water mixture help?

[white90]

i went to the track today. i melted the electrodes on some plugs. not bad just back a little. my question is, would the mixture effect this? i was injecting 60% alky, and 40% water. if i run 1/3 alky and 2/3 water would this help? if not i will have to pull some timing. thanks for the help

also should i switch from alky to methanol. im running the 70% alky isopro solution. which would have the best effect and what percent. thanks again

[hotrod]

Isopropyl alcohol acts more like a fuel that an antidetonatant.

You should increase your water percentage or reduce you timing advance or booth until you figure out what was happening.

Methanol would need a different blend for best performance. You may have been on the ragged edge of pre-ignition which can kill an engine very quickly ( ie as in melt the tops out of pistons and burn valves ).

One of the reasons they went to a 50/50 blend of water and methanol on the combat aircraft is at higher percentages of methanol they would get pre-ignition. If they substituted isopropyl alcohol for the methanol they would blow engines due to its lower flamability limit.


Be very careful --- drop back a bit and work up slowly, you may have just missed melting an engine.

Larry

[white90]

Isopropyl alcohol acts more like a fuel that an antidetonatant.

You should increase your water percentage or reduce you timing advance or booth until you figure out what was happening.

Methanol would need a different blend for best performance. You may have been on the ragged edge of pre-ignition which can kill an engine very quickly ( ie as in melt the tops out of pistons and burn valves ).

One of the reasons they went to a 50/50 blend of water and methanol on the combat aircraft is at higher percentages of methanol they would get pre-ignition. If they substituted isopropyl alcohol for the methanol they would blow engines due to its lower flamability limit.


Be very careful --- drop back a bit and work up slowly, you may have just missed melting an engine.

Larry

how much timing should i back down, also im going to colder plugs. will that help at all? if i ran straight water would that control the detonation?

[hotrod]

Unfortunately WI tuning is largely an experimental process. I can't give any hard and fast numbers for you as I have never tuned that engine with WI.

That said ---

Yes definitely go to a colder plug, might even go 2 steps cold if you can find them.

I'd probably start by dropping about 2 deg on the spark advance.
Too much spark advance causes huge increases in cylinder pressures and temperatures. If that does not solve the "plug eating" then I'd suggest dropping to a 50% water/50% alcohol mix and make a run and then pull the plugs to see whats happening.

Dropping to straight water would definitely be the safest approach, then gradually add back in alcohol step by step.

Just be aware that your current setup is on the ragged edge, so back off a bit, and then go slowly and carefully in a step by step process.

Larry

[white90]

Unfortunately WI tuning is largely an experimental process. I can't give any hard and fast numbers for you as I have never tuned that engine with WI.

That said ---

Yes definitely go to a colder plug, might even go 2 steps cold if you can find them.

I'd probably start by dropping about 2 deg on the spark advance.
Too much spark advance causes huge increases in cylinder pressures and temperatures. If that does not solve the "plug eating" then I'd suggest dropping to a 50% water/50% alcohol mix and make a run and then pull the plugs to see whats happening.

Dropping to straight water would definitely be the safest approach, then gradually add back in alcohol step by step.

Just be aware that your current setup is on the ragged edge, so back off a bit, and then go slowly and carefully in a step by step process.

Larry

actually i changed my plugs to 2 steps colder. only the front 4 plugs were fried. the back 4 were a little hot though. why would this be? in ject the alky/water into the front of the carb in the primaries. could it of been the allky that fried the plugs?

[hotrod]

Sounds like a mixture distribution problem. I'd switch to straight water and see what it does. You may need to run multiple jets to get an even distribution.

It will probably take some experimentation to figure things out.

If your using a single jet in front, you may want to switch to 2 jets one on each side near the rear of the primaries.

The other option would be to pull the manifold and carburator and have it flow tested by some one with a flow bench.

You might have to use multiple EGT gauges to figure out what is happening.

You might try running it up to the point it starts to spray and cutting the engine while its spraying and then pulling the carburator (if you can) and see if you can see a big difference in how wet the manifold runners are.

Not much help I know but you'll just need to do some tests to figure out what is going on.

Larry

[white90]

Sounds like a mixture distribution problem. I'd switch to straight water and see what it does. You may need to run multiple jets to get an even distribution.

It will probably take some experimentation to figure things out.

If your using a single jet in front, you may want to switch to 2 jets one on each side near the rear of the primaries.

The other option would be to pull the manifold and carburator and have it flow tested by some one with a flow bench.

You might have to use multiple EGT gauges to figure out what is happening.

You might try running it up to the point it starts to spray and cutting the engine while its spraying and then pulling the carburator (if you can) and see if you can see a big difference in how wet the manifold runners are.

Not much help I know but you'll just need to do some tests to figure out what is going on.

Larry

someone told me i should switch to straight methonal. what you think. they said that it is better than alky, if so what %, they said 100% meth, im not too sure about all that though

[hotrod]

I'd start at 50% water 50% methanol as it is widely regarded as a good mixture for most applications. Your setup may like a different mixture better, but try it as a bench mark and go from there.

larry