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#1
01-26-2009, 03:33 PM
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Strange numbers with Desktop Dyno
I just finished inputing my numbers in Desktop Dyno 2003. I'm not sure if the results are close to actual performance, but I've got some strange results in my opinion.
I know these softwares give approximate results. To be as close as possible, I had my heads, intake and pistons tested for CC and flow. I used Desktop Dyno to make sure I've got a good cam. - 400, 0.040 over - #62 heads (all chambers machined to 73cc) - 4-valve reliefs cast pistons (all machined to 15cc) - Edelbrock Performer intake - 750CFM Q-Jet carb - Hedman 35270, 4-tubes headers - Pypes 2.5 exhaust with Street Pro mufflers - COMP Cams XR264HR with hydraulic roller lifters - 9.25 CR Peak HP was 326 at 4000RPM, which seems correct to me. But the torque... I've got 497 at 2000RPM (180HP) and still going over 400 at 4500RPM. That means a 97 drop in a 2500RPM range? This is calculated at the flywheel, I understand the torque will be reduced when applied to the wheels. But.. Is it me or the torque numbers are high? I expected the torque level to drop well below 4000RPM range with that cam. Can I expect those numbers if I put the engine on a dyno? Or is it very far from the thuth? Last edited by MescaBug; 01-26-2009 at 03:49 PM. |
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#2
01-26-2009, 04:01 PM
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On the engine dyno your not going to get a 2000 spread in rpm between where the engine makes peak torque and where it makes peak power. Looking at actual dyno sheets from my combos and others I've seen it's typicaly about 900 to as much as 1400 rpm, and with 'big' solid rollers it can go higher. Much depends on the type of cam, intake involved, stroke, etc.
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#3
01-26-2009, 05:05 PM
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That cam is a toque monster, it may be right. I had one in my 462 and it was ridiculous. It ran out of breath pretty quick though.
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#4
01-27-2009, 03:27 AM
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Just on a whim- try setting the cam "straight up" (split overlap), ignoring whatever ICL was recommended by Comp Cams.
497 lb.ft. @ 3,000, or even 2,800 RPM, would be within reason- but not @ 2,000, without excessive advancing of the cam. So... what were some flow numbers for your heads- say at .500" lift of the intake? Are you sure you set up the "custom flow" file correctly for the simulator?
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Anybody else on this planet campaign a M/T hemi Pontiac for eleven seasons? ... or has built a record breaking DOHC hemi four cylinder Pontiac? ... or has driven a couple laps of Nuerburgring with Tri-Power Pontiac power?(back in 1967) Last edited by Jack Gifford; 01-27-2009 at 03:32 AM. |
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