Completed Project My 98 super charged EX

[4pointslow]

room

There looks to be enough room to run 3 inch pipes from the cats to the back where the spare tire used to be, then the mufflers could be placed under there with short tail pipes.

 

[joecrna]

Isn't exhaust work wonderful. About the only real scientific info available is based on wind instrument studies. Think pipe organ. The rest remains primarily black magic. That and years of experience to get a good starting point. There are a couple books that combine the two. Then test and tune. A very expensive, in both time and money, way to go about things.

"X" pipe is for tuning. Generally this will improve low end power but at the expense of maximum power. Assuming location of the "X" pipe and diameter are correct for the rest of the system. Works good on most street cars and even a few very heavy, moderate power drag cars. Not what I would call all out drag cars. Usually street strip kinds of stuff. On a turbo or SC car, I don't think I've ever used a crossover. They need too much flow.

4point, I tried to look at your pictures of the new system but they stopped just before the muffler. You could "Y" down into one very large muffler but I think your needs are beyond that. Like Don said earlier, if you are running 14psi of boost your 4.0L now needs to flow like an 8L. If Red line is about 6000 RPM, and I understand your system correctly, I'd put two 2.5 inch very low restriction mufflers on it.

I think before I spent anymore money I would measure your backpressure before the cats ( I think you already did). Then unbolt the muffler and measure the "backpressure" at the same location as before.

 

[4pointslow]

Dual Exhaust

I am going to stop by the exhaust shop again and see what they can do.
I did some cutting of a heat shield that is over top of the tail pipe, looks like I may be able to get two 3 inch pipes over the rear and then mufflers all the way at the end of the exhaust. Trying for 3 inch in and out.

I did measure back pressure after the cat and before the muffler (8-9lbs).
I have a flow master with two inlets and one 3 inch outlet on it now.

I am happy with the front pipes and cats I had installed, they are much bigger and will flow better than the stock ones that were on there. I was just surprised to see how much back pressure was before the muffler.

 

[CDW6212R]

I am going to stop by the exhaust shop again and see what they can do.
I did some cutting of a heat shield that is over top of the tail pipe, looks like I may be able to get two 3 inch pipes over the rear and then mufflers all the way at the end of the exhaust. Trying for 3 inch in and out.

I did measure back pressure after the cat and before the muffler (8-9lbs).
I have a flow master with two inlets and one 3 inch outlet on it now.

I am happy with the front pipes and cats I had installed, they are much bigger and will flow better than the stock ones that were on there. I was just surprised to see how much back pressure was before the muffler.

I'm sure that if you get another muffler in there, the back pressure will drop a bunch.

 

[joecrna]

I looked at that muffler for my NA 4.0. Flowmaster claimed it would support 400HP. I assume there is no reasonance at cruising speeds? High flow cats by magna flow are always a good bet. They flow very well. The work your shop did on the pipes and cats looks very good. Nice radiuses and pretty smooth contours.

I'd like to know what your back pressure meassurement is without the muffler attached. Just wondering if you would see a big drop or could the measurement technique be flawed. I personally wouldn't switch mufflers or tail pipes until I was certain that is why I was seeing "backpressure".

Heck, I'd even take it to the track and run it just as it is. Then unbolt the muffler and remove the rest of the exhaust and run it a couple more times. See if there is any real difference. Then make changes as you see fit.

 

[4pointslow]

muffler

Unfortunately the muffler doesn't unbolt. It is welded.
Pressure backs up in front of a restriction.
I used the O2 sensor holes, one in front and one in back of the cats.
Per Ford diagnostics for loss of power, back pressure should not be higher than 8 at WOT under load for a stock vehicle(which usually have somewhat restrictive exhaust anyway).

All the different calculations for choosing exhaust sizing say to use duals with 2.5 to 3.0 inch sizing. So we are talking 5 to 6 inches total. I am sure the one 3 inch outlet is restrictive.

 

[4pointslow]

2.5 duals or 3 inch duals?

I am going to go get an estimate on 2.5 and 3 inch duals to see if there is a price difference. I guess I may have to factor that in.

I would like to hear some opinions on which to use.

 

[Dono]

Go big, or go home.

 

[ahodges]

IMO, dual 3" sounds like a lot for a 4.0L V6, even if it is forced induction.

 

[delexploder]

Dual 2.5 will handle 500 HP, you will destroy the motor before you outgrow 2.5 and on mine I have 18" long tips that are 3" ,I ran it with the 2.5 " tails before cutting them back for the tips and the sound difference was huge , IMO if you go 3" from the cat back it will sound like a dump truck

 

[Dono]

Is there room for 3"? If its the same price(Or very close), why not do it?

One reason might be that it will be louder? More drone on the hwy? Just stuff to think about that the answers are hard to come by.

 

[vroomzoomboom]

like don said. 3 inch is even hard to fit under a fox body mustang, let alone our grocery getters

 

[4pointslow]

Tomorrow

I went to the exhaust shop and spoke to the guy who did my exhaust work. I explained that I wanted 2 estimates, one for 2.5 duals and one for 3 inch duals. He told me they were very backed up and it might take a couple hours to get it in for a look back there. The place was swarming with people and vehicles. I asked if it would be better if I came back tomorrow and he said yes and told me to come in at 8:00 am before they got busy. So that is the plan. Now I have more time to consider the exhaust size.

Tomorrow is supposed to rain so no track time until Thursday (their rain date).
I hope to have the duals done before Thursday.

 

[4pointslow]

3 inch

like don said. 3 inch is even hard to fit under a fox body mustang, let alone our grocery getters

I agree, but....
I have a 3 inch tail pipe already, I made room for another to pass over the rear. I plan to have the mufflers where the spare used to be. See pics.

The exhaust guy may look at it and say, no way, cant do it, or he may say he can. lol.
But yes, it is tight back there.

 

[CDW6212R]

Unfortunately the muffler doesn't unbolt. It is welded.
Pressure backs up in front of a restriction.
I used the O2 sensor holes, one in front and one in back of the cats.
Per Ford diagnostics for loss of power, back pressure should not be higher than 8 at WOT under load for a stock vehicle(which usually have somewhat restrictive exhaust anyway).

All the different calculations for choosing exhaust sizing say to use duals with 2.5 to 3.0 inch sizing. So we are talking 5 to 6 inches total. I am sure the one 3 inch outlet is restrictive.

That muffler size(the housing) looks like it would work turned, with another one next to it. I'm sure using two with a single inlet and outlet is the easiest method. See if the ones you find are the same width as that one.

Measure on your truck how far down from the floor you'd be willing to have a muffler hang, plus the width in there that still leaves space around it for cooling. Then see how you might arrange two turned on their side there, even at an angle if there is more width than height. My friend had our local popular shop do the Flowmasters for his Explorer, but that was way back in about 2004. They barely showed under the truck as I recall.

 

[4pointslow]

That muffler size(the housing) looks like it would work turned, with another one next to it. I'm sure using two with a single inlet and outlet is the easiest method. See if the ones you find are the same width as that one.

I had a tape measure where the muffler is and using the same width as the muffler that was in there(10 inch?), it came down below my traction bars. I don't think it would have looked right. Besides I have all that room under the back where the spare used to be. Also I was thinking there will be more weight added to the truck now, better to have the weight all the way in the back for rear tire traction. And having the muffler at the rear of the exhaust is supposed to be an enhancement.

 

[CDW6212R]

That's good if they will fit where the spare is, I was thinking of how you might need one some day.

I usually fix my own flats on the car without removing the tire, but rarely the tire cannot be fixed. My last one was last year and with a tire warranty, I had to swap it out and take the flat tire to a repair shop authorized to do it and keep the warranty.

 

[4pointslow]

spare

I too usually fix the tires with the wheels on the truck.
I have a tire plugger, plugs, reamer, diagonal cutters, and electric air pump in all 3 of my vehicles. I figure one day my luck will run out and I will have to have a tow.

My ranger has 31 inch tires on it and a space saver spare! I can not even get the spare down, the spare tire lock wont open. I even tried oiling it. I will probably drill it out.

The only vehicle I have a good spare on is my 4 door explorer. lol.

 

[4pointslow]

Still debating exhaust size

Some things to think about

When the exhaust valve closes, the exhuast flow in the pipes(from other cylinders?) causes a vacuum to be created at the back of
the exhaust valve. That vacuum helps pull the exhaust out of the cylinder the next time the valve is opened(and more air fuel can go in). I
beleive that to be exhaust scavenging. To big a diameter(larger area) of exhaust pipe can cause a loss of that scavenging. Think why
an engine's vacuum drops when you open the throttle plate. The engine is still sucking, but the intake is open to the atmosphere, and
you can not pull a vacuum in the atmosphere because it is too large. So I use that logic to beleive or undertsand the effects of
exhaust scavenging and possible loss of it due to "too large pipes". (but maybe that only happens in the headers and front pipes?)

In another thought,
If cam lobe overlap is huge, scavenging can pull air/fuel into the exhaust and it would be wasted (too much scavenging). Not
enough scavenging causes exhaust gases to be left in the cylinder and exhaust gas is not combustable so power can be lost.
Having boost in your intake can add to the huge cam lobe overlap problem also.
I dont have any formulas for cam lobe overlap anyway. Just some thoughts.


I had 290HP at wheels (348 at crank) (plus 75 to drive supercharger if you are supposed to add that)
I now have anywhere from 380 - 455 HP at the crank (304 - 364 at wheels). (455/364 is with 75 hp to drive supercharger)
So question is do I add the required HP to drive supercharger or not?

I have a 3 inch tail pipe (area 6.47) (744 cfm)
a single 3 inch supposedly can handle 337HP (crank)
I was pushing 348 at crank through it. (or 423 if SC added) Definately a restriction.

If I have 10 inches of back pressure and I should have 8 or less, then that shows a restrcition. A small one?
I believe it would benifit the vehicle to be below 8 lbs back pressure, and may not need to be 0.
I dont beleive back pressure is good, but a little of it is a result of having a system not too big to hurt the effects of scavenging if that
makes sense.

Two 2.5 inch pipes have an area of 8.8 (1012cfm)
Supposedly can handle 460HP

two 2.75 inch pipes have an area of 10.78 (1240cfm)
Supposedly can handle 564

Two 3 inch pipes have an area of 12.94 (1488cfm)
Supposedly can handle 674HP

The math makes me think that dual 2.5 would be an upgrade, dual 3 inch might be too much, and a system made with 2.75 inch
would be best, but it is not a common size.
I am looking at some charts on pipe size to HP too, I plan to post them later.

Any input added to this would be appreciated.

 

[CDW6212R]

There is no real worthy scavenging to gain from after the area where the O2 sensors are. In that area of the collector pipes to the trans pan, that's where a theoretical cross over could help slightly with additional scavenging. But you can't put one there for a street vehicle, the trans etc, parts are in the way. That's why the crossovers end up near the back of the trans, where it doesn't help measurably(it does way more for sound than power).

The point is that beyond the collector/pan area, it's all about restriction, reducing it. All back pressure is bad, 1psi is bad.

But the key is how much actual power can you gain from each given size upgrade? Dual 2.5" pipes will be a big improvement over a single 3", but a dual 3" system will not gain the same amount. Each step up will gain something, but less than the last step up. You want whatever the biggest is that can easily be fitted, but how much trouble is that(the power gained?).

If the 2.5" step gains you say 35hp, and the 3" step only gains 10hp more, is the extra 10hp worth the extra work and cost? I don't know what the actual hp figures would be, I just picked a couple of random possibilities. It might be 50hp versus 10, or 25 versus 5 etc.

The choices of tail pipes will also effect the sound, like the mufflers. Adding a muffler should lessen the sound some, with half as much flow going through each as before. But lots of people have learned what certain mufflers and pipes, tips etc, what they did for the sound. So think about the sound too, I'd lean to the mufflers you have heard and liked the most.