Diagnose my S2 dyno
 

Stock 2010 series 2, new plugs and air filter. Original coils and leads at 24.5k.
It looks to me like I'm not making full power at the top end and I don't think I should have the 'w' shape. Is this a possible intake valve issue, ignition, or something else?

I tried searching for an hour or so on here and could not find a similar graph... but searching for 'dyno' is like searching for a particular piece of hay in a haystack.

Ignition issues seem to show up as erratic power (squiggly line) which I don't seem to have?

Thanks!

Ignition COULD be going out, just because the service manual says switch @30K doesn't mean they'll be 100% til then. Just my .02

Also, you need to spank it more. Seriously, I make more power on the drive cycle after a good spanking, clears all the carbon out.

The slight hiccup at 3,750 and 6,250 is normal, but I guess the top end squiggle could be attributed to my ignition theory.

Hope that helps.

P.S. Oil changes? Engine, tranny, diff...

^thanks

I did find this: https://www.rx8club.com/trouble-shoo...9/#post4302095

so I guess SSV or VIV is something to look at. AFR seems to drop at the same time, which could be another symptom, could be normal, or could be a sign of a different issue :confused:

And yes, I have just changed engine, tranny & diff oils.

I hear you on the spanking. I suspect this car has not had much of that before the start of my stewardship and I rarely rev it that much during my DD. The first run on the dyno was noticably lower in power than the following 3 and did eject a little bit of dark smoke. I am going to have it on track this weekend so that should clear it out, or kill it if my ignition fails :scared: That's what I'm trying to work out :-)

Awesome, mine sputters if I DON'T spank her ;) Lol, it won't die if your ignition fails, at least not this early in the game. (Could cause cat problems later in life.)

VIV could explain the power cap, but not the W-shape.

Let us know how it goes :)

P.S. I think the VIV would throw a CEL, not entirely sure though...

Hmm, I still have not worked out what or where the VIV is... I did go out and push open the VDI and SSV valves. Both seem to operate smoothly, although the VDI valve squeaks a bit over the first third of its movement. This is with a cold engine bay. Not sure if adding some heat will change anything. I also took a look at the MAF sensor and that looked very clean.

That VIV valve will get you every time - very few people know anything about it . :suspect:


Another possibility is that the VDI valve is oscillating somehow to cause the little known ' W effect' - this combined with an ignition tracking/coil issue is my best guess as to what is going on here .

"should" be nothing wrong with a low mileage 2010....

What does your Dyno but 'feel'???

Is there any hesitation @ 7600-7900??

You really are getting close to max power, as many have said before around the 8K mark you enter the black worm hole.

Next to no benefit going past that RPM line...in a stock set up.

Ok, I'll bite: wft is the VIV?

And yes, I searched. :angel:

New top secret Brettspeed product, I bet!

Yeah, it's getting really hard to distinguish the comedy from the serious statements in this thread...
[SERIOUS FACE ON]
I searched a whole bunch and as far as I can work out, VIV might stand for variable intake valve. The comment I linked above is the only place I have found refer to it in this way and I am now not sure that comment is completely technically correct. There seems to be some better info in this thread:
https://www.rx8club.com/rx-8-discuss...rts-rx8-15622/

and here: http://www.starmazda.com/competitors...isTutorial.pdf

So, the VDI valve opens at 7250 rpm and you can see an appropriate dip for that in my dyno plot. The question is, why does my power dip a 2nd time just after that?
[/SERIOUS FACE ON]

VDI is broken maybe

https://www.rx8club.com/do-yourself-...valves-174009/

Thanks for chiming in here Ash. I really appreciate you passing your eyes over this and the multitude of informative posts you have on this board...

I don't really have my "butt dyno" calibrated well enough yet to rely on it, but have not picked up on any glaring issues. I'm going to have to drive it more before I can answer your hesitation question with any certainty.

I agree, there "should" be nothing wrong, but that 3rd power dip at ~8000 rpm does not look completely normal to me. I was able to compare results with two other RX8s at the shop and neither of them had this. One made less power up top and apparently had some known issues. The other made more from 7k onwards with a plot that carried on up and to the right where mine levels off, but was running a 13:1 AFR so must have been tuned. Both had the 1st two dips, but not the 3rd.

As soon as you find out who Viv is you can ask her what her valve is doing .


Like I said the first time . Looks like the VDI is opening and closing on you .

And I do think you are losing power to another issue on top of that as well - ignition related .

Thanks Brettus. I'll check with Viv on Friday night ;-)

OK, I'll go spend more time trying to diagnose the VDI, and coils...

Check out Jon's excellent thread, and yes VDI..


How often do you 'exercise' higher RPM's 6900 +?

The Series 2 Inlet manifold is slightly different than his S1, (mainly different hang on parts) however the principal is of operation is identical.

I am very surprise such a low mileage S2 has this issue..you are going to have to investigate, you could have an issue with 12V Solenoid Valve which controls Vacuum to VDI Actuator, although intermittent problems usually don't exits, the 12V solenoid either works or it does not.
Or Actuator on VDI?...I don't think either of these.

IMO I believe you have some carbon build up which is causing a sticking motion of VDI, opening and then closing, it is working but not smoothly.

Have you or do you ever run pre-mix (in gas/fuel), currently also winter where you are, extra cold could be making it stick with carbon/soot build up....it needs some manual exercise, do you have a Mityvac to connect like in Jons Video?

Do a vacuum check on your VDI actuator to make sure it holds vacuum . When you see Viv you could do a similar check on her as well ....

snap!

disable the vdi and dyno again?
But actually I think something else is going on. !st place to look is coils and leads.
But- ---and this is a guess--injectors too?
I see the a/f's swinging back and forth during that dip?
I also wonder about compression---161 is low?
Hows the cat?
It could be a lot of things....

I am of no help....

OK, thanks, I do have a vacuum pump but it might have to wait until the weekend before I have time to hook it up to the car. I did try pushing the VDI valve open again by hand with a hot engine (carefully!) and the behavior is the same. Smooth operation with a slight squeak over the first 1/3 of movement.

So far it has not seen high rpms that often with me, but I have only had it a couple of months. I can't be sure how the previous owner treated it, but my impression was that it was not driven hard and also not driven very much or for any distance during the last few months of ownership.

I have not run any premix yet, and I doubt the previous owner did, but I will be using premix at the track this weekend... Perhaps that will be enough to clear it out :-)

dont run the cat on the track!

That chart looks about normal as far as my ass dyno is concerned. I don't really rev mine past 7k because it just makes more noise and power drops off like yours does. The myth that these cars pull hard to redline is about as accurate as the "vtec kicks in so hard" myth lol I guess it depends on the gear too because I know first is so short that you can't really tell as where 2nd and 3rd are more noticeable because there's more time spent in the rpm range. Idk though just my 2 cents but I honestly think you're chasing a non existent problem. On a side note that hp number makes me feel really sad :'-( lol

It's no myth - . Suggest you get yours checked as well .

compare the above dyno to this one .........

https://www.rx8club.com/tech-garage-...3/#post4408918

Yeah brettus your power also dropped off before 9k! Sometimes I think it's just me because sometimes the car feels different depending on wether i'm well rested or if i've been up for 24+ hrs working lmao Do you guys have some more graphs? Maybe an isuzu dyno sheet to compare with?

Yeah - I guess you are right - practically fell on its face :uhh:

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.