DSmith

Has anyone compared the results of a desktop dyno 2000 to a read dyno? I have the dyno 2000 on my computer and when I put in all the info on my engine it comes up with 340 hp 450 torque. The car pulls hard and feels good but thats bigger numbers than I think it can make. The cam is a 270/276 roller with 1.6 rockers. forged flat tops. vorteck heads(ported), headers 3" exhaust with flowmaster. MSD 6.

I know that the Dyno 2000 does not calculate for timing, injectors and several other things but how close can it be if I have everything else where it needs to be?

89RsPower!

I've never used it or compared numbers but the overwhelming consensus on here seems to imply that DD2000 is extremely liberal in overestimation.

AJ_92RS

I'll give you the #1 hint....

DO NOT use the roller lifter option unless you're running a solid roller cam. This will give unreal torque figures.

If you have an aggressive hyd. roller cam, using the solid lifter option will give more realistic numbers.

If you read the instructions (I know it's against the "guy rules") they even say this.

dankhound

The other things that really help is to have flow numbers for the heads and the exact timing for your cam. If you have those two things and take the others advice the numbers are almost dead on for ENGINE dyno numbers. Chasis dyno numbers will of course be slightly lower.

Fast305

Desktop dyno is more accurate with seat to seat timing not timing at .050". They even state this in the manual. My 305 is overestimated by 30 ft/lbs when you use the .050" specs. It is right on the money when you use the advertised specs. Read the manual and follow their instructions and you will find the program fairly accurate. Shorty headers should be simulated by HP manifolds & exhaust, etc. More importantly it gives you the overall shape of your power curve even if it tends to be 5-10% optimistic. I accounted for approximately 20% drivetrain loss and the numbers on desktop dyno almost matched my rear wheel numbers. I dyno'd 250 rear wheel horsepower. Desktop dyno said I would make 315 horsepower. Divide 250 by .80 and you get 312.5. (315-312.5)/315*100 =0.8% optimistic. The torque numbers claimed 370 ft/lbs. I was able to make 290 ft/lbs at the wheels. 290/.8=362.5. (370-362.5)/370*100=2.02% optimistic. Darn respectable for a guess if you ask me.

Stekman

Yep. It is best to use seat to seat duration specs. If you use the .050" duration, the computer guesses at what the seat to seat may be.

Damon

My version gives some pretty "sane" numbers, but that asumes I put in "sane" specs. Garbage in/garbage out. Having correct head flow numbers is important. Cam specs have to be reasonably right, although I haven't found it to read much different whether using advertised or .050 specs (at least with flat tappet cams).

Don't over-estimate your intake flow. If you have a 750 CFM carb, put it in as 650 CFM. The air cleaner and other restrictions knock down the actual CFM of your total intake system as-installed in the car quite a bit. More than most people think.

Also, don't over-estimate your compression ratio. Many people think their compression ratio is about 1/2 point higher than it actually is. Head gaskets that have more cc's than they think is one common reason. Another is assuming flattop pistons are zero cc's, when they are actually much more like -6cc's. Also, most pistons sit "in the hole" at least .025" in a stock-deck block, not at zero deck.

Lotsa little things can add up to a number that's pretty far off.

On my 383 blower motor I was REAL careful to put in numbers that were as close as I was capable of providing it. DD2000 said I'd make 470HP. I actually make just over 480HP, so it was pretty damned close.