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.

 

[tgreene92]

quick or fast, my 4.0 is neither i think its a slug of an engine. has good pulling power but my ex is pretty darn slow. it prob could use a little touching up tho to bring it back some life

 

[Hitchhikingmike]

Well, I am more so wondering how did Ford compensate for the VLIM? Do you know how ford was able to keep the horse power above 200 without the VLIM?

 

[CDW6212R]

Well, I am more so wondering how did Ford compensate for the VLIM? Do you know how ford was able to keep the horse power above 200 without the VLIM?

I don't think it helped much on the SOHC 4.0, the intake is too restrictive as it is. If the entrance and path to the "VLIM" was much larger it might have had a chance to help more.

Ford has been playing around with long runner intakes since fuel injection began in 1986. If you pay close attention to more recent intake designs, they are becoming much shorter and larger internally. Ford is finally learning(but still too slowly), how to design camshafts to work with larger and shorter intakes.

The opening of the intakes is much larger than ever in the past, check out how small 3.5-4.0 liter engines come with 65mm to 80mm throttle bodies now. That's part of the progression to bigger power, lessons learned by professional engine builders, and OEM eventually begins to pay attention.

That's why the new generations of Mustang have been so much faster than ever. It's the same basic 4.6 shortblock they are working with, but the heads and intake flow far more than the 1990 versions. They are shortening and opening up the intake path with bigger ports, and camshafts to match those needs. With better breathing the stroked 5.0 version is worth doing, it wasn't before with the old intakes and heads.

 

[Kainon]

The following statement is Reversed but is correctly shown in the picture.

This system is a computer controlled variable intake runner, during normal operation air is routed through a longer intake runner for low RPM torque, under 3/4 to WOT the comptuer opens a butterfly at around 3k RPM's to allow air to be routed through a shorter intake runner, for high RPM horsepower.

The longer intake runner helps with High RPM, Short Runners for Low RPM.


Question: will a faulty VLIM cause a lean miss fire at and above 3k? or is the section sealed from sucking in non-monitored air ?

 

[Jakee]

The following statement is Reversed but is correctly shown in the picture.

This system is a computer controlled variable intake runner, during normal operation air is routed through a longer intake runner for low RPM torque, under 3/4 to WOT the comptuer opens a butterfly at around 3k RPM's to allow air to be routed through a shorter intake runner, for high RPM horsepower.

The longer intake runner helps with High RPM, Short Runners for Low RPM.


Question: will a faulty VLIM cause a lean miss fire at and above 3k? or is the section sealed from sucking in non-monitored air ?

Well, since we're on the subject again.

Yes, No...

The underlined statement is correct. Longer runners are good for low RPM torque, short runners are good for High RPM HP. The range is shifted from one end to the other depending on the runner length. So someone was trying to get the best of both worlds. Not a bad Idea in theory but I wonder why they stopped that. Cuss mine doesn't have the variable runner valve.

 

[FIND]

Well, since we're on the subject again.

Yes, No...

The underlined statement is correct. Longer runners are good for low RPM torque, short runners are good for High RPM HP. The range is shifted from one end to the other depending on the runner length. So someone was trying to get the best of both worlds. Not a bad Idea in theory but I wonder why they stopped that. Cuss mine doesn't have the variable runner valve.

To clarify, the longer runners are for creating higher velocity intake air at low RPMs. The short runners are just to increase the volume of air that the engine takes in at higher RPMs where it needs more air.

 

[CDW6212R]

Please don't use the word velocity like it's a special goal for engine flow. Anyone can make the passages smaller and thus force higher velocities. The goal is always airflow, efficient airflow. Avoid using the word velocity ever regarding engines, it's misused most of the time.

Longer runners work better at low rpm's with the given cam specs. I don't know how else to describe that but that's as close to what's going on as I can say. A cam can be made to produce the same or more power for a short runner intake at low rpm, as the stock cam. The stock cam is a factory compromise, not ideal given today's cam design technology.

Ford made those variable runner intakes for a couple of engines in the 96-98 models. Most common was the 96-98 Cobra 4.6 DOHC engines, but they decided that the reliability and trouble which people had over time was not worth it. Since the change back to single intake ports per cylinder in 1999, they have improved continuously. The newer DOHC models make better low rpm power and they have shorter runners. It's in the cams and port designs, not higher velocity. Regards,

 

[Kainon]

doesnt answer the question but thanks anyway.

also you guys need to look at the pic ( if its factory ) .. long intake runners have always helped High RPM not Low RPM. but what ever.

 

[Jakee]

doesnt answer the question but thanks anyway.

also you guys need to look at the pic ( if its factory ) .. long intake runners have always helped High RPM not Low RPM. but what ever.

Let's not confuse people here. Do an internet search and this question will be answered several hundred times. I'll help you out with this one link.

http://www.wallaceracing.com/runnertorquecalc.php

 

[rokr1292]

I wish ford would make a 4.0 Ti-vct, that'd be amazing, both for power and efficiency

 

[Mannybeltran]

Agreed

Yeah I don't know about fast mine can hold its own. But as soon as I drive my 325i fast becomes a reality.Good trucks and I am also looking for more speed and power any tips where to start?