25+mpg 4.0l ohv build

[superj]

when i did megasquirt, back in 2009 or 2010, it was 700 bucks for the ms2 system that you soldered yourself on the desk at home. it was really awesome to do and took me a week after work in the evenings. i believe the make a lot of kits already assembled now for many popular motors so you might be able to get one already built for your truck.

you do need some different sensors, a laptop, and one or two other things in order to use it properly though so you might go over the 1k mark. or see if any are on ebay for cheap

 

[Angry Possum]

I'm battling with poor gas mileage currently. Stock 93 Ranger XLT Supercab. 4.0 132k miles.
I just did a full tune up, all filters, new wires etc.
I'm still getting a dismal 11mpg city and 16 or so Hwy. Going to replace the 02 sensors for a start. Eventually I may do the Electric Fan. Maybe I'll look into a new MAF etc. What else should I consider? Synthetic Oil...

 

[DPDISXR4Ti]

I'm battling with poor gas mileage currently.

Do you have a A/F gauge of some sort? They often get dissed since they're not terribly useful as a tuning aid, but what they will tell you is whether closed-loop operation is occurring. If you're not going closed-loop, you'll certainly get decreased fuel mileage.

 

[Angry Possum]

Do you have a A/F gauge of some sort? They often get dissed since they're not terribly useful as a tuning aid, but what they will tell you is whether closed-loop operation is occurring. If you're not going closed-loop, you'll certainly get decreased fuel mileage.

Thanks, Firstly, What is an AF Gauge and how or where would I actually hook it up to test the loop etc.

 

[DPDISXR4Ti]

Thanks, Firstly, What is an AF Gauge and how or where would I actually hook it up to test the loop etc.

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[Roert42]

Something that is also extremely useful for optimal mpg is a vacuum gauge.

a vac gauge could gain you a couple mpg by simply telling you to shift sooner or later.

 

[gaz]

*UPDATE*

An unforeseen issue arises;

When I tore down the 1994 Ranger doner OHV 4.0l, I was in such a rush to get the heads to the machinist that I neglected to check which casting they were. As an unforeseen good turn of fate, my machinist and I decided not to mill the heads and just take the compression bump from the 01+ SOHC pistons. As it turns out, that Ranger did not have it's original 94 spec heads; when it was originally rebuild, the mechanic must have sourced and installed 98 spec heads on the 94 block/piston (verified).

So this doner 94 Ranger had a pretty good setup, 94 spec short block with 98 spec heads, running a bit over 10:1.

I am faced with a build I had not intended to take on just yet:
• 94 short block
• 01+ SOHC flat tops
• 98 spec heads

Now the anticipated compression ratio is definitely over 11:1, from what I have read, as high as 11.4:1.

My excitement is now off the charts boy n gils as this will once and for settle the question regarding the use of SOHC flat tops with a 95-98 spec fast burn combustion chamber.

Though I have read that many have accomplished this build, I remain uncertain. Also if memory serves, I only recall builders trying to run it with the 98 PCM. Hopefully, the forgiving nature of the 94 California emissions PCM will love it

 

[Uncle Gump]

That's gonna be tough to run on pump unleaded. I would think no way around pump premium at a minimum.

As forgiving as that ECM is... it might not be enough. A stand alone system that you can alter spark and fuel curves would be a better choice.

Good Luck....

 

[DPDISXR4Ti]

So this doner 94 Ranger had a pretty good setup, 94 spec short block with 98 spec heads, running a bit over 10:1.

The 4L engine I picked up last year has the same setup. For whatever reason(s), it seems rebuilders like to use the '98 heads with the smaller chambers. FWIW, the guy I got it from claimed he ran it with a stock calibration PCM. That said, it had 24pph injectors in it, so I think he "tuned" it by simply throwing more fuel at it. My plan was to retard the base timing a couple degrees by making the pickup mounts ovalized.

As suggested above however, running a 11.4 C/R engine will present some challenges on pump gas. I don't think you could even "fix" it by timing adjustments. I can't say that for sure - that's just my SWAG.

 

[Snoranger]

That sounds like it would be a great engine to run on propane.

 

[gaz]

@snoranger ,
I am inclined to feel that you are serious. I have used Rangers on propane and really liked it. I am uncertain where I would put the tank with a BII.

 

[gaz]

@Uncle Gump , @DPDISXR4Ti ,
I am leary of the valve clearance with the 98 head and SOHC pistons, so I will try the heads with 94 shallow dish pistons 1st.

I am not leary about 11.4:1 on pump premium, the 2.9l in my Ranger is just under 11.5:1 [typo, corrected from 12.5:1], if I can get even close to well that works, I will be happy. These engines really like compression, as long as there are well cooled.

 

[Snoranger]

@snoranger ,
I am inclined to feel that you are serious. I have used Rangers on propane and really liked it. I am uncertain where I would put the tank with a BII.

I am serious. Propane has an octane rating of around 108… that would work well in an engine running 11:1 compression.

 

[DPDISXR4Ti]

I am not leary about 11.4:1 on pump premium, the 2.9l in my Ranger is just under 12.5:1, if I can get even close to well that works, I will be happy. These engines really like compression, as long as there are well cooled.

Thanks for that data-point. It gives me less cause for concern about running the 10:1 yielded by the '98 heads with the stock '94 bottom-end. While you can find anecdotal references to that combination "burning the engine down", they seem to be mostly based on conjecture rather than actual experience.

The other thing to think about for a simple, "tuning, not really tuning" experiments is using different PCM's from different donors. A couple guiding thoughts...
1) A 2WD vehicle should have a slightly more aggressive ignition map than a 4WD
2) An EGR-equipped vehicle should have a slightly more aggressive ignition map than a non-EGR vehicle.
Given that, a 4WD, non-EGR donor would have the most mild ignition map, which is what you would want to start with on a higher (than stock) compression engine. Fortunately, that should be an easy PCM to locate. I'm assuming 2WD 4.0's are few and far between. I don't recall ever coming across one in the junkyard.

 

[gaz]

@DPDISXR4Ti ,

All of my mechanical mentors have agreed on this point, exactly the same way; naturally aspirated engines, running up to 13.5:1 compression ratio on pump premium, no need for concern of detonation but measures should be employed to manage the extra heat:
• engine oil cooler
• improved top end oiling
• increased engine oil capacity
• 1 or 2 heat ranges cooler spark plugs
• reducing unnecessary engine loads
• increased radiator cooling capacity
• lower temps under the hood