Dyno and new #s
07-11-2005, 03:23 PM
#1
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Dyno and new #s I have a few questions for all the experienced dyno people here (mods in sig).
I had my car dynoed in March this year with an end dyno of:
318.4 RWHP at 5700 RPM
322.0 RWTQ at 4900 RPM
I do not know the A/F and it was on a Mustang Dyno with SAE.
The difference between this run and the one I had last Friday was a different shop, different Mustang Dyno, and I replaced the Mac Cats for some ThunderBolt cats.
The results from Friday:
340.7 RWHP at 6050 RPM
331.2 RWTQ at 4800 RPM
This was on a Mustang Dyno with SAE and A/F of 13.0.
Questions:
1. Could a Thunderbolt Cat switch from Mac Cat cause that much of an increase in HP and TQ (22.3 RWHP and 9.2 RWTQ)?
2. How much of a difference could be from 2 different shops with their own Mustang Dynos?
3. Last, I switched from 3.23 gears to 3.73 gears and would like to know what difference I might see when I have it dynoed in 2 weeks at the same shop I went to this last Friday?
I had my car dynoed in March this year with an end dyno of:
318.4 RWHP at 5700 RPM
322.0 RWTQ at 4900 RPM
I do not know the A/F and it was on a Mustang Dyno with SAE.
The difference between this run and the one I had last Friday was a different shop, different Mustang Dyno, and I replaced the Mac Cats for some ThunderBolt cats.
The results from Friday:
340.7 RWHP at 6050 RPM
331.2 RWTQ at 4800 RPM
This was on a Mustang Dyno with SAE and A/F of 13.0.
Questions:
1. Could a Thunderbolt Cat switch from Mac Cat cause that much of an increase in HP and TQ (22.3 RWHP and 9.2 RWTQ)?
2. How much of a difference could be from 2 different shops with their own Mustang Dynos?
3. Last, I switched from 3.23 gears to 3.73 gears and would like to know what difference I might see when I have it dynoed in 2 weeks at the same shop I went to this last Friday?
07-14-2005, 05:02 PM
#3
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OK...
I guess those are unanswerable? OR! Maybe, it is an ancient dyno secret.
J/K
Well let me pose another question to the 'Dyno Gods':
why do I see dynos that are SAE and have widely varying TQ?
Ex: Car 1 has 340 RWHP and 375 RWTQ. Car 2 (with similiar setup and tune at different shop) gets 342 RWHP and 333 RWTQ.
Question: why is one RWTQ much higher and the other is much lower and both are similiar RWHP and setup.
I guess those are unanswerable? OR! Maybe, it is an ancient dyno secret.
J/K
Well let me pose another question to the 'Dyno Gods':
why do I see dynos that are SAE and have widely varying TQ?
Ex: Car 1 has 340 RWHP and 375 RWTQ. Car 2 (with similiar setup and tune at different shop) gets 342 RWHP and 333 RWTQ.
Question: why is one RWTQ much higher and the other is much lower and both are similiar RWHP and setup.
07-16-2005, 11:49 PM
#4
SAE number you are talking about is just the correction for weather conditions and has nothing to do with the dyno testing method such as acceleration rate, loaded or inertia test, steady state, etc. The different testing method is why you will get different numbers from the same vehicle or similiar setup and tune. It is really funny how everybody is hell bent on sae or std correction but no one gives a damn about the actual test method.
To put it another way, your vehicle does not make a set HP and TQ number at the wheels and you just go test it and see what it is by doing an accelleration pull because the rate at which you measure it affects your result. This is also true with an engine dyno. If we would use a SAE, STD or just a universally agreed upon test method we would eliminate alot of the varying numbers.
Use the dyno as a before and after test to compare modifications and use the same dyno and the same accelleration rate, etc as your baseline test. Tires, air pressure, weather conditons, engine temp, accelleration rate.....all effect the outcome of the test. The more conditions you can control and duplicate each run, the better your results will be.
Better results meaning accurate, NOT just higher numbers.
To put it another way, your vehicle does not make a set HP and TQ number at the wheels and you just go test it and see what it is by doing an accelleration pull because the rate at which you measure it affects your result. This is also true with an engine dyno. If we would use a SAE, STD or just a universally agreed upon test method we would eliminate alot of the varying numbers.
Use the dyno as a before and after test to compare modifications and use the same dyno and the same accelleration rate, etc as your baseline test. Tires, air pressure, weather conditons, engine temp, accelleration rate.....all effect the outcome of the test. The more conditions you can control and duplicate each run, the better your results will be.
Better results meaning accurate, NOT just higher numbers.
Originally Posted by ActionJack
OK...
I guess those are unanswerable? OR! Maybe, it is an ancient dyno secret.
J/K
Well let me pose another question to the 'Dyno Gods':
why do I see dynos that are SAE and have widely varying TQ?
Ex: Car 1 has 340 RWHP and 375 RWTQ. Car 2 (with similiar setup and tune at different shop) gets 342 RWHP and 333 RWTQ.
Question: why is one RWTQ much higher and the other is much lower and both are similiar RWHP and setup.
I guess those are unanswerable? OR! Maybe, it is an ancient dyno secret.
J/K
Well let me pose another question to the 'Dyno Gods':
why do I see dynos that are SAE and have widely varying TQ?
Ex: Car 1 has 340 RWHP and 375 RWTQ. Car 2 (with similiar setup and tune at different shop) gets 342 RWHP and 333 RWTQ.
Question: why is one RWTQ much higher and the other is much lower and both are similiar RWHP and setup.
07-18-2005, 01:00 PM
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Originally Posted by DynoDR
SAE number you are talking about is just the correction for weather conditions and has nothing to do with the dyno testing method such as acceleration rate, loaded or inertia test, steady state, etc. The different testing method is why you will get different numbers from the same vehicle or similiar setup and tune. It is really funny how everybody is hell bent on sae or std correction but no one gives a damn about the actual test method.
To put it another way, your vehicle does not make a set HP and TQ number at the wheels and you just go test it and see what it is by doing an accelleration pull because the rate at which you measure it affects your result. This is also true with an engine dyno. If we would use a SAE, STD or just a universally agreed upon test method we would eliminate alot of the varying numbers.
Use the dyno as a before and after test to compare modifications and use the same dyno and the same accelleration rate, etc as your baseline test. Tires, air pressure, weather conditons, engine temp, accelleration rate.....all effect the outcome of the test. The more conditions you can control and duplicate each run, the better your results will be.
Better results meaning accurate, NOT just higher numbers.
To put it another way, your vehicle does not make a set HP and TQ number at the wheels and you just go test it and see what it is by doing an accelleration pull because the rate at which you measure it affects your result. This is also true with an engine dyno. If we would use a SAE, STD or just a universally agreed upon test method we would eliminate alot of the varying numbers.
Use the dyno as a before and after test to compare modifications and use the same dyno and the same accelleration rate, etc as your baseline test. Tires, air pressure, weather conditons, engine temp, accelleration rate.....all effect the outcome of the test. The more conditions you can control and duplicate each run, the better your results will be.
Better results meaning accurate, NOT just higher numbers.
Thanks for responding to my post since I was getting frustrated with no response being given.
Your answer seems to only verify what I had assumed to be the case. That different dynos and different conditions will supply varying results. That it is best to use the same dyno and varying conditions to try to get the best measurement of chages to a car.
So, when I go to get my cats removed and have a Y pipe fabricated I should do a before and after dyno with the emgine cool at both runs to give me the best indication of any true gains and to keep in mind that the final HP and TQ #s will vary slightly for any car with different conditions even with the exact same setup.
thanks for responding yet again...
07-18-2005, 07:56 PM
#6
Originally Posted by ActionJack
Thanks for responding to my post since I was getting frustrated with no response being given.
If you can do the before and after pulls on the same day, closer weather conditions, that will help take one varible out of the process.
I would probably do a couple pulls back to back, let it cool for 10-15 min and do another pull before I removed the cats. Then after you have your exhaust done, do the same thing. Key things like starting each run at the same coolant temp or oil temp, same tire pressure are again very important to getting an accurate comparison. Have the same dyno operator, let the same person strap it down. All of these little things will really tighten up your results.
