van Aaken C3.2 and overhead mileage computer

[Blakers]

What kind of readings have you guys with the VA C3. 2 duration boxes been getting on your overhead mileage computers?



I know with the EZ the computers indicate higher mileage than actual. But, since the VA C3. 2 box hooks directly to the ECM, will it throw the overhead computer off like the EZ does?



Thanks.

 

[Blakers]

Just during my normal driving routine, my overhead computer is indicating about 1 mile per gallon less than before.



I admit, I have horsed it a little during this time, but not a lot. I've been trying to keep my same speeds and usual foot activity.



I have not checked the mileage the old fashioned way yet.



Has anyone else with a VA duration unit checked their mileage yet or observed the reaction of their overhead computer?



I had to bring this to the top as no one saw it. And I'm sure it will be discussed eventually.

 

[Sherman]

No mileage?

Originally posted by Blakers

Just during my normal driving routine, my overhead computer is indicating about 1 mile per gallon less than before.



I admit, I have horsed it a little during this time, but not a lot. I've been trying to keep my same speeds and usual foot activity.



I have not checked the mileage the old fashioned way yet.



Has anyone else with a VA duration unit checked their mileage yet or observed the reaction of their overhead computer?



I had to bring this to the top as no one saw it. And I'm sure it will be discussed eventually.

I have been waiting for real mileage comparisons for the VA duration box especially in the heavy tow world,I guess the price of fuel isn't high enough yet!!!!!!!If ther is no mileage gain towing at 1600-2100rpm range then why buy it .

 

[DLeno]

Personally I'm a skeptic when it comes to fuel economy improvements due to additional fuel. Unless that additional fuel is accompanied by timing of course, which is where the real economy gains are to be had in my opinion. In other words, certain driving conditions will benefit more than others -- highway cruising while empty is not one of them, as far as my experience tells me so far.



Its possible that small fuel economy gains could be had if you are able to stay in the lower rpms. But highway cruising is still going to be in the 1900 plus region. I personally have not found a mileage increase with the VA boxes, and believe that if such an improvement actually occurs, it will be less than 1 mpg.



I've had a similar experience with the overhead! I wonder if the fueling changes accomplished by the VA box are actually picked up by the overhead. normally I would not expect this, but the VA duration box is unique among all other boxes including the TST -- it lengthens pulse duration in the digital domain, not by analog fooling. So while I dont' have enough data to make this claim, I am suspicous that the extra fueling of the VA duration box may be detected by the overhead.



sorry, no towing data. I would expect a measureable improvement to the extent that the tow stays in the lower rpm range. again, no data to support that -- just an opinion.

 

[Sherman]

mpg

Originally posted by DLeno

Personally I'm a skeptic when it comes to fuel economy improvements due to additional fuel. Unless that additional fuel is accompanied by timing of course, which is where the real economy gains are to be had in my opinion. In other words, certain driving conditions will benefit more than others -- highway cruising while empty is not one of them, as far as my experience tells me so far.



Its possible that small fuel economy gains could be had if you are able to stay in the lower rpms. But highway cruising is still going to be in the 1900 plus region. I personally have not found a mileage increase with the VA boxes, and believe that if such an improvement actually occurs, it will be less than 1 mpg.



I've had a similar experience with the overhead! I wonder if the fueling changes accomplished by the VA box are actually picked up by the overhead. normally I would not expect this, but the VA duration box is unique among all other boxes including the TST -- it lengthens pulse duration in the digital domain, not by analog fooling. So while I dont' have enough data to make this claim, I am suspicous that the extra fueling of the VA duration box may be detected by the overhead.



sorry, no towing data. I would expect a measureable improvement to the extent that the tow stays in the lower rpm range. again, no data to support that -- just an opinion.

In your opinion what would be the towing range?According to Cummins this ho engine can run all day at 1600 and above,I have found that when pulling a 14500# trailer and above 1700rpm the mileage will vary by about 1mpg /100rpm on generally flat ground at sea level. My guestion would be :is there a mpg gain at that 1600-2100 tow range at 14500# with a 6sd transmission?

 

[DLeno]

Well, given people tow differently I'm not out to state what the towing range actually is -- just to suggest that 1700-2500 covers it for the vast majority of cases.



In my opinion, the box itself doesn't make the engine consume fuel any more efficiently. In actual driving situations, mpg gains at lower rpms are dominated by friction and wind drag, which cause the required horspower to change as the cube of vehicle speed. That means if you cut the engine rpms from 2000 to 1900, a 14 percent decrease in required engine power results. So 1 mpg per 100 rpm is not unreasonable. but the point is, how much of that fuel economy improvement is actually due to the engine's better use of fuel, or the fact that it doesn't have to work as hard to begin with to overcome friction and wind drag. Only a dyno will tell us that because its the only way you can change vehicle speed without changing the load demands on the engine at the same time.



That said, the engine itself has to oversome inirtial and friction losses at higher rpms, and so there is a sound argument for a small fuel economy improvment when engine rpms stay low. I'm only saying that this factor is swamped in real driving conditions by the engine load factor -- you simply cannot reduce engine rpms without reducing engine load at the same time.



The older mechanical 5. 9's had a real preference for the lower rpms, and the fuel economy issue was pronouced within an rpm sweet spot. While the lower rpms do without a doubt contribute to fuel economy, it is difficult to say (on the HPCR engine) that the engine has the same preference for lower rpms (or to the same extent) as its mechanical predisessor did.



Without driving this into the old "sweet spot" discussions (which are fun) suffice to say I believe we can all accept that some fuel economy improvement can be acheived simply by running at lower rpms. Cummins has told me that themselves (that fewer, large fuel charges is better). So to the extent that a fueling box lets you avoid a downshift by delivering enough power at a lower rpm, I would predict a measureable fuel economy improvement. As for cruising at 65 mph with and without a box? I havent seen any compelling data showing that only extra fueling (not timing) in a performance box will yield a realizable, measureable, and substantially benefitting improvement at the same rpm. .



In my current understanding (and experience running empty) and without data to the contrary, I would not purchase a pressure or duration box expecting to see a fuel economy improvement. I would buy one for the drivability improvement. However I can suggest that if the extra power allows lower engine rpms than otherwise, then yes you will see an improvment. That depends a great deal on driving conditions though. for example, if you do a lot of pulling now and find that shifting into 5th is required to maintain speed, a fueling box might let you avoid that and stay in 6th gear, avoiding the higher rpms to maintain the same vehicle speed. On the other hand, the effect of the stock truck might be to cause you to both shift down to 5th AND slow down to 1900 rpm, in which case the stock engine might give you better fuel economy.



So this is a long answer to your question, simply because I am speaking from a theoretical standpoint. Maybe some of the guys who keep extensive fuel logs and make regular towing runs could chime in with more practical data.

 

[Sherman]

NOW you are getting close,this time I will be more specific,Let's say for discussion: we are at sea level on a standard day no wind, on a flat paved road,you have a 10000# trailer hitched to your gooseneck ball that is the bed of your truck,by the way your truck is a box stock ho 6sd 4. 10 gears,you pull the trailer at a fixed speed 1900rpm in 6th gear and get 11. 0mpg then while continuing todrive at 1900rpm you turn on your VA duration box ,now the question:is there any improvement in mpg and if so what would be your educated guess as to the amount of improvement?

 

[EEngel]

MPG gain & Overhead

I have seen a little over 1mpg gain since I put the VA box on. I have been running in the 50% mode.



My overhead was always ~0. 7mpg low, now it's about 1. 1mpg low.

 

[Blakers]

Originally posted by EEngel

I have seen a little over 1mpg gain since I put the VA box on. I have been running in the 50% mode.



My overhead was always ~0. 7mpg low, now it's about 1. 1mpg low.

My overhead is the same way. It was low before and now seems a little lower. I mathmatically checked my mileage today and it was about 17. 5. I usually get just over 19, but I have been playing around with the box here and there, so it will probably be lower than normal.



I got behind a slow poke on my way to work last night and when he turned off the road I nailed it with the box on 100% and going just over idle in 4th. She broke loose and left a black cloud.



I've been running at 50% for the most part. That's what Danny recommended for mileage.

 

[EEngel]

50%

Blakers,



I have been running at the 50% setting 99% of the time. Just every once in a while you feel that "need".

 

[JFulford]

VA C2 mileage

I put my VA C2 in about a week ago. Filled up at QT and reset the overhead computer. Currently reading 1. 5-2mpg Better than before, on the middle setting. Haven't tried the upper setting.

BTW, weighed the truck with an almost empty tank and 200 lbs of tools in it: 7560! Longbed/quad cab/ automatic/4wd

jeff

 

[EEngel]

Mileage gain

JFulford,



Let us know what your results are when you fill up again.

 

[JFulford]

EEngel

No problem, but it could be a while. No major trips planned for the month.

jeff

 

[DLeno]

Originally posted by Sherman

NOW you are getting close,this time I will be more specific,Let's say for discussion: we are at sea level on a standard day no wind, on a flat paved road,you have a 10000# trailer hitched to your gooseneck ball that is the bed of your truck,by the way your truck is a box stock ho 6sd 4. 10 gears,you pull the trailer at a fixed speed 1900rpm in 6th gear and get 11. 0mpg then while continuing todrive at 1900rpm you turn on your VA duration box ,now the question:is there any improvement in mpg and if so what would be your educated guess as to the amount of improvement?

ahh, thats the $64 question. Personally I approach the possibility of some mpg improvement in this situation with some skepticism. But Here's what I think could happen: The VA will lengthen pulse width and the ECM will lower fuel pressure -- to get the same net fuel charge in there to deliver the same amount of torque to pull the same load . The result is a longer, smaller fuel charge.



Any argument for a fuel economy increase in this situation would have to be based on establishing a more complete burn via the longer duration. I have speculated in the past that this might be the case, but it has not been established with any certainty.



We do have evidence that going too far with fuel duration acutally may reduce fuel economy by producing more unburned fuel very late resulting in higher EGTs. At the risk of reading more into that evidence than is appropriate, I'd suggest that if there is a mpg opportunity via duration, that opportunity would be limited to moderate duration (VA style or TST on lower settings).



What would be cool here is to do an EGT study of the TST/EZ combination to discover where the EGT sweet spot is, in terms of a combination of pressure and duration. that would probably correspond also to the fuel economy sweet spot.



collecting statistically valid data showing that duration increases fuel economy would be time consuming, but it could be done. One would have to run interleved fuel tanks with the box on and then off respectively, and calculate mileage manually. The question would basically involve the ability to detect (with statistical significance) a difference in the mean fuel economy of the box-on data versus the box-off data. Some time I'll dig out the stats book and find out what kind of sample size would be requried



But the answer to your question is that my un-validated opinion tells me there will be less than 1 mpg advantage, if any. I think more substantial improvements would come from the newly aquired ability to stay in higher gears because of increased available torque.

 

[EEngel]

Testing

DLeno,



Better get started with all the tests you have planned. You only have 6 weeks recovery time off...

 

[DLeno]

yes well, the frustrating thing is that during recovery I can plan but I can't do!

 

[JonCoffey]

MY WORD, i just had a really simple ?

 

[DLeno]

in what thread? I don't see a question from you in this one . BTW welcome to the forum -- I saw that this was your first post, at least as JonCoffey



guess you figured out by now that the answer to the fuel economy question with duration is not simple b

 

[EEngel]

?'s

Doug,



There seems to be plenty of simple questions, just no simple answers.



Getting better daily or what?

 

[DLeno]

yup. Boy did we drift this thread or what .



Anyway, doc says I still can't lift anything heavier than a beer can, but I can use a laptop as long as it is not in a case (weight), and then only carefully. start working from home 2 hrs per day next week. Today I felt good enough to start wiring gauges. I figured wires, panels, and gauges and screws were no heavier than a beer cans , so now I have dimmed 12V and switched 12V wires waiting to be used. I have yet to go through the firewall...