4.0 SOHC Seriously fast?

My 98 4.0 SOHC is really fast. Are they supposed to be fast? I have whipped up on a lot of cars and trucks trying to race me.

Seems like the thing has endless gears compaired to my 4.0 95 EB and my 01 Expedition 5.4.

I hit the gas and it starts going into passing gear, but if I hit it again it goes into a higher passing gear and just kicks azz is this normal or did someone put a tune on this thing?

I know it is all set up for towing and the towing rack in the back is huge and meant for hauling something big and the it even had what looks like after market oil and trans coolers.

Anyone have any ideas? I got this truck used.

 

[CmdrPopNFresh]

what!? i didn't know they had that! i thought that was just v-tec hondas (and others a like z-tech, t-vis, etc)

not quite the same thing. v-tec has to do with the intake valves them selves. when you go into v-tec an oil acctuated solenoid activates another larger cam lobe on the intake cam and gives the intake valves more lift...or duration...i dont remember.

on the sohc the intake manifold has valves inside of it that open and allow air to travel into shorter or longer tubes for more volume and equal lengths.....like on the sho taurus. even my 01 escort has a similar system on it.

 

[SVO]

Actually, one of the layman definitions I just gave has a flaw in it. I challenge someone to find it.

Torque is the term used to decribe a roating force that may or may not result in motion.

Mesured in pound feet.


Work is defined as actually accomplishing movment when torque is applied to an object.

Mesured in foot pounds.


Power, the term power means the rate at doing work. Power equals work divided by time.

Expressed as foot-pounds per minute.


Horse Power, One horse power is the power required to move 550 pounds 1 foot in 1 second, or 33,000 pounds 1 foot in 1 minute, this is expressed as 500 foot pounds per second.


Horsepower = (torque * rpm) / 5252



Altitude for every 1000ft of altitude you loose 3% of power (N/A), not so much with boosted engines, as they make positive displacement.





Jeff - :navajo:

 

[SVO]

I don't think SVO was saying that is the optimal shift point, but it is a good place to start, the only real way to find it is making passes at the track and seeing what makes for the fastest e.t.

This is a goo place to start, but by no means is it the most optimal place to be, gearing both in the transmissin ans rear axle has a lot to do with the actual shift point effectiveness.

Your results may vary :




Jeff - :navajo:

 

[CDW6212R]

The Ford intake parts mentioned to aid power at low rpm or high, depending on the solenoid/valve, that was prior to 1999. Ford started that with the 96 Cobra DOHC, and it lasted until 1998. After a lot of issues and better development of a traditional single intake path, that concept was dropped. The 1999 versions of those engines perform just as well, so don't go out hunting the old parts. Use what you have, the 96-98 odd stuff is problematic.

FYI, power does not determine acceleration or real 1/4 mile times. Torque combined with RPM does, and that is not measured on a dyno. Thus you cannot race dynos. An engine with less dyno power can very often spank a somewhat more powerful(dyno) engine, at the track.

Concentrate on gaining rpm acceleration much more than power. Example, stronger valve springs do hurt dyno power, but they give better valvetrain control, and thus acceleration. Concentrate on the heads, camshaft, and valvetrain.

The SOHC 4.0 has those better parts, thus it's much better than the OHV 4.0 for performance.

 

[SVO]

The Ford intake parts mentioned to aid power at low rpm or high, depending on the solenoid/valve, that was prior to 1999. Ford started that with the 96 Cobra DOHC,

DOHC 4.6 Lincolin Mark VIII , pre-curser to the DOHC Cobra motor, with electronic vacuum solenoid actuated (by the PCM) IMRC till 1996 then it was electronic cable actuated (again by the PCM).








Jeff - :navajo:

 

[SVO]

A set of IMRC delete plates I modified from a Cobra DOHC, the car did suffer on the bottomend of the rpms, I put boost on it, then it still suffered but not near as bad, it was a 10hp gain with the removal of the rods and plates.

I think I would have kept the lowend drivability myself, but I get paid to do what the customer wants, not what I want.

Jeff - :navajo:

 

[CDW6212R]

Oh yes, the Mark got it first. I think it was a great idea, but Ford always builds crap heads to start with in a new engine design. The heads needed tons of improvement from the start. The IMRC intake design was very likely not a problem, because the heads were not good enough. Any modern DOHC performance engine should be capable of making 1hp per liter, without boost. Ford failed at that in a big way, which is why the boosted and pushrod engines still do most of the work.

 

[SVO]

Any modern DOHC performance engine should be capable of making 1hp per liter, without boost. Ford failed at that in a big way, which is why the boosted and pushrod engines still do most of the work.

Fully AGREED!





Jeff - :navajo:

 

[Jakee]

Yes. This guy knows a thing or two. You can have all kinds of torque going out but if there’s no HP then you're not going anywhere soon.

The track is not the only place to find your shift points - there are other ways, but the track is the best place to open things up; that, I'll agree with.

Then again, I know everyone on here wants to bug me about getting mine to the track and that will come someday. What I'm doing is attempting to get as close as possible to optimal, where I have time to do it, then I'll be ready to get to the track. There will still be adjustments but I'll be a lot closer to the best possible time. - I feel like a broken record here.


Some of the 4.0 SOHC don't have the VLIM. Mine doesn't. The main reason the sport models with the 4.0 SOHC are quicker and faster than there brothers and sisters is because of the weight of the vehicle; work can get done faster.

CDW - "power does not determine acceleration or real 1/4 mile times." Not alone it doesn't. We know this because a heavy vehicle will not go as fast or as quick as a lighter vehicle with everything else equal. And gearing and drive train losses play another factor. Then there’s the wind, the temp, the condition of the track…..ect.

There are so many variables that the best thing to do is get to the track. But if there were some way to factor in the entire variables then I think it could be done - It’s just insane to try and do that.

I went to the track a few months back watching the "big dogs" run. One of the things that stuck in my mind was the announcer saying how important it was for these guys to get down the track the very first run. The reason for this is for a complete data set. Without the data they wouldn't know what to adjust to get optimal results the very next run. Data is very important and not just the times you’re getting at the end.

 

[CDW6212R]

Jake, my power comment was aimed at the countless people who only look at a dyno figure. Regardless of a vehicle and conditions, a lot of people think that any engine with 350hp will post an identical time to any other 350hp engine(in the same vehicle).

I was hinting that there are engine factors which affect greatly the acceleration of the engine from low rpm to redline. It is common for the pros to have less power but much quicker acceleration, than an amateur who just shoots for dyno numbers. There are a lot of myths(or mediocre parts) which may produce HP numbers, but do not help at the track. I believe I have located a few of those pros who have a lot of that figured out. Let's not go any more off topic, I'm sorry for my part in that also.

The SOHC 4.0 is a great engine, the heads flow very well for a two valve head. There may be very nice gains to be had with custom camshafts, and/or an open plenum intake(carb style).

 

[Jakee]

I'm not upset in anyway and I hope no one else is. I don't think we're off topic here; we're talking about fast and quick and what the definitions are and so on.....ect.

I know what you're trying to say and your right.

For the dyno chart posted - and just by looking at it and nothing else, if that motor was able to spin 6 grand with no problems then that's where I'd shift at to start with. The reason why is because when the tranny shifts it'll be closer to the peak HP and I believe this would give you an RPM band with the highest average HP thru second and third.

 

[CDW6212R]

FYI, most OEM tachs are inaccurate. I do not know how accurate the OBDII PCM data is, but it is a good bit lower than the tach. My Scangauge records highest rpm reached, and once in a while I go through WOT and watch the difference. Just today I went into 3rd gear at WOT, the tach hit close to 5500rpm both times. The OBDII data suggests only 5020rpm was reached. I've seen the tach hit virtually 6000rpm a few times, and the OBDII hit over 5500rpm. I need to get with James and have some tuning done.

It sounds great doing it, but I always worry about the trans. This is my work truck, so it's important. I'll likely be hitting a true 6000rpm with my 347, given the shift start and actual shift event. I wonder if the tach can be calibrated.

 

[Jakee]

I think it can be set closer but the true way to do this is the acceleration rate and not RPM’s. One thing that wasn't adjusted in my tune was the PCM trying to calculate shift points based on RPM’s. Doing it this way, and stock this is the way it’s done on my truck, is not good once you start building more power. My truck would actually hit the rev limiter in second because the PCM freaked out with the RPM’s racing so fast. The best way is to properly calculate NV on the tranny; make sure the gears are right; the RevsPerMile is correct and then set the switch to use MPH to trigger shift points. There are a couple more adjustments to make this correct but it says this is the proper way in the SCT software.

 

[CDW6212R]

Okay, so the MPH is a piece of data which the PCM can keep up with better than the rpm? Could that be because the PCM anticipates, or that the adjustment of MPH is rougher, and thus you can narrow it to what you want easier?

 

[Jakee]

Yes

There is a setting inside the tune that's called "Switch to use RPM Anticipated shifts". From the factory this switch is enabled. SCT says, "This switch, if set to one, tries to use engine RPM acceleration rate to determine when to command the shifts. This is not a very good way and this switch should be shut off, so that only vehicle speed acceleration rate is used." I shut this off so it wouldn’t use it.

“At WOT, the trans shifts based of one of two things, whichever one happens first. Either the vehicle speed that is in the shift schedule functions or the WOT engine speed scalars,”

By shutting off the first scalar and maxing out another you force the MPH table to be used and evidently the PCM can react faster with the MPH vs the RPM. It makes sense when you watch both gauges and how quickly they increase compared to one another. It would be easier for you to quickly guess the MPH at a certain time when accelerating.

As for RPM's being off and not to trust them - there is a lot of things inside your PCM that are using this data to calculate when to do things. You’re stuck with the RPM factor so it’s best to make sure everything is setup right in the tune so the RPM’s will be as close as possible.

Bottom line, use MPH to anticipate shifting vs RPMs.

 

[CDW6212R]

...
As for RPM's being off and not to trust them - there is a lot of things inside your PCM that are using this data to calculate when to do things. You’re stuck with the RPM factor so it’s best to make sure everything is setup right in the tune so the RPM’s will be as close as possible.
...

That's good information. My comment about the tach being inaccurate was about the tach, not the PCM. I'm telling people to not trust the tach, just because it says you reached 6000rpm does not truly mean that. I'd like to be able to calibrate the tach sometime later to be more accurate.

 

[Jakee]

Roger that, I see what your saying.

 

[compdoc777]

Yes, what I am saying is the SOHC is fast for what it is in the Explorer. It seems to motivate the truck quite well.

I have a new problem though. My performance seems to have dropped off as well as my gas mileage. I went from about 17 MPG to 14.5-15 MPG and when I accellerate it seems to lag a little now. I replaced the sparkplugs and the wires and the fuel filter runs a bit better, but still laggy and the same MPG.

 

[contrail]

http://www.youtube.com/watch?v=RfrWSCaD0nI

thats my bone stock explorer doing the 0-60 thing in 7.2 seconds
... not "fast" but definitely quick enough to wax the average car.

 

[aklmfreak]

http://www.youtube.com/watch?v=RfrWSCaD0nI

thats my bone stock explorer doing the 0-60 thing in 7.2 seconds
... not "fast" but definitely quick enough to wax the average car.

very nice, gotta love the way that 4-oh purrs

i think if you consider the class of vehicles the Ford Explorer is in, the 4.0 SOHC is crazy awesome. beyond all the numbers and statistics i dont think anyone can deny that the SOHC makes our 4000lb SUV's loads of fun to drive compared to similar vehicles

i've done a little suspension work to mine to make it corner better and i get a kick out of driving it every day! its ridiculously agile considering the kind of vehicle it is. my father says i drive it like a go-kart, lol