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Stroker Fuel Mileage

17K views 26 replies 12 participants last post by  mdm 
#1 ·
I am thinking about putting a stroker kit in my 2000 wrangler 4.0 I6. Would this increase my fuel mileage or hurt it?
Thanks,
 
#2 ·
more fuel per combustion.

Fewer revs needed to get the same power.

If you keep your foot out of it and don't hot rod it, it'll probably be a wash, if not improve your fuel economy. But most of the time, rebuilding the engine and making it better tends to also install the lead foot mod. Don't expect gains.
 
#8 ·
If everything is bone stock and given the motor is tuned and the exhaust system is in good shape then you are getting the best MPG's that you are going to get. Going higher and larger tires will lower your MPG's unless you regear to compensate for the larger tire. You will also need to change your speedometer gear to compensate for the larger tire and gear ratio change.
 
#17 ·
False.

You're saying that a factory 4.0 5MT TJ on factory 235's with 3.07 gears will get identical fuel economy as the same 4.0 5MT on factory 235's TJ but with 3.55 gears?

Regearing, going with a different tire size/weight, or improving the engine's efficiency and/or powerband WILL provide an improvement in fuel economy. Now, increasing the engine's displacement isn't fundamentally ideal towards improving fuel economy by default, but when you're dealing with an engine that is built from the factory to be a dog until 2200 RPM, when you know for a fact that a simple cam profile change will change that, it's very possible that adding torque from 1k-2k rpm, allowing you to run in a higher gear/lower RPM than currently, will improve fuel efficiency even while adding displacement. Allowing that engine to get more power out of the available fuel delivery at a lower RPM is probably the BEST way to improve mileage.

But I stand by my statement that any time you do a major engine overhaul, you're tempted to give her all she's got...so measuring fuel economy changes will be difficult.
 
#11 ·
Okay, well 28" tires with 3.07 gears is stock. There is nothing you can do to get better MPG's. If you go to 33" tires your MPG's will drop like a rock. Therefore you will need to regear to 4.11 gears to get the motor back to where it needs to be. You will also need to replace the speedo gear to a 26 tooth so it will show you your correct speed and MPG's. Stroking the motor will not give you better MPG's. Welcome to the JEEP world.
 
#12 ·
Building a stroker motor will not have a significant impact on fuel economy by itself. Everything else being equal, you can ink of it in terms of brake specific fuel consumption (bsfc), which is typically measured in lbs/hp hr. Any given engine design (ie in line 6cyl spark ignited fuel injected) will operate within a fairly narrow band of fuel consumed per lb or gallon of fuel used. There are a few small efficiencies that can be gained! But without a major change in combustion system, fuel system, or basic physical concept, you won't have a major change in bsfc. What this really means is that with a stroker motor you can mAke more power, but you certainly would not expect to have an increase in fuel economy. The typical reaction to an increase in hp would be to use more of it. For every additional hp used, more fuel will be consumed.
If young a little deeper into engine physics, you would think about throttle losses which increase for a higher displacement engine at the same power output. In the end, you would want the smallest displacement engine practical to produce the power that you need in order to get the best fuel economy.
That's a long winded way of saying that if your only goal is higher fuel efficiency, a stroker motor will not accomplish that.
 
#15 ·
Yeah, definitely go with 4.11 gears. I have a 98 4.0L with 32RH 3 speed auto and 3.73 gears stock. Perfect combo for 31's, but when I jumped to 33's, Jeep became noticeably less responsive. Could be my shift range is off a little though too. I have yet to recalibrate my speedo, as I need a digital calibrator due to running the JB Conversions SS SYE. You can find a 4cyl Jeep with dana 30's and they will most likely come stock with 4.11's. Easy and cheap mod to get the proper gearing, whereas gearing your stock axles will run $1200 and up. You can likely get both axles at a scrapyard for less than $300.

Regarding stroker kit, yeah not much gain for the money. I have "heard" of guys swapping in a late model Chevy 5.3 and accompanied transmission and getting around 22mpg if driven conservatively. Would definitely go that route instead of stroking the 4.0 unless you want to put your own stroker together using 258 crank and connecting rods. You can easily build a Poor Man's stroker for around a $1000 with approx 260 hp and 300+ ft lb tq. The extra power would help for cruising as your rpm's would be less as you wont have to use as much power to attain the same speed. You still have to factor in the wind drag and poor aerodynamics of a stock jeep, let alone one lifted 3-4" over stock
 
#16 ·
You can find a 4cyl Jeep with dana 30's and they will most likely come stock with 4.11's. Easy and cheap mod to get the proper gearing, whereas gearing your stock axles will run $1200 and up. You can likely get both axles at a scrapyard for less than $300.

Man less than $300 for both axles...must be nice. Around here 4cyl axles are hard to come by and when you do they're more like $400 a piece.
 
#19 ·
Hey JR,
I have a 2000 TJ with the stroker and 33s with 3.73 ratio right now. what totally sucks about your situation is the gear ratio. With 3.73 I have been able to get around ok with my 33" tires. With 3.07s with 33s isnt any fun and its hard to just get up a curb without gassing it, at least thats how it was with my '78 wagoneer...

The stroker for some people is a wash as far as gas mileage. Depends on the build that is done and like the others said, how much you hit the gas. I am going to calculate my mph soon. I was almost there and I disconnected my battery so I lost my ODO record I was saving. The stroker has given me more power up hills and I generally put less foot into it now. I am still planning on regearing soon to 4.11 or 4.56 depending on my tire size.

With the cost of a stroker and you having a good engine... I would use your money to get a different rear axle and regear for your 33" tires. I needed an engine, so I did the stroker first and I still feel the need to regear. Good Luck.
 
#26 ·
Sound like your in the same boat as me. You want more power but you also want better fuel economy (because you know its possible to have both) That is the reason I wont be doing a hemi swap. I believe I'd really like to do a diesel swap, I've read anywhere from 25-low 30's mpg, but it looks to be more than I am capable of. Seems to need more fabricating of parts then an LS swap. So it looks like an LS swap, hopefully a 6.0. Looks like low 20's mpg if your conservative. Whatever you do, as long as your getting better gas mileage then eventually the swap would pay for itself, at least thats how I look at it. Yes it will take a long time but I plan on keeping it forever.
 
#27 ·
I was getting a shade under 14 MPG with the stock engine w/35" tires, 3.73 gears, and the 5 speed.

Rebuilt the engine into a 4.6 stroker with a different cam, set for advanced valve timing. Still got a shade under 14 MPG.

Regeared to 4.88 gears and still got a shade under 14 MPG.

Hmmm - Where could I be going wrong? I don't think I am. However, I would be going wrong if I was expecting to get better MPG from the rig.
 
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