I watched an episode of engine masters dealing with parasitic drag of electric, clutch, stock and flex fans. They tested on a small block 350 on a Dyno. they posted losses of 12 to 25 hp if I recall correctly. But, what is the real world loss on our Buick motors, actual loss on the track. No guesses please, if you switched over to electric and picked up , that’s what I would like to see. The cooling aspect would be a different question that I’d rather not worry about right now. So ladies and gentlemen thank you.
The problem with that test is that when a car is moving the airflow helps the fan turn negating some of the loss. Sitting still on a dyno is not the same. Electric is best but I took my flex fan off at the track and only picked up .05....so only about a 5hp loss. Also a SB Chevy lacks the torque we have so would be affected more....
I swapped from the stock clutch fan to a electric fan. I saw no noticeable difference at the track.. the difference was so small that it could have easily been better air. Also, I think we've met, I was there the night you spit your driveshaft out through the floor.
BQuick, I had a similar thoughts on a anemic small block compared to ours. .05 it’s not worth the expense and install especially where I have no cooling issues currently. Thank you so much for the input. The wagon is currently running 1130s. If I needed that half a tenth to pop a 10, my arm might have to get twisted. But I’m not there yet. 436 d skylark, are you the fellow we talk to at Epping this past season. I know we talked about the driveshaft incident a little bit during the downtime. That was one heck of a night. thanks everyone for your input certainly appreciate it . Bret
I haven't been to Epping since the pre-covid days. I was pitted with you and Bryan the night it failed. I helped push it on the trailer. I had the four speed car that was spinning badly running low 12s at that time.
Yes, yes, yes I remember now. Everything broke that night from the transmission all the way back to the rear end. When the driveshaft went out.
I've never been around drag racing but I have been in oval racing my entire life where cooling is essential. We found the best combination was a 4 bladed fan and a good tight shroud. After about 5,000 rpm a semi-vacuum forms inside the shroud and terminal velocity is achieved across the radiator. Any RPM above that number does not increase further drag on the motor since there is no more air to pull. It's like putting your hand over a vacuum cleaner hose, the motor speeds up because max negative pressure is achieved and there's no more air to pull. The worst combination is a mechanical fan with a loose or no shroud since the fan has infinite air to pull and requires a lot of power to drive it.
I can tell you this.. 70 GS 706 HP 494 Full weight 3.73 gear PS/WP/ALT driven off the crank Ran consistant high 10.70's and a couple of low 80's at BG in 2019 Last pass on Friday it broke the crank pulley... and picked up about tenth and a half.. (10.61) and a couple mph.. At that speed, with that heavy brick of a car, we have to be talking about 30 HP here...
Another thing I see many times is someone running AC pullies in a drag car overdriving the fan and water pump. Underdrive non-ac pullies are worth .10 by slowing fan, pump and alternator down.
I run electric fans and pump on the race car not for the additional power but cooling between rounds. Get into the pits shut the car off and leave the pump and fans run for 5 mins and the engine is cool to the touch.
You are talking about episode 20 of Engine Masters. I know everyone has there opinions and all are justified one way or another but I personally believe in the dyno. I spent many years in my career doing Test in / Test out procedures to come up with the info I needed to move forward. I have no overheating issues now even after I repeatedly thrash it on a hot day but I am removing my mechanical fan for a electric one. It's cheap, easy and 20-25hp increase is like a cam change. I am all in.
For those wanting to eek out those 30-ish +- horsies. Electric fan(s) with a on/off switch. Fire up car, flip fan on (so no DC load from fan during engine start). Wired in relay (using kickdown switch, or ?) to cutoff fan during WOT, that way, fan is on when needed, during start, in line, up to staging, and then off during the run, back on after big end and back to pits, or if hot lapping. Maybe...
Don't need to do that. Watch episode 20. The alternator draws a minimal amount. Hook up the fan to a properly rated relay and wire size for your application. All of this can be controlled with a thermostatic switch in the water jacket. Don't need a kit, just do some surfing for the right parts that work for you. I have a HVAC background. This is a basic setup that anyone can do. Keep it simple and it will always work.
Do, or do not. Might be a need, might not. I have two fan setups on both my '64 and '68. Total draw about 60 amps, when screaming. (And a spike for a split second when first kicking on to get up to speed) Controlled by two separate thermal switches (and relays) to come on at separate temps. So, there is a draw on the alternator, but I am not worried about any loss of power as these are not drag cars. We can talk all day about how to skin cats. I have quite a long history in auto, mechanical, computer/electronics, aircraft systems and powerplants, and know my way around the electrical side of things. Simply offering another POV, and the doing is pretty simple. People helping people. [/drift]
I continue to thank you for all the responses. Obviously a higher amp draw with two fans. Do you concentrate on CFM of a fan. Do you look at the surface area the fan is pulling through. What brand of electric fan typically is most reliable. Be it dual or single. There are many options out there I hope there’s a few standouts.
