Desktop Dynos, How accurate are they?

flyin 5.8 · 04-30-2002, 05:55 PM

I have Desktop Dyno 2000, I bought it because I'm buliding my first engine and I wanted to know if the combination will work. But, I do not know how accurate it is. Does anybody know of any magazine articles/books that have tested a desktop dyno agianst an engine dyno?

Also, How much HP will I loose between the flywheel and the wheels with a C4 auto trans. 20%, 15%??

Stang Runner · 04-30-2002, 05:58 PM

I really dont know But i bet they Can be Close need to Make it the same as what you put in tho to have it tha Same might not be as ez as you think But Any how I posted because I see you are not to Far from Me I like a 30 Min drive.

HellRaiser92 · 04-30-2002, 08:00 PM

My friend has that desktop dyno and it's pretty acurate (sp). And as far as how much HP you will loose it's about 15 to 20% as far as I know. Obviously the real thing (engine dyno) will be better in my opinion. I personaly like chassis dyno's better since they show what you actually have at the rear wheels.

juiceman · 04-30-2002, 08:47 PM

desktop dynos are pretty good for et and mph. not so much for hp they can be close. problem is you have to be exact on what you input.

Jeff Chambers · 05-01-2002, 06:45 AM

For my combination, DD was about 55 hp off from what we measured on the engine dyno and it predicted the peak hp & tq points to be about 800rpm less than what we measured. And that was with a carbureted combination which you'd expect its math models to be more accurate at compared to a long runner EFI model.

This doesn't mean that DD was worthless though. You've got to use it parametrically to examine the effects of a component change. Start with your current combination and get a feel for how the DD output varies from what you know about your combination. Then start making changes ONE-BY-ONE to examine how it affects the output.

I used the solver to literally run through thousands of cam combinations over the winter. In the end, it was useful in narrowing in on the cam that I did have ground but I also had to sort through some very bad cams that DD actually said made more power. It'll converge to a poor solution but the computer can't recognize the fact; that's where the user's brain power has to take over.

Bottom line, DD is qualitative not quantitative but it can still be a very useful tool.

04-30-2002, 05:55 PM	#1
flyin 5.8 Registered Member Join Date: Apr 2002 Location: Holland, Michigan Posts: 73	Desktop Dynos, How accurate are they? I have Desktop Dyno 2000, I bought it because I'm buliding my first engine and I wanted to know if the combination will work. But, I do not know how accurate it is. Does anybody know of any magazine articles/books that have tested a desktop dyno agianst an engine dyno? Also, How much HP will I loose between the flywheel and the wheels with a C4 auto trans. 20%, 15%??

04-30-2002, 05:58 PM	#2
Stang Runner Registered Member Join Date: Jun 1999 Location: Walker, MI, USA Posts: 1,202	I really dont know But i bet they Can be Close need to Make it the same as what you put in tho to have it tha Same might not be as ez as you think But Any how I posted because I see you are not to Far from Me I like a 30 Min drive. __________________ Engine: steel mounts, Under drive pulleys, K&N, GT-40 Intake ported Lower, No power steering, No A/C, Mac cold intake, 65MM TB, 255 Fuel pump, 24's, AFR 165 58cc, Rocker Arms 1.7with the stock Cam, 1 5/8 short headers, offRoad X-pipe Drive Train: 3.55, T-5 with a Pro 5.0 shifter 12.656@107.71MPH See It at www.T-racing.com/mustang.htm

05-01-2002, 06:45 AM	#5
Jeff Chambers Moderator Join Date: Aug 2000 Location: Milan, OH Posts: 2,699	For my combination, DD was about 55 hp off from what we measured on the engine dyno and it predicted the peak hp & tq points to be about 800rpm less than what we measured. And that was with a carbureted combination which you'd expect its math models to be more accurate at compared to a long runner EFI model. This doesn't mean that DD was worthless though. You've got to use it parametrically to examine the effects of a component change. Start with your current combination and get a feel for how the DD output varies from what you know about your combination. Then start making changes ONE-BY-ONE to examine how it affects the output. I used the solver to literally run through thousands of cam combinations over the winter. In the end, it was useful in narrowing in on the cam that I did have ground but I also had to sort through some very bad cams that DD actually said made more power. It'll converge to a poor solution but the computer can't recognize the fact; that's where the user's brain power has to take over. Bottom line, DD is qualitative not quantitative but it can still be a very useful tool. __________________ Jeff Chambers 1990 Mustang GT 10.032 Seconds / 137.5 MPH 14-time Street Warrior World Record Setter CRT Performance 2001 Tropic Green Mustang GT - 12.181 / 113.2 MPH 2002 Ford F-250 Crew Cab 7.3l Power Stroke - 17.41@77.2 "There's nothing boring about a small block automatic shifting gears at 9400 rpm!"

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04-30-2002, 08:00 PM	#3
HellRaiser92 Registered Member Join Date: Apr 2000 Posts: 104	My friend has that desktop dyno and it's pretty acurate (sp). And as far as how much HP you will loose it's about 15 to 20% as far as I know. Obviously the real thing (engine dyno) will be better in my opinion. I personaly like chassis dyno's better since they show what you actually have at the rear wheels.

04-30-2002, 08:47 PM	#4
juiceman Registered Member Join Date: Jan 2001 Location: ny Posts: 197	desktop dynos are pretty good for et and mph. not so much for hp they can be close. problem is you have to be exact on what you input.