Constant Low Power ALH

Sounds interesting, subscribing

ihredneck said:

I'm no professional, but the 45 mg/str appears at the lower RPM's but at the 3000 RPM mark they are within spec of 40.0-42.0 mg/str.

Though a value that I believe is out of spec on block 008 is the IQ MAF Limit @ 3000 RPM. The log shows 32.8 mg/str and spec shows it should be 36.0-39.0 mg/str. Not sure how to interpret this though.

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Ack! I missed the other spreadsheet pages! But, I still think that the requested fueling is higher than I have seen for stock: I have data from the son's Golf, which, at the time I gathered data, was a perfect runner, and I see a max of 41.8 mg/str.

"IQ MAF?"

Group 011 around 3k RPM it looks like you're losing boost. Sticking vanes or the N75 isn't responding correctly.

I just uploaded data from the son's car (Group 011) for reference.

IQ MAF = Smoke Limitation (last column on block 008 data log)

Was the data log taken while in 3rd gear at WOT on your sons car?? Also, does his car have a tune or any mods?

I agree, the boost drops off around 3000 RPM.
I guess is could be sticky vanes, probably pull the down pipe off to check that, I had manually stroked the vanes, but I will check again.
Another thought is that it is under fueling around that RPM.

Also, I was looking at the time stamps vs RPM from your sons car and mine and I noticed that his went from 1900-3800 in about 4 seconds, mine got to 3800 in about 9 SECONDS....now I know it is a DOG! Again assuming your car data log was in 3rd gear.

Saw some post where someone suggested oven cleaner to free sticky vanes.

ihredneck said:

IQ MAF = Smoke Limitation (last column on block 008 data log)

Was the data log taken while in 3rd gear at WOT on your sons car?? Also, does his car have a tune or any mods?

I agree, the boost drops off around 3000 RPM.
I guess is could be sticky vanes, probably pull the down pipe off to check that, I had manually stroked the vanes, but I will check again.
Another thought is that it is under fueling around that RPM.

Also, I was looking at the time stamps vs RPM from your sons car and mine and I noticed that his went from 1900-3800 in about 4 seconds, mine got to 3800 in about 9 SECONDS....now I know it is a DOG! Again assuming your car data log was in 3rd gear.

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Yeah, if I was logging then it would have been 3rd gear. I'm guessing that it was a stock tune at the time: fueling is maxed around 37 mg/str (car now has a Stage 3 tune, with same T4 nozzles, in which case I figure fueling is now substantially higher); log of my car shows max fueling around 49 mg/str - Stage 2 tune with DLC520s.

Sticking vanes most likely. Wife's car had a sticky spot around 3k rpm and I kept working it for a good year before I manged to get it to smoothen out: I should get a log of her car- it's the strongest runner of the lot.

That would be interesting seeing logs of all the blocks on her car. Also, how could you tell the vanes were sticky around 3k besides pulling the exhaust and watching the movement of the vanes?

I do plan do check them out once I get back from a work trip.

ihredneck said:

That would be interesting seeing logs of all the blocks on her car. Also, how could you tell the vanes were sticky around 3k besides pulling the exhaust and watching the movement of the vanes?

I do plan do check them out once I get back from a work trip.

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Performance-wise everything was great, on the wife's car, except that there was a lull around the 3,000 rpm mark, kind of like it was running out of fuel, flat-lining and then pulling back out of it and resorting to full boost/power. I'd cleaned the intake, EGR and intake ports in the head, so all was clean there.

Here's a graph of what the wife's car was like (I should look around and see if I have one since things have been working well). It didn't feel as dramatic as it looks, though for sure it had a pronounced drop-off. Again, this is NOT what a properly running engine should look like! (I'm pretty sure this is a VNT15 in this car, though I have never looked- ha ha, I'd thought that it had a DMF in it only to find out when I went to replace the clutch that it had an SMF! - why service records are a nice thing to have!)

https://log.malonetuning.com/chart/...DmsKbw6NmUsOWwpnCrWrDuwnDoQd3w6PDgsKWwo0AAAA=

I was really hopeful it was sticky vanes but they are as free as one could hope for, even got the car hot to see if it caused them to stick any and they are super easy to get full travel from.

Any other ideas???

has it always been like that? if it was like that when you got it could be a bad timing belt job where vagcom will show it is in time but... Timing is set based on crank-to-IP positioning. You still have the cam, and the cam gear could be off.

ihredneck said:

I was really hopeful it was sticky vanes but they are as free as one could hope for, even got the car hot to see if it caused them to stick any and they are super easy to get full travel from.

Any other ideas???

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Work backward from the vanes. Actuator. Hoses. N75. Vacuum pump. I'd still wonder whether there could be a boost leak happening.

indysoto said:

has it always been like that? if it was like that when you got it could be a bad timing belt job where vagcom will show it is in time but... Timing is set based on crank-to-IP positioning. You still have the cam, and the cam gear could be off.

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Been like this since I've had it. I've redone the timing twice, once when I did the belt job and second when I did the cam and lifters

UhOh said:

Work backward from the vanes. Actuator. Hoses. N75. Vacuum pump. I'd still wonder whether there could be a boost leak happening.

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Verified the N75, new vacuum hoses, checked vacuum up to N75 with a gauge and holds.

Wouldn't a boost leak show up on VCDS? Tracking requested vs actual was good and it held actual as long as I had a hill to climb.

A boost leak would tend to show up as you're seeing on the graph, weak response. Problem here is that whatever it is it's very subtle.

You checked that the actuator holds vacuum? (sorry, my memory is not being real kind to me of late)

I'm thinking that we need the presence of oilhammer.

I haven't pulled a vacuum directly on the actuator due to it holding boost as well as it responds well to the requested on the graph.
But willing to try if it is felt that it could be an issue.

Thought I'd recalled seeing this graphed, but... I went back and looked at the data....

Actual boost exceeds Requested at 2,835 rpm and, then, come 2,919 Actual dips below Requested. Nothing in this to be worried about, as it's normal for the ECU to have to correct/tamp things back down, EXCEPT, Actual, with no change in Requested, keeps falling off until at 3,900 rpm Actual comes back to match Requested. That's approximately a 1,000 rpm range/change in which the ECU is struggling to get things lining up.

Something is holding boost back, against the "wishes" of the ECU instructions. I'm not experienced enough to know whether it's possible for a boost leak to "heal" itself (matching back up at 3,900 rpm).

If it were a fueling issue I don't think things would correct (starvation would keep things knocked down). Really only leaves this as an air issue, and since boost can be met and because higher rpms can be had, it seems that it comes down on to boost itself. And for boost it's vacuum (vacuum noses, N75; also vanes and physical abilities of the turbo) and delivery (piping).

Like I mentioned in my last post, we really need someone like oilhammer to chime in.

I will hook up some pressure to the system and see of i have a boost leak somewhere.

I decided to chart the IQ values from block 8 vs the boost values from block 11 and that the IQ via MAF follows the actual boost trend almost identically so I could see fueling being effected by the boost issue because of what the MAF is seeing.

ihredneck said:

I haven't pulled a vacuum directly on the actuator due to it holding boost as well as it responds well to the requested on the graph.
But willing to try if it is felt that it could be an issue.

Click to expand...

Testing it from the top where it connects to the N75 would also check the line going down to the actuator.

ihredneck said:

I will hook up some pressure to the system and see of i have a boost leak somewhere.

I decided to chart the IQ values from block 8 vs the boost values from block 11 and that the IQ via MAF follows the actual boost trend almost identically so I could see fueling being effected by the boost issue because of what the MAF is seeing.

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I found a boost leak spraying soapy water on the tubes and connections.
Had a hair line crack where the PS pulley scraped the boost tube.
Just had the engine idling.

Another dead end. I plugged the hoses between the outlet of the turbo and inlet of the EGR and put 15 psi into it and no leaks, it held for at least 5 minutes.

Is there any reason I should pressurize through the intake?

If I missed it forgive me. Have you put a vacuum gauge between the N75 and the turbo during WOT? If so what did you get in vacuum inches?

No I have not. Will run that and let you know the results.

Okay, got some testing done.
Checked the turbo actuator with a hand pump and hooked up just after the N75. Thr actuator responds smoothly and no jerking when pulling a vacuum on it.
Also, at idle the vacuum after the N75 was at 14 in-mg and at WOT the vacuum just after the N75 got down to 4-7 in-mg

ihredneck said:

Okay, got some testing done.
Checked the turbo actuator with a hand pump and hooked up just after the N75. Thr actuator responds smoothly and no jerking when pulling a vacuum on it.

Also, at idle the vacuum after the N75 was at 20 in-mg and at WOT the vacuum just after the N75 got down to 10-13 in-mg

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This is about the same as I get.
I'm going to look at the boost log again, though UhOh is better with it.

The vacuum system uses PCM so it will always be a percentage of the available vacuum.

wonneber said:

This is about the same as I get.
I'm going to look at the boost log again, though UhOh is better with it.

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Can you recheck my numbers? The gauge was out of calibration and so are 6 in-mg lower.

After N75 to turbo actuator:
- 14" - Idle
- 4" to 7" - WOT

Any thoughts?

Let me throw this out there if I may: According to "factory specs" you turbo actuator should not hit the stop--request of full boost--until there is 18" of vacuum applied. If you only have 4" to 7" at WOT that would certainly cause an erratic boost curve.
I do not remember how much vacuum you have anywhere else at idle, but if you do not have at least 22" (24"-25" is better) of vacuum at idle straight off of the pump, then I would consider rebuilding the vacuum pump. It is an easy job to do and all you need is an o-ring.

The way it works makes no sense to me.
At Idle I get more vacuum then when I take off and it drops.
I have power as far as I can tell and the only thing I get is slightly lower MPG for the all highway driving I did for my last 2 jobs.
Use to get just over 50 MPG w/o the AC.
Last several years it dropped varying 45 to 47 or so.
Last job was 1 mile to the highway, 30 miles to the exit (1 toll booth in between) and 1 mile to the parking lot.
I should have gotten 50+
My boost gauge easily goes to 20-23 LB (US) boost if I punch it.
Some day I have to lengthen again, it was even higher when I installed the actuator.

Nevada_TDI said:

Let me throw this out there if I may: According to "factory specs" you turbo actuator should not hit the stop--request of full boost--until there is 18" of vacuum applied. If you only have 4" to 7" at WOT that would certainly cause an erratic boost curve.
I do not remember how much vacuum you have anywhere else at idle, but if you do not have at least 22" (24"-25" is better) of vacuum at idle straight off of the pump, then I would consider rebuilding the vacuum pump. It is an easy job to do and all you need is an o-ring.

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I'll check my vacuum at idle after the pump.

wonneber said:

The way it works makes no sense to me.
At Idle I get more vacuum then when I take off and it drops.
I have power as far as I can tell and the only thing I get is slightly lower MPG for the all highway driving I did for my last 2 jobs.
Use to get just over 50 MPG w/o the AC.
Last several years it dropped varying 45 to 47 or so.
Last job was 1 mile to the highway, 30 miles to the exit (1 toll booth in between) and 1 mile to the parking lot.
I should have gotten 50+
My boost gauge easily goes to 20-23 LB (US) boost if I punch it.
Some day I have to lengthen again, it was even higher when I installed the actuator.

Click to expand...

The turbo is set to 'vent' off the excess boost that the ECM sees that is over allowable boost. So at WOT the more fuel sent into the engine means higher boost so the vacuum drops from the N75 to the actuator opening the vanes in the turbo to help keep the boost under control. The vanes in open position are "venting" off boost like a wastegate setup would.