Problems with my Twinscroll Turbo - Please help :)

[Tiz]

I live in Europe where we have less experience with (twinscroll) turbo setups. Therefore, I would be grateful for your thoughts:

My AT car has a 480hp rated GTX2867R (/w 0.82 AR twinscroll housing) but does not make enough top end power. It makes only about 350-380 hp (with high intake temps on the dyno) @ about 17 PSI using 93 octane. However, it generates torque and hp very early. About 300hp/ approx. 260 lb ft torque at 3300 rpm. About 9 PSI @ 3000 rpm. Highflow metal cat. Tomei Type 80 exhaust.

By contrast, my tuner has an MT FR-S that makes approx. 440-450 hp / 360 lb ft @ 17 PSI. This car uses a HKS 3040 turbo (/w a relatively small 0.76? AR twinscroll housing). Moreover, the car uses a header with a larger diameter and, probably, race cats. Tomei Type 80 exhaust.

(Btw.: My well-recognized tuner is still working hard on my car and there is no reason to complain. But I would like to do my own research or, respectively, hear your thoughts. I have converted the European number into US numbers (e.g. nm into lb ft). Probably, the measured numbers are not whp numbers but were already converted/standardized to crank hp.)

Now my questions:

1. What hp rating would you expect from a GTX2867R? At what PSI?
2. Why is it so difficult to achieve the rated 480 crank hp (or at least 400-450 hp) without using race fuel? (My Subaru STI made 490-500 crank hp on 93 octane using a 525hp rated GT3076R.)
2. Is there any reason why an old HKS 3040 would make more power/is easier to tune/produces lower intake air temps than a 2867R?
3. Do you know what diameter FRS twinscroll headers (for high hp applications) normally use?
4. Does an AT suck much power?
5. Any other thoughts?

Many thanks!

Tiz

[Kiske]

What fuel type, fuel pump and injectors are both cars running? Are both cars running the same kit?

[Tiz]

Fuel type: Standard European super plus fuel. More or less identical to US 93 octane fuel. Injectors and fuel pump should be identical (although I will reconfirm this matter with my tuner).

Both cars use the same built engine (compression 10:1).

Both cars differ because the tuner's car is using a different turbo and a larger diameter header. Moreover, I expect the tuner's car to use a metal cat with less cells. (My car uses metal cats with 200 cells.) In addition, the tuner's car is a MT and not an AT.

Addendum: I understand that the HKS is only slightly larger than the GTX2867R. Moreover, it seems that max. air flow of the 2867 is about 48 lb air/min. The HKS should make about 52 lb air/min if I correctly understand these figures: http://www.clubwrx.net/forums/engine...olume-etc.html

[cdrazic93]

Auto takes more % drivetrain loss than manual. Race cats are a myth; race cars don't need catalytic converters. At a certain level the fuel limits the power made on any turbo. 93 pump gas can only make so much xxx hp on any psi. @woode made 412 hp on 21 psi on 93 gas.

[Tiz]

1. Thanks for the link. What I do not understand is why the HKS 3040 makes more power with the same type of fuel. My cars lacks about 80hp.

2. Racers do need cats in Europe. Moreover, the max exhaust noise is frequently regulated. But this is off topic anyway.

[cdrazic93]

Originally Posted by Tiz

1. Thanks for the link. What I do not understand is why the HKS 3040 makes more power with the same type of fuel. My cars lacks about 80hp.

2. Racers do need cats in Europe. Moreover, the max exhaust noise is frequently regulated. But this is off topic anyway.

After a slight bit of researching the 3040 has the same spec wheels as the gt30xx from Garrett. That's why its out performing you. I'm assuming you get much better spool?

[Tiz]

Originally Posted by cdrazic93

After a slight bit of researching the 3040 has the same spec wheels as the gt30xx from Garrett. That's why its out performing you. I'm assuming you get much better spool?

Can you please share your results? There are various different GT30xx turbos. For instance, the GT3076R makes quite a lot hp. The GT3067 or GT3071 make less hp. According to my research the HKS 3040 is similar to a 500hp GT30 and only slightly larger than my 480hp GTX2867R. Consequently, I would not mind the HKS to make 20hp more than my GTX28. But the difference should not be 80hp. In particular, this is because the spool of the HKS is still pretty good!

[Kiske]

3040 seems to be =)ish) to the GT30 56trim.

This may help it is a comparison between the gtx286r/gtx2867r/gtx3071r with debate. http://www.ft86club.com/forums/showthread.php?t=57370

[Tiz]

Thanks. It seems to me that other cars also achieve roughly the same power level on pump fuel.

It puzzles me why it is so difficult to further increase the boost on the FT86 engine (even with lowered compression)? My Subaru WRX STI made almost 500hp @ 93 octane @ 23 PSI using a GT3076R rated at 525 crank hp.

[Dipstik-sportech]

Twin scroll turbos are known to lose top end power due to the restriction due to the exhaust housing, it's a trade off for the earlier spool. Is it dropping boost at high rpm? Do u have a manual or electronic boost controller? My single scroll 2871 lost 2psi from 6900-7500 but when we went to an electronic boost controller we were able to compensate for it.

Is your tuner saying it's the boost that's holding u back? Or is it other factors like knock?

[Tiz]

Tuner is afraid of high intake air temps (at least on the dyno): 140+ degrees Fahrenheit. He tried to increase boost to 18 or 19 PSI but had to adjust timings. Consequently, the crank hp did not get higher than 370hp. Tuner is afraid to increase boost even more (whilst the car is running on 93 octane). Tuner also says that the hp is higher on the road due to lower intake air temps: 98 degrees Fahrenheit

By contrast, the twinscroll HKS makes almost 450 crank hp @ 17 PSI on the dyno. Seems to be easier to tune. The spool is still good.

[Dipstik-sportech]

Does it make that same HP on the same engine? What are your intake temps? Does he have a fan blowing on the intercooler? How many back to back runs have you done? Could it be heat soaked? Is the hood open during the runs? So many variables. 370whp on 93 octane on a twin scroll 2867 isn't bad through an auto. On e85 they max at 450whp and that's a single scroll on a manual. This proves my theory that these cars don't need a twin scroll, my 2871 made full boost by 3000rpm, any sooner and you'd just spin the tires anyway

[Tiz]

Originally Posted by Dipstik-sportech

Does it make that same HP on the same engine? What are your intake temps? Does he have a fan blowing on the intercooler? How many back to back runs have you done? Could it be heat soaked? Is the hood open during the runs? So many variables. 370whp on 93 octane on a twin scroll 2867 isn't bad through an auto. On e85 they max at 450whp and that's a single scroll on a manual. This proves my theory that these cars don't need a twin scroll, my 2871 made full boost by 3000rpm, any sooner and you'd just spin the tires anyway

Thanks for the input.

Same engine: Same type of engine and identical rods (lowered compression). But two different cars.

Intake temps: See above. I have amended my post and included the numbers.

Blower: Yes, there is a blower. We will try to put a larger turbo on my car and make more dyno runs.

It seems to me that my hp figures are not bad (i.e. other forum members with a GTX2867R do not make more power on pump gas). But this also means that this turbo's hp rating (480hp) cannot be achieved on pump gas. At least not with our cars. That's disappointing because my Subaru WRX STI could (almost) reach the max. rated hp of a GT3076R on pump gas.

I was planning to use a 23 PSI map on my car. But this seems to be impossible if I use a GTX2867R...

[Reaper]

On e85 (105 octane) I had similar results. Tons of low end torque and lost a bit on the top end. The single scroll doesn't like going over 18psi. I'm sure the twin scroll is worse. I made 450+whp with the turbo maxed out on 105 octane at 18psi so it sounds like you're not too far off. Theres a local car near me making the same power as you with a similar sized turbo at lower compression on 93 and having ait issues as well.