pjr

iTrader: (8)

Hyper4fance, this thread is one of best here in ages, especially since it goes against conventional thinking!

So, the starting point should be RB's road race header. Since the ISC isn't around, use a megaphone as a collector. I think you're saying 30" is optimal.... any idea on the I.D. on each end for the megaphone? And from there, pipe back to favorite muffler (magnaflow or whatever).

So I have that right?

BTW, Wolfe is like 10 minutes from my work. That will work well!

Hyper4mance2k

iTrader: (40)

I'm not saying 30" i soptimal. I still feel Racibng beats numbers for collecting with custom exhasut systems is correct., but collect into a megaphone and expansion chamber and then ramp back down and out the back. http://www.racingbeat.com/Tech/Tech.Exhaust.2.htm

pjr

iTrader: (8)

I'll take another whack at this:

• Start with RB's Road Race Header
• Add the RR Header "Outlet Flange" part 16197 to fabricate from the header.... reduce to 3" then...
• Expand to 4" DynaMax bullet race muffler to serve as expansion chamber.
• Fab back to 3"
• Simmer with a 3" pre-silencer and muffler to taste. Stir and enjoy.

Kerebrus

iTrader: (30)

Reduce to 3"? You mean enlarge to 3" off the header.

pjr

iTrader: (8)

http://www.racingbeat.com/FRmazda2.htm
Yep! My bad.

BTW, Racing Beat has a collector/megaphone... probably could repalce the DynaMax from the list above. It's here, part number 16119.

Kerebrus

iTrader: (30)

You can't link products on Racing Beat's website, it just takes you to the homepage. Just list the part number that's the easiest way for people to find what you're talking about.

pjr

iTrader: (8)

Yeah, I know, it only brings the page up... I listed the part numbers too.

Hyper4mance2k

iTrader: (40)

No... if you use this. http://www.racingbeat.com/resultset....rtNumber=16119
you're going old school with the exhaust and building an exhaust that has nothing to do with this thread. the whole point is the expansion chamber not a long megaphone....
collect the 2 1-7/8" pipes into a short megaphone fron 2.5" to 4" them put a muffler or a straight pipe 4" then colapse it back down to 2.5-3" and run what ever exhaust after that. It's not that hard to figure out.
Mine expands from collector to 4" in about 6" where as the megaphone expands from2.5-4" in 24"


p.s. you can link to parts on the RB website, just not very well...

mine:

racing beat

pjr

iTrader: (8)

No desire for old school exhuast LOL! Thx for the feedback.... How's this for a revised plan:

• Start with RB's Road Race Header
• Add the RR Header "Outlet Flange" part 16197
• Fabricate/megaphone output from the header, expanding from the pair of 1 7/8" outputs to 4" in about 6 inches
• Connect to 4" DynaMax bullet race muffler to serve as expansion chamber.
• Fab back down to 3"
• Complete with pre-silencer and muffler per volume needs.

pjr

iTrader: (8)

P.S. And use the last item on this page as a short megaphone from the header's ouyput to the 4" muffler. It's a bit too long at 9" but we would need to cut off some length at the 1" end anyhow.

n0ferz

iTrader: (4)

Hyper, will I get any benefits if I do this to my stockport12a? Also did you use 2 Dynomax Mufflers one after each other ?

thanks

pjr

iTrader: (8)

Correction: last item on page 1.

Hyper4mance2k

iTrader: (40)

should work, but 20G steel is pretty thin...

rotarygod

iTrader: (1)

I'm still not convinced when it comes to ISC's exhaust. It's pretty poorly built which is obvious just by looking at it and a fiberglass Dynomax bullet muffler isn't going to live long there. At least not in the form of a muffler. I'm sure it will just burn itself out and stay a hollow chamber but it will lose muffling ability. Keep in mind that the tuning in an exhaust is based on sound pressure waves and when you change the intensity of these, you change the tuning. Now saying that, being built poorly and functioning are 2 totally different things. It appears to produce good power. However Kahren got 195 rwhp with a plain old 2nd gen Racing Beat header and catbck so I still don't see why all the fuss about it. Have a look:

First run 182 rwhp: https://www.rx7club.com/time-slips-dyno-128/na-streetport-6-port-dynoed-182whp-details-inside-416012/
An update, 195 rwhp: https://www.rx7club.com/time-slips-dyno-128/na-6port-streetport-dynoed-195whp-update-418805/
Here's what he did with a stock exhaust manifold (2" outlet): https://www.rx7club.com/time-slips-dyno-128/na-6-port-dynoed-152whp-details-inside-461424/
He even built a custom intake manifold and retained the stock exhaust manifold and did 178 rwhp!

Admittedly the RB system isn't the be all end all system by any means but just applying an expansion chamber to just any size pipe isn't going to give the same results so saying that it can be changed to X from this and to X pipe size over here instead is just plain guessing. I'd personally rather just use an off the shelf header and get basically the same results. I know I can build a better header but at the end of the day it takes some theory, some testing, and lots of time and it's pretty much guaranteed not be be correct the first time.

The entire system works together. There is no one component that is more important than the other. The expansion chamber is made up of 3 parts, the divergent cone, the body, and the convergent cone. You can't say it's about the expansion chamber and not the long megaphone. Yes it is! The megaphone is a part of the expansion chamber. A long megaphone will have a very different effect on power than a short megaphone expansion. A greater angle with a shorter cone may work better than a longer cone with a shallower angle or vice versa. You never know. Each engine responds differently. The length of the expansion chamber body, in this case a bullet muffler, also plays a part in tuning. The convergent cone length has an effect. The outlet pipe size does too. The most important thing is the area of the collector itself as differences in size here change the powerband. All I see here is a bunch of guessing (and advice being given based off of it!) with no fundamental knowledge of how or why exhaust systems work. To make matters worse it's being justified by comparing it to an unequal setup that had far too many elements that affected the results. I suppose I should mention that a properly designed exhaust using an expansion chamber will theoretically produce a wider powerband at the expense of overall peak power. A poorly designed one will hurt power everywhere. This is the downside of guessing. There are more bad combinations than good ones! If you want a good idea of what their potential is, take a look at race car exhaust design. Look at their headers. Then tell me how many are designed like this. I think everyone is expecting a miracle by copying this design and while it may work just fine, try looking at what others have done with other systems before you make an absolute judgement call. There's lots more to making power than just throwing an expansion chamber into the mix.

Hyper4mance2k

iTrader: (40)

I'm not saying long megaphones don't work. in fact i know they work well. I was saying that my expansion chamber is built around a short megaphone.
Kahren also built a s5 engine not a s3... more port timing from the factory, lighter rotors, higher compression. plus his very short intake system was length tuned for peak power, more air flow potential through the TB than my 43mm chokes in the weber. There are many huge advantages Kahrens set up has over mine. I bet he would've dome over 200whp if he would have put a different exhaust on there.

rotarygod

iTrader: (1)

You are also using a Weber intake and carb which flows quite well so you aren't exactly stock either. You've also tuned it and picked up a bunch of power. while you say you have stock ports, you've also admitted that they've been cleaned up. Most people don't even realize the stock ports can flow enough for 200 hp at their original size. There's obviously more to it than that though. The point isn't to say that your system is bad. It's not and obviously makes some nice power. It's definitely worth studying further as I feel just by looking at it that it can be improved starting with the collector. However the fact that Kahren could get near 200 rwhp using a plain old RB header and exhaust show that it is clearly not a restriction and not as bad as you have been trying to make RB exhausts out to be. I seriously doubt he could swap out his system for yours and pick up 30 hp. It's not saying he couldn't pick up some though. He probably could.

The standard 1st gen header/muffler system really is the only RB system that isn't all that great. Of course it is better than stock but that's not saying much. You do have to use one of the stock pieces though. I used to have their streetport long primary on my 1st gen and I loved it. I regret getting rid of it and may at some point in the future just copy it. I know there are more powerful systems out there than just a plain RB header and catback. I've had a couple of them. They aren't bad though and definitely capable of quite a bit. Nothing that is using a 2" pipe is going to give a whole lot of power though. I don't care who makes it. If ISC made a 2" exhaust, it would still suck.

DriveFast7

iTrader: (1)

I would like an exhaust miracle to go please. With a side of expansion chamber and metallic catalytic converter so it won't smell as bad or make my eyes water.

Hyper4mance2k

iTrader: (40)

my car doesn't smell bad or make my eyes water. I run 2 crane boxes adn waste spark, so i'm sure that helps celan up unburnt fuel that the stock ignition couldn't. And this exhaust is no merical. It's a diffrent approack to the standard. And if you look at the people who are consistantly winning ITS in the SE it's people using someones expansion chambers. Be it ISC, prisq, or any of the few other tuners doing them now.

My 48IDA weber has 43mm chokes in it and cannot flow as much as a stock FC TB with, if I remember correctly, 2x44mm butterflys and a 36mm butterfly.

As your quote says my one test result of back to back dyno compairisons is better than all your "expert" oppinions.

Kerebrus

iTrader: (30)

Butterflies are awesome!

Hyper4mance2k

iTrader: (40)

Spelling owns me...

rotarygod

iTrader: (1)

I've personally tried 3 different exhaust styles (long primary, short primary, true dual) on 2 different cars over the years with a total of 3 different engines including a stock port 6 port, a streetport 6 port and a streetport 4 port TII based n/a engine and tried multiple lengths on each including different combinations of collectors and pipe diameters. On top of that I fabricated them. Admittedly they weren't all pretty but they worked. I've even got my own custom machined exhaust sleeves that hold the stock port shape and area yet increase flow almost 30% while using a smaller primary and I did it for the first time 10 years ago. You can take my "opinion" any way you want. How many systems besides a bolt on and this one have you tried and gotten results off of? How many others can you directly compare? Your 1 lowly test result doesn't really tell you a whole lot more than to say that a 2" exhaust is restrictive and that's really no secret anyways. I've already shown you that even a plain RB header has more than enough capability to match your setup.

I haven't been insulting your setup or you. What I have been doing is trying to counter your claims that RB exhausts suck. You've stated it over and over again in multiple threads trying to steer everyone away from them and all towards your setup. I am also trying to show others that while you love your system, you are selling it as the be all end all exhaust when you really have no other quantifiable data to back it up. We know it makes good power but you have not shown that it's better than anything else that isn't restrictive. Maybe it is but you quite frankly don't have the test results. I've shown you alternatives that can match it yet you concentrate on other aspects of the engine ignoring that the exhaust could keep up quite easily. That's the point. A RB header can make the power that you are! You obviously have a setup that works for some track cars. Guess what a street car is not?

It's also a system that was designed for a 2nd gen. You know, the very car that you keep saying has more intake area than yours and makes more power than yours which makes comparisons irrelevant. Please don't get mad at me for just pointing things out. Just keep it unbiased and relevant. Thats all I want to see. I don't want everyone getting their hopes up only to try to duplicate it and then be disappointed with the results. Everyone was asking about buying a header when someone else here posted 230 rwhp on a streetported motor. They all thought the secret was the header. Nevermind the fact that it was a 4 port, with a shortened intake manifold, made peak power near 9K where a stock car doesn't rev up to, and was tuned very well. Everyone wanted to buy his header. It was a component in a system just the same as yours is. You are giving too little credit to the rest of your setup which isn't all that bad as your results would show.

Your car looks like it's alot of fun to drive. I just want others to realize that while there is good power to be had in the exhaust, there's no reason to believe that you have the best system for everyone. There isn't one. There are only good systems for different uses. You've got a good one for you and your setup. People need to examine all the options before they blindly follow any one system. What happens if you find an exhaust later on that makes more power than this one? Will you say this one sucks too?

mxd

iTrader: (1)

In theory, what would this exhaust do?






and who's is it? application? scavenging? .. whats with the choke and spiral after the megaphone?

peejay

My new 2.5" exhaust with straight-through mufflers only picked up about 1mph in the quarter mile over my old stock-midpipe exhaust...

It's at least really loud and annoying to drive, though

It does want about 10-15% more fuel in the 5500-8000rpm range, but it hasn't translated into more actual speed.

pjr

iTrader: (8)

Peejay, that, a bit depressing.... with that type of gain, then why bother with the header and system replacement? Unless you just want to make noise.

dj55b

iTrader: (2)

It has nothing to do with that, its like rotarygod has been saying, everything works as a system, and if the one part you're improving isn't the weakest link, then the whole system is still just as weak as before.

So if your intake is more restrictive than your exhaust, than you'll only be able to produce as much power as your intake will allow you to run, and visa versa.