souping up the OHV 4.0

[Bird]

Can you go into more detail about how to tune this area? For this could be the information I was looking for about my build. As you are aware from a different thread I was/am having that small problem, and after the injector swap tings have mellowed out for the rich burning, however, i still feel that she isn't running 100% yet. any knowledge on this fine tuning will be appreciated. (links??)

thanks

You have to keep in mind that adding headers, swapping cams, porting heads, etc change the 'flow' in an engine (volumetric efficiency), thereby necessitating fueling changes. With a 'properly tuned' MAF based system, the MAF transfer function will 'usually' be able to accomodate this increase in air flow and keep the fueling in line as long as the MAF doesn't max out at WOT. Adding headers and porting the heads usually don't require a retune as all you're doing is increasing flow - throw a cam into the mix and everything changes. All of a sudden, the valve timing events play a role in the fueling. Throw some overlap between the exhaust and intake valves and now you're allowing some of that fuel that the PCM / tune thinks is going into the cylinder to combust to actually go out the exhaust valve - resulting in a leaner combusion condition that under closed loop will be compensated for by adaptive fueling, but under open loop wouldn't. A tweak would be needed either in the requested fuel tables or, better yet, in the injector timing to delay the firing of the injector slightly - keeping the fuel in the intake stroke. (this will also help get rid of the raw gas smell in the exhaust)
Changing out heads or pistons for more compression (ie: adding 95+heads to pre-95 shortblocks) throws another factor in the equation - you will usually need higher octane fuel to control detonation and also increase fueling a bit under open loop operation to keep A/F ratios in the proper range for best power.
If you change to different injectors or a bigger MAF, now closed loop operation will be affected - you have to change the injector parameters so that the PCM will know how much pulsewidth to apply for proper fueling and the MAF transfer function will have to be changed out to reflect the different values that the new MAF will report for airflow. Some of the aftermarket MAFs claim to be calibrated for specific injectors, but there are several assumptions / 'SWAGS' in those calibrations. Also, contrary to popular belief, the factory Ford MAF's are not calibrated for specific injectors - you can't just swap in a bigger MAF from another engine with the same size injectors and expect it to be good.

OK - end of today's lesson.

Bird

ps. SWAG = Scientific Wildass Guess

 

[shadetree]

You have to keep in mind that adding headers, swapping cams, porting heads, etc change the 'flow' in an engine (volumetric efficiency), thereby necessitating fueling changes. With a 'properly tuned' MAF based system, the MAF transfer function will 'usually' be able to accomodate this increase in air flow and keep the fueling in line as long as the MAF doesn't max out at WOT. Adding headers and porting the heads usually don't require a retune as all you're doing is increasing flow - throw a cam into the mix and everything changes. All of a sudden, the valve timing events play a role in the fueling. Throw some overlap between the exhaust and intake valves and now you're allowing some of that fuel that the PCM / tune thinks is going into the cylinder to combust to actually go out the exhaust valve - resulting in a leaner combusion condition that under closed loop will be compensated for by adaptive fueling, but under open loop wouldn't. A tweak would be needed either in the requested fuel tables or, better yet, in the injector timing to delay the firing of the injector slightly - keeping the fuel in the intake stroke. (this will also help get rid of the raw gas smell in the exhaust)
Changing out heads or pistons for more compression (ie: adding 95+heads to pre-95 shortblocks) throws another factor in the equation - you will usually need higher octane fuel to control detonation and also increase fueling a bit under open loop operation to keep A/F ratios in the proper range for best power.
If you change to different injectors or a bigger MAF, now closed loop operation will be affected - you have to change the injector parameters so that the PCM will know how much pulsewidth to apply for proper fueling and the MAF transfer function will have to be changed out to reflect the different values that the new MAF will report for airflow. Some of the aftermarket MAFs claim to be calibrated for specific injectors, but there are several assumptions / 'SWAGS' in those calibrations. Also, contrary to popular belief, the factory Ford MAF's are not calibrated for specific injectors - you can't just swap in a bigger MAF from another engine with the same size injectors and expect it to be good.

OK - end of today's lesson.

Bird

ps. SWAG = Scientific Wildass Guess

To the OP, i find it amazingly hilarious that a lot of the information you have/will recieve on this subject will come from people that have little / none knowledge of the internals of the 4.0 and the possibilities of modifications - they're standard answer will be "change the gears - there's nothing else that you can really do". While that will work in some instances, it's not the 'do all / be all' for your wants.

Great info Bird. shady

 

[Angie]

OK - end of today's lesson.

Bird


THANKS !!!! you have given me the direction that I am needing to look into. You Da' man when it comes to these mods and your depth of knowledge here is a gold mine... thanks

 

[Bird]

One more thing - when I said that most people that recommend gears have no knowledge of the internals / design / capabilities of the 4.0, I definitely wasn't referring to AllanD - he has more knowledge than most of the rest of the forum combined and can always be counted on to be a voice of practicality and common sense when other's are voicing misinformation and wild ideas - I usually don't speak up in most of these threads because he's already said what I would..............

Now, some of the others out there........I just gotta wonder.

Bird

 

[rocks]

I have been thinking of using the small port heads on my 94 engine, headers and 410 cam, with some mild port work. Since it is a maf system you could use a SAFC II to control your fueling at wot. Can find them used for cheap. Thats my plan. My motor is all worn out. With 4.88 gears and 35" tires I can hardly climb a small in 4hi. To fast on the highway and it starts pinging real bad. Hopefully the block is still good and I can get away with a small overbored when I rebuild it. I would just like to swap a newer low mileage engine in it but its hell finding a running 4.0 around here in a junk yard.

The other day when I was at the junkyard they told me 400$ for a engine they couldnt guarntee to run. The hell with that. I would pay them 200$ for it just for a core to rebuild.

Rock - I've got a 50k mile shortblock in great shape here that you can have
for $250 picked up - sorry, will not ship. Would be perfect to add a cam and decent heads to...........even have some Jet Hot coated Hedman Headers that I would add in for a small pittance.

Bird

 

[Bird]

I have been thinking of using the small port heads on my 94 engine, headers and 410 cam, with some mild port work. Since it is a maf system you could use a SAFC II to control your fueling at wot. Can find them used for cheap. Thats my plan. My motor is all worn out. With 4.88 gears and 35" tires I can hardly climb a small in 4hi. To fast on the highway and it starts pinging real bad. Hopefully the block is still good and I can get away with a small overbored when I rebuild it. I would just like to swap a newer low mileage engine in it but its hell finding a running 4.0 around here in a junk yard.

The other day when I was at the junkyard they told me 400$ for a engine they couldnt guarntee to run. The hell with that. I would pay them 200$ for it just for a core to rebuild.

Rock - I've got a 50k mile shortblock in great shape here that you can have
for $250 picked up - sorry, will not ship. Would be perfect to add a cam and decent heads to...........even have some Jet Hot coated Hedman Headers that I would add in for a small pittance.

Bird

 

[AllanD]

You, know what I said about "Gears" still apllies but Sometimes you need to look at the problem the other way around...

If the OP has already got 3.73's gears may still be the answer...
but in his case not grabbier, taller. (work along with me here for a moment)

Slightly taller gears will reduce the tendency for wheelspin on "launch"
and let you stay in your lower gears longer...

My issue on my 235/75-15 4x4 is that with 4.10's I can go days
without ever using 1st gear outside of a parking lot... and that's
with the 3.40 1st gear ratio of a factory 4.0 trans...

I "Creep" through stop sign intersection in second without touching
the clutch pedal...

so mabey he's spending too much time shifing because he's geared too short already?

The 4.0 is a "torque engine" and likes something to push against...

Kinda like guys who set-up a 2.3turbo with 3.73's or 4.10's thinking it's
a "Revvy" engine and discovering that a 2.3T is MUCh happier with 3.55's to push against because like most boosted engines a 2.3turbo is a torque engine

Frankly if I really wanted more from my 4.0 I'd go with the "Blue bottle" method.

AD

 

[wahlstrom1]

...kinda like my 37's with 4.56's. I like it better for most driving now because I don't run out of rpm so quick and if anything I think it's quicker overall then it was with 35's.

 

[rocks]

Heh I would buy that shortblock from you if it wasn't 450 miles away. Hopefully something will turn up here in the next year. My engine should last at least that long i think.

 

[Bird]

Heh I would buy that shortblock from you if it wasn't 450 miles away. Hopefully something will turn up here in the next year. My engine should last at least that long i think.

1 day drive down, spend the night here at the house and 1 day back - $400 total for the shortblock and headers - it's a win/win.

But, I do understand............

Bird

 

[rocks]

I will keep it mind. I have to rebuild the front end before I would even feel safe driving it that far.

 

[Madracingalley]

AllenD. My issue on my 235/75-15 4x4 is that with 4.10's I can go days
without ever using 1st gear outside of a parking lot... and that's
with the 3.40 1st gear ratio of a factory 4.0 trans...

I do that too!!! except i have a 2X4, with limited slip....

2nd gear off the line blows off hyundais...
Then, I shift to third........

I do like the 4 Liter engine, even stock, since it has exceptional torque in the lower rpm range. And I have learned that having too much flow out the exhaust isn't always the best. the 4 Liter seems to like a little backpressure (hence the reason i pulled the flowmaster and replaced it with my old sidepipe)

I tend to leave stuff inside alone (To factory specs) because, thats the way it was designed to run.... although my truck is a mess.. it would probibly run better if i replaced half the bad sensors in the motor

I may have to go to 2:73s when i have to drive it back and forth to Ohio... But at least thats all highway. not stop and go. (so I can cruise at 70 without being at 4 thousand rpms.......)

I hate emoticons but they work so well....
~Fish

 

[94redranger]

I used to want the same thing from my 4.0 ohv. I was going to put '95-'97 cast heads with '94 pistons to bump up the compression. I also had plans for a 410 or 422 cam (of course with the 422 cam you have to get longer pushrods, valve springs and what not). As well a pcm tune bigger tb, maf and injectors. BUT then I thought wait, why put all that time and money into a motor that isnt too impressive to begin with and not have anything too impressive when done. Im not saying that when the 4.0 is done up like I said above it wont be fast but there is an easier and better way...V8
Think of it like this; V8 have more displacement which is a no brainer. They also have 2 more cylinders firing on every rotation giving you more power right there.
Now if you want to stay with the 4.0 thats all right if you got the time and money search here and RPS and you'll find some good stuff. It would be a fun truck with those mods. If you really want to kick some ass turbo or super the 4.0 if you have the knowledge. But i personally believe V8 the way to go especially with a 5.0 thats a motor with alot of experience and thousands of performance parts available for it!

 

[turbo cat]

One easy cheap method of gaining power on a 4.0 ohv is a turbo. I spent no more than 200$. My setup is no where close to ideal but it is what it is. I used a very tiny turbo that will spool up super quick which helps make a great torque curve. I didn't see too much power gain (est 40hp) but factors like only an FMU to adjust AF. I also still don't have an intercooler and the motor has some miles and is completely stock from TB to pan. The 4.0 ohv bottom end is strong as a bull. The main issues are stock oem heads that crack and HGs. Ive had my share of both NA and boosted. On the dyno I did lay down 250 ft lbs @ 5lbs of boost on a 4wd 5spd setup. Oem specs were supose to be 175 ft lbs crank power if I'm correct. On the road its a different story I can now pass when I need to. SHow the local diesels I can keep up and take hills easily riding a honda's ass. Oh and Im also using the stock exhaust manifolds.

 

[Bird]

Last run on the dyno that I had with my 'moderately' built 4.0 OHV with 5# boost was 255 rwhp / 318 rwtq with over 200 lb/ft rwtq from 2200 rpm up to the stop of the dyno pull (5200 rpm). This was on a Mustang Dyno (loaded cell) with a very mild tune for normal everyday driving - regular DynoJet numbers would have been 10-12% higher. That truck was an absolute beast with 3.73's and still super responsive with 3.08's - wish I still had it...............

Bird