Thread: Tdi Turbo and boost .

First up you need a EGT gauge if you havnt all ready, from reading other posts the easy way to go is get a tdi200 exhaust manifold and then source a turbo
cheers
blaze

I would recommend that you don't touch anything if you don't understand it.

As bblaze said, to get the most out of any adjustments you need to know what is going on with the engine. A boost guage and exhaust gas temp guage are essential.

If you do a search there is a lot of info on fuel pump adjustment, which ties in with boost adjustment.

You probably already know this, but as BigJon mentioned, if you adjust the boost you also need to change the pump fueling to get extra fuel in to burn with the extra air, otherwise you won't get extra power.

They go hand in hand.

The little turbo really can jam enough air in for the engine, so a bigger one won't be greatly beneficial.

Better to look at a VNT (variable nozzle turbo/turbine) to get more low end go.
These are on the 2.8L International 300Tdi engines.
You can also get kits with these turbos from the UK, but they are pricey.

Yep, I'd say the same... If you don't understand, leave well alone.

It's not just as simple as changing the boost pressure.

M

Stock boost is approximately 15 psi. It is reasonable to up this to about 18 psi.

They will go higher, but the compressor efficiency will be reducing rapidly and create more heat in the charge air, without beneficial increase in mass flow of air.

The turbo has a waste gate in the turbine housing that is held closed by a spring in its actuator. A hose from the turbo's compressor outlet supplies boost pressure to the actuator. When the boost pressure overcomes the spring preload force the waste gate opens to allow some exhaust gas to bypass the turbine. This limits the boost pressure, prevents the turbo from exceeding safe rpm's and reduces drive pressure in the exhaust manifold.

The boost pressure is adjusted by changing the length of the rod from the actuator to the lever on the waste gate. This increases the preload of the spring in the actuator.

The actuator and rod are not easy to access - they are on the underside of the turbo. The rod screws into the actuator to shorten, but the other end has to be disconnected from the lever on the waste gate before it can be turned. A clip has to be removed from the rod at the waste gate end, then the rod can be released from the lever - may need pliers to pull the rod against the spring force (and to reconnect).

Sometimes the rod has to be shortened by cutting if it doesn't screw in far enough.

Adjustments should be made a little at a time and test driven with plenty of right foot, up a good hill. Naturally you need a boost gauge to measure the results.

Because the turbine is driven by the exhaust gasses, more fuel will produce more higher temp exhaust gas and produce more drive pressure.

If the boost pressure is not going up enough, it may be necessary to increase the fuelling, but check for restrictions inside, or leaks from the compressor inlet and intercooler hoses first (also oily muck inside the intercooler).

Increasing boost pressure should not increase egt, but increasing fuel will if there is not enough air provided.

300Tdi's are prone to blowing head gaskets, particularly if they have overheated or even with large km on the clock. Increasing boost pressure on a 300tdi with a poor head gasket may just be the straw to break it's back.

If the turbo is not in good condition (eg. worn bearings), it will die quicker if the boost is increased.

The performance of the stock turbo can be improved by having the compressor high flowed by a turbo shop. This is the cheapest upgrade.

John,
Ive heard of the high flowing - what is it that they do?
And any ideas on a good place that may do such a thing and rough cost estimate if you have it?

I have a spare turbo/manifold... so time wouldnt be an issue.

Steve

basically they shape the housings to ensure correct airflow onto the wheels with minimum interfereance.

A bit like a port and polish but trickier not overly benificial on a high performance high quality unit but you will be pleasantly surprised at the difference it can make to smaller cheaper units.

I have pretty much decided to fork out for the Allisport upgrade when I have the dosh

They give you a manifold, turbo, hoses and intercooler if your interested

Somewhere above the 2 grand mark is about the price

Thats for a VGT turbo as well

rijidij has this setup on his 130