Can the unorthrodox underdrive crank pulley cause a knock sensor to go off and retard timing, because a harmonic disbalance.

Thanks Glen

 

no

 

well said

 

Any chance of getting a more in-depth answer to this? This is something I've been wondering as well.

At a recent drag strip meet, my car w/ Stillen intake, Z-tube, Crawford plenum, UR pulley was consistently beat by .2 sec in the 1/4 by a stock vehicle. Watching closely during the race, we are pretty much dead even, save for the last 1/16 mile where he actually pulls on me. This should not happen with my mods. Wondering if somthing is causing timing to be pulled under load in 3rd gear (AT)?

 

Was the other car a 6MT? if so that can more than make up the diff.

 

IIRC, the central point of the argument that U/R pulleys (or underdrive pulleys in general) are bad for your engine stems from harmonic balancing... but... the VQ35DE is an internally balanced engine, therefore it does not require a certain size/shape/weight of a crank pulley to balance the engine (if it did, this would be an externally balanced engine)

there are tons of thread around here, so you may want to use the search function to get a ridiculously detailed idea of the "problem" and the refutation of that argument

 

No, it was AT as well.

 

Yes, I've read them. Just can't figure out how I seem to be loosing power under load in 3rd gear.

 

With the Crawford Plenum and a Catback you can be running leaner than stock and that can cause the ECU to pull extra timing due to extra knock. To get the full benefit out of these mods you need a reflash to restore your A/F or maybe run a higher grade fuel. I have the Crawford , CATs and TD and have noted this to be the case via an OBD2 analysis probe..

 

Only one way to find out. Use an OBD-II scanner and monitor ignition timing and RPM in all driving conditions w/ and w/o a pulley.

Michael.

 

I don't have a cat-back; only Stillen intake/Z-tube, plenum and UR pulley. I only run 93 octane. I tried having my timing advanced 2 deg and G-tech indicated it gave me .15 sec gain in 0-60, but nothing in 1/4 mile. I have since had it reset to stock. From info. I have read and been told by Crawford, thee mods should not put me so lean as to cause knock/timing retard.

 

I'm going to try to get my tech to ride with me and make a few runs with the ConsultII hooked up to see if timing is being pulled. I guess he can monitor the A/F as well?

 

I did hook my car up to a ignition timing machine, and at high rpms the timing was getting pulled back. The only problem is is it from the head component upgrade i have or the unorthrodox pulley. But i recall once i installed the crank pulley my car burnt out more right away, and over a few start ups it started to decrease. The only way to find out is to in fact try the factory pulley, and the unorthrodox one on a ignition timing system. The main culprit to the timing loss is the knock sensor what we need to know is how sensitive this sensor is? Im fed up with the dam thing retarding my timing so im having it deleted from my program. All the race motors people have dont have that sensor. I guess im gonna find out the hard way. If the sensor protects the car or not. I feel the louder the motor over factory spec the more that knock sensor is gonna pick up vibrations.

Lets hope ill be fine without it!!!!

Thanks Glen

 

Great, so now we're back where we started. So the pulley (stock or otherwise) is not dampened, but the stock one has a noise suppressing ring. This mean that the UR pulley may be causing additional noise that the knock sensors are picking up and thereby retarding the timing (totally different issue than the pulley potentially being bad for the engine).

The other possibility is that my mods are causing a lean condition, causing knock, retarding timing. I tend to think this is not the case. If it was, timing would be retarded from the start under WOT or at least as I approach redline in each gear. I only seem to be losing power under load in 3rd gear toward the end of the 1/4.

 

The more I think about it, the more I'm convinced that if timing is being pulled (which it would seem to be), that the pulley IS the most likely culprit. If it was anything having to do with A/f, timng would be pulled all the time from the start, or at least in the same rev range in each gear. I only appear to be losing power in 3rd gear under load as RPMs rise, toward the end of the 1/4. If "noise" from the pulley is causing it, it may be bacause at that particular load/rpm, the noise is at such a point so as to set off the knock sensors and pull timing.

If this IS the case, then this would also negate any gains that the timing advance had in the 1/4 mile, but not affect 0-60 times, which could explain why I saw a .15 gain in 0-60 with the timing advance, but no difference in the 1/4 mile.

We may be getting somewhere!

Next step: Have my tech monitor for timing being pulled, yank the pulley if it is, then re-test timing advance.

Big question is: do I get timing pulled under normal driving conditions or only at WOT runs to high speed? If not, I would have to decide if the one occasional negative outweighs the benefits of the pulley (few extra ponies and more low TQ and quicker revs). I don't drag race much at all in normal driving and rarely even hit it at WOT.

 

I agree i have power until high rpms thats when my timing is getting pulled.

 

I have logged nearly 50 hours on my car with the pulley on and off...no change in timing whatsoever

I have witnessed Z's with very few mods (fewest was intake and exhaust, period), run mid 13's at the strip...insanely quick compared to what most NA modded cars (ecu, test pipes, etc) run. Different cars, different build dates, etc - sometimes people just get exceptionally strong runners!

The sensors on most cars are very sensitive, which is how they should be for a street driven car on pump gas. If the car is tuned properly, there is absolutely NO reason that the knock sensor should be picking anything up other than actual knock. One of my own cars has solid lifters, and a valvetrain/cam package that is 100% custom. it was all assembled by hand to very tight tolerances, and the ecu I run can enable or disable the knock sensor. If you log a series of runs, regardless of the gear, the knock sensor picks up absolutely nothing. Keep in mind this car is an inline 6, and as such has a much noiser valvetrain than any v series motor I have ever heard.

My guess is 2 fold - either something is up wiht the tolerances your head was put together too (I'd samy that's remote but still a possible cause), you somehow damaged your knock sensor during disassembly or reassebly, or 3, your timing or fuel curves are too aggressive.

The only way you are going to know what is going on is to get a datalogger and start testing..without that you are literally looking for a needle in a haystack

Adam

 

Your correct their must be a reason for the knock sensor going off. Hopefully i can figure it out soon.

Thanks Glen

 

Zmego - try to borrow a datalogger from someone to do some testing...at least you can spot exactly where the timing is being pulled, and what else is happening at that exact moment in time (fuel trim wise, tps wise, maf signal wise, etc)

 

Ill have the dyno do this with their datalogger. When they did this before my timing at a idle is 28 degrees as the rpms increase timing starts to decrease. At wide open throttle at 7000 rpms my timing is 10 degrees.

Thanks Glen