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Discussion Starter #1
Took the Jeep to KC Maxx Performance today for a little dyno tuning. MoTech did the original swap a couple years ago and tuned it pretty conservatively. I recently did some work replacing the intake tube and updated the tune with HP Tuners using the timing, air, and fuel tables from a 2013 Camaro SS LS3. I wanted Ryan (KC Maxx) to verify my work and make sure I didn't have any risk of detonation or lean AFRs. They were great to work with. I captured some of the dyno pulls on video and posted it to YouTube for your viewing pleasure. He did all the pulls in 3rd gear to keep the drive shaft and tire speed safe. It shouldn't affect the final dyno numbers too much.


 

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Discussion Starter #3 (Edited)
Yeah. It's definitely not breaking any records, but I'm happy with it. My intent wasn't to brag about a power monster, but to share a real-world verified number. I think it's fine when you consider it was a third gear pull, driveline loss, and the 35" tires. I'm not sure what the typical driveline loss is with the 6l80 and Jeep transfer case? The wheel and tire combo is about 100 lbs per corner, so it takes a little power to get them spun up. It drives great on the road and feels like plenty of power to me. Especially when you consider the original 3.6 made 285hp at the crank. I'm not sure what that would have been at the tire...
 

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~14% powertrain loss. I would say that number is high.
For an auto trans... hardly. The old standard used to be about 20% for an auto trans. These days the transmissions are more efficient and the loss is less but 14% is great considering.


To put it into perspective my 525hp crate engine came out to 360ish hp iirc. My rolling stock is 140lbs per corner and the looser converter soaks up a bit of power itself.

I don't think folks put enough thought into how much a heavy wheel / tire setup affects performance.
 

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Discussion Starter #6
For an auto trans... hardly. The old standard used to be about 20% for an auto trans. These days the transmissions are more efficient and the loss is less but 14% is great considering.


To put it into perspective my 525hp crate engine came out to 360ish hp iirc. My rolling stock is 140lbs per corner and the looser converter soaks up a bit of power itself.

I don't think folks put enough thought into how much a heavy wheel / tire setup affects performance.
Doing the math, and assuming that my motor is making the advertised 430hp at the crank, 345hp is right at 80% of the crank figure. That means the 20% loss figure would be right on.
 

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For an auto trans... hardly. The old standard used to be about 20% for an auto trans. These days the transmissions are more efficient and the loss is less but 14% is great considering.


To put it into perspective my 525hp crate engine came out to 360ish hp iirc. My rolling stock is 140lbs per corner and the looser converter soaks up a bit of power itself.

I don't think folks put enough thought into how much a heavy wheel / tire setup affects performance.
No I meant having only 15% powertrain loss is low in this situation. The old 15-20% "rule of thumb" comes from the performance world so 2 wheel drive, performance tires etc... My stock JK had close to 50% powertrain loss

Doing the math, and assuming that my motor is making the advertised 430hp at the crank, 345hp is right at 80% of the crank figure. That means the 20% loss figure would be right on.
Sorry I did the math assuming a 400 hp crank rating. 20% is going in the right direction but I still think its more than that in a JK with a t case, larger drive shaft, larger axle components and big tires to spin.
 

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No I meant having only 15% powertrain loss is low in this situation. The old 15-20% "rule of thumb" comes from the performance world so 2 wheel drive, performance tires etc... My stock JK had close to 50% powertrain loss



Sorry I did the math assuming a 400 hp crank rating. 20% is going in the right direction but I still think its more than that in a JK with a t case, larger drive shaft, larger axle components and big tires to spin.
Ahh, gotcha. The t-case when in 2wd really isnt contributing negatively to performance. There is a small bit of rotational mass there but it's not much and you aren't driving the chain.



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E38. I think that's what Robbie suggests for all of his Gen IV swaps. Does Jon at RPM give you more flexibility regarding the GM ECU?
I'm running an e38 as well. I asked because the e38 can be run with flex fuel. All you have to do is get the sensor and plumb it inline one of the fuel lines and wire in the 3 wire pigtail. Only 1 of the wires actually goes to the ecu, the other 2 are power and ground.

The benefit here is that while it's fairly inefficient because it's 85% ethanol.... It's flippin 105 octane. You can get at least a 30hp wheel increase just running straight e85. So you install the sensor and go back to your tuner to have it setup and now that the sensor is there it will adjust your tune for e85 when it is present. The cool part is that it will detect % of e85 and adjust accordingly. Obviously the best gains will be from running straight e85 but you can run any blend in between and not screw anything up.

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Thanks for the info. I didn't realize that e85 was 105 octane. That explains why so many guys run it at the track.
Yep, so for $100ish said and done you can get another 30ish rwhp. Also it comes with that nice sweet smell that burning high octane fuel makes.

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Yeah. It's definitely not breaking any records, but I'm happy with it. My intent wasn't to brag about a power monster, but to share a real-world verified number. I think it's fine when you consider it was a third gear pull, driveline loss, and the 35" tires. I'm not sure what the typical driveline loss is with the 6l80 and Jeep transfer case? The wheel and tire combo is about 100 lbs per corner, so it takes a little power to get them spun up. It drives great on the road and feels like plenty of power to me. Especially when you consider the original 3.6 made 285hp at the crank. I'm not sure what that would have been at the tire...
I'm sure you still have some more ponies to unlock if you wanted to but it's plenty of power for a JK! My LS2 pulled 324 at the wheel in 3rd gear (6L80E) and 37s on a 20" wheel. My dyno guy figured closer to 30% drivetrain loss (He tunes a lot of hotrods and 4x4s around here).
 

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Discussion Starter #15
I don't think folks put enough thought into how much a heavy wheel / tire setup affects performance.
That's a good point. It would be interesting to do an experiment comparing dyno pulls with a heavy set of off road tires vs stock size tires. If someone had convenient and cheap access to a dyno, and a set of stock-size tires, it could be done. I've read a lot regarding powertrain loss from the mechanical bits, but not much to address how tires affect the numbers.
 

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That's a good point. It would be interesting to do an experiment comparing dyno pulls with a heavy set of off road tires vs stock size tires. If someone had convenient and cheap access to a dyno, and a set of stock-size tires, it could be done. I've read a lot regarding powertrain loss from the mechanical bits, but not much to address how tires affect the numbers.
It's exactly why racers use as light of wheel, tire, and brake setups that will still hold up.

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That's a good point. It would be interesting to do an experiment comparing dyno pulls with a heavy set of off road tires vs stock size tires. If someone had convenient and cheap access to a dyno, and a set of stock-size tires, it could be done. I've read a lot regarding powertrain loss from the mechanical bits, but not much to address how tires affect the numbers.
You'd also have to change the rearend gears to go with the change in tire size if you wanted accurate data for different wheel/tire weights. 28" tall tires and 5.13 gears would skew the numbers a bit. Would be fun to do burnouts though.
 

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Hi there, crate engine dyno'd @ 427 h/p & 463 F.P.T. Running TH400, 4:10 in one tons and 38's. I think my wife's Toyota Corolla might be faster on road. In 4wg low, it's a friggin' monster though.
 

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That's a good point. It would be interesting to do an experiment comparing dyno pulls with a heavy set of off road tires vs stock size tires. If someone had convenient and cheap access to a dyno, and a set of stock-size tires, it could be done. I've read a lot regarding powertrain loss from the mechanical bits, but not much to address how tires affect the numbers.
I would try it if I could get stock wheels over my brakes. My dyno guy built a 72 Scout with an LS3 and he had around 40hp difference between 31" and 35" tires.
 

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Discussion Starter #20
I would try it if I could get stock wheels over my brakes. My dyno guy built a 72 Scout with an LS3 and he had around 40hp difference between 31" and 35" tires.
That's crazy. I wouldn't have expected 40hp. Rolling resistance and the unsprung weight associated with heavy wheel/tire combos obviously kills fuel economy and overall power. I just didn't realize exactly how much! Thanks for sharing your tuner's observation.
 
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