540 Chassis Dyno results.....
07-29-2001, 08:31 PM
#1
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Well. I finally got around to Chassis Dyno testing the 540 to see how it compared to the engine dyno session I did previously. Thanks to a great turnout from Forum members we had a great day at MTI in Houston.
Here's the CNN version results;
TQ HP
3500 492.5 328.2
4600 586.5 513.7 (peak TQ)
5000 520.3 495.3 (Tire spin!!)
5500 491.0 514.1
6000 459.7 525.2 (peak HP)
6500 402.4 498.0
7000 347.3 462.9
7500 303.1 432.8 (oops!)
The RPM peaks were identical to the engine dyno tests. It made 702 Hp and 689 ft lbs in that configuration with slightly larger headers, open exhaust and no accessories other than the water pump operating.
We made two passes that were near identical. It was capped up with 39* timing just as I drive it on the street.
The operator let me do the "driving" on the dyno! I'm not sure why but I was the only one to do it. It must have been when he found out I have no rev limiter!! He told me to nod to him when I was ready and to let out when I was done. From the previous tests I knew power fell off after 6500 so I planned to take it only to 6500-6700 or so tops. I also assumed my factory mechanical tach is a little lazy, but now I know how much. With an indicated 6700-6800 rpm it turns out I was spinning 7400-7500!!! Oops!!
I spent time with the operators afterward asking what they typically use for comparison percentages comparing the two types of dynos. They said 12-15% off of "new car specs" will pretty closely match the chassis dyno. For example, most new 345-350 hp Vettes dyno in the 295-300 range. So comparing mine to that I'm in the 600-615 range as installed in the car.
But to compare it to engine dyno testing in the Hot Rod World and the correction factors they use, 18-22% is closer to the number. Especially considering the newer cars use a much more efficient driveline than something like my Doug Nash 5 speed. It's not known for being terribly efficient (but very strong!) So with all that taken into account, it would appear the addition of slightly smaller headers, full closed exhaust, a fixed stainless steel flex fan and alternator account for around 40 HP or so, putting me in the 660 hp (old style numbers) range on the street.
It's interesting to compare the results from the two different types of testing, engine and chassis. The percentage differences climb greatly as RPM increases. Must be the additional restriction of the exhaust and the fan. It's only down 8.6% at 4200 RPM at the wheels compared to open headers etc on the engine dyno. At 6000 RPM it's 25.3% and at 7000 RPM its down to 21.8%. Maybe the fan is finally flattening out up there?
The fun part was talking to folks afterwards. They said smoke blew off the tires when I hit it and then the tires went "egg" shaped! We had to wipe rubber dust off the qtr. panels! As a sidenote they reported the only smoke they saw was a puff of black when I hit it and then clean afterwards. Good news!
Also the point triggered ignition never missed a beat at 7500 RPM either. Also the Holley mechanical pump kept up fine just as it's been doing on the street and track with the old 427.
Talk about "old tech" technology. Lots of cubes, carburetor, points, big heads, big cam etc. etc.
But when it all comes together it sure is fun!!
Next stop..... drag testing!
Here's the CNN version results;
TQ HP
3500 492.5 328.2
4600 586.5 513.7 (peak TQ)
5000 520.3 495.3 (Tire spin!!)
5500 491.0 514.1
6000 459.7 525.2 (peak HP)
6500 402.4 498.0
7000 347.3 462.9
7500 303.1 432.8 (oops!)
The RPM peaks were identical to the engine dyno tests. It made 702 Hp and 689 ft lbs in that configuration with slightly larger headers, open exhaust and no accessories other than the water pump operating.
We made two passes that were near identical. It was capped up with 39* timing just as I drive it on the street.
The operator let me do the "driving" on the dyno! I'm not sure why but I was the only one to do it. It must have been when he found out I have no rev limiter!! He told me to nod to him when I was ready and to let out when I was done. From the previous tests I knew power fell off after 6500 so I planned to take it only to 6500-6700 or so tops. I also assumed my factory mechanical tach is a little lazy, but now I know how much. With an indicated 6700-6800 rpm it turns out I was spinning 7400-7500!!! Oops!!
I spent time with the operators afterward asking what they typically use for comparison percentages comparing the two types of dynos. They said 12-15% off of "new car specs" will pretty closely match the chassis dyno. For example, most new 345-350 hp Vettes dyno in the 295-300 range. So comparing mine to that I'm in the 600-615 range as installed in the car.
But to compare it to engine dyno testing in the Hot Rod World and the correction factors they use, 18-22% is closer to the number. Especially considering the newer cars use a much more efficient driveline than something like my Doug Nash 5 speed. It's not known for being terribly efficient (but very strong!) So with all that taken into account, it would appear the addition of slightly smaller headers, full closed exhaust, a fixed stainless steel flex fan and alternator account for around 40 HP or so, putting me in the 660 hp (old style numbers) range on the street.
It's interesting to compare the results from the two different types of testing, engine and chassis. The percentage differences climb greatly as RPM increases. Must be the additional restriction of the exhaust and the fan. It's only down 8.6% at 4200 RPM at the wheels compared to open headers etc on the engine dyno. At 6000 RPM it's 25.3% and at 7000 RPM its down to 21.8%. Maybe the fan is finally flattening out up there?
The fun part was talking to folks afterwards. They said smoke blew off the tires when I hit it and then the tires went "egg" shaped! We had to wipe rubber dust off the qtr. panels! As a sidenote they reported the only smoke they saw was a puff of black when I hit it and then clean afterwards. Good news!
Also the point triggered ignition never missed a beat at 7500 RPM either. Also the Holley mechanical pump kept up fine just as it's been doing on the street and track with the old 427.
Talk about "old tech" technology. Lots of cubes, carburetor, points, big heads, big cam etc. etc.
But when it all comes together it sure is fun!!
Next stop..... drag testing!
07-29-2001, 09:53 PM
#3
Burning Brakes
Jim,
Those are some impressive numbers!
Can't wait to see how this translates to 1/4 mile MPH. W/o slicks, I wouldn't even hazard a guess at ET!!
I got your note, thanks. You have mail.
Take care,
Mark
Those are some impressive numbers!
Can't wait to see how this translates to 1/4 mile MPH. W/o slicks, I wouldn't even hazard a guess at ET!!
I got your note, thanks. You have mail.
Take care,
Mark
07-29-2001, 09:59 PM
#4
Burning Brakes
So when do you change your username to 540Hotrod? 
07-30-2001, 02:09 AM
#5
Drifting
Awsome power,congrats!
Can you tell me what kind of clutch you are useing? does it hold on ? easy to drive around?
thanks !
Can you tell me what kind of clutch you are useing? does it hold on ? easy to drive around?
thanks !
07-30-2001, 11:08 PM
#6
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2020 C2 of the Year - Modified Winner
2020 Corvette of the Year (performance mods)
C2 of Year Winner (performance mods) 2019
2017 C2 of Year Finalist
It's got a Centerforce 11" dual friction. It works great and holds fine. Lot's less pedal effort than the old hays I was using.
It'll hold just about anything I've seen that's streetable. I've had it over three years in there and launching on slicks with no problems.
Jim
It'll hold just about anything I've seen that's streetable. I've had it over three years in there and launching on slicks with no problems.
Jim