Thread: Turbo GT2256V VNT - How to adjust boost?

Check all the hoses and the intercooler for possible air leaks first, and all of the sensor vacuum pressure lines. If air is escaping anywhere you will never make boost.

Additionally, if running an electronic ECU and the MAP sensor is "off" the ECU may cause the waste gate to dump early.

If it is a waste gate problem, it can be adjusted by shortening or lengthening the rod from the actuator capsule if a threaded section is provided for the purpose. Normally OEM ones never need touching (Unless one likes to play )

Alternatively one may purchase a boost adjustment device which plumbs into the waste gate actuator vacuum/pressure line and bleeds pressure from line/capsule delaying opening of the waste gate.

Cheers

RF

being a vnt it wont have a waste gate, but an acuator to adjust the pitch of the vanes.

Make the lenght of the acuator arm shorter will give you more boost.

You should also check for boost leaks and exhuast restrictions.

Also your fuel pump could need adjusting to give it a little more fuel (unsure if they have a similar pump to a tdi)

Boost depends upon a number of things; the resistance to flow (engine volumetric efficiency), the diameter of the impeller, the speed (rpm) of the impeller, and the resistance in your exhaust system after the turbine. Short of a great deal of work you won't change the first two.

Most change the impeller speed. This depends upon available energy in the exhaust gasses (temperature and pressure) available to the turbine.

The energy in the exhaust depends on engine speed and load, and the fuel burning rate.

Boost will be low when the engine speed and load are low. You need to have the engine warmed up, a good load such as a long steepish hill, high engine speed and your right foot all the way down when you want to measure maximum boost pressure.

Your turbo doesn't have a waste gate, so ignore posts about adjusting/etc. waste gates.

Your turbo adjusts the angle of vanes in the turbine nozzle to control the turbine speed. Adjusting the length of the link to the vane mechanism will change the vane angle to increase boost.

IMHO, before you touch the link, fit an egt gauge and increase the simple fuel adjustments on the fuel injection pump.

Originally Posted by Benny_IIA

being a vnt it wont have a waste gate, but an acuator to adjust the pitch of the vanes.

Make the lenght of the acuator arm shorter will give you more boost.

You should also check for boost leaks and exhuast restrictions.

Also your fuel pump could need adjusting to give it a little more fuel (unsure if they have a similar pump to a tdi)

Thanks for the reply, you have answered the most important question i.e. making the actuator arm shorter gives more boost.

I don't have any leaks or restrictions, other than the intercooler!
I have taken off the square air cleaner box/filter which came with the engine and refitted the original round box/filter which I calculated to have twice the surface area.
This gave a noticeable improvement in torque and reduced my exhaust emissions which were already extremely low - at tickover less than the minimum that the machine could measure and now also at the rated speed test. This suggests that my injection pump is running on the lean side.
Also people that drive behind me say that I never have any black smoke even on hill climbs when I change gear.
But because maximum torque is at 1400 rpm I never need to pull high revs and rarely floor it, changing up at 2000 rpm usually gives better acceleration.
It does have a Bosch VE pump like a 300 tdi. I am studying the Bosch Technical Instruction for the pump.

Again many thanks for your reply.
Rob

Originally Posted by robm

[snip]

It does have a Bosch VE pump like a 300 tdi. I am studying the Bosch Technical Instruction for the pump.

Again many thanks for your reply.
Rob

Study this doc, it has step by step instructions for tuning the VE pump

http://www.aulro.com/afvb/attachment...6&d=1152411367

Originally Posted by Bush65

Boost depends upon a number of things; the resistance to flow (engine volumetric efficiency), the diameter of the impeller, the speed (rpm) of the impeller, and the resistance in your exhaust system after the turbine. Short of a great deal of work you won't change the first two.

Most change the impeller speed. This depends upon available energy in the exhaust gasses (temperature and pressure) available to the turbine.

The energy in the exhaust depends on engine speed and load, and the fuel burning rate.

Boost will be low when the engine speed and load are low. You need to have the engine warmed up, a good load such as a long steepish hill, high engine speed and your right foot all the way down when you want to measure maximum boost pressure.

Your turbo doesn't have a waste gate, so ignore posts about adjusting/etc. waste gates.

Your turbo adjusts the angle of vanes in the turbine nozzle to control the turbine speed. Adjusting the length of the link to the vane mechanism will change the vane angle to increase boost.

IMHO, before you touch the link, fit an egt gauge and increase the simple fuel adjustments on the fuel injection pump.

Hi John,
I've been doing a lot of research these last few days and what you say is what I had concluded except for one point. I get maximum boost below 2000 rpm depending on load and it stays constant after that. But since the engine is meant to give maximum torque at 1400 rpm I assume that that is to be expected.
I think my exhaust system is OK. It starts off with a 3 inch down pipe and becomes 2.5 inch after the first box with a straighter than standard pipe over the axle which was difficult to line up so as not to be hit by the axle.

As I said in the reply just before this, I think I have a too lean setting on the fuel pump and I will take your advice about fitting an egt guage and adjusting the pump.
Can you recommend an egt gauge?

Many thanks for your reply
Cheers
Rob

Originally Posted by rick130

Study this doc, it has step by step instructions for tuning the VE pump

http://www.aulro.com/afvb/attachment...6&d=1152411367

Hi,
many thanks for this link.
I have seen similar descriptions but without much detail and certainly without the graphs and values given. This is a great.
Only problem I'm going to have is fitting an egt gauge - my manifold doesn't have the convenient access plate that a 300 tdi has.
Cheers
rob

Originally Posted by Benny_IIA

being a vnt it wont have a waste gate, but an acuator to adjust the pitch of the vanes.

Make the lenght of the acuator arm shorter will give you more boost.

You sure it adjusts boost? It adjusts the vanes and yes it brings on boost earlier but not sure about total boost.

I have a GT2256V and to get them to run efficiently and developing power throughout the rev range you need to control the vanes. I see no mention of how this being done. If you are not controlling the vanes you need to be as this will give you the best enhancement in performance. Get an EGT gauge soon though before you start playing with fueling. Digital EGT Gauge with TC-KEGTS Probe [Combo-EGTS] - $87.50 : auberins.com, Temperature control solutions for home and industry