GT1749V - Max power, torque and boost pressue? Now limp mode

Does anyone know what this turbo is good for?

It's standard equipment on my Audi A4 1.9 TDI (B6). I've had the car chipped to just under 180BHP and 450NM. Boost requested is at 1.4 bar and the limit was raised to 1.6 bar after constant overboost issues causing limp mode in high gears. However the car still overboosts, just under heavier load / high speeds / bigger hills. Always seems tyo be in 6th gear after 3,000rpm with some level of gradient involved.

I've replaced the vacuum hoses, intercooler pipe, egr valve (serious leaking) to no avail. I've now also replaced the turbo with a low mileage one (full actuator movement, very clean and no play in the shaft), which seemed fine at first (4 weeks ago) and on the long journies at that time. However overboost is now back bringing in the limp mode. VAG-COM group 011 shows the N75 cycling the actuator fully. Sometimes there is no fault code and other times there is the 17965 - Charge Pressure Control: Positive Deviation P1557 - 35-00 - - code.

I'm running out of ideas now and wondering if the the power or torque is genuinely too high for the turbo. Or perhaps there is a sensor somewhere that the power or torque are exceeds it's limit. Or that my car just really doesn't like the ever growing short journies followed by fast roads.

Any ideas would be greatly appreciated, as I'm now out of them!

Is your audi a 130hp pd motor with a vnt17va unit.......taking in to concideration that the newer turbo is functioning correctly i would say that the map is too aggressively fueled etc.......can you tell us what fueling mods you have on the car like a tuning box for instance etc.

Yep it's a PD130. The replacement turbo is the same model from a 2003 car (mine's a late 2004 car), that was removed over a year ago and had few miles.

The turbo is a GT1749V (not sure about the A, but possibly). No tuning box, a custom remap (chip) carried out by VAG tuning specialists on a dyno. Running BP Ultimate diesel fuel, no additional additives.

Sadly I'm out of ideas, and can really only think it is the remap / chip, or the exhaust gases are too high for the turbine to cope with. Also have a catback 2.0T petrol exhaust on it, not sure if that could cause an issue, I doubt it though.

sounds aggressive but i know a few of the lads with pd 130s in the uk can hit 190bhp with just a tune for long periods without out any issues thus far apart from the clutch , this seems to be the only reason that the stay below about 175bhp , due to the cost of replacing the six speed clutch. the lads with these cars recomend 21 psi max for turbo longevity but allot are running 23 psi with spikes upto 25 but its believed to be taking a risk .
not sure what tht is in bar pressure

The exhaust could be too restrictive as diesels pass larger exhaust/soot particles........if the turbo is from another 130hp pd motor it will be a vnt17va = 130hp and the vnt17vb means its from a 150hp motor.........i'd be inclined to think it was the tuning have you had the standard chip put back in to see if you can get limp mode.......if it doesn't give limp mod then i'd ask for the fueling on the vag-tuning chip to be backed off a little.

cog said:

sounds aggressive but i know a few of the lads with pd 130s in the uk can hit 190bhp with just a tune for long periods without out any issues thus far apart from the clutch , this seems to be the only reason that the stay below about 175bhp , due to the cost of replacing the six speed clutch. the lads with these cars recomend 21 psi max for turbo longevity but allot are running 23 psi with spikes upto 25 but its believed to be taking a risk .
not sure what tht is in bar pressure

Click to expand...

Yeah I'd heard of others with higher bhp than mine, they all seem to be below 300ft/lbs (aroun d 400NM) of torque though, so I was a little concerned as mines 331ft/lbs (around 450NM) aparantley. Clutch was replaced around 10k ago, with no signs of slippage so far.

1.4 bar (my requested boost) = 20.31 psi
1.6 bar (my boost limit) = 23.20 psi

mojogoes said:

The exhaust could be too restrictive as diesels pass larger exhaust/soot particles........if the turbo is from another 130hp pd motor it will be a vnt17va = 130hp and the vnt17vb means its from a 150hp motor.........i'd be inclined to think it was the tuning have you had the standard chip put back in to see if you can get limp mode.......if it doesn't give limp mod then i'd ask for the fueling on the vag-tuning chip to be backed off a little.

Click to expand...

Cheers for the info, I didn't realise it was a different turbo on the PD150, makes sense though.

The exhaust is the same diameter, just splits at the centre box to two mufflers and tips, rather than just one at the left, suppose the mufflers could be more restrictive - I kind of which I hadn't done all this now, as it's making finding the cause of these issues harder.

I think you may be right, getting the stock tune back as from what COg has also mentioned, the boost may be too high.

i would also say that that clutch will be deffiantly slip with that much tourque , they normally back off the tourque at peak boost to around 280ftlbs to save clutch life. but some still slip it then . if the clutch is new id say thats the main reason it has no sighns of slipping unless he put a sachs upgrade in there do you know . where did you get it chipped do you have any info

cog said:

i would also say that that clutch will be deffiantly slip with that much tourque , they normally back off the tourque at peak boost to around 280ftlbs to save clutch life. but some still slip it then . if the clutch is new id say thats the main reason it has no sighns of slipping unless he put a sachs upgrade in there do you know . where did you get it chipped do you have any info

Click to expand...

I asked about the clutch at the time as I thought they were rated to 300ft/lbs. The tuner said it's always in the regien of, and they measure by bringing the torque up slowely to find the limits and backing off. I got it done at Awesome GTI in Manchester, UK. They have over 25years VAG experiece. They do alot of the RS's, Porsche's etc and even some of the VW TDI Cup cars, so I figured they would be a really good place to go. I'm not suggesting they've done a bad job or anything, which is why I've tried to eliminate all other possibilities first. Silly thing is, I've had it chipped since January (limp mode within 1000miles of though), so actually feel the car is slow now, as I must have got used to it.

Strange that I only get fault codes some of the time too, not always, which is weird and makes me think there may be two issues, one sensor related one not.

yeah thats correct a good tuner should graduate the tourque in on those. still sounds quite high a high tourque figure though, but its sounds like at least they knew what they were doing. have you contacted them with the the boost pressures and limp mode.

oh and by the way you do get used to the power

and usually want more to get that feeling back

It mite be an idea to change your iat/map sensor as they do/can go down....it should be located in the intercooler pipe after the ic before the inlet-manifold , something else you can try which should give you back your lost hp is to desconnect your battery over night which should give you back the hp you paid for!.

But yeah i'd go back to standard tuning to see where you stand and about the cat-back petrol exhaust , i guess you could always get rid of the cat and use a straight through piece of pipe.

Not to hijack but cog i need your clutch m8 as this one i got is slipping in every gear!!

cog said:

yeah thats correct a good tuner should graduate the tourque in on those. still sounds quite high a high tourque figure though, but its sounds like at least they knew what they were doing. have you contacted them with the the boost pressures and limp mode.

oh and by the way you do get used to the power

and usually want more to get that feeling back

Click to expand...

I spoke to them after the first couple of limp modes (around 1000 miles after the chip), they checked it out, couldn't see anything amiss. They raised the boost limit, but said there shouldn't be any problem. Overboosted on the way home 6th gear, pushing hard. Ring them again and they said it may be best to put back to stock to see if problems persist. Since then I carried out the previously mentioned changes and maintenance, but as yet haven't been back as I need to take a day off work which seems hard to do at the moment and I didn't want it to be down to a split pipe etc. I thought the new turbo had sorted it, but clearly not, so I will contact them again. Really just hoped it could be something else. I could do with finding out how to check the expected values of the MAP and MAF sensors too, so I can run VAG-COM and eliminate them as a cause.

That is normal.
I already remape more then 20 of this cars and in 6th gear when you have more then 170-175bhp it will overboost specialy going uphill.
You can dyno a lot of power in this engines but thats because most of them overboost.
Max safe power is acheived with more less 64 to 68mg of fuel and 1.45bars.

Regads,

I'm also inclined to think the MAP sensor may be to blame. If the original MAP sensor is still in the car (2.5 bar) then the latest tune requesting 1.6 bar would be more than the ECU's ability to track and would cause the fault, wouldn't it? I mean, a 2.5 bar sensor means 1.5 bar over atmosphere, meaning the software's request for 1.6 bar is more than the stock MAP sensor can see, meaning the ECU will throw a deviation code. Or am I just talking out my a$$ as usual?

no that seems to make sense to me maybe he does just need a 3 bar map with the newly raised boost

Lol for sure!!^^^ some tuners do what Marc1 has said and raise the boost pressure limit which has the worst effect = more overboost deviations (limp mode) when in fact it either needs to be lowered or that they need to understand that what is needed is a larger 3bar map sensor or in some cases 3.5bar map and a re-scaleing there after (tuner .....or no that means more fiddley work though doesn't it ) = "yes it does pratt!!"

Ed's TDI said:

I'm also inclined to think the MAP sensor may be to blame. If the original MAP sensor is still in the car (2.5 bar) then the latest tune requesting 1.6 bar would be more than the ECU's ability to track and would cause the fault, wouldn't it? I mean, a 2.5 bar sensor means 1.5 bar over atmosphere, meaning the software's request for 1.6 bar is more than the stock MAP sensor can see, meaning the ECU will throw a deviation code. Or am I just talking out my a$$ as usual?

Click to expand...

Correct!

Ok... as you wish.

When you have the problem solved just post here...

Go and change the map , put more fuel in it and the come here to tell me you have even more overboost.

BTW, take the cat out... that will overboost even more..

You need to have good remap...

majesty78 said:

You need to have good remap...

Click to expand...

I already gave the fuel amount needed for no overboost...I can also tell that you have to change the vnt map so it wont spike in high RPMs so it wont overboost.

I have logs here from this cars going uphill asking 1.45bars and they cant do less then 1.55bars if you ask a bit more fuel even with open vnt map so no need to bang the head to the wall too much.. just take some fuel until it overboosts max 100g.

Regards,

Thanks all for your contributions so far.

I understand what people are saying about the MAP sensor, and the fueling etc.

However, before the re-visit to the tuner, the requested boost and boost limit where both set at 1.4bar. The limit was only changed to 1.6bar, to see if limp mode could still be induced - which of cause it was.

ArturCosta - could you give me some more information please? Do I need to get the boost limit reduced again to 1.4bar and have around 100g less fueling added? Also, does this just apply to 6th gear. Is increased fueling and boost pressure altered for each gear independantly? I know the tuner said it is set to use less EGR as it pregresses through the rev ranges.

How do we make sure it doesn't spike past 1.55bar in 6th? Just by dropping the limit? Will this not bring on limp mode earlier like the first few times before the limit was raised?

Also how come this only hapens in 6th, but not other gears? Also I don't think it overboosted on the dyno at all, is this just because in 'real word' driving it's working a lot harder?

Regarding the MAP sensor - can I test this using VAG-COM to make sure it's not faulty etc?

Thanks again for your help guys, really appreciate it.

Did you dyno on a free flow dyno?

In 5th and 6th gear the "charge" on the engine is a lot higher so you need less movement of the vnt to make boost and also more flow of the turbine.

To make sure it does not spike past 1,6bars you need to remap it so the vanes position prior to go WOT is correct so it wont spike, that is the main trick on this cars because if it spikes what goes in must come out... so it ends up overboosting.

I have tested a lot of this cars and all that are running fine nearly dont smoke since more fuel will over boost.

Max I did was 175bhp more less with a positive deviation of boost of 50 to 75grams... thats 1,5bars at 4000rpm since asked is less

Just get a 1852 made to fit there and you are ok

ArturCosta said:

Did you dyno on a free flow dyno?

In 5th and 6th gear the "charge" on the engine is a lot higher so you need less movement of the vnt to make boost and also more flow of the turbine.

To make sure it does not spike past 1,6bars you need to remap it so the vanes position prior to go WOT is correct so it wont spike, that is the main trick on this cars because if it spikes what goes in must come out... so it ends up overboosting.

I have tested a lot of this cars and all that are running fine nearly dont smoke since more fuel will over boost.

Max I did was 175bhp more less with a positive deviation of boost of 50 to 75grams... thats 1,5bars at 4000rpm since asked is less

Just get a 1852 made to fit there and you are ok

Click to expand...

Thanks for the info. I'm not sure the difference between dyno and free flow dyno. It was on the rollers with fans pointing at it .

Sorry for daft questions but what is go WOT? (about to get flamed here, lol)

So do I just need to get him to change the fuel mapping in 6th (or 5th too?). And make sure the boost is only set to 1.5bar and 50 - 75grams of fuel?

Sorry that I don't understand too well, trying to learn though, so your help is much appreciated.

wot = "wide open throttle"

marc1 said:

Thanks for the info. I'm not sure the difference between dyno and free flow dyno. It was on the rollers with fans pointing at it .

Sorry for daft questions but what is go WOT? (about to get flamed here, lol)

So do I just need to get him to change the fuel mapping in 6th (or 5th too?). And make sure the boost is only set to 1.5bar and 50 - 75grams of fuel?

Sorry that I don't understand too well, trying to learn though, so your help is much appreciated.

Click to expand...

Some Dynos as a Maha it takes 45s to dyno the car as it applies braking to the rollers , in this type of dynos this cars overboost. On the others where it takes 10 to 25seconds it dynos really well.

There is no easy way to limit boost of fuel in 5th or 6th gear , you will have to limit it on all of the map.

About the gramas... pleaser remember that 1.5bars are 1500g of boost 1,5Kg... so I was talking about 75g of overboost is "normal" and the best you can get in 6th gear

About the fuel , 65mg would be good value ate 4000rpm , just remember stock ECU has only data for 60mg so you have to "make" your own 65... not just ask 65 at the remap

Regards,

mojogoes said:

wot = "wide open throttle"

Click to expand...

Thanks mate.

ArturCosta said:

Some Dynos as a Maha it takes 45s to dyno the car as it applies braking to the rollers , in this type of dynos this cars overboost. On the others where it takes 10 to 25seconds it dynos really well.

There is no easy way to limit boost of fuel in 5th or 6th gear , you will have to limit it on all of the map.

About the gramas... pleaser remember that 1.5bars are 1500g of boost 1,5Kg... so I was talking about 75g of overboost is "normal" and the best you can get in 6th gear

About the fuel , 65mg would be good value ate 4000rpm , just remember stock ECU has only data for 60mg so you have to "make" your own 65... not just ask 65 at the remap

Regards,

Click to expand...

Thanks ArturCosta, I 'think' it's becoming clearer now. So I need to have the fuel dropped to 65mg. The boost requested can be set to 1500g, but this needs to only allow for a spike up to 1575g and no more. By setting the boost at this level and reducing the fueling it will not be requesting too much from the turbo, as it will not reach the 1600g limit? Is this limit safe enough for the turbo?

The map also needs to be adjusted so the ECU tells the actuator to be be correct prior to being at WOT? How is this done though?

Thanks once again, finding this very interesting.

You have a map on the ECU that controls the vanes possiton on the turbo in each amount of fuel and RPM , you just have to tune that in order to not have spikes.

Here is a log going really uphill pushing 5th and 6th gear... the car had no more power to keep climbing RPMs so its clear how uphill it was.
This car dynos 170 to 175bhp.



As you can see its really the limit as the duty cycle of the N75 is really on its max , if it had more fuel it would overboost.
You can also see no spike on gear change that was made nearly at 4400rpm

Regards

ArturCosta said:

You have a map on the ECU that controls the vanes possiton on the turbo in each amount of fuel and RPM , you just have to tune that in order to not have spikes.

Here is a log going really uphill pushing 5th and 6th gear... the car had no more power to keep climbing RPMs so its clear how uphill it was.
This car dynos 170 to 175bhp.

As you can see its really the limit as the duty cycle of the N75 is really on its max , if it had more fuel it would overboost.
You can also see no spike on gear change that was made nearly at 4400rpm

Regards

Click to expand...

Thanks for that mate. Is this graph from VAG-COM? If so do you know what groups I need to choose and I will run a similiar test, and post results.

Could you confirm I have understood you properly on the other parts below please and I will get the tuner to amend as per your suggestions.

marc1 said:

Thanks ArturCosta, I 'think' it's becoming clearer now. So I need to have the fuel dropped to 65mg. The boost requested can be set to 1500g, but this needs to only allow for a spike up to 1575g and no more. By setting the boost at this level and reducing the fueling it will not be requesting too much from the turbo, as it will not reach the 1600g limit? Is this limit safe enough for the turbo?

Click to expand...

Thanks again.