vnt-15 limits

[Hinzipwo]

i did some searching but couldn't really find any useful information.

first off my car is a 2001 jetta tdi alh with an automatic transmission. we are working on the manual swap and wont be pushing any more power until the car is swapped.

my power goals are modest to say the least, im really only looking for maybe 150-160hp and a nice bump in torque. my question is how far can you push a vnt-15 without sacrificing reliability? i believe the limit of the stock setup is 15psi? could i push 20psi without hurting the turbo?

i plan on doing bigger injectors at least, that way if i want to upgrade the turbo later on, i have the fuel to match it.

my goal is to get bigger injectors and tune, but i dont know whether getting the vnt-17 is worth it for my power goal.

i apologize if i wasnt as clear in this post, dont hesitate to give me heck if this kinda thing has been talked about before, still figuring out how to navigate the forums!

 

[Nero Morg]

If I remember right, Vnt15 can sustain 17-18psi max. For 150-160hp you'd be better off with a Vnt17 and other supporting mods/tune.

 

[Poor King]

Ya.. even if it makes it through all that boost producing power, you will wear out the bearings real fast.

 

[Nevada_TDI]

Buy some .216 nozzles and a Stage 3 tune. These nozzles have room left for a bigger turbo. I can tell you compared to stock, a Stage 3 tune hauls a$$.
If at some point you want to go to a bigger turbo like a vnt-1749vb, you will already have nozzles installed to fuel it.

 

[IndigoBlueWagon]

I assume you have the original turbo in the car, yes? I ask because the internals of the VNT-15 were upgraded several years ago and it allows the newer design ones to run more boost.

I'm running a new design Mahle VNT-15 (same as the Garrett) on my wagon with PP357s, an 11mm pump (which you'll have), PD150 breathing mods (snorkel, airbox, turbo intake, intake manifold), a 2" downpipe with no CAT and a stock exhaust from the downpipe back. And a lift pump, although that's probably not doing much these days. The car is tuned with Rocketchip Stage 3+, which is a 19.5 PSI tune. He goes to 18.5 PSI with the earlier design turbo. With that setup and the earlier design turbo I dyno'd the car at 140/260 at the wheels on a very conservative dyno. It's plenty quick. And I can log 50 MPG tanks without trouble if I keep highway speed at 80 or lower.

This is the best setup I've had on any ALH I've owned. I had the car set up this way in 2007-8 until I upgraded the turbo. But I've gone back to this setup because it's smoke free, super responsive (much more so than a VNT-17) and great on fuel. As you might be able to tell, I am a big fan of VNT-15 turbos. Most people want to go bigger, but these work great. And set up and driven right they're pretty indestructible

 

[[486]]

they're already rather far outside their efficient zone with the stock maps, the exhaust pressure is already higher than boost pressure

if you're going to get a bigger turbo, do it when the trans is out, lots easier to wrestle the stock one out then
also your fuel economy will go up with a bigger turbine

 

[Hinzipwo]

Buy some .216 nozzles and a Stage 3 tune. These nozzles have room left for a bigger turbo. I can tell you compared to stock, a Stage 3 tune hauls a$$.
If at some point you want to go to a bigger turbo like a vnt-1749vb, you will already have nozzles installed to fuel it.

so what your'e saying is i can run bigger nozzles and a stage 3 tune on my stock vnt-15?

I assume you have the original turbo in the car, yes? I ask because the internals of the VNT-15 were upgraded several years ago and it allows the newer design ones to run more boost.

i do have the original turbo in the car. this makes me want to buy a newer vnt-15 considering the reliability

Edit: Does idparts sell this new style vnt-15?)

 

[IndigoBlueWagon]

Only the new style are available now, so that's what we have, and [486], I know about higher boost being outside the turbo's efficiency curve, but it turbos typically don't spend a lot of time at max boost anyway.

 

[Andyinchville1]

they're already rather far outside their efficient zone with the stock maps, the exhaust pressure is already higher than boost pressure

if you're going to get a bigger turbo, do it when the trans is out, lots easier to wrestle the stock one out then
also your fuel economy will go up with a bigger turbine

Hi

Just curious but , at highway speeds driven the same, how many more MPGs would you get with a 17 vs a 15 ?

Thanks
Andrew

 

[Hinzipwo]

Only the new style are available now, so that's what we have, and [486], I know about higher boost being outside the turbo's efficiency curve, but it turbos typically don't spend a lot of time at max boost anyway.

would there be any difference in reliability and rigidity between the reman and new unit?

 

[derek5120]

I didn't see any real difference between my stock car and vnt17 + 1019dlc mpg wise that is

Hi

Just curious but , at highway speeds driven the same, how many more MPGs would you get with a 17 vs a 15 ?

Thanks
Andrew

In terms of a turbo swap with stock injectors and ecu, I'd say there would be very little if any difference. I went from stock to vnt17+1019dlcs and only noticed a slight decrease in mpg, but then again the power difference makes you want drive quicker.

 

[[486]]

[486], I know about higher boost being outside the turbo's efficiency curve, but it turbos typically don't spend a lot of time at max boost anyway.

I'm not talking about when tapped out, I'm just talking 55-70 mph with the cruise control set, flat ground. IIRC it was something like 3 psi in the intake and 8 in the exhaust.

ETA: it is easy to see why they sized the turbo so tiny that it'd never be running efficiently, as then the EGR system would flow backwards

Just curious but , at highway speeds driven the same, how many more MPGs would you get with a 17 vs a 15 ?

never wasted money on a 1749va or vb so no idea, they're very similar dimensionally though so I doubt there'd be much difference.
going from a 1749v and stock nozzles to a 1752s (jammed into a VNT housing I machined out from a 1749v) and pp764 nozzles got me from 42 to 48, and it would actually get out of its own way rather than being an impediment to traffic

Were I to do it again I'd just go wastegated from the start, vane turbos are neat if you've got the drive to spend weeks setting up the maps right but WG turbos just plain work.

 

[Nevada_TDI]

Keep your vnt-15 and don't beat on it for now. Other than buying a new turbo, a tune, nozzles, and having them mounted and balance will still eat a chunk of change.
Around $300 for a tune, around $300 for nozzles, and $250 to mount and balance the nozzles. So $750.00 or so and you still can stay with the vnt-15 you already have.

 

[turbocharged798]

I would agree that a well tuned VNT15 setup is a riot to drive. Almost instant boost and full torque by 2000RPMs. You will absolutely need a clutch though.

Biggest thing is you have to make sure your car is in tip top shape. Proper functioning actuator, timing belt that is actually done correctly, clutch, and other maintenance things go a long way.

 

[Mongler98]

if you need to put the words, performance into the equation, then a turbo upgrade is worth it. still can get good cheap power from the stock 15... seriously spend $ on the clutch though....

 

[Hinzipwo]

if you need to put the words, performance into the equation, then a turbo upgrade is worth it. still can get good cheap power from the stock 15... seriously spend $ on the clutch though....

My problem is I’m still learning on driving standard, I’ve heard performance clutches are hard to drive and I feel like that would be hard to learn on. Give it to me straight, should I wait until I’m more comfortable driving stick to put more power into the equation?

 

[Nero Morg]

A South bend stage 2 daily feels like OEM pedal resistance, and drives normally. I have a stage 3, and resistance is doubled. Me personally, I wish I had learned on a harder clutch because you can really feel when they start to engage. With a soft clutch you question if it's actually working.

 

[Nuje]

I can concur. Just this past weekend, I replaced my stock clutch with a Southbend Stage 2 daily and literally forgot that I had a new clutch as I was reversing out of the driveway on the initial test drive. It really is that similar (read: easy to learn to drive stick with)

 

[Nevada_TDI]

I agree the Daily Driver 2 clutch from South bend feels just like stock pedal wise with a lot more grip.

 

[Mongler98]

Same here. Stage 2 SBC endurance. Nearly identical to stock. Only difference is you can actually stall easier if you dump it quick vs nearly impossible. TDIs are so freaking easy to learn stick with. So forgiving.
You won't regret it.
My advice, go sign up for autocross. You just need a helmet and a cleaned out car. Trust me...... its low speed cone racing.

 

[derek5120]

Look at Bully clutch in Ottawa, I see you are a fellow Canadian. They offer clutches that are competitive with SBC but you don't have go over the boarder, so they are cheaper. I've got a SBC stage 2 endurance and I feels the same as the Valeo smf kit in my other car.

 

[Hinzipwo]

Thanks guys! my whole idea is that when i do my manual swap i want the car to come out with a way different experience than driving my stock automatic car. a little bit more power and torque to make for a better driving experience. thanks for all the great suggestions!