MPG fooler - Design phase

[ISX]

Went and weighed it with me in it and a full tank of fuel. Exactly 6600lbs. Guessing it would weigh ~6300 stock without me in it. As in, only 2 batteries, no tool box, no tools in my cab..

[Mopar1973Man]

Hmmm... Your 1,000# lighter than I am... Full tank of fuel, me in the saddle, mine weighs out at 7,300# = 4,400# Front axle + 2,860# But now with all the stuff in the bed of the truck and the topper I'm closer 7,900#... So I understand why you get better numbers...

[ISX]

Hmmm... Your 1,000# lighter than I am... Full tank of fuel, me in the saddle, mine weighs out at 7,300# = 4,400# Front axle + 2,860# But now with all the stuff in the bed of the truck and the topper I'm closer 7,900#... So I understand why you get better numbers...

[Rogan]

I agree with isx in the respect that the two trucks are far different, as well as the terrain and air density. However, thhe principles are the same in testing. Isx getting 27-28mpg boggles my mind, if he's getting consistently (empty) and mixed driving. Highway travel, I can believe it. My 96 got 26.9mpg at 65mph with 265-75/16, 5spd, 4x4, sclb, bhaf, #10 fuel plate full forward, arc full forward, Jacob exh brake, 4" dp, 7" stack, on a round trip from Virginia to new York. The 2nd trip, at 73 netted about 21.7mpg. Around my local area, which is a combination of hills, mountains, and flats, it averaged (with ~80% city driving,) it averaged about 19-21mpg. Pulling my 9000lb enclosed trailer, which is like pulling a shipping container around, the '96 got about 16-17mpg. Moving to the '01 24v, ( bhaf, no muffler, cropped exhaust at back of cab, 6 speed qcsb, 4x4, 265-70-16), a steady highway run to southern Virginia (240mi round trip) netted 17.6 @ 68mph. Same city travel as the old truck, this one only gets about 14mpg. Hook up to the trailer, and I'm lucky to see north of 10-11mpg. Additionally, there's a mountain that I pass with about a 1000' rise in elevation over the course of about 1.5mi, so it's quite steep for here. Pulling the trailer, the old truck would climb this in 5th, hitting the bottom at 70, and crossing the top at 65-68. The 24v (no real power adders) will take the same trailer, hit the bottom in 6th at 70mph, and I'll have to drop 2 gears and crest the mountain at around 40-45mph. Drastically different. Way less power, and way less economy. Diesel is now 3.19/gal here, so better economy is a high priority to me. I'll be glad to assist in anything i can to help with this quest "we're" on.

[ISX]

I agree with isx in the respect that the two trucks are far different, as well as the terrain and air density.

However, thhe principles are the same in testing. Isx getting 27-28mpg boggles my mind, if he's getting consistently (empty) and mixed driving. Highway travel, I can believe it.

My 96 got 26.9mpg at 65mph with 265-75/16, 5spd, 4x4, sclb, bhaf, #10 fuel plate full forward, arc full forward, Jacob exh brake, 4" dp, 7" stack, on a round trip from Virginia to new York. The 2nd trip, at 73 netted about 21.7mpg.

[JOHNFAK]

Yeah what Rogan says is what I see on the forums all the time. 12v getting 26-28 hwy and 18-20 city.24v getting 19-21 hwy and 14-16 city.Each case around 40% better than a 24v. Not 5%, not 10% -> 40% :stuned:Doesn't seem to matter too much where you live. Obviously peoples accuracy and true figures may vary though.So I was thinking it must be the 1000 lbs and smaller tires ....... but your saying you get the same mileage with the truck loaded isx ??? Then apart from the injection delivery/timing and compression the main differences would be the tires and lower to ground ?? I also notice Mikes MPG shoot up with the smaller tires. SO ...... has anyone on the vp44's switched out to smaller tires and noticed a large increase in MPG - and how would you calibrate to make sure its accurate ? As a smaller tire will do more revolutions per distance travelled and make your MPG shoot up correct ? I guess I was thinking - it "seems" possible to pick up 2+mpg with smaller tires. If I switched mine out - and got that I could possibly hit 22-23mpg. That in a 4x4 that still weighs 1000 lbs more than isx's seems a little closer to what he's seeing ......

[Mopar1973Man]

Yeah what Rogan says is what I see on the forums all the time. 12v getting 26-28 hwy and 18-20 city. 24v getting 19-21 hwy and 14-16 city. Each case around 40% better than a 24v. Not 5%, not 10% -> 40% Doesn't seem to matter too much where you live. Obviously peoples accuracy and true figures may vary though. So I was thinking it must be the 1000 lbs and smaller tires ....... but your saying you get the same mileage with the truck loaded isx ??? Then apart from the injection delivery/timing and compression the main differences would be the tires and lower to ground ?? I also notice Mikes MPG shoot up with the smaller tires. SO ...... has anyone on the vp44's switched out to smaller tires and noticed a large increase in MPG - and how would you calibrate to make sure its accurate ? As a smaller tire will do more revolutions per distance travelled and make your MPG shoot up correct ? I guess I was thinking - it "seems" possible to pick up 2+mpg with smaller tires. If I switched mine out - and got that I could possibly hit 22-23mpg. That in a 4x4 that still weighs 1000 lbs more than isx's seems a little closer to what he's seeing ......

[JOHNFAK]

Tires are not small diameter they are the same its just there narrower and less rolling resistance... As for Speedometer calibration I'm not worried... My Garmin GPS V is on the dash and I recalibrate the ScanGauge II to match the GPS so the Scangauge II mileage (distance) numbers are closer to correct than stock odometer on typically.

Yeah but what if you were running ISX's tires ........ 245/75/16 hmm - ran that through the calculator and only a 4% difference. But wonder on weight etc. ?? That could be another 10% overall compared to my 265/75/16's. How much do you pick up with the 235/85 R16 OAT's ?? mpg ? Thinking if I can hit 20mpg on the 265/75/16 -> then could I hit 22-23 on the BIG O AT's or ISX's tires. Then the numbers are closer again right ?

[ISX]

Yeah but what if you were running ISX's tires ........ 245/75/16

hmm - ran that through the calculator and only a 4% difference. But wonder on weight etc. ?? That could be another 10% overall compared to my 265/75/16's.

How much do you pick up with the 235/85 R16 OAT's ?? mpg ?

Thinking if I can hit 20mpg on the 265/75/16 -> then could I hit 22-23 on the BIG O AT's or ISX's tires.

Then the numbers are closer again right ?

Mine were also 60lbs.. I do run 80psi up front and 70 in back. Rogan surely had the same tires that Mike does on his 12V when he was getting 27. There is just something happening here about the 12 and 24 that I can't figure out. But there are several things that could be adding up. Like my valve springs are not 60lb springs, not sure what they are but they are less. 24V's have 60lb springs and 12 more of them.. Not sure that matters since the energy used to open the valve is sent right back when they close.

There is also the deal with compression but the problem is that the HO engines seem to get the same mileage as the SO ones. Supposedly lower compression is needed for higher loads (trailers) and you need more boost to be efficient, which means an SO engine with an HY (your truck John) would be the most efficient with a trailer. But obviously that isn't happening.

I am dumbfounded that THracing gets 22 with a 4wd dually 24V at 60-65 with 4.10s, and Rogan gets 27 with a 4wd at 60-65 as well. Yet when I go 60-65, I get 25-23mpg. Th runs smaller tires even (I think) and that would mean it would really be up there in the RPM's with those 4.10's. But if the engine had that much leverage, it would seemingly not have to work at all other than basically free reving to whatever that RPM. On the other hand we have Rogan with big tires doing 60-65 getting 27, that tells me low engine RPM and an advantage at miles per tire revolution can also gain you. What I mean by that is if I go 1500RPM, the engine isnt working but I'm not getting anywhere either, maybe 50mph. If Rogan went the same RPM, he might be at 60mph, so he racks up more miles which are part of the mpg equation.

So it seems you can beat the odds in a couple different ways. Giving the engine so much leverage that it doesn't even have to work, or allowing the engine to rack up miles at low RPM using slightly larger tires (I don't think Rogan was using overly aggressive tires or anything, just bigger diameter than me). That is why I want the 3.07, it would give me both advantages. 3.07 would rack up miles at low rpm, but the small tires would give me the leverage. I believe getting the miles up through the axle ratios is more efficient than trying to get them up through tire sizes, since bigger tires also come with added weight you have to push.

--- Update to the previous post...

Alright I was reading some conflicting info on the compression ratio crap. Finally found efficiency formulas that prove what a more efficient engine needs. It says you want the charge air to be as low of temp as possible and the temperature after combustion to be as high as possible. To accomplish this you need as high a compression ratio as you can run safely. So high EGT's are actually what you want..as long as they do not exceed the limits of the pistons. It seems you can run 1100F or so all day long on these engines so that would be optimal, but getting there with as cold of intake air as possible is a big challenge.

I will try and get a calculator going and see what I can figure out.

[white01]

i run 58 psi up front and 'bput 52 in the back the higher the tire psi the more than backend likes to bounce...as for weight..i ran up on the scales here at work last year where the trucks weight at..full of fuel and me..nothing in the bed7,040 lbs....after the big snow storm last year i shoveled the driveway and thru the snow in the bed....full of fuel and me and the snow..9,040 exactly!!that snow was piled high to!!

--- Update to the previous post...

ISX....if i was to put more air in the tires..lets leave the bounce out of it...how would it ride?steer?mpg?tires in sig and they are 10 ply/load range E..

--- Update to the previous post...

need to make myself more clear here..currently running 285/75/16's

[ISX]

i run 58 psi up front and 'bput 52 in the back the higher the tire psi the more than backend likes to bounce...as for weight..i ran up on the scales here at work last year where the trucks weight at..full of fuel and me..nothing in the bed7,040 lbs....after the big snow storm last year i shoveled the driveway and thru the snow in the bed....full of fuel and me and the snow..9,040 exactly!!that snow was piled high to!!

--- Update to the previous post...

ISX....if i was to put more air in the tires..lets leave the bounce out of it...how would it ride?steer?mpg?tires in sig and they are 10 ply/load range E..

--- Update to the previous post...

need to make myself more clear here..currently running 285/75/16's

I think the backend will hop regardless, though it does help having less air in them I would think. Up front the engine is so heavy I never run anything less than 80. If it ever hops up front it must be because I drove off a bridge More pressure should always help mpg. Try pushing a truck with flat tires.. The less air in them, the more surface area is touching the road, you want there to be less surface area. I fill my bed with snow (if we had any) too, otherwise I use engine blocks. I didn't know snow added THAT much weight! Though I don't doubt it, mine rode on the overloads last time filled it up, rode so smoooth.

[stodg73]

Am I an enigma because I get 22 mpg @ 75mph? I am running everything in my sig. I am turning about 2100-2200 rpm. When I am loaded with about 10k I get about 15.5+ mpg at 70mph.

[ISX]

Am I an enigma because I get 22 mpg @ 75mph? I am running everything in my sig. I am turning about 2100-2200 rpm. When I am loaded with about 10k I get about 15.5+ mpg at 70mph.

[stodg73]

P.S. don't let JOHNFAK know this!!!!!!

[ISX]

P.S. don't let JOHNFAK know this!!!!!!

[stodg73]

I know! More MPG & More Power!

[JOHNFAK]

P.S. don't let JOHNFAK know this!!!!!!

[SASQCH]

Alright I was reading some conflicting info on the compression ratio crap. Finally found efficiency formulas that prove what a more efficient engine needs. It says you want the charge air to be as low of temp as possible and the temperature after combustion to be as high as possible. To accomplish this you need as high a compression ratio as you can run safely. So high EGT's are actually what you want..as long as they do not exceed the limits of the pistons. It seems you can run 1100F or so all day long on these engines so that would be optimal, but getting there with as cold of intake air as possible is a big challenge.

I will try and get a calculator going and see what I can figure out.

[JOHNFAK]

As I'm following the posts here a thought occurred to me, the economy difference between the 12 valve and the 24 valve could be related to the difference between teh compression datios and/or the electronic injection pump verses the mechanical P-pump. It would be helpful if someone who has converted their 24 valve to a P-pump could contribute their experiences with economy before and after the conversion. It might point the way to whether or not the lower compression of the 24 valve engine is a real contributing factor to poor economy.

[ISX]

I think you are on the right track here. Performance engine builders have known for seventy years that the power output on an engine is related to the difference between the intake and exhaust temperatures. There are other factors that affect it but as a rule off thumb the temp difference in a key factor.

That's why so many engine builders and shops push cold air intakes as a means to get dense air in the engine for more power and economy. To me a CAI is a moot point with a turbocharger and inter cooler because it effectively does the same thing better. One of the differences on an electronic controled injection pump in the injection parameter from the IAT input and Mike is trying to ascertain what that effect is and how to control it.

This makes me wonder if I should put the 12cm2 housing back on my turbo before I go on another trip to Montana with another 8K load this spring and see what my mileage difference would be with the higher EGT it would give me. The problem I see isn't the 1100 degree EGT it's the 1350 degree EGT going over the passes. I guess I could just grab a lower gear and go slower. There are two long hard climbe one north of Ft Nelson and one south out of Ft StJohn that get the EGTs up a bit.

I think going from a 14 to the 12cm is going at it the wrong way. Your EGT goes up because it is more restricted so it's choking the engine (not very efficient). If your EGT went down then it had the flow you needed, rather than up because of it being too big of turbo (not spooling). I don't know how you did for boost differences but I am guessing the 12 built more, which means more heat on the intake side which in turn would mean higher EGTs which is not the way it is supposed to work. You need cold intake temps and hot EGT's. Though I guess it wouldn't make a difference since the compressor is the same, but choking the engine up wouldn't help matters I wouldn't think. Did your mileage go up or down when you changed them?

As I'm following the posts here a thought occurred to me, the economy difference between the 12 valve and the 24 valve could be related to the difference between teh compression datios and/or the electronic injection pump verses the mechanical P-pump. It would be helpful if someone who has converted their 24 valve to a P-pump could contribute their experiences with economy before and after the conversion. It might point the way to whether or not the lower compression of the 24 valve engine is a real contributing factor to poor economy.

I know CF has a whole section devoted to this so I will start scouring it and see what I come up with. I have been working on a calculator for several different aspects dealing with compression ratios and boost all morning. I have several factors now determined but I had to figure something harder out and am waiting on an answer.

The other economy factor I'm seeing is whether or not the truck is an auto trans or standard. One would think that while running in TC lockup there should NOT be a great difference in economy but in the real world there is, which begs the question why. If the planetary gears in the transmission were absorbing the energy from a 4 - 7 MPG difference the transmission would be a molten mass after a couple of hundred miles.

I think city driving with an auto kills MPG's. Someone just might be getting 27mpg all on the highway, then go through one little town and it all goes downhill. If you have a good tight trans like you and John seem to have (since they love to stall on you), then I would think the mileage would stay up. One thing I did notice is that the auto's tend to want to shift at 2000 or so, whereas I shift at 1800 or less.

Just my and food for thought.

Jim