//// vnt 15 vs vnt 17 ////

Andyinchville1

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Apr 7, 2016
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2003 Jetta TDI wagon, 5 sp, 226K miles
Hi

I have the factory turbo on my car and when it goes out I plan on replacing it with a vnt17. .. (or maybe I can swap it out earlier and sell it as a good usable turbo...

Anyways, I know the vnt17 is considered an upgrade performance-wise but given that would I see better performance AND fuel economy with the 17 as opposed to a stock vnt15 given my mods?

Thanks
Andrew
 
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JETaah

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As far as I know, people do the switch to have the capacity to safely run higher boost pressures along with additional fueling/timing to accomplish the added performance. Just switching the VNT15 for the VNT17 is not a performance upgrade. If the program is requesting 15 PSI it will still produce 15 PSI with the VNT17.

I think that the ECU could use a tweak to compensate for the change. You may notice a boost lag otherwise between gear changes. Consult Malone to see what they have to say about it and if they would alter the programming.
 
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Andyinchville1

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As far as I know, people do the switch to have the capacity to safely run higher boost pressures along with additional fueling/timing to accomplish the added performance. Just switching the VNT15 for the VNT17 is not a performance upgrade. If the program is requesting 15 PSI it will still produce 15 PSI with the VNT17.

I think that the ECU could use a tweak to compensate for the change. You may notice a boost lag otherwise between gear changes. Consult Malone to see what they have to say about it and if they would alter the programming.

Thanks for the info I'll try calling them or contacting Malone.

I know my mods are not currently extreme enough to take full advantage of the 17 but I was thinking that maybe the larger turbo is freer flowing and may actually help MPG due to less restrictions but I know primarily most people looked at the 17 as a way to increase power or make for more reliable power continuously ...

Andrew
 

Growler

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the 17 is a bigger turbo, has a stronger main center shaft design than the vnt 15, bolts right up with a clip hose adapter and a modification to your factory vnt-15 exit hose and can handle more boost than a vnt-15.

HOWEVER, if you like the fun noises that a VNT-15 can make with an open exhaust you WILL miss these when you go to a VNT-17. it is just NOT as vocal as a 15.

FWIW, I put a 17 on my dads car after he blew up his 15 after getting a chiptune. (he is hard on cars) I did not however get his tune updated and his turbo lasted right up until the time he was pulling a hill full power and his timing belt let go.. it was for some reason rubbing against the tensioner sides and was about 2/3 a wide as it should have been so it just gave up.

anyhoo, a 17 is a great choice for mild tunes/injector upgrades when a 15 isn't able to produce/sustain the boost needed to keep the exhaust clear.
 

Andyinchville1

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Joined
Apr 7, 2016
Location
Virginia
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2003 Jetta TDI wagon, 5 sp, 226K miles
the 17 is a bigger turbo, has a stronger main center shaft design than the vnt 15, bolts right up with a clip hose adapter and a modification to your factory vnt-15 exit hose and can handle more boost than a vnt-15.

HOWEVER, if you like the fun noises that a VNT-15 can make with an open exhaust you WILL miss these when you go to a VNT-17. it is just NOT as vocal as a 15.

FWIW, I put a 17 on my dads car after he blew up his 15 after getting a chiptune. (he is hard on cars) I did not however get his tune updated and his turbo lasted right up until the time he was pulling a hill full power and his timing belt let go.. it was for some reason rubbing against the tensioner sides and was about 2/3 a wide as it should have been so it just gave up.

anyhoo, a 17 is a great choice for mild tunes/injector upgrades when a 15 isn't able to produce/sustain the boost needed to keep the exhaust clear.
Thanks for the info but I was curious about something still ....

Boost level for boost level, does the 17 offer less resistance to flow (most likely exhaust side or maybe intake side ) compared to the 15 ?

Reason I ask is because in my readings, I have heard it said that the turbo is actually the most restrictive part of the exhaust system ... I am wondering, if the 17 is freer flowing in any way maybe it will help MPGs ( as compared to a car set up with the 15) if one is not driving aggressively ?

Or maybe put another way, if 2 cars are set up identically (with the exception of the turbo) at any particular level of boost which car would get better fuel mileage ?

On the flip side, If 2 cars are set up exactly the same except 1 had a 15 with optimized tune and one had a 17 with optimized tune , would one car get better fuel mileage compared to the other when driving in the same manner?

It is interesting to learn about the turbo sounds .... at some point in the future I will be getting an exhaust system but for now still stock ... cat and all

Thanks

Andrew
 
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Mongler98

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Boost is boost. Should not change much in that sense that you ask. If your turbo is suspect and you want to upgrade, I would but I'd also get a step up in the tune and if you have the $ go with better nozzles. That will increase power and fuel economy if you stay off the pedal.
 

flee

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2002 Jetta GLS wagon
Thanks for the info but I was curious about something still ....
Boost level for boost level, does the 17 offer less resistance to flow (most likely exhaust side or maybe intake side ) compared to the 15 ?
Reason I ask is because in my readings, I have heard it said that the turbo is actually the most restrictive part of the exhaust system ... I am wondering, if the 17 is freer flowing in any way maybe it will help MPGs ( as compared to a car set up with the 15) if one is not driving aggressively ?
Or maybe put another way, if 2 cars are set up identically (with the exception of the turbo) at any particular level of boost which car would get better fuel mileage ?
On the flip side, If 2 cars are set up exactly the same except 1 had a 15 with optimized tune and one had a 17 with optimized tune , would one car get better fuel mileage compared to the other when driving in the same manner?
It is interesting to learn about the turbo sounds .... at some point in the future I will be getting an exhaust system but for now still stock ... cat and all
Thanks
Andrew
In a word, no.
The vanes are mostly open, i.e. not a restriction, on both turbos unless boost is
being requested. In that case, the amount of restriction is dictated by the amount
of boost the turbo is making. It takes energy to make boost.
One factor in the mpg question is the turbo's efficiency - in which the smaller turbo
may have a slight edge.
 

jmodge

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It’s hard to compare the two turbos in the same manner of driving because they’re not made to be driven in the same manner. pick your choice of Turbo by the manner in which you drive. When someone talks about restriction as far as a turbo is concerned, they are talking about power potential due to available air volume.
 
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