aliveagain
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posted November 03, 2010 11:20 AM
EGT
You guys that have been running the land speed racing, what temps are you seeing at the big end?
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ZRXDean
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posted November 03, 2010 05:00 PM
AA, I can't think of anyone that records EGTs. Most use AFR, and maybe intake temps with a turbo.
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Johnnycheese
Pro
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posted November 03, 2010 05:37 PM
Gary did on his 12 no higher than 1250 with spray
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aliveagain
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posted November 03, 2010 05:54 PM
The reason I had asked is my turbo diesel truck runs up passed 1300* at times and I was told long periods passed the 1300 mark would start melting pistons. Now I hear some turbo bikes can get boost creep and how do you know how much ram air will make at 240 mph on spray or NA ? Is it an equation that at a certain air/fuel mixture the egt will be at a certain parameter? Just curious.
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dougmeyer
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posted November 03, 2010 07:45 PM
1300-1325 continuous should be no problem in a well tuned engine.
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whitehendrix
Zone Head
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posted November 04, 2010 07:27 PM
 Edited By: whitehendrix on 5 Nov 2010 03:31
well, i recall Dr. Meyer saying once ( IIRC..) 1380*F is the target EGT in general..
so, maybe diesel is a little more cool-running?
boost creep CAN happen, but it is a function of the wastegate.. if its an internal WG then the best solution is a porting of the WG bypass port where the flapper closes off the scroll. taking a carbide burr or endmill in there and opening it up to where you have .100" of seat area on valve seat usually alleviates that.. if theres a decent sized valve there in the first place. sometimes you can only hog out .050 or so from the bore. thus why an external WG is the preferred method for long runs and lots of boost that must be precisely controlled.
as far as "boost" via ram air, it's isn't as much as you think.. tho it's obviously dependent on speed.
"roughly" as a general rule, ram air will produce .7PSI @ 200 mph
at 240, exactly 1psi
at 275mph, 1.31psi.
if you wanted to go apeshit, you probably can use that on top of your known VE, CSA, port velocities and BSFC and derive a reasonable range of expected HP ( minus drivetrain losses) at a given speed.
tho ram air pressure is directly related to runner dimensions and inlet size, obviously.
egt is also a function of ignition timing and many other variables, so just a port velocity and VE are not going to correlate to a consistently trackable EGT
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aliveagain
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Posts: 5033
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posted November 05, 2010 06:02 AM
My question was based solely on metallurgy and holding up to heat. On the diesel, I can pump in a lot of fuel where it is black smoke yet it will still rise above the melting point of the pistons.so a/f ratio does not guaranty safety. I realize that diesel motors are a whole different ball game but I would think some physics would be the same. A lot is also based on curiosity as to how close to the edge are the bikes brought to.
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