Intake air temp- What affect if any
 

does hotter air have on fuel mixture. I know it has an effect on detonation at some point. I have no shortage of fuel, so can't I compensate for an elevated intake air temp?? I also need to know if hotter intake air has any affect on BSFC?? I am building 540 ci motors and want to re-use my smaller 2.3L Whipple compressors with air to water intercoolers. I will be raising base compression to 9:1. My static compression will be 13.2:1. Again I have BIG injectors with plenty of fuel. I will also have a cam profiled for this exact setup. I just need to be sure this will work so I can pull the trigger and get the motors done. I do not have the option right now to go to bigger 3.3L compressors. Any feedback ???

P.S. Max boost will be 6-7 lbs at 6000rpm

Thanks !!!

Hotter intake air takes up more space with the same amount of molecules. Cold air is more dense and takes up less space. Hotter air will make you run richer.

Adding too much fuel will wash down the cyl. walls and dilute your oil. Not a good way to control detonation. If your intake charge is too hot, there are other ways to deal with it. Use a scoop to bring cool air to the intake. Take out the thermostat to cool the entire engine down. Aluminum heads tranfer heat better. Water/alcohol injection. Racing gas or a high octane blend.

O.K. More info I have aluminum heads, I do not run a t-stat,motors run at less than 120 degrees with 70 degree intake water. i always run 93 octane bought on the street, I am working on a way to get cool air to the intakes.

Every 10 degrees temp change equals about 1% difference in power.

There's room for impovement on the air inlets
on the 33's and 36's.

I added additional ducting ( 3 4" hoses per side)
from the flat area underneath the side vent grilles
down to the side bulkheads of the engine compartment.

I'll snap some pic's and send them to you if you'd like ?

My bunch a hot air!
 

Obviously inlet air temperature affects power and elevated temperature compressed air even with a rich fuel mixture will decrease power and can contibute to detonation in a supercharged engine. The smaller 2.3 compressor trying to provide enough air for a 540 cubic inch engine will be creating more heat than the larger 3.3 trying to make the same 6-7 pounds of boost. The adding of addtional fuel above reasonable safe power making levels will cause other issues for the life of the engines and the result will also be significantly increased BFSC's. If you need to use the smaller aftercooled compressor I would suggest you make sure the resulting air/fuel ratios under the real boat loads are dialed in carefully so not as to support detonation under your worst case use air inlet temperatures (use a wide band sensor in the exhaust) and obviously you should set up the motors with EGT's that will not help burn it down. I am not a real supercharging guru, but I know there are some real experts here on the forum who can probably help keep you out of trouble and in the throttle! Good Luck, have fun!

Regards,
Ray @ Raylar

I have a friend who is a trouble shooter on some 1.5-2 million dollar engines. He says in the computer they have if the intake air temp gets over 140 they shut the motor down.

When I changed intercoolers on my boat from the procharger to rtech I had cooler air temps . The efi added about 15% more fuel with the cooler air temps. I think the air temp before I changed was just over that 140 number and about 115 -120 after.

WOW what is a 1.5-2 million dollar engine?

Used to run compressors, generators and pumps in the oil field and other places. I think the AC compressor at the Denver airport has one or a number of these engines.Can produce almost up to 5000Hp 24/7

Specs on the V18 is

Dry weight 43,652 lbs
164.2l displacment
11:1 compression ratio
215 gallons oil capacity

Here is picture of one of the smaller ones.