Has anyone ever considered....

[bjoehandley]

Hell, I'd still be willing to try one of the JK Minivan motors in a XJ (as well as thw fwd ones in a Lebaron Coupe and PT Cruiser......) It may not be enough motor in a 4dr JK and just sufficent in a heavily optioned minivan, but it supposedly made the pre factory turbo PT Cruisers real movers when swapped in and I wouldn't be the least bit surprised if the XJ, MJ, and J-Body Lebaron's would be far off that!


BTW Yossarian, I've got a friend who's into the LS motors, I'll get ahold of him tomorrow and ask. He currently works for a Chevy dealer and used to own an '03 Silverado Sportside that had a 4.3l V-6/5 speed stick combo (it had been a special order) and I can't remember if he said that was LS based or still the SBC based one.

 

[tbburg]

Not sure about turboing a 2.5.
Jeep used the Mopar 2.4 in a Wrangler, so it would be mainly parts gathering to put a SRT motor in an XJ.(and figuring out the computer,..)I'd probably go that route rather then turbo-modding a 2.5.

dasbulliwagen: Boring the 2.5 out as far as it can go is an option. As to taking it .150-.160 over: I don't like the fact he had it done without checking, but it's his jeep, and the work was free. I'd personally have the block ultrasound checked for core shift before any major bore upgrade like that. Not sure if the extra 10ci would be worth it anyway(ok, 12) I think his major power upgrade was from the breathing improvement and the unaccounted for compression rise due to the flat top pistons. Displacement increase probably had little to do with it.

140 HP at the rear wheels, with the stock cam and injectors: pretty good,..

 

[ChevelleSSLS6]

I'd kill for a diesel turbo 4-banger in my XJ.

Unfortunately however, those aren't very popular here in the US - too "dirty" for all the mindless liberals who don't know any better :doh:

I've heard the Diesel XJs (export market only.:bawl could get 30mpg. F*, my wife's Civic (I drive that damn puddle jumper to work every day) gets 32mpg average. I'd so "ditch dive" that Civic for a Diesel XJ.

...or even a Diesel Liberty and a Diesel JK. Is anyone from Mother Mopar listening? Maybe we should send them emails en-masse. Everyday. Tell them that the lunatic fringe can't afford 20mpg, but we want solid axles (at least a solid rear in the Liberty), and the simplicity offered by not having a hybrid. The only way around it is diesel power.

 

[Dr. Dyno]

Anyone want to tap Hesco for a cross-flow head w/ more modern combustion champer shapes?

Even Hesco abandoned the idea of a crossflow head. It simply isn't feasible with the block design of the 2.5 I4 and 4.0 I6.

 

[bjoehandley]

Even Hesco abandoned the idea of a crossflow head. It simply isn't feasible with the block design of the 2.5 I4 and 4.0 I6.

Somehow I get the feeling that a crossflow head would also require making it at least a SOHC design too.












Wonder how a DOHC stroker would run now........................................

 

[bjoehandley]

I checked with my friend on the V-6 question, he says that the current 4.3l V-6 is still the old SBC based motor that has been around for a while now. Guess to chop an LS down to a 6 require significant rebalancing of the rotating assembly from how the V-8's are balanced.

 

[Dr. Dyno]

Somehow I get the feeling that a crossflow head would also require making it at least a SOHC design too.

Yup. The whole 4.0 engine, not just the head, would need to be redesigned to accommodate a cross-flow head with single or double overhead cams. Not a viable proposition.

Somehow I'm not convinced that swapping a smaller displacement engine into an XJ is going to yield any significant mpg saving 'cause you'd also need to run it at higher rpm and use larger throttle openings to access the performance. Not to mention that you'd never recoup the cost of doing the swap.
At the end of the day I still believe that the most cost effective way to more power while maintaining near stock mpg is to upgrade your existing 4.0 and if it needs to be rebuilt, make it a 4.6.

 

[Bdiddy11]

Since this thread revolves around engine swaps...

What would be the consensus for the best engine swap for a MPG increase, ideally getting at least 20mpg in town?

VW 1.9 TDI or similar diesel VW
OM617 Merc
4bt (seems like there's better options than this heavy engine)
or...

My Cherokee is a DD during crappy weather and weekend warrior/expedition style rig. Not into rock crawling. Running a max of 32" tires. My wife and I agree that there aren't really any "new" 4x4s that we like and we're into the whole expedition style wheeling. So we figure, why not spend money on a motor swap to make the Cherokee more fuel efficient instead of buying a newer, slightly better MPG 4x4 and not be as happy with it.

We love XJs a lot and would rather spend more money on it than buying something that we are only partially happy with. We could buy a gas friendly car... but we hate little cars.

for kicks and giggles lets say that the budget is $9k or less

 

[Root Moose]

I bet an active displacement GM LS engine with a 6 speed (manual or auto) would get mid 20s highway if built properly.

Not sold on putting an ancient diesel in anything.

 

[souske]

That same 9K sure would buy a lot of fuel...

 

[Bdiddy11]

Sure it would... But that doesn't answer the question. Buying more fuel or an economy car isn't what i'm looking for.

 

[JTM]

Has anyone considered using a Toyota 3RZ (2.7L) about the same power as a stock 4.0 and they came bolted to an AW4 variant. TRD made a supercharger kit for it and LC Engineering has a Turbo Kit.

 

[Talyn]

3RZ output is 150 hp and 177 lb·ft . Not the same as a 4.0L. They are dogs of engines and a pain in the ass to work on, especially in their original vehicles.

 

[bigalpha]

The LC Engineering company makes a $2,500 turbo kit.

 

[themax01]

If miles per gallon is the issue then changing out the tranny and rear/front gears would be the solution. Putting a stock sbc 5.7 into a shortbox s-dime supposedly created 30mpg. What is the highest octane rating you could use in a stock 4.0?

 

[Talyn]

You can use what ever octane rating you like, but in a stock 4.0L there is no reason to waste money on higher than 87.

 

[Dr. Dyno]

Since this thread revolves around engine swaps...

What would be the consensus for the best engine swap for a MPG increase, ideally getting at least 20mpg in town?

VW 1.9 TDI or similar diesel VW
OM617 Merc
4bt (seems like there's better options than this heavy engine)
or...

My Cherokee is a DD during crappy weather and weekend warrior/expedition style rig. Not into rock crawling. Running a max of 32" tires. My wife and I agree that there aren't really any "new" 4x4s that we like and we're into the whole expedition style wheeling. So we figure, why not spend money on a motor swap to make the Cherokee more fuel efficient instead of buying a newer, slightly better MPG 4x4 and not be as happy with it.

We love XJs a lot and would rather spend more money on it than buying something that we are only partially happy with. We could buy a gas friendly car... but we hate little cars.

That's why I'd just keep my XJ and continue running a 4.6L stroker. On the highway it delivers slightly better mpg than my old 4.0, and with some restraint mid-20's mpg is possible. The cost of swapping in a more economical engine would never be offset by any fuel cost savings so why bother? An LPG conversion would be a viable proposition though.

 

[kastein]

The cost of swapping in a more economical engine would never be offset by any fuel cost savings so why bother? An LPG conversion would be a viable proposition though.

agreed. A lot of people miss this when they consider either making their XJ more economical or buying a gas sipper daily driver.

Let's say you could go from 17mpg to 25mpg by swapping in a $1k motor. Breakeven mileage is:
gallons you need to save = $1000/price per gallon (going to assume $3.60) = 278
miles you need to drive with the new motor to save this amount of fuel:
x miles / 17mpg = 278 gallons + x miles / 25mpg
solve for x
breakeven at 14768 miles (probably a year or two, though I'd hit this in around 6 months... hmmm...)

And that's assuming you actually get 25mpg because you're not driving your V8 XJ around with a massive shit-eating grin on your face, and that your entire V8 swap or stroker build costs $1k.

It's even worse if you decided to buy a nice fuel sipping DD to save money instead, because now you are paying insurance, registration, a few thousand for the car, repairs, etc for it. If you get the car ridiculously cheap or it gets ridiculously good mileage OR the XJ starts with terrible mileage, obviously this argument goes out the window. If the XJ gets terrible mileage, you are doing something wrong though, because I easily get 16mpg with a leaking fuel sender o-ring, 33s/3.55s/AX15, and a tired 4.0, even driving fast (maintaining 75-85 on the highway with ~500lbs in the bed.)

If you're looking for an excuse to swap an LS1 in don't let me dissuade you here, just go into it with open eyes and plan your budget sanely.

 

[Dr. Dyno]

And that's assuming you actually get 25mpg because you're not driving your V8 XJ around with a massive shit-eating grin on your face, and that your entire V8 swap or stroker build costs $1k.

You won't go from 17mpg to 25mpg by swapping a V8 in place of the 4.0 unless you start driving like a granny, in which case you could get 25mpg from the 4.0 as well without the cost of an engine swap. Incidentally, figure on a minimum of $3000 for a proper stroker build with external performance bolt-ons, and $5000+ for a V8 swap. You might be able to find the V8 itself for only $1000 but it's all the other parts and fabrication that'll eat up your budget.
Even if the cost was "only" $5000 and you managed a highly unlikely 5mpg gain, you'd need to drive 15,000 miles/year for 20 years to offset the cost in fuel savings. In other words, forget about ANY engine swap if your goal is just to save fuel.

 

[John(XJ)Jeep]

It's not too bad under normal driving I get around 20-22mpg. I've watched carefully one time on a trip. I can get about 516km to my 13gal tank which translates to about 24.53Mpg. When driving a little heavy it goes down to about 16-18mpg and in town haven't measured exactly yet but economically it's roughly 18mpg, on a 4.7 stroker. With this motor cruising speed is nice at around 140-150kph with about half inch of throttle input, normal driving maximum input needed is barely putting my foot on the pedal just enough to register movement is all I need.