997 turbo tuning

[BIG GT2]

apologies as this has probably been asked before but i cant use the search on my crappy phone!
anyway ive got a 2008 997tt engine to fit into my cayman racer after the aircooled motor expired.
a friend said today that the vtg turbochargers have a power/boost thermal limit. any ideas on what these limits are and has anyone swapped to old school kkk turbos? ive got a few of those around or are the vtgs ok up to silly power anyway? it might seem a step backwards but if what i was told is true id rather go that way than have skyhigh inlet temps and boost dropping off through a long race

thanks in advance mark

[gtphile]

BIG GT2 said:

apologies as this has probably been asked before but i cant use the search on my crappy phone!
anyway ive got a 2008 997tt engine to fit into my cayman racer after the aircooled motor expired.
a friend said today that the vtg turbochargers have a power/boost thermal limit. any ideas on what these limits are and has anyone swapped to old school kkk turbos? ive got a few of those around or are the vtgs ok up to silly power anyway? it might seem a step backwards but if what i was told is true id rather go that way than have skyhigh inlet temps and boost dropping off through a long race

thanks in advance mark

It is going to depend on what power you want basically.
- if you keep it standard and upgrade the intercoolers to the GT2RS ones then you would have better power for longer compared to the standard intercoolers on the 997 turbo. Fit a more free flowing exhaust and help with reduced backpressure.
- however, even then you are going to have issues with intake temps and EGTs and octane.
(not sure if you are allowed to fit acqamist system even if you do it just for cooling only but that would help, but will reduce power a little, but then won't trigger the DME as much)

The problem is this - the 997t DME is extremely knock sensitive even without any modifications - you stick in 95 Octane in a 997 gt2 (620ps) and you will be running 50-60ps less. It needs octane. Additionally setting aside IATs, the Exhaust gas temp (EGTs) will trigger reductions in power, as does higher altitude.

Remapping that engine without making other changes and you will have even more issues - knock will come on around 120mph and power reduced. The only way you can mitigate that is running larger housings as in the 997 gt2 (rs) which help reduce the heat and backpressure. They are expensive - retail around 3.8k each. Even then it is not easy.

Personally binning the VTGs and going conventional turbos is the best solution depending on what your power targets are - not difficult to do. There are hybrids (non VTGs versions) that spool as quick now.

You need to think carefully here as you what you do because otherwise it will be an expensive mistake.

James

[BIG GT2]

ive got a aquamist system that i run a water/methanol mix with fitted in the cayman. ill just have to plumb it into the new engine. ill sell the vtg turbos and standard i/c's and upgrade them. im gonna fit my motec to the new engine so will watch for knock on that. better get stuck in now. sounds like any turbo motor, plenty of cold air where it needs to be.
thanks for the info!