I've run a borrowed Mugen 4-1 for the last couple of races (I posted summary dyno results back awhile) and figured it's time to give it back. So I welded up a 2.25 section from the Comptech 4-2-1 to my resonator, and went to Loynings this morning to see what it did.

SAE corrected WHP was down 6-9 over the entire useful powerband (peak is down from 189 to 180 whp). Mixture was observed to be satisfactory and since the motor had been relatively insensitive to timing last time no changes were tried. Motor is stock internally, with Mugen ECU, Comptech Air Box, B&M FPR, and my 2.5 inch full exhaust system.

I told myself that the Mugen was going back - period, and that I could live with whatever small losses I expected. Hmmm. Hmmm. <checks to see - yeah I am broke already>

In talking with Doug, who runs the dyno at Loynings, I asked about different header designs, like the long stepped primary short secondary 4-2-1's. He said that they were no big deal - they typically just produce a little more torque below the bottom of the powerband and mostly impress drivers who can't keep it on the pipe.

One of the biggest objections I've had to 4-1's is that they give up some ground clearance and are expensive to replace in the event of a now more likely to be damaging off. Not that it would matter much in this context, but the Mugen is noticably heavier because of much thicker tube walls than the Comptech. And forgive me for this: the Mugen looks better than the Comptech - which by comparison looks like a tangle of twigs.

I don't know how other JDM sized 4-1's stack up, but I think that spending more than the Mugen costs for power I can't actually use on the track would have to be justified by other factors like ground clearance, trickness, or doing business with someone you like - all of which are fine.

Scott, who doesn't want to go slower......

 

Have you looked into the DC sports 4-1 (the JDM version, 2.5" collector). Its is very similar to the Mugen but about 1/3 the price.

 

You want real power, if your going to spend the money on mugen, why not go with SMSP? More power, and custom build, for the same price...

 

.....if you liked the m00gen, you'll love the toda.

Ground clearance is like stock. *sigh*

I miss my old toda header.....