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Thread: Blower Thermodynamics

  1. #71
    DEL51
    Whipple Charged:
    picked up 70 hp from 11.8 to 13 with a 1471? Was that steady state? Thats pretty rare in a marine roots blower.
    And, yes, you can pick up torque and not hp, not at the same rpm, thats not what I said, but at a lower rpm while not making much hp. To give you an example, figure the cost of 100+hp on that same engine with 13lbs. of boost, not to mention you can achive a higher psi before detonation because of the cooler air charges. Not only that, it doesn't vary over time, they last longer, smaller, more compact, quieter, etc.
    There is no comparison, call up Littlefield, he has to run a screw compressor on the alcohol car that he runs because the roots is no wear near competitive, even though it has major rule advantages with weight and engine size.
    Thanks,
    Dustin

  2. #72
    DEL51
    Whipple Charged:
    picked up 70 hp from 11.8 to 13 with a 1471? Was that steady state? Thats pretty rare in a marine roots blower.
    And, yes, you can pick up torque and not hp, not at the same rpm, thats not what I said, but at a lower rpm while not making much hp. To give you an example, figure the cost of 100+hp on that same engine with 13lbs. of boost, not to mention you can achive a higher psi before detonation because of the cooler air charges. Not only that, it doesn't vary over time, they last longer, smaller, more compact, quieter, etc.
    There is no comparison, call up Littlefield, he has to run a screw compressor on the alcohol car that he runs because the roots is no wear near competitive, even though it has major rule advantages with weight and engine size.
    Thanks,
    Dustin I have no reason to call him, a blown alcohol drag application is not my intended use, it is cool though.I paid 2500.00 for my 1471 add 500 for accessories.So I am at the low end of the roots cost estimate.That is still 4k under the whipple.The dyno session was a ramped pull on a DTS dyno. No steady state comparison.Final power number was 1166 @ 6500rpm.Tis was with the air cleaner on and 110 octane fuel.This motor was 1117 on pump gas@ 11.8 lbs of boost.My point is that excellant power can be made with old technology. This is comparable to a different 572 whipplecharged engine referred to in a previous post in this forum. No dual drive belts or belts popping off. I think your product is good but not when the price and looks come into play. Assuming I had the money to spend for a new whipple quad rotor, I would be better off going with a twin turbo/EFI setup similar to what Unchained is doing.It is VERY hard to beat a simple roots setup for great power and price.If he were to start out with a roots he could convert to one of your whipples when he has the money.I am curious about steady state dyno pulls. Do they yeild different numbers than a ramp type test?Thanks for posting the comparisons,very informative. When the screw blowers become more competitive price wise I will consider them as an alternative.These are my opinions and I do not want to seem dismisive of your good points.Thanks for responding
    [ January 29, 2003, 05:35 PM: Message edited by: DEL51 ]

  3. #73
    Infomaniac
    A "sweep" test usually shows a higher number than a "step" test.

  4. #74
    DEL51
    Infomaniac:
    A "sweep" test usually shows a higher number than a "step" test. On the bottom of my dyno sheet it says," inertia factor .96".I wonder if this may account for the difference.When you dyno your project engine what type of test will you run? and what are the pro's and con's of each?

  5. #75
    Infomaniac
    It will be a sweep because 99 % of them are.
    The computer controls the acceleration of the sweep test.
    A step test gives a few seconds for everything to stabilize at each RPM tested.
    In the early days a manual operated dyno used the step test. It is nearly impossible to do a sweep manually. I have tried. And If you did no two would be the same.
    Maybe someone else will add to pro and con issues.

  6. #76
    Badboat1
    As I would call a ramp test and a steady state test.IT is about 15-25HP down on a ramp,but you need to make 4 or 5 ramps and average them for a good reading the dyno will spike some numbers at times.The ramp will allways be lower than a steady state pull. just my 2 cents been doing this shit for over 20 years.I will post some steady state pulls for you tommorow.What Rpm per sec.you talking also.
    Badboat1
    [ January 29, 2003, 09:19 PM: Message edited by: Badboat1 ]

  7. #77
    Whipple Charged
    Theres certainly still power in older technology, but I think you might be missing the point, there is a huge difference, not a minimal difference. Also, there are not dual belts, just one that runs on two blowers. It's also a very quiet serpentine vs. the short lived and noisy 8mm/cog. For the amount that we've sold, we have had little belt problems.
    The difference in dyno test and power numbers provided are different for every engine, but with a roots, steady state will continue to fall in power as the temp increases, a 10-15 second swept test is no comparison to a full throttle run in a stable boat. Temps will continue to increase through the rpm range. With todays computer controlled dynos, you can do a lot longer swept test, something closer to 45 - 60 seconds for a typical boat run and 10 minutes WOT for endurance testing. Mercury racing does 20 minute WOT runs on the big motors to give an example.
    But when your refering to the amount of money spent, on that exact motor, we could get another 100-150hp (not saying it's needed) without breaking a sweat and gaining durability, not losing. So depending on what your starting with, getting that extra power on the desired octane gas could be cheaper. Maybe somebody built the same motor as yours, but wanted to run 91 octane and make the same power, they could lower boost, etc. Otherwise they were stuck running higher octane or bigger ci or heads, etc. Maybe somebody wants to make 1000 hp on a 500ci motor with pump gas, etc. Either way, theres always alternative soloutions, some are turbos, some centrifugals, some roots, etc.
    Dustin
    [ January 30, 2003, 12:56 AM: Message edited by: Whipple Charged ]

  8. #78
    Infomaniac
    bump for first page of archive

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