How much timing pull is normal?

[VancouverGTI]

Hey all,

I got an APR RSC exhaust system a couple of weeks ago, along with the supporting Stage 2 tune. There's a definitely a power difference, but it's not much. After running some logs, I believe I'm seeing more timing pull than I should be, but I'm not clear on what's normal for our cars in general, or those with a tune.

I sent the logs in to APR but haven't heard back yet. In the meantime... is this normal for Stage 2 on a cool evening? I can't imagine what I'd be seeing on a hot afternoon.

 

[dbduke]

No, not normal at all. Normal pull should be like 2 or 3 degrees max, unless you're heat soaked. What was the ambient temperature? Did you log IAT's as well?

What kind of gas are you running? Bad gas can be the culprit for sure.

 

[mk5gtiguy]

Time for a FMIC

 

[dubbin]

^^ugh, on a cool evening, i dont think so. whats a "cool evening" op. 60-50* temps should not be seing 5-6-7-8* of time pull.

this makes me want to run some logs.

 

[VancouverGTI]

Sadly, I didn't log IAT's, but I'm thinking heat soak really shouldn't have been an issue.

It was about 16º C (60º F) and the dead of night. I use a freeway on-ramp to avoid shattering any laws, and the next off-ramp is 4kms away. So, by the time I'm back to where I started, it's an 8km drive at a leisurely 90km/h... more than enough airflow to cool the engine between runs, I would think?

I have given the gas idea some thought, yeah... I'm wondering if my programs got switched around during the Stage 2 flash, somehow? I'm running Shell V-Power 91, and have the 91 octane file selected... but maybe it's really a 93 file?

All that being said, I have been thinking about picking up an S3 intercooler... :biggrin:

Gotta get this sorted out first though. Thanks guys... anyone else got any suggestions or thoughts?

 

[dubbin]

hey man, im running logs this friday, now its going to be in the middle of the day, so its gonna be pretty hot for me, ill try to get logs, but i too am on a 91 oct map. ill see how my logs look and ill post them up. i have already an s3 ic :thumbsup:

 

[dbduke]

IAT's shouldn't be a problem in those conditions, and shell v-power 91 should be solid for a 91 octane tune.

Check your fuel trims and post them up... Are you running an intake? Which one?

 

[dubbin]

if for some reason he is on a 93 program running 91 then that could very well be the culprit, but i am going to highly doubt that here.

 

[VancouverGTI]

dubbin, thanks in advance for sharing your logs! I'll log IAT's next time so I can compare against your S3 IC. :thumbsup:

duke, yeah, I'd hope Shell should be a reliable enough fuel. Sorry, you've lost me on the fuel trims... do you mean rail pressure (actual matches specified quite nicely)?

My intake is a BSH Tru Seal, Stage 1 & 2, and according to earlier dynos when I was Stage 1, definitely flows better than stock. You're right that I should consider it here, though... who knows, right?

The octane issue is definitely on my mind; it would certainly explain the pull.

 

[teamx]

I recently logged and got the same timing pull as you did. My problem was heatsoak for sure. Had just driven 30km's (driving at legal speeds) to my mate who has VAG-COM. Temps were slightly hotter then yours - around 24º C. The stock cooler really doesn't cut it when you're tuned. My mate has a K04 GTi with S3 IC and Forge Twincooler and his intake temps were equal to ambient on the same day, logged directly after I did.

 

[dbduke]

OP, fuel trims refer to the adjustment the ECU makes to the readings its getting from the MAF. Think of it as a correction factor that accounts for the manufacturing variability in the cross-sectional area of your intake at the mass air flow sensor.

A number of aftermarket intakes create problems with the MAF measurements, either because the sensor is placed incorrectly, the geometry of the intake creates turbulent flow, or the cross-sectional area at the MAF is too different from the stock configuration. All of this results in air flow measurements that confuse the ECU and cause it to inject too much or too little fuel. This can lead to pre-ignition and timing pull.

The ECU has an adjustment range of +/- 25% (I think), but if you're over 15% in either direction then you'll often start to see problems. Several vendors, especially BSH, have had issues with their intakes creating fuel trim problems, although BSH to my knowledge has these solved a long time ago. And those issues were on the FSI, I haven't heard of MAF issues on the TSI, but its still worth checking out.

You can check what your idle and partial throttle fuel trims are in vag com. Its block 31 or 32 or something like that.

 

[VancouverGTI]

Our cars definitely have a problem with heatsoak, there's no doubt. I've never owned a car that's suffered as badly from it, and this isn't my first turbo or anything. Yeah, a tune only exacerbates the problem.

I'll definitely fire up VAG-COM later today to have a look for those fuel trim blocks! Block 31 is Lambda, if memory serves correct, but I know labeling varies from car to car, too. The bright side with the BSH solution is that they leave the OEM MAF piping alone, though that wouldn't rule out the possibility of different intake turbulence characteristics.

The log of Lambda shows an increasingly rich mixture, which I'd expect, but I don't know how to convert 0.71 (the richest point) into an actual AFR?



Fueling itself seems to be a non-issue, as I'd expect from a TSI.

 

[dbduke]

lambda = actual afr/ stoich afr
stoich afr = 14.7, so just multiply lambda by 14.7 to get your afr

 

[VancouverGTI]

Awesome, thanks man... so at the peak, my AFR is 10.4 to 1.

I wish it were easier for others to post their logs here. I'd love to compare that to other CCTA's.

 

[dubbin]

well im cbfa, if its going to matter, but i will post them up when im done :thumbsup: