So do we think the introduction of the new GT2 will mean larger VNT hot sides for us to use?

Rick.

 

they may be larger but if the predecessors are any indication of price they will be very expensive. 6k + for the pair.

 

I hope that they have gone one step further and introduced wastegates as on the new Boxster S. VTG with wastegate is really nice since you can remove some exhaust flow from the turbine and thereby allowing the VTG vanes to be set at a position for best turbine efficiency. This gives lower back pressures for a given boost level, and with the data Cobb provided us here with back pressure over boost on 997.1 TT I think we all understand that it is not optimal as it is. Also the data from BorgWarner with this technology says alot of its potential (I am not sure if it is official and what I can share).

I had plans to add wastegates to my 7.1TT with stock turbos, but have now built a new K16 based EFR 7163 setup so I think I dont have the energy to do that test even if I am quite curious about the result. I hope that someone here tries it! (I am running Syvecs so I have the possibility to control this quite easy).

One other feature that Porsche might try (or that someone here should) is to add a tube between the exhaust manifolds. This could be closed of with an exhaust cut-out throttle or similar. The idea is at lower engine speeds the turbos generally like the pulses to spool the turbos. But ones they are up and running these pulses actually choke the turbine and if they could be damped overall turbine efficiency would increase. This means same boost with less exhaust back pressure. I think Mercedes F1 uses log style exhaust manifold and this is the reason. Also all trucks where efficiency is key. With the active valve between them we could have both - spool and efficiency!

 

I think it will be a good combo when leaving some of the compressors potential on the table. I am looking at sub 1000 hp at the crank, i.e. sub 500 hp on each turbo.
The K16 housing is quite big and when I compare it to other K16/K24 OEM units it uses a quite big turbine for its compressor size.
Also, the housing size (in cm2) is quite comparable to what BW uses for their 7163.
We have machined the housings quite alot and made an adapter plate for the CHRA to fit in the K16 housing. The much larger diameter of the 7163 turbine will also allow for usage of a "small" housing w/o adding excessive back pressure (hopefully )

I was reluctant to use K24 since they seems to add way more lag compared to K16 and from my 996 period, (I wanted to buy one but they got so expensive here in Europe so I bought a 997 instead) the upgraded K16 seemed better than upgraded K24 in overall performance.

Also, the mixed flow turbine on the 7163 intrigues me and some data I have seen (Perrin blog, Subaru testing), low end performance is acutally better than the smaller EFR turbos.

Best regards
Erik

 

That sounds great! Is that when you reach your peak boost?
Do you have any log that you can share from 1500 rpm third/fourth gear pull? It would be interesting to see when they come on some boost and when they reach "high" boost. Also, wastegate control of interest (i.e. if the wastegate is forced shut or not). I dont have any logs since they are not mounted yet

I do not want 500 hp from each turbo below 3000 rpm, but some boost would be nice and then ramp it up as engine speed increases. I am not that impressed with the VTGs actually and many people says that they get better response with an aftermarket turbo w/o VTG. It would be nice with some boost from low engine speed and then I can decide how much is allowed. (I also had the K16 housing laying around - new!)

BR
Erik

 

3500 for boost to start is late, t makes the car feel lazy. Changing down a gear looses time. It is ok for highway type pulls but not too good on say the Nurburgring.

Wastegated turbos with VNT would be nice, I could get the 7.1 ECU to control that.

Rick

 

991.2.TT/S turbos may possibly be same with GT2RS. will get more info soon

 

The new turbos are VNT and electronically controlled combined with liquid cooled intercoolers.

I doubt they will work with 997 DME

 

Made few corrections.

BTW, They can be made to work in a 996, though not with ME7.8, but external controller. How would I know...

 

VNT/VTG are the same thing, just different jargon.

 

Of course it is always possible to make 991 GT2RS turbos work on a 997tt. At the end of the day everything ist possible.

The Question ist, whether it makes sense spending some grands just for the conversation in addition to new VNT turbos, which I expect also to be on the high end.

 

Most likely bolt-on. If factory has been really nasty, new flanges for exhaust. Some tuning for Motronic.

Bigger hotsides, more tuning potential. So far hotside (or lack of bigger ones) has been the limiting factor in extracting power out of VTG equipped 997 turbos.

 

Upgrading 997t turbos costs 2000,- with max. 700HP
Upgrading 997 GT2 turbos makes 800HP possible.

So. why should i get the 991 turbos?
Upgrading the old turbos plus the 4.1 liter cylinder kit makes more sense to me...

https://www.fvd.net/us-en/100103041T...o-gt2-911.html

 

I think they are just keeping the throttle open with a selective fuel cut off pattern rather than spinning them electrically but I'm not 100%

I have already done something very similar for 6/7.1 - but have never bothered tuning it - you loose engine braking so it feels quite strange!

 

Looks like you might be ordering a set of these then lol!