pelucidor

I can just imagine:

Yup, that's a damn fine looking engine. Look how shiny and small it is...

altaic

Hold on a second, please. I didn't know about Skyline Maniac's reputation before you mentioned it, but I think his comment has a point.

Given:
- Mazda knows of the issue, and has since the first dyno, around July 18th.
http://www.rx8forum.com/showthread.p...5&pagenumber=3
http://www.rx8forum.com/showthread.php?s=&threadid=6890

- The power at the wheels should be about 204hp to 207hp.
http://rotarynews.com/view.php?id=193

- There have been three dynos, in three different areas, showing the car to be 20hp to 30hp underpowered.
http://www.rx8forum.com/showthread.php?s=&threadid=6890
http://www.rx8forum.com/showthread.php?s=&threadid=7533
http://www.rx8forum.com/showthread.php?s=&threadid=7863

Speculation:
Let's review the responses Mazda is likely to make for the three scenarios regarding the low hp dynos:

1) Design Flaw
If the car is indeed supposed to be producing 247hp at the flywheel, and it is instead producing 20 or 30 less, Mazda will hold out on breaking the news until (a) they have a fix, or (b) the media threatens their sales. It's possible they'd even preform the fix at a scheduled service and not tell the car owner, and wait for the media to pick up on it. I also wouldn't put it past them to stifle internet communities' reaction via anonymous interjection.

2) Design Feature
It's possible the car underperforms on dynos which are not specially designed to test it (like the bmws with front wheel sensors). Another possibility is the ECU that is designed to remove a cap or change air/fuel ratios at a certain mileage or at a scheduled maintenance, to aid engine break-in. In this scenario, Mazda will tell people ASAP, at the least to avoid misconceptions in the media, or even better, to keep their enthusiasts happy (they hope to cater to the enthusiasts for the new RX-7 if their flagship RX-8 does well).

3) Dyno Flaw
This is the easiest for Mazda, because they have a dyno at their disposal, which they know is in perfect working condition, and you can bet they've already dynoed several cars since hearing of the issue. They can easily issue a statement that the consumer's dyno results are wrong, and their cars can be sent to the dealer for inspection. Similarly to scenario #2, they'd want to act with all haste to keep the media from publishing misconceptions.

Conclusion:
Since Mazda has had three weeks to consider their position, and their flagship vehicle is of utmost importance to them, it seems they have not responded as though they believe it's scenario 2 or 3. I think a month is more than enough time to straighten out misconceptions; their PR dept. should have taken care of that in a week's time, or at least before the next month's magazines come out.

Therefore, I believe there is a problem of some sort, and we can either sit and wait for word which will be very slow in coming (perhaps never, if there is not a fix, and no one outside the company investigates), or we can compile our findings, as well as email addresses of owners and others concerned who are considering buying the car (names in the media are very good to have on the list, as well). Then on the 18th or thereabouts (one month since Mazda has known), contact Mazda as a single entity with the document, and leverage contacting the media if detailed (feature/flaw in the car) answers don't come out within a week.

They know that more cars will be dynoed soon, and their answers had better match those results. Lying would prove to be a bad move.

That leaves enough time for them to respond, and enough time for the information to be published in the next month's magazines if they don't respond.

I'm not one for causing trouble, but I think tucking one's tail between one's legs is not the right thing to do. The corporation's interests are not always the same as the consumers'. Further more, there are a great number of people waiting for the information before purchasing an RX-8, and some who have decided to look elsewhere; Mazda should be told that they would benefit. It would also be kind to those who are already committed to their purchase by allaying their fears.

pelucidor

Very well put Altaic.

I agree with your conclusion as well, except that Mazda may not have known about any issue at the first dyno (single instance shows no trend), but they should by the third dyno from Compaddict on 7-30-03 which even includes the graph and all environmental conditions. Certainly I and others I am aware of only contacted Mazda at that point so they have only had a week so far to investigate and prepare.

I suggest we let Mazda's slow-moving PR people have until 8-31-03 to tell us what is going on, and then go to Mazda en masse for clarification. By mid-August I will start to think the 'good news' options (2 and 3 in your post) are unlikely.

turboMX5

I am watching this thread with much interest. I personally own a turbocharged MX-5, and am familiar with ECU mapping and air fuel ratios for my car. That said, I know little about what A/F a normally aspirated rotary engine needs for best power.

The posted dyno chart that logged AF read all the way down to 12:1 AF after 7000 RPM. That is a fairly rich mixture that is appropriate for about 12psi boost on a piston engine, such as my car. This seems extremely rich for any normally aspirated engine. Can anyone else confirm this would be true also for the Renesis?

Also, in a boosted app at least, the A/F ratio should be stable from peak boost to redline. The RX-8 logged A/F drops all the way to redline where it is in the neighborhood of 12:1. I would have expected to see something much more constant after WOT onset.

Also, a VTEC hit, such as on the S2000, will give a JUMP in torque, right as the profiles switch, due to the increased VE and CFM airflow at that point. The 3-stage intake of the RX-8 should provide two similar hits noted on the dyno chart where these additional ports open (the first being open during regular driving, the other two open at later RPM setpoints).

This being true, why do the dyno graphs show torque DROPPING at each RPM setpoint? Seems to me that the engine is not getting the additional air that we would expect from the opening of another intake port, or that the ECU delivers too much fuel when these RPM points are reached.

The engine in my car (1999 Miata engine) has a VICS variable intake system that switches from long intake runners to shorter intake runners at 5300 RPM. At this point on the dyno graph, torque visibly rises and holds to redline. Basically, with a markedly superior setup on the Renesis that actually DELIVERS more air by definition twice in the rev range, I would expect to see at least similar results if not better than with the VICS switchover on the 1999 and 2000 MX-5.

Something seems fishy to me...

Kurt

turboMX5

Also from the dyno charts, I see where the second intake port opens at ~4000 RPM, and I see where the third intake port opens at ~6200 RPM.

What happens at 7200 RPM that delivers the same dip in the torque curve?

Kurt

P00Man

many people ahve speculated that the ECU deliberately drops the AF ration to protect the engine during break-in periods
which explains the drop in torque and stuff youve pointed out as being awfully wrong for peak power

eccles

Actually, one of those lower hiccups (I forget which) is caused by an external valve which alters the characteristics of the intake tract. The final 7200rpm hiccup is the third ports opening.

rx7aggie

they aren't talking about hiccups here. if i'm reading correctly, what they are mentioning is the overall degrease in torque after the ports and intake's open and change, respectively. notice that after the 2nd and 3rd sets of ports open up, the torque drops significantly and fails to ever reach the maximum torque produced from the previous set of intake ports.

i have edited the toque curve to show what i think is the general trend, and how it seems to be going from the previous port opening data.

as you can see, it seems opening the 5th and 6th ports is parasitic, causing the car to loose torque and peak hp. it seems the torque between 6300 and 7400 was greating increasing and by leaving that setup alone, the car would end up producing more toque and more HP further on down the curve.

i agree with turbomx-5. you'd think with a change in ports and intake setup, you would get a net rise in torque, not a decrease.

delhi

For those who are new to Mazda, there was a similar hp issue with the miata as well a few years ago. But the power loss wasn't this dramatic. only about 7hp. I'm not sure Mazda ever compensated the owners.
I know for a fact that Ford actually recalled the Cobras and have them retuned with modified headers and some engine work to regain the claimed hp figures. I really really hope Mazda would rectify this issue....if indeed is an issue.

KyngNothing

I'm sure somebody will come in who knows exactly, but Mazda either bought those cars back, or gave free extended service etc on them... for 7.... I doubt they screwed up 20, but maybe that's just me...

BillK

I won't go into detail here because this is covered in other posts, but basically Mazda gave Miata owners two choices: Free maintenance for the length of the warranty period or they would buy back the cars.

Now, to comment once again on many folks' "Mazda must tell us something by this date" demands, fact is Mazda's a big company and if you know anything about big companies it's that announcements about things like this come slow. Even if it was something like the RX-8 cannot be dynoed on a "standard" dyno they would want to cover all their bases and determine exactly why before saying a thing.

As I've stated before, I would be rather surprised if Mazda makes an announcement within a month, because frankly it's the concern of a bunch of enthusiasts at this point, and most potential customers don't even know the 8 is out yet let alone know about any theoretical power issue.

Remember that BMW only really addressed the E46 M3 engine issue when AutoWeek reported on the web site reports, and even then a majority of potential M3 purchasers know nothing except their engine warranty has been extended for some reason; if there is an issue and Mazda plays their cards right potential 8 owners would be similarly oblivious and just think "Gee, the 8 comes with free maintenance - cool!"

Lethalchem

Good point! I didn't think of it that way, I was just trying to present an encouraging possibility.:D

eccles

Which was exactly my point in an earlier post (in one of these damned dyno threads). I strongly suspect that because these dyno runs are being done in 3rd gear, the engine is spinning up too fast for the system to recover from the extra turbulence or whatever that is caused by the opening of the extra ports. I suspect that if the runs were done in a higher gear, so the engine reves up more slowly and has a chance to recover after each change, that we would see a rapid recovery back to almost the same HP as before each port opened, and climbing again from there. But nobody else seemed to want to pick up on that point at the time, for some reason.

Quick_lude

I thought the dyno with the 2000mile engine was also done in 4th and 5th gears but since the results were almost identical Compactaddict didn't post them up. Maybe you could ask him if he has the plots of those runs for comparison.

pelucidor

Yes Compaddict said that the 4th and 5th gear runs were about 1% less - within the bounds of measuring error.

turboMX5

Based on my experience with switching the variable intake on my Miata, I would like for someone to try something on their RX-8 and see if the power feels any better.

I bet the engine has two butterfly actuators, one for each of the additional ports. These will be controlled/switched by a solenoid near or on the plenum. If it is like my car, the extra chamber is held closed by a +12V current to the solenoid, channeling vacuum to the actuator that holds the chamber blocked off. At the ECU's RPM setpoint, this circuit is broken, removing the vacuum signal, that opens the butterflies for the extra chamber or plenum.

Judging from all the dyno charts I have seen of the 6-spd, the power could benefit from NOT switching to the auxillary intake ports, for whatever reason. The quick and easy test for this is to wire the intake actuator in its idling/rest position.

Alternatively, the same test could be done by wiring the actuators in the open (high RPM) setting and seeing that difference. I'm sure you could learn alot from this, especially if someone was to test this on the dyno.

If anyone on this list is in the DFW area, I'd be happy to explain further and show an example on my turbocharged MX-5.

Kurt

omahawk

One of the threads about this in the tech forum stated that there are not vaccum tubes and the the actuators are electronic/computer controlled. So this may not work, however I may be wrong.

neit_jnf

There seems to be a bit of confusion as to how the intake paths and ports work. I hope this helps:

omahawk

Neit,

Great post. I was wondering exactly how the ports worked.

turboMX5

Or in this case, how they don't work. They look to be a detriment to power. Maybe they only half-open or something? The torque should NOT drop with an advertised positive effect from resonance or from additional port airflow.

I bet a solution will be found rather quickly.

Kurt

Racer X-8

Yeah, I was seeing that "projected torque" loss from day one of this quandry. I have dismissed this to myself though, believing that the "projected torque curve" would most likely nose-dive, like that of a hp curve after about 400 rpm or so into the projection. Still though, I feel like you that there is something basically wrong right here, I just don't have what I would need to analyze it at all.

RomanoM

Sputnik

This thread is turning into a repeat of others, so let's keep it all in one place on this thread.

---jps