Engine temp vs. hp?

[Paul Workman]

The trouble with "rules of thumb" is that often the rule is remembered, but not the attending circumstances forming the basis of the "rule".

For example: The rule of thumb is that "oil will float on water". But, the underlying circumstances are the oil and water are relatively pure AND in the presence of gravity...(You see where I'm going, doancha?): Change the circumstances - i.e. add detergent to the mix in a zero gravity environment - and the rule that oil rises to the surface...is wrong!

So, hopefully the example above opens our minds enough to ponder this: If knock/detonation is not present at say 205 degrees F at WOT, are we sure a motor will really put out more hp if temperature is reduce to say 170 degrees? If so why?

I'm dubious of the argument that air density entering the engine is the entire answer: A 350 ci 4-stroke motor at 7000 rpm (efficiency factor included) will pull approx 10 cubic feet of air/second. I don't see how there is going to be any significant transfer of engine heat to the rush of incoming air - to reduce the air density by any significant amount**. I'm not a mechanical engineer - I just have a physics background (and you know what they say about having just a little knowledge and being dangerous!).

**The operative phrase. What is or is not "significant" might be in the eye of the beholder, I suppose.

Just food for thought. (Hey! Gimme a break! There's feet of snow on the ground, and I can't go out for a ride and it's killin me!)

P.

[tomtom72]

Jingle bells Paul!

Okay I'll play along....with my meager knowledge. I think I hear what you're saying. How is it possible that the air gets heated significantly due to the short amount of time it actually spends going from the air filter to the back of the valve, right Paul?

I don't have cold air intake so I look at the OE set up & think the under hood air is hot already due to the engine radiating heat? Next, there is conductive heat transfer due to the hot intake system parts that the air travels thru? I don't know how to calculate the amount of heat absorbed over one second, but if there is a difference in temps the heat has to be transferred. My visualization is that there is a column of air from the A/Filter to the I/valve and that's how it comes to absorb heat because it's like a solid chunk waiting to get sliced by the intake valve?... okay, maybe not so much.

[sammy]

paul. i ttok my white car to fontana on the 4th of dec. i finally moved mat sensor out of the engine compartment like mark h does and found some interesting results. i did it originally due to seeing the temps spike to 120-130 while witing in the staging lanes to run. well it works now my mat sensor allways reads the same as the outside temp +or minus 4 deg. i also found out the car ran now 2 tenths better when the engine temp was at least 180 but not over 188. i didnt have the time to get her hotter than 188 that day .ran out of time . when the temps were 165 178 the car slowed down 2 tenths and around 1.8 mph . weird huh . will try again on jan 4 at a private track rental and see if the results come out the same .merry xmas sorry about the snow . just go do snqow angels with the z.lol

[Bob G]

What where your 60 ft times on theese runs?

[sammy]

on the 90s runs. with the flowmaster exhaust 12.35 @117.80 mph with a 1.964 60 ft. with the dr gas setup 12.10 @119.47 mph1.967 60 ft . i was using the mickey thompson drs 315x35x17which i didnt like as well as the nitto nto5r drs that i am using now . the white car with the corsa went 12.48@116.47 with a 1.91 60 ft and with my 23/4 in ladder style crossover and 3 in dyno max super turbos with dual 21/2 exits. best run 11.94@117.90 mph with a 1.873 60 ft. i have ordered a set of 275x40x17 nittos thinking that the taller sidewall might help the launch some. i am also using snubber extentions so that the snubber is 1/2 in off the knuckle on the drivers side and 1/4 of an in of the passenger . i an also going to a eaton gear type set up to get rid of the clutch posi setup which i think sometimes has a mind of its own . if the new nittos 275x40x17 dont work i will next try the hoosier 335x35x17 which pete uses very well . i need to install a line lock so i dont have to hold the car during its burnout by putting on the brakes which can get dicy at times .the ets wopuld be alot better if i wasnt racing at a da of 2700-3200 ft all the time the 11.94 run was done in july in 95 degree weather . as was the 12.10 in the blk car. maybe if it stops raining i will go back to sac and do a comparo of the different exhausts. where the da is usually 0-400 ft both cars run 3-4 tenths better there . but i couldnt use them in my comparison . all my runs in the above comparo where done in the summer time @famoso in bakersfield . best corrected time using the drag time da calcs (90) 12.10 run done on sept 6/08@858 pm corrected out to 11.685 @123.808 mphthe (92)s 11.94 run was done on july24/10@11.11pm corrected to 11.53@122.14mph das for both cars runs were between 2880 and 2887.

[sammy]

and geez who gave me the red mark, all i did was share and can fax actual time slips to any who doubt the truth of what i am saying .plus the 12.10 run is on utube for all to see .to that person have a wonderfull xmas,you arent a very nice person