Cooling Issue

[Offcamber1]

Why not take your nice new thick heat exchanger and mount it next to your shoulder vertically and and perpendicular to the direction of travel? A bit of fabrication for an inlet and shrouding, and the fan mounted behind the rad for sitting stationary while waiting on your run.

This might simplify the plumbing a bit as well.

As to the current configuration I'm just guessing, but I would venture that if you removed the wing it would not significantly alter the problem. Just not pushing enough air in through that narrow slit no matter how fast you are going.

Unlike Art, I have no science to back my submission.

Kip

[Stan Clayton]

So do you think this isn't part of the issue?

I believe this is your problem, Garry. Open the inlet back up to 60 sq-in and I strongly suspect you'll feed enough air into the radiator to get sufficient cooling. Back in 2005 I prepped Arnie Loyning's Runoffs winning CSR with about 240 hp. We ran 60 sq-in ducts (6" by 10") back from the front bodywork through the front a-arms to the radiator's plenum, which provided enough cooling flow for the engine at Mid Ohio.

That's about 4 hp per square inch of inlet. Based on that rough order of magnitude, with a clean ingress path your 47 sq-in might support 188 hp, but with the wings blocking some of the airflow 47 inches might not be quite enough, especially if the taper ratio from the opening to the inlet exceeds about 9 degrees.

[Jim Garry]

Two things.

1. Please keep in mind that there are dozens of Cheetahs road racing (as was mine in Charlie Smith's hands). These cars use the same cooling design as mine, minus the wing, and cool fine. Mine used to cool ok until changing the rad and closing the intake. I think that undoing those two things should be first on my list followed by other ideas as necessary.

2. I'm grateful for all of the enthusiastically offered advice on this forum and one on one offline. What a wonderful resource Apexspeed is and all of its family.

I've got plenty of time to think about the suggestions and plan a course forward.

Best regards to all and Happy New Year again.

[dereklola]

Back in 2005 I prepped Arnie Loyning's Runoffs winning CSR with about 240 hp. We ran 60 sq-in ducts (6" by 10") .............. which provided enough cooling flow for the engine at Mid Ohio.
That's about 4 hp per square inch of inlet.

Stan - that's a useful reference for me on a similar project. I realize you meant it as a rough guidance - but did you use one 6x10 duct - or two? Two ducts, each 6x10, would be 120 sq.in. - or only 2 hp per square inch of inlet. (I'm assuming the car had twin rads one in each sidepod).

My own reference is my old Atlantic (similar power) which had two openings about 2x12 = 48 sq.in. or about 5 hp per sq.in. It was over cooled up to 100+ degrees. Just looking for clarification and a quick reference. Thx - Derek

[Stan Clayton]

Stan - that's a useful reference for me on a similar project. I realize you meant it as a rough guidance - but did you use one 6x10 duct - or two? Two ducts, each 6x10, would be 120 sq.in. - or only 2 hp per square inch of inlet. (I'm assuming the car had twin rads one in each sidepod).

My own reference is my old Atlantic (similar power) which had two openings about 2x12 = 48 sq.in. or about 5 hp per sq.in. It was over cooled up to 100+ degrees. Just looking for clarification and a quick reference. Thx - Derek

Hi Derek,

Yes, I meant it as rough guidance.

You should be able to see from the photo that there are two inlets...they are 6"x10" each. One went to the single water radiator, while the other fed air to the oil cooler...no dual water radiators.

Cheers, Stan

[HayesCages]

As has been mentioned several times but in differing ways: Airflow is where it's at right? (and water flow...)
A long time ago a friend crashed his FF smashing the front mounted radiator. Researching options to replace it revealed several, one of which was cooling fins-per-inch on the core. Too close together and no air flow. Since his rad. used a thick, 4-core design we choose the lowest fin-per-inch core we could find. Worked perfectly.
Maybe your core fins are so close that the airflow is slowed too much?

[DaveW]

As has been mentioned several times but in differing ways: Airflow is where it's at right? (and water flow...)
A long time ago a friend crashed his FF smashing the front mounted radiator. Researching options to replace it revealed several, one of which was cooling fins-per-inch on the core. Too close together and no air flow. Since his rad. used a thick, 4-core design we choose the lowest fin-per-inch core we could find. Worked perfectly.
Maybe your core fins are so close that the airflow is slowed too much?

Agreed - fin density (and even the fin configuration) is a critical variable. As you said, fins too close together, or a too thick radiator, and airflow can be reduced to the point where it won't cool, plus parasitic drag increases. On the other hand, with a too low fin density there isn't enough surface area to transfer heat to the air. So, as with almost any variable related to a racecar, it's a compromise. And predicting how it will work in the absence of sophisticated CFD and accurate modeling is usually no good. So trial and error is, IMO, the best approach for us amateurs.

[Jim Garry]

As has been mentioned several times but in differing ways: Airflow is where it's at right? (and water flow...)
A long time ago a friend crashed his FF smashing the front mounted radiator. Researching options to replace it revealed several, one of which was cooling fins-per-inch on the core. Too close together and no air flow. Since his rad. used a thick, 4-core design we choose the lowest fin-per-inch core we could find. Worked perfectly.
Maybe your core fins are so close that the airflow is slowed too much?

Could be. One of the things I'll look at.

[Jon Jeffords]

How confident are you regarding the accuracy of your temperature reading? Can you submerse your temperature probe in a pot of boiling water to verify it is reading a stable 210-214 degF? In the morning before you fire the engine, does the indicated coolant temperature seem logical (as compared to the overnight ambient)?

[Jim Garry]

How confident are you regarding the accuracy of your temperature reading? Can you submerse your temperature probe in a pot of boiling water to verify it is reading a stable 210-214 degF? In the morning before you fire the engine, does the indicated coolant temperature seem logical (as compared to the overnight ambient)?

Good questions Jon. I held off doing it for a long time but finally about the middle of the summer (2017) I did do the boiling water test and it was on the money.

My gauge only goes down to 100 degrees so I can't tell about ambient temperatures.


Thanks,

[RussMcB]

My gauge only goes down to 100 degrees so I can't tell about ambient temperatures.

I started to say you could down south, but not this week! :-)

[Mondial]

You are running autocross? and your runs are maybe 60 to 90 seconds? Could you remove the front wing and try a run to see what it would do the temps?

[Jim Garry]

You are running autocross? and your runs are maybe 60 to 90 seconds? Could you remove the front wing and try a run to see what it would do the temps?

Sure. Of course, I'll be doing work on it this winter and hopefully the problem will be resolved. If it isn't, I will take a run without the wing.