Low end Dyno graphs
No low RPM data recorded. Why? Why isn't low rpm data recorded during dyno sessions for manual transmission cars. Basically in a manual you can do this from idle to redline, and in an auto anything under the stall speed is useless. From what I've researched, idle-3000rpm is usually missing? Why is this when most cars run under 3000 rpm on the street?
Last edited by squealingtires; Feb 8, 2007 at 10:41 AM. Reason: clarification
I have always figured that usually the cams people put in their cars don't really pick up till 3k, so it would be kinda worthless to show what you may have lost (or stayed even) down low. I could be wrong though. I've wondered the same.
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Joined: Jun 2005
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From: Was New Orleans, but swam to Baton Rouge
Most dyno tuning is done for wide open throttle. You do not need to look at the low side for any of that. Most daily driving the O2 sensors will determine fuel and timing and the load is minimal on an engine. When you have a cam most people start where the cam pulls and go to look at the wide open throttle performance and air fuel.
If you were to try this you will see why it is not done. The next time you are riding around, put a manual vehicle in 4th gear, slow down to about 1000 rpm and then try to accelerate.
And I am guessing that you are talking Hp/tq and afr numbers when you refer to "data".
And I am guessing that you are talking Hp/tq and afr numbers when you refer to "data".
Originally Posted by vader99
So no one worries about everyday normal driving results anymore, just the top 2000 rpm's? LOL
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Originally Posted by ArcticZ28
It can obviously be done, just would be harder on a load-bearing dyno.
Originally Posted by DynoDR
You can turn the absorber off on a load bearing dyno and you still have alot of drum weight to accelerate. What you end up with is such a high load at those low rpm's any data you gather is pretty much useless anyway.
As long as the dynoing is all the same and on the same car with near the same conditions, at least you would be able to see the loss/gain of the cam you just put in compared to your previous one when comparing the bottom end. A loss in low rpm torque will still be evident and I would imagine some of these bigger cams would surprise most people on how much you actually lose on the bottom end compared to stock or a smaller cam.
If your car is a track *****, then disregard this argument. But most people still drive their's on the street and some like bottom-end torque still.
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Joined: Sep 2004
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From: Omaha, NE
Originally Posted by squealingtires
Why isn't low rpm data recorded during dyno sessions for manual transmission cars. Basically in a manual you can do this from idle to redline, and in an auto anything under the stall speed is useless. From what I've researched, idle-3000rpm is usually missing? Why is this when most cars run under 3000 rpm on the street?
Is there a better way of characterizing an engine performance characteristics down low? How about a near zero load on the engine (rear axle lifted up) could be dangerous if the car fell or something. If some test wheels (known rotational inertia) could be mounted and rotational speed measured with respect to time, then the torque could be calculated. I dunno
