[Lotus Esprit GT1]

This is is my first post on the forum, so please be patient with me.

I have a project car that I have been working on for some years. In its been based around chargecooling a Lotus Esprit V8 and moving to a full Motec M800 ecu/ADL set-up. Currently, it is developing 450bhp at 10psi.

My reason for posting is that I plan to move to a single turbo set-up, instead of the existing T28/25 hybrids. The engine is a 3.5l and I?m seeking some guidance on the correct GT-K selection. My goal is for 550bhp, but I do not want to run very high boost in order to acheive it. I would like to have some room to manouver and hope that the smaller turbine A/R will help with decent spool-up.

My greatest hope is that the move to a ?latest generation? ball bearing design will give me a good combination of fast spool and a cool efficient flow at relatively low pressure ratio.

Do you have any recommendations?
Mike S

[Robert]

Initially based on displacement of 3.5L I would be looking at the GT-K 550. It uses a GTK61 compressor wheel which is more than capable of producing your desired levels. It uses a F1 T3 Stage 5 turbine which is an improved version of the turbine I currently run on my 3.5L 350Z motor. On my motor with a .77 A/R and older desgin I see a full 8 PSI of boost around 3300-3500 RPMs. The GT-K 550s turbine is far superior to mine in terms of blade count, wheel design, etc. The GT-K 550 uses a .82 A/R which should give just as good of a spool up without any issues on the top end. I'm a little concerned because you have a V8 that it might choke the turbine housing on the top end but with a .82 A/R you should be ok. The other option would be a GT-K 650 however it uses a larger turbine and compressor wheel. Its capable of far more power but is over kill for your purposes. In the end I think you will be very happy with the GT-K 550 for your project.

[Lotus Esprit GT1]

Thanks for the swift response and comparison on your 3.5L Z (very nice car).

I really don?t want to run more than 1 bar boost. With the GT-K 550, wouldn?t it be necessary to run higher boost in order to get the necessary airflow for my power goal?

If I went for the 650 variant instead of the 550, how much later would I expect to see 11-12 psi?

I know that there is a significant step-up in turbine size, but the A/R is still fairly small.

There would also be the chance to extend my power output if I felt it necessary, which would not be the case with the 550..... What do you think?

Cheers,
Mike S

[Robert]

Originally Posted by Lotus Esprit GT1

Thanks for the swift response and comparison on your 3.5L Z (very nice car).

I really don?t want to run more than 1 bar boost. With the GT-K 550, wouldn?t it be necessary to run higher boost in order to get the necessary airflow for my power goal?

If I went for the 650 variant instead of the 550, how much later would I expect to see 11-12 psi?

I know that there is a significant step-up in turbine size, but the A/R is still fairly small.

There would also be the chance to extend my power output if I felt it necessary, which would not be the case with the 550..... What do you think?

Cheers,
Mike S

Yes on the GT-K 550 you might need a bit more boost pressure then 1 bar to make your goals. The GT-k 650 is a larger compressor so you should make the same power level at lower boost and of course you also have the potential to expand power output. I don't think you'll see full boost much later with the F1 P trim but it would be a little bit slower...

[Lotus Esprit GT1]

Cool.

I think I?ll opt for the GT-K650 then.

I can see that it has been asked before, but when do you think there will be some compressor maps available for this family of turbos?

Thanks for your insight.

Mike S

[Robert]

Originally Posted by Lotus Esprit GT1

Cool.

I think I?ll opt for the GT-K650 then.

I can see that it has been asked before, but when do you think there will be some compressor maps available for this family of turbos?

Thanks for your insight.

Mike S

I honestly wish I had a good date to give for the compressor maps but Turbonetics has not yet released anything in the form of a date for their publishing. I assure you the minute they are available I will have an announcement posted here with the maps attached.