12V fuel economy, or lack thereof...

[Rogan]

So I've been driving my 'new'sed 97 DRW for a few months now..12V, 135k, auto, 4.10, 235/85-16s, BHAF, #0 plate, 4" exhaust...Best tank MPG: 13.1Avg tank MPG: 12.3-12.7Talked to a buddy of mine that has near exact truck and mods. He has a #10 plate though.. he averages about 17-18mpg and has very similar driving habits and city/highway mix as I do..Thinking maybe I need to get a few things checked out:timingfuel plate positioningvalve lashThoughts? (ISX)

[ISX]

I thought you said it was the auto that was causing all of this..?

[Rogan]

I didn't say it "was the reason", but more of a strong possibility?

[ISX]

List all of the things you have noticed about it in comparison to your other 12V. I mean ANYTHING. Does it take 1ms longer to start, does it smoke, does it..... 12mpg unloaded is absolutely horrible so if the problem exists within the engine then it would be pretty obvious. Timing would be wayyyyy off. My timing has been from +2* to -20* and I didn't notice but a few mpg difference. Symptoms would get us started though.

[Rogan]

Previous 12V:

Timing @ 16*

4" DP w/7" stack, no muffler

265-75-16

#10 fuel plate full forward

star wheel full forward

3K GSK

BHAF

Boost elbow

haze on cold startup/warmup, clean after that, except for obvious acceleration

As an auto: 15-17 city, 22-23 hwy empty 13-15 towing

- shifted normally, didn't seem to slip at all when accelerating as going through the gears

- 2nd gear shift @ 15, 3rd shift at ~30, OD ~40, Lockup ~50mph (all subsequent gear changes after 1st seems positive and firm, no noticeable slippage

As a 5 speed: 17-18 city, 25-27 hwy empty, 21-22 towing

Current 12V:

Timing ??

4" TBE with muffler

235-85-16

#0 fuel plate, position unknown yet

star wheel unknown

stock GSK

BHAF

no boost elbow

haze on startup/warmup, clean after that, except for obvious acceleration

As an auto: 12-13 city/hwy, emtpy/towing

- shifts abnormally, seems to slip in 3rd when accelerating as going through the gears

- 2nd gear shift @ 10, 3rd shift at ~20, OD shortly/immediately after, Lockup ~50mph

3rd gear seems slippy, as does OD at lower speeds. Lockup feels like direct drive (as it should)

- Manually shifting is what I almost have to do in order to reduce/minimize the slipping and/or early gear changes

[rancherman]

sometimes I'll post 'devils advocate'. maybe for my own info, maybe to spark a conversation.I see a lot of talk about timing. and justifiably so! I was curious... are all our cummins pumps 'zeroed' perfectly? can there be differences? (either from factory, a recent rebuild shop...)My Perkins 540's are 'tuned' using the spill method of setting the timing. It's a simple 'dumb as a rock' process that eliminates timing problems due to wear and tear, or manufacturing/assembly goofs. This includes everything from driver cam in IP all the way back to the engine crankshaft. Those 540's have a nightmare of gears in the timing case!!! Spill timing is the point in the cycle where IP sends all fuel to injector. No bypass in the ip's head. When #1 piston is 5/8ths inch btdc, IP's #1 fuel return/bypass should be ' just closed'. All fuel from that point foward is then 'injected'. measuring pistion distance btdc even eliminates 'bad' or slipped marks on a crank balancer.Effectively, the ' start" of the injection event is 18* using this method. I'm sure a few more degrees are needed to actually 'pop' the injector! So, I was just curious if we need to put ALL faith on a little 'mark'... to definitely set our injection? I agree on ISX's post; The symtoms of a poorly tuned are pretty easy to analyze.... and from that an adjustment one way or the other.In other words, if its 'set' at cummins recommeded, but its hard starting, smoking, heating, etc... MUST we assume automatically that it's something else??

[Rogan]

something else to add for ISX's request is EGT..My old 12V would run at, say, 55mph, no load, about 500-600*F (probe in the exhaust manifold.) Boost no load 2-4psi. loaded/towing, flat, 5-10psi.My 24V was just about the same.This one runs closer to the 600+ mark, and the probe is in the DP, just after the turbo.. It should run cooler there, but that is not the case. Possibly a bad/weak probe, but not sure..55mph no load, ~4-5psiloaded can be anywhere from 5-12psi on fairly flat ground.

[ISX]

sometimes I'll post 'devils advocate'. maybe for my own info, maybe to spark a conversation. I see a lot of talk about timing. and justifiably so! I was curious... are all our cummins pumps 'zeroed' perfectly? can there be differences? (either from factory, a recent rebuild shop...) My Perkins 540's are 'tuned' using the spill method of setting the timing. It's a simple 'dumb as a rock' process that eliminates timing problems due to wear and tear, or manufacturing/assembly goofs. This includes everything from driver cam in IP all the way back to the engine crankshaft. Those 540's have a nightmare of gears in the timing case!!! Spill timing is the point in the cycle where IP sends all fuel to injector. No bypass in the ip's head. When #1 piston is 5/8ths inch btdc, IP's #1 fuel return/bypass should be ' just closed'. All fuel from that point foward is then 'injected'. measuring pistion distance btdc even eliminates 'bad' or slipped marks on a crank balancer. Effectively, the ' start" of the injection event is 18* using this method. I'm sure a few more degrees are needed to actually 'pop' the injector! So, I was just curious if we need to put ALL faith on a little 'mark'... to definitely set our injection? I agree on ISX's post; The symtoms of a poorly tuned are pretty easy to analyze.... and from that an adjustment one way or the other. In other words, if its 'set' at cummins recommeded, but its hard starting, smoking, heating, etc... MUST we assume automatically that it's something else??

Well for starters Rogan, the fuel plate, starwheel, etc. have nothing to do with efficiency. They don't even do anything unless you are stepping on it. If it starts fine then timing isn't an issue. If it doesn't completely fall on it's face up high then it isn't an issue as well. Overly retarded makes it start in an instant, overly advanced makes it start like crap. You can set your valves and clean the injectors but unless it's chugging out of the valves or missing from a crappy injector, I'm really not seeing THAT big of a MPG drop. Do you have an EGT and boost gauge and some numbers you can share? As for rancherman, from everything I have read, the tolerance of error is about 1-2*. However, I think I've read about the tab in the pump sliding around, rarely though. I use the valve drop method to find tdc and spill timing to set mine as well. It's easy and dead nuts. But, I believe for the most part the pin inside the pump is plenty accurate. You're not gonna notice a degree here or there.

[Rogan]

added boost numbers to previous post..also, this truck doesn't pull like the old ones did. By 'pull', I mean accelerate as quickly. This one also seems like, say, from a stop, to flat-out mash to the mat, it doesn't pull real strongly, as I manually go through the gears. And the pedal doesn't really feel like it travels very far..(that part might just be in my mind.)But it doesn't really have the uhmph that either of the other trucks had..

[AH64ID]

Higher EGT's is likely from retarded timing (a few deg makes a big difference), a boost or exhaust leak. All of which would decrease economy.

[ISX]

Alright I'm gonna dispell all these theories (since nobody has any proof) on what exactly timing does. I will set my truck at 0-10-20* and record EGT's, boost, everything at a set speed at operating temp on the same road same everything. I will get recordings of what each sounds like since they do each sound different. I don't remember there being that big of a difference between them but I cannot exactly prove all this since I have no movie of each one. I do know that pulling a trailer at 2000RPM raised EGT's 100-200F but this was at 2* ATDC if I did everything right. The doing everything right thing is what I question (before I knew about spill timing). I know it was way retarded but I am not sure on the exact degree, so this time now that I know how to do it all I will get info.

[AH64ID]

Timing alone on my truck netted about 55rwhp in the mid range, and 200° cooler EGT's.

Timing is huge, is plays a major role in economy, spool, power, torque curve, EGT's, and boost.

I have probably 40+ hours in writing a tune for my truck, I would say that all but 2 of those are on timing, and timing alone. Trying to find that ideal timing. 12V's aren't nearly as complicated, but it's still a diesel engine and timing is very important.

This is a general chart, the is geared mostly towards P-pumps. (This is all within reason, like the change from 13.5° to 16.5° or 10.5° , not 13.5° to 30° or 0°).

[TABLE=align: center]

[TR]

[TD=bgcolor: #FFFFFF]Engine parameter:[/TD]

[TD=bgcolor: #FFFFFF, colspan: 2]

TIMING is:

[/TD]

[/TR]

[TR]

[TD=bgcolor: #FFFFFF]RETARDED ( - )[/TD]

[TD=bgcolor: #FFFFFF]ADVANCED ( + )[/TD]

[/TR]

[TR]

[TD]EXHAUST TEMP[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[TR]

[TD]CYLINDER PRESSURE[/TD]

[TD]decreases[/TD]

[TD]increases[/TD]

[/TR]

[TR]

[TD]INTAKE MANIFOLD PRESSURE

(BELOW P-TORQUE) WASTEGATED[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[TR]

[TD]BSFC (brake specific fuel consumption)[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[TR]

[TD]NOX (oxides of nitrogen)[/TD]

[TD]decreases[/TD]

[TD]increases[/TD]

[/TR]

[TR]

[TD]HEAT REJECTION[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[TR]

[TD]HYDROCARBONS (HC)[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[TR]

[TD]BLACK SMOKE: 1000RPM[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[TR]

[TD]BLACK SMOKE: PEAK TORQUE[/TD]

[TD]decreases[/TD]

[TD]increases[/TD]

[/TR]

[TR]

[TD]BLACK SMOKE: RATED[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[TR]

[TD]WHITE SMOKE: < 1000RPM[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[TR]

[TD]WHITE SMOKE: > 1000RPM[/TD]

[TD]increases[/TD]

[TD]decreases[/TD]

[/TR]

[/TABLE]

Timing needs to be set where you spend most of your time, or want your motor to run best. A guy that lives empty at 80 mph will require a less advanced timing than a guy that tows 20K lbs at 2300 rpms all the time. They both need different timing than a guy that is sled pulling, or drag racing. So take that chart for what it's worth, as decreasing timing may actually improve economy.. if that's fits your motor better.

[Mopar1973Man]

I know I don't exactly apply either but I've been hunting for a smokeless tune that keeps the MPG's as well. Come to find out even in my tuning that reducing the sublevel from 5 to 3 well come to find out the timing curve fell out sharply and so did the MPG's even my ScanGauge II is showing only 16-17 MPG at best. So I bounced up to Sublevel 4 trying to gain back but here comes the darn smoke again. I'll most likely return back to 5.

[AH64ID]

I am finding the same thing with my UDC tuning, a slight haze under 30-50% load acceleration (I do mean SLIGHT), and clean under constant rpm's. Take a look at all older diesels that were tuned for economy/performance and they all haze a little under acceleration and they all use less fuel than their current counterparts..

[rancherman]

..........then there is the unlikely possibility of the cam being off a tooth........which would put everything 'off the reservation'.... Or an improperly indexed cam... I suppose a cam 'off' one tooth in a turbo'd engine would barely run. never mind.