You may be right .bob, but I am speaking from mine and others experiences here in the real world, when my turbo went on my mileage began to increase a little and the driving egts were down. To me that is running more efficient and I think the turbo was a big reason for what i have now. I get 21mpg pretty regularly unless towing, and even then its not that bad. Not to mention better heat exchange from engine to turbo. This is just opinion, I can tell you on a 03-04 it is even more important.

I do not have any data, but the fuel burned either goes to the crankshaft, the cooling system or the exhaust system. All things being equal, two trucks side by side going down the road, same rpm, the one with lower EGT is either more efficient or it is dumping more heat in the cooling system since the exhaust is cooler. I guess to be technicaly correct we need to be talking about post turbo temp not preturbo. Obviously one could have high preturbo but very efficient turbine and low post temp. Consider twins, low post post temps.

As easy as it is to heat up air there is probably a lot of temp for little extra fuel required to heat it. But a lower temp would indicate less energy going out the exhaust so it would be taking things n the right direction, just question how measureable which is your valid point.

Good post. I was hoping you would chime in. That hatchback is radical! I bet it works though. Makes that Ford start looking like the insight!

I don't know enough about diesels to make solid assumptions. That's why I said, "I don't see...". I could be wrong, I don 't know.

I'm pretty good with a gas engine. When egt's rise, it's running lean (and that's bad). To drop the EGT's, you add fuel. That makes it run better and live longer, but then you're burning more fuel.

But gasoline and diesel are very differant, so I don't know if that fact translates well. We all know how many people swear a CAI kit has increased their fuel mileage or power levels, but actaul controlled testing proves otherwise.

Sure would like to see some real data.

Bob,

What is the CAI kit??

^^^ cold air intake

Thanks. The subject of economy is no different than that of performance (it IS performance, only with an ending differing slightly). The following is borrowed from two other persons, and I believe sums it up well:


The #1 factor in getting better fuel mileage is to REDUCE HORSEPOWER DEMAND.
This is a combination of vehicle configuration, condition, load and DRIVER OPERATION.

Keep your pyrometer under 600°F and keep your boost pressure under 5 PSI when solo.

The #2 factor in getting better fuel mileage is to
AVOID RUNNING THE ENGINE WHEN YOU ARE NOT MOVING.

Based on years of trying to achieve great fuel mileage off of big gasser V8's (the problems of avoiding detonation while running higher compression off of pump gas with carbs by effective quench heights; short/low lift cam events BUT with big/fast openings from 20-degrees onwards; long highway gears without O/D, etc), it "might" be that, for parts blend:

better intake path, better exhaust path and then playing with turbo and injectors could be the way to go as one wants the least amount of fuel burned to achieve an objective. I'm leery that any of it would work as the aftermarket for CTD cams is too small to warrant this expenditure as a package. If gearing (axle and trans PLUS stall speed [for the kids who insist on automatics]) could be packaged with an optimized intake, intercooler, turbocharger and exhaust manifold, etc, proven to some degree then it MAY be worthwhile. MAY . . .

I could never see the point of going beyond a 14-sec 1/4-mile at 100-mph . . . or, better (more real world) very short 50-70 mph passing times.

I can also see no point in wanting more than 305HP and 555TQ as I find it an incredible combination. "Improvements" in my mind are in optimizing rolling resistance, reducing internal resistance, and in exploring aerodynamics where overall appearance doesn't get too weird (or that can easily be changed back to oem stock). Do all the easy stuff first.

The only real performance is what happens on the big road, solo, or loaded heavy AND towing (up to rated capacity). Exceeding parameters on a beautifully engineered vehicle is pushing other components to early destruction (not economical; poor ownership habits), thus looking to w-i-d-e-n the performance envelope is where these other components are NOT adversely affected AND in a narrow area where performance MAY add to ownership value (being able to pass another driver not moving slowly, but erratically). In other words, I don't want to change from 3.73 to 4.10, BUT I want it to wind hard and fast for a specific, narrow purpose and not burn more fuel during cruise.

One MUST have a specific goal in mind . . . tromp on it ("I shat my didies, Mom . . whoa-wow what a feeling!") isn't a goal.

Steady state cruise is the goal as I see it. Least fuel for most work. Slowing down a little is beside the point. Having a guy ahead of me who can't maintain a reasonable headway due to poor skill/inattentiveness is the only time I "want" more power. It's just easier -- and a helluva lot cheaper -- to get off the road for a break and let him get 25-30 miles onward before resuming.

Best blend of power and economy? Leave earlier.

.

Good info, Rednax. I was reading your signature and wondering how much you think your exhaust is worth? I tried a turbo back 4" straight pipe with the stock resonator on Saturday and it was too loud so I put the stock muffler in front of it. I cannot notice a sound difference with the converter off of it. These were homade welded from pipe and elbows so my cost to experiment was not great, about $80.00 for both configurations.

I put the smarty S06 on it as well and set it at level 5 which is 70 (or 90, I forget) HP over stock and then set the POD (Power on demand) all the way down to 30%. So driving it feels a lot like my '84 F250 6.9 175Hp truck I had years ago. I think it is holding boost and fuel way down like your driving solo suggested. The timing advance should be a plus. I'm going on a trip Easter weekend with no load so will try that setting. It still pulls Tennessee grades on cruise control at 62mph without dropping speed. I think the Smarty is going to teach me how to drive better so later I can open it up and use the power momentarily and then cruise by using driving lessons learned from the reduced power mode.

I was reading your signature and wondering how much you think your exhaust is worth?

When I bought the truck it had a non-resonated AEROTURBINE 4040 with a chrome megaphone tailpipe tip. Nice fun kiddie sound around town, but the drone while towing on the highway was unbearable.

I read around, and found that at that time the ROKKTECH muffler was advocated for lower-than-stock backpressure than the factory piece, was well-made, and was not "louder" than factory, appreciably. The tone was different. The muffler is sort of directional: installed one way and the sound is a bit louder (as I recall).

I also found more than one post (on TDR, I think) where a 4040 was used as a resonator ahead of a ROKKTECH. I took the new muffler and went by a shop and had them:

1] Install the ROKKTECH in the factory muffler position, in the direction of quietest sound.

2] Remove, and reinstall the 4040 as far forward as possible.

3] Remove the chrome tip and replace it with the piece cut out for the 4040, and extend it past the body line. (This may be the single "improvement" vis-vis fuel economy).

When you see my truck it appears to have a school bus exhaust system when from the rear. I like anonymity (to some degree), and I value not waking my neighbors at an 0400 departure. I especially do not want it to sound like the city trash truck that so many on here are in love with.

The engine is louder than the exhaust, at idle. The tone is nice. It may be that having the tailpipe "out in the wind" has helped a bit with exhaust scavenging.

Having two mufflers in the system has proven no detriment to fuel mileage. Both mufflers are well-made, well thought out.

I believe (subject to correction) that the other men in the Southwest achieving consistent 25+ mpg on Gen 3 trucks have stock exhaust systems. Driver skill is the highest determinant, IMO.

The ROKKTECH is not available anymore (I'd still email them to ask); and EDMONTONCANADA indicates that CORSA makes a similar muffler (look for pics of interior of both).

Were I starting from scratch I believe I'd try an EAG (Exhaust Air Guide) hard up against the downpipe, just one foot ahead of a resonated AEROTURBINE 4040XL for starters on an otherwise stock, non-cat system (where the oem muffler is removed).

With a cat I'd email the EAG manufacturer and talk about installation distance behind that piece and (same muffler) placement.

I have also thought about adding that funky CHEVROLET venturi tailpipe to see if there would be any change. The TAG-II is on my list, and I may add the EAG. The three pieces may not make any difference (or, only under certain conditions; towing), but I'd like to see more reports before purchase.

Reducing horsepower demand means, IMO, that the motor be always predictable. The driver works for the motor -- is it's eyes and ears -- and his function is to make perfectly steady state headway possible. It is all a set of questions, problem-solving, about small margins. If the motor starts to call for fuel, boost, etc, then allowances must be made in negotiating the road versus load, speed, traffic and rolling distances.

.

Just for giggles, I calculated the payback for the cam that was suggested earlier at $550. The writer said payback in two years or less, which, of course depends on the number of miles driven per year. I am paying 2.90/gal for #2 right now, and getting 21 mpg (according to my overhead). That makes $0.138 per mile. If I do the conversion and get 2 mpg, as suggested by the manufacturer, I get 23mpg, which translates to $0.126/mi. The difference is $0.012/mile (1.2 cents/mile). 550/.012 = 45,833 miles, so payback in two years is reasonable for many drivers for that mod. Now if the manufacturer is being overly optimistic, which they normally are, and let's say the actual mileage gain is 1mpg rather than 2. Now that payback stretches out to almost 92,000, or 4 years. Will you have the truck that long? Or are you outfitting the truck for the benefit of the next owner? Now lets add another $400 for the CAI, and $450 for the Smarty (keep in mind that adding accessories that say 2-4 mpg increase doesn't mean that if you keep adding them up you get 10 extra mpg), and you can see that your payback time is greatly compounded. So, if you spend $2000 on mods that get you 4 mpg extra (25mpg = ~2.2cents/mi difference), we are now looking at a payback period of about 91,000 miles.

For me, that equates to about 5 years or more. That means that in five years I will be back at "point 0", as if I hadn't spent the money at all and had lived with the original fuel mileage. From that point on, I start saving 2.2 cents per mile. In another 5 years I will have saved about $2000, if fuel prices stay about the same. I have to ask myself, "What else might I have done with that $2000 ten years ago?"

Now, if your actual fuel mileage is less, say 17 mpg before and 21 after, or if fuel prices increase, then your cost per mile increases and the payback period decreases accordingly. So, if you are intent on doing these mods, might as well do them now and get the payback period started!

My truck was outfitted with an AFE Brute Force CAI, BD Outlook monitor, and programmed with a BD Triple Dog programmer (which he kept), a straight pipe with a cat, probably around $2K worth, all of which benefits me. They guy was apparently a Hot-Shotter and ran up over 42K per year. The mods probably had just paid off by the time he lost the truck to the bank. I'm enjoying the benefits, because those things simply do not add any value on resale. Not only that, but the $2500 bumper he put on the truck probably sucked down all the mpgs the mods gave him. I'm enjoying the bumper, too.

Just food for thought while you are considering performance mods. Gaining MPGs is expensive. If you keep your vehicles until they wear out, like I do, they may be worth considering. If you like to trade vehicles every few years, then just consider it money spent on fun and "accessorizing" your toy. There can be satisfaction in both. Just depends on your personal desires and goals.