BS-Legal Exhaust Weights/HP Bonuses?
 

I remember that I informally polled BS participants at the Packwood NT, but at the time I was broke and couldn't afford an exhaust. Now I can! And of course I don't remember what conclusion I came to back then.

I'm going to get an aftermarket exhaust of one sort or another. I'm just curious what's going to give me a good weight loss and a decent HP boost. Basically, for BS, what's the best option, decently cost-independent? I've heard good things about the Borla, which is listed as 11HP gain, but that's all I remember.

Before baghead says it, I will...SEARCH :cwm27:

There's a bunch of good info on exhausts on this board. I'll say one thing, though...according to dyno runs done by a number of people, you aren't going to be picking up 11hp... :)

I'm not expecting much in the way of horsepower, but every little bit helps. I'm curious about weight loss, though. Goeke was trying to tell me that one of the exhausts was like ~40 pounds lighter, which seemed too good to be true.

The complete stock system, cat back, is 39-40lbs. So no way you are going to save that much.

My system is about 17lbs from the cat back: https://www.rx8club.com/rx-8-racing-25/single-side-exhaust-59424/

If you want dual the only light one is the JIC.

Here's what I ended up copying, the "Isley System tm" :)

https://www.rx8club.com/showthread.php?t=59424

EDIT: Looks like UHOSER beat me to it...

if you can live with the price you I'd suggest the Tanabe UltraMedallion, it's part Ti and part stainless, somebody claimed it's as light as the JIC full Ti, but I'd expect it to weigh a few pounds more, maybe 20 lb max I'd guess but I've never seen an official weight published. It's a fairly straight through system, but comes with silencer inserts that can be used for general street or sound-limited autox events.

generally speaking, you want the most free-flowing system you can find. A catback open pipe is best for power and weight if you can live with the noise.

https://www.rx8club.com/showpost.php...77&postcount=4

https://www.rx8club.com/series-i-aftermarket-performance-modifications-23/what-lightest-non-titanium-dual-exhaust-106580/


The OE RX-8 exhaust weighs 39 - 40 lbs

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Did you see your noise readings from this weekend? At 50':

run 1 95db
run 2 94db
run 3 93db

That's a fair amount of noise to "live with", too close for SD!

No, but thanks, I was trying to get them. Are you sure it's 50 ft? I thought they were measuring at 100 ft, which is a big difference on the dB meter.

I can easily quiet it down below 93 dB with a small weight penalty

Yes, it's confirmed about 50ft reading. See http://www.baautox.com/forum/index.p...tart=0&rid=230. Gave the #s to dknv last nite actually, so she's aware of you going WOT more than she did.

I'm probably the lightest RX-8 autoxer out there, coming in under 140lb. So should I spring the $160 for ULLLOSE-spec single exhaust to save 20 or so pounds? The weight reduction in the back does not have the same effect as unsprung weight reduction thru wheels, correct? Namely, the multiplier factor.

20 pounds is not insignificant...plus, you get rid of the hybrid electric motor/Evinrude sound of the stock RX8 :cwm27:

You are correct, though, that taking that 20 pounds off the wheels would be more advantageous. I don't know about the pros and cons of taking the weight off the very rear of the car, which is what the exhaust swap does...in some cases, autocrossers have found having more weight far back has helped with weight transfer, particularly off turn, like in the Corvettes, where folks have added trailer hitches just for the weight on the rearmost part of the car. Of course, that's a completely different situation than a low torque RX8...like I said, I just don't know.

Well, sign me up for ULLLOSE-exhaust convert too. I'd be a happy camper with just more torque. The challenging part is to put it up, since I have never weld/solider anything in my life. I'll check our your exhaust to get a visual clue of what to do at the next event. Maybe install-help too? Forgot to ask you to drive the car to check my rear shock setting. :angel:

I bought the RB "Race" exhaust. It weighed 26lbs with all the bolts and installation pieces. That was a few pounds lighter than RB had advertised....which was fine by me.

for my autox exhaust, i have my own version of the isley exhaust, but with a magnaflow. also for the noise reader. in the first run group the guy was in the worst spot ever. right next to the stadium so all the noise echoed off and i bet screwed up the readings. he also claimed that the drivers were seeing the noise meter and letting off the gas while they went by it to throw off the ratings. when i ran i never even saw the noise caluculator and i wouldnt go slower just to get a quiet reading. its not like they are doing anything but write you name down on baautox.com if you get a high reading. =P

exhaust
 

How do you like it so far? Is your car driven on the street as well? Any resonance at certain rpm's...I could do search but just looking for an imformed racers answer. Notice anything different otherwise....

Thanks

And what's wrong with a hybrid electric motor/Evinrude RX-8? I may just make a move in that direction to get better fuel mileage, damn the sound meters! :hahano:

Honestly, I can't tell a difference in power. I chose to go that route because I figured I could sell it and get most of the money back. It is a well built piece. On another note, I went with the custom exhaust job on my M3 and that exhaust sold for fifty bucks under what I paid. Most M3 exhaust's from aftermarket companies go for 500+ so a custom 185 dollar job just seemed like the logical choice.

The Isley setup is the best way to go for a hardcore stock autocross driver. I ran before him at nats so I didn't get to hear how his setup sounds but it's lighter than the RB setup for sure by about 10lbs.

Aaron and Brian might want to chime in because they have the same exhaust. My opinion is that it is very deep sounding at low RPM and but seems to go to a higher pitch sound at higher RPM. It almost seems that it gets quieter at higher RPM's. To most people, it would probably be irritating as a daily driver but I made the change to get rid of some weight, maybe gain a couple HP and be able to sell it for a reasonable amount.

Yes this is my daily driver and the lower the RPM the more it drones. The interior rattling irritates me more than the exhaust by FAR.

my latest one is now under 5 lbs and should pass the SD sound limit since we were right at it with an open pipe, unfortunately I gained 10 lbs in the last year :doh:

So I finally got around to making a "Isley inspired" exhaust. I decided to try a Magnaflow muffler instead of Borla because I've always been happy with the sound on other cars I've owned and because the price was so much lower.

I purchased the 5x8 oval, 14" body Magnaflow muffler off of Ebay for $50 shipped, 1 u-bend from Summit and a tip from the muffler shop I go to.

Here are the results:

VIDEO!

Pictures:

http://i172.photobucket.com/albums/w..._exhaust_1.jpg

http://i172.photobucket.com/albums/w..._exhaust_2.jpg

http://i172.photobucket.com/albums/w..._exhaust_3.jpg

A couple more comments. Big thanks to brattesani for sharing some photos and specs of his custom Magnaflow exhaust and the sound is pretty quiet inside the car. There is no drone when cruising around town or on the highway.

To bad you put the weight on the wrong side of the car. :dunno:

I have an Isley exhaust as well, except with a turndown behind the bumper instead of a tip poking through the right rear. It only took a couple of hours for me to cut the pieces and TIG it together by myself, and I love the way it sounds.

Right rear passengers complain about it the most, and it is a little obnoxious on long drives, but it's very livable. I'm going to be making the drive home to California from Michigan after I graduate, so that will be the ultimate test. Aside from that, it's gotten surprisingly many sound related compliments, so I'm pretty happy about that

I know, but I didn't want to deal with all the other convoluted piping to have the passenger side exit. I don't think it would have even worked with the 12" long muffler without looping back to the driver side first. Smaller radius bends may have helped too.

I have a 16" muffler on the pass side. :squint:

I was talking about the added tubing of your J-tube that loops over to the drivers-side. I'm sure I'll be at a huge disadvantage. :uhh: I think my disadvantage will be more due to my driving.

No you will say "if only the muffler was on the other side I would not have lost by a tenth". :lol: