Another 240SX header question

Ok, I'm about to re-do the exhaust from the header back with 3" tubing and wanted to ask you guys one thing - are you coming right off the collector with the larger diameter tubing, or are you gradually stepping up to it? The reason I ask is that I read an article on S&S's webiste that says in part

the collector outlet diameter only needs to be 20% larger than the primary tube diameter. (Example: 1 3/4" primary tubes need a 2" collector outlet diameter.) The rule of thumb here is two tube sizes. This keeps the velocity fast to increase scavenging, especially at lower R.P.M.s. Going to a larger outlet diameter will hurt the midrange and low R.P.M. torque. The amount of straight in the collector extension can move the engines torque up or down in the R.P.M. range. Longer extension length will pull the torque down into the midrange.

this makes me wonder if maybe I should be running a short section of 2"-2-1/4" tubing off the collector and then stepping up to 3". But then again, this may be more geared toward street applications, and may be all wrong for our motors. So, I thought I would ask you guys what you're doing, and how well you think it works.

Thanks.

I have mine dumping straight into the 3" pipe. My car pulls hard from 1500-6300 with no issues and no aftermarket programing.

The only thing I will change next go round is to get it further over and under the transmission more. The floor board on my car is brutal, I have a blister on my heal after a day at the track. That makes the enduros quite uncomforatable.
Hope this helps,
Carver

Most of the guys run a straight 3" inch pipe. The 12 valve motors need to breath. And Carver, you have a common problem. Build a foot plate with some insulation sandwiched in between the floor board and your plate. I have melted the heel on my right race shoe from that heat. I now wear a heel protector over my shoe for that problem.

Earl, check out www.headerdesign.com. It's free, and allows you to calculate various header designs, collector sizes, and main pipe sizes.

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Originally Posted by Tristan Smith

Most of the guys run a straight 3" inch pipe. The 12 valve motors need to breath. And Carver, you have a common problem. Build a foot plate with some insulation sandwiched in between the floor board and your plate. I have melted the heel on my right race shoe from that heat. I now wear a heel protector over my shoe for that problem.

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I too have been wearing the heal protector with no prevail.
I think we even met once in Atlanta. I came over to get some ideas off of Newberry's car when he was running in ITS.
I will build a foot plate and try that out.
Thanks again,
Carver

Back to your header thread!

Thanks guys - I am going to try running the 3" pipe right off the collector for this weekend and see how it does; but since both the S&S and the headerdesign.com websites say a length of 2-1/4" dumping into the larger pipe is the way to go I will probably fab up an alternate setup and try them both on the dyno later.

Carver - as Tristan noted, pretty much everyone I've ever talked to has the same problem with heat in this car. I've also melted the heel of my driver's shoe, even with the exhaust wrapped from the collector back to under the seat. I now use a heel protector, but I also know a couple of guys who went with the false floor solution.

Shoot Brandon Bogart an email (Brandon at BBRacingUSA dot com). He spent alot of time and money testing and developing a header and a 3 inch mandrel bent exhaust. It dyno'd +9 rwhp (+12 rwhp at peak gains) and +10 ft/lbs of torque (+12 ft/lbs at peak). He is willing to replicate it and save you the time and aggrevation of testing!

I just sent you a PM outlining our ITS exhaust system we developed. Good Luck, your looking in the right place for power.

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Originally Posted by slickS14

I just sent you a PM outlining our ITS exhaust system we developed. Good Luck, your looking in the right place for power.

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Share the knowledge! I did not get any PMs

Hey Chris, You drove all the way to Road Atlanta to "snoop"..hahahaa..I figured you had pics, no need for a verbal/written description. Glad to see your car is running good. I stop in and check the forum from time to time and I saw this thread. I like that headerdesign.com site also. Everyone take care, good luck racing, I really miss it. Maybe one day I'll give another shot.

I'd have to look to see what Bob did on the exhaust in my car. I can't picture it here at work. I can tell you that it goes extremely close to the steering column and was obviously fabricated just to miss it. I hope to make Road Atlanta in July and the hood is usually up.

As for heat in the floor, use a piece of sheet metal and sandwich some insulation between it and the floor like Tristan said. Just pop rivet the sheet metal to the floor to keep everything in place. That's what I've got and I haven't melted a shoe yet.

David

Holy shit, why didn't you guys tell me the exhaust in these cars is so friggin important!?!?!?!?!? :D

Today was the first time I've had the car on the track since re-vamping the exhaust. For the time being I just went with the cheap & easy way out - cut the collector where it was about 2-3/8" diameter, welded on one of those Mr. Gasket header reducers, backwards (2-1/2" opening up to 3"), and ran that right into a section of 3" pipe, into a bullet muffler, and then ran 3" pipe back and out the right side in front of the rear wheel. Loud as shit inside the car, and probably to anyone on the right side of the car - but on the left side, where sound control just happens to be at Summit, it was only hitting 99 db.

I had no idea what to expect going up there this morning - was just hoping that I would see some noticeable difference. Well, I am pleased to report there was a noticeable difference - 1.3 seconds of noticeable difference!!! Yes, that's 1.3 SECONDS, off my previous best time, which I set at MARRS 1 this April, which was also the last time I had the car on track. Needless to say I was just a little stoked.

So, now I need to plan some time to try out a couple other designs that Chris and Jim have been kind enough to pass along - hopefully there is still a little more power hiding under the hood.

Thanks again for all your help guys.