Here's another test that Mazda did showing the relationship between timing, the surface temperature of the rotor, and knock:



Look along the X axis of the graph. You can see that as timing is retarded, temperature of the rotor goes down and knock is suppressed. This is from Nagao, "Present Status and Future View of Rotary Engines" published in 1986 I believe. EGT's are important but all the discussion I see in SAE papers and OEM literature focus on the EGT affecting the life of the turbo and the cat more than anything else. I've got one paper where some NASA engineers ran a carb'd 12A at about 7psi and 15:1 AFR on 93 octane equivalent. Preturbo EGT's got up to about 1900 degrees and all they talked about was burning up the turbo.

Lower EGT's would be preferable but I'm not convinced that high EGT necessarily means knock and a blown motor.

 

While good information, something needs to be pointed out. @ 200% load, 7000rpms, the timing is back to 22*............

My peak tq is about 67-6900 rpms, running 17.5* and EGT's around 1650-1700.

What alot of people here are missing is timing.... not just the timing of the ignition but the physical TIME it takes to ignite and burn the charge. Nova's EGT's are so ******* high becuase the timing is so blatantly retarded that I would bet the combustion process is still going on after the exhaust port begins to open (stupid low tq numbers) and why it PRE-ignited, hot combusting gases entering an intake charge. There is a difference between auto-ignition and pre-ignition. I DOUBT this was a case of auto-ignition and more a case of pre-ignition becase of the overlap present, the slow burn from the AFR's, and the retarded timing.

 

Boost had dropped to 13psi at this point. The boost tapers off from the factory. That's how almost every modern engine with electronic boost control works. Even the FC and FD have boost taper off at very high rpm, but the Evo is probably the most extreme example.

On the subject of plugs: I believe the Evo X uses a 6 heat range plug with that factory 23psi tune (which is admittedly rich). In the world of very high boost, high hp piston engines a 9 is very cold. Remember that the Evo X makes 300hp out of 2 liters and the series 6 FD makes 255 out of 1.3 liters from the factory.

If you are saying that he had too little timing (too retarded) and that ultimately caused knock, I feel it is the complete opposite. If anything he had too much timing. If you look at how all these OEM tunes work, they use the timing to control knock and they use the mixture to control EGT (which affects life of the cat and the turbo). Here's the "low octane" timing map on an Evo X for when knock is detected:



If you look down the 220 load column you can see that when significant knock is detected, timing is retarded significantly--at least 6 or 7 more degrees versus the high octane map I posted above. The target AFR gets slightly richer as well, but in the interest of brevity I won't post the two target AFR maps right now. This is a factory tune on a car with millions of dollars worth of engineering in it that has an actual warranty.

EGT's are a highly controversial subject in the world of performance tuning. I respect your point of view and we'll have to agree to disagree. All this is academic though--if he had just hit overboost fuel cut, we wouldn't be having this debate...

 

the factory plug spec is 7 in the leading and 9 in the trailing. if you step to a 9 in the leading should you not put 11's in the trailing?

driving cycle is a factor also...

 

I believe you're focusing too much on peak torque here, which is important to know, but a little irrelvant here becuase the RPM at which the EVO makes peak tq is slightly different than where our RE's are making it. Mine for example is around 67-6900 rpms and I'm still 17ish degrees of timing.

I respect your opinion as well, I honestly do but I don't think your hearing me. Looking at the low octane timing map, 200% load, 7k rpm, timing is still 15*. He is running 6*

What does 6* of timing do as opposed to my 17ish.... it allows 11 more degrees of rotation before the ignition sequence. Which also allows 11 more degrees of BURNING exhaust gases to be introduced into the intake charge. Not to mention he is running too rich which will slow the burn as well. Again, this is why I believe his EGT's are too damn hot as well. The charge is burning too slow, and the sequence is starting too late. This, in my opinion, is why the thing is so low on tq/hp. I bet if he advanced the timing his EGT's would lower, and the tq would pick up as well.

He's also runing a BP motor which has much more overlap than my SP... hence more exhaust gases get introduced into the intake charge. And in this case, more slow burning exhaust gases.

We have no idea what the EMAP was, nor the hotside of the turbo so we can't even begin to talk about EMAP tuning.

I do agree that if the overboost had been setup correctly the engine would still be alive. However, that tuning is poor at best and waiting for enough exhaust gas to get in to pre-ignit the charge. When he overboosted the AIT's got hot enough, the EMAP got high enough, enough gases got in and the worst happened. This is why I say meth is nothing but a shitty band-aid to a problem that was concieved with the plan. Sure it raises the auto-ignition temp, but why build an engine that needs that to begin with? I know plenty of people with SP's and BP's making great numbers, no meth, no blown engines, nothing wrong with them and they are running what so many people consider AGRESSIVE tunes. I run 11:7-12:1 while under boost. ZOMFG!!!!!!!! THAT"S WAY TOO LEAN!!!!! YOU"RE GONNA BLOW IT UP!!!!! I also have what people in this thread are considering wildly aggressive timing. Yet my EGT's are 1700*'s on the street (granted 4th gear dyno pulls from 2-7500k they get in the 1800*range but that's a different story) and I'm making great power. How am I doing it

Less overlap and more timing and the engine would still be together IMVHO.

 

If you are arguing that generally speaking he should advance timing as rpm increases, the equivalent of centrifugal advance on a dizzy, then I agree (that's how I do things on my own maps). And that's exactly what most OEM timing maps do. They advance timing as rpm increases and retard timing as load increases. That's why you end up with a timing curve that initially dips and then ramps up. The shape of that curve and the exact number of degrees used depends on all these factors of fuel quality, porting, etc.

If I had the OP's engine intentionally running at 27psi I probably would have initially run 0 degrees (TDC) at peak torque and advanced timing up to redline. This is as opposed to setting fixed timing for a particular boost level that does not vary with rpm. Then when you have the car on the dyno you can see how much more timing the engine wants up top by looking at the shape of the torque curve.

In blue you can see the cells for the 28psi range in this old map I put together for a big streetport:



Depending on the setup, once you get to 7000+ rpm you are starting to leave the "danger zone" where knock is most likely to occur so you can play around with timing on the dyno there.

 

FWIW, racing beat runs 10* timing, zero split across the board in boost for testing, and 12* for racing. Nearly everyone on this board will tell you not to run zero split in a boosted engine. What works for one is definitely not to be considered fact, plain and simple.

Given the complex effects of a split ignition system and the combustion chamber design on a RE, any comparison to piston engine timing figures are pretty irrelevant. Also, anyone who says they understand the effect that ignition split has on the combustion event is completely full of ****. For some insight on the matter check out Barry Bordes' thread on combustion chamber pressure mapping, and he is only touching the tip of the iceberg.

TTT, don't forget that 11* crankshaft rotation is still less than 4* rotor rotation, which is something but not everything. I agree about the exhaust dilution being an issue, but combusting exhaust is not going to cause instant ignition of the incoming intake charge, otherwise PP engines would not idle whatsoever, they would just backfire out the manifold. A larger concern is the effect of auto-ignition due to intake charge dillution, I'm pretty sure someone covered that topic in a thread a while back, it was a good one.

Warning: save your fingers from arthritis before telling me I have not contributed anything to this thread, I already know. I'm not trying to come off like I know the answer to any of these concerns, just trying to stir the mental pot.

 

Yup, that is EXACTELY what I was saying. Just wanted to make sure that we're on the same page and everyone else knew it as well. They way it was being worded, it seemed like it could be confusing.

I would've started with a some timing, not much, but more than 0... oddly enough though, our ign maps are very similar. You're running much more advance than I am in vac though which is good for power and cleanliness and throttle response. I just seem to spend much more time tuning the higher load sites as I am very happy with how the car drives, I always seem to be improving other area's now.

Oh really? So 1900* worth of exhaust heat and combusting gases won't ignite an intake charge? I disagree.

hmmmm, maybe that's why they idle @ 2k and pull very little vac?

Aren't you contradicting yourself here?

And this is what I've been saying.........

 

EMAP and exhaust gas dilution are related, so its a good point.

EMAP is actually pretty undervalued, i used it to tune my NA, and it made it very easy.
less back pressure = happier engine = more power.

 

Alright, then tell me, what is the auto-ignition temperature of fuel? What are your idle EGTs? Im going to go out on a limb here and say that the latter is much greater. If the intake charge was going to instantaneously ignite the intake charge, wouldnt you think it would be at idle when it physically has that much more time during overlap?

The point I was trying to make is that the dirty intake charge does have a greater risk for auto-ignition, but not because of the temperature. This is what I was referring to:
He is a lot better at explaining things then me.

Oh come on, I know youve got more game then that...
http://www.youtube.com/watch?v=3RlCJ...layer_embedded

He claims it idles very smoothly at 1000 RPM, pretty similar to my streetported engine.

The simple point I was making is that exhaust gas does not instantly ignite the intake charge, even if you are running slightly retarded timing. Period. It just increases the volatility of the intake mixture, which is likely part of the reason why a mis-fire can lead to much higher combustion pressures on the following cycles.

 

Ok I'm learning a lot of stuff here. What the hell is EMAP and do I have this with my Haltech E11?

 

I need to go pull it up again but in one of the RE books it is stated that a misfire on one rotor face will carry over to the next 2 cycles. So if the intake has now has dilution from the last exhaust cycle and is carried over causing a misfire it continues the cycle over and over.

I am w/ titanium on this one. I feel the timing can be more aggressive and the fuel can be as well.

 

that is completely incorrect. even with a carb and a distributor ive had mine idling as low as 750rpm. normal idle is 900-1000 depending on engine temp.

with intake vacuum given all the overlap, less is better... think about it, intake vacuum just pulls exhaust out of the exhaust port and into the next intake stroke. ive tested it, less vacuum runs better until the carb doesn't meter fuel anymore. i can even get it to idle without the brap brap misfires.

most of what you've heard about PP engines, is from road racers 30 years ago who didn't care if it idled, and doesn't really apply

sorry for the hijack, but i just built and tuned one.

 

Somewhere around 500*. but as the charge comes in and compresses, what's the auto-ignition temp of that? My idle EGT's are about 1100*. I also have 100kPa or less of EMAP, so I have very little dilution at idle.


Again, I can't speak intelligently about an engine that I've never built or tuned, so yeah, I can only speak second hand about P-Ports..... that's an impressive idle BUT let me ask you this, what's the thing pulling for vac? This comes in handy in the next post

My SP pulls about 45kPa

EMAP - Exhaust Manifold Absolute Pressure. You should have a spare input or two that you could hook up a 3B MAP sensor. The trick is to run 2' of Stainless Steel tubing to cool the exhuast off, then some braided hose to the MAP sensor.

 

That is very impressive actually. And it's not really a threadjack, there's still some good info in here for those who can interpret it and learn from it.

 

i did a LOT of research, and some experimenting. i'm not sure how applicable it is to a side port, but reducing the intake vacuum on the PP engine makes a HUGE difference in low speed running

 

Does anybody have any concerns or insight on the coinciding of the trending data loss at the exact moment the engine blew?

 

If all data was lost (not just a bad tach signal or something), then the most logical explanations are

1) loss of communication between laptop and ECU

2) some kind of failure in the ECU itself

 

I like the methanol coolaid.... bandaid or not.

I like Howard's posts about it.

I like that he's not an arrogant mr. know-it-all.

 

After rereading the thread and not getting caught up in everything else going on I would start here and figure out this problem as I think it will lead you somewhere. Sometimes its the little things we miss trying to make the problem too complicated.

The only other thing I don't understand is why everyone runs 9's all around. You know the trailing spark plug hole is smaller and holds more heat, and that is the reason the factory runs 9's instead of 7's. I am not running near the boost you are but at 16 psi on the street I run 9's L and 10.5's T on 91.

Those are my only contributions because after the reread that's all that stands out in my head.

Good luck to the OP and keep us updated on your findings. You'll be the one to tell us what happened.

 

Very wise and I agree with you. I think that's what folks oughta do -- exactly that when running at a bar. I've not liked the idea of keeping the stock trailing plug when doing the kinds of power ranges most of us street cars use. Has bothered me for a long time.

I agree. I think it's too hot a plug myself. The symptom he experienced and felt fits it.

B

 

I agree. If I thought the boost was going to go any higher than the 22 psi I expected, I would have waited for the new plugs to arrive (came in last night). I think I'm going to run 10.5s on the leading and 11.5 on the trailing.

E-mailed back and forth with Haltech the past couple of evenings. They seem to think the data loss is due to electrical noise. They said non-resistor plugs or solid core wires would be the most likely culprit, but I was obviously running resistor type plugs and MSD Superconductor wires (no solid core). They also mentioned poor grounding, but the block and chassis are grounded to the battery via 8 gauge and 4 gauge wire respectively. Block is also grounded to the chassis. Don't think that is the problem. I'm wondering if one of the leading coils (ls1 style) took a crap, and caused a significant amount of noise when it died. Might explain the engine sounding like it hit a rev limiter? I've also heard an engine with severe ignition breakup sound like that too. Need to do a compression check to verify the state of things, but I'm not going to be hopeful. I had the coil charge times set to 6ms on the dyno. Before this run, however, I dropped it to 5ms after reading that a charge time > 5ms would lead to a quick death of the coil.

BDC - please expound on the "symptoms" you are referring to. I'm a little slow sometimes........

 

That's better.

I agree.

Maybe noise but I doubt it. I could be wrong, though. It's always somethin' with cars.

Those LSx coils can be run comfortably to 6ms.

It's like the hand of God smacks the car. The whole drivetrain takes this one, singular huge blast of BAM. When driving, everyone will feel it. And, as the plugs get hotter (under load), that same intermittent blast starts coming in greater frequency. Its like a huge fuel cut of some sort. I've seen it on a few cars and all three of them had catastrophic engine failures (massively chunked apex seals and gouges all over the rotor housings).

B

 

What LS1 style coils? I am running the Motec ones w/ my E8.

 

Ok thanks. I'm running NA so I guess the best place to mount the tunbing would be the collector? I have a colletor w/megaphone.