Gas Mileage? MPG?

[Drooque]

Hello All,
I have seen many people state, both on this forum and other places, that their stoker gets better gas mileage than their previous 4.0 did. If that is true, what would be the best stroker recipe for gas mileage?
Obviously, driving behavior plays the bigger role, and if you have a higher output engine, getting on the throttle is more tempting, but what would be the best recipe assuming conservative driving?
Another 'obvious' would be that at some point, increasing power has to come at the cost of fuel efficiency.
Thank you,

[Randy Bobandi]

I have seen many people state, both on this forum and other places, that their stoker gets better gas mileage than their previous 4.0 did.

If those reporting an increase in fuel economy after their build are being honest, it's likely the result of going from a tired engine to a fresh engine. Things like clean intake and exhaust ports/valves and better ring seal. Most stroker engines end up with higher compression as well.

A low friction, lightweight 4.0L rebuild is the most economical approach. The economy build definitely doesn't start with a $600 3.895" stroke crankshaft.

[Cheromaniac]

I have seen many people state, both on this forum and other places, that their stoker gets better gas mileage than their previous 4.0 did.

If those reporting an increase in fuel economy after their build are being honest, it's likely the result of going from a tired engine to a fresh engine.

Not necessarily. Although my old 4.0 had 174k miles on it (mostly highway) when I swapped in the 4.6 stroker, it was still running like a raped ape and wasn't burning any oil.
At the end of the day, I reckon I was getting better gas mileage from the stroker 'cause the extra torque meant I needed less throttle to accelerate at the same rate.

[Drooque]

I should have been more clear when I said gas mileage. My question, for research purposes, would involve highest miles per gallon, and not related costs. So a $600 crank would not come into play (and it's not that hard to source a very inexpensive stock crank from a 4.2l). Also, added cost of higher octane gas would not be considered.
For the sake of argument, and maybe adding some more fun to the forum, let me pose this hypothetical scenario"
Wealthy far green environmentalist (definitely not myself) regularly has to drive about 30 minutes on the interstate followed by 30 minutes up a steep dirt road to maintain a solar array. His WJ is a perfect size to hold his heavy tools and equipment, but the tired 4.0l struggles with the climb. He also believes he should reuse vehicles and parts as much as possible. What stroker recipe should he use to update his Jeep???
So I'll throw some thoughts out there, but I am definitely not an expert in the area. Recipe might include: highest compression the premium gas for the given elevation would allow, cam with little to zero overlap, 2000-2006 Base stock ECU and EFI other than 24lb injectors and all sensors working properly, proper custom tuning.

[75SV!]

I'd look at gearing too. Especially, since you mentioned going up an incline. Also, I changed some stuff on a 2" lifted Jeep with 31's and a worn stock motor. I was getting 17.5-18.5 mpg. I did the cut and fold on the rear quarters. Changed to synthetic gear oil, front and rear axles, and added the window deflators. I was getting 19.5 to 20.5 mpg highway.

[Russ Pottenger]

Definitely, don’t be surprised if your mileage picks up with a stroker build. I agree with all of the previous reasons previously stated, but would add an additional reason is the ability and opportunity to improve piston quench that would help to improve combustion/power efficiency.

[Cheromaniac]

Definitely, don’t be surprised if your mileage picks up with a stroker build. I agree with all of the previous reasons previously stated, but would add an additional reason is the ability and opportunity to improve piston quench that would help to improve combustion/power efficiency.

My gas mileage improved despite the stroker having a modest 9.3:1 compression ratio and a quench height of 0.088".

[Drooque]

Excellent point Russ.
I probably should stop assuming compression and quench go hand in hand. I grew up in a performance garage, and I was always taught to achieve desired compression through CC and gasket. It was always just assumed to work with machinist and piston selection, rod selection, rpm range to achieve tightest quench (or what I knew as 'piston to head clearance').
Would you say that if budget allows, you should always temporarily install pistons, measure quench and then deck block accordingly?

[Russ Pottenger]

Having a shop that builds performance and racing engines, I’ve had the benefit of having the tools and measuring equipment to measure the center to center if connecting rods and the block deck height prior before doing any machining. This, of course has been a valuable timesaver.

With that said, absolutely anything you can do to more accurately hit your tolerances more closely it will reward you in the end.

[Drooque]

Having a shop that builds performance and racing engines, I’ve had the benefit of having the tools and measuring equipment to measure the center to center if connecting rods and the block deck height prior before doing any machining. This, of course has been a valuable timesaver.

With that said, absolutely anything you can do to more accurately hit your tolerances more closely it will reward you in the end.

Do you have tolerance numbers you use for these strokers for different rod types (rod stretch)?

[Russ Pottenger]

Having a shop that builds performance and racing engines, I’ve had the benefit of having the tools and measuring equipment to measure the center to center if connecting rods and the block deck height prior before doing any machining. This, of course has been a valuable timesaver.

With that said, absolutely anything you can do to more accurately hit your tolerances more closely it will reward you in the end.

Do you have tolerance numbers you use for these strokers for different rod types (rod stretch)?

Factoring in the head gasket thickness and proper piston to cylinder wall clearances at TDC ideally you should be shooting for .035 plus or minus .005