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VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

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Old September 13th, 2017, 18:06   #16
Rembrant
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Rem, I looked at the data and things look good until just after 4k RPM and then the air just drops off a cliff even though the RPMs are still increasing (just before, what looks like, the OP let off the pedal). Under 4k RPMs I cannot see there being any issues, nothing that would suggest a big impact to FE.
Well, I can't comment much on how the engine is supposed to behave above 4000 RPM. I've done a ton of data logs, but I never bothered testing anything above 4 grand as I'm never up there anyway.

What I do know, from my own experience, is that in the lower daily driver RPM's, if everything is working properly, the MAF specified and MAF actual usually track pretty closely together, all the way up to 850 and back down to idle.

The MAF numbers make much more sense if you can see the boost numbers along with them. See where the MAF actual spikes when he first stomps the pedal down? That's where the boost is spiking.

To be honest, I was really only looking at the numbers and not really paying any attention to FE issues.
Personally, I'd spend 10 minutes testing a MAF, and if it didn't behave 100% perfectly, I'd chuck it in the bin and buy a new one...lol. In VW TDI repair dollars, they're about the cheapest thing you can buy.

Then again, I've been known to buy things I don't need.
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Old September 15th, 2017, 16:40   #17
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If it was me, I'd do the same tests you've already done, but include boost in the data. A good data log for the ALH is MAF, Inj Timing, and Boost, all together.

Rembrant, here is the data log I did today with all 3 together.

https://log.malonetuning.com/chart/3...KaegEAAA%3D%3D
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Old September 15th, 2017, 17:35   #18
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The instructions on Malone's site say to start around 1,500 rpm (others will say 1,800) in third gear and then slam it until you hit redline. I'm not seeing that in your logs: you're not hitting redline and there doesn't seem to be a very rapid increase in RPMs.
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Old September 16th, 2017, 01:33   #19
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I'm no expert, but I don't see anything there worth worrying about.

I'd go back and review the things that were changed. If the mileage decreased after a TB change, or after changing IP seals, etc...look at those items.
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Old September 16th, 2017, 14:51   #20
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The instructions on Malone's site say to start around 1,500 rpm (others will say 1,800) in third gear and then slam it until you hit redline. I'm not seeing that in your logs: you're not hitting redline and there doesn't seem to be a very rapid increase in RPMs.
Here is the new one I did this morning hitting redline in 3rd gear.


https://log.malonetuning.com/chart/3...vCjQEAAA%3D%3D

I do believe things have improved and I'll know for sure when I fill up next.
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Old September 20th, 2017, 02:32   #21
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OK, thanks, that's a bit easier to review.

There's a bit of a boost spike happening. If, however, you're not going in to limp mode then it's not substantial enough to be an issue: my wife's car is a bit spiky and it's been that way since we've owned it and it's never went into limp mode. Other than this the boost/turbo looks like it's behaving fine.

I still see that the MAF Actual drops quite a bit when hitting higher RPMs. I'm wondering whether you might have some intake clogging. That'll drop FE a bit, though I believe that it has to be fairly substantial for it do have a big impact on FE.
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Old September 20th, 2017, 11:48   #22
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These motors don't really flow above 4000 in stock configuration, looks normal. MAF request and actual do not have to follow each other.
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Old September 21st, 2017, 00:16   #23
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These motors don't really flow above 4000 in stock configuration, looks normal. MAF request and actual do not have to follow each other.
I'd have to look at some of my old logs, but I don't recall such a severe drop off. But, there's little reason to be running these engines above 4k RPMs (unless modded for it).
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