The 1.9L PD TDI powerquest

[Gigitt]

Ahyes the boost valve in reverse
It's been around for a while

Boostvalve.com

I've had mine for nearly close to 10 years now on the mk3 TDI

Glad you're enjoying the diesel mod bug and solved you're vnt spiking. Just keep an eye on the boost valve as they can get stuck or not seal from contamination and you'll be scratching your head why you have crazy boost/lag/powerloss issues that are unexplainable.

I added some irrigation taps to my set up so that it is easy to switch between N75 and boost valve control of the turbo. This also let's me easily switch back to N75 so if I'm having issues I can simply turn off the boost valve without loosing my preset setting.

[gldgti]

Ahyes the boost valve in reverse
It's been around for a while

Boostvalve.com

I've had mine for nearly close to 10 years now on the mk3 TDI

Glad you're enjoying the diesel mod bug and solved you're vnt spiking. Just keep an eye on the boost valve as they can get stuck or not seal from contamination and you'll be scratching your head why you have crazy boost/lag/powerloss issues that are unexplainable.

I added some irrigation taps to my set up so that it is easy to switch between N75 and boost valve control of the turbo. This also let's me easily switch back to N75 so if I'm having issues I can simply turn off the boost valve without loosing my preset setting.

Do you mean you have a VNT on your mk3????

Ive had MBCs on all my turbo cars that have normal wastegate turbo's, but never seen it used on a vacuum actualted turbo before for this purpose. I woudn't be at all surprised if people have done, but just never read it anywhere on the net yet

Took some logs tonight with the mod in place - heres a graph of boost specified versus actual in a 4th gear pull - rpm on the x axis, millibars on the y:



***EDIT*** well there you go, on the boostvalve website about using one without a bleed hole for VNT's.

Why isnt this plastered all over the tdi related forums?

[Gigitt]

Yep Pretty cool!
Just block that tiny bleed hole and the boost valve is used for vnt turbos :p

My mk3 is wastegated.
I was having boost issues about two years ago. Bugger if I could not find out why. Knew there was something wrong with the boostvalve so I drilled a 1mm hole in the cap as I was trapping boost in the wastgate line keeping it open. It worked but was too laggy. Well it turns out I was on the right track but forgot about the tiny hole already drilled into the side. It was blocked. So I soldered the hole in the cap that that I made, cleaned the tiny bleed hole with wire from a thin wire tie and it was restored back to perfect boosting.

Yes funny how there is alot of stuff on TDICLUB yet bugger if you can find it. Too many naysayers and keyboard trolls now filling up the threads and good info is lost.

Anyway it was boostvalve.com that reminded me of the tiny hole and it is tiny!!! That's why I could not see it.

Tdiclub was against the boostvalve after a year or two - especially if you used it to replace the n75. People were burning up turbos cause they were setting it too high and flooring accelerator to low in RPM's.
anywhoo I still run stock turbo with it
Haveing the taps allows me to switch between boostvalve only control of wastegate or in parallel with n75 so it acts as spike control.
Best of both worlds.

[kaanage]

Here's a great pic by a TDiClub member


gldgti, you should spin off a thread about this so it can be stickied for watercooled members usage.

Gigitt, I never read anything at TDiClub about using the BoostValve INSTEAD of the N75 on VNTs - that seems reckless. Or was it only being used this way on the wastegated TDi's. The issues I read about were to do with the valve not closing off soon enough once the vanes closed but gldgti doesn't have that issue at all from the log he has posted (maybe it develops over time as the valves gets dirty)

[gldgti]

gldgti, you should spin off a thread about this so it can be stickied for watercooled members usage.

The issues I read about were to do with the valve not closing off soon enough once the vanes closed but gldgti doesn't have that issue at all from the log he has posted (maybe it develops over time as the valves gets dirty)

I might do a sticky thread Greg, good idea.

I dont see how you could replace the N75 with just an MBC. VNT control requires more input than just the boost signal - you need accelerator position and you require a specified boost level to maintain. The boostvalve can't achieve that - in this application, all it is doing is preventing boost in excess of a specified point - but unless the n75 is also doing its job, the only other way you could rig it is to have the vanes permentantly closed unless the boostvalve is doing its thing - that is CRAZY - since you dont want 20psi all the time - you only want it when you also are calling for full power!

Anyway - with regard to keeping it clean - A valid concern and one I adressed without thinking to mention it. I have in line before my boost gauge and the MBC one of those little in line filters. Lots of 90's VAG petrol cars had them in their vacuum supply lines from the manifold, the one I'm using is the one that came with my boost gauge kit - its got a clear housing so you can see if it gets dirty. Its also only about 300mm from the boost takeoff, and then its another 4-500mm to the sender and MBC from there. Hopefully the MBC will stay nice and clean.

I'm going to take some comparative logs this morning with and without the MBC just to see the difference.

[Gigitt]

yes my method is only for wastegated turbo's.
yes I can replace a boostvalve for n75 for a wastegated turbo.

no you cannot replace an n75 with a boostbavle if you run VNT turbo.
I never said you could - sorry if there was any confusion.

[gldgti]

yes my method is only for wastegated turbo's.
yes I can replace a boostvalve for n75 for a wastegated turbo.

no you cannot replace an n75 with a boostbavle if you run VNT turbo.
I never said you could - sorry if there was any confusion.

No, I thought you said thats what people had done on tdiclub - not that you said you could do it.

[gldgti]

Heres a plot from a log I just took, with and without the MBC:


You can see from the 'spec' lines in each case that the way I applied the accelerator in each case wasnt really the same - I was much more progressive in my application without the MBC. But, there is still a big pressure spike as you can see.

Heres the MBC:


The inline filter:


The willing participant (needs a wash!):

[Gigitt]

No, I thought you said thats what people had done on tdiclub - not that you said you could do it.

I initially found out about MBC on tdiclub for my wastegate turbo. There was also talk about using them on vnt turbo but not to replace n75 but to use them like you have. tdiclub don't talk about them any more they just say a good tuner will prevent spikes etc.

[gldgti]

So, heres a challenge for those with Viezu tunes - can you do a bit of a fuel consumption comparison between your perf map and race map for me?

I have put the race map back on the car on the weekend to do the data logging, and drove to work with it today. Anyway, my indicated fuel economy (by the MFD) is considerably better than before.

I'm ready to accept any number of reason it might show better fuel economy but in reality (by the end of the tank) not actually be any different at all - however it also occurs to me that if there is a significant change in injection timing with the race map, this may make the economy better.

The indicated change I'm talking about is about 0.3l/100km each way on my journey - pretty significant really when the car gets ~5l/100km.

Perhaps more striking - I checked my 'long term' indicated average (which works off the last 99.9 hours of driving time I think) and it has reached an all time low of 4.8l/100km. This I put down to the new exhaust I fitted a couple of months ago.

I have noticed that I'm getting an extra trip to work out of each tank nowdays compared with 6 months ago... a round trip being approx 100km. That doesnt mean I'm getting an extra 100km/tank, more like the amount of fuel left in the tank at when before I would have decided to fill it is enough extra to sway me to make one more trip.... the difference may be only 2-3 litres.