P00Man

Church, did you notice change dramatically from below 6000 rpm to above 6krpm?

becuase the other AF charts showed more or less "normal" or "correct" ratios below 6000 and then dramatically changed to those more abnormal ratios above 6k or there abouts

i cant really read the AF ratios in those shots, so thats why i ask

ChurchAutoTest

If you'll closely at the new, enlarged pics, you'll see that the RX8 starts off relatively lean, but by 4000 rpm has dropped down into a richer state that is more in tune with how modern cars run at full throttle.

Many modern ECU systems actually try and run near stoichiometric for short applications of full throttle by using cheap widebands as the primary O2 sensor. We've seen this on Acura RSXs and even some of the newer Ford products. Ostensibly this is to improve emissions performance, but once the ECU realizes you intend to keep your foot in it (time based? Who knows) it goes to a safer WOT mixture. In the case of the Dynapack, we always do a loaded stabilization before the run begins, so the car is being held at WOT for 2 seconds at 2000 rpm before the ramp begins. On a Dynojet, you're accelerating as soon as you go WOT, so any attempts to run stoich (if time based) will go rich later than we did on this test.

I think its important to point out that on a NA engine, going from 12:1 to 13:1 is not going to free up much power. 2-3% is a normal number. The mixture is not the culprit here, something else is cramping the top end power.

SC

rxphink

By the look at how quickly the curve falls off after 6000 I would have to say that timing and intake restrictions are the two most likely culprits.
Did you guys happen to notice if the throttle plate was opening fully?

The A/F is still too rich it should be in the 13's, this is based on previous experience with N/A rotaries. My old '91 would run in the mid/high 13's at the top end and this is with an even less efficient port design. The renisis' port design is bay far better at scavenging the unburnt A/F mix and sending it back around to be burnt again, so I would expect the A/F readings to be much more lean in with the renesis. I would also expect them to be a bit different based on the fact that the renesis uses speed density vs. the old N/A 13B's mass air system since the renesis has the ability to compensate for barometer and temp.

Now another question, wher are the A/F ratios being measured?
Are you removing the stock primary O2 sensor?
If so this might be a problem since the stock primary O2 sensor looks to be a wide band sensor. By removing this from the pipe the ECU may be freaking out and dumping fuel. If your getting it from the tail pipe, then damn it must be RICH before the cat.
With the wide band stock sensor the car would be more likely to try and manage the A/F ratio all through out the rev band.

Aesculapius

I have noticed a lot of debate concerning the validity of a dynojet because of unknown drivetrain loss.

Rotary News posted an article here:

http://rotarynews.com/view.php?id=198

The subject of the article deals with a company developing aftermarket parts for the Renesis engine.

Pictures in the article show the engine attached to a brake type dyno.

Has anyone heard the results of this test?

akrx8

you guys might find this intresting regarding not being able to get info from a scan tool thru the ecu.my last car was a svt focus and ford has a new encripted program they have in this car only.have spent alot of time on svt forums and found that not even diablo or superchips have been able to get into it to build performance chips.it is a flashable system that dealers only with special softwear can reflash the system.my svt went thru 4 reflashes in 7 months with the supposed new and better program and each time the car was diffrent.this may or maynot be the same or similar system in the rx8 but if this is its a very advanced computer and im thinking(hoping) that we will get are power back wether its automatic after a set mileage or we have to go in for a ecu reflash,just hope they let us know soon so we can talk about all the great things this car can do. :D

eclps0

maybe the ecu is restraining power to protect the engine from over heating.

1 rx7s have overheated and alot of problems with them beacuse they were not cooled down as much as they should have been.

2 the rx8 on the dyno it has two oil coolers, a BIG radiator, and the intake.I personly dont think it had enough air cooling the oil coolers, the radiator, and air going into the intake.beacause in alot of post people r saying the car is freaking fast someone also compared it to the evo with the power delivery i donmt think he would have compared the two if the rx8 only had 220 crank HP and 184 rwhp.

rxphink

The 3rd gen RX-7's used to overheat because of teh heat that was retained in the engine bay. My FD withstood many a hard drive on a 110+ degree Texas day. The highest water temp I would get was 99C and that was after running fairly hard with only one oil cooler and just a Mazdacomp upgraded radiator. The R1's and R2's would be a few degrees lower with the second oil cooler. My 91' N/A RX-7 would usually only go up to 88C in the same temps.
With the better cooling of the RX-8's huge front openings and lack of heat retaining turbos I would have to guess the temps would be around the 88C range.

Keeper

If this were true, the runs would not yield consistent results.

Keeper

I've read that the 8 can be shipped with two "types" of emissions equipement ... emissions equipment which conform to federal standards, and equipment which conforms to california standards (states other than cali implement cali standards).

... of the dyno runs published so far, what emissions spec was the car shipped with?

rxphink

Here are the torque curves that Mazda has released so far :




See how flat the curves are, that is the same shape that I have seen out of every properly running rotary I have ever seen/tested.


With the sharp fall off of torque seen in the graphs posted lately I'd have to say that there is definately a tuning issue or intake air flow here.

Hopefully someone who has dynoed their car or someone who is plannying on dynoing their car will read my previous post (just a few up the page) and get some definate answers to my questions. I have a feeling that with just a bit more info we can make some pretty good educated guesses.

I'm going to atempt to get my car on the dyno pretty soon and see how much data I can gather, but the more reference points we have the better.

One more thing I've noticed is that when cruising down the highway and then down shifting to say 4th I get a higher reading on the "Butt Dyno" than I get when starting from low RPM and running through the whole gear.

Reminds me of my previous RX-7 when the 6-ports weren't opening up properly.

TerenceT

how about doing a run with no air filter? that would solve the air restriction problem somewhat and we'll have prove to buy or not to buy K&N filters (or cold air intake) when it comes out

i work in torrance and would like to visit you when you do the next dyno

how about partially turn off dsc? instead of completely disable?

ChurchAutoTest

- Not being able to read from the OBDII port is unusual. There is a standard government mandated specificiation for OBDII interfaces (so that mechanics, emissions facilities, etc. can read them) and this car apparently didn't meet them. My scan tool is only 9 months old...

- Temperature was not a problem on the dyno. The car was cooled between runs and the power output was extremely consistent on each of the three runs we did. The hood was open and a 6000 CFM fan was used to blow air into the radiator opening.

- The mixture was taken from the tailpipe, no O2 sensors were removed. Readings are usually slightly leaner after the cat. As noted before, the mixture is rich, but not unusual for a high revving motor seeking to maintain OEM reliability goals. Other cars run richer, and the S2000 runs similar ratios too. Even leaning it out a couple of points is not going to generate the missing power. Additionally, the power before 6000 rpm was exactly as expected, even with the rich mixture.

- The car was a CA emissions spec car

If I was investigating this, I'd ignore the AF mixture and look at ignition timing above 6000 rpm - if you can find a way to read it without an OBDII scantool (may need a Mazda unit - if anyone from a SoCal Mazda dealer wants to bring one in with an RX8, I'm game).

SC

neit_jnf

Just had a crazy idea, what if a dyno pull could be done with the auxilliary port injectors disconnected? Maybe that way the rich A/F mixture can be avoided at the top end. Of course I don't know if this can cause damage to the engine...

seikx8

Well, definitely this qualify as a crazy idea. I don't think anyone would want to do that to their car. We don't even know how the ECU is controlling the fuel and whether it will go into limp mode if injectors are detected to be missing. If not, you can do serious damage to the engine running at high rev without the needed fuel from that injectors. That's my random thought.

ZoomZoomH

iTrader: (1)

messing with the injectors?

that's just craaaaaa-zy!

Keeper

I know you probably can't get a fed spec car into your shop in California, but can anyone with a fed spec car that's been broken in get a dyno taken? I can't see the different emissions equipment accounting for the missing power, but it would be another datapoint and it could rule out another variable as the cause of the problem.

The other thing that would really bug me is that the ODB port isn't working ... it didn't think it was legal to sell a car these days that didn't conform to the ODB-II spec...

neit_jnf

All US RX-8 are CA emissions compliant, there are no differences between CA or elsewhere 8's.

eccles

The warranty reports that budaman and FUBAR were pulling prior to delivery, suggest otherwise - some cars showed CA-spec while some showed US-spec under "Emissions".

P00Man

i remember the other AFR's posted not getting super-rich (ie in the low 12's) untill after 6000 rpm, did you notice this Church?

or anyone else for that matter

reason i ask is because i remember the AFR's dropping rapidly as the rpms went to 6kish and beyond, pretty sure some other people pointed it out aswell

ChurchAutoTest

Check out the chart P00Man, it shows the AFR for the RX8. No real changes around 6k.

SC

LightEmUp

I thought I bought a car with 247 bhp, and hoped it would put out at least 210(15% loss) at the wheels. I go to my friends shop today and what do I see? Freaking peaked at 174. I'm pretty pissed right now, I want a 1/4 of my money back, or a car that performs like it's supposed to. Mazda you better get your act together cus people are gonna start noticing you guys fucked up.

P00Man

calm down, theres many threads on the boards cause of this already

the main concensus is that it is an ECU issue, due to the fact that the engines are running incredibly rich, and we know (thanks to the star mazda series) that the engines can put out the power

also, the engine isnt really broken in yet so that adds to it also, look around in the tech garage and check the sticky in discussion

P00Man

im too stupid to read those charts lol

i dont know whats for the 8 and whats for whatever else was being run for comparo. think its an s2000 no?

edit:
ok, i see what you mean, but im pretty sure that the other charts showed different (either that or im halucinating) can anyone dig them up and post them here?

i dunno how to post anything like that, otherwise i would

rxtreme

iTrader: (1)

If it is the ignition timing, that should be an easy fix, right? Totally controlled by the ECU. Do you think there is 20+ HP bottled up with that type of an issue?

If it is, the next question would be why. Would a radical timing adjustment be made to comply with emissions? I wish Mazda would start talking before lawsuits are taken.

TurboSE

I agree with church, it is normal to have 12.5 : 1 afr at WOT. I doubt Mazda would want it running leaner than 13 and even with that change you wont see 20 HP gains. Also, I am a little confused by the obsession with flywheel HP. The fact remains that what the car puts to the ground will determine it's performance and by the numbers it's putting out, it falls below it's competition. Sad to say but it just does not deliver the bang for the buck, atleast not yet anyway. I bet there is not much difference in performance numbers between the 4-port auto and the 6-port manual versions. Now if some of you could race the 2 versions and post the results.......