4-1 vs. 4-2-1 dyno comparison

Just got back and the results where rather impressive. As I said, I tried to make this as close to an actual header v header as possible. The dyno was done on a Mustang dyno which typically reads about 15% less than a Dyno Jet. The tuning was done first on the Nismo header and then 30 mins later (after the swap) we redyno'd the car with the DC style header. Both have very similar 2.5" custom mid pipes with no cat.

First I would like to thank the great folks - Derrick and Dave - at Lethal Injection. If you are close to Atlanta, check them out. They have an in house machine shop and have completed some b16 crank/rod swaps into B15s with great success. Cool bunch of guys. It took us about 3 hrs to get this wrapped up and they were very cool about all of it.

Here are both headers:

And here is the DC Style with the custom mid pipe:

OK - first, tuning the SAFC with the Nismo header. We tuned the AFR to 13.2 across the board then dropped it to high 12s past 5400 rpm b/c we noticed only a difference of 1hp/1tq. And I drive @ WOT all the time, a little richer was safer. The dip in the AFR on the untuned @ 4300 was the LM1 freaking out for a split sec. We later swapped it out for a newer one.

The car only picked up 2wtq and 4whp tuned. For a peak of 163wtq / 152whp or 187wtq / 175whp per a Dyno Jet (estimated). Thats est. 224.9 crank tq and 210 crank hp.

Then we installed the DC style header and custom mid pipe:

And the results....?? not so great. The car lost 6wtq and 4whp.. everywhere. It didnt perform like anyone thought it would. Maybe it has too little backpressure and not enough scavenging. I dunno. The car sounded different - not as fast and quieter. I thought I would see some gains somewhere. Nope. We ran the dyno again and repeated the results.

Here is the tuned Nismo v the DC/AEBS style. The Nismo is the dotted line. We even raised the AFRs on the DC header to 13 across the board. Nothing.

And to make matters worse, the DC/AEBS makes less power than the untuned Nismo. The untuned Nismo (our baseline) is the dotted line.

The modification done to the 4-2-1 header:

I did exactly as suggested and made a custom 2.5" midpipe (I'll post pictures) with my 4-2-1 header. I suggest everyone do this. Look what I found where the 2 goes into 1. The piping is 2 1/4, but with this restriction, it drops to 1.5. I cant believe this crap. I have a dyno session scheduled for Thur to compare the Nismo to the 4-2-1. It will be apples to apples since the mid pipes are both 2.5" similar custom designs. No cats. So its truly the header that will show a difference.