The first dyno on this thread with the 'W' thing going on seems to indicate that the vdi does open on que but then the way power drops and then takes off again suggests to me that the VDI is responsible for that.
How about a scenario where vacuum in the VDI actuator is leaking through the diaphragm and allowing the spring to close it .Then it gets reopened because somehow the leak seals itself with the diaphragm in a different position.

That's what it looks like to me and I would be Testing that the vdi actuator holds vacuum :)

That's entirely possible. The energy stored in a better coil charged for too-short a time may be less than a relatively poor coil. Why? Inductance!

https://www.rx8club.com/engine-tunin...8/#post4313860

TeamRX8 is correct in stating that extending the dwell to 5.4 msec is optimum for the coil. I'm essentially using the so-called Oltman dwell settings however from concerns about duty cycle and the amount of current being drawn through the stock wiring harness.

https://www.rx8club.com/engine-tunin...8/#post4313928

Boil down: 5.4 msec if duty cycle is less than 50%, or a dwell which gives 50% duty cycle if 5.4 msec would give higher.

Another s2 dyno is posted here: https://www.rx8club.com/series-ii-af...2-dyno-244980/

In reply to that post (and somewhat summarizing this thread so far):

Every car is different. How many miles on the car, and when did you last do plugs, or coils? The other thing to check is the various valves in the intake.

The AFR is normal for these cars. Mazda do that to keep exhaust temps down in order to protect the cat from burning up (rotary engines have very hot exhausts). Tuning has just become a possibility, but if you do that, you need to ditch the cat, or be aware that you'll be buying a new one in the not too distant future.


On my own result, I have not gone as far as checking the vacuum holds. I can say the valves move freely.

Sorry it took a little bit to get on here but in regards to my dyno, I just replaced the Coils and wires the day before and cleaned the plugs (under 6k on the plugs) and i have 41k currently on the car.


The AFR's were somewhere in the low/mid 11's btw

So, I just had another dyno done...
Since last time, the car has a mid-pipe, new coils and leads and a mild tune (basically just leaned out the higher rpm's). Just before the dyno the car had a 20 minute track session, with some premix and it has also completed a bunch of track days since my original dyno.

Now looks clean, smooth and healthy to me... I actually think the coils made the difference at the top end although it is also possible blatting it around the track cleaned something out.

Everything aside from the mid-pipe and tune are stock.

https://www.rx8club.com/attachment.p...1&d=1378246478

Sorry bro. :( But unless another RX-8 ran the same time as you then it's not all bad, the dyno could be off in your favor.

Yep looks sweet now . Pity so much was changed that you weren't able to confirm what caused the 'W' .

Subjectively the coils & leads made the biggest difference. My guess is that fixed it. It seemed to me the car ran a little smoother, had a little more tq and less stink at idle with the cat off after I changed the coils.

I have swapped the cat on and off a few times (now back with cat) and I can't say I notice any difference with that except for the sound. I could be wrong though.

A couple of other notes:

On they dyno IAT varied quite a bit. The first run started at 100F and dropped to 96F. It increased steadily from then on, the 2nd run it was 100F for the higher rpm and then 110F for the 3rd run. On the track, IAT remains almost at ambient, climbing just a few degrees when running behind another car. That means that any intake mods to provide cooler air on the dyno won't actually make any difference on the track. Of course, more flow will still help if that is possible.

Also, the shop reading for A/F was leaner than the oem sensor. They start out about the same, but at higher rpm (hotter and richer) the oem sensor reads 12.x while the shop sensor was reading 13.x

Both car and shop read richer in the last run (when temps must have been higher).

Per the shop readings I am running too lean, so not sure what to make of that.

This seems true for all rx8s . Aftermarket guages tell the same story in general . So .........always tune on the rich side of your target AFRs !

Bringing this back - it's not far from what my car saw at Lucky7s a few weeks ago. 190hp and 138tq, RB intake, midpipe & catback, all else stock. I'll have to find the graph and post it. Couldn't tell you the conditions though - I wasn't there and they were trying to diagnose another issue... I was pleasantly surprised!