see if its a dynojet and weather or not we can get a file.Originally Posted by NOLAjeeper
Id like to check the conditions vs the chart line to get to the bottom of weather or not Jesse's dyno is "off".
see if its a dynojet and weather or not we can get a file.
Id like to check the conditions vs the chart line to get to the bottom of weather or not Jesse's dyno is "off".
I think the 4.88 gears on Jesse's Girl could have significantly affected the dyno results, especially because it was run with stock 32" tires, and because of the nature of how a turbo works.
The overall gear ratio of 4th gear on that setup is close to 3rd gear with 3.73 gears, and is like something between 2nd and 3rd gear with 3.21 gears. This means that Jesse's Girl did not have as much load on the engine when run on the dyno as compared to Prodigy's dyno runs. This would lead to lower dyno numbers for 2 reasons:
1) The already-discussed issue of quicker acceleration on the dyno leading to lower dyno numbers because more torque is lost to accelerating the drive train more quickly.
2) Less load on the engine and quicker acceleration causes the turbo to spool up more slowly with respect to engine speed, so boost increases "later" in the rpm range, resulting in a lower peak torque that occurs higher up in the rpm range.
Additionally, common dyno practice is to use the transmission gear that is closest to a 1:1 ratio. 5th gear is a 1:1 ratio on the Wrangler, so it's possible that Prodigy's results are from a 5th gear dyno pull, meaning that Prodigy's dyno pull had even that much more load on the engine for slower acceleration, allowing the turbo to spool up at lower rpms, and giving up less torque to accelerating the drive train.
To get as close to Prodigy's conditions as possible, we need to find out what transmission gear they used for the dyno pull, then run Jesse's Girl one gear higher with stock tires. Even at one gear higher, Jesse's Girl will still be geared overall a little shorter (numerically higher), plus the driveshaft will be accelerating more quickly than the stock jeep (using up some of the torque), so I would still expect the numbers to be a bit lower than Prodigy's results.
I have never heard of a 5th gear dyno.
Ive also been told by separate people that the gearing doesnt matter with a tumbler style dyno machine.
Im not an expert, these points, I have heard from different people. The power comes thru the drive train, and the rear wheels roll the tumbler. The tumbler dosent know what the gearing is, and im not sure the number of teeth in the ring alters the power from the driveshaft thru the wheels.
Maybe I can get someone from dynojet to tell us exactly.
The math might work out so that it doesn't really matter for N/A or supercharged engines, where there is a direct relationship between engine speed and torque output. But we're talking about a turbocharged engine here. It takes engine load and time to spool up a turbo. Just compare a 3rd and 4th gear run from Jesse's girl and you'll see how much of a difference the overall gear ratio can make.
Jeff: to be honest I don't believe in dynos what I believe is personal experience so my question is what do you feel about the gain and did u got what expected from the kit. Same questions to others (impression). I already ordered the kit (still waiting) but once I installed I will try to compare it with other cars plus other upgraded JK if possible. Gears affect how quick is your car , but in major view it dosent affect the overall performance.
My butt dyno says Jesse's Girl is a rocket. But the 4.88s play into that. Did she feel fast? Yes. Was I going fast?... not as fast as it felt. I was merging onto a highway and I had the throttle nailed. It felt like I was on a roller coaster. But I was not blowing away traffic. Thats because the gearing was holding the overall speed back. (I think).
So is she fast? Yes, very fast.
Would she be faster with 4.10s? If we are talking about highway speeds, then yes. But the acceleration would suffer, and she might not feel as fast.
My personal experience is all subjective, so it's not a valid basis for comparison. Butt dynos are much less trustworthy than real dynos. Starting around 3000 rpm, it goes fast, makes cool noises, and makes me smile. How fast is fast? Faster than stock is all I can tell you. Is it faster than RIPP or Magnuson? I have no idea. I haven't even seen one of their kits in person. Is it fast enough to make you smile? I wouldn't know.
That's why we use tools (dynos) to measure objective representations of performance (torque/power curves). If the tools are standardized and used consistently, then you get consistent and comparable results. We have seen inconsistent results at this point and are trying to figure out the cause inconsistency so it can be corrected to ensure that we have results that are consistent and comparable to other dyno results (stock, RIPP and Magnuson).
Hope you get a chance to compare with others legally in a track or down hills.
Ross - I think you are talking about your 3rd and 4th gear stock dyno runs. I'm talking about Jessee's 3rd and 4th gear turbo dyno runs. The gear made a pretty big difference with the turbo. Want me to post a chart comparing them?
3rd gear definitely showed lower peak number than 4th. This was 100% expected by the shop rolling the dyno and by me. Again - its the idea that a dyno is most accurate where a 1:1 ratio is achieved. I didn't do the math to figure out what gear had my 1:1, I just assumed I should use 4th as was done previously.
My higher axle gearing would have skewed my numbers down vice the factory 4.10s in a given gear. The higher gearing changes the engine's rate of acceleration as a matter of fact. Faster engine acceleration equals lower bhp. Again - the effect of this is different for every dyno manufacturer and the way it does its math.
I'm feeling another dyno run is in my future.
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