Making a 6000 mile trip soon, looking to improve EGT's and/or mileage

Bersaglieri

Bersaglieri

Ron Swanson's Brother
Joined
Jan 8, 2008
Messages
1,957
So I'm towing my car to a drag/cruise/show event and have been trying to find the sweet spot on my combo for mileage. My girl wants us to take her 7.3L F350, but I'm not as familiar with it and we'd have to buy her a hitch. If something happens with the 12v over the road I know I can fix it. However her truck can nail 23mpg empty at 65mph.

On topic, from what I've seen it's a delicate balance between power/boost/fuel to have the nuts to tow up hills, keep EGT's in check, but also not drain the tank so quick.

I plan on keeping the RPM's right at 1800, which seems to put the engine under the perfect load and reasonable speed with 315/75/16's. Now at 1800rpm what's the theory? Should I try keeping boost as low as possible and just tune the fuel to have good power or cut fuel way back? From what I've seen adding low end fuel so you can keep your foot out of it works well, at least at 4500ft above sea level. When I had a heavier AFC spring, housing back and smoke screw out the truck needed more pedal to maintain 1800rpm, I since put the stock AFC spring in, moved the AFC forward, and turned the smoke screw in 1/2 way and now I can barely touch the pedal to stay at 1800rpm, the truck just seems to have an easier time running. It also seems to get better mileage with my 70/30 highway/city mix.

The trip wasn't bothering me unitl the fuel prices shot up, now I'm talking about drafting semis the whole way, haha.

Setup:
180hp 12v
HX35-14/HT3B-26
5x.014
Built 47RE
4GSK and 0/100/5 plates available
60lb valve springs
Ported exhaust manifold and HX35 housing
Stock timing :doh:

How much is stock timing hurting me? I worry about the head gasket increasing the timing, but I'd be willing to do timing and head studs before I leave if it would help alot... it's just one of those things I haven't got around to since I've been building this car for two years. I also considered tossing a camshaft in there, something in the 17X/21X range...

PS It's a 3300lb car on a 20ft long low deck gooseneck.

-Dustin-
 
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I would take the timing up to 18 for mileage. I got my best MPG to date at 21* and i got 21.8 so almost 22mpg.

It varies though, my buddies truck at 18* gets 20's consistently. So i would play with the timing a bit to see how it effects your truck.
 
A timing bump and a cam would both help. Remember that lower EGT and boost numbers at cruising speed makes less fuel being burned. Also with the AFC spring, too light and you get into the fuel too soon and kills MPG, too late.... You have to hold the skinny pedal too much.

Depending on where you are at rpm wise at speed, is where you wanna time to. Stock bolts have handled 17 and 18 DD's but with twins already and depending on your setup, you may want to throw studs at it. Now once again, what timing works best for MPG on a 4.10 truck, might not work as well for a 3.54 truck.

So 18* may be out of optimum for a 3.54 with 315's, but might be perfect for one with 315's and 4.10's
 
sh13lds21 said:
isnt 18* a little high for towing?
Click to expand...

Nahhhh! Ive towed at 21* and it handled it just fine.

dieseltech8100 said:
A timing bump and a cam would both help. Remember that lower EGT and boost numbers at cruising speed makes less fuel being burned. Also with the AFC spring, too light and you get into the fuel too soon and kills MPG, too late.... You have to hold the skinny pedal too much.

Depending on where you are at rpm wise at speed, is where you wanna time to. Stock bolts have handled 17 and 18 DD's but with twins already and depending on your setup, you may want to throw studs at it. Now once again, what timing works best for MPG on a 4.10 truck, might not work as well for a 3.54 truck.

So 18* may be out of optimum for a 3.54 with 315's, but might be perfect for one with 315's and 4.10's
Click to expand...

Ive always though of it this way:
More rpm = higher timing for optimal performance, guys running lots of rpm have pretty high timing right? So running stock 13* or whatever at 1800rpm wont be as efficient as 1800rpm at 18* (im just generalizing).

The best mileage i ever got was with 21* timing cruising at 70mph.

As for egt's more timing slows the needle down a bit. A cam will help quite a bit in my opinion.
 
Biggest thing I've noticed for mileage is fresh injectors. Made a huge difference on my truck.
 
Looks like timing is a good route, I have 3.54's and 315 tires.

-Dustin-
 
Fresh u-joints, good synthetic lube in the transfer case, synthetic lube in the tranny, and light weight 75w90 in the differentials all help with fuel economy.

If you aren't towing heavy, you can pick up fuel economy by running Rotella T-5 10w-30 semi synthetic motor oil.

Be sure to go over your brakes and make sure you aren't dragging a caliper or rubbing in a rear drum.

Verify alignment is true.

Exhaust leaks before the turbo kill mileage. Boost leaks also hurt fuel economy.
 
If you haven't retorqued your stock head bolts to 125-130 ftlbs. you could do that and feel better about bumping up the timing.$.02
 
Most of the typical maintenance stuff is kept up on, gotta check the brakes.

I've been wanting to do a retorque, but I'm undecided on whether to pull-lube-torque or just torque em down more.

Timing 17 degrees?

-Dustin-
 
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If your pull any kind of sizable hills, your going to be making some sizable boost. My vote would be pull the head, install studs, & a new headgasket. I wouldn't want to have to replace a HG away from home. And timing 16-18 will work fine for your intended RPM use @ 1800.

liteweight
 
liteweight said:
If your pull any kind of sizable hills, your going to be making some sizable boost. My vote would be pull the head, install studs, & a new headgasket. I wouldn't want to have to replace a HG away from home. And timing 16-18 will work fine for your intended RPM use @ 1800.

liteweight
Click to expand...

If I was in Dustins situation, I would rather re-torque a seasoned head gasket, than a new one with studs.

The old gasket isn't going to relax much with more squish on it. A new gasket will relax quite a bit.

Studs aren't as elastic as stock bolts. So if the gasket relaxes the stud will lose clamping force before the bolt will.

Studs and a new gasket are probably the best choice here, but not in a short time frame, where multiple re-torques are needed for optimum holding.

On edit: One more vote for timing.
 
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I've even thought about going down to 5x.012's. I'd like to do a cam, but I probably don't have the time to throw one in before I leave. Even thought out whipping up a quick dual horn intake or something to help improve VE.

-Dustin-
 
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