Racing Beat exhaust dyno compairisons
 

So, I win, I was right. RB exhausts suck
The last time I dyno'd my car with timeing adjustments and playing with fuel the most we were able to get out of my car was 138.4whp @ 6400 rpm. That was with a RB streetable collected header and pre-silencer with 2.25" after the silencer to a apex N1 muffler.

Nothing was changed on my car besides the exhaust. Now I'm running an old Rotary engineering road race header.
I posted a bash thread about it a while ago because it wasn't equal length, but I thought it was RB. so sorry about bashing the RB RR header when it turned out to be RE. Anyway it's a RE RR uncollected header with the flange cut off and re-welded to make the runners equal length. Then it's attached to an old no longer available ISC racing center section. It collects the 2 runners into a 3" collector then expands into a 4" expansion chamber and collects back into 3" goes through a dynomax bullet pre-silencer then 3" over axle and out a magnaflow 3" muffler.
Well we strapped it back on the dyno and on the first pull I made 169.13whp@7000 rpm. I was kinda happy but my afr's were sitting around 13.2:1 so i put a bigger main jet in and they went to 12.5:1 and power went up to 171.31 whp at 7k. Then I peaked the shop owners interest and he wanted to see what the car can do so he gave me some more runs and let me pull out the jets and timeing light for free. So I backed timeing out to 26*btdc at full advance and gave it 2 more pulls. The final one was...
are you ready for this?


are you sure?
189.65whp @7200 rpm!!!! 144.74 ft lbs at around 6200 rpm.

Did you hear me yet? that's a 51.25 WHEEL HORSEPOWER GAIN!!! over the racing beat exhaust. need I say anything more?

Oh I guess... For those of you that don't know. I have an ugly 84 base model with a gslse 13b 6port with kind of a port job, but I wouldn't call it a street port as it's more of just a clean up to get the casting out of the runners. It has a weber 48 IDA and series 4 rotors. and my own Jimmie rigged Mallory directfire system.

*disclaimer!
I have my dyno sheets, but I can't get my roommates ghetto fab scanner to work, so I'll post them up on Monday from work. LOL! Awesome!! anyways. I'm really happy with 189whp. Now I want to see if I can eak 200whp out of this thing!!:lol:

Wow man, thats a ton of power man. I wouldn't say RB exhausts suck, however. I have RB components on mine and it completely changed my motor. They are very good quality and happen to be the only good rotary exhaust parts for our car availble right now, to the best of my knowledge. RE has been out of business for quite a while, correct?

Wait, you went from a Collected RB header to a non-collected header that dumps into 3" (or more) pipe all the way back and a magnaflow? It's not surprising that it flows more.

Changing the exhaust net you a 31hpgain before you started playing with jets. Yes I realize that you had no choice but to play with the jets to get your AFRs back where they made sense, and that's still a large gain, I just wanted to put a bit of emphasis on that as "just the exhaust" for the people who will miss that part and start yelling about the carb changes you made.

What I want to know is how does that compare to the RB "Street Port" exhaust. You obviously don't have a stock 12a in there so the regular RB exhaust is too restrictive, even the RB website would agree with that. I know that even the "Street Port" exhaust would flow less than what you've got, but probably not by as large a margin, and it will keep quiet while doing it.

The thing is that the RB exhaust (even the street port model) is designed to balance muffling (keeping things quiet) with street performance. I still wouldn't say that they "suck" considering they do give a huge boost in HP over a stock system while not making that system much noisier. I'd say they definitely achieved their goals, as you can get approx 20% HP boost on a stock 12a just by going from stock exhaust to even the collected RB. Plus, their parts have a reputation for outliving the cars they're installed on.

I've got a "Street Port" RB exhaust which is uncollected right until the rear axel as two 2.5" (or it might be 2.25"?) pipes, where they combine and enter the RB muffler. I know it's not the least restrictive thing out there, but it does flow very well while keeping the cops from noticing my car as it drives by. Having been around rotaries with Magnaflow mufflers, I know they aren't nearly as easy on the ears.

I doubt the difference between *just* the header/collector would be large between your exhaust and mine. It's the centre section and muffler that are doing it for you I'm sure.

I'm glad you enjoy it, but calling the RB system "crap" completely ignores the fact that your definition of a good exhaust system probably isn't what RB was aiming for, and isn't necessarily what all the people in the rx7 community are aiming for. I'd say instead that the RB exhaust achieves its goals, and your exhaust achieves yours. I'm happy with mine, you're happy with yours, and since I don't believe the difference between mine and yours would be anywhere near that 30hp, I don't feel that I would be willing to switch if your exhaust were offered to me. The noise is just too much of a factor on the streets around here. Perhaps on my autocross car it would be good.

My point is that you can't call this an apples-to-apples comparison since you changed so much. Nobody will argue that what you have now flows more than what you had before, so I'm not sure what we can take away from this thread other than "Hey guys, here's what I did to my exhaust and it gave me awesome hp".

Jon

Holy crap, that's impressive. I'm gonna have to get a ride in your car one of these days.

this is a 13B :icon_tup:

Actually i'm willing to bet it more the expansion chamber that gave you the most power (the ISC piece), expansion chambers are suppose to work really well in rotaries and gain quite a bit. Different afr's are needed for that too. A real test would of been to take the RB header and do the same thing you did as the RE one and bolt it up to that system as a whole. Only then you're doing a real comparison.

Do you have a picture of that ISC piece?

I will say an inpressive jump in hp but not just an exhaust change that did it. And I will add that you DID NOT have an RB exhaust as you did not have the main RB muffler. You only had RB exhaust components but not the full exhaust. On that same note, I believe with some more tuning and tinkering that you can break 200whp.

I actually had the complete RB exhaust and I cut off the muffler after seeing pics of the inside of it and put on the apex N1 and gained 5-7mph and almost half a second in the 1/4 mile. So that was an obvious gain in power, but fawk it was loud so I added another silencer and it was fine then.
To be more descriptive here's the break down of what I have now.
Before I had this
http://www.racingbeat.com/photos/16410.jpg
Now I'm running an old RE road race header. It's identical to the RB RR header pictured below. The only major difference is that the RE one comes straight off the exhuast flange for about 1 inch before it turns where as the RB Rotor1 turns right at the flange. This is supposed to be better for flow with the RE header, but it made one runner 27" and one 25". I'm a believer in equal length, so I cut off the small end and had it re-welded so each runner was closer to 26".
http://www.racingbeat.com/photos/16001.jpg
Then I have this ISC mid-section bolted to it, so it's essentially the same as the RB collected header, but with a properly built collector and expansion chamber collecting exhaust at about 30". The great thing about the ISC enter section is that the "expansion chamber" is a dynomax bullet resonator, so it makes it a little bit quieter.
https://img210.imageshack.us/img210/...ict0060is0.jpg
https://img338.imageshack.us/img338/...ict0061gd1.jpg
https://img338.imageshack.us/img338/...ict0062ym9.jpg
Then after that is just basicallya 3" "cat" back, but it has an additional 3" dynomax bullet presilencer, and at the end is a 3" magnaflow with a "cool" auzzie style turn down, so it is livable.

Viper did make an awesome point that RB designed a bullet proof exhaust that will probably out last everyone reading this, and they did a great job balancing power, style, quality, and quietness all into a bolt in package. My crap comment was aimed at the people on here and other forums that parrot out how RB is the best system for power over and over again. Here is clear evidence that their system can be out done. If I ever build another NA exhaust it will be based of the RB RR header only because ISC doesn't make theirs anymore, and the ISC expansion chamber shouldn't be too hard for me to replicate.

used RE RR header $40
ISC center section $250
dynomax bullet $40
used magnaflow on craigslist $50
box of mandrel bend pipes from Columbia river mandrel $70
installation $500
= $950 Hyper4mance Industries exhaust (LOL) 189whp
RB collected $758 135 whp Streetport $959 never seen more than 180 stock ported with this exhaust
Id honestly say my car is louder then the RB SP at cruise but it's much much deeper, but at WOT it's not much louder at all.
FYI this is the inside of a RB muffler one pipe in and two pipes out. It's a classic chambered muffler:
https://www.rx7club.com/attachment.p...0&d=1123206818

my beat to death header when I got it. lol
I sanded the hell out of it, painted it with 5-6 coats of high temp paint then wrapped it with header rap.
Attachment 709686
On another note I'm not trying to start a fight just putting out there what I have learned through the years on this rotard thing and what has been working for me. I'll be the ghinny pig and buy 50 different exhaust setups to see what works. LOL! Sometimes I guess I come off as a dick but I'm not trying to be this time, this time.

Nice work. Impressive gains over what's certainly the most popular "performance" exhaust on the market for the rotary.
Again, as Vipernicus pointed out, there's a compromise between performance and streetability. Arguably, I guess Racing beat considers exhaust noise level to be part of "streetability". LOL
Part of my dream custom set-up has always been an exhaust dump for that buried power you just found.

Flow. Heh-heh, you just never know till ya try it.

I have the street port full system for my six port 13b and everyone comments that I have the quietest RX-7. Well everyone local that owns a 7.

I've seen that cutout picture of the RB Power Pulse before, is that yours or a pic found on the forum? I thought the one found on the forum was contested as not rb but instead monza

Damn dude thats impressive. I want a hyperformance industries exhuast. I wonder how much power i can get outa me SP S5 motor with 48dco?

K so you said the inlet and outlet on that ISC piece (well the muffler that they use) is 4" right? now long is the whole thing? Just the muffler that is

What is the actual length of the primaries?

30" primaries
the isc chamber collects the two primaires into a 3" collector then expands to 4" dynomax bullet muffler. it 16.5" long "Dynomax Performance 24217"
https://static.summitracing.com/glob...lk-24217_w.jpg
then reduces back into 3" then it's 3" all the way out the back.
Gavin I want to put this exhaust on your car and see how it works with the super charger. I bet it makes over 225 whp.

I bet it would, too. I'll be taking my car down for a clutch job later this month and installing a better exhaust at the same time. RB RR header collected into 2", with an RB presilencer and a Borla. Not sure how close the primary lengths are, I haven't measured them yet. But in any case it's far from ideal. Between the larger ports and the supercharger, I bet the difference in power using your exhaust system would be even more dramatic on my car.

why are you going to only a 2" exhaust? I would do 2.5 at the very least with your supercharger setup.

He actually going with a turbo and 3". The SC and 2" is only temporary.

this has been an interesting thread, amazing stuff. Hey Hyper if possible can you get a whole picture of the bottom of your car. Would be really neat to get a view of it instead of the cut up pics if you know what I mean. My goal was a 2.5" on my charger but now looking into the way you did it since I too have an RE header sitting in my garage.

This is great stuff. Although you can only warrent 31 rwhp gaines to the exhuast change. Once you started messing with the carb it was over. That being said, 31 rwhp is a lot to gain from an exhaust.

That's why I prefer to design my own exhaust systems rather than buying a prebuilt one. It is more time comsuming, usually about the same price, and usually more work to get installed properly.

If you just want a good all around system you cant go wrong with a RB system, but others, like myself, prefer to be a little more adventurous.

I have a full old school RE system. When I first heard it I didnt like the sound. It has since grown on me. It is a great set up that has been running strong since the 80's and has many more years left in it. I HATE how low it hangs though. It's rediculous. I dont know why RE designed it so low, but oh well.

My favorite exhaust I have had to date though was the exhaust I designed myself. It consisted of: a RB collected header, RB presilencer, magnaflow 18" straight through presilencer, and ended with a Borla XR-1. All was 2.5". The only bad thing I could say about the system was that due to it being 2.5" it killed my low end torque for daily driving. Other than that, it was awsome. I would still have it today instead of the RE if I didnt need the money and had to sale it.

I have been wanting to see a dyno comparison of headers for years. Now, you need to keep your car as is and swap in a ISC header.

i dunno, if he would have made those carb changes on the old exhaust it would have lost power. new exhaust needed different jets.

or look at it this way, it was tuned with the old system, and then the last runs are tuned with the new system

Mike only had one header left when I spoke o him last and he wasn't planning on making anymore.
That's a terrible argument that only 31 was the exhaust. The 138.4 was made after jetting and timming changes and that was all I could squeeze out of the car then. Changing jets and timeing isn't modding, it's tuning. Every change you make to the car it needs to be retuned. If I was Fuel injected the ECU would've added the additional fuel automaticaly due to the extra air flow through the engine, because i had to do it myself makes no difference. All the power came from the exhaust and the engines ability to pull more air and fuel into the cumbustion chamber because it coule get more exhaust out faster.

On another note. My work scanner is absolutely errible and I'm at work so I'll just post the shitty PDF of the 138 one. Anyone who wants to convert it to a pic and post it in the thread for me please do so.
https://www.rx7club.com/attachment.p...1&d=1236027914
Here I made more HP at 3000 RPM than I made peak TQ anywhere with the RB exhaust so much for needing small diamater pipes for lowend TQ.
https://www.rx7club.com/attachment.p...1&d=1236027914

Great numbers

As soon as I get my car on the dyno (probably Friday), I will post my numbers. I have a 12A large street port. I've been running a stock port RB setup with no presilencer. I now have the RB single outlet header, 2.5" pipe with an 18"x4"round magnaflow and a magnaflow stainless w/ 2-3"tips. I know that the old exhaust was restricting the engine because I have a SP. I also changed to an electric fan and went from accel coils to MSD. So the numbers will not be 100%.

here's the PDF in picture :

https://www.rx7club.com/attachment.p...5&d=1236031252