[Diy_efi] Water metanol turbo assist (Greg H)

[Greg Hermann]

At 12:14 PM 1/9/03, Derek wrote:
>> >But generally, 12.5:1 is referred to as being the maximum power WOT gaso=
line
>> >AFR. Just wondering why you would want it leaner than that? Is max power
>> >at 14:1
>> >or so, given excellent in-cylinder cooling (meth, water, or any mix)?
>>
>> Yes, max power IS at 14:1 (petrol) or so given adequate in-cylinder cooln=
g
>> from another source, such as water or a water/meth mix.
>> >
>> >Not arguing, just trying to figure out if running it leaner than .85 lam=
bda
>on
>> >my car (lots of methanol, 0F inlet temps) would be of any benefit.
>>
>> I think it would.
>
>Greg,
>
>I ran it to stoich at 1BAR of boost with a ton of methanol, and it never ev=
en
>blipped the knock sensor. So the cooling is doing it's job in terms
>pre-combustion cooling.
>
>Got another question for you. Can't believe it didn't occur to me before. W=
hat
>about EGTs? Won't they be sky high and likely melt something? I'm afraid of=
 a
>knock free meltdown. I never got a EGT, once I got a wideband I figured I
>wouldn't need it.

Not to worry. Internal cooling during the compression stroke is a
_WONDERFUL_ thing. Say you do enough to lower the peak temp (at TDC, before
ignition) by 400=B0 F. Doing that not only means you are gonna do less
negative work on the compression stroke, you will also lose the SAME 400=B0 =
F
peak cycle temp (immediately after the burn is finished), you are going to
lower the compression pressure AND peak cycle pressure significantly
(meaning less loading on the bearings, con rods, and bearing webs), AND you
are going to LOWER the EGT--not by the full 400 =B0 F, but proportionally.

Another goody that comes out of the lower temps through the cycle is LESS
heat rejection to the cooling system and through the pistons into the oil.

YES--because of the lower peak temp and pressure, there will be LESS
positive work done on the power stroke--and the efficiency of the power
stroke will be a little bit lower--but this is very slightly more than made
up by the fact that you needed less negative work on the compression
stroke. The fact that there is lower heat rejection to the cooling system
and the oil leaves you with a pretty significant net GAIN in efficiency and
power, though. Not to mention a whole lotta parts that will last a lot
longer because the load on them is lighter (for the same net power output).

Go ahead, put an EGT on it and get a NICE surprise !!

Greg



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