hmm, the header design looks sick. Wish I can get one :P

I dont have much time to "look" at my 8 lately cuz Im too busy with the 7.

Great info ! I just learn a lot ! Thx man

 

That is a pretty weird design. 4 to 2 to 1 to 2 again.

mind telling me which jp company?

I know its from not Fujita, RE, nor Knight sports. at least I dont see it on their sites.

 

Let's pretend I have no friggin' idea what a 4th gear max load fuel map is---please educate me.

We run .92 because it makes power, is safe and saves fuel. We have run .94 and a 3 rotor team I know with an Synthetic oil company sponsor runs .96 with a 3 rotor. We run .92

Educate me please on teh 4th G max load fuel map.

 

I just took some rough measurements under my car with a tape measure. These are in no way accurate enough to design anything but ballpark the midpipe is about 42-44" long from header flange to "cat back" flange in a straight line (EG: I am not taking in to account the length of the bend).

The cat. is about 21-22" long and starts immediately after the 3 bolt flange with the header. There is a resonator in the pipe immediately after the cat. that's another 21-22" long. There is a bend in the middle between them that the cat. kind of narrows down and turns in to the bend.

An aftermarket cat. like the RP supercat. is much shorter I believe based on pictures I've seen on RX7store.net

So if you wanted to put a one or two piece header and cat. pipe together you have about 42" of mid. pipe. I'd have to jack up the car to crawl underneath and see length from exhaust manifold to header flange. Although it may be more useful to pick up on a datum from the engine itself since the length of the exhaust manifold from some random point doesn't really help much.

PS: I left you a voicemail.

 

i'm sure i'm the one confused.

you say you have your management set at .92. When i ask what exactly is set at .92, you tell me you're talking about afrs. So i understand you have some part of a fuel map set at 13.5 (lambda .92). I take it this means you want to get your afrs to be 13.5 when you're doing your dyno pull in 4th gear. And I think that means when your engine load is 100 percent in 4th gear at some rpm range, your target afr is 13.5. That's what I'm calling the 4th gear max load fuel map.

Does that make sense?

I'm curious about your actual afr when you did the pull. with the management, you're telling the ecu 13.5, but what did you actually get during the pull?
I'm trying to figure out what i should set mine at and What your reasons were for setting yours where you did.

see the highlighted part in the pic. maybe we're just talking past each other?

all great info. just trying to understand. i didn't think my question was stupid, but maybe it was.

edit: maybe dyno live tuning is significantly different?

 

I ask because i've heard the following comments on the best NA rx-8 ignition tuning...
- "leave it stock"
- "reduce split to 5 degrees"
- "add up to 2 degrees of advance over stock"
- "take 2 degrees of timing out.."

... and i tried much of it but lack the resources to hold all the variables constant enough for a decent evaluation


So i gather from that comment your reducing the ignition advance a few degrees (stock advances up to 30 with rpm before leveling out). What about leading/trailing split?

 

Subscribed. This is awesome info Eric, I love following you guys, and this is the cake under the icing

 

OK---I u-stand your Q.

Target is .92 and actual (from about 4,000 to 8,500) is .90/.91 to .93/.94. For the most part the Lambda is spot on at .92 with a few little little spikes in and around the valve actuation events. The more you tune the more you can tune out these little spikes and get right to your target. The valve events make it pretty difficult because so much air is rushing in (or out). Being off a little here and there isn't traumatic given the big change in air flow due to valves.

One thing to remember----we are using an extremely high quality engine management system so you have the ability to do just about anything and really get into the details.

 

It's actually Knightsports. That's their prototype for their 09 RX8 for RE wars this year. They're running a standard renny too, not one with rx7 housings. And, lastly..it goes from 4, to 2, to 1 all the way. They don't use 2 on their race cars. Their single has that cool titanium rotor tip.

Not sure why they did that, but before their header design was a 4 runner directly into a 1 for the mid pipe. Which is why I always asked "hey guys..what about 4 runner?" but I'm always batted down..lol. But now we have Eric here, so I wanted his thoughts on 4 runners. :D It must be SOMEHOW beneficial, especially if Knightsports did it for rennys for awhile, and now are expanding on it and making it a longer 4, into a 2, then 1. Sort of like a motorcycle, no?

 

I think there is confusion around with regards to a header.
When someone says "a header won't work" on the Renesis, what they mean to say is "a header is ineffective when it is not part of a comprehensive exhaust system design".
The "secret" to a header for the Renesis comes in part from what follows it.
No matter how effective a header design might be, it is dependent on the flow behind it to do its thing.

 

Whooo hooo. Now we have big players in this

Thanks for the info there Ray, good to know. Will be interested to see what kind of information/results you get if you test, especially when coupled with a sexy BHR midpipe... unpolished to show off BHR rugged side. lol

 

Bingo! We have a winner.

Now is probably a good time to talk about the path from the original stock exhaust to what we are currently running.

SHORT version:

Late Fall 2007 Bought a 2004 RX8 w/Man trans

Winter 2008 Got my hands on a SpeedSource header for the Koni Challenge RX8 cars. Mated it up to the stock cats and stock exhaust----made a few ponies

Late Winter/Early Spring 2008:
--Removed cats---made a few more ponies
--Tried different mufflers (1 under the car, 1 at the back of the car, 2 under the car, 1 under the car and one at the back of the car) --- found a few more here and there.
--Messed around with the Racing Beat reflash, tried different heat ranges of plugs new coil packs (always the stock ones---Koni rules do not allow aftermarket coils)
--Changed pipe diameters in the entire exhaust system. Smaller O.D., Larger O.D., ---found a few more ponies. Tried different types of mufflers.
--Moved some pipes around for better fitment, to make it easier to remove trans, reduced some weight, tucked the exhaust up under the car in certain areas so that we could run the car relatively low to the ground and not scrape/touch/bend any part of the system if the car were to leave the racing surface--power curved went up and down a bit.
--There was a long run where we made 210 hp all day long. Every motor would make 210. 210, 210, 210.
--Changed bends, bend lengths, choke sizes and locations (by choke I mean the smallest part of the exhaust system or the point of the exhaust which has the lowest surface area)---- found a few more ponies/changed the curve shape
--Then we were making a bunch of 215's. 215, 215, 215.
---Messed around with several different styles and lengths of INTAKES including different air filters, different air boxes, different shapes, sizes, filter locations, etc., etc., ---found a few more ponies and/or the shape of the dyno curved changed.
--210, 220 and everything in between as we tried things here and there. I think we pulled a 226 one time in 5th gear but could not duplicate it (In my mind you have to get your same number or curve over several pulls in order to back it up).
---Repeat process several times over 2008 and 2009 and we've ended up with a complete system that makes some great power.
---I've lost count however 11 different exhaust systems and/or exhaust system variants have been tested I recall. This does not include when we tried different intakes with these exhaust systems (and yes, there is no one super great intake that totally kicked everyone elses butt). We found some intakes work better with some exhausts and not as good with others (we are talking a few h.p. here and there).

So, the majority of power gains have been had and anything we get now (or try to get) is either a "change in the curve shape", too small to measure or is within 2 h.p which IMO is not good data. Remember: a 1% dyno variation equals 2 hp on our cars. THIS VARIATION COULD BE LARGER THAN THE DUMB NUMBER YOUR LOOKING FOR!!!

In conclusion, MazdaMan is correct. It is about the entire system and not just "the header".

 

Wow awesome info man!
Thinking of getting an exhaust
/\ True dat.

 

Anyone recall Gotham Racing 224whp on a Mustang dyno?

https://www.rx8club.com/showpost.php...73&postcount=1

Edit: Never mind. It was 208whp on a Mustang. They added 8% to make it 224whp.

 

Lol I was the first one Steve tuned and got 184 whp (I think) w/o midpipe or coils. I'm not sure about the 208 whp, but he did most of my dynoes in 3rd so maybe that wasn't the full amount?

 

Excellent info Eric - many thanks for sharing .

You have probably done this already but .......
It might be worth changing the timing of the aux port slightly now that you have maxed out the system .
I have experimented with it quite a bit in a turbo application and made some interesting observations . I know N/A is very different but who is to say Mazda got it exactly right . You might be able to lessen its impact on the curve with some experimenting .....

 

Excellent info Eric !!!!

 

I just find it interesting that everyone always says "you get more power the higher the RPM" and all that, yet Eric noticed that the most power you get is between 8.5 to 8.7 and anything higher there is nothing and it just could damage the engine... Very good to know. I can't tell you how many older RX7 ownwers, RX8 owners and all I've run into that always stress "get more RPMS!!"

 

I don't know about RX-7s, but doesn't the stock HP curve of the RX-8 peak at 8400 or something like that? Since this is a NA design, I would assume that the peaks would remain relatively the same as you aren't forcing more air into the chamber to allow for a peak at a higher RPM.

 

^-- I suppose so, but like I mentioned, it's only just what I've heard. Not necessarily backing it up or anything, but I always felt it was sort of a consistent thing that many people pushed to believe. Could just be me or the rotary people around me here..lol.

 

Yeah I've seen a few people argue for it. More RPMs on an NA car, if the HP curve doesn't just plummet after your peak, is helpful in holding a gear longer than other cars. It's great in auto-x if you can hold 2nd or 3rd gear for most of the run. But with the RX-8's 9000 RPM limiter, that's already damn high.

On the other hand, FI cars could make more power beyond the 9000 RPM limiter if you can get the boost controller to increase boost above that peak? The RPMs are limited by the amount of air the rotors suck in at that high speed, so if you can force more air in, you would get the power out.

 

It's all in perspective. The 'more RPMs' point of view has some validity to it, but just RPM without perspective or qualifiers is a crumbling foundation of theory.

Remember that 'power' is a function of torque, and lower gears have a better torque multiplier, so if you can spin higher, you can generate more power. The problem is, this doesn't always achieve what you want, and you still have to tune for a specific range. Eric's range is best backed off of 9k slightly, the 626b's range was probably more like 13-18k.

The 'more RPM' theory is based on the simple torque multiplier, but often lacks the additional information. If you could stay in 1st gear, with 1st gear's torque pull, all the way to 200mph, you would, because it is superior to even 2nd gear's available torque, simply because of the gear ratio. Obviously that is just a severe example, 1st gear at 200mph (stock gearing) would be about 42,800rpm but hopefully you get what I am going at.

Don't get me wrong, I am not saying that Eric is wrong, because for his application, he is right. There is no reason for him to go above 9k, so they have tuned appropriately, and that has given them information to set the redline lower than 9k.

*I am hardly an expert, just sharing what I see on differing perspectives around the question.

 

We haven't changed the valve switchovers on ours by more than a few hundred rpms - they're pretty good as they are, even that was mainly to stop the car dropping right into a valve changeover point on a gearchange, which was doing funny things to the fuelling for a split-second.

 

Wow, great thread/information Eric! I definitely just lost the first hour and a half of work carefully reading through pretty much every post in here.

I'm not familiar with the Koni series so I'm not sure what the rules are, but with all the time and attention to detail you put into your engine work, I'm curious if you spent a similar amount of time looking at the car's aero setup and balancing downforce vs. drag and if so, what you could share about your experiences?

Similarly, I can only imagine you spent just as much time paying attention to detail while setting up you suspension. Given that, do you have any shock dynos stored away you'd be willing to share?

 

Correct me if I'm wrong, but I believe Koni Challenge only allows the use of factory bodykits/parts as well..thus all Koni Challenge people are using Mazdaspeed. Again, I may be wrong..but from what I've seen, thats what it looks like. I also noticed no one uses the Mazdaspeed rear diffuser except Speedsource in the GT Rolex..which I find interesting.