Hymee

iTrader: (1)

Hey,

For the Aussie guys - I found "Diggers" sell straight Toluene for about $20 AUD for a 4 litre can. It is not a stock item in retail stores.

Cheers,
Hymee

(PS - for any spies out there - I didn't say I bought any...)

OverLOAD

Hey, back to the advance/retard timing thing, and the pre-detonation question..

Here's a how to, for how the RX-8, and many other cars handle 'potential' detonation.

When the knock sensor starts to detect that the mixture is detonating before the spark, it decreases the Air:Fuel ratio... it makes the mix more rich, causing lower temperatures in the combustion chamber, reducing the possiblity of detonation.

Normally, you won't instantly get detonantion 15 degrees before TDC first... It'll start to happen just a little bit before the spark first, and continue to advance the timing as you step on the gas. If your fuel is too low a ratio, the mix gets much hotter at TDC, possibly causing detonation.

Obviously, detonation 1/100th of a degree before where the computer thinks it should be firing isn't that big of a deal, but the fact that the computer can start to detect it within 1/10th of a degree helps to minimize it. We would all do best to be able to run the highest compression ratio possible, with the highest A/F ratio possible, but the engine might detonate way too early.

Here's how A/F ratio works in the engine: a normal A/F ratio of around 14:1 is pretty normal depending on the compression ratio of the engine involved. add more fuel, until you've got a 10:1 A/F ratio, and it causes the engine to have a lower temperature burn.. the reason this is, is because all of the fuel does not burn, since there are more hydrocarbons that do not react, they can not heat up, and actually absorb heat from the other hydrocarbons in the mixture that did burn, since the amount of oxygen in the mix is limited, so is the amount of burnable hydrocarbons.. This reduces the compression temperature, and lowers the likelyhood of detonation.

If you lower the fuel amount in the A/F ratio, to say 18:1, then you have a situation where there is enough oxygen in the mix for a complete burn in the combustion chamber, and maximum heat and efficiency.. This is very bad for HC byproducts, since the hotter the burn, the more volatile HC byproducts like Carbon Monoxide and such are produced.. bad for emmissions. Also, this increases the compression temperature, and increases the likelihood of detonation.. This is part of the best argument for an intercooler in a turbo application, since they dramatically reduce the temperature of intake charge air, reducing the maximum temperature of the Air-fuel mix at TDC.

This follows on to how compression ratios work the same way. Higher compression ratios cause higher temperatures at TDC, lower compression ratios reduce the TDC temperature.. That's why Turbo engines like having lower compression ratios. It's the Octane content that helps to prevent detonation at the high temperature conditions that occur under high-compression, especially with the added pressure that a turbo/supercharger will add. If you could get gas with high enough octane ratio, you could run a compression ratio of 15:1, at 30psi boot, and stil advance the timing... It's all about the susceptability of the gas to detonate at that point. the higher the octane number, the higher the temperature the air/fuel mix can go before it detonates...

I had considered trying putting a small piece of plastic, or some sort of cover over part of the edge of the mass airflow meter wire. This would make the computer think that there was less airflow than there actually was, thus leaning out the mixure in the chamber substantially.. exactly how much of the sensor wire to cover would be very tricky, and quite likely could cause way early detonation, and blow the rotors off the driveshaft... but it could also lean out the mixture enough to make the PCM deliver a slightly less rich mixture throughout the whole rpm range, causing increased power, and better mpg.... but worse emmissions.. probably also do bad things to the oxygen sensor and the exhaust - fresh air pump...


OverLOAD

Hymee

iTrader: (1)

Overload,

Thanks for the great info. One of the best aspects of this forum.

Regarding mods to the MAF - it is quite common in AUS for tuners to port out the MAFs in our Chev 5.7L LS1 powered cars. Porting the MAF tricks the ECU into leaning out the mixture. The exact amount of porting is experimental. The better way is not to fiddle with the MAF, but to re-calibrate the ECU's fuel mapping tables. If the size of the MAF is offering a physical restriction, then a bigger MAF would be put in - you just need to get the correct calibration for the MAF so you can still tune the ECU accuratley.

Another common thing is to remove the MAF altogether, and do a completely MAF-less tune. But it not as accurate a tune as with a MAF. It is completely based on throttle postion. MAF is much more accurate.

Slightly off topic but still good info (hopefully!)

Cheers,
Hymee.

Doctorr

Mr. labrat,
Excellent points about Ethanol....it is mostly a 'subsidies' matter, very little thought is given to the poor old engine.

That said however, given that ethanol has much less density/power, and is also a good oxygenator - and given that a certain 'motor-of-the-year' runs, and I quote..."pig rich", then perhaps Xylene for power and octane is just making a bad situation worse....

The alcohol discussion did jog a file in the old memory banks......about an old RX3 with a '12A' that got its gas lines frozen solid (don't go there!) and ended up with a gallon of alcohol in its tank - the results were.......eye opening......

So we can try going the 'less filling' route....ethanol's octane rating being 112, and liberating significant oxygen in the combustion, with the double O2 sensor setup looking for the oxygen level in the pre/post catalyst outlet stream - and the net effect on the mixture being to 'lean it out', should make for an interesting dyno plot.

I would not advise anyone to try gas/ethanol mixtures beyond the ten percent tolerance for 'normal' gasohol......it has to be anhydrous fuel-grade, with co-solvent......and is a definite warranty issue. Best leave it to the pros.

I am booking some dyno time this week to establish some baselines, both for a car (not mine, of course!) and naturally, for the dyno machine.

"Film at 11!"
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doc

Vette Dude

I would not use xyline.. I would go with toluane... I think that is how u spell it... It was used exclusively with formula one car racing back in the 80s when they used lots of high boost turbo motors. It has a nutz *** octane rating! i don't think xylene is such a good idea IMHO.

r0tor

iTrader: (1)

I've done a few lab dyno tests for the effects of running ethanol mixed with gas up to 10% - basically the engine ran hotter, produced no more hp, but did produce some nasty fumes. It turns out there is a balancing act between getting more power from the fuel and getting less efficiency because of heat.


Just a warning about Xylene and Tolulene - change your oil more frequently if you run this stuff. They are both about as perfect a petroleum solvent as it gets - cuts oil like crazy and leaves next to no residue (its actually used to wash out test equipment in oil labs). Yes gas is also a good solvent and gas does have some of these products in them, but Xylene and Tolulene are much more severe - better be safe then sorry, especially with the amount of fuel that gets in our oil!

Vette Dude

I knew when i was forgeting something... In fact you could add some oiil to the gas...Toluane is used in modern gas extensively. It being one of the major aromatics.

Kas

I'm no mathamatitian (or however its spelt) nor a genius like some, but i've had some great reading here and alot of work has gone into this post....but still cant figure out the outcome of it all ?

more power safely? or not?

VelocityRedRX8

Actually, nitromethane's formula is CH3NO2 - NH4+ is the ammonium ion of ammonia, NH3.

wakeech

ah... :D thanks for that... i'm a chem dummy, just a guess, and was only to illustrate that they're not the same chemical.

Kas, yes, toluene or xylene is a safe way to increase the power of the engine... just DEFINITELY not the cheapest way.

VelocityRedRX8

I meant no offense, wakeech. Chemistry/physics geek here.

wakeech

none taken

Lock & Load

I have purchased a bottle of high performance octane booster. I was wondereing whether this can be used on rotarys. Iv'e emailed them hoping to get an answer back but do you guys know if it is possible? I am currently using Shell OptiMax 98 ron this product depending how much you put in will increase the ron by up to 6 ron.

Here is the address to the site.

http://www.nitrous.com.au

Do you guys recommend products such as these?

XDEEDUBBX

sure why not...your fuel will combust faster...i use octane booster on my 43cc 2 stroke engine for my scooter...felt a big difference but the octane to regular fuel mix was much greater..

Kas

wats the point if the cars not tuned to run higher octane fuel.

Lock & Load

Kas

Fuel used in japan is 100 octane level so the rx8 is made to run on higher fuel not the supposed 98 ron we get here , i have been told that some cars dont make it to oz because of our low quality fuels.

Turborex

I highly doubt the rx-8's in japan are tuned the same as the rx-8's here in the US. Here we have higher crash standards, and emissions standards, as well as lower octane gas. Octane booster will help the performance of the car, whether it is tuned for it or not. It will help more if you can tune for the octane booster because you may be able to advance timing a slight bit, and lean out the A/F.

XeRo

Turborex is correct in that aspect...of tuning...US is much stricker on emission standards...also go figure...why do you think they pay ~$3.98 a gallon for fuel over there (in J-Pan)? Our fuel standards here ..regardless of what Shell, Amoco, Chevron claim SUX compared to other countries...i mean even Iraq has better fuel...or had

BUT....in light of Kas' response...there is no point...until all this BS talk of turbo and intake becomes reality and force higher end fuel management..

Lock & Load

THANKS FOR YOUR INPUT.

Turborex

I agree good point.

tadams

Does adding a fuel cleaner (like STP) every gas up or every other time effect the 8 negatively?

Please lmk your opinions/experiences.

Thanks

wakeech

ok Ray, let 'er rip

rexateher

Is the horse dead yet? no!! whack whack. How about now?

Gord96BRG

No, it's the exact opposite - octane is just a measure of fuel's resistance to detonation. It has nothing to do with the energy content of the fuel, but the resistance to detonation also means that higher octane fuels actually burn slightly more slowly. If you're talking toluene or some other non-gasoline additive/substitute, then energy content is also different.

Regards,
Gordon

Turborex

you want to combust faster?
NAAAAAWWWWWSSSSSS