Exhaust System sizing for a 7.5L Ford E350

[fortee9er]

I have a 1996 Ford E350 with a MFI 7.5L V8. This monster is renown as a gas guzzler and I am researching ways of improving gas mileage while making it more efficient and getting more power. One of the things I am considering is installing headers and a new exhaust system. My question: Is a Y pipe feeding into a single exhaust pipe just as efficient as running duals with an X pipe? Because of the undercarriage packaging the exhaust pipe(s) have to run on the passenger side. The large gas tank sits on the driver side inside the chassis rails. SO there are some packaging constraints.
What size tubing should I use if I use the Y pipe single exhaust pipe?
Thank You

 

[Tmoose]

What gas mileage are you getting?
What transmission?
Do much highway driving? What is your highway cruising mph and , rpm at that mph?

 

[MikeHalloran]

WRT exhaust pipe size, as big as you can fit, allowing clearance for vibration and such.

Headers will help measurably, if you measure with some precision.
Whether they will fit in an Econoline is a different question.

The biggest improvement in highway mileage can be had by getting the cruise RPM of the engine down. Your monster would probably have no trouble cruising at 1000 rpm. Ways to get there include:

Change axle ratio, lower numerically.
Add-on overdrive in the driveshaft
Substitute a later model transmission, one with lots of gears, at least two of which are overdrives.

Before doing any of that, take care of any related maintenance issues:
Put in a clean air filter element.
Make sure that if your transmission has a lock-up clutch, it's actually locking.
Make sure that if your radiator fan has a clutch, it's actually unlocking.

You might convert to electric radiator fans; they will save power even relative to a working clutch fan.

I'm not a big fan of aftermarket cold air intakes.
When you install one you'll discover the annoying resonances that all the funny looking tubes in the stock intake were designed to suppress. Don't destroy or lose the stock parts; you will want them back.

I'm also not a fan of washable air filters.
... mostly because you won't wash them often enough.




Mike Halloran
Pembroke Pines, FL, USA

 

[GregLocock]

I'm not convinced that any mods to the intake will do much for fuel economy, even cleaning the air filter. Reason is that is it sized for full power operation. Hopefully someone striving for economy is nowhere near redlining the engine. The biggest intake depression I've seen across an entire production intake system at full throttle was of the order of 1/2% of atmospheric pressure.

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

http://eng-tips.com/market.cfm?

 

[fortee9er]

I will try to answer all your questions:
Current gas mileage - The van is new to me so I can speak from experience but what I have read is 8 mpg - 12 mpg. If I can get the intown mileage up into the double digits that would be a success.
Transmission - As far as I can tell it is a 4R70W. Gear ratios published:
First: 2.84 :1
Second: 1.55 :1
Third: 1.00 :1
Overdrive: 0.70 :1
Reverse: 2.32 :1
Highway driving - I bought the van to haul car parts, motorcycles, tow a trailer with a car, and occasionally as a vacation vehicle on long road trips.But most of the time it is freeway driving in town. Speed, whatever the traffic will allow. On Interstate road trips usually 70 - 80 mph. I am basing this on experience but not with this van.
RPM ??? van doesn't have a tach.
My hope is to achieve my mpg goals by tuning and bolt-ons nothing radical. So no add on over drive, rear end changes, transmission swaps...etc.
My plans include:
Aluminum radiator with electric fans, bigger throttle body, playing with the ignition timing, adjustable fuel pressure regulator, and the aforementioned headers and exhaust. If available some ECU tuning via a chip or a hand held tuner such as SCT.
At the moment I am taking care of basics: Mobil1 oil and filter, new air filter, flushed cooling system, new brake master cylinder, new battery, new fuel filter...etc.
Air intake mods is an interesting question. If I had my drudders I would like to have an air box like on my F150. There is space for one , the space normally occupied by the second battery on diesel vans. The problem is that the throttle body sits so far back that Ford used two 3" hoses to route the air from a smallish air box sitting atop the radiator. The air box gets the air from the space betwwen the top of the grill and the hood.
The van is a 1996 E350 Club Wagon Chateau with the 7.5L. It has 53k miles.
Thank you for taking an interest in my project.
Jorge

 

[gruntguru]

"My plans include:
Aluminum radiator with electric fans, bigger throttle body, playing with the ignition timing, adjustable fuel pressure regulator, and the aforementioned headers and exhaust. If available some ECU tuning via a chip or a hand held tuner such as SCT."

Regarding the potential for economy improvement:
Aluminum radiator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . No benefit
electric fans. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some benefit
bigger throttle body . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . No benefit
playing with the ignition timing . . . . . . . . . . . . . . . . . . . . . . .Possible benefit
adjustable fuel pressure regulator . . . . . . . . . . . . . . . . . . . . Possible benefit
headers and exhaust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Some benefit
ECU tuning via a chip or a hand held tuner such as SCT . . . . . Significant benefit if done properly. Be aware of emissions implications.

je suis charlie

 

[Tmoose]

The Fords I've dealt with lately have good info like original axle ratio on the build sticker on the door frame.

http://www.ford-trucks.com/forums/297637-rear-axle-ratio-codes.html

 

[fortee9er]

Tmoose - thanks for that info that will save me from crawling under van and looking for the tag on the diff.
Gruntguru- thank you for your comments. I agree that some of these upgrades, such as the aluminum radiator, will not help gas mileage.

 

[JayMaechtlen]

ECU/OBDII interface with data display on a smartphone or cheap tablet.
That takes care of tach and most other instrumentation.


Jay Maechtlen

http://www.laserpubs.com/techcomm

 

[BrianPetersen]

Biggest potential fuel consumption benefit ... Slow down.

Next biggest ... Aerodynamics. You are driving a barn door. Problem is that this requires a different van. The one you're driving was designed in the 1970s with no concern for aerodynamics whatsoever. The Fiat Ducato (a.k.a. Ram ProMaster) apparently has a drag coefficient of 0.31.

Next one ... the engine itself. Your Ford 460 is an engine design that dates back to the 1960s. There's a reason they changed over to the "mod motor" a year or two after yours was built. The newer engines make more power despite being quite a bit smaller.

 

[MikeHalloran]

Yeah, but only 53k miles in 20 years. ... I'd have bought it, too.

Per Jay's suggestion: I've got a BAFX Products Bluetooth OBD2 scan tool.
With the Pro (paid, cheap) version of a phone app called Torque, it shows you lots of useful stuff, and the combo is cheaper than a traditional add-on tachometer.

Agreed about the aero.
If your running boards have mud flaps on the ends, consider removing the flaps.
Also think about a modest chin spoiler.

You've got the wide-ratio transmission already, and it looks like not much else fits, so I might take a look at a taller (lower numerically) ring and pinion in the axle.

... depending on how heavy a load you tow, some moderation is advised.
For a long time, I had a high-top Chevy van with a 2.70 (!) axle. It could pull an 8' U-Haul, but I don't think it would like pulling a big boat.

If you're already running a 3.55, then the most bang for the buck is probably a GearVendors Over/UnderDrive,

https://www.gearvendors.com/f2wd4s.html

... which may cost more than you paid for the van itself.



Mike Halloran
Pembroke Pines, FL, USA

 

[fortee9er]

You guys have been great with your comments and suggestions, which I plan on following up. But we have not really touched my original question about exhaust pipe sizing.
As of this moment it looks like the only headers available, for my van, are the Doug Thorley Try Y headers here are the specs:

Header Style: 4:2:1 Tri-Y Headers
Material: Steel
Finish: Silver Ceramic Coated
Weld Up: Yes, adapters must be welded to exhaust system
Primary Tube Diameter: 1-3/4"
Primary Tube Gauge: 14 Gauge
Collector Attachment: 3-Bolt Flange
Collector Diameter: 2-1/2"
Tuned: No
Flange Thickness: 3/8"
Bolts and/or Studs Included: Yes
Gaskets Included: Yes
Reducers/Adapters Included: Yes
Y-Pipe (Crossover) Included: No
Y-Pipe Inlet Diameter: N/A
Y-Pipe Outlet Diameter: N/A
Catalytic Converter(s) Included: No
Quantity: Sold as a Pair
CARB E.O. #: D-540-5

What size piping should be used for the Y pipe and rest of the exhaust?
Thank You

 

[BrianPetersen]

Realistically, that engine isn't very powerful for its size.

2.5" exhaust pipe, matching the header/collector outlet, is more than enough for what you have. Even after the two headers join into a single exhaust, it's enough for what you realistically have.

 

[fortee9er]

Agreed! By today's standards I'd be looking for 100hp per liter which in my case would translate into 750hp. But that is not what I am looking for. The name of this game is gains in mpg and torque.