# Root cause of timing pull discovered!



## Currancchs (Feb 24, 2011)

Well, I think at least, seems to be backed up by logs so far, maybe coincidental though... So, I have had what I always thought was a bit too much timing pull since purchasing my 2001 225Q a bit over a year ago now. Stock I had about 3 degrees of pull, and GIAC was pulling about 10 degrees, APR pulled ~8 degrees! I fiddled with the wastegate (reduced preload), changed out N75 back to stock, etc. but nothing seemed to make a large difference, just a degree or two less from the changes. Well, my rear tires had been flat spotted since purchasing the car (It sat for well over 6 months), and have gotten progressively worse, vibrating the whole car. I just got new tires and the difference is amazing, never realized the old tires were that bad. My timing pull dropped from ~8 on APR to 5 degrees!

I guess that the vibrations were being picked up by the knock sensors? In any case, just thought this was weird enough to warrant mention here, maybe someone else is experiencing similar issues and hadn't thought of that as a potential cause.


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## 20v master (May 7, 2009)

Indirect correlation. Nice try though. Seriously, if "vibrations" were picked up by the knock sensors and led to timing pull, those with open exhausts and upgraded motor mounts would have worse problems. The knock sensors are looking for specific frequencies at specific times. This is how two sensors detect knock on four individual cylinders. Have you cleaned your IC's out as well as your IAT? Oil in the intake tract is horrible for detonation. Where does your PCV route to? Upgraded exhaust lowers the pressure on the turbo output, aiding in turbine efficiency, meaning less work to make boost, meaning more efficiency there. Remove restrictions from the system, to improve efficiency all around which will lower IAT's and help your timing pull. Or add water/meth or higher octane.


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## Currancchs (Feb 24, 2011)

20v master said:


> Indirect correlation. Nice try though. Seriously, if "vibrations" were picked up by the knock sensors and led to timing pull, those with open exhausts and upgraded motor mounts would have worse problems. The knock sensors are looking for specific frequencies at specific times. This is how two sensors detect knock on four individual cylinders. Have you cleaned your IC's out as well as your IAT? Oil in the intake tract is horrible for detonation. Where does your PCV route to? Upgraded exhaust lowers the pressure on the turbo output, aiding in turbine efficiency, meaning less work to make boost, meaning more efficiency there. Remove restrictions from the system, to improve efficiency all around which will lower IAT's and help your timing pull. Or add water/meth or higher octane.


I thought it was strange myself, but I assumed if the vibrations were bad enough, it might have an effect, as it seemed at least to have here. My tires were REALLY bad btw. I mean, there was belt showing on portions, and portions of the tire that were not even worn to the wear bars... I wish I had taken pictures...

To give you an idea of what has been done to my car that would possibly effect this my modifications include:
Stage I BFI mounts all around (Tranny/motor/dogbone)
3'' 42dd DP
Neuspeed P-flo (IAT's pretty low, not a heat problem here)
Stage I SPEC 13 lbs. LWFW/organic disk/High pressure pressure plate
APR 93 Octane Tune
Run on only 93 octane gas from Shell/Mobil/occasionally Sunoco
Forge 007 DV (Actually running stock for now, but this has been on it most of the time, never noticed a difference in Timing pull with this v. stock)

I generally clean out the IC's every oil change. I have replace the MAF a couple months back. I have also cleaned the TB and IAT sensor. My coolant sensor is the newer "Green Top." The PCV system is routed in the stock manner. I replaced all of the hoses and PCV valve under the intake manifold about 6 months ago, when the brake booster line blew while driving I decided to just replace the whole mess of hoses under the manifold, as they weren't looking too great... I was thinking about water/meth soon, but am in school right now on a limited budget, maybe this summer when my financial situation (hopefully) improves.


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## Doooglasss (Aug 28, 2009)

MAF and spark plug conditions?

I agree with 20v- it's not the vibrations.


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## Currancchs (Feb 24, 2011)

Well, the MAF is almost brand new. I originally replaced with a reman Bosch, but then returned it because it was reading a bit low and bought the OEM one new from a dealer. The spark plugs only have about 5-8k miles on them. They are NGK's (Not copper, iridium I believe) one heat range colder than stock.

Could it maybe not be the vibrations, but could tires be so bad that they caused spikes in load/cylinder pressure that would encourage knock? It is just really weird that I dropped from 6-9 roughly degrees of knock across cylinders to 3-5 degrees right after a tire change...

Other information: NO BOOST LEAKS. I checked myself two weeks ago, then I brought it to a shop and had them recheck it, none were found. Most lines have been replaced with Silicone. (the PCV hoses are still rubber, as well as some N249 connections, because they were different sizes on either end and looked OK.

I am not trying to promote misinformation here, and I value your opinions, it is just weird that the decrease in timing pull coincided with this service.


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## Currancchs (Feb 24, 2011)

So, Max contacted me and sent me some great graphs of timing pull at various coolant and Intake Air temps. It seems like my IAT may have something to do with it... I know that I usually see single digit IATs in the winter here. When I start up the car, many times I'll see a temp of -4 or so, and after an hour of highway driving I hardly ever see it pass 10 degrees C. On warmer days I still don't get past 20 degrees C, although in the summer months, I remember seeing slightly higher temps. Apparently the ECU pulls timing if the IAT is below about 30 degrees C... I am running a cone filter with (probably useless) heat shield, so I would expect my temperatures to be higher, even in the winter... Maybe my IAT sensor is screwy, I know I cleaned it, but since it is less than $30 bucks maybe I'll just replace it and see what happens.

What are you guys seeing for IATs under normal driving conditions in the winter? Are my readings (5-20 degrees C max) normal for NH winters (10-40 F ambient)? It was a warmer day than usual when I picked up the tires, maybe this could have coincidentally lessened the timing pull?

Images Courtesy of the Great Max!:


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## Matt_B (Apr 22, 2010)

Currancchs said:


> Apparently the ECU pulls timing if the IAT is below about 30 degrees C... QUOTE]
> 
> Is this true, my WMI gives me temps around 10-12 degrees at the moment and around 20 in the summer. Surely this isn't detrimental??


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## Doooglasss (Aug 28, 2009)

Haha that's my tune!

My car sees under 30 degrees IAT on a 40-50 degree day. Under boost it actually decreases to around 25 due to my setup.



Matt_B said:


> Currancchs said:
> 
> 
> > Apparently the ECU pulls timing if the IAT is below about 30 degrees C... QUOTE]
> ...


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## Matt_B (Apr 22, 2010)

Absolutely, I have been seeing inlet temps of 1 degree over the last couple of weeks and the power has been awesome.

Why cant we have winter air and summer traction doh


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