Brettus NA power project
 

So................ the RX8 I bought recently came with a spare (low compression ) engine .I was initially going to turbo the car but having that engine got me thinking about what can be done NA . I've been down this track about 15 years ago and lack of results prompted me to turbo my other 8. However .... I've learned a lot since then so...I have high hopes of finding some extra NA power ........ here is the plan:

1/ Dyno existing engine in the car. I know this is a fairly healthy engine with good compression and from a few roll races I know it's comparable in straight line acceleration with other good rx8s.
Existing Mods : Mazdaspeed flywheel,Brettspeed cold air intake, gutted cat,RMajic catback exhaust.

2/Fit log style header (copy of Teamrx8's header design) . Hope to get this done same day as dyno above. This will see if the header alone is worth any power.


3/ Rebuild old engine and fit . I'm going to keep the engine details secret for now but suffice it to say what I'm planning has never been tried before (to my knowledge) . I've already done the porting and the engine should get assembled(hopefully) before xmas.

Pics of car and intake .................

https://cimg4.ibsrv.net/gimg/www.rx8...9793d891cb.jpg

https://cimg5.ibsrv.net/gimg/www.rx8...19994588eb.jpg

sick mate sick

Sorry, an NA build is never going to be a Major HP Upgrade thread, the exception might be a 26B NA swap.

:icon_bs:

LOL ..... What hp gain would qualify as 'major' Team ?

Excellent Brettus - looking forward to seeing your quest for more hp.

^^ Ditto. Good looking car. Interested to see what you come up w/ and if any principles c/b applied to FI. :icon_tup: :)

Cheers Curt.
That's how I came up with the concept (trying to think of ways to overcome FI limitations). However, the way I've ported this engine wont suit FI and I don't think I have the motivation to do an FI version.

I assume the issue is how to make the "air pump" pump more air when it is NA, eh? I assume you cannot add larger FI for larger gas volume and have the engine pull in more air as NA. Damn physics.

20b should be able to get you to between 450whp and 500whp as proven by defined autowork's NA FD (before he went to a 26b). I would consider that "big power" NA wise.

I dont see an NA Renesis breaking 300whp without a very exotic / 20b cost level setup.

Team is just being pedantic. This forum actually includes "porting" in the description so that's why I posted here. I feel anything over a 10% gain would justify the "major" title given the history of this engine.

hahaha you may be right.

No, I’m being truthful. NA porting is in here because back in the day everybody thought there was some kind of hidden well of Renesis secret sauce in there somewhere. In reality, Mazda squeezed most of it dry. Which they didn’t give us much to work with as far as porting potential goes. You’ll be lucky to come up with about 10 bhp ported over what the best hand built factory stock engine can do; about 280 bhp imo.

the best mod imo doesn’t change the potential of that, but adds long term durability; revising the apex seals to the full depth 13B type and using Iannetti ceramic seals. Pretty expensive mod though, especially since both new rotors and housings should be paired with them and then the rotor rips need to be modified using an expensive technique for the deeper seals. The OE seals will start off the same, but performance will fade away faster over time.

The other issue is that the potential is so dependent on intake resonance that you can go backwards real quick if mods interfere with or impact it negatively. I don’t what the plan is here, but imo the best you’re ever likely to see is around maybe 240 rwhp, and that’s going to require an ultra lightweight racing clutch/flywheel rather than the usual street type parts with a fresh blueprinted trans and lightweight wheels/tires. 230ish is more likely though.

Team Pedantic wishes you well.

We will see I guess, but if I could get say, double, the 10whp you say is tops for porting ..... it's a major win. The engine isn't going to cost me too much to try this concept as I didn't have to buy any major components. Just seals , a little machining and labor to assemble.

The manifold is being built this week and dynoing it might happen as soon as next week ...fingers xd . No expecting too much but maybe there's 5-10 in it ?

Also : just copied this comment you made to me in another thread :

:D:

That’s an entirely different situation. You think you know something pro builders who’ve been doing rotary engines since the beginning and outfitted with their own engine dynos and machine shops haven’t been able to find yet.

the path of the other thread is not so well travelled.

.

It's pretty well traveled ...just not by you.

And no , I don't think I know half of what those guys do. But I'm still willing to give it a shot ......1/because I haven't seen it done before............ and 2/ I think it will work.

I love stuff like this. Thank you. I have no plans to go FI, so its nice to see what if anything can be done NA. I know there have been some build threads on this before, and consensus is that there is little to be had, but new ideas are new ideas, and it is nice to see them implemented, documented, etc.

Like header theory...

Which was an excellent contribution to this forum.

Thanks Kevin :)

The mod I've done wont be that hard to implement for others............. if it works. It took me several hours with a die grinder plus there is the machining which I couldn't do without a mill.

I don't plan to do anything else to get power BTW ...none of that fancy stuff that Team mentioned.

I also have no desire to go turbo. I'll be waiting for your results Brett. And thank you for being adventurous.

Looking forward to this regardless of how the results pan out. Hopefully you're able to include extensive photos.

Except for discussing the conventional porting limitations, nothing I mentioned in the previous post is about making power. Some of the “fancy stuff”; as Brett calls it, is for long term durability, especially for performance/track use. The other parts simply allow power that already exists to be applied at the tire contact patch rather than consumed prior.

A factory clutch/flywheel assy. Is about 32-33 lbs. while a 5.5” 2-disc racing clutch/aluminum flywheel can be 7-8 lbs. the big difference though is MOI; which has a much bigger impact on engine output that the weight difference. The 32lbs of OE weight is centered around a 10” radius while the 8 lbs racing setup is on a 5” radius (general guesstimates in my head, not calculated; moi = mass x radius^2, 3200 vs 200 = 16x dMOI vs 4x dMass). That’s why the usual ltw street flywheel with OE size clutch doesn’t amount to much. You save a couple of lbs, but radius center and MOI are not impacted so much. You need to drop down to a 7.25” clutch setup to start seeing any noticeable gains.

The wheel/tire package also has a similar impact; not just the power required to accelerate the rear wheels, but it also has to overcome MOI of the front wheels, drivetrain, brake rotors, etc. along all the non-rotating mass weight as well. Some of those only show up in real world acceleration and not on a dyno, but you can potentially have the highest output NA Renesis engine in the world, but not be anywhere near the ‘fastest’ RX8.

so anyway, when I first did the header manifold, ultra-flow cat converter, and race muffler back in 2006 on an otherwise factory stock RX8 I ran it on a dynojet and made around 206 rwhp. No tuning, no intake, OEM everything else.

.

What changes were made between the 206 Dynojet dyno and the 220 Mustang dyno ?

Intake, tuning mostly, exhaust muffler was different, fresh #10 race plugs. I left the car at Cobb Tuning for them to develop the AccessTuner device in Sept. 2007 and they had it up around 215 or so when I picked up in Feb. 2008. I had it tuned again by them a while later when the WOT AFRs we’re reading high. Not sure if that was from intake mods or what happened, but that’s when it pulled that dyno. It made a few HP more actually, but at around 13.8 AFR or so. We ended up around 13.1 or so on the final pull. In fact my pcm has no factory base map. The base map on it is the Cobb tune from then. There was no RX8 AT device yet and they were doing it all on laptop software. So when I finally got the tuning device it has that for the original tune. I tried to get a AccessRacer copy of the tune from them, but there was something different from what the software they were developing it with and the public version that prevented doing so. So I couldn’t even use it to build future tunes from and had to start from scratch.

Hmmmmmm ...so from that, I guess the most I can expect from the header alone is between 5-10whp ?

Good luck Brettus.
looking forward to some data.


Godspeed

I had no base tune on the car, but if I had to guess the manifold with high flow cat/exhaust is probably around 8 - 10 hp. Maybe. I mainly did the manifold for weight. It was around 7 lbs and still emission legal. OE is about 15 lbs.

Damn .................it's sounding more and more like the manifold is going to do sweet FA on its own .

I wouldn’t be so sure. I always said the main improvement for exhaust mods was weight reduction, but opening the whole thing up for maximum free flow is likely worth some gains at higher rpms. So it’s not just the manifold, it’s the rest of it too. Which I had a real 100 cpi metallic racing cat rated for 500 hp with full 3” from the rear exhaust port to the rear of the car splitting into dual 2.5” straight-thru racing mufflers & tips out the back. The flow capacity could support a 400+ hp rotary turbo engine. Some people are claiming Speedsource was using 3.5”, but that seems a bit OTT to me. The best thing is probably a drag style header megaphone, but that’s going to be a serious sound and heat issue, lol.

https://cimg0.ibsrv.net/gimg/www.rx8...5a4731db2.jpeg

Progress!!!!!
https://cimg4.ibsrv.net/gimg/www.rx8...0206a7895d.png

Think I used a shorter radius elbow to match the OE centerline, likely doesn’t matter though. Looks good.

I thought it looked a little too far out ..but it's deceptive because the flange isn't nearly as deep as the stock one .

Yes, looks good. But wouldn't it be advantageous to angle the runners toward the rear to minimize reversion, and increase flow? Probably minimal additional positive effect, but since the point is optimization.

Maybe, hard to say if that would make any difference.................. too late now.

There’s no reversion because without overlap there’s no place for it to go. You have to get your head wrapped around the whole new way of looking at it outside the box of traditional convention. That’s the whole point of making it as free flowing as possible. It just needs to get out freely. The rest will take care of itself.

I get your point regarding no reversion d/t port overlap. However, I'm not referring to inter-port interaction...but the increased backpressure within the runner from perpendicular entry into the collective "log". Same principal involved in designing bends/elbows with as great a radius as possible. Certainly a 90 degree incidence into the log increases backpressure, I.e. reversion in that sense. Quantifying the effect would require comparative testing with a manifold design fitted with all curved runners similar to that fitted on the rotor 1 primary exhaust shown here.

jcbrx8 ..... I think the increasing diameter plus the offset of the port to the log does exactly that to a large extent. Remember there is limited space here so making radius bends flow into the log isn't possible . To do that you need to make a conventional header . And Team has already shown that this design does better than most conventional headers so................................

no, those two ports are discharging to a larger volume where the pulse pressure expands and is decreased. That’s the purpose of expanding come shape of the log itself; the volume increases as each port adds it’s contribution. The front elbow is also working to push the other two down the pipe in a spiral flow motion. Again, while Mazda may not of extracted every last bit due to other factors, they worked very hard at extracting as much power as possible given those limitations. My contention has always been that they already knew what I’ve been claiming about no overlap and how it voids common header theory. That said, I don’t see anything wrong with three short header pipes with radius bends into a proper long angle merge collector. It just adds complexity and cost without any real benefit imo. The exception is weight vs strength, which I now have a tubular header to use ultra thin tubes that have the thermal expansion flexure capability for long term durability. The advantage there is weight though, not power.

While I believe the idea has merit for "some" benefit in the upper rpm range..., I do see both your points: the expanding diameter log and induced swirling motion on exhaust entry would work to reduce the back pressure / reversion effect. And I will concede that the likely minimal gains on an NA application are insufficient to warrant the additional complexity & cost. :icon_tup:

Following w/ interest...

Car is on the dyno ATM and have done a base power run . Only problem..... never thought I'd say this about a Renesis ....it made too much power ! So will do some more runs and try figure out why that was .

You’re not running it on an all wheel drive dyno with it set to all wheel drive mode like the Motortrend guys did with the C8 corvette they tested??? ;)

No ...it's a Mainline hub dyno.
I have tuned a few other NA Rx8s on this dyno and typically we don't see any more than 195 for a good stock setup and 205 for a race prepped setup (stock engine, header, intake but 3" header back exhaust).

We started the day with the stock header. From the first pull we were up around 220whp which I thought was an anomaly so we did probably another 10 or so pulls........... but it was always up at around 220.
So this was : Stock header , stock midpipe with 1/2 cat still in place (rear half gone) , R majic catback , Brettspeed intake , stock coils , mazdaspeed flywheel. Engine has been rebuilt and is in good condition with good compression , porting ...unknown.

Then we set about fitting the new log header . Gav at HPR made an excellent job of it , couldn't have asked for more. I was able to do most of the removal and replacement in HPR's shop myself which was good of them to let me do that. When we removed the midpipe we were very surprised to find 1/2 the cat material still in place. We removed the rest of it and fitted the new log style header then headed back to the dyno.

We did maybe a dozen pulls. Most of these were around the same numbers as earlier with the stock header but one pull showed more power at 233whp . I'm going to say that pull was an anomaly but it's the one we ended up printing off so that's the one you will see here. I'm also going to do some street pulls today to see if anything has changed from two days ago.
Pics to come.....

Well to be honest when I had an engine professionally rebuilt and installed it I was pretty sure it was way stronger than when the car ran the 220 hp dyno on the original OE engine (only around 20,xxx miles or so on it), but I never put it back on the dyno to find out. Just my butt dyno, but the car was super fast and I was having issues with power oversteer competing on 180TW street tires. That was the engine that did around 270 bhp/190 btq on the builders engine dyno though.

Some pics of the install :

https://cimg2.ibsrv.net/gimg/www.rx8...2bb6a97d83.jpg
https://cimg6.ibsrv.net/gimg/www.rx8...7c50836ede.jpg


https://cimg4.ibsrv.net/gimg/www.rx8...1978cd2e72.jpg

The blue line is with stock header and red with new log style.
I really don't trust that 'after' pull as it seems really odd and the other logs weren't showing that. Possibly something to do with TCS as the TCS button seemed to crap out early in the day. I really couldn't see any definitive gains from the header looking at all the pulls together.

https://cimg6.ibsrv.net/gimg/www.rx8...6dfaa8e3ee.jpg

Hopefully there’s a different dyno around you can use. The rolling motion of the data leads me to think it’s dyno induced. My car doesn’t have DSC, but I suppose there could be something going on with that too.

world record for NA renesis? woudl equate to about 300 FWHP?

Peripheral port incoming?

How much of an impact do you think removing the rest of the catalyst had on the results?

Would be interesting to see what a manifold with separate runners of the same size you're using now routed into a merge collector would produce...something like Team's latest design. I suspect that some portion (perhaps small) of the flow from the back 2 runners tries to initially go forward when it first enters the log. If that does happen, I would expect a merge collected manifold would eliminate that problem.

I know we don't trust VD but these two logs were identical conditions as close as I could possibly have done. It is showing small gains from the manifold (green line) up top.

https://cimg4.ibsrv.net/gimg/www.rx8...dd83d857f1.png

I really wouldn't trust that red line dyno ...it just looks ...odd . And when that happens you know you have a rouge result. I really didn't want to post it , but it's all I had.

:suspect: