by –3 and –6 deg (or the effect on the torque curve). Aftermarket DME chips can pickup 10-15+ hp by advancing the timing over stock, but I dont know how much advance they are adding.

By the way, anyone know what the resistance of pin 12 (Ground, Knock Sensor Shield) on the KLR should be?

Will still do a little more screwing around with this before throwing in the towel. But as this troubleshooting path turns into a dead end, Im not sure what other systems to go back and check again (mechanical, electrical, etc).

Oddjob

Sean, I have the little curtis event counter and it does indicate a few knock counts every full boost run, even on the street. And as would be expected, when the knock sensor is unplugged it does not register any.

I have thought of dyno’ing the car with a timing light hooked up to measure full load timing. But I do not know the chip timing maps to compare, and even if I did, I am not certain of a timing light's +/- accuracy. I could put another car on the dyno to compare timing #s to the other car running the same chips – that would probably be the most conclusive in determining if the weaker car is pulling timing.

Just doing some homework before taking the time and spending the money to get two cars over to a dyno shop.

JET951

Hi Jim
Thats just what i was going to suggest. lucky enough for you that you have a few 951's to trade and compare parts. i know this is out of left field but none the less, are there to resistance with the 951 with less HP, for instance is one of the rear calipers binding. i know its a long shot but everything is worth looking at. is the valve timing the same between the 2 cars? could one of the cars have a different cam to the other?

fast951

Oddjob, Any chance the ref sensor is not in the correct location? Can you check your ignition with a timing light (at idle)? At least you can eliminate the ref sensor being off.
Too bad you don't live closer, I can check if the KLR is pulling timing in no time.

Oddjob

Fairly certain the cams are all stock. The weak car has had two different engines in it, to include the heads and cam towers. The strong car is not special, it makes similar power to another 89T I previously owned, so its not unusually "hot". I have double checked cam timing. I dont think the clutch is slipping. Brake pad wear does not indicate that the rears are hanging up. I would think any torque tube and trans bearings that were bad enough to decrease rwhp would be howling/screaming loud. The torque/hp curve from the dyno doesnt look odd, the shape is what you would expect, just 8-10% low. I would think any driveline mechanical problem (slipping clutch, excessive friction, etc) would likely show up in the torque curves, right?



I did check the no-load timing at idle and 2500rpm last year. From old notes: with Cup/Escort chips, the timing was 8 deg at idle and 41 deg at 2500. With APE chips: 7 deg idle, 53 deg @ 2500. The stronger car was about 6 deg at idle and 48 at 2500 with the APE chips. I attributed the 5 deg difference between the two cars with the APE chips to the timing light accuracy, tach variation, and the difficulty of holding exactly 2500 rpm. Those numbers sound ballpark?

I have not done the oscilliscope tests per the factory manual to check the ref. sensor signals to the DME. But I have replaced the sensors and the gap has been checked a couple times when I replaced the clutch and then again when I swapped the clutch/bellhousing onto the replacement engine. There has been at least two flywheels on the car too.

Unfortunately that would be a long drive from MN, but I appreciate the offer.

fast951

Not having the data off of the chips you tested with, I cannot be 100% accurate on my guess. However I'm yet to see idle ignition modified, so I assume they are using the factory idle timing. Based on this, you are not off at idle (well maybe a couple of degrees, but this varies with the idle RPM).

The part throttle is not possible for me to guess, as the PT tables are usually modified so I have no base to compare with your results.

If you were to use the factory stock chip for the same test I can guess a bit better.

I'm not concerned with the ref signal making it to the DME, we know it is. However if the set screw on the flywheel is off by 2 teeth, your timing will be off by approx 6 degrees. Based on the idle data, the ref sensor is fine.

Ideally you want to set the timing on the chip for a static well known value (not as simple as it sounds), then check against a timing light. This will indicate if the KLR is pulling timing.

Oddjob

John,

Pretty much semantics, but the KLR, thru the DME, actually retards timing (say -6) from a base ignition map if it detects something wrong (knock or some other system failure-limp mode), correct? Versus - it doesnt advance the timing 6 deg from a base map, if all system diagnostics are ok and no knock detected?

In limp mode and/or knock detection, I dont think timing is retarded throughout the entire rev range and all throttle positions, right? Is it retarded just at full load, or is it something like throttle postions above 50%?

fast951

Jim, The KLR retards up to 6deg when it thinks it's required. It does not advance the timing over the base!

TurboTommy

This is a good question. I wondered about this myself.