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The lean mean donut machine
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Discussion Starter #1
I call into question the accuracy of DD2k. I took an atricle off chevyhiperformance.com called Cylinder Head Flow-Bench Database. Under the Edelbrock Performer head they had a 355 engine they said they dyno'd at 420hp and 440 ft-lbs of torque, using the Edelbrock heads. After typing in the specs of that motor, including the flow numbers from the heads, the exact cam specs, CR, Manifold, etc. DD2k only gave me 368 HP and 392 torque. That is a whopping underestimation that gets me big-eyed about other motors I have dialed up on the program. Has anyone else had this kind of miscalculation with the program as bad as this?
 

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"May the Schwartz be with you"
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Personally, I would only use Desktop Dyno as an indication of estimated percentage of performance increases or losses with changes of known parts. There are far too many variables to expect a relatively simple bit of software to sort out.

This is why I run UGS NX Environment...never lets me down.
 

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True,

Certain things it does seem to calculate pretty well. For instance I have never had any trouble with the head flow numbers, or selecting the correct type of style head. It seems to do very well for normaly aspirated engines when you use advertised spec with either a roller or flat tappet cam. It even still gets the numbers right when you switch from advertised to .050 spec on a flat tappet cam file, but just dont switch it to roller after that!
 

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i rad several articles in the car mags some time after it came out and they all said it was about 95% accurate.you have to remeber when entering info that alot of it only gets you close such as having a choice between dual plane intake and single plane.leaves a little room so you have to make sure everything else is accurate.i'd say 90-95%.good tool but you won't be perfect til you put the wheels on the rollers.
 

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WV hillbilly
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781 Posts
hehehe....

geee, I thought that 17,000 hp top fuel engine I developed on DD was accurate...lol
 

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I have no real comparisons to show on DD2K or Dyno Sim, but this guy seems to get pretty good results with it.

http://www.piratesofhorsepower.com/archives/2004/09/how_accurate_is.html

I'm actually interested in seeing how my final engine stacks upto the DD2K simulation, in my case DD shows about 440HP and a couple of "experts" I've talked to have estimated 400. If the experts are right it's within 10% which in my book is pretty good.

It'll be a while yet, but I will be Dynoing the engine when it's complete and it will be interesting to see who's closer.
 

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The lean mean donut machine
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386 Posts
Discussion Starter #13
I went again and checked the info I plugged into the program for that Edelbrock headed motor, and yes, it really did only put out 368 HP and 392 torque. Chevy Hi Performance actually dynoed theirs at 420 and 440, so this is more than 10% out. Here is the specs that I entered into dyno2000:

Chevy 350 4.030 bore/3.48 stroke
Heads: (2.02/1.60 valves, 28" water)

0.050 32 20
0.100 64 44
0.200 121 96
0.300 174 134
0.400 216 159
0.500 235 177
0.600 236 187

valve sizes 2.02, 1.60

Compression 9.00

Induction 650cfm @ 1.50 inHg Single Plane Manifold

Small tube headers with mufflers

Cam specs (for the DEH275 Comp Cams)

High Performance Street
Hydraulic Lifters
Cam Specs at .050 lift
duration 219 intake, 229 exhaust
lift .462 intake, .482 exhaust
LSA 110*, Intake centerline 108*

Maybe I did something wrong, I don't know, but that is what it put out on the program. The motor in question is at http://chevyhiperformance.com/techarticles/41598/index4.html it is about half way down in the sidebar under Edelbrock Performer heads.

People are saying DD2k is a good tool, but this example seems to point to the contrary.
 

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WV hillbilly
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781 Posts
Mad Maggot said:
I went again and checked the info I plugged into the program for that Edelbrock headed motor, and yes, it really did only put out 368 HP and 392 torque. Chevy Hi Performance actually dynoed theirs at 420 and 440, so this is more than 10% out. Here is the specs that I entered into dyno2000:

Chevy 350 4.030 bore/3.48 stroke
Heads: (2.02/1.60 valves, 28" water)

0.050 32 20
0.100 64 44
0.200 121 96
0.300 174 134
0.400 216 159
0.500 235 177
0.600 236 187

valve sizes 2.02, 1.60

Compression 9.00

Induction 650cfm @ 1.50 inHg Single Plane Manifold

Small tube headers with mufflers

Cam specs (for the DEH275 Comp Cams)

High Performance Street
Hydraulic Lifters
Cam Specs at .050 lift
duration 219 intake, 229 exhaust
lift .462 intake, .482 exhaust
LSA 110*, Intake centerline 108*

Maybe I did something wrong, I don't know, but that is what it put out on the program. The motor in question is at http://chevyhiperformance.com/techarticles/41598/index4.html it is about half way down in the sidebar under Edelbrock Performer heads.

People are saying DD2k is a good tool, but this example seems to point to the contrary.



Change the exhaust, the results might surprise you...
 

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as much as I love chevy hi po mag, they are in the biz of selling magazines and car parts....could be grounds for exageration via data manipulation. (air temp, elevation correction factors,humidity)
 

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The lean mean donut machine
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386 Posts
Discussion Starter #19
I already changed the exhaust and it did not produce much of a difference, it's a little closer, but not any where near what it should be.
 

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as much as I love chevy hi po mag, they are in the biz of selling magazines and car parts....could be grounds for exageration via data manipulation. (air temp, elevation correction factors,humidity)
I am glad to hear it is conservative!
 
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