Whatever the outcome this pulley deal is still good old fashioned hot rodding at it's best.
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| underdrive pulleys on the cheap https://slantsix.org/forum/viewtopic.php?t=59447 |
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| Author: | SlantSixDan [ Thu Apr 14, 2016 10:45 am ] |
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Quote: Dan, they took the belt completely off.
Right, I get that, and then they said "Whoah, we gained 20hp when we took the belt off!". What I want to know is what-all that belt was driving before they took it off.
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| Author: | Joshie225 [ Thu Apr 14, 2016 11:22 am ] |
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Quote: Quote: Dan, they took the belt completely off.
Right, I get that, and then they said "Whoah, we gained 20hp when we took the belt off!". What I want to know is what-all that belt was driving before they took it off. |
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| Author: | Badvert65 [ Thu Apr 14, 2016 12:17 pm ] |
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[/quote]As 'Zilla mentioned, a lot of the performance increase observed could also be attributed to the lower engine temperature. I know I've broken out badly from the engine cooling off while sitting in the staging lanes. Suffice to say, we have no good A-B-A data.[/quote] I am fixin to change that. If I ever get this dang race motor together, I'll have both sets of pulleys on it and try it both ways. |
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| Author: | Badvert65 [ Thu Apr 14, 2016 2:01 pm ] |
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I looked up the numbers from the article and plugged them into a performance calculator (for what it's worth) and came up with the following: 1/8 mile et>18 hp increase 1/8 mile MPH> 16 hp increase 1/4 mile et> 20 hp increase 1/4 mile MPH> 20 hp increase and again, this is taking the fan belt off (I did not calculate the weight difference of the belt) and there was most likely a difference relating to the engine temp but that variable was not listed in the article. I just find this interesting. |
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| Author: | slantzilla [ Thu Apr 14, 2016 3:02 pm ] |
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Whatever the outcome this pulley deal is still good old fashioned hot rodding at it's best.
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| Author: | SlantSixDan [ Thu Apr 14, 2016 5:02 pm ] |
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Quote: The belt was driving the fan
Aha. I thought so. That would certainly explain an artificially high apparent amount of parasitic drag alleviated by removing the belt. Here's the thing: on a dyno, the fan's gotta haul itself through standing air. Lots of wind resistance, therefore lots of power required. In a car, the forward motion of the vehicle dramatically lowers the effective wind resistance experienced by the fan. Easy to visualize if you think about it: the air is already moving rearwards, that is the direction the fan wants to pull it anyhow. It's very common for magazines to publish stuff like this: ZOMG WE FREED UP 20 30 40 HORSES JUST BY DELETING THE FAN!!!!!111!!!!!! It's very uncommon for those same magazines to bother thinking about why that might be the case on the dyno and not in an actual car. Quote: performance increase observed could also be attributed to the lower engine temperature
I don't think I agree. Read this (especially the Smokey Yunick quote). Cooler intake air, yes, that's always good thing for maximizing power output if you have no other factors to consider like part-throttle and around-town driveability, fuel economy, etc (if you do have those things to consider because yours is a street car and not a race car, then it changes to cold air being sometimes a good thing). But a colder engine? No, that's not generally better. Best power comes from a hot engine breathing cold air.
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| Author: | Badvert65 [ Thu Apr 14, 2016 5:10 pm ] |
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Quote:
Here's the thing: on a dyno, the fan's gotta haul itself through standing air. Lots of wind resistance, therefore lots of power required. In a car, the forward motion of the vehicle dramatically lowers the effective wind resistance experienced by the fan. Easy to visualize if you think about it: the air is already moving rearwards, that is the direction the fan wants to pull it anyhow.
I see your point but in this case, we are only dealing with numbers from the drag strip, not from a dyno. Granted, I used computations to get the HP figures. But they are performance numbers from a drag strip run. We just don't really know all the other parameters (engine temp, etc).
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