Borgwarner Twin Scroll 7670 With Dyno Graph
Based on the numbers David posted, compared to the HTA3076, it's down about 30 ft-lbs at peak torque at 34 psi. Nearly identical HP up top with both turbos falling to 28 psi by 8000 RPM.
I overlayed the graphs in excel, it's about what I would have thought. They lay right over the top of each other on spool. The HTA is running more boost though so it makes more power across the rpm range.
If you could get the EFR 7670 sorted out to hold 40 psi like he did with the HTA3076, it would probably go over 600 HP/550 ft-lbs. The question of interest though, why does the motor seem so reluctant to run that high of boost?
On the dyno charts, they seem to look very similar at a given boost level. That always seems to be the case with TS vs. SS though. The only hint that you can see of improved response is the manner in which torque comes in. The EFR has a bit of an advantage until about 3800 RPM. The HTA takes over from there and looks much more "exponential" on torque ramp up where the EFR builds more linearly. That earlier torque and linear boost ramp should translate into a more torquey feel at low boost and during spool up.
This boost drop is pretty disappointing. A pair of Tial externals shouldn't experience boost taper at that low of boost which leads me to question the boost controller setup. If it can only hold 27 psi at 8000 RPM, fine, but it should have no trouble holding 25 psi from spool to redline if that's the case and yet boost tapers at even the 18 psi level.
I overlayed the graphs in excel, it's about what I would have thought. They lay right over the top of each other on spool. The HTA is running more boost though so it makes more power across the rpm range.
If you could get the EFR 7670 sorted out to hold 40 psi like he did with the HTA3076, it would probably go over 600 HP/550 ft-lbs. The question of interest though, why does the motor seem so reluctant to run that high of boost?
On the dyno charts, they seem to look very similar at a given boost level. That always seems to be the case with TS vs. SS though. The only hint that you can see of improved response is the manner in which torque comes in. The EFR has a bit of an advantage until about 3800 RPM. The HTA takes over from there and looks much more "exponential" on torque ramp up where the EFR builds more linearly. That earlier torque and linear boost ramp should translate into a more torquey feel at low boost and during spool up.
This boost drop is pretty disappointing. A pair of Tial externals shouldn't experience boost taper at that low of boost which leads me to question the boost controller setup. If it can only hold 27 psi at 8000 RPM, fine, but it should have no trouble holding 25 psi from spool to redline if that's the case and yet boost tapers at even the 18 psi level.
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That is certainly the conclusion I think some people are drawing, but I am not sure I agree. It's turning out very good numbers with a solid curve at extremely low boost pressures. Every turbo is a compromise, so its really a question of the best fit for application. I don't know given the choice of the HTA 3076 at 34 psi vs. the EFR at 28 psi if you can really argue the EFR isn't making impressive numbers.
I don't think that Dave could have made the comparison any more perfect without swapping the turbo onto his own car. It just seems to be an issue of excessive backpressure in the turbo design preventing higher boost pressures and limiting the breathing on the top. That isn't necessarily a bad thing if you are good with running the turbo at the pressure it is comfortable with. For leet's intended purposes of road racing... a 28 psi twin-scroll setup that turns ~550 whp is going to be amazing.
I don't think that Dave could have made the comparison any more perfect without swapping the turbo onto his own car. It just seems to be an issue of excessive backpressure in the turbo design preventing higher boost pressures and limiting the breathing on the top. That isn't necessarily a bad thing if you are good with running the turbo at the pressure it is comfortable with. For leet's intended purposes of road racing... a 28 psi twin-scroll setup that turns ~550 whp is going to be amazing.
I am going to go through my data better on Monday or maybe this afternoon when I meet Ben to pick up his car. I may have dyno numbers from the HTA3076 at 28-30 psi, I had to adjust boost pressure so I may have something that low. The EFR was tested, as can be seen by the graph at 28.3 psi of boost. When it was on the Dynapak it was at 30 psi of boost. The numbers I am seeing are directly in line with the Dynapak results given the 1.7 psi difference and 13% lower number estimate I use for Dynojet/Dynapaks.
Dynapak is hub power... and is much less than WHP 10+% easy.
I am going to go through my data better on Monday or maybe this afternoon when I meet Ben to pick up his car. I may have dyno numbers from the HTA3076 at 28-30 psi, I had to adjust boost pressure so I may have something that low. The EFR was tested, as can be seen by the graph at 28.3 psi of boost. When it was on the Dynapak it was at 30 psi of boost. The numbers I am seeing are directly in line with the Dynapak results given the 1.7 psi difference and 13% lower number estimate I use for Dynojet/Dynapaks.
I'm at the shop waiting on Ben.
I pulled up my logs from the HTA3076. The lowest boost the turbo was run at was 30.5 psi peak. On that run the car made 557 whp-500 ft lbs. The car hit 20 psi at 3650 rpm. 30.5 psi was hit at 4079 rpm, at 8,000 rpm the car still had 25.6 psi of boost.
So yes, the EFR 7670 is making good power at 28.3 psi with it's 539 whp/480 ft lbs. It's 2.2 psi of boost down, figuring about 10/10 increase per psi, we'd be at 559/500, just about identical to the HTA3076. Being identical to what some have basically called back yard engineered technology isn't stellar if you ask me. Boost wise the EFR7670 was at 20 psi at 3863 rpm, 28.3 at 4379 and down to 22 psi at 8,000 rpm. All of which are lower/less than the HTA3076.
I would take the HTA3076 hands down, no questions asked over this turbo. Take into consideration the small tube header on this EFR kit and the twin scroll housing. Then take into consideration the HTA3076 was tested on my large diameter runner single scroll .82 a/r housing. It's a no brainer.
The HTA3076 on our new V-band small runner header would spool even faster and the weight savings would be DRASTIC over this kit.
As for me testing the EFR's on my car. 03white posted a dyno sheet of sierra's car losing power up top on the 8370 I wasn't aware of this and was being told that is what is on the car now and it's God's answer to turbos. Looking at that chart is surely is not. With that team though and the engine program no telling what was going on.
I think I am going to stick with the HTA86 after doing this test and see the other results. I think Robert down at Forced Performance has it going on.
I pulled up my logs from the HTA3076. The lowest boost the turbo was run at was 30.5 psi peak. On that run the car made 557 whp-500 ft lbs. The car hit 20 psi at 3650 rpm. 30.5 psi was hit at 4079 rpm, at 8,000 rpm the car still had 25.6 psi of boost.
So yes, the EFR 7670 is making good power at 28.3 psi with it's 539 whp/480 ft lbs. It's 2.2 psi of boost down, figuring about 10/10 increase per psi, we'd be at 559/500, just about identical to the HTA3076. Being identical to what some have basically called back yard engineered technology isn't stellar if you ask me. Boost wise the EFR7670 was at 20 psi at 3863 rpm, 28.3 at 4379 and down to 22 psi at 8,000 rpm. All of which are lower/less than the HTA3076.
I would take the HTA3076 hands down, no questions asked over this turbo. Take into consideration the small tube header on this EFR kit and the twin scroll housing. Then take into consideration the HTA3076 was tested on my large diameter runner single scroll .82 a/r housing. It's a no brainer.
The HTA3076 on our new V-band small runner header would spool even faster and the weight savings would be DRASTIC over this kit.
As for me testing the EFR's on my car. 03white posted a dyno sheet of sierra's car losing power up top on the 8370 I wasn't aware of this and was being told that is what is on the car now and it's God's answer to turbos. Looking at that chart is surely is not. With that team though and the engine program no telling what was going on.
I think I am going to stick with the HTA86 after doing this test and see the other results. I think Robert down at Forced Performance has it going on.
Actually, I have a perfect comparison but will have to wait until Monday, someone remind me please.
I have a dyno run from the EFR at 30.12 psi of boost, the car made...........556/499 ft lbs at that boost level. Crazy how well my guess of a calculation above was on the money! haha Damn rednecks! I will match that datalog to a dyno graph and lay both 30 psi graphs over each other on Monday.
I have a dyno run from the EFR at 30.12 psi of boost, the car made...........556/499 ft lbs at that boost level. Crazy how well my guess of a calculation above was on the money! haha Damn rednecks! I will match that datalog to a dyno graph and lay both 30 psi graphs over each other on Monday.
I briefly looked in the dyno computer while I was at the shop, I don't think a comparison is going to be possible, the 30 psi pull on the HTA3076 was in 3rd gear and it changes the spool up characteristics by a lot.
Ben, nice seeing you again. I'm glad you are happy with the car and wish the absolute best of luck with it. I can't wait to hear the results. Have a safe drive home.
Ben, nice seeing you again. I'm glad you are happy with the car and wish the absolute best of luck with it. I can't wait to hear the results. Have a safe drive home.