OP, I suggest you start pre-mixing (yes even for S2), obviously pre-mix is not going to get up to VDI straight away, but 'vapors or oil residue' will over time, say after a full tank of pre-mixed fuel..

I pre-mixed (S2) from the day I took 8 off the showroom floor, everything is standard, and she revs as smooth as silk, as far as I want to take her, But, I don't get in the habit of going past beeper, it is pointless, and IMO does more harm than good over the longterm.

I did have my VDI stick/hesitate once, it was a very humid/hot day...did I say humid, I think it was reported as 85%...anyway, I put it down to this, it did it once and has never returned some 20K later..

There was an S2 guy here about a year ago reporting similar issues (no Dyno) but he did not pre-mix, after I suggested it and about a tank later he said his issue never returned.

You will be surprised how much better your 8 feels, drives and performs with some pre-mix.
Personally I believe your car needs a good thrashing (with pre-mix).
I also do not believe you have Ignition issues.

 

Thanks, it will be getting exactly that this weekend. Should be fun :-)

https://www.rx8club.com/rx-8-racing-...9-10-a-242436/

 

Keep us informed...

 

PM Sent to OP over this temporary thread closure..

 

sooooo ....................... any the wiser ?

 

Had a PM talk to the guy (going on memory)....

He said he could not feel any ignition missing @ high RPM, however he said he believed that the previous owner did not do much hard or spirited driving.

Anyway I suggested he pre-mix to help on a permanent basis and he was taking car out for a track session around now (this weekend).

He said he will come back and report...

 

If we are looking at S2 dyno's... I'll throw mine in. The AFR line is hard to see but can't seem to get it darker. PLM AFR numbers at bottom are Min: 11.0 Max: 13.0 Avg: 12.2...

I regularly see 11.1 per DashCommand OBD connection when accelerating. Cruising usually around 14.5ish

 

Wow .. is this from an Automatic or MT?

 

Sorry, should have posted. 2009 Mazda RX8 GT Manual. Was around 60K miles. Only change from stock is BHR ignition kit. Dyno before this one iginition coils were going bad. Replaced with BHR, regained about 5 HP.

 

wow indeed ! There is more going on than just over rich .
Check:
VDI
SSV
Compression

 

Brettus, thank you. This is a bit over my head mechanically, so have reached out to a fellow board friend to assist. Hopefully between the two of us and Jon316G's video I won't be without a car for a while. Since I am still trying to learn cars in general and my 8 specifically, would either of the VDI/SSV explain the richness? Or do they have no impact on that whatsoever?

 

Well I took it on track with premix and it felt to be performing well. No way to replicate the dyno, but acceleration felt smooth and linear all the way to the limiter. So much so it surprised me to hit it a couple of times. It's hard to hear the beep with a full face helmet on and windows down...

I was able to log some data. AFR (edit: I mean MAF) levels out at ~220 a little over 8000 rpm. Just based on some searching here I think that looks ok, and so means the various intake valves are operating correctly.

A plot of RPM vs time looks smooth up to ~7500. It does have some minor wiggles after that which may or may not be normal.

AFR is reading as a flat 0.76, which tells me that it is actually running richer than I am able to read. Presumably that is a ratio to stoichiometric, so actual AFR is below 11.172. Unfortunately that limitation of that factory sensor (or my data logger) means I can't see the curve to compare with my dyno result from earlier.

Screen grab of data attached.

 

I feel a bit better now... How about plugs, were they changed with or after the coils?

Would low compression do that at high rpm?

 

At 60k I did the BHR coils, wires, plugs, oil change, man transmission fluid, diff fluid. This dyno was done about 1k later. Am now at 81k. Just pulled and cleaned spark plugs last weekend. I do what I can to keep it running as best as I can.

 

For what it is worth, here are a couple of edyno plots based on the obd data I collected. I've stared at these for some time but could not convince myself the accuracy is good enough to make any conclusions.

 

Interesting. What are you using (hardware/software) to collect the data?

 

It's an aim solo dl and the software that comes with it.

 

So just to update regarding my dyno. Since it was mentioned to check SSV and VDI, I began reaching out to those nearby who are more expierenced than I. TeamRX8 was gracious enough to meet up and check things out. He was able to reach in and both turned super easy. As some others around the forum have mentioned it looks like the first step will be to get it tuned to the BHR kit and adjust the dwell. Here's to hoping that tomorrow goes well...
Thanks again TeamRX8...

 

After viewing the two dyno graphs, 1st one with OE coils and the 2nd later one with the BHR system on the OE dwell map, and also hand inspecting the actuation of the SSV and VDI valves, I stand by my previous assessment posted earlier.

You can clearly see that the SSV is operating fine by the power curve through that rpm transition area, and it also seemed smooth during my hand operation of it. You can also see that the APV valve is opening at the factory programmed rpm point with resulting flow drop, but then the power curve goes off from there. If you compare the OE coil dyno graph and the BHR on OE dwell dyno graph you can see there is much more impact on high rpm power with the ignition upgrade. At the same time, the AFR is going very rich; low 11s, after the APV opening point.

Those of you have been around a while will recall that when the BHR system first came out there was a hiccup when it was realized low AFR and OE RX8 dwell is not a good mix with the GM truck coils. It was most apparent on turbo cars; high load, rich AFR. This is when a multiplier factor was rushed out to up the coil dwell. As we've learned since, while this factor helped it still isn't ideal. The GM truck coils don't really wake until you get the dwell up into the 3.5 - 5.0 mS operating range. Making some assumption here because we still are not 100% sure on how well the S2 dwell map mimics the S1 map, but the S1 OE dwell map is kicking out less than 2mS dwell at higher rpm, exactly where the power is falling off here. The prescribed multiplier factor was still not increasing it enough in that range and there is a whole other thread/discussion on this elsewhere on the forum..

Because the power curve is so fubar at hight rpm the VDI operation is not so apparent. By hand it moves very smoothly. Even if the VDI doesn't operate the power curve only flattens rather than oscillate wildly with a big drop. My assessment is the VDI operation is fine.

One other possibility is that the cat converter after 81k miles may not be flowing as well as a new one, but not be heavily plugged enough yet to cause a significant problem everywhere. This would have more impact at high rpm/load than when the engine flow through-put is lower. Just a guess at this point. If this were an S1 the thing to do would be to tune the AFRs into the 13.0 AFR range and reassess the resulting change. A midpipe could also be swapped in and compared against the existing cat pipe.

There might be some issues that are helping to drive the AFRs down and contributing to the issue, but low AFR and resulting low power is a fairly common issue with the Renesis. At this point I don't think it's either the intake valves or the ignition system. It actually got worse with the ignition upgrade, which is what I would expect on OE dwell with AFR in the low 11 range.

 

Interesting, so with no tune, meaning oe dwell times and oe afr, bhr coils might not do as well as fresh oe coils?

I also don't think I have any intake valve issues now and have ordered an hei spark tester and a compression tester to try.

 

I've advised against using the GM coils on S2s in other threads because there is no way to alter the dwell settings

https://www.rx8club.com/aftermarket-...t-work-171852/

 

....

 

just curious to know what the datalogging at Dynotronics showed?

 

That is a long and painful thread and the summary seems to be that if you are FI, then you need to modify the dwell settings. Stock, or NA should work fine with the stock dwell settings. Since FI needs a whole bunch of tuning anyway that does not seem too big a deal. Not stated is whether the stock settings result in more, less, or the same energy per spark as working oem coils. If it is the same, you are simply buying longer lasting coils, more, well that is a bonus, less would be a bit of a disappointing, but perhaps still better than stock coils that fade (assuming they do on an s2 which is another debate).

 

I can tell you that (for S1s) startup spark with D585 coils on stock dwell is INFERIOR to stock coils.