Why does JT have poor throttle response?

[seven30]

Unless there’s something wrong with your throttle, I don’t think the Jeep has that bad of throttle response.

Go drive the new 4cyl land rover defender and come back and report your thoughts again on Jeeps response

Ha I took the 2001 4.0 Cherokee out earlier this evening. The is just no comparison in throttle respnse. The ole 4.0 has explosive response and loads of torque right where its needed. The whole jeep torques over when you punch it.
I dont get how the 3.6 with its fancy valve train lost so much on the lower end.

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[Blitzinger]

Have you asked Chatgpt?

 

[seven30]

Have you asked Chatgpt?

Why

That would be my entire question.

 

[JT1]

Ha I took the 2001 4.0 Cherokee out earlier this evening. The is just no comparison in throttle respnse. The ole 4.0 has explosive response and loads of torque right where its needed. The whole jeep torques over when you punch it.
I dont get how the 3.6 with its fancy valve train lost so much on the lower end.

Multiple reasons actually. The old 4.0 (I've had a few) had a mechanical throttle and the computer couldn't dull the response in the name of refinement, or limit torque in certain situations (the biggest reason)

Traction control. The old ones don't have it, the new ones do.

The biggest tire that ever came on a factory 4.0 was the TJ/LJ rubicon, and they were only 245/75r16's~ barely a 31 and factory 4.10s, so gearing at the tires was typically deeper

The 4.0 has a longer stroke and was cam'd for tractor use.. They are nearly 100hp down on the 3.6, but the torque curve on them started lower than the 3.6 which has essentially nothing until 1800rpm

 

[seven30]

Multiple reasons actually. The old 4.0 (I've had a few) had a mechanical throttle and the computer couldn't dull the response in the name of refinement, or limit torque in certain situations (the biggest reason)

Traction control. The old ones don't have it, the new ones do.

The biggest tire that ever came on a factory 4.0 was the TJ/LJ rubicon, and they were only 245/75r16's~ barely a 31 and factory 4.10s, so gearing at the tires was typically deeper

The 4.0 has a longer stroke and was cam'd for tractor use.. They are nearly 100hp down on the 3.6, but the torque curve on them started lower than the 3.6 which has essentially nothing until 1800rpm

Of course the 3.6 has more power where we rarely need it. OTOH the 4.0 has more power exactly where its needed. I guess its our fault for paying any attention whatsoever to HP numbers. Useless information. We say this all the time in racing: HP sells torque wins.

It would be interesting to see the 3.6 dyno curve after something like a Livernois change especially below 3000.

 

[NeatFreq]

The perfect comparison to this is to go drive a Tacoma TRD Pro, then be shocked at what bad throttle response really is!!!!!!

This is so true, or a TRD Pro 4Runner, I've had both and they sucked ballz

 

[JT1]

Of course the 3.6 has more power where we rarely need it. OTOH the 4.0 has more power exactly where its needed. I guess its our fault for paying any attention whatsoever to HP numbers. Useless information. We say this all the time in racing: HP sells torque wins.

It would be interesting to see the 3.6 dyno curve after something like a Livernois change especially below 3000.

The 4.0 has 200 lb/ft at 1200rpm. The pentastar makes about 150 lb/ft at 1500. Once you cross 2500 the pentastar has more.
Another HUGE factor is weight. Stick a 4.0 in one of these new heavyweights and see how it feels.

 

[JTDay]

I'm uncertain if anyone is supporting (able to unlock) the newer ECUs yet, but the Livernois gains are huge. I'm not really sure how they achieve this but hopefully they leave cam timing mostly alone. If they end up supporting new ECUs, I'll probably go the Livernois route.

 

[Dust]

3.6 is a v6. The 4.0 (258cid) is a straight six. In line produces more torque, ask Mercedes they went back to a straight configuration instead of the V. BMW has always had straight six configuration since the beginning back when they broke altitude/speed records with aircraft engines. Now the Hurricane 6. Old technology doesn’t mean obsolete. Watching for the first Hurricane transplant, sign me up! As for throttle controllers, Sprint Booster has for ME been the best hands down. Night and day for my 08 JKR with the 3.8. Dangerous entering on ramps with out it! Also my 2012 Toyota Tacoma TRD sport with a factory installed TRD supercharger ( yes even with a supercharger it was needed). A lot of people crap on these but those are people who never used one. Remember the old adage “you get what you pay for”. Sprint Booster’s aren’t cheap and yes there are other companies that claim they do the same, but Sprint Booster has been around a long time, and in my humble opinion perfected it. Easy to install/use, never had a code!

 

[seven30]

The 4.0 has 200 lb/ft at 1200rpm. The pentastar makes about 150 lb/ft at 1500. Once you cross 2500 the pentastar has more.
Another HUGE factor is weight. Stick a 4.0 in one of these new heavyweights and see how it feels.

True that. Wonder how the Cherokee would feel with the 3.6. Be interesting.

 

[Beemer533]

My late 2021 mfg MT Mojave stock gets 17 if I hammer it around town. Usually 19. Hwy 19-23 depending on speed. 75 it drops 18 but at ~7000 alt on I25 its back to 23. Thin air makes a difference.

Anyone have the Livernois setup?

Damn, I hope altitude has something to do with it. I average maybe 13-14 around town (upstate NY), bone stock Mojave.

If I'm on the highway for more than an hour I'll see my average maybe hit 15-16

My road trip to UT/CO last year the best I ever saw was just under 19. That was relatively loaded though with camping gear, maybe 450lbs or so.

 

[Beemer533]

Unless there’s something wrong with your throttle, I don’t think the Jeep has that bad of throttle response.

Go drive the new 4cyl land rover defender and come back and report your thoughts again on Jeeps response

It's pretty lousy, I put in the Hikeit and it really felt good. Until I accidentally turned it off, my Mojave felt like I lost power. It was bad enough that I noticed right away something wasn't right lol.


The gladiator isn't really under powered in my opinion, it's just tuned terribly and is really lacking torque down low...

 

[JT1]

True that. Wonder how the Cherokee would feel with the 3.6. Be interesting.

Since it weighs nothing, an XJ would be FAST especially with the 8 speed behind it

 

[ShadowsPapa]

Ha I took the 2001 4.0 Cherokee out earlier this evening. The is just no comparison in throttle respnse. The ole 4.0 has explosive response and loads of torque right where its needed. The whole jeep torques over when you punch it.
I dont get how the 3.6 with its fancy valve train lost so much on the lower end.

You've got to be kidding. I've got a built 4.0 in my little Eagle and although it could pull a building sideways at low throttle, there's no comparison on rate of acceleration and throttle response - at least compared to a 3.6 automatic.
The 4.0 can't possible wind up as fast. It's a long stroke, long rod engine with a heavy rotating mass and it takes time and energy to go from 600 RPM up to 2,000 RPM with a 4.0.
I'll pull things up a hill at idle that my JT would struggle with, but my 3.6 will trounce the 4.0 in a race.
I can spin tires, make 'em chirp in 2nd with my 4.0, but seriously, mashing the throttle with a 4.0 with a T5 behind it - no comparison to the 3.6 in the JT.

The 4.0 (258cid) is a straight six. In line produces more torque,

Not because it's an I6, but because of the long stroke.
I've had various long and short stroke engines. The longer crank throw and longer stroke = torque, not the configuration of the cylinders. Early V8s had tall cylinders and longer strokes but the need to downsize engines reduced the stroke. People wanted HP and fast acceleration. That's harder to do with a long stroke engine.

- here's supporting documentation -

The I6 is naturally balanced, and the configuration in the past allowed for tall cylinders, longer strokes, thus the torque. But there are drawbacks as well - including the need to support the long crankshaft and prevent crankshaft twisting. AMC touted "7 main bearings" with their 232 engines, and the later 258 (and of course the 4.0 inherited this)

 

[ShadowsPapa]

The 4.0 ......... and was cam'd for tractor use..

- where'd you get that?
It was one of few to have a split pattern cam, and the LSA had to be kept up to keep the period MAP happy.
The 4.0 grew from the AMC 4 cylinder engine. The idea came out of Mexico, VAM. AMC originally rejected the idea, but then decided to run with it for the Jeep line. The Eagle retained the 258.
The cam profile started out very similar to the 258 when the 4.0 first introduced.
In fact, cams will interchange.
Suggesting it was "cam'd for tractor use" is to say so was the 232 and 258.
The 258 pulled a lot of Jeeps and cars around for years.

Later mods to the 4.0 included changing cam profile and going to a split pattern.
I'm running a Comp xtreme 4x4 cam in my 4.0 and had to choose an LSA to allow me to use the stock PCM and MAP and so on.

I still wonder what the experimental aluminum head I have would do with my 4.0. If I had the time and energy, I'd swap it on and see.............it would sure lighten the engine up quite a bit.

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