# How Much boost in a stock 1.9tdi ?



## DVR68U (Oct 19, 2004)

hey guys how much boost does a stock 1.9l tdi make its got a t15 garrett turbo ?
thanks guys 
cheers brenton


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## GoFaster (Jun 18, 1999)

12 - 16 psi (0.8 - 1.1 bar) depending on model year for the lower-powered models. The 130hp and 150hp versions have a bigger turbo and run more boost ...


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## DVR68U (Oct 19, 2004)

*Re: (GoFaster)*

so the t15 puts out 12-16psi , is there any way to turn it down on the garret? i herd the kkk turbos have a adjustable wastegate.


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## MXTHOR3 (Jan 10, 2003)

*Re: (DVR68U)*


_Quote, originally posted by *DVR68U* »_so the t15 puts out 12-16psi , is there any way to turn it down on the garret? i herd the kkk turbos have a adjustable wastegate.

Boost is controlled via the ECU.. If you did up the boost without a ECU upgrade, you would most likely be in limp mode quite a bit. Easiest way to up the boost would be a chip upgrade


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## DVR68U (Oct 19, 2004)

*Re: (MXTHOR3)*

yeah i want to lower the boost , and put this turbo onto a small gas engine . cheers brenton


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## GoFaster (Jun 18, 1999)

Oh ... Then you won't be using the stock N75 boost control solenoid anyway.
By the way, there is no "T15" used on a TDI. The two variations that are Garrett turbos are the GT15 wastegate style turbo used on the early A3 and B4 90hp engines (Engine code 1Z only - the engine code AHU used a KKK K03-006 turbo), and the VNT15 variable-geometry turbo used on the 110hp models since the outset and on Mk4 90hp models. These two turbochargers both have "T15" in their common names but they are totally different.
The GT15 uses a conventional pressure-to-open wastegate, and it can be controlled using any boost controller that you care to choose. The wastegate needs about 5 ~ 7 psi in order to open, so you can't regulate it lower than that, but a regular boost controller (simple mechanical or fancy electronic) can control it anywhere between that and the stock setting.
The VNT15 is vacuum-to-close, and is a WHOLE different ball game. I don't think this can be used properly with a mechanical boost controller. If you can find a strategy for applying the vacuum then you can regulate it. The stock setup has the intake manifold pressure "mapped" throughout the entire speed and load range, rather than using a "closed, but open when max exceeded" strategy that a wastegate turbo uses.


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## DVR68U (Oct 19, 2004)

*Re: (GoFaster)*

hey mate thanks for the great info, so is the stock waste gate on the 90hp models (gt15) set at 12 psi or is it less . i want you to say 8psi but i guess it might be higher due to the diesel settings. does any body have a compressor map for a gt15 ? i want to make my carby 1.8l into a torque monster








cheers brenton


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## GoFaster (Jun 18, 1999)

Told ya above ... the wastegate needs 5 to 7 psi to open it on a GT15. The TDI uses the N75 valve to regulate the boost pressure down to the wastegate-opening pressure. You can use a mechanical boost controller to do the same thing.
I have the compressor map. Looking at it now. Higher revs on your engine are getting into an area where the pressure ratio at a given turbo RPM is dropping off. It's not ideal, but since you are not running an extreme pressure ratio or much over 6000 rpm on that engine, I think you'll be okay with it.


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## DVR68U (Oct 19, 2004)

*Re: (GoFaster)*

thanks alot for the info. i just wanted to check that the waste gate was set low before i got the motor running . i only plan on reving up to 6000 anyway so should not be a problem. 
i will post up my results once i have the system up and running. 
so if i up the boost to 12psi then the turbo wont be able to handle the volume at 6000 rpm will it ?
cheers brenton


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## GoFaster (Jun 18, 1999)

It will do it (barely), the pressure ratio is 1.8, but the turbo RPM is around 140,000 and it's beyond the most efficient operating range. At a more TDI-like engine RPM, that puts the turbo near its maximum ratings. I don't think the engine will like that sort of boost, anyway. At 8 - 10 psi without any spikes, you'll be fine.


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## DVR68U (Oct 19, 2004)

*Re: (GoFaster)*

no prob ill shoot for around 8psi ,and try to keep the revs to 6000. 
cheers brenton


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