Huge knock issue.

[markmurfie]

Cylinder head temperature difference between fuels is imperceptible. The exhaust gas temperature might be slightly less given an equal energy output, but not anything significant. We are talking about a 100* difference in their peak temperature, so heat transfer is going to be nearly the same at a given energy output. I would even lean towards using alcohol fuels will increase temperatures as you will be probably be on a more aggressive tune whether it be timing, leaner PE, or increased boost, it will be making it produce more power. More energy released from the fuel, more heat to dissipate. The easiest most effective things to do is run a higher water to antifreeze ratio, a lower thermostat to bring the base coolant temps lower, a larger radiator for increased heat capacity, a higher flowing water pump to increase flow through the water jackets, a less restrictive exhaust to let the hot exhaust gasses escape quicker, and vise versa colder intake air temps (phenolic spacers, better intercooler system same concepts as the radiator with capacity and flow rates, interchiller/ ice tank systems to lower base coolant temps).

Cylinder pressure is the threshold for knock. You want flow to produce more power and avoid increasing pressure if you can. That goes for the air going through your engine, the coolant in your coolant system, the air flowing over your radiator, the air flowing over your intercooler, the air flowing over your heat exchanger, nearly every thing is safer with higher flow at lower pressures.

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[thelostotter]

I have had some at 0.016 and some at .020 but normally 0.017-0.018. Did you check each cylinder with the rings that came out of that cylinder or did you check them all with the same rings

Checked each cylinder with the rings that came from that bore.

 

[Bmaughan]

Cylinder head temperature difference between fuels is imperceptible. The exhaust gas temperature might be slightly less given an equal energy output, but not anything significant. We are talking about a 100* difference in their peak temperature, so heat transfer is going to be nearly the same at a given energy output. I would even lean towards using alcohol fuels will increase temperatures as you will be probably be on a more aggressive tune whether it be timing, leaner PE, or increased boost, it will be making it produce more power. More energy released from the fuel, more heat to dissipate. The easiest most effective things to do is run a higher water to antifreeze ratio, a lower thermostat to bring the base coolant temps lower, a larger radiator for increased heat capacity, a higher flowing water pump to increase flow through the water jackets, a less restrictive exhaust to let the hot exhaust gasses escape quicker, and vise versa colder intake air temps (phenolic spacers, better intercooler system same concepts as the radiator with capacity and flow rates, interchiller/ ice tank systems to lower base coolant temps).

Cylinder pressure is the threshold for knock. You want flow to produce more power and avoid increasing pressure if you can. That goes for the air going through your engine, the coolant in your coolant system, the air flowing over your radiator, the air flowing over your intercooler, the air flowing over your heat exchanger, nearly every thing is safer with higher flow at lower pressures.

Everything you’re saying makes sense but oddly enough ...now that I’m on e85 at a much higher power level, my head temps drop almost 20 degrees after a WOT pull. That never happened on 91 at almost 200hp less. Is that not due to the fuel change?

ive been wanting to change my coolant ratio for a while now...what’s an acceptable water/coolant ratio that won’t cause any kind of corrosion harm? I’m in az and the car is kept in a garage so freeze point isn’t really a factor.

 

[Bmaughan]

one other thought: it’s my understanding that specifically water injection is extremely effective in controlling cylinder temps... anyone have first hand experience with this?

 

[Jackson1320]

Checked each cylinder with the rings that came from that bore.

thats a little tight for boost. Even for N/A it’s tight if you are really pushing it. Bore * .005 is as tight as I would want it for performance N/A and *.007 for boost. Do you know what your new short block is set to?

 

[Jackson1320]

one other thought: it’s my understanding that specifically water injection is extremely effective in controlling cylinder temps... anyone have first hand experience with this?

Controlling detonation yes

Everything you’re saying makes sense but oddly enough ...now that I’m on e85 at a much higher power level, my head temps drop almost 20 degrees after a WOT pull. That never happened on 91 at almost 200hp less. Is that not due to the fuel change?

ive been wanting to change my coolant ratio for a while now...what’s an acceptable water/coolant ratio that won’t cause any kind of corrosion harm? I’m in az and the car is kept in a garage so freeze point isn’t really a factor.

In Arizona and an aluminum block aluminum radiator I wouldn’t worry too much about corrosion you can run 25% coolant with distilled water and be fine

 

[markmurfie]

Key word there is distilled water. Don't go putting tap, or drinking water with trace minerals in it. Its a sealed system and as long as you keep it clean and flushed everything from seals to surfaces will be good for a long time.

 

[Bmaughan]

Any thoughts on my situation with the head temps dropping? I know alcohol is an excellent charge cooler but I was under the impression that it also help control cylinder temps. Not that I had a scientific reason why, I guess it was just an ... whether it be the effect in latent heat or just the shear amount of fuel being sprayed...

I found this on an old drag racing site.
is this inaccurate? Genuine question.. I don’t pretend to be any kind of expert..

“One of the most important topics is the superior cooling effect that alcohol has on a racing engine. The high oxygen content mentioned earlier is also what gives alcohol its superb “cooling effect” capabilities. This is because the oxygen introduced as part of the alcohol fuel raises the latent heat of evaporation within the engine. In layman’s terms this means that heat energy is removed from the engine when the alcohol changes states from a liquid to a gas. Alcohol has nearly ten times the cooling-effect as gasoline. This is the reason that alcohol engines run cooler and ultimately place significantly less demands on the racecar’s cooling and battery systems. Alcohol runs cool enough that it is common to not need the fan to aid in cooling the engine. Between round chores are as simple as fueling it back up and mentally preparing for the next round. This can become extremely important in the summer-time months in round robin style bracket racing”

 

[thelostotter]

thats a little tight for boost. Even for N/A it’s tight if you are really pushing it. Bore * .005 is as tight as I would want it for performance N/A and *.007 for boost. Do you know what your new short block is set to?

I’m still NA, I ended up setting all the rings to match the loosest bore so all top rings are .019” and second rings are .022”.

 

[markmurfie]

Are they talking about ethanol or methanol? Be carful in your research when you read alcohol. Its a family of multiple liquids.

Ethanol is not much difference from gasoline. On the other hand methanol has a far far greater cooling effect. So much so you can use it and get away from running an intercooler.

Boiling points (majority of heat taken away during liquid evaporation)
Gasoline 185*
Ethanol 173*
Methanol 148*

Heat of evaporation as liquids
octane(gasoline) 128 btu/lb
Ethanol 385 BTU/lb
Methanol 501 BTU/lb

Then from their stoichiometry the alcohols having more mass being injected, they are harder to evaporate, but more heat is taken when they do evaporate.

Then you can get into heat release rates of combustion, where methanol is 20% that of gasoline, and 75% that of ethanol. But that is all related to the power output of the engine and you need ~40% more alcohol fuel mass compared to gasoline so about the same amount of energy is produced just slower.

Then just to be clear, all this heat came from the fuel being injected and releasing energy. The heat that fuel picks up, gets released again, and maybe goes out the exhaust on the next combustion cycle. The only true way the heat leaves is the exhaust or the head/cylinder walls/ pistons and the radiator/oil coolers.

 

[Bmaughan]

That’s good advice/info.. the article was definitely emphasizing methanol but was stating e85 as a solid compromise. That’s why I wondered if running e85 along with water/methanol injection would be effective in combating high cylinder temps under high boost.

 

[Jackson1320]

I’m still NA, I ended up setting all the rings to match the loosest bore so all top rings are .019” and second rings are .022”.

That’s enough for N/A. If you plan to go boost later I would open them up a little. I gap top and second ring the same. The top ring gets hotter and closes more so it will naturally give you the .001-.002 tighter gap you want

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