Dr.drivability
9 second wannabee
- Joined
- Oct 1, 2005
I understand what you are saying, but It was two VERY reputable vendors.
Cracked piston on high mileage stock bottom end
- Thread starter bison
- Start date
With the methanol being involved, it is very possible for the methanol to go into preignition and cause damage like that with no other signs, such as melting, signs of lean out, etc.
At least that would be the case with a pure methanol engine. The point where the methanol goes into preignition is like a light switch and there's little time for components to melt down. Things start to break before that point. I've broke rods from methanol preignition and the head gaskets and deck surfaces looked perfect and flat.
In the case of gasoline with methanol injection, you're running higher cylinder temps than a typical alcohol engine. I wonder how close the alcohol gets to autoignition temperature in that scenario? I've read that high amounts of aux methanol injection can lead to preignition of the alcohol.
Are you injecting a lot of methanol? Was the engine running hotter than usual?
edit: I just read past the 1st page of the thread. You are injecting a lot of methanol.
You guys may be discovering auxiliary methanol injection preignition. The second engine I put rods through, the alcohol preignited with absolutely no warning. At one moment the rpm and boost is rising, and the next, a bunch of noise as the rods are hammering there way out of the block. The heads, piston tops, gaskets, deck surfaces, spark plugs all looked perfect. Bearings too.
At least that would be the case with a pure methanol engine. The point where the methanol goes into preignition is like a light switch and there's little time for components to melt down. Things start to break before that point. I've broke rods from methanol preignition and the head gaskets and deck surfaces looked perfect and flat.
In the case of gasoline with methanol injection, you're running higher cylinder temps than a typical alcohol engine. I wonder how close the alcohol gets to autoignition temperature in that scenario? I've read that high amounts of aux methanol injection can lead to preignition of the alcohol.
Are you injecting a lot of methanol? Was the engine running hotter than usual?
edit: I just read past the 1st page of the thread. You are injecting a lot of methanol.
You guys may be discovering auxiliary methanol injection preignition. The second engine I put rods through, the alcohol preignited with absolutely no warning. At one moment the rpm and boost is rising, and the next, a bunch of noise as the rods are hammering there way out of the block. The heads, piston tops, gaskets, deck surfaces, spark plugs all looked perfect. Bearings too.
Methanol will auto-ignite between 725-878 deg. F. Don't know how pressure can change that figure.
I would imagine that with the right combination of circumstances if the gasoline went into even the slightest degree of detonation, and there was methanol in the mix that had completely dissociated by that point (600-700 deg. F), there would be a high chance that the cylinder temps would get high enough very quickly to put the methanol mix into preignition with very little warning. Remember, methanol does not detonate like gasoline. It passes that step and goes straight to preignition.
I would imagine that with the right combination of circumstances if the gasoline went into even the slightest degree of detonation, and there was methanol in the mix that had completely dissociated by that point (600-700 deg. F), there would be a high chance that the cylinder temps would get high enough very quickly to put the methanol mix into preignition with very little warning. Remember, methanol does not detonate like gasoline. It passes that step and goes straight to preignition.
I would imagine that it has to be a little tricky tuning a gasoline/alky mix. I would hope that those that are doing it are not tuning for the highest possible hp level. When alcohol is tuned to a safe hp level, it is under what it could be if it were leaned just a little bit more. With a safe alcohol mix, you will lose a little hp. You need it a little on the rich side to stay away from preigniting. In my experience, 10.6-10.8 is living on the edge at 26-27 psi boost. I see a noticeable power loss at 10.4 and lower,... which would be much safer.
I am curious to know have you noticed any differences in the data you get since removing the powerplate? You say you dont think it wasn't hurting or helping. Are you using a stock doghouse? Are you using a stock shortblock besides the cam? I don't have any intention in removing my PP, just wanted to see what made you want to try it? Good luck on the 9sec pass!
the only data i have is time slips where the car at the same boost level runs the same mph with or without the powerplate.i really don't want to get into a lot about the powerplate but i see it as a restriction at the level i am at right now.that's my opinion though. i have a Precision plenum to help clear the 4" intake pipe..the block has never been out of the car..it is completely stock.
DonWG ..that is very interesting about the alcohol..i am spraying a good bit but i don't think i am spraying that much
i have been wot a couple of times since i have my fuel straighted out and i have no knock. the car pulls like crazy up top.....Bobthe only data i have is time slips where the car at the same boost level runs the same mph with or without the powerplate.i really don't want to get into a lot about the powerplate but i see it as a restriction at the level i am at right now.that's my opinion though. i have a Precision plenum to help clear the 4" intake pipe..the block has never been out of the car..it is completely stock.
DonWG ..that is very interesting about the alcohol..i am spraying a good bit but i don't think i am spraying that much
I'm just suggesting that you guys start looking for failure patterns. There are a lot of you guys now that are spraying methanol. Some of you a lot of it. Judging by what I've read in this thread, a pattern seems to be emerging. As you guys keep working up on the tuneup, you will ultimately find the limit of what the alcohol can do for you when mixed with gasoline.
edit: Yeah. Alcohol does pull real hard,... just before it hands you a rod. :biggrin:
Exactly! I sure would like to see people learn to tune without a knock sensor. Maybe that's not practical with a petrol engine though.
Since methanol really doesn't detonate, I've always tuned without a knock sensor. If I depended heavily on a knock sensor and it did pick up something, it would already be too late.
i think Bison was running c-16 and alcohol...i'm sure he wasn't getting any knock. mine could very well be getting knock with the 93..lets see how many passes it will make before it gives me a rod
Someone willing to lay his engine on the line for the sake of science. A man after my own heart. Just don't forget to keep us updated.
C-16 does much to help with the detonation limit of the gasoline. It does nothing to control the auto-ignition limit of the alcohol.
:biggrin: i am very hard headed and not scared to go against the grain from time to time..DonWG you are far learner than me. these cars have really taught me a lot and i am still learning...thanks Bob
I Like that idea, even though it does sounds DANGEROUS..lol.
but how do you tune without a knock sensor????
spark plug checking after every run or something else.....what?
anyhelp appreciated..
Well, in my case, my learning experience was expensive. You carefully track a/f ratios, timing, boost, a lot of simulator work, and blow up a few engines to test your fueling limit theories. After all that, you have a pretty good idea of where your limits are. The latest engine has lasted well.
Plug reading is very important, but most of you probably don't install fresh plugs to get good readings like you should. Trying to read old plugs is useless,... unless you're just looking for melted electrodes.
edit: For instance, I've learned that if I burn the plating off of one thread on the spark plug, my combustion temps are safe. If I burn 1.5 threads, I'm still safe. If I burn 2 I start looking to change the fuel map. If I burn 3 threads, I'm either lucky I made it through the run, or I hurt something and I'm just confirming that the combustion temps were too high. :frown:
Light plated plugs such as NGK and Champion work real well for that type of plug reading. I also use a plug with a very short ground strap. A hot groud strap will set off the methanol.
Thanks, Don, like i said sounds like a good idea.. Plugs arent that much so id say that they're definatley worth it...
After you've determined your tuneup you can leave the plugs in. But, if you're making changes towards the more dangerous side,.. read the plugs.
I was running Q16 and alky on a 10.8:1 target. Alky was a little over 10% of the mix. If there was any detonation at those levels the rod bearings would be hammered after one instance. There would be deformation and evidence of crank to bearing contact particularly in the top half of the bearing. A little detonation is not ok. All the rod bearings looked great on tear down.
This type of damage on high mileage engines could be simply metal fatigue too. Just keep the feelers out and check for patterns.
This type of damage, pre-ignition type damage lacking the other typical signs of detonation or pre-ignition looks like the type of damage you see in a methanol engine that's been tuned too close to the edge.
This type of damage, pre-ignition type damage lacking the other typical signs of detonation or pre-ignition looks like the type of damage you see in a methanol engine that's been tuned too close to the edge.
What I'd REALLY like to know is... what's the limit when running straight C16 ?
How much boost and timing will it tolerate ?
On an ohv v-6 with the engine built to run high boost and about 8.5:1 CR id guess its upwards of 50psi. You have to take into consideration the pistion design and rod length vs stroke.
What most think is that it is ok for a little detonation. Therefore they think they can tune off of KR. I never thought that way and always stayed ahead by adding in extra octane. They will learn eventually that there is no substitute for octane when you are running high cyl pressure. If i picked up KR on any of my passes i would have just pulled the engine and tore it down regardless of how i thought it was since i know it would be hammered.
