How does weight used effect Dyno results???
Thread Starter
Melting Slicks
Joined: Oct 2000
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From: Heidelberg PA
Cruise-In V Veteran
How does weight used effect Dyno results???
Just wondering how weight can effect a Dyno.
If the weight of the vehicle is inputted at 3500lbs when the stats/factory has 3088lbs we are talking about a 15% variance.
Any assistance would be helpful.
Jim C
If the weight of the vehicle is inputted at 3500lbs when the stats/factory has 3088lbs we are talking about a 15% variance.
Any assistance would be helpful.
Jim C
Melting Slicks
Joined: Aug 2001
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Re: How does weight used effect Dyno results??? (85vet)
Yep, rolling resistance will definitely effect the outcome... if there are two totally equal cars (this being impossible) and one has the tires inflated to max streetable pressure and the other has the tires at 15psi.. which car is gonna roll and accelerate the drums faster? The car that rotates the drum quicker within the same given time, show the higher ratings. This being true, if you fudge the weight of the car, the same should be true. I'm not sure if you're talking Dynojet or other, but there's gotta be an algorithm in the software that places all things equal provided the user inputs the data correctly.
Thread Starter
Melting Slicks
Joined: Oct 2000
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From: Heidelberg PA
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Re: (scorp508)
The weight was part of the dynos database. It was printed out with the stats.
It shows 3500lbs and I looked into the stats and they say 3088lbs.
It shows 3500lbs and I looked into the stats and they say 3088lbs.
Team Owner
Joined: Mar 2000
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From: Boston, MA
Re: (85vet)
It shows 3500lbs and I looked into the stats and they say 3088lbs.
Melting Slicks
Joined: Nov 2000
Posts: 2,469
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From: Winchester Ontario
Re: (85vet)
When the dyno guy asked me for the weight, I asked him how close I had to be. He said well about 50 pounds give or take. So, I told him that I found that my car weighed 3238 on a web page, so that's the info he entered. I was wondering the same thing myself.
Melting Slicks
Joined: Mar 2001
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From: Timra, Sweden
Re: How does weight used effect Dyno results??? (85vet)
I can't see how the weight of the car could possibly affect the dyno hp readings. The car is standing still so the weight does not matter at all.
If they use the dyno data to calculate a 1/4 mile run then the weight is important, but not to get the hp / tourqe numbers.
Next time, do a run with / without a heavy passenger and see if you get different results.
[Modified by JoBy, 1:51 PM 12/3/2001]
If they use the dyno data to calculate a 1/4 mile run then the weight is important, but not to get the hp / tourqe numbers.
Next time, do a run with / without a heavy passenger and see if you get different results.
[Modified by JoBy, 1:51 PM 12/3/2001]
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Thread Starter
Melting Slicks
Joined: Oct 2000
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From: Heidelberg PA
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Re: How does weight used effect Dyno results??? (89vette)
89vette,
Here is the results - Not as good as I hoped.
Miles - 52878
Weight - 3500
HP@50mph - 13.6
Test Run - 12/1/01 2:28:08
Max Power - 198.6 @ 4250 RPM
Max Torque - 275.8 @ 3250 RPM
1/4 mile run
Distance Time Speed
100 Yards 5.884 59.68
200 Yards 8.896 76.579
300 Yards 11.386 85.728
400 Yards 13.617 95.621
60 Feet 2.289 30.26
1/4 Mile 14.451 98.581
Note that I am not power shifting and this can have a effect.
Since the run, I have discovered that my timing was at 2 to 3 degree retarded vs 8 to 10 advanced. I changed the pulleys to undersized and didn't realize it would effect my timing. ( I was too excited about going to the dyno)
And I had a massive intake leak at runner to manifold - Both are corrected and I will be returning to the dyno on Wednesday.
Another question!!!
When you do the power run from 30 miles an hour - what gear should you be in?
I was in 3rd and told to kick it down. In an auto at thirty and you floor it - doesn't the car downshift?
I am wondering if 3rd is the best gear since all my torque is in 1st & 2nd?
:chevy
[Modified by 85vet, 10:08 AM 12/3/2001]
Here is the results - Not as good as I hoped.
Miles - 52878
Weight - 3500
HP@50mph - 13.6
Test Run - 12/1/01 2:28:08
Max Power - 198.6 @ 4250 RPM
Max Torque - 275.8 @ 3250 RPM
1/4 mile run
Distance Time Speed
100 Yards 5.884 59.68
200 Yards 8.896 76.579
300 Yards 11.386 85.728
400 Yards 13.617 95.621
60 Feet 2.289 30.26
1/4 Mile 14.451 98.581
Note that I am not power shifting and this can have a effect.
Since the run, I have discovered that my timing was at 2 to 3 degree retarded vs 8 to 10 advanced. I changed the pulleys to undersized and didn't realize it would effect my timing. ( I was too excited about going to the dyno)
And I had a massive intake leak at runner to manifold - Both are corrected and I will be returning to the dyno on Wednesday.
Another question!!!
When you do the power run from 30 miles an hour - what gear should you be in?
I was in 3rd and told to kick it down. In an auto at thirty and you floor it - doesn't the car downshift?
I am wondering if 3rd is the best gear since all my torque is in 1st & 2nd?
:chevy
[Modified by 85vet, 10:08 AM 12/3/2001]
Melting Slicks
Joined: Aug 2000
Posts: 2,388
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From: Murrysville PA
Re: How does weight used effect Dyno results??? (85vet)
Yes you do the test in third gear for autos. Yes it does downshift and I think thats where you get the torque spike. My car is a six speed and I do the test in 4th gear. I get it up to 2500 RPM and then floor it to 6000. Don't be too overly concerened with the horsepower numbers. Your mods will not give you much if any power over stock. I did see your post about the timing and that will have alot to do with it. Three years ago, I dynoed my car when it had genuine CNC ported heads, Crane Compucam 214/220 durtation .452/.465 lift, ported stock base, ASM large runners, ported plenum, 52mm throttle body, ported MAF, KN filter with open lid, Ed Wright chip, LPE 1 5/8" headers, Random cat, and LT1 mufflers. I thought with all that I should have 300 horsepower. I had 270HP to the wheels and 353TQ. The car was plenty fast and fun. Now I have a 396 with a Super ram and lots of hi dollar parts and I dyno 334HP and 430TQ to the wheels. Most say I should have, about 40 more horsepower. Well maybe so but the car is pretty wicked now and I'm happy. Its starts and drives like a stocker until you nail it and then its all over the road.
As far as shifting, I used to shift at about 4500.
Maybe in the spring we can get together for a dyno day since I am from Pittsburgh also.
Jason
As far as shifting, I used to shift at about 4500.
Maybe in the spring we can get together for a dyno day since I am from Pittsburgh also.
Jason
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,426
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From: Heidelberg PA
Cruise-In V Veteran
Re: How does weight used effect Dyno results??? (89vette)
Thanks,
You made my day :cheers: :cheers:
Keep me in mind in the summer, I had fun and will go whenever cash and time allow.
You made my day :cheers: :cheers:
Keep me in mind in the summer, I had fun and will go whenever cash and time allow.
Safety Car
Joined: Jul 1999
Posts: 3,946
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From: Marianna FL
Re: How does weight used effect Dyno results??? (85vet)
Was this run on a Mustang Dyno or a Dynojet? If it was on a Mustang Dyno and was the true rear wheel numbers (looks like it), then you can expect a dynojet to read about 11% higher--so I've read.
Thread Starter
Melting Slicks
Joined: Oct 2000
Posts: 3,426
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From: Heidelberg PA
Cruise-In V Veteran
Re: How does weight used effect Dyno results??? (Mr Dave)
The dyno was a Mustang (I Know this is a naughty word on this forum)!!
Very Interesting!!!!!!
:chevy
[Modified by 85vet, 1:59 PM 12/3/2001]
Very Interesting!!!!!!
:chevy
[Modified by 85vet, 1:59 PM 12/3/2001]
Race Director
Joined: Sep 2000
Posts: 17,298
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From: The Top of Utah
Re: How does weight used effect Dyno results??? (85vet)
Weight doesn't affect horserpower, and accessory belt pulleys don't affect ignition timing. Since you are starting from a 30 mph roll, the 1/4 mile run, distance, time, speed, numbers must be a calculation that WOULD be affected by weight. Because they are theoretical, they are no substitute for the real thing. The HP and torque numbers are real. For the others, hit the track.
Race Director
Joined: May 2001
Posts: 14,165
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Re: How does weight used effect Dyno results??? (Mr Dave)
Yes, I've seen mustang Dyno's tend to read much lower, but why? I don't think it's because they are more accurate, if anything they are less. A dynojet seems to stack right nicely with the calculated drivetrain loses, going by the factory rated power. The mustangs just tend to be WAY low. I guess with everything mustang, people just thing they are better than they really are :)
Le Mans Master
Joined: Jun 2001
Posts: 9,117
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From: 7th Floor Crew
Re: How does weight used effect Dyno results??? (Nathan Plemons)
Yes, I've seen mustang Dyno's tend to read much lower, but why?
Scott
Racer
Joined: Nov 2000
Posts: 253
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From: battle creek mi
Re: How does weight used effect Dyno results??? (Hurricane_777)
i have a mustang dyno in my garage! try to run part-throttle driveability tests with a dynojet...i need the weight of the car so that the dyno software can add enertia weight..it has a 1000 lb wheel on the side and then it applies current to simulate the rest. i try not to get wrapped up in dyno #'s...id rather drive
:yesnod:
:yesnod:
Thread Starter
Melting Slicks
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From: Heidelberg PA
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Re: How does weight used effect Dyno results??? (CFI-EFI)
CFI-EFI,
The 30 mile start calculation is for HP. The 1/4 mile is from a dead stop and there is resistance simulating track conditions.
I was talking to a friend of mine (mechanic) and he said the same thing about the pulleys not effecting timing. I am stopping to see him tomorrow before I take another run.
Jim C
The 30 mile start calculation is for HP. The 1/4 mile is from a dead stop and there is resistance simulating track conditions.
I was talking to a friend of mine (mechanic) and he said the same thing about the pulleys not effecting timing. I am stopping to see him tomorrow before I take another run.
Jim C