Formula First engine cooling

Moderator: Dietmar

Formula First engine cooling

Postby Jeremy Soule » March 8th, 2015, 1:33 am

My car came to me minus motor had been previously cooled by factory method. 2 questions...
I read on the FFDA website, Conversion section, that the engine needs 20 Sq. In. of air intake. Is that per side or total?
I installed a new cyl temp gage from SR Racing, sensor under plug #3 (plug washer removed) and am seeing 550 deg. after 5-7 laps. I then pull in. I tried to cruze it for a few laps but then it goes right up again in 1/2 a lap.
Is 550 deg. to hot?
Thanks Jeremy.
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Re: Formula First engine cooling

Postby Dietmar » March 8th, 2015, 11:57 am

Jeremy:
I can only comment on FV- the air requirements for FST is greater as the engine is larger and does require MORE cooling.

Many years ago when I/we went from stock fan cooling to ducting directly to the heads, I employed an engineer from the local aircraft facility to do some "math". He came up with a suggested 28 square inch opening PER SIDE to duplicate the output of the fan at 5500rpm.
How the air is directed is also a factor, so in some designs it might require more than the 28 sq in or less.
But, that was the basis of my design years ago and it seemed to work fine. When I converted my D-13 from fan to ducting, I once again used that 28 sq in per side and it worked well. I never saw the temps that you indicated- and yes, that seems a bit high and by "cruising" for a few laps would make it worse as the fan is not turning fast enough.

You did not say if you are using a stock pulley or an aftermarket aluminum pulley, but the aluminum pulley would also slow down the fan speed. A doghouse cooling fan shroud , if you are using one, should allow for a lower temp on #3.

My suggestion: in order for me to give you a better comparison, you would need to relocate your temp sender. I have mine under the stock #3 cylinder head cover. There is a boss that the cyl cover is screwed down to. The sender will fit over that boss. Using this location, I get 350-375 degrees head temp. If you try that location and get higher temps, then I would look to see how I could increase my cooling efficiency.


Hope this helps

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Re: Formula First engine cooling

Postby Jeremy Soule » March 8th, 2015, 1:37 pm

Thanks for the advice and validation....
I realize my post was a little misleading, I am not using the pulley driven fan but trying to develop an outside ducted air flow from scratch.

Tried to upload JPEG photos just now but got a "Could Not Upload Attachment" message....

I have a little less than 28 sq in. per side and is tucked in along the body not out in the airstream like the ones that look like large reversed mirrors, so will look at enlarging that. Also thinking of doing the "oil drop test" around the openings to check for air flow in that area.

Not sure I copy on sensor location, do you mean screwed/bolted to a boss underneath the "tin" head cover?
Jeremy
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Re: Formula First engine cooling

Postby Dietmar » March 8th, 2015, 2:00 pm

Jeremy:

My fault- I thought you were continuing to use the stock configuration.

FOR SURE the ducting you currently have is too small with the temps you are seeing. Could be a result of having the ducts close to the body. Maybe the air is being diverted by the body and not enough going to the duct openings.

And yes, under the stock tin there is a boss that normally holds the cylinder tin in place. If you are using the stock tin, simply slide the sender under the tin, over the boss, and secure with the stock 6mm sheet metal screw.

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Re: Formula First engine cooling

Postby BLS » March 9th, 2015, 12:46 am

Jeremy,

the FST website has some technical articles including a "minimum" of 20 sq in opening each side. It also describes the location of cyl head temp and 325F max reading. This will be dependent on where the sensor is located. I think under the spark plug the reading is much higher, but I have not used one and my memory (35 years back) could be wrong.

Link to the website, select FV to FST conversion and scroll through:

http://formula-first.org/Technical/tech_articles.htm
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