Stock Boost on ALH 1.9L

[davealltheway]

Hi All,

Trying to find out what the stock boost, and/or max boost is on a 2001 vw jetta, ALH 90hp 1.9L, VNT-15.

Some have said 12-13 with a surge to 16, and others have said more like 18. Reason I ask, my TDI is going into limp mode, and trying to figure out at what psi (or mBar) it hits limp (over boost).

Appreciate your input!
D.

 

[03Springer]

It should reach 16 to 17 PSI sustained if all is well.

 

[davealltheway]

Great thanks!

 

[Curious Chris]

18 psi is stock sustained boost. Google dawes device for boost limiting.

 

[theantirice]

It should reach 16 to 17 PSI sustained if all is well.

That sounds a little high to me. I'm basing this off of where the rocketchip stages get you:

Stage 1 - 15psi tune
Stage 2 - 17psi
Stage 3 - 18.5psi
http://forums.tdiclub.com/showthread.php?t=294771

Anyone else want to chime in?

 

[VeeDubTDI]

I have always known stock boost on an ALH to be 0.9 Bar.

 

[Bob_Fout]

I have always known stock boost on an ALH to be 0.9 Bar.

Yup, stock is 12 to 13 PSI.

 

[turbocharged798]

Wow, so much bad info in this thread.

 

[oilhammer]

What's funny is all you have to do is A: check the shop manual and B: check the actual/requested values with a scan tool. Also keep in mind a boost gauge will be showing atmosphere PLUS turbo positive boost pressure. The ECU goes off of Manifold Absolute Pressure (MAP) which is what you can watch in the data stream.

The way to check boost on the ALH is to accelerate in 3rd gear from 1500 to redline, and record the MAP as it passes 3000 RPM. Monitor Group 011, Block 3 should be 1700 to 2200 mbar (which is about 25 to 32 psi.. but again, this is WITH atmosphere). If you want to figure out what the actual boost level is, monitor that same data block without the engine running, that will give you atmospheric pressure (usually around 950 mbar, but this depends on your altitude). As a general rule, 1 bar (1000 mbar) is one atmosphere at sea level.

 

[Curious Chris]

Ok stock TDI should be about 13 psi or .9 bar. The max by design is 18 psi sustained. The map reports mBar which has to be specified as gauge or absolute as there is no consensus on which it should be.

X2 on checking the Specified MAP and the Actual MAP as suggested. VCDS will do this for you. A nice 10 second run at full throttle will give you a good graph of the PID control loop and whether the system is meeting specified MAP.

 

[oilhammer]

People always ask this, and I am always curious as to the nature or context of the question. Since the ECU controls, and therefore monitors, the turbocharger's function, if you have no DTC stored for boost control there is likely not anything "wrong" with the turbocharger. I forget how far from requested the actual must be before a DTC is flagged, maybe 400 mbar or so? So I guess it is possible that if the boost cannot ever totally achieve requested BUT gets within that margin of fault detection the car could seem a little doggy in comparison to one that is in perfect working order. But again, a simple bit of time with a scan tool will show this.

Most complaints of "low power" on a TDI however are NOT turbo-related, BTW.

Now an OVERboost condition seems to be more common, and usually caused by sticky/stuck VNT bits on the ALH. Sometimes you can get it freed up, sometimes you can't. Sometimes it is just a flakey N75.

 

[Geordi]

Ok, so the turbo is capable of 14-16 psi sustained by the computer in stock setup.

Now, the $64 question: is that 'sustained' under load / acceleration, or at steady state cruise?

I'm trying to establish a baseline for my new TDI (2003 wagon auto) before I do anything crazy with it. Currently, the only way I think the turbo would go over 15psi is if I stuffed a scuba tank fitting onto the air inlet. At WOT, it might SPIKE to 16psi, but the computer (ScanGauge) and my external Glowshift gauge both show it almost instantly is collected back to about 11-13psi.

At steady state cruise, flat road, 75mph (dash speedo, about 72 GPS) I am reading 4psi continuously. This is while towing a VERY small open trailer with a table saw and miter saw on it... So the boost might be a touch higher than while running unloaded... But it still seems abnormally low to me. My mileage also isn't fabulous, it has been right around 36mpg full-highway and I have yet to crack a 600 mile tank even filling to the neck (ventectomy) and that is not towing. With this trailer, I lose about 2mpg, which is expected. I also realize I'm on winter diesel right now... But that shouldn't change the boost map.

What do the normal MKIV turbos run at while cruising at highway speeds?

 

[Curious Chris]

The only way you will see what the "maximum sustained" is 100% throttle in 3rd or 4th gear as you only get maximum boost when the load demands it.

Yes if the turbo is behaving it will overshoot a bit, 16 psi is fine, and then settle down to typically not more than 13.5 psi.

You are seeing what I would expect at 70 mph which is a little boost but not much. On my commute I am at 60 mph most of the time and at that speed I know the boost is even less than 4 psi.

 

[Ski in NC]

Geordi- the vnt turbo allows the ecu to control boost. The turbo is capable of much higher boost, but the ecu through the N75 and vnt vane controller position the vanes on the turbine to give the boost the ecu requests, no more, no less. There is no advantage to higher boost when engine does not need it for complete combustion. Other diesels with old school turbos or turbos with waste gates operate differently. Boost on those is pretty linear with load.

Best way to check turbo is to run vcds on a laptop- you can see the boost requested by ecu, and whether actual boost is close. I don't think scangauge gives you both numbers.

 

[mrrhtuner]

Hey guys, I'm trying to troubleshoot my turbo/limp mode so I used Torque Pro to log boost.

I did a few hard pulls in 2nd and 3rd gear and noticed that the boost is close to 20psi.

I made sure that torque was checking the MAP sensor also.

Can a bad turbo boost more? Or what could cause it to boost more then stock? The car is a 2003 alh manual with sprint 520 nozzles and nothing else done to it.

 

[LNXGUY]

Are you spiking to 20psi or seeing 20psi sustained? I wouldn't worry about a spike to 20psi then sustained around 13-14 on a VNT15. Sustained boost of 20 will lead to a quick death of that turbo though.

Could be sticky vnt vanes.

 

[mrrhtuner]

hmmm......

I just went out and did two runs, so this looks like VNT vane issues?

https://www.youtube.com/watch?v=VA86gkRuaWQ

https://www.youtube.com/watch?v=-SqGLAEKPdo

Right after each run, the car went into limp mode. The second video at the end still has me accelerating and it won't boost anymore to 22 PSI.

At the end of the second video, I also had a CEL come up which is the one I've been getting since buying this turd.

 

[LNXGUY]

Sounds like it.

 

[mrrhtuner]

I've been trying to figure this out, if the actuator is adjusted wrong as it controls the vanes, could that cause the overboost?

 

[csstevej]

Hook up a mity vac to the actuator and apply vaccum . It should start to move at about 3-5 in and be fully opened at 18". It should be smooth and hold a vacuum. There should be no ratcheting, if there is move the lever on the turbo with a wrench either a 14 mm or a 9/16 open end wrench.
It should be smooth and not notchy or crunching . It should also move a little more than a half an inch. Make sure it hits the stop.
Sometimes it's the actuator........sometimes not.
You may have to remove the actuator to be sure, just remove the c-clip at the lever.......get some spare ones, good chance you will loose it. I picked up an assortment of them from HF they had a nice box with different sizes for about 5 bucks or so.

All this can be done while turbo is on the car.

 

[kryptykr6]

Wow, Mine is having a major overboosting condition then. I have both a bluetooth OBD 2 adapter as well as a boost gauge and both read to about 26 psi spike and about 23-24 psi sustained. It's been doing this since we bought it about 9 months ago, and have already put around 20k miles on it. It now has 288,880 miles. I'm not sure it the turbo has ever been upgraded but I believe it is stock just from quick glances at it while rebuilding my motor for another reason.

 

[50harleyrider]

Wow, Mine is having a major overboosting condition then. I have both a bluetooth OBD 2 adapter as well as a boost gauge and both read to about 26 psi spike and about 23-24 psi sustained. It's been doing this since we bought it about 9 months ago, and have already put around 20k miles on it. It now has 288,880 miles. I'm not sure it the turbo has ever been upgraded but I believe it is stock just from quick glances at it while rebuilding my motor for another reason.

With a stock tune, you won't get 23-24 sustained-car will go into limp. Doesn't matter what turbo is on it. The vnt mechanism is usually the culprit on a stock VNT-15. 90% of the time, just needs cleaned. The numbers you are quoting would really be on a VNT17-22 with an aggressive tune like an RC3, nozzles,etc. I bet you're doing a lot of key cycling, huh?

 

[turbocharged798]

Or he is reading the pressure in absolute, in which case he needs to subtract 14.7psi.

 

[kryptykr6]

Yeah, before the rebuild I was doing ALOT of key cycling, and code clearing with Torque because it would go into limp mode constantly. It sucked, it has absolutely no power without that turbo, and I am not just basing that off limp mode, I have had my intake tube blow off under the pressures numerous times recently and instantly a power loss. I haven't had to cycle it or anything recently with it building that much pressure, which is by the way on top of the atmospheric pressure (I had thought the same thing with subtracting 14.7 but after watching in/hg stay at about 29 in/hg then spike to 53 in/hg then drop to about 49 sustained, all the while the boost gauge is reading around 24 psi). You can definitely tell its making that much pressure because it pulls hard then my friends TDi who has a stage 3 tune, bigger nozzles, ect. Also, mine has massive turbo mark, to the point where when I was taking a video of how it sounded, I left my phone on my well and went down the road and about a half mile away, you obviously couldn't hear the car but you could definitely hear the bark of the turbo as if it were right next to you. I'll try to upload the video. But as far as I know, I believe the car is stock, it didn't look like it was tuned or anything. But who knows. Here is that link to the video. Just make sure your speakers are turned up. https://youtu.be/dZju8liekiA

 

[AndyBees]

For what it's worth:

Stock, the 2002 ALH in my Vanagon showed 11 to 12 psi sustained .. would spike during acceleration to 15-16 psi.

Stage 1 Malone tune, 16-17 psi sustained and easily 19-20 psi spike going thru the gears accelerating ........ occasionally a 21-22 psi spike.

The Turbo gauge is VDO with the tap at the EGR assembly pre-ASV which is functional but EGR is physically deleted.

 

[antonio2001]

is a spike to 21 psi and sustained 16-17 safe for a stock vnt 15?

 

[AndyBees]

Considering the VNT15 on my ALH has a mild Stage 1 tune (no other engine mods) and has been running fine for over 80k miles (roughly 25k miles pulling a 1200 pound camper), I'd say it's okay. However, it does have about 208k miles on it now...... so, maybe I should consider an upgrade!.. I'm running almost a 6 quart oil system set-up. Also, my engine lays over on 50 degrees causing the drain from the Turbo to back up oil to at least the bottom of the Turbo bushing... just saying, maybe that is a good thing, which is contrary to the thinking here in the club as well as other places on the WWW.

 

[RBW]

Super High Spikes?

Hi all,
I just recently swapped my 2003 Jetta TDI ALH to a manual and she definitely pulls better now, but here's the thing - I just used VAGCOM to test the boost for the first time and I got spikes up to 37.28PSI with normal driving. It averaged 16.03PSI though, and the car actually requested 31.5 PSI at one point.
Now it didn't take long for me to realize this is not normal, but what could this mean for my turbo? I've never gotten any overboost codes, in fact I got an underboost code when i first bought the car and the turbo wasn't working due to the actuator.
Just looking for opinions
Thanks

 

[IndigoBlueWagon]

Not sure what you're reading, but keep in mind that some boost readings are atmosphere plus requested boost. If that's the case, 37.2 would actually be 37.2 less 15.7 or so, or 22.2. Still too high, but if that's a spike it won't kill your turbo.

 

[Curious Chris]

The stock VNT-15 is a twitchy turbocharger. Oh yes fast response but notorious on the overshoot. I put a Dawes device on my car when I had RC3 that pushed the sustained boost to 18. Of course lunched that turbo and now I have a VNT-17/22 that Jeff has tuned and is nice smooth boost.