Maximum boost pressure for VAG TDI

[mauroper]

I'd like to hear your reccomendations about how high may i go with the boost pressure in my Seat Cordoba TDI 110HP, equipped with the wastegate-type turbo Garret G15.
I read 18psi in VAGCLUB... still... want your opinion.

Considering i want most of this turbo without blowing it, and without willing to have to lower compression in my still pretty stock engine.

Thanks a lot

[pgarner]

dont know about the older 110 engine but the later PD engines were more or less hard wired to a max of 1.7 bar (24 psi) spike, and there were only a very few that were able to get around this as theres 2 boost limits in the ecu. 1 most tuners got around to lift it but then the 2nd was the failsafe, this was the one that caused confusion.


whats does it run standard and whats it running currently ?

[HDi fun]

I have heard of a Gold 1.9 TDi being tuned to over 300bhp with a hybrid turbo, high flow injectors and a custom ECU. Apparently 3 bar boost pressure.

Don't try this at home.

[waynne]

I wouldn't be happy pushing a 110 Tdi to anything over 180 on standard internals.

[HDi fun]

No, nor would I. I think the 300bhp one was significantly altered internally. The base car was the 150bhp

[mauroper]

Unluckily i haven't got a pressure gauge (yet), i believe the original number is around 14psi, with the ECU limiting it to 14.7, so i guess it's around 15 or 16 now, since the chippping i made was relatively conservative, and... i hope "very engine friendly".
I still have some black smoke so i figure i'll have to raise the boost pressure a little bit, and check the injection timing.

[waynne]

How is it going mauroper?

[HDi fun]

Black smoke is often very hard to correct. My car has a particle filter so 95 plus percent of the stuff is removed anyway.

If I notice anything in the mirror under acceleration it's a very slight amount of soot as the boost pressure rises above unity (1 bar). Once full boost is available the smoke disappears completely.

This is probably hard to totally eliminate as you have to burn fuel to make torque and to burn fuel you need air. So increasing the boost at that point will make no difference if the turbo is not shoving out the maximum possible pressure at that point and therefore no boost increase will happen.

It's the transition for those few tenths of a second when the boost pressure changes from being uniform with atmospheric to being positive.

Leaning off the fuelling won't help either as then there will insufficient exhaust velocity to spin the turbo up swiftly.

If you can find a way to increase the fuel pressure earlier in the rev range (never exceed maximum recommended pressure, just let it rise sooner) then you might manage to get the fuel injection cycle completed in a shorter time which might help.

[mauroper]

I will have to face to a special shop where they modify boost pressure. I have already spoken to the manager and will check my config free of charge... if something is to be modified... iw'll see and tell you. However i can tell the smoke doesn't dissapear when full boost is adquired... it is there specially on second gear under full load... all the way until i discharge the pedal... or when redline is reached.

[HDi fun]

Originally Posted by mauroper

I will have to face to a special shop where they modify boost pressure. I have already spoken to the manager and will check my config free of charge... if something is to be modified... iw'll see and tell you. However i can tell the smoke doesn't dissapear when full boost is adquired... it is there specially on second gear under full load... all the way until i discharge the pedal... or when redline is reached.

Gear 2 is likely to be the gear in which some sooting is most apparent. Especially if you engage that gear shortly after moving away from rest. If you're happy with the performance already then just wind down the fuel delivery a little.

Smoke means one thing - not enough oxygen to burn the fuel 'dose' fully.

I know you're thinking of increasing boost pressure but is there any more to be had? Perhaps just get the fuel delivery advanced a bit, by a few tenths of a degree of crank rotation.