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Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Wed Dec 02, 2015 11:27 am
by vlad01
OZ38 wrote:Charlescrown wrote: Comparing alcohol fuel to petrol might not be a good thing. Some tuners have made the mistake of tuning up to detonation and with alcohol you will hammer the guts out of the bearings due to the rod/crank angle obtained without detonation.
I think you have high lighted to me a fault I was seeing when helping a friend out pit crewing his Methanol Mechanical fuel injected Camaro drag car.
I noticed the way they would set their spark timing was lock in at something like 34-38 degrees BTDC on the crank trigger device. Then they would set the fuel injection pill (return line jet) based on the EGT they got at the end of a run, fatter (rich) or thinner (lean) they would refer to it as. After seeing the engine fail one time with a ARP big end bolt letting go shortly after a rebuild by recognised race engine builder. I started to wonder if the point of peak pressure was happening a little to close to TDC. Tuning of these engines didn't seem to have the benefits of engine management that could control knock. Or so it seemed by the way these guys were playing with them & winding then locking spark advance so far forward at the high idle.
Thing is alcohol is great at resisting knock, but sure is susceptible to pre ignition.
Not to confuse with eachother. Knock is pockets of charge spontaneously combusting usually in a fast explosive burn due to enough heat energy in the charge to make it react spontaniously Heat = Heat, pressure = heat. Pre ignition is the whole charge lighting off just like spark plug would but set off way before actual spark and normally set of by hot spots like glowing electrode or carbon, its quite an explosive burn too. This is what happens when an engine runs on when no ignition is present. Eg Lada engines lol
Knock is damaging, pre igntion is usually catastrophic breaking rods, cranks and pistons.
I have read that alcohol fuel, its a good idea to run couple of numbers cooler plugs to prevent pre ignition on alcohol.
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Wed Dec 02, 2015 11:33 am
by Holden202T
I've never experienced pre ignition with methanol and normal heat range plugs but I do also run 1 plug cooler ngk's, and could possibly even go 2 numbers cooler, just harder to get. the theory is also for increased HP you want possibly a number cooler plug too ....
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Wed Dec 02, 2015 11:46 am
by Charlescrown
unfortunately my dyno experience with alcohol fuel is vert limited but you newer techs should be really looking into new fuels. I got some info from BP some time back and it was interesting on power/litre and air fuel ratios for different octane levels. I still remember the old Holden 253 and you could clearly see a power drop as the timing went up with no knock. I suppose we are a lot like monkey see monkey do and when monkey does his own thing and blows up and engine he goes back to monkey do. It would really be exciting to get an engine setup with some accurate modern technology and start developing new tuning maps but where do we stop? Cost and time I suppose but it is probably already happening. The V8 super cars seem well developed on E85.
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Wed Dec 02, 2015 12:03 pm
by Gareth
Both these tools together would be the best thing. So big G, when are you getting the in cylinder pressure monitoring gear? lol
you read my mind
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Wed Dec 02, 2015 12:51 pm
by vlad01
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Wed Dec 02, 2015 6:36 pm
by yoda69
The logging speeds for peak pressure are amazingly fast, I have a logger that can do 10,000Hz logging speed which I thought would have been fine, from my reading even this isn't high enough for good results!!!
Here's the quick calculation:
Realistically would need to be logging at a speed better than 1 degree of engine revolution to have reasonable view of cylinder pressure, at 6000RPM this is 100 revs per second or 100hz, times this by 360 degrees per rev and we need a logging speed of 36,000Hz. Having had a read through of some of the cylinder pressure transducers there are recommended recording speeds of 60,000Hz minimum for the reason. Datalogger with these speeds don't come cheap.
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Wed Dec 02, 2015 8:04 pm
by OZ38
yoda69 wrote: Datalogger with these speeds don't come cheap.
So back to dyno tuning by torque figures ?
I heard dyno tuners say tune for torque quite often.
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Wed Dec 02, 2015 8:26 pm
by Gareth
Yep, its called MBT or 'mean best torque', this is usually reached a few degrees before knock occurs, MBT is the point where an engine/fuel combination for a particular speed makes the most of the combustion process, or in other words 'where the engine is the most efficent'
On the dyno we add ignition advance until we start to see a reduction in torque (whilst listening for knock) the point of the highest torque output is the engine/fuels sweet spot.
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Thu Dec 03, 2015 12:40 pm
by OZ38
Biggvl wrote:Yep, its called MBT or 'mean best torque', this is usually reached a few degrees before knock occurs, MBT is the point where an engine/fuel combination for a particular speed makes the most of the combustion process, or in other words 'where the engine is the most efficent'
On the dyno we add ignition advance until we start to see a reduction in torque (whilst listening for knock) the point of the highest torque output is the engine/fuels sweet spot.
This is great, I am really learning a bit out of all of this talk.
We 've been talking about spark advance / retard & the results it will have on higher compressions & lower compressions with high & low octane fuels.
I am wondering now how the advancing & retarding of the camshaft will affect all of this too. It now seems normal for guys to dial in (degree) their performance camshafts to the specs on the cam sheet. With the Super6 it is also seeing guys advance the cam by a couple of degrees from the standard settings. The theory being to get you max power lower / earlier in the rev range (Advanced) or later / higher in the rev range (Retarded).
Cheers
Re: Ulimate 98 in a n/a ecotec V6 ?
Posted: Thu Dec 03, 2015 12:46 pm
by pman92
I imagine retarding the intake cam would lower the dynamic compression ratio and reduce knock/allow more timing before knock, while advancing the intake would increase the DCR and increase the on set of knock. Can anyone confirm?
I'm learning a lot reading this thread too, it's interesting stuff.