Engine dyno load vs. WOT on the road?

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427dart
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Engine dyno load vs. WOT on the road?

Post by 427dart »

When an engine is tested on an engine dyno how does it compare to same WOT on the street. Is the dyno load like the engine being accelerated in 3rd gear or 4th being 1 to 1 ratio?
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Re: Engine dyno load vs. WOT on the road?

Post by Schurkey »

Isn't the dyno load adjustable, for a certain amount of RPM rise per second?

300 RPM rise per second is going to be different from 600 rpm per second.
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Re: Engine dyno load vs. WOT on the road?

Post by cardo0 »

You won't have the air drag at high road speeds on a Dyno which would affect load. Also you have fresher air for the cooling system - as I'm sure you have watched your temp gauge reading rise in stop and go traffic after getting off the freeway. And the induction system should be breathing cooler/fresher air also - but not all dyno's.
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Re: Engine dyno load vs. WOT on the road?

Post by 427dart »

I was thinking along the lines of accel rate and load compared to flat level stretch of road accel and load in say 2nd gear.
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Re: Engine dyno load vs. WOT on the road?

Post by Brian P »

With a good load-control dyno, you can set those to anything you want.

https://www.youtube.com/watch?v=z87iFASgDwk
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Re: Engine dyno load vs. WOT on the road?

Post by groberts101 »

Brian P wrote: Sat Jul 14, 2018 2:56 pm With a good load-control dyno, you can set those to anything you want.

https://www.youtube.com/watch?v=z87iFASgDwk
Tons of good dyno's and electronics out there but the operators don't always know how to use them or invest the time to take full advantage of them. Plus, most customers get sticker shocked when the find out how much it will actually cost to dial in that last 5% average power gain.

My experience has always been that typical "time slotted dyno tune's" are not real world and rarely are customers cars tuned from a low rpm dig on proper equipment to actually simulate what rpm sweep the engine will actually encounter on the road. Can a pickup truck sweep 600 rpm/sec in 4th gear on the highway? Car truck or otherwise, the ignition timing sweep alone usually leaves much to be desired after a local dyno tune and I always gain manifold vacuum at idle, average power and throttle response which makes the car much funner to drive in the real world.
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Re: Engine dyno load vs. WOT on the road?

Post by Zmechanic »

On the road the acceleration is dependent on the output of the engine. Most water brake dynos are set up to have a constant and fixed acceleration rate.

Velocity is proportional to the square root of energy. And horsepower is energy delivered per unit time. So if you had a constant 1hp engine, even with no air drag, the cars acceleration would slow as it sped up. Air drag just makes this effect even more pronounced and can mean acceleration will stop altogether.

The closest you can get to this is an inertial dyno. If you could apply an increasing static load with rpm it'd be even more realistic. People gave gone to varies lengths to do things like this.

Doesn't mean a fixed acceleration rate isn't useful. But it can lead to some inconsistencies.
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Re: Engine dyno load vs. WOT on the road?

Post by cjperformance »

Schurkey wrote: Sat Jul 14, 2018 1:29 pm Isn't the dyno load adjustable, for a certain amount of RPM rise per second?

300 RPM rise per second is going to be different from 600 rpm per second.
The road rpm rise rate is accounting for every bit of load the engine sees.
If you're at WOT and you match the rpm rise to what you get on the road then you will get an accurate result on the dyno.
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Re: Engine dyno load vs. WOT on the road?

Post by ptuomov »

There are dynos and then there are dynos:

https://youtu.be/mfuleS9rnzc
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
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Re: Engine dyno load vs. WOT on the road?

Post by cjperformance »

ptuomov wrote: Sat Jul 14, 2018 7:47 pm There are dynos and then there are dynos:

https://youtu.be/mfuleS9rnzc
Yes thats awesome.
And although not as tech advanced i really like the 427 Ford on the Le Mans dyno simulator that Walter put up a while back.
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Re: Engine dyno load vs. WOT on the road?

Post by andyf »

Engine acceleration in a car is going to depend on the power to weight ratio. If you really want to know the answer to this question then you would need to use a data logger in the car to see what the engine acceleration rate is. Then when you go to the dyno you can ask the operator to match that acceleration rate. That will be about as close as you can get it without spending a fortune for a dyno with a non-linear acceleration curve.
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Re: Engine dyno load vs. WOT on the road?

Post by user-23911 »

Once you've got a data logger in the car, so long as you've got a safe track, you no longer need a dyno..........within reason of course.

But as said, there's dynos and there's dynos.
A "good" dyno will be able to hold the RPMs steady (no acceleration rate) throughout the total RPM range (from 800 RPM for a truck engine) and the total load range.......as required for emissions testing to SAE spec J ?????
Same as climbing a long hill........should be able to hold it all day long or until you run out of fuel.

https://www.youtube.com/watch?v=n1yxMFuYwHE
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Re: Engine dyno load vs. WOT on the road?

Post by ptuomov »

John Kuhn has been fuel mapping my engine this week. The first step is to create a "primary load map" that would give the engine 14.5 AFR in all steady state conditions. The second is to add a "base fuel map" correction to that injector pulse width that then gives one the actual AFR desired in various steady state conditions (14.5 for most of the map, but as rich as 11.5 at very high loads). The third step is to sweep load (holding rpm) and sweep rpm (holding load) at different rates of change to tune the transient conditions to produce 0-0.5 AFR points richer tune in quickly increasing load or rpm situations. After this procedure, the engine fueling is mapped well enough that one can start maximizing torque in each map cell by changing AFR and ignition timing.

Here's a photo and video:

https://photos.app.goo.gl/jxL1MLAjzTbgD4Zv8

https://photos.app.goo.gl/6tw7C9ZS76GPpw2d6
Paradigms often shift without the clutch -- https://www.youtube.com/watch?v=cxn-LxwsrnU
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Re: Engine dyno load vs. WOT on the road?

Post by Stan Weiss »

This dyno sheet I believe is from the 2011 carb challenge that was run on the BLP inertia dyno. As you can see the RPM/S acceleration rate follows the torque curve.

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Re: Engine dyno load vs. WOT on the road?

Post by Warp Speed »

Stan Weiss wrote: Sat Jul 14, 2018 11:50 pm This dyno sheet I believe is from the 2011 carb challenge that was run on the BLP inertia dyno. As you can see the RPM/S acceleration rate follows the torque curve.

Stan

JMark_BB-2011.gif
I often wonder why didn't that dyno ever take off in the performance industry?

Doing real road simulation, an AVL will simulate any condition it's programmed for. Just need throttle position and rpm trace data.
As mentioned, you can use a typical water break, and test at various acceleration rates and throttle positions, and get pretty close to ideal.
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