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Yeah, that’s more or less what I recommend for most people. The only issue with a lot of those is the smallish primary pipe size. Most are 1.625 or 1.75” OD thick-wall primary tubes which is a little restrictive and the collectors more or less suck too, but in reality it’s more or less splitting hp hairs over what I consider optimum. Which you can lenthen the tubes and put a nice collector on it if that’s what you believe in. It’s a lot cheaper that way for sure. Couple of the Japanese companies offer 2” primaries, it will cost a lot more though. Because Japan.
Yeah, that’s more or less what I recommend for most people. The only issue with a lot of those is the smallish primary pipe size. Most are 1.625 or 1.75” OD thick-wall primary tubes which is a little restrictive and the collectors more or less suck too, but in reality it’s more or less splitting hp hairs over what I consider optimum. Which you can lenthen the tubes and put a nice collector on it if that’s what you believe in. It’s a lot cheaper that way for sure. Couple of the Japanese companies offer 2” primaries, it will cost a lot more though. Because Japan.
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I agree, I wanted to make something from scratch with 2" runners and this 3" burns collector I have sitting, but the time wasn't there. This, I think is adequate for now. Certainly, I don't think I'm going to lose a jacket because of it, that's a nut behind the wheel problem.
Not really, but in order to survive long term it needs to be built like a reinforced concrete poop house with heavier gauge material, which is going to offset any potential weight savings. Even though mine was T321 I’m retiring it due to stress fatigue cracking. It did serve me well and actually is still useable, but just needs to have cracks welded up annually. It’s not really that bad, but when a crack or two develops it’s not helping the engine bay heat situation.
Not really, but in order to survive long term it needs to be built like a reinforced concrete poop house with heavier gauge material, which is going to offset any potential weight savings. Even though mine was T321 I’m retiring it due to stress fatigue cracking. It did serve me well and actually is still useable, but just needs to have cracks welded up annually. It’s not really that bad, but when a crack or two develops it’s not helping the engine bay heat situation.
As i think i mentioned in the dsp thread, i did my exhaust as a full 3.5 back based on the speedsource designs. you're style ramping up to 3.5" is "easy", and i can possibly do some back to back from the racing beat header version and this style. Not that the fab work will be easy, but its a straightforward project.
Are you sure that wasn’t for the 3-rotor Rolex Grand Am RX8s? That’s pretty big for a NA Renesis. I seem to recall that they were only using open 2.5” on the OE body cars in the day
I can't fully be sure, but a roadracer who bought a speedsource rx8, running a class as a renesis car had a 3.5" (he is the 3rd party though, so could've been owner #2's idea). And it would be a coincidence when in DM's with ***** from Speedsource he told me there was a torque gain with 3.5" (if he mistook me asking about a 3-rotor vs. renny).
I fear I'll be low hp anyway, and a rebuild will be a winter project. I might not have meaningful data for a little while, but I V-banded from Header back, so a swap on a dyno day could be do-able if I feel like throwing $$ away for knowledge of the compromise RB header vs. the megaphone. Dyno would be done at Elite in Schaumburg when/if it happens, so he'll have some bone stock rx8 dyno pulls to have some sort of baseline for that dyno's readings.
It would be $$$ just to have knowledge, but a DSP group outing to do dyno pulls in Lincoln would be satisfying.
My 2 cents is Racing Beat since my last 8 had one and my new 8 does not. BUT... Like has been said a few times the HP gain is not greatly noticable even with a full RB system. Keep it stock and watch your Cat for degradation which will kill your engine when plugged.
For that street stuff, might be a bit, but not much really. Street pulleys tend to be more show than go. With a street flywheel you typically still have a full size 8.25” steel clutch so you’re not gaining much. It makes some difference for real race parts, but they aren’t streetable. Like an aluminum race flywheel with 5.5” mini-clutch. It doesn’t make power, it just frees up the torque to produce acceleration quicker.
weight is a factor, but it comes down to how it’s distributed from the center point (MOI - moment of inertia). So an OE flywheel and clutch assembly is around 32 - 33 lbs total weight. Some of the street flywheels might drop 6 or 7 lbs off that; which seems like a lot, but it’s still a full diameter clutch and the flywheel has to provide the surface for it. So you still have a lot of weight spinning out far from the center point.
However an aluminum race flywheel like Mazdatrix or i-Rotary (Iannetti) with a Tilton 5.5” twin-disc carbon clutch is only about 9 lbs total assembled weight (!!!) including the grade 8 mounting bolts. Of course it’s hard to launch from a dead start without some revving and slipping, but even the starter ring gear is aluminum/integral to the flywheel and most of the weight is in toward the center. Substantially lower MOI than a street type setup. These are generally the Renesis NA engines that dyno over 230+ whp because it’s not being sucked up trying to accelerate a heavy clutch/flywheel.
But even they might not get that if heavy wheels/tires are on there too. Kind of the same principle, except the clutch/flywheel is directly on the e-shaft at full engine rpms and the wheel/tires are geared down to slower rpms. So not as dramatic of a shift. It all adds up though.
not to highjack the thread, but do you think pulleys and a flywheel is worthwhile if its not a daily? Ive noticed you’ve done these yourself
Team fully addresses the flywheel question.
IMHO, pulleys are a dangerous waste of money. Any gains are tiny, and we frequently see lightweight pulleys fall off and destroy engines at the track: probably 5 per year. There was a beautiful garage queen yellow S2000 that lost its engine due to a lightweight pulley falling off a few months back. To add insult to injury, the owner opened the hood shortly after, which caused the oil under the hood to catch fire, and the car was burned badly. OE pulleys are tested for millions of miles, and are very reliable. Aftermarket pulleys are tested for 10s of miles. Not worth the risk.
As for HP gains on the Renesis generally, I never bothered, beyond the midpipe. I had the fortune to watch other people spend the money on full bolt-ons, only to see 180WHP on a DynoJet. The Renesis starts its relatively rapid descent into lowish compression the first time it is started, and once compression is below a certain threshold, bolt-ons have no worthwhile effect (assuming they ever did on this fickle mistress).
Also, the small power gains added by bolt-ons are all in the high RPM band (above 7000RPM), and how much time do you spend up there? (This excludes the lighweight flywheel, of course.) The RX-8 needs help much lower, and bolt-ons do nothing down there.
So the collector of the stock exhaust manifold is 2.5" right? is it necked down to 2.5"? Like can you cut off the flange and back a few inches and diameter is larger or no? If so what is that diameter 2.75" or 3"? Just want to be sure before I start ordering piping and catalytic converter. Thanks.
It’s 2.5” ID as best I can tell. However, there’s two squared protrusions on opposing sides and also one where the O2 sensor comes in at the top on the thinner inner wall section that result in it being almost squared off internally to a smaller opening that the gases have to pass through. I’m not sure if it’s possible just to beat those back or push it back with an exhaust pipe expander tool. You can see the thinner wall inner and thicker wall outer and those protrusions in the photo below
Got some names for the said companies? I get to Japan all the time. Great information BTW, I've been lurking and found some great stuff on here. Good to know what's crap, and what's good before wasting money.
I think that was posted by someone at one time as well.
Given ten to fifteen years it’s not a talent to repeatedly stuff up a straw man and ignite him. But whatever gives people their jollies.
Arguing that headers are pointless because Renesis has no intake/exhaust timing overlap and therefore scavenging doesn’t occur hand-wavingly ignores a lot of other potential physics going on with air flow, turbulence, and resonances. Shoving air into bigger volumes doesn’t necessarily lead to best outcomes in moving that air as quickly as possible and with minimal restriction. It’s important to realize too that theories are only as good as their ability to completely describe physical nature, not just a subset.
Its not to say just throw a header on and you will get gains, but discounting that a header can ever provide meaningful gains by referencing a supposed all-encompassing end-all-be-all final-word bible on header theory Is the worst kind of faux authority out there.
Last edited by schm1347; Oct 14, 2022 at 09:10 AM.
I think that was posted by someone at one time as well.
Given ten to fifteen years it’s not a talent to repeatedly stuff up a straw man and ignite him. But whatever gives people their jollies.
Arguing that headers are pointless because Renesis has no intake/exhaust timing overlap and therefore scavenging doesn’t occur hand-wavingly ignores a lot of other potential physics going on with air flow, turbulence, and resonances. Shoving air into bigger volumes doesn’t necessarily lead to best outcomes in moving that air as quickly as possible and with minimal restriction. It’s important to realize too that theories are only as good as their ability to completely describe physical nature, not just a subset.
Its not to say just throw a header on and you will get gains, but discounting that a header can ever provide meaningful gains by referencing a supposed all-encompassing end-all-be-all final-word bible on header theory Is the worst kind of faux authority out there.
Nice first post. You will certainly gain some attention.
Great information BTW, I've been lurking and found some great stuff on here. Good to know what's crap, and what's good before wasting money.
