FP Black MHI vs SS Housing
Former Sponsor
Joined: Jan 2018
Posts: 67
Likes: 44
From: Johnson Creek, WI
We don't want to stray too far off but wanted to clear things up a bit.
We won't speak for other fabricators and product, but can speak to ours.
It's certainly not just the smoother formed transitions, but we are sure they were in our favor for the results. The factory turbine flange footprint can make for a tough transition without forming the merges, and the location/placement causes many (non-cast) runner layouts to have a very tight and/or cheated bend radius off of the #3 port. Both of which we overcame without compromise, and the formed oval port runners off the flange are a given.
Without tune adjustments, and after only swapping to our manifold while still on the dyno, the car leaned out quite a bit. It actually made a little more power than stated in the article during those first initial (leaner) pulls. After the AFR was back in line, the power % difference tracked well with the initial % AFR difference and fuel requirements, as it should with higher VE (the car is speed density). Unfortunately, a drive pressure/EMP sensor wasn’t installed, but when the same wastegate duty cycle was commanded, actual boost was lower but it still made more power- both indicating lower EMP.
The back-to-back dyno was 3rd party, and was as thorough as possible as covered in our write-up/article. A huge thank you to Yusuf and Geared Up Motorsports for taking an extra long day to do the testing.
Turbo cars are extremely tolerant to unequal length runners, this isn't a naturally aspirated engine where turbulence in the exhaust ruins exhaust scavenging and hurts power. I respect their dedication to being thorough about their products but the fact is really any manifold will outflow an MHI housing. The only differences are really going to be in runner diameter which would affect spool. The MHI stuff also doesn't really mind much in regards to collector angle because the volute doesn't start in the housing until you're about 3-4" down past the flange or so, a fair bit steeper than most turbine housings.
I'm not spouting garbage out of nothing either, I have a degree in automotive engineering and have spent more time using flow benches and consulting flow bench experts than anyone here short of some guys who use them for a living.
For the typical factory runner lengths of a turbo car to begin with, we agree that length variances don’t have as much of an affect on power. And certainly don’t want to throw “equal length” around like a buzz word. We do like to have things equal length when possible, however, to help minimize cylinder to cylinder VE/fueling requirements and subsequent leaner and richer cylinders. Especially when we don’t have to “go out of our way” to do so, and when the length (depending on configuration and application) becomes more critical to some possible pulse tuning effects. Having AFR variances across each cylinder, dependent on rpm, is something turbo cars aren’t as tolerant of. Take this for what it is, but it was reported that after the initial cast manifold runs, cylinder #1 plug indicated leaner than the rest (despite the higher flowing injector purposely placed in that cylinder) that no longer showed lean after the runs with our manifold.
Touching on the runner diameter, we intentionally chose the smaller primary size in order to better match the flow capabilities and characteristics of bolt-on options out there. Our goal was to obviously make more power than a factory ported manifold but also without giving up much (if any) spool and response.
We feel that the angle of entry at the collector was one of the larger factors in the results. Instead of the somewhat flat cast collector that partially points the paired runners at each other, each runner is pointed directly at the volute and turbine itself. Our collector also mimics the volute angle of entry into the turbine housing, which isn’t actually perpendicular to the flange. We don’t know of any other manifold offerings out there that do this.
This was an FP SS turbine housing by the way, and it should be noted that the test was in comparison to a ported FP Race manifold- not a factory manifold. Which both work very well to begin with.
For the original post, we feel that Abacus nailed it. The SS housing will make more power and allow the stock frame turbo to be pushed quite a bit harder (Stock appearing class), but the MHI housing makes for an astounding powerband. Near 500wtq at 4000rpm and practically 650whp from a 2.0 proves that. It comes down to preference and what path makes the most sense from where you are now.
We won't speak for other fabricators and product, but can speak to ours.
It's certainly not just the smoother formed transitions, but we are sure they were in our favor for the results. The factory turbine flange footprint can make for a tough transition without forming the merges, and the location/placement causes many (non-cast) runner layouts to have a very tight and/or cheated bend radius off of the #3 port. Both of which we overcame without compromise, and the formed oval port runners off the flange are a given.
Without tune adjustments, and after only swapping to our manifold while still on the dyno, the car leaned out quite a bit. It actually made a little more power than stated in the article during those first initial (leaner) pulls. After the AFR was back in line, the power % difference tracked well with the initial % AFR difference and fuel requirements, as it should with higher VE (the car is speed density). Unfortunately, a drive pressure/EMP sensor wasn’t installed, but when the same wastegate duty cycle was commanded, actual boost was lower but it still made more power- both indicating lower EMP.
The back-to-back dyno was 3rd party, and was as thorough as possible as covered in our write-up/article. A huge thank you to Yusuf and Geared Up Motorsports for taking an extra long day to do the testing.
Turbo cars are extremely tolerant to unequal length runners, this isn't a naturally aspirated engine where turbulence in the exhaust ruins exhaust scavenging and hurts power. I respect their dedication to being thorough about their products but the fact is really any manifold will outflow an MHI housing. The only differences are really going to be in runner diameter which would affect spool. The MHI stuff also doesn't really mind much in regards to collector angle because the volute doesn't start in the housing until you're about 3-4" down past the flange or so, a fair bit steeper than most turbine housings.
I'm not spouting garbage out of nothing either, I have a degree in automotive engineering and have spent more time using flow benches and consulting flow bench experts than anyone here short of some guys who use them for a living.
For the typical factory runner lengths of a turbo car to begin with, we agree that length variances don’t have as much of an affect on power. And certainly don’t want to throw “equal length” around like a buzz word. We do like to have things equal length when possible, however, to help minimize cylinder to cylinder VE/fueling requirements and subsequent leaner and richer cylinders. Especially when we don’t have to “go out of our way” to do so, and when the length (depending on configuration and application) becomes more critical to some possible pulse tuning effects. Having AFR variances across each cylinder, dependent on rpm, is something turbo cars aren’t as tolerant of. Take this for what it is, but it was reported that after the initial cast manifold runs, cylinder #1 plug indicated leaner than the rest (despite the higher flowing injector purposely placed in that cylinder) that no longer showed lean after the runs with our manifold.
Touching on the runner diameter, we intentionally chose the smaller primary size in order to better match the flow capabilities and characteristics of bolt-on options out there. Our goal was to obviously make more power than a factory ported manifold but also without giving up much (if any) spool and response.
We feel that the angle of entry at the collector was one of the larger factors in the results. Instead of the somewhat flat cast collector that partially points the paired runners at each other, each runner is pointed directly at the volute and turbine itself. Our collector also mimics the volute angle of entry into the turbine housing, which isn’t actually perpendicular to the flange. We don’t know of any other manifold offerings out there that do this.
This was an FP SS turbine housing by the way, and it should be noted that the test was in comparison to a ported FP Race manifold- not a factory manifold. Which both work very well to begin with.
For the original post, we feel that Abacus nailed it. The SS housing will make more power and allow the stock frame turbo to be pushed quite a bit harder (Stock appearing class), but the MHI housing makes for an astounding powerband. Near 500wtq at 4000rpm and practically 650whp from a 2.0 proves that. It comes down to preference and what path makes the most sense from where you are now.
