Which part of me saying not to take it personally or having any personal issues didn't you see? I'm writing for information sake not personal reasons.

Sorry if anyone was offended.

 

I think this is the beginning of a pretty good thread on the topic of detonation.

If people would be less "touchy" and not take stuff personally it would make for a much better discussion.

Trolls will troll.
Ignore them, please.

To reply to their comments feeds them.

 

I knew I'd regret it.

Probably picked a bad thread to introduce myself on....

<white flag>

 

WPM Rotary God???

 

the simple answer to the original question is this: the maf/afm reads 0-5v (or 5-0v), once it hits maximum (or minimum) voltage it cant compensate anymore. you can go a little further, but you loose the ecu's ability to compensate for airflow changes.

mike

 

I may be wrong but i think all Rotarygod was saying about octane was that it will take ALOT more than 87 octane instead of 91 to cause detonation in the Rennisis. This is simply too small of a change in the N/a motor to cause such a drastic reaction. Now add some more power (forced induction) with higher temps and pressures along with the 87 octane and there may be serious issues...I'll bet no one would disagree with that.

 

I disagree! You lost the bet, pay up...

j/k

 

Tony: Just for the record I don't have any issues with you or anyone else here. I apologize if I came off in an offensive way. Just smack me next time! Welcome to the forum BTW. I hope you don't have an issues with anyone else here either. We are all pretty cool here although admittedly I guess I can be a *****. It isn't intentional though.

Canzoomer: I agree. Again sorry if I came off offensive to anyone. I didn't intend it thatway.

 

Well, RG, I for one appreciate your prickishness and find it refreshing.:D
Mostly because you know what you are talking about.:p
The Internet is a funny place.
If Al Gore had the ability to convey intent and emotion, it might have been integrated into the WEB somehow.
But, alas...

 

Now that we have all kissed and made up, here is some info:

The Renesis in the RX-8 will start to significantly detonate at around 14.3 AFR, under open loop, WOT conditions.
Typically it starts to go after the secondary intake tract opens ( above 3,750rpm) The knock sensor picks it up, and the ECU repsonds by dropping timing advance 15 degrees, and by cutting fuel duty cycle.

Engine power then drops about 70HP, and the car is effectively in limp mode for a while, until the ECU resets the map.

If it detects a second event it goes onto limp mose until it is reset, either by OBD port reset instruction, or by unplugging power to the ECU for a few minutes.

The system is amazingly resistant to knock.

If anyone would like AFR tables demonstrating this, with matching dyno charts I can post them if you find it of interest.

 

Why would you want to operate the motor at WOT and 3700 RPM with only a 14.3:1 A/F? Towing a Fruehof trailer over the Alps in August with a dirty airfilter and no working gear under 5th??

Just **** in the tank while you are at it and be sure to drain the cooling system first.:p

I actually found (as I'm sure you did as well) that it is of some benefit to keep the 4000 RPM and below range just a touch more rich than the stock setting - especially at 70% - 100% throttle.
I've taken the ignition timing all the way up to 15° additional advance across the board with an A/F never more lean under load than 13.7:1 with no ping and no anomalies in the logs to indicate ping or anything similar. This is on 92 octane, BTW.
I run out of advance at 20°, of course. I guess I 'll see what happens.

The interetsting thing I've noticed (and expected, actually since this is the case with turbo motors) that the EGT at torque peak is slightly lower with more advance than stock.
Can I can gain back some of my CAT longevity with timing advance? Probably not, but it can't hurt I suppose.

 

 

We had an opportunity to test with a good knock controller unit, and therefore pushed the A/F to determine where near and WOT knock actually DOES start, with a margin of safety.

We also looked at the effect of timing on it.
And, yes, smoother running, less power dip can be achieved in the 4K+ range with more fuel than stock, as Mazda made that range pretty darned lean. Question is why?
Advance in this range seems to have a good effect in tuning out that "dip"

However, raising fuel in that area increases consumption in higher highway speed applications. Sometimes by quite a bit!

In this we are trying to accurately define what the tune limits are in terms of mixture and timing. So far we are seeing the resistance to knock t be quite a bit higher than expected, especially for this high a compression ratio.
Also the stock sensor and ECU management on knock is pretty effective. Colder plugs ( L10) also allows a LOT of advance to be used, as high as 30 degrees, with a significant power gain. I see advance gains of useful amount up to about 8 degreees, where it flattens out, then rising again at around 14 degrees and up.
Of course these plugs are horrible to use in cold air conditions, contributing greatly to flooding. Good for track use, but pretty useless on daily driving in cold weather.

 

Canzoomer.....

Please do post the AFR tables and dyno sheets. I am a visual learner and this would keep me.

I owe you, rotarygod, and Maniac a HUGE amount at this point. I've only had mine since Oct. but with all the info you guys are sharing I feel I am almost ready to start and play with the tuning on my own!!!!

Again.....Thanks to evreyone on this fourm for all the info and entertainment they provide.

Nathan

 

is this 30btdc? or 30 over stock factory maps?

 

damn, i want this thread in the Tech Garage.

hey RG, PP13BNOS, did you guys see Ryan's reply??

so... i suppose we have to take that for what it's worth, although i'm not sure in what position Mr. Munsey would be in to know about such technical fineries.

 

Trailing plugs fire before the leading - it is a certainty. I have observed it myself and the technical papers from SAE indicate this as well.