SC vs. HEMI - Let the TRASH talk begin!

[UselessPickles]

It's reasonable estimation based on known drivetrain loss of a 5.7 Hemi Wrangler, comparing dyno charts to crank hp ratings. Again, read all the things I already stated about this being a best estimate with the available data, to be used for comparing general trends and relative differences. More specifically, for comparing large relative differences. Any area where the differences are very small could be well withing a margin of error of the assumptions.

The data I have so far is enough to see that the 6.4 Hemi will clearly destroy the superchargers throughout the RPM range, will destroy the turbo at low RPMs, but the turbo will likely have some level of advantage in the upper RPM range.

I'll gladly update everything as soon as someone produces an actual dyno chart of a 6.4 Hemi Wrangler. The amount of drivetrain loss becomes irrelevant then, because we'll have an actual measured torque curve at the wheels.

[HahaJK]

Looking at this from the view of a guy that wants more power for primarily trail runs and the occasional rock crawl, prodigy seems to be the best answer dollar for dollar. The 6.4L is out of the question simply due to price, but Magnuson, RiPP and Prodigy are all in the same ball park.

Reading up on the hot side of the turbos and pipes as well as the future problems of the prodigy though, I'm more swayed towards RIPP with a high boost pulley.

[gbaumann]

I know we're focused here on power but if Pickles has any spare computing time can we get a chart showing where the dollars go for these mods as they relate to power? We know what Mag, Ripp and Prodigy cost. I spent $28k on the 6.4. Which of the FI kits puts the torque/dollar in the most efficient spot? I'm assuming there's nothing efficient about the cost of the hemi. Assume daily driving with a typical commute and weekend trail time.

[UselessPickles]

Reading up on the hot side of the turbos and pipes as well as the future problems of the prodigy though, I'm more swayed towards RIPP with a high boost pulley.

Generalizations about hot pipes on turbo systems may not apply to the Prodigy system. The turbo is intentionally over-sized a bit for various reasons, so that it ends up not spooling much during typical cruising conditions. When the turbo is not spooled up and producing much boost, it's also not producing much waste heat beyond what a plain exhaust pipe would already do. If you're concerned about under-hood heat, then get the pipes ceramic coated. Also definitely put a turbo blanket on the hot-side of the turbo. The turbo kit also removes two sources of heat from under the hood: the catalytic converters. A new high-flow catalytic converter is included with the kit, and it's located about under the driver-side seat, underneath the vehicle (not in the engine compartment).

Off-road driving also does not spool up the turbo much in my experience. When I'm off road, I make use of gearing (4LO, low transmission gears) to keep RPMs up a bit in the mid-range area when I'm climbing stuff, which makes use of all the torque multiplication to keep engine load low, and throttle response good. Low engine load means low exhaust flow, which means minimal turbo spooling, and minimal extra heat from the turbo. The turbo itself, the wastegate, and some of the exhaust pipes are conveniently right behind the radiator fans and in airflow for cooling.


What "future problems" are you referring to?

Pickles, the 6.4L and 5.7L hemis since 2012 use the original trans. I have the same WA580E/NAG-1 that was bolted to my Pentastar. So your assumptions should be pretty good if you're figuring in the original trans dynamics.

Unfortunately, that still doesn't help me, because that's the stock automatic transmission. I currently have no way to model the behavior of an automatic, especially the torque multiplication of the torque converter whenever the converter is not locked up (which will especially affect the initial launch). I can only model behavior a manual transmission, so I'm limited to modeling a theoretical 6.4 Hemi with the Jeep's 6-speed manual (is that even a possible combination?). At least it's consistent for comparison to the rest of the power mods, which can definitely coexist with the stock manual transmission.

I know we're focused here on power but if Pickles has any spare computing time can we get a chart showing where the dollars go for these mods as they relate to power? ... Assume daily driving with a typical commute and weekend trail time.

Not quote sure what you're asking for here. Could you be more specific?

I also still plan to make some more charts illustrating how each option can accelerate in more normal driving situations - not in the best transmission gear for max acceleration. This will allow you to compare, for example, how much acceleration potential is there at 50 mph in 5th gear, and how many gears would less powerful options need to downshift to get equivalent acceleration at the same speed. I can already tell you without any doubt that the Hemi will be the indisputable winner here, and will cause the Hemi to generally "feel" much more powerful in daily driving that all other options (including Prodigy), even if Prodigy's turbo actually makes more power and is capable of faster full-throttle acceleration.

[UselessPickles]

BTW - my simulation based on dyno torque curve data has actually proven to produce realistic results for several vehicles already. My favorite example is a 2006 WRX STi. My brother bought one last year and was interested in using my simulation get some idea about how launching at different RPMs and different quickness of shifting gears might affect acceleration performance.

We found a stock dyno chart online, a measured coefficient of drag and frontal area, specs for transmission ratios, weight and tire size. Everything we needed.

First simulated run, launch hard at peak torque, assuming 0.5s shift times, and I got...

0-60mph: 4.9s
1/4 mile: 13.01s @ 104.4mph

One car website reported 4.9s 0-60, but no 1/4 mile time.

Another car website reported 4.5s 0-60, and 13.0 sec @ 103.5

Almost a perfect match to the reported 1/4 mile time, and a perfect match to one of the reported 0-60 mph times. But that quicker 4.5s 0-60 time from the other website was really bothering me. Which one was correct? 4.9 or 4.5? How could there be such a big difference? And what concerned me the most was that the website that had the 1/4 mile result that agreed with my simulation was the source of the 0-60 time that did NOT agree with my simulation! What have I done wrong!?!?!

Then I remembered that some car testers use a 1-foot roll-out (like a 1/4 mile race) for all acceleration-from-a-stop tests, including 0-60 mph tests. This produces quicker 0-60 results because there's a 1-foot head start before the timer starts. So back to the simulation to test this hypothesis...

Simulated 0-60 with 1-foot rollout: 4.57s

Much better!

I was then able to slightly tweak the launch RPMs and shift times, still within a reasonable range, and get results that even more perfectly matched the websites reported results.

[KaiserBill]

It's reasonable estimation based on known drivetrain loss of a 5.7 Hemi Wrangler, comparing dyno charts to crank hp ratings. Again, read all the things I already stated about this being a best estimate with the available data, to be used for comparing general trends and relative differences. More specifically, for comparing large relative differences. Any area where the differences are very small could be well withing a margin of error of the assumptions.

The data I have so far is enough to see that the 6.4 Hemi will clearly destroy the superchargers throughout the RPM range, will destroy the turbo at low RPMs, but the turbo will likely have some level of advantage in the upper RPM range.

I'll gladly update everything as soon as someone produces an actual dyno chart of a 6.4 Hemi Wrangler. The amount of drivetrain loss becomes irrelevant then, because we'll have an actual measured torque curve at the wheels.

I read your statements. You're once again making too many assumptions based on too little data. You've derived this figure of 30-33% loss due to drive train without actually having any really good baseline information about the Pentastar Engine that I can see. You're seeing Wheel HP figures and attempting to working backwards to a Flywheel/Brake HP figure without having enough data about the engine. I've not seen one add on kit that talks about BHP and not WHP... In fact all of them state the fact that they only test on chassis dynos.. Which sort of makes me wonder what they are trying to fudge with the for marketing purposes. People will say "Oh Wow... It is has to be so much more at the flywheel..." and purchase this kit. And they don't take the engines out and really dyno them.

If you want to really find out how much your engine is loosing between transmission, transfer case, axles and so on you have to take the engine out and dyno it and find out what sort of power you're getting. And then if you want to talk about Jeeps in general you have to get a very respectable sampling size of all the possible combinations from the factory so you can say okay -- Engines alone had this tolerance in power +/- over the stated horsepower, then hook it up to the transmission and dyno that combination and that will give you the ability to see what the power loss is in that combination, then you can check out the axle ratio combinations. Then you can build a baseline and come up with same average performance numbers and say okay-- this what A JKU with 3.6L V6 and 6spd Manual with 4.10's averages out to or model x , z, y... and then you say okay lets play with this variable or that one. Right now all your data is vehicle specific and it is way too general to even make any meaningful conclusions about performance extending past a few controlled variables.

For example if this AEV kit makes 400Hp at it sees a 27% loss in power it is down to 292WHP ... I'm skeptical that you will see the types of losses you claim the wrangler is seeing. For example if the Ripp system creates 325 hp at the rear wheels and that is after it has lost a 1/3 of it's power that means it must have well over 400hp at the crankshaft! They want you to believe that you making what nearly 200hp extra at the crankshaft with a bolt on turbo kit and not affecting the compression ratio and so on. I could see a 125-136hp at the crank shaft and loss of about 30-40hp through the drive train at best.

I think you've done a lot of hard work but the problem is you need more data still to make any really interesting conclusions beyond that of your vehicle.