Dyno time

See section 8 for info that addresses why use 1:1.
https://kennebell.net/tech/tuning-t...ir-fuel-ratio-readings-the-pitfalls-problems/

 

Naw man, I recognize what you're asking. I'm just not sure how to articulate what I'm trying to convey.

So, after reading this I've learned how many variables that influence a dyno run.

So I guess that doing a run in a ratio other than 1:1 could be done, but that would just be adding yet another variable. Sure, it could probably be "compensated" for, but it could only be an "educated guess". Ya, there's also probably a "formula", but that still kinda muddies the water further. Using a 1:1 (or which ever one is closest) ratio helps to create a "standard" operating procedure for the scientific method. When trying to reproduce or compare results, having as many variables as possible the same gives insight into which other, less controllable variables, give different results. If you were to do your run in 3rd gear, in a sense your results will only really be valid to compare to a different truck that also did a run in 3rd, or your own truck. That wouldn't even take into consideration your different final drive and tire size. You and I could compare dyno run, but you have different tires, pulley (I think), final drive and intake. I have stock tire size, final drive ratio, and air box. That would skew any attempts at comparison between mine and others, and would only really be valid to runs made with your truck and they would also need to be made in 3rd gear to be truly valid.

I likely wandered somewhat off track here, lol, but are we getting closer to answering your query? Standardization. Oh, thought of another reference. Maybe you've heard about the story some years ago where we sent a probe to Mars. Things went awry when they tried to land it because some of the scientists were using our U.S. system, and others were using the metric system and the project was lost. Imagine the disaster you would have on your hands if you moved back and forth between S.A.E. and metric on your buggy build? Alright, I think I may be wandering again...

 

Hmmm but wouldn't the fact I'm on 5.29s also has an affect on the read out?

 

Yes, and the most valid comparison would be to other dyno runs of trucks with the same final drive ratio. I think @snivilous has 5.29s as well. The final numbers would need to be "adjusted" when comparing to a truck with the stock 4.3s. Different tire sized would need to be taken into consideration too.

 

Obviously you want to be consistent with runs for tuning, so in that regard it sounds like it doesn't matter what gear you make a pull in. It would actually seem preferable to NOT run in 4th if you have to go through the special procedure that dirty deeds says. Do a pull in 1st, tweak, repeat pull in 1st (or whatever gear). But if you want to show peak power then 4th is best since it's effectively (I assume) a direct drive--i don't know much about transmissions but I assume there's no gear passes happening in 4th which is where the power loss that article is talking about would happen.

 

Yes and no, your engine power would need to be compensated by the efficiency changes of the different gearing but your actual power at the tire would still be an accurate measurement.

If you want engine power you need to try and match everything downstream, but if you're just measuring at the tire then nothing matters up stream. I think that's some of the confusion, if you're trying to extrapolate the engine there's a lot of variables. There's no variables at the tire since that's directly what the Dyno is reading and frankly the number that is actually dictating the trucks performance. Correct me if I'm wrong.

 

If the procedure suggested were not implemented in 3rd you'd still have the potential problem of a 3-2 downshift if you didn't ease into it up to a particular RPM. That may be a different RPM due to the different ratio and transmission tuning. Doing pulls as close to 1:1 is as direct a measurement of engine performance without removing it from the vehicle. Tune the engine for best use case (power/torque) and then use the transmission for terrain variations. You could tune the engine for a 1st gear pull, but that will likely make it suck in other gears. Tune those gears and it messes it up for the others (can you imagine applying this to LO range?). So tune for best engine performance with minimal driveline influence then use the transmission for placing the engine in that performance window over varying terrain. That's kind of the rationale for a transmission, keeping the engine in the sweet spot.

The dyno it trying to measure engine performance/efficiency via the driveline, every component between the two will influence that. Like on a torque wrench, every item between the head of the wrench and the fastener is going to alter that measurement. Like putting a cheater extension on a breaker bar, it alters the effort you need to exert via mechanical leverage; a ratio other than 1:1 does the same. Imagine the inverse when "choking up" on a baseball bat, or the breaker bar.

One of these times, I'll hit on something that'll "click", and it will fall into place.

 

Paging @mech_engineer09

 

Have you guys ever wondered how I can get the transmission to stay in 4th without downshifting on the dyno?
Look at my dyno runs, they are all done in 4th from 2500 RPM.
Yes, it is possible and quite easy to keep the trans in 4th from 1000 rpm to redline without downshifting or upshifting without a tuner of any type
https://www.youtube.com/watch?v=BBI2qosLjhs&t

 

I couldn’t have said it any better. All we are trying to do is eliminate as many variables as possible.

 

I need some schooling sir!! How?

 

I can't get back in time for dyno session, so that has to be delayed.

I tried the ABSII fuse trick, only to have thunderstorm for last couple of days.

In the mean time, here's my racelogic box logging 0-100km/h (62mph), this was done in 2wd, no brake torque launch, just stop from dead stop then mash the gas pedal.

Iroinically, 7.58s was done when my pedal monster was set to stock.

 

Should pull 3 times each, maybe tire is cold on first run with PM, tire lose some grip