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Explanation on Dyno Testing

G

GWTW-000

Guest
Can someone please explain Dyno Testing and the difference if any of horsepower and torque numbers from the way it is calculated on an airboat verses the test on a Chassis Dyno? On the Caddy as well as others prior to 1972. I think the HP numbers were calculated different than they are now. My new engine has been tested on a Chassis Dyno and produced 415 hp and 520 fp of torque. It had all of the bells and whistles when tested. Will this be the same no matter how it is tested or will it be different at the prop or fly wheel (flex plate)? Please enlighten this Georgia boy so I can talk intelligently on this subject. Without knowing it seem that it would have higher ratings not having a/c, power brakes, power steering etc. and only dealing with the crank.

Thanks
KJC
 
The numbers you posted look real strong.would be interested in knowing at what rpm the torque and hp peak at .
 
I know this is a lot of information but here is what I bought and am awaiting anxiously for. I can't wait to put Waterthunders 2.38/1 soft drive on with the new K sereis prop and try it.

Engine Specs

Block: 75-76 500 cubic inch, bored .040" with approximately .010" milled off the deck. ARP studs are used for the main bearing caps and the heads

Crankshaft: is stock stroke and cut .010" under on the rod and main journals

Rods: are aftermarket forged steel from CMD with ARP bolts

Pistons: are custom made forged by Arias and are .040" oversize with a 9.7:1 compression ratio

Heads: are '75-'76 large chamber with 114cc combustion chambers with bowl work and valves unshrouded. The intake and exhaust ports were ported for street/strip use. The valves are 2.12" intake and 1.80" exhaust. Valve springs are from MTS and are single springs with a damper. Seat pressure is 100lbs @1.850" and 300lbs @.550". Coil bind is at 1.150". Max valve lift should be kept at .600" for clearance purposes.

Rocker Arms: are fully adjustable from MTS using Harland sharp rollers 1.65:1 ratio

Pushrods: are standard length on the intake at 10.200" and the exhaust are 10.230"

Intake Manifold: is a custom 2-piece design from CMD and is fully ported and port-matched to the heads.

Carburetor: is a Holly 850 Double Pumper with glass float sights

Distributor: is a custom-made unit from PSD. Mechanical advance has 18 degrees and can be adjusted. Initial timing is set between 15018 degrees for general use.

Camshaft 1: is currently in the engine - is an MTS MT20.

Camshaft 2: is an MTS MT15


This engine has approximately 2,000 miles on it. It originally came out of a Cadillac Coupe de Ville. It was capable of turning that car sideways when "required". Horsepower as tested on a chassis dyno is 415. Torque was 520. The engine made these numbers with A/C, power brakes, alternator and power steering, with a Turbo 400 transmission and a 12 bolt GM mid-size car rear end.

Thanks
KJC
 
There are two common dyno's a chassis dyno and a flywheel dyno. Chassis dyno's are the simplest and the most common however most are not accurate because they get their reading at the rear wheel after the drive train. Engine builders argue this constantly the import or bolt on horsepower peddlers love Chassis dynos because they simply charge people to wheel up their car and run on them and make simple changes with the ecu and charge you. Here are the differences a Chassis tells you HP after the drive train all rear ends and trany's suck up different amounts of power. A Dana 60 will rob twice as much power as a GM 10 bolt and with a trany a T10 will rob 1/2 as much power as a C6. So when you get a Chassis dyno number you do not know what kind of horsepower your engine is making it's only an estimation. Felber also proved how you run your car on a chassis dyno will affect the reading. He witnessed a car run twice, differently each time and read a HP difference of around 30%. So on a 400HP motor that is around 120HP. A flywheel dyno will give you an exact horsepower and torque figure for your motor and only the motor.
 
Cam number two is what you want! That mts 20 a lttle more than you want for a boat 2800 to 6500! That a solid liter cam ! The 15 is a strong cam more bottom !2200 5400 ! thats a good boat cam !
 
with the intake i would change it if it is a larry kruzick vally plate with the ford intake the edelbrock would be better.i believe one of the guy's from cadillac power ran one and said it did not perform as well as he hoped.and you may get some good money for it.
 
I AM WITH MR B ON THE MANIFOLD ! ON A BOAT YOU WILL NEVER USED THE GOOD PART OF ( RPM ) OF IT ! ELENBROCK PERFORMER ! SEEMS TO BE THE NORM ,PORT IT ! CLEAN UP THE TOP OF THE RUNNERS LEAVE THE BOTTOM ALONG ! PORT MATCH IT ! SOME LEAVE A LITTLE HUMP ON THE BOTTOM! JUST BEFORE THE HEAD !TO KICK THE WET FLOW BACK UP ! SOME DO IT ! SOME DONT ! THAT IS JUST ANOTHER DEAL OR THREAD! :D
 
KJ C - It's good to hear you are still after that performance. I clearly remember your first posts about the old hull and issues with it. Looks like you are on the verge of having a real beast. Hope you can make it to the KRVSA's Family Reunion on Oct. 07 on Kissimmee. I'd love to see your boat.
 
I have seen hp numbers incredibly low on a "chassis" dyno, while your typical rear wheel torque will drop an avg of 18 percent due to drivetrain loss. Torque numbers are fairly accurate , but hp numbers for some reason don't read right on a Cadillac, even at 7000 rpm. An engine dyno is straight up and measure flywheel hp as one fellow stated. 520 with 18 percent added back (which ain't entirely accurate as you subtract 18 percent, but close enough) is alittle over 600, if done accurately by multiplying the proper formula, you should be around 580 or so. I don't remember formula, but do recall past reconfigurations
 
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