rotorocks

No, those are my personal invention at cutting corners :-)
...Home Depot.

As you can see there is plenty of BANG for a Buck

TeamRX8

iTrader: (25)

exactly, the fuel system could have a blockage or failure and a resulting AFR way above stoich which would produce a low EGT, without a functioning AFR indicator it might not otherwise be obvious, the engine would likely detonate and knock out the apex seals without being pushed hard, just an unproven theory at this point though

MazdaManiac

iTrader: (3)

Just because you are over-lean does not mean ping and blown seals.
Detonation is NOT necessarily autoignition.

If the motor is running over lean, there might simply not be enough combustion pressure to do much of anything.

guitarjunkie28

lean or too much boost = preignition
too much timing = detonation

guitarjunkie28

you talking about C or F? it seems a little too low for F, but too high for C

Red_X8

I don't understand when some people complain about the price of adding FI to their car. You have to pay to play, cutting corners gets you nothing but problems in the long run. If you can't afford to turbo your car, then you shouldn't do it.

rkostolni

Your AFR might have been rich when the car was tuned, but your AFR will lean out as the IAT drops. I'm adding 9% more fuel at 45deg F compared to 75 deg F to maintain the same AFR. Like I had said before, if your tuner didn't add in fuel to your air temp map, then it definitely leaned out. Not saying that's why it blew, but as air gets colder, it's density does increase.

EGT is no way to measure your AFR. It doesn't respond fast enough to show spikes, and its just not precise enough. A 0.5 change in AFR can be all it takes to blow a motor if you're already on the edge, which after the climate change, you may have been.

MazdaManiac

iTrader: (3)

That is incorrect.

Detonation - any uncontrolled combustion, regardless of its timing relative to a proper ignition event.
Preignition - uncontrolled combustion in advance of the proper ignition event initiated by elevated temps in the combustion chamber (the result of hot-spots, low octane, high pressure, or high intake temps).
"Ping" is preigition that results in higher than normal combustion pressures. However, it is possible to have preigition that yeilds lower than normal combustion pressures that won't manifest itself noisily. It all depends on how much energy is available.

RX8FOREAL

rkostolni - You make a good point - one that is more obvious to people living where there are very distinct seasons. I live in NJ and just within this week did the temp drop from mid-sixties to 27 tonight. That cold dense air makes a hugh difference on how the car responds with turbo engaged. What will take me a while to learn is the major interdependancies between many of the fuel and ignition adjustments.
I also made some fuel adjustments in the air temp map which led me to make corresponding changes to the idle and load maps.
It appears that there may be a separate map for each season, which the inter has the capability to do.
Thanks to Mad Dog for his tuning suggestions. I feel much better knowing I have very conservative ignition settings, I don't want to be one of the first with a 3rd engine.

Dennis

guitarjunkie28

that was dumbed down. i thought you'd know that.

MazdaManiac

iTrader: (3)

Dumbed down can be dangerous when you are defining terms.
The whole "detonation" issue often tends to be misapplied.
The most important thing to realize is that lean doesn't always mean ping and vice-versa.

guitarjunkie28

you should be able to just adjust your correction maps and never have to mess with the "base" fuel map.

i've been adjusting for the colder air and warm up in my air and coolant correction maps in my haltech/fd, but i haven't touched my main fuel map since it got cold. this should be true for all systems.

the problem is, hardly anybody has the capability of feeding the engine controlled air temp on the dyno. it'd be great if we all had access to climate control like that, but the reality is it's really expensive and most of us don't have that luxury.

pay close attenetion to your air temps when you tune. write them down. later on, when you notice something lean or rich, you'll be able to look back at the condition in which the car was tuned and just play with the correction maps.

a little extra work when you tune can save a lot of time later.

guitarjunkie28

yea i get ya.
my point, and obviously this is very general, is:
advance your timing too far on an otherwise good tune, and you'll detonate. run too much boost or fuel with lower octane and you'll auto-ignite.
the 2 big problems with rx8's are:

1) excessive carbon buildup on the rotors
2) compression ratio is really high to begin with.

so in your description of the preignition event, lean, hot spots, too much pressure, too low octane fuel, etc... are all indicators of preignition. basically, too much boost or too lean for the conditions.

i think the auto-ignition is going to kill more boosted renesis engines than anything else.

a good example of the opposite is my fd engine. i used 8.5 compression rotors when i built it, and i boost 20 psi with a little methanol injection on california 91 octane daily and it holds together just fine. my egt's are quite a bit lower than the boosted renesis egines, too.

MazdaManiac

iTrader: (3)

Yeah, but the important thing is that pre-ignition may not yield high combustion pressures if the mix is very lean. Therefore, it might not ping, but it is still detonating.
The root of the word "detonation" is the concept of de-tune, not explode.
If the process is detonated, it is detuned, not necessarily over-combusted.

Fanman

I live in Los Angeles never been a 30 degree weather change in years. Also, I never really drove the car in cold weather. It was during the day (similar to conditions when it was tuned, and early evenings. Never ever in 45 degree weather so that is a moot point for us Californians.

Not only that but again, the place I took it to, and the people that worked on my car are some of the foremost tuners in the country. They have probably built as many 1000+ hp Supras, and 500+ hp RX7's, and worked on more import cars than just about any outfit in the country. So tuning the AFR's for temps I'm sure is something that they did. The engine went. No matter how much tuning you do, rotaries do that (especially ones with high compression and a largely untested turbo kit for high mileage). Does that mean that I am 100% sure of what caused it, nope. Like I was telling another poster on this board that has had numerous rotaries cars. The only thing you know 100% about blown rotary engines, is that you are 100% unsure of what causes it to blow. If you want me to give a definitive answer on exactly what caused my engine to fail I can't.

If you want to keep on making wild assumptions by all means go ahead.

Fanman

This is an odd post in the end of this thread. And can be construed pretty poorly if directed at me. Did you actually read the thread and see what was done in preparation for FI'ing the car and how the car was worked on for FI'ing ? Before you say that I was "cutting corners."

rotorocks

I think it was actually directed at me :-) As I had mentioned "cutting corners" when replying to your question about the blown coupler in my avatar. Apparently he is not too familiar with my "oneofakind" turbo project.
I'll explain:
Red_X8 I did my turbo system out of my own garage, since it was an undertaking that no one has successfully attempted on the RX8 (at the time) I was trying spent as little money as possible on parts (in case it did not work).
Now that it works, I have really good couplers on it :-)
Fanman, sorry for hijacking the tread. Just wanted to make things clear.

mike1324a

Fanman, all you have to say to that it "k thanks bye"

guitarjunkie28

we've found a lot of ways to explain boom.