Josh 91RS

My freind is building me a motor that on desktop dyno puts out about 455 horses. Ive always heard that desktop dyno estimates a little high. He said that hes used it multiple times in the past and been extremely close on accuracy. He said his brother is really good with it and showed him how to use it. When he built his mustang, and his brothers 72 camaro engines it was pretty damn close. Anybody have any comments on desktop dyno? And if it estimates high, how high?

Apeiron

It's not just a little high, it's usually a lot high. I compared my engine's dyno sheet with Desktop Dyno's prediction. I got the curves to match pretty closely by telling it I had stock exhaust manifolds instead of headers.

It doesn't really do that good of a job of predicting the output of a given combination, but it can show you what kinds of results you'll get out of certain mods if you ignore the actual numbers and just look at the changes.

ViciousZ

iTrader: (1)

Some friends of mine and I were playing around with it and put in the specs on all of our cars. I don't know about the hp estimates because none of us have ever dynoed our cars, but the ETs were really close to what each of actually ran at the track, like within one to two thenths.

The ODB

think about it for yourself. How could a real dyno (let alone a computer program) have any direct relation to pushing an actual car through a quarter mile run?

Every computer simulation I've ever run has estimated extremely low and the closest one was still 1.5 seconds slow on E.T.

Chvywolf

I have desktop dyno. And for all the numbers i've crunched it seems to be pretty good. The only thing it can't account for is drive train loss. Whenever i get the numbers for an engine for my car i always figure in 20% loss for the 700R4. If i'm figuring for a manual i'll use bout 18% and it seems fairly close. Again though you have to figure, it's a program not real life. Just use it for what it's intended. It won't give you exact figures just an estimate. I've learned a lot from it as far as what mods to get, and what will give me the most power now and what to get first for leading up to something else.

For example: Getting a cam will help out a lot for power. However, getting the heads ported and polished first may not give you as much but then put in the cam and holy crap. What a differance.

Just my .02 cents

"Oh yeah, well i'm taller"


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89 RS Conv 305 700R4
85HO heads
Edelbrock intake
Holley 600
Hedman Hedders and Y pipe
Flowmaster
B&M MegaShifter

[This message has been edited by Chvywolf (edited March 18, 2001).]

Josh 91RS

Basically i just want to know that if desktop dyno shows 455 horsepower, will i be close? Like i would be happy with 350+ hp at the rear wheels. If desktop dyno is showing those high numbers should i be happy with the engine?

3.1 firebird

let us know your combo, I'll plug it into my DtD and tell you what I come up with.

RMK

I've heard that the 700 R4 has a power loss of between 20-23% I always go with the highst so that I'm not dissapointed and presently surprised

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1987 IROC-Z Auto (LB9)
Black/grey interior with the stance of a streetfighter

Mods
Custom exhaust. 4 Inch pipe from the headders all the way back to a single muffler at the rear. No Cat.

Future mods due in March:
K&Ns
RAM Air
Air foil
AFPR

Hoping to get a couple of tenths with that lot

Brent

iTrader: (1)

FWIW, here is David Vizards review.

http://www.motortecmag.com/archives/...FEB010301.html

RB83L69

It's reasonably accurate, at least for comparing one well-characterized part to another. However, if you blue-sky some part (heads and exhaust in particular) and then get yanked back down to the real world when you get sticker shock, the numbers you got with the big imagination are useless. It's only as good as what you feed it. Honesty is the best policy here.

If this is a 350 you're building, I have serious doubts as to the accuracy of that number. If it's a 400, it's possible but still not too likely when things like chassis restrictions and hood clearance (real world!!) get factored in.

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"So many Mustangs, so little time..."
ICON Motorsports

jcb999

I have found it to be about 10 percent high in most cases. In some cases it is very close. Over the last few months I added several combinations that have been listed in the various mags. I even added some airflow files from the CHP tests. The MAG tests with the AFR heads and comp cams are very close to what DTD provides. DTD tends to be a little more optimistic with the combinations that use TFS and Dart heads.

PS, if it indicates a 350 is making 450 hp with anything less than 10.5 to 1 compression, a very good set of aftermarket heads, and a real good Hydroller cam, it is BS. About 1.2 hp per cubic inch is really good for a 350 with aluminum heads and flat tappet cam.

[This message has been edited by jcb999 (edited March 19, 2001).]