Author Topic: Robbing Horsepower  (Read 769 times)

Shelby_r_b

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Robbing Horsepower
« on: May 15, 2019, 11:16:00 PM »
I’m curious. It’s my understanding that the following installs will rob a car of horsepower:

- Auto Transmission
- AC
- Thermactor

Is this true, and if so, how much HP does each take away?

Thanks!
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Side-Oilers

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Re: Robbing Horsepower
« Reply #1 on: May 15, 2019, 11:25:15 PM »
So will P/S.
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2112

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Re: Robbing Horsepower
« Reply #2 on: May 16, 2019, 01:12:49 AM »
Water pump?

I don't think the Thermactor (in '67) is as bad as other accessories.

Kent

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Re: Robbing Horsepower
« Reply #3 on: May 16, 2019, 03:56:24 AM »
AC
Power Steering
Thermactor
Choke Plate
Alternator
Water Pump
Motor Chain
Camshaft

also Automatic is robbing a lot compared to the 4 speed toploader

The Thermactor is maybe not to bad but not like a modern drag racing system becuase on my 68 Fastback Dragster I also have a smog pump to catch the crap and collect it in my catch can, from what I know a smog pump also if its belt driven like mine and transport the crap in a catch can will gain hp because of the cleaner air/fuel mix so higher octane ratings will stay where they are and a big plus the pump helps the pistonrings to seal better because of the vaccum it creates. Dynosheets show gains from 15-35 hp with such a system. I think the most is coming because of the cleaner air/fuel mix it will create.
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67350#1242

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Re: Robbing Horsepower
« Reply #4 on: May 16, 2019, 10:29:05 AM »
Cooling fan esp. if non clutch
67 GT350  SJ 02/01/67
67 Coupe  SJ 11/16/66

gt350hr

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Re: Robbing Horsepower
« Reply #5 on: May 16, 2019, 11:30:15 AM »
AC
Power Steering
Thermactor
Choke Plate
Alternator
Water Pump
Motor Chain
Camshaft

also Automatic is robbing a lot compared to the 4 speed toploader

The Thermactor is maybe not to bad but not like a modern drag racing system becuase on my 68 Fastback Dragster I also have a smog pump to catch the crap and collect it in my catch can, from what I know a smog pump also if its belt driven like mine and transport the crap in a catch can will gain hp because of the cleaner air/fuel mix so higher octane ratings will stay where they are and a big plus the pump helps the pistonrings to seal better because of the vaccum it creates. Dynosheets show gains from 15-35 hp with such a system. I think the most is coming because of the cleaner air/fuel mix it will create.

     The major gain is from removing crankcase pressure that directly improves piston ring seal. there is a small gain from actually "pulling" oil out of the crank. I don't see any change in a cleaner air fuel mix as you suggest as it doesn't affect intake charge. I have used smog pumps for over 25 years on drag race cars. The same can be done with a dry sump oil system. The scavenge side can pull vacuum and a secondary ( smog) pump is not needed.
    Randy
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gt350hr

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Re: Robbing Horsepower
« Reply #6 on: May 16, 2019, 11:56:28 AM »
I’m curious. It’s my understanding that the following installs will rob a car of horsepower:

- Auto Transmission
- AC
- Thermactor

Is this true, and if so, how much HP does each take away?

Thanks!

    An automatic transmission uses a torque convertor which is sort of like a fluid clutch so no "pedal" is needed when you come to a stop. This "fluid coupling" is not capable of 100% efficiency so there is a power loss. In the '80s manufacturers developed a "locking" torque convertor which helped allot.
The automatic transmission gear train is not "as" efficient as a manual trans so there in lies the power loss.
   A/C (when engaged) robs power ( especially on older piston powered pumps simply because of the power required to turn the pump and make pressure.
"Modern" rotary style pumps take FAR less power to turn .
    "60's smog pumps aren't all that bad as far as power loss because there wasn't any pressure build up and the pump itself was not a big power draw.

     I short , ANY device that was turned by the crank "could" rob HP as noted by others above. Water pump , power steering etc. This is why "modern" cars have gone to electric power steering and more efficient water and A/C pumps , serpentine belts etc. To "make" net power , you have to start by "saving" first.
    Randy
Celebrating 44 years of drag racing 6S477 and no end in sight.

CSX 4133

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Re: Robbing Horsepower
« Reply #7 on: May 16, 2019, 02:24:32 PM »

You can recoup some of the "lost" HP by using lightweight pulleys at the crank, etc.
~Steven

 6S1806 B.Prod.Shelby

gt350hr

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Re: Robbing Horsepower
« Reply #8 on: May 16, 2019, 02:48:31 PM »
   Steven,
       Rotating weight has no affect on horsepower by itself. I have seen it many times on engine dynos by drag racers and Nascar teams.  Now if there is a reduction in pump speed because of underdrive pulleys , there could be a small power gain.
     Randy
Celebrating 44 years of drag racing 6S477 and no end in sight.

427heaven

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Re: Robbing Horsepower
« Reply #9 on: May 16, 2019, 03:19:19 PM »
Well if were getting technical ANYTHING that creates friction is a horsepower robbing bandit. Low friction ring packages, special coatings for bearing surfaces, roller bearing surfaces, seals, viscosity of oil, oil temp, air mixture struggling to get in your engine, same to get out this spent exhaust gasses, pumps, belts, pulleys, fans, oh my, my head is spinning with all the power robbing items on a car. 99 percent of the auto world doesn't give a rats tail about any of this, but the 1% care about everyone of those items. ;)

pbf777

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Re: Robbing Horsepower
« Reply #10 on: May 16, 2019, 07:12:13 PM »

You can recoup some of the "lost" HP by using lightweight pulleys at the crank, etc.

     Randy is correct, but the confusion is created if one establishes the H.P. capacities using an acceleration "chassis dyno" vs. a steady state process, as the lesser rotating mass is easier to accelerate (& decelerate) therefore the some of the total mass in motion over the time element is affected.    ???

     Scott.

Kent

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Re: Robbing Horsepower
« Reply #11 on: May 17, 2019, 05:09:02 AM »
A friend of mine who works for Bentley, Bugatti etc. always say that a big thing for robbing hp and friction is really the valvetrain that why Fiat did the Multiair which is far from perfect but a first step in the right direction

https://www.youtube.com/watch?v=Td9Gz_h7Qpg
SAAC Member from Germany and Owner of a unrestored 1967 Shelby GT500, 1968 1/2 Cobra Jet´s and some nice Mustang Fastback´s 67/68

2112

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Re: Robbing Horsepower
« Reply #12 on: May 17, 2019, 09:41:24 AM »
I thought F1 (like Cosworth) had used completely pneumatic valvetrains 25 years ago?

I won't be expecting much innovation in internal combustion engines in the future.    ::)

pbf777

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Re: Robbing Horsepower
« Reply #13 on: May 17, 2019, 11:15:05 AM »
       I think the next "big" advancement in the mechanical engineering will be the elimination of the poppet valve. 

      But then perhaps the "Green New Deal" will arrive first, and non of this will matter!    :o

     Scott.

gt350hr

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Re: Robbing Horsepower
« Reply #14 on: May 17, 2019, 11:50:43 AM »
   The modern automotive industry HAS to be concerned as CAFE requirements get tougher. For example , thin rings have been in use for years. Now oil pumps have gone to being crank driven in many cases to reduce friction from cam driven methods. Tighter bearing clearances and thinner oils are being used too. All of these changes are aimed at engine efficiency. One unexpected off shoot is these lower "drag" (friction) engines is less cylinder wear and higher mileage before a rebuild is needed.
   Randy
Celebrating 44 years of drag racing 6S477 and no end in sight.