Just a Couple Headers and a Slow FT-86: Skunk2 EL vs Tomei UEL

Now I want to get into this and say that I was not in any way displeased with the Skunk2 Alpha race header on our Scion FR-S — the power pick up over stock was significant, and I expected it to maintain a bit of a torque dip being it is of equal length design and we see that dip remain in some form with all the equal length headers.

I have been running this header since it came out on the platform and after helping a few customers with their Tomei unequal length race headers, it really peaked my curiosity and I wanted to do a legitimate comparison. None of this “open two dynos from two different cars” as is so common with the vast majority of “comparisons” being done. It opens a can of worms and seemingly endless debate about this and that.

Some information about the parts and vehicle as it sits now. After spending countless hours testing and tuning the car using ECUTek (which I still offer for customer cars), I have switched it to a MoTec M1 stand alone ECU for it’s advanced features and ability to rapidly tune new configurations on the vehicle (no more “Flash and Wait” — given this car is a test mule, this saves countless hours on R&D and as they say: time is money). This comparison is done with both configurations tuned on the MoTeC.

Other relevant information:

  • Skunk2 Intake
  • Perrin 3″ Exhaust
  • Perrin Over Pipe
  • HKS Front Pipe
  • E85 fuel

The use of E85 fuel makes the vehicle much more consistent and the comparison much more reliable — the correction factor used on a dyno gives you an “estimate” to compensate for weather differences, but it is only an estimate. The use of E85 ensures the motor is able to be run at MBT for ignition timing even if we have a temperature swing — something that cannot be said of 91-93 octane pump gas. From my tests on this vehicle I found a whopping 1hp difference from running E85 in 40*F weather vs E85 in 90*F weather while tuning on the Dynapack. This helps aid in the consistency of the test. With pump gas a pull used for comparison that was done in 40*F can and will make a fair bit more power than a pull done in 90*F, so you really have to be careful when doing parts comparisons on pump gas which can just lead to more debate. That being said, even with the E85 fuel, I went to great lengths to make sure the conditions were pretty much identical between the two tuning sessions.

My Expectations

With the swap to an UEL race header it goes without saying that I expected to flatten out the torque in the area where the dip remained with the EL race header. However, I was also expecting to lose out on top end as this seemed to be the “expected” results between the two styles of header. And so I was about to find out how true this was… Bearing in mind the Skunk2 Alpha is a header I’ve been running for 9 months through many tuning sessions where I’ve eeked out everything there is to be had on this setup.

The Results

So without further ado — the test was simple. The vehicle was fully tuned in great detail with the existing setup — all fuel, timing and cam timing dialed in. As soon as the Tomei UEL was delivered it installed after the Skunk2 was removed and the car went right back on the dyno for more tuning.

skunk2_vs_tomei

I was indeed partially surprised by the results — the story is that EL should have better top end? Doesn’t look like it’s even remotely an accurate statement as not only did the UEL match the EL, it carried torque much better up top and didn’t drop off as soon. The mid range also filled in significantly and the low end was no worse than the EL — unless you count the blip at 2600 rpm. Which I don’t, as that blip is literally nothing more than a blip and I can assure you from driving the car with the Tomei on it, you won’t ever miss that blip, it’s like it doesn’t exist.

For the curious, the data from the two runs (which were about 5 days apart) demonstrates the weather conditions were virtually identical (RemoteTmp, Baro & RelHum).

skunk2_vs_tomei_2

 

Conclusion

This was an interesting test, and I’m happy I could fit it in before the car gets torn down for our turbo kit build — yet there are many more items I would love to test. It would definitely please me to have a full “header comparison” database for this vehicle — if I could borrow every header and take a week to test them all out, I would.

As it stands now — the car makes more torque than it did horsepower in stock form, which is quite amusing.

stock_vs_tomei_uel