23 June at Dyno :roll: • The Dodge Challenger Message Board

by **plum-crazy** » 20 Jun 2006 16:57

Yes, finally i decided to try dyno test.
I want to know real numbers of this engine, any recommend?
I think the test must be done in "D" with auto trans but is necessary disconnect the kick down cable? Otherwise when we push gas, tranny will reduce to second gear and give a wrong result.

Anyone knows something about it?

Thanks.

by **dave-r** » 20 Jun 2006 17:37

I know someone i can ask.

by **plum-crazy** » 20 Jun 2006 18:13

I have a couple of days but is a first contact to know about the engine power, I have not a lot of things to change :roll:

I'm still thinking about shorten the rear end...

by **dave-r** » 20 Jun 2006 18:58

I asked MMA club member and good guy Alex how he used to do them when he used to dyno race cars and exotics.

Yes Drive.

You disconnect the kickdown, roll it out in First, then Second and nail it in Drive from about 20 mph.

Depending on the dyno you run it up to the redline or if the dyno guy is good until the power has peaked which is usually a bit sooner.

Then either lift off and allow it to run down or if the dyno is modern you punch neutral at the top of the run and let it coast to a halt so the dyno can asses the transmission losses to calculate flywheel Hp/torque as well as wheel figures.

Hope that helps.

by **plum-crazy** » 21 Jun 2006 6:33

Yes, Dave it's the same I want to do, I thought is the correct way.
Thanks.

by **plum-crazy** » 27 Jun 2006 15:41

That's right.
Dyno's curve
Anyway i have a question that dyno's man do not clear to me.
If power at rear wheels are 237kw/322hp I can't understand the real power of the engine be 259.9kw/353hp.
I understand is about 20% lost from the engine to rear wheels. :?:

by **dave-r** » 27 Jun 2006 16:30

I usually add around 70hp to the rear wheel figure to get crank horsepower. So I would say your engine is making nearer 400hp.

by **dave-r** » 27 Jun 2006 16:36

A drag strip quarter mile speed (mph) will confirm the rear wheel horsepower if you know the weight of the car + driver). The time in seconds for the quarter mile will tell you how much of that power made it to the track surface.

If the power is less than you expected look at the distributor timing curve and carb tuning again.

Put in as much total timing as the compression/petrol type will allow. Get you initial idle timing up more too. Somewhere between 14 and 18 degrees.

by **Misaeus** » 27 Jun 2006 16:42

the mags and builders claim around 500 HP at the crank with specs close to PCs engine.
are they all VERY optimistic?
is this number not obtainable from these specs in the real world?

by **Misaeus** » 27 Jun 2006 17:37

the previous owner of my RR claimed a best of 12.8 ET at 108 MPH.

i use your spreadsheet and for 108 MPH in a 4000 pound car i need some 393 RWHP.
393 + 70 = 463.

the specs of my engine are not too far from the PCs engine, so, i think 400 HP are small numbers.

the Chally is very fast and really kicks your a**.

something is out of place...

by **plum-crazy** » 27 Jun 2006 18:27

i need to check damper position because the maximum advance at idle is 4 degrees without pinging.
I'm using a mopar distributor and this unit uses centrifugal and vacuum advance. I will purchase an MSD mechanic distributor and will check damper at first cilynder TDC to assure I'm in the right way to tune it.
Anyway i want to change my demon 850 for a 750 because I'm checking mixture is lean sometimes due to a excessive air into the carb, then if i change jets to a higher number car makes a lot of black smoke.