DYNO RESULTS DESKTOPvsENGINEvsCHASSIS

peterd · #1 (**permalink**) 11-29-2004, 07:52 PM

I have benchmarked my 408 stroker with all three Dyno methods, in my case I actually did a chassis dyno before doing the engine Dyno. I was happy with my chassis DYNO results 423HP and 408 ft/lbs of torque, however the DYNOJET doesn't help you with drivability tuning. I use EFI with the FAST engine control, this gives me control over fuel curves.I spent most of the summer driving around trying to get my fuel numbers right for the 2000-3500rpm range under light load. I decided it was time for an engine DYNO, this allowed me to control load at all RPM. The resulting number show the differences between all three methods. Motor is back in the car however I have not driven it yet. Looks like I loose 70hp through the drivetrain

Curt C. · #2 (**permalink**) 11-30-2004, 11:11 AM

Thats a good comparison. Desktop dyno numbers are a little agressive. Any ideas why that is?

Hotfingrs · #3 (**permalink**) 11-30-2004, 02:25 PM

When I plugged my engine specs into Dyno2000 there was only 10 lbs of torque difference from the program and actual chassis dyno numbers. Played with different cams over the winter on this program and found what I wanted, and the numbers were right on with the chassis dyno.

blykins · #4 (**permalink**) 11-30-2004, 02:31 PM

Yeah, mine too.....I think my horsepower was off like 2 hp from engine dyno results.

RICK LAKE · #5 (**permalink**) 11-30-2004, 04:11 PM

PeterD Pete I did my motor build on dyno 2000 and was 6hp off and 8 lbs of tork of the chassic dyno. I am using Dynoslim now for another motor. This system is very close to real life motor numbers. I just can't figure out how some people are get big hp and tork numbers

I must be putting the wrong numbers in

Rick Lake

peterd · #6 (**permalink**) 12-03-2004, 08:02 PM

The DESKTOP DYNO calculates the Volumetric Efficency for motor. In my case I have a 408cubic inch small block. You can look at the motor as being an air pump, so in a perfect world this motor would consum 408 cubic inchs of air every 2 revolutions. At 5000 rpm each cylinder could consum 73 cubic ft/min. So DESKTOP DYNO takes into account the flow through the heads, the duration of the cam, the inlet manifold and the exhaust system, all of these items restrict the flow of air and reduce the VE for the motor. I believe the reason some people get bigger numbers than actual is because the motors VE is not reduced significantly by the heads or the cam and the restrictions come from the inlet manifold and exhaust system. Although DESKTOP DYNO allows for a selection of manifolds and exhaust systems the charactistics are not as closely modeled as the heads or the cam. I believe normally aspirated motors producing more than 1.2hp/cubic inch will get high numbers on DESKTOP DYNO.

peterd · #7 (**permalink**) 12-04-2004, 08:57 PM

Rick Lake and Hotfingrs you both indicated that you DeskTop numbers were the same as a chassis dyno. The Desk Top gives you engine numbers not RWHP?????

Hotfingrs · #8 (**permalink**) 12-05-2004, 01:55 AM

Pete
You're right. I know if the engine would be put on an engine dyno, the numbers would be way higher than what the puter program said, but as a reference for making changes, this works out. Dyno2000 said I had X number of horse and torque, ok it's at the rear wheels not the crank, but the number is close. When I make a cam change or whatever, gives me some idea of what to expect. Dyno said new cam would increase horse and torque by a little over 50 each, and on the chassis dyno, that's exactly what I got.

peterd · #9 (**permalink**) 12-05-2004, 08:37 AM

I agree that Desktopn DYNO is good for relative changes and not the actual numbers. I am curious why you got low numbers (I would add 15% for transmission loss). What kind of info did you enter for the heads, are you turbo or supercharged?????

Curt C. · #10 (**permalink**) 12-05-2004, 01:27 PM

Interesting. When I plugged my combo in the Destop it generated about 450 HP. I was happy with this because the motor actually yielded 377 RWHP representing a 16% loss for the driveline. Seems to be in line with most estimates of drivetrain losses.

Hotfingrs · #11 (**permalink**) 12-05-2004, 03:19 PM

Pete,
No turbo or supercharged. I don't have the program on this puter, but it was big valve, but not full race...the one below it.

Dwight · #12 (**permalink**) 12-05-2004, 08:39 PM

PETERD
PLEASE TELL ME ABOUT YOUR EFI FOR THE 408. I'M VERY INTERESTED IN THIS SETUP. INJECTORS, HEADS, MASS AIR, ECT.

THANKS DWIGHT

RICK LAKE · #13 (**permalink**) 12-06-2004, 04:18 AM

PeterD The chassic dyno I went to is setup for the motor output not the rwHP and tork. 9.2 compression with a 500" lift cam and a set of CNC ports in by shelby heads. This is why there have been wars on the CC about some of the BS numbers that get posted. I think they are mostly crank numbers not rear wheels. There comes the trouble now

I never said my car was rear wheels. I run 12.5 in the 1/4 mile under idea conditions at E-town, it's a great track. You can figure out the hp from this time. Rick Lake

peterd · #14 (**permalink**) 12-06-2004, 11:37 AM

My EFI is custom built by Force-EFI, I sent them a victor jr manifold and they reworked it. Check out the force-efi website and you can find a picture of my manifold. I use the FAST ECU system and my heads are AFR205's. I use 25lb injectors, roller cam. 9.5 compression ratio.