Engine and Transmission Tech

Dan, Regarding the .7 hg, 4bbl sizing for optimum power. I read the Engine Masters mag. when I can. Case in point, 350" sbc, std. Holley 750 cfm.,447hp at 6,200. Your formula provides max hp. with 916 cfm.? I'm thinking air flow rating system for slide plate injection would roughly equate to inlet port flow, ie. no pressure loss? Thanks, roverman.

Jim, Since there was no takers on the flow vs. tube dia. I thought I'd take a plug at it.

Steep learning curve on the pressure head loss per ft of methanol. I've run a bunch of calculations based on pressure loss for water and tried to sub in the specific mass/density of methanol at 49.38 lb/cu.ft. I get a different number each time of course because I'm just an animator by trade. LOL.

My point is you could get away with going down to .250 ID with some loss in flow because the friction is pretty low at 8" length. loss in head pressure looks like about 12% with the decrease in dia. from .375 ID (3/8 tube).

Hope that helps.

Really? I'm astonished. I found out that a 5' head of water is about 2.2 psi. I'd never have thought that that would be enough to push 1gpm of water through a 1/4" tube. Maybe I should set up a siphon to test it, could be about right.

Jim

I think that would be a good idea. I could have missed something. It was a super lengthy process to try to work through it. More math then I've had to do in a long time. The hardest part was trying to find a reference I could use to calculate something so short (8"). Most of the equations were based on 100 ft of tube.

Could be that the Mass/Density of Methanol is 78% of water. OR I messed up one of the numbers.

I was a bit surprised too because the reduction in head pressure vs. tube dia. seems like it should be exponential because of the reduction in cross-sectional area. I guess it could be that 120 gph at 14 psi isn't based on 3/8"??

I don't know. It's pretty confusing. Just trying to help.

I appreciate it a lot Nik. I did the test, using a 3 ft head since I'll be losing 2 ft going from the bottom of the condenser to the top of the evaporator and using a 5-1/2 ft length of 5/16" fuel hose. It emptied the 1 gallon water jug in right at 55 seconds into the lower jug. So I'd say your numbers are close. Maybe I should see if I can buy some Methanol and try it with that.

Jim

Jim or clan.I don't have chart for comparative coefficient of friction for various materials/coatings. I have been quoted .05 for a proprietory, hard anodize process. Anybody? Thanks, roverman.

To estimate the size of carb needed I am pretty certain that the calculation is:
Street Carb CFM = Max RPM multiplied by Displacement (in cubic inches) then divide this by 3456, then multiply by 0.85 (volumetic efficiency). for Race multiply by 1.1 instead of 0.85.

Air Capacity (in cubic inches per minute) = RPM x Displacement (in cubic inches) divided by 2.
Air capacity (in cubic feet per minute) = RPM x Displacement (in cubic inches) divided by 3456.
Cylinder volume = pi/4 x bore squared (in inches) x stroke (in inches).
Stroke = displacement (in cubic inches) divided by : pi/4 x bore squared (in inches) x number of cylinders.
Bore = the square root of: Displacement (in cubic inches) divided by: p/4 x stroke (in inches) x number of cylinders.

This is old school (and I am sort of old) but it should be pretty close.
There is an "Auto Math" book that was published back in the early 90's that showcase these calculations



Edited 1 time(s). Last edit at 12/18/2009 11:25PM by bashby.

Lots of easy to use automotive calculators:

[www.avenger-valkyrie.org]

Thanks Carl, Those will probably be real helpful. The hard part is putting together the right formula so that the results make sense. Luckily there are smarter people than me who are willing to help with it, and at this point it looks like the math is worked out. Now it's down to material compatibilities. Never easy.

Jim

Jim, I'm wondering, will the frictional coefficients be a factor in the calc's ?

I doubt it Art, we've left some leeway in the figures and in the end the unit will be instrumented to see how it performs. Coolant flow can be adjusted up or down to optimize cooling on that side so the limiting factor appears to be evaporator size and air flow restriction and we've gone as big as we can go there. Right now we're looking at n-hexane as a coolant and need to pump about 6 gpm (360 gph) through the core. I'll be running a test in the next day or two to see if that is practical or not.

Jim