Slant Six Forum :: 83 D150 Chasis Dyno

Quote:

most dynojet runs will be done in a gear that is closest to a one to one ratio with the engine speed, using say first gear can be manipulated into a false higher TQ reading .

It doesn't matter what gear you run in on load cell style dynos as they are measuring force, not acceleration. Force does not change from gear to gear.

Your last statement seems to contradict your first. From my study of levers it seems as if changing gears is like changing lever ratios, which does change the mechanical advantage the force(engine torque) has over the resistance (dyno drum). Why does the drum not feel this as multiplying the force? I understand that I do not really have to understand this. It works whether I get it or not. This is just pure intellectual curiosity.

Sam

Author:	DadTruck [ Mon Jul 14, 2014 2:52 pm ]
Post subject:	83 D150 Chasis Dyno
when doing the engine planning for the 83 D150 I relied a lot on information gleaned from this forum, and also Dyno Sim to organize the build parameters for analysis. To see how it all actually came together I ran the 83 D150 on a chassis dyno at Cozzolino Motor Sports. The owner, Pete C, admitted that this was the first slant six that he had on his dyno.. http://www.cozzolinomotorsports.com/ here is a chart showing torque and hp. For comparison, I penciled in the stock engine numbers derived from Dyno Sim https://www.flickr.com/photos/13718356@N02/14469478150/ Max HP at the wheel,, 133.7 @4000 RPM Max Torque at the wheel,, 210.3 @2625 RPM https://www.youtube.com/watch?v=k7EKTORC0QM along the right side of the display are readings from Pete C's certified A/F sensor, the NOS 2280 is not letting the mix get lean. here is the second run about identical to the first https://www.youtube.com/watch?v=qdyJHORhQoI Dyno Sim had predicted 138 @ 4000 for HP 215 @ 3000 for Torque I used actual port flow data, that had a lot to do with getting the computer simulation right not bad numbers for an engine running 8.5 static 8.2 dynamic 160 + cranking pressure on regular gas and 20+ highway mpg I asked if there were any signs of detonation on the chart. Pete said if there was detonation, it would show on the chart as sudden dips in the readings. He said the repeating waves in this chart are due to drive line harmonics and heavy stock truck tires,, said if I put on a set of drag slicks the waves would flatten. He also offered, to get to HP at the crank add 25 to 30 to the rear wheel numbers,, that gets me in the 160 HP neighborhood.

Author:	Sam Powell [ Mon Jul 14, 2014 3:37 pm ]
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Wow! Thanks. I will have to read your build sheet again. I really appreciate your sharing this. Several questions: 1 .Is there a single thing that you think improved the engine the most over stock? I seem to recall you thought head work was the biggest thing. If I recall you moved up to a larger carb, so maybe those two things together; induction in general. 2. When they do the dyno run what gear is it in? How can they test rear wheel HP without the gearing effecting the numbers? Thanks again. Sam

Author:	DadTruck [ Mon Jul 14, 2014 4:01 pm ]
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for how a dyno works http://www.ehow.com/how-does_5183355_dyno-work_.html as far as the motor in the 83 D150,, I am happy that the engine performs as it should, it is a bit edgy, but very streetable and something I can live with on a MPG basis. concerning the changes, raising compression and the cam change probably had the greatest impact, but getting the ignition and port flow - machining right can't be discounted.

Author:	Dart270 [ Mon Jul 14, 2014 6:59 pm ]
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Very nice results, John! That is quite respectable for such a mild motor. A well balanced package... Someday I need to dyno a car (or more than one). I think I will get data overload. Look forward to seeing you and the D150 in action this Friday! Lou

Author:	wvenable [ Mon Jul 14, 2014 7:39 pm ]
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During the first youtube vid, there is a brief cameo appearance by a very handsome guy.

Slant Six Forum https://slantsix.org/forum/

83 D150 Chasis Dyno https://slantsix.org/forum/viewtopic.php?t=55796	Page 1 of 2

Author:	slantzilla [ Tue Jul 15, 2014 3:38 pm ]
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Pretty good numbers for a fairly stock motor John.

Author:	Sam Powell [ Tue Jul 15, 2014 3:55 pm ]
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What gear was your truck in on the dyno? Did they wait for to shift into high gear? If so, what keeps it from down shifting? I read the link and did not see the answer to this, so now feel dumb whether I ask again or not. So here goes. They say the only dumb question is the one you don't ask. Thanks. Sam

Author:	DadTruck [ Tue Jul 15, 2014 8:02 pm ]
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Quote: What gear was your truck in on the dyno my truck is a stick, so it probably was in second or third, but to really answer your question,, the transmisson gear that is selected and ultimately how fast the rear tires spin, has little to do with determining engine torque. the car you drive and the truck that I drive needs multiple "gears' to be able to launch it from a stop, mainly due to the weight of the vehicle. If your Dart weighted nothing, you could easliy launch it from a dead stop and progress to top engine speed (max RPM) in a single gear. When a vehicle is on a chassis dyno, the engine propels the drive train forward, but the engine sees no vehicle weight. The engine does see drive train and rear tire rolling resistance (friction), that is why power at the wheel is less than power at the crank or flywheel. but basically any gear will give the same aceleration rate, you would not use the highest gear at max RPM, unless you had quality speed rated tires. For example my truck runs about 70 mph at 2200 rpm in 4th,, spin the engine up to 4500 in 4th, the rear tires will see 140+,, What the chassis dyno does to calculate torque is, the mass and rolling resistance of the drum under the vehicle drive wheels is known. The program measures the rate of change ( acceleration) of the drum. Knowing how fast the drum is accelerating moment by moment and knowing the mass of the drum, one can then calculate how much force (torque) it takes to do that. If the engine torque curve was flat, say from 1000 to 5000 RPM,, what that means is as the drum acelerated with the engine speed, the aceleration was at a constant rate. Conversely, where you see the peak torque on a chart, it is saying that the rate of aceleration was highest at that point.

Author:	Sam Powell [ Wed Jul 16, 2014 4:27 am ]
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Thanks. That is pretty clear. I am still studying the chart of the dyno run. It is very revealing. The more I study it the more I understand the nature of your engine. Very interesting. Sam

Author:	moparmatt441 [ Wed Jul 16, 2014 6:40 am ]
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most dynojet runs will be done in a gear that is closest to a one to one ratio with the engine speed, using say first gear can be manipulated into a false higher TQ reading as it is easier for the engine to get the drum spinning were as an overdrive top gear would do the opposite and would kill tq even thought the speed of the drum would be higher. So if this truck were a three speed manual with 4th as an over drive , second gear would read higher tq than third and third would read higher than 4th. the reason for the dyno in the 1:1 gear ratio is due to the Dynojet. Dynojet mathematically creates a horsepower number based on mass (which is the known weight of the rollers) and acceleration (how fast the car is accelerating the known weight). F=ma From force (F), we can calculate horsepower. Dyno the car in 2nd gear, and acceleration (a) goes way up, causing force (F) to go way up. So by dynoing the car in the gear closest to the 1:1 gear ratio, we eliminate any acceleration advantage or disadvantage caused by the transmission, which gives us unskewed whp numbers (even though Dynojet has a fudge factor in there which makes them skewed anyways and read high). As for other dynos out there (i.e. Mustang and Dyno Dynamics) - they use a load cell to measure roll force (the amount of force the tire is placing on the roller). Based on roll force and the radius arm going to the load cell, we get roll torque. Based on roll torque and roll speed, we can get vehicle horsepower. Vehicle horsepower and vehicle RPM gives vehicle torque. It doesn't matter what gear you run in on load cell style dynos as they are measuring force, not acceleration. Force does not change from gear to gear.

Author:	Sam Powell [ Wed Jul 16, 2014 2:33 pm ]
Post subject:
Quote: most dynojet runs will be done in a gear that is closest to a one to one ratio with the engine speed, using say first gear can be manipulated into a false higher TQ reading . It doesn't matter what gear you run in on load cell style dynos as they are measuring force, not acceleration. Force does not change from gear to gear. Your last statement seems to contradict your first. From my study of levers it seems as if changing gears is like changing lever ratios, which does change the mechanical advantage the force(engine torque) has over the resistance (dyno drum). Why does the drum not feel this as multiplying the force? I understand that I do not really have to understand this. It works whether I get it or not. This is just pure intellectual curiosity. Sam

Author:	DadTruck [ Wed Jul 16, 2014 3:04 pm ]
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MoparMatt has posted some great info here..he is definately closer to the task of dynos than I. the botom line is there are camps that prefer one chassy dyno system over others, and engine dyno folks that look at any chassis dyno with crossed eyes.. My intent of this post is to point out that the chassis dyno is an affordable tuning tool. And in this case provided results that were very simular to a computer dyno sim program. Is it accurate down to a fly speck,, heck no. I expected that, temperature, humidity, grade of gas can influence the results 10%. Do the charts present on paper an accurate representation of the power curve when driving the truck,, absolutely. Does it give me a base line to test other changes against, on the same dyno, yes,,

Author:	slantzilla [ Wed Jul 16, 2014 3:30 pm ]
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John hit it square on the head, a dyno is a tuning tool. The numbers are at the mercy of way to many variables.

Author:	moparmatt441 [ Wed Jul 16, 2014 8:03 pm ]
Post subject:
Quote: Quote: most dynojet runs will be done in a gear that is closest to a one to one ratio with the engine speed, using say first gear can be manipulated into a false higher TQ reading . It doesn't matter what gear you run in on load cell style dynos as they are measuring force, not acceleration. Force does not change from gear to gear. Your last statement seems to contradict your first. From my study of levers it seems as if changing gears is like changing lever ratios, which does change the mechanical advantage the force(engine torque) has over the resistance (dyno drum). Why does the drum not feel this as multiplying the force? I understand that I do not really have to understand this. It works whether I get it or not. This is just pure intellectual curiosity. Sam Not really conflicting the point, just trying to explain there are two different types of dynos. Also agree they are a good tool for setup and tuning but too many differences to compare one reading from one dyno to another.

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Author:	emsvitil [ Wed Jul 16, 2014 9:49 pm ]
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The accelerate the drum type dynos will read a little higher, the higher the gear you use........ The dyno knows the mass and properties of the drum, but does not know the mass and mass distribution of: the engine the flywheel the transmission the driveshaft the axles the wheels and tires. Accelerating the drum isn't linear. Doubling the gear ratio, doesn't double the acceleration of the drum. So the higher the gear you use, the less the effect of the unknown mass has on the calculations.