A small header project

[Tomi]

My new header eneded up being so good I decided to do a little write up on it. The engine is 88x101.6 with Scat case, JPM MS230 heads and JPM custom roller cam. On summer 2011 I had a 4-2-1 header to save space and be somewhat invisible, sizes and lengths calculated with Pipemax software. I thought it was OK but apparently it wasn't.



The result was 170 kw at the wheels and at 6800rpm. According to the cam specs the peak power should be above 7200, so there was definitely something wrong. After some discussions with Johannes he sent me new specs for the header and suggested 4-1 header instead of 4-2-1. The problem was I wanted the header to be hidden and not facing backwards as the car is a street car and I don't like the collector to hang out at the rear and stingers are not for me. Dry sump pump also added the complexity so some kind of compromise was needed. Luckily I have a tech nut friend working at local university of arts and he promised to help. He made a cad model of the engine and knowing the pipe lengths spent hours getting them fit.







After that we used university lab's equipments to cut the bends and pipes, and my friend started weld it all together.







I managed to fit a muffler there as well to keep it "quiet". The header does not hang too low, the lowest point from fround is 13cm.






It took us nearly 3 months with slow pace to get it all done but it was really worth it. Last friday I had only 1 hour to spend at the dyno so not much time for fine tuning. Without any other changes the power went up to 185kw @ wheels @ 7100rpm, with the fan belt and muffler on. That's 20 horsepower with the change of header only. With some more tuning it could even get better.

I can only thank Johannes for specs, the engine is now much closer to what it should be.

[MarvelTyler]

Wow, that really is some work there. Nice one.

[BeetleBug]

VERY interesting and thank you for sharing Tomi. Brilliant pictures as well! I hope 2012 will be the year when you will bring it to SCC. And also Turbo Town Shootout at Kjula on June 8-10 is well worth the boat ride. Kjula offer a well prepped track with excellent traction.

Best rgs
BB

[richie]

tomi,

very interesting project,did the exhaust analizer specify the increase in size of the primary tubes? and at what length to increase them? or was that for another reason?

cheers richie

[Tomi]

The 4-2-1 header was initially calculated to be used with a different, milder, cam. For the JPM roller I just made some changes to it. Pipemax calculator gave all the sizes and lengths and I didn't question them at all. It is much easier to make 4-2-1 header and that's why I still kept with that design.

Obviously that header did not work well as a package with new cam and improved heads and that's where Johannes came to help. I did no own calculations for the new header, Johannes gave me the specs and yes, the size of the pipes were completely different from the old one. To me this clearly shows what a difference a well designed header makes. I don't have idea if rear facing header would be even better if all other things, such as tube sizes and lengths, are kept equal.

Kalle, Kjula is definitely too soon. The drive there is shorter than to my summer cottage so I would love to go there some day. Is there something in september also? SCC is not out of question, I just hope the car is still in OK when the time comes. 

[richie]

What I meant was I can see in the pictures the tube size seems to increase as it gets further from the head flange,looks like 3 steps,is that part of the design or just soemthing that you did for fitment reasons? and if it is needed,how do you calculate how long each section needs to be before going up a size?

cheers richie

[Tomi]

OK, now I understand the question. Both headers have three different size pipes and they are not for fitment reasons. Pipemax gave the steps for the 4-2-1 header and it was tuned for milder cam, hence the loss in horsepower. Johannes on the other hand gave exact lengths for different size pipes for the 4-1 header. I don't know the formula for calculating the sections but software like pipemax is very good in that. And the more you know about your engine the better results you get.

[richie]

Hi Tomi

thankyou,something new I learned,now I just need to study some more to see if I can gain anything from it as well

cheers richie