are desktop dyno results acurate?

[big_truxx]

i was bored and decided to install my copy of desktop dyno 2000 on the comp. i figured good time to see how much torque my 84 454 put out. when i ran the #'s on a stock engine, it came out with 202hp @ 3,000 and 402tq @ 2,000 rpms. now i was wondering about that. since i know that when my dad bought his 89 4 door dually in 90 new, that the specs on it were supposed to be something like 265hp and 300tq this with tbi. so is this desktop dyno thing acurate? i changed the bore and stroke to that of the caddy 500 just for kicks and it came up with 205hp and 438tq peak at the same rpms as the 454.

 

[dyeager535]

As long as the data you use is accurate, the results from what I have seen are pretty darn close, something like within 5%. If you know who he is, David Vizard did a test of some dyno programs, (not sure if DD2K was one or not) and at first he thought they were wrong, then realized that the dyno's themselves were the problem...one dyno gave quite a difference from another in numbers. Once he had that figured out, the results from the programs were very accurate.

There is at least one catch, and thats the roller cam. Apparently that setting in DD2k is WAY off, so use roller cam specs, but select flat tappet, that will get you closer.

The only "test" I personally know of is a guy that has a Monte Carlo, and took it to the track. Since you can figure out the output of the engine based on the track times, vehicle weight, etc., he was able to compare the two, and that was within 5% of what DD2k said.

 

[JDBlazer454]

From my personal results on DD to actual Dyno results of my 70 Camaro it wasn't even close and that was with true actual specs. Was so very disappointed to see the true Dyno results but it was fun running a real dyno

 

[k5floyd]

ive played with it a lot, and i have to say unless you put in EVERY single detail , it wont even be close to accurate. and even then, i still think it overestimates by a lot.

 

[k20]

As long as the data you use is accurate, the results from what I have seen are pretty darn close, something like within 5%. If you know who he is, David Vizard did a test of some dyno programs, (not sure if DD2K was one or not) and at first he thought they were wrong, then realized that the dyno's themselves were the problem...one dyno gave quite a difference from another in numbers. Once he had that figured out, the results from the programs were very accurate.

There is at least one catch, and thats the roller cam. Apparently that setting in DD2k is WAY off, so use roller cam specs, but select flat tappet, that will get you closer.

The only "test" I personally know of is a guy that has a Monte Carlo, and took it to the track. Since you can figure out the output of the engine based on the track times, vehicle weight, etc., he was able to compare the two, and that was within 5% of what DD2k said.

Haha, David Vizard is the head of our FSAE team at school. Crazy frickin british guy.

 

[thezentree]

vizard is UNCC's motor guy, not just FSAE. that man always has somethin to say, usually its pretty insane. definately an interesting fellow to say the least.

thats all i have to say about desktop dyno

 

[k20]

you know what the heck I meant, o yeh, hijack over, least for me, le meow. O btw, 1800 posts!

 

[big_truxx]

i thought that the #'s were a tad high. but i was looking at the cad company and d/l'd the catalog. this is what i found interesting;

We will start with our low compression buildup, and move on to the high compression engine later on. Our low
compression short block was based on a ’76 spec rebuild, and was built with 8:1 instead of 8.5:1 compression due
to piston modification for later race combos not detailed here. The short block was bored 0.060” over, with 0.002”
piston clearance, reconditioned stock rods with ARP fasteners on an OE crank turned .010/.010 (not balanced), and
assembled following stock clearance specs using the following parts:
And the dyno says: 493.5 Lb-Ft at 2600 RPM and 302.1 HP at 3600. Standard off the shelf cast ‘74-’76
replacement pistons (Pg 11)
True Roller timing set (Pg 12) OE HEI distributor
Moly rings (Pg 10) OE camshaft, new lifters 120cc heads (‘74-’76) #493
Clevite rod and main bearings (Pg 10) reconditioned OE pushrods Straight 45° valve job (OE valves)
Durabond cam bearings (Pg 10) Our light duty street springs (Pg 12) OE 76 manifolds and carb
And the dyno says: 493.5 Lb-Ft at 2600 RPM and 302.1 HP at 3600.

and just looking again at dyno 2000 #'s, i see at stock parts option with 600cfm carb dual plane manifold hyd lifters stock exhaust etc etc etc all stock or low end options, the #'s read 196hp @ 2,000 rpm and 423tq @ 3,000 rpms. so taking people who have done this a lot and dynoed their engine and comparing it to the dd, seems like the dd was a bit low. unless i change the exhaust to small tube headers w/ mufflers and then it says 225 & 486 at the same rpms. so the "stock" part may not be close enough to the actual part that is in the engine right? so the dyno 2000 is really good for fun and a figure close to what the actual is?