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Discussion Starter · #1 ·
I've noticed this a few times since I bought the car. There seems to be a noticable hesitation in power delivery when accelerating from low revs at WOT. It usualy hits around 2200rpm when the turbo is spooling and causes a slight dip in power. I've not been to bothered about it but after todays logging its showing up as a drop in air flow so there must be something causing it.

Before we start however, I must point out I've had this problem since before the car was Revo'd - although it wasn't as pronounced before the remap - I'm sure this is to be expected due to the increased output.

The logging I did today has confirmed there is a problem both before and after the TIP install. Here's the graphs:





As you can see theres a noticable dip just after spool up. The above log shows 100% open throttle during the runs (I haven't included that info on the graph).

I initially thought it could be the infamous temp sender. I had that changed today to the uprated 'green' part while at Awesome. While this hasn't sorted the issue its at least piece of mind that nothing else will go wrong with that lol!

So. Where do I start with fault finding on this one? Could it be the MAF? Its showing peak flow of around 179 g/s since the Forge TIP has been fitted - are these peak figures consistent with a healthy MAF?

Any help would be appreciated [:)]
 

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Sure you haven't actually bought a TDi [:)], that's a very common symptom on TDi's at 2200 rpm - mine does it too. I've just learned to live with it.
 

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It would be interesting to switch the car back to stock with an SPS3 and do more airflow logs to see if its still there.
 

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Hi Tabs, Have you tried cleaning/replacing your maf.

I had he same problem on a previous turbo car.And whatever i did i
could not cure the problem, Chipped it, changed dump valves, hoses,
knock sensors

etc etc till 4 years later when the maf finally packed in and i changed it.The problem was cured instantly.

Another possibility could be a dirty throttle.
 

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I ain't no effin padawan
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Mark

I'm not sure you actually have a problem.

To me it looks like the turbo spools up, overboosts slightly, and then settles down to requested boost levels.

At the same time as the turbo is spooling up, the timing is taking a dive, and will take a little while to come back up to where it should be after spool. If you log 003 and 118, and then 003 and 115, you'll see that the boost controller holds the wastegate shut on spool up, and then starts to open it as boost approaches requested. It'll over shoot slightly, which will correspond with the first peak in airflow, and then will settle down an match requested. You'll also see that timing dives fro 25-30 btdc to about 0-5 btdc, at the same point, and then settles down and runs from 8-20 btdc smoothly increasing as you increase in revs.

What you're feeling is the boost drop after overshoot, (it generally then undershoots a touch), and the low timing advance. It's normal, and the more boost you run, the worse it gets.

It's probably worse with the TIP, but should adapt out a little. You can see that spool is quicker and more aggressive with the tip.

Your maf readings suggests that you not only have a health maf, but a pretty healthy car. A 210lcr logs about 165g/s through the maf, and a chipped one logs about 200g/s.

At 180g/sec you're at about 230hp, which considering you have no downpipe, is PFTM.

You should have put it on their rr before and after. One thing is for sure. Your logs scream . Anyone who hasn't got a forge tip. BUY ONE!
 

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Discussion Starter · #10 ·
Thanks for that John. So what you're saying is its normal for the dip in power to occur.

I take it changing the settings for boost and timing via SPS would help 'iron out' the dip somewhat?

I'll log blocks 003 and 118/115 to see the corresponding dips. Interesting stuff this [Y]
 

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I ain't no effin padawan
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Yep

It sort of overboosts, then underboosts, then levels out.
 

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Sure you haven't actually bought a TDi [:)], that's a very common symptom on TDi's at 2200 rpm - mine does it too. I've just learned to live with it.
Really? ive never had this, even with the hybrid turbo etc... Having said this the last few days ive been experiencing odd things but i think its my MAF
 

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This is a MAF log which I did when running Revo, note there's no hesitation at all, just a progressive rise in airflow.

Posted Image
 

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Tabs, i think you should give MRC Tuning a call!! Since i've had my car back from them it is AMAZING!! Thay are God in my book..
 

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Discussion Starter · #16 ·
This is a MAF log which I did when running Revo, note there's no hesitation at all, just a progressive rise in airflow.

Posted Image
Nice peaks [:D]

Your graph is smooth. No doubt about that. Which Revo code were you running? Stage 2?
 

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Discussion Starter · #17 ·
Did you see comparable blips in the RR sheet from the recent SCN Awesome day?
Just found my graph on Awesome's site (from the RR day):

Posted Image


As you can see its a bit sprodic and certainly hits a spot around 3000rpm which ties in with the graphs I have above.

I'm going to do some more logging, except this time I'll use third of forth gear and start low down the range and take it all the way to the redline.
 

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Mark, that was with Revo 4bar.

In all the logs i've done with Revo and CC I have never seen a dip like yours is showing.
 
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