ACCURATE DYNO ?
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 805
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From: Vasteras, Sweden
ACCURATE DYNO ?
Has anyone had the opportunity to compare the result from a real dyno with Desktop Dyno 2000 or Engine analyser 3.0? Are the results accurate?
I have calculated some cam combination for my 460 cui and my feeling is that Engine analyser is more precise than Dyno 2000. Engine analyser has more input variables in most cases, but fewer on head flows.
Can I be on the right track, when I calculate my new setup with this programs?
I have calculated some cam combination for my 460 cui and my feeling is that Engine analyser is more precise than Dyno 2000. Engine analyser has more input variables in most cases, but fewer on head flows.
Can I be on the right track, when I calculate my new setup with this programs?
Safety Car
Joined: Apr 2002
Posts: 3,551
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From: No link, No dupe
Re: ACCURATE DYNO ? (Lasse)
I have wondered that as well. I found the exact specs for my engine, and put that into DeskTop Dyno. DeskTop Dyno always seems to come up with a little more horsepower that what I actually am making. In my case, it was 10 horsepower off, which is not bad when you consider all possible variables the dyno doesn't account for.
One reason may be that when you input the CFM for a carb or EFI, the Dyno assumes that the fuel metering is precise and the engine will use 100% of that; not too rich, not too lean. To compensate, I usually pick a slightly smaller cfm figure.
One reason may be that when you input the CFM for a carb or EFI, the Dyno assumes that the fuel metering is precise and the engine will use 100% of that; not too rich, not too lean. To compensate, I usually pick a slightly smaller cfm figure.
Race Director
Joined: Sep 1999
Posts: 11,358
Likes: 379
From: Plano TX
Re: ACCURATE DYNO ? (Lasse)
I've found DD2000 to be optimistic by about 2-7%. Engine analyzer is slightly pessimistic by about 2-5%. With engine analyzer I have to enter "no accessories" to get close to what my engine dynoes with accessories.
Thread Starter
Burning Brakes
Joined: Aug 2000
Posts: 805
Likes: 0
From: Vasteras, Sweden
Re: ACCURATE DYNO ? (zwede)
I have the most variable of my engine, but for the intake have I used generic street singel plane. Instead of Edelbrock Torker.
My rectangular heads gives me cam times 290+ for the best overall results, but I'm looking for some bottom end also.
The best setup I have found, are with:
Comp Cam 280HR with 9.5 C/R => 512 HP@6000 / 486 TQ@5000 and bottom-end 312 TQ@2000 / 212 TQ@1500
and
Crane 139721 (276/284 dur) with 9.2 C/R => 496 HP@5500 / 482 TQ@5000 and
bottom-end 350 TQ@2000 / 249 TQ@1500
Are the bottom ends enought to get a civilized engine (4 speed manual)? Can I trust on this bottom figures?
(C/R optimized for detonations in Engine analyze)
My rectangular heads gives me cam times 290+ for the best overall results, but I'm looking for some bottom end also.
The best setup I have found, are with:
Comp Cam 280HR with 9.5 C/R => 512 HP@6000 / 486 TQ@5000 and bottom-end 312 TQ@2000 / 212 TQ@1500
and
Crane 139721 (276/284 dur) with 9.2 C/R => 496 HP@5500 / 482 TQ@5000 and
bottom-end 350 TQ@2000 / 249 TQ@1500
Are the bottom ends enought to get a civilized engine (4 speed manual)? Can I trust on this bottom figures?
(C/R optimized for detonations in Engine analyze)
Instructor
Joined: Mar 2002
Posts: 239
Likes: 0
From: Fredericksburg VA
Re: ACCURATE DYNO ? (Lasse)
Lasse,
I've found the Dyno2000 to give incorrect horsepower curves (the shape not the magnitude) when the header selections are chosen. If you read the instructions, you'll find that the program assumes complete scavenging of the clearance volume at all engine speeds when any of the header selections are chosen. This is never the case.
The Dyno2000 is generally pretty close actual peak torque and peak horsepower (maybe a little optimistic), but use the high-performance manifolds selection to see the actual shape of the horsepower curves. In real life, you can change the scavenging RPM range of the header by changing header dimensions. Extending the top end always comes at the expense of the lower midrange, and vise versa. We don't much care about the low-end when headers are used.
I've found the Dyno2000 to give incorrect horsepower curves (the shape not the magnitude) when the header selections are chosen. If you read the instructions, you'll find that the program assumes complete scavenging of the clearance volume at all engine speeds when any of the header selections are chosen. This is never the case.
The Dyno2000 is generally pretty close actual peak torque and peak horsepower (maybe a little optimistic), but use the high-performance manifolds selection to see the actual shape of the horsepower curves. In real life, you can change the scavenging RPM range of the header by changing header dimensions. Extending the top end always comes at the expense of the lower midrange, and vise versa. We don't much care about the low-end when headers are used.
