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Engine Specific Info and Questions => IDI Engine => Topic started by: Mark(The Miser)UK on November 26, 2013, 03:35:17 pm
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Some may remember my proclamation a month back or so when I said that my engine was happy running @0.5 to 0.6mm, and got good turbo response, and fuel economy.
Then, yesterday I said reducing the timing from 0.95 to 0.8 should reduce engine temperature. In an act of good will, to prevent those who despise me making foolish comments, here is an extract from a write up that I haven't seen for 10 years from the Dodge-Ram-diesel-Cummings site....
Well, well it still exists!
> "What changes in measurable parameters such as EGT, power, noise, smoke, fuel
> consumption, etc. will I find as timing is varied? I'm not looking for
> numbers, just relative changes?"
" Here is a general overview of what happens when you change timing on Cummins' B- and C-series engines. I would imagine that this holds true for any engine that uses a pump-line-nozzle type fuel system; results may be different for larger engines that use unit injectors (on-highway truck engines, for example):
Engine parameter:
TIMING is:
RETARDED ( - ) ADVANCED ( + )
EXHAUST TEMP increases decreases
CYLINDER PRESSURE decreases increases
INTAKE MANIFOLD PRESSURE
(BELOW P-TORQUE) WASTEGATED increases decreases
BSFC (brake specific fuel consumption) increases decreases
NOX (oxides of nitrogen) decreases increases
HEAT REJECTION increases decreases
HYDROCARBONS (HC) increases decreases
BLACK SMOKE: 1000RPM increases decreases
BLACK SMOKE: PEAK TORQUE decreases increases
BLACK SMOKE: RATED increases decreases
WHITE SMOKE: < 1000RPM increases decreases
WHITE SMOKE: > 1000RPM increases decreases
For Cummins' B & C-Series engines, the timing is part of the CPL (Control Parts List), which is basically the emissions "recipe" that we use when certify the engine with the EPA. There is a tolerance band around that timing, and setting the timing out of the tolerance band around the specified timing is technically illegal."
" The VE pump used on Cummins engines in '89-'93 Dodges is a rotary style pump with an engine-speed dependent timing advance mechanism: as engine speed increases, the timing advances. The P7100 pump used on Cummins engines in '94-'98 Dodges is an inline style pump with no dynamic timing adjustment capability (technically, you can get dynamic advance by using a really complicated fuel pump gear, but we chose not to do that). The VP44 pump used on Cummins engines in '98.5-later Dodges is an electronically controlled rotary pump. It uses a timing advance mechanism that is similar to that of the VE pump, but it's controlled by a solenoid. This gives us the capability of varying timing throughout the engine operating speed range (roughly 700-3600 RPM in a Dodge)."
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Extracting less heat from your exhaust just means you are blowing it out the tailpipe. I have never heard anyone advocate retarding the timing on a Cummins On mine the coolant temps get more rise from thermostat cycling than running wide open uphill (something to be said for a 7 gallon cooling system). BSFC and EGT both go up with retard. boost goes up because you are burning fuel in the turbo instead of the engine.
Mine being a 94 motor is timed to the most retarded spec, and what to you know, power isn't that good, and it gets under 20 MPG
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LOL I wouldn't know a Cummins from a Caterpillar.
I'm not advocating everyone retards their engine by vast amounts, if at all, despite my weird engine, but my point was that Rising EGT due to changes in timing like from a perfectly feasible 0.95 to 0.8, are not linked to rises in cylinder temperature, unlike rises in EGT due to putting one's foot down.Thus a slight improvement may be welcome when running near the engines limits.
EGT is a crude, but convenient measure. Advantage of a timing based rise in EGT will give you a quicker rise in boost pressure.Coupled with the lower peak pressure in the cylinder, which presumably allows those who wish to add more fuel, with a goal of speed increase, rather than economy... After all this is the GTD site, ;D despite my owning a GTD; I'm in search of Spock, oops, reasonable fuel economy, with or without a power increase.
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I don't have my pyrometer installed yet, but can attest to a bit more power in the lower rpms after retarding my timing a bit.
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Well shyoot TD, I never thought of it that way.. I must just need to retard a little bit.. The 1.6TD is so sluggish off the line.
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I have a pyro and boost gauge waiting for install, so I'm flying blind... and not advocating much adjustment without gauges.
YMMV
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What would I know, I don't drive my IDI at low RPMs, it's happiest at 2700 RPM Torque peak.
The Cummins formula is advance timing 3-5 degrees for a few HP and +3 to 5 MPG, or 6+ degree if you are ready to break off some driveline parts.
While the more boost might sound appealing, 90% of the time unless you have a Banks 6.2 or first gen Dodge, the wastegate will be the limiting factor anyway.
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I have a pyro and boost gauge waiting for install, so I'm flying blind... and not advocating much adjustment without gauges.
YMMV
Very true, I understand. I am not by any means "new" to this ;).
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Interesting topic for sure. I don't know enough to jump in, but it's good reading.
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It was/is understood that retarded timing increases EGTs but does not increase cylinder temps. It will decrease cylinder temps by sending the still burning fuel out the exhaust pipe instead of turning it into useful work. I don't see why anyone would want any of the effects of retarded timing listed above except the reduction of NOx and the increase in manifold pressure. Both of those 'benefits' come at the cost of reduced engine efficiency, reduced power and increases of all the other emissions.
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Retarding timing reduces cylinder pressures, because the chamber at peak burn is larger. It is larger because the piston has moved further down the chamber.
Further down the chamber naturally means the peak is peaking on say 15 degrees ATDC, which means more energy goes into the torque, contrast with the extreme of peaking @ TDC for instance, with higher pressure less extractable torque, greater heatloss to the engine.
What I strove for years ago, was to try and flatten out the combustion pressure, my main method being to extend injection period by lowering break pressures. Down to 125bar for instance.
Was I successful? Well I don't know, but my car beats official handbook economies. This was at 0.57, 46mpg [imp] round town and 62+mpg on a flat run. So despite low value timing it clearly doesn't all go out of the exhaust.
I would like to spend more time researching. Obviously too retarded and the potential gain in torque is exceeded by excess energy out of the exhaust.
If I had a machine to measure area and angle under the pressure curve, it would help...
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What I strove for years ago, was to try and flatten out the combustion pressure, my main method being to extend injection period by lowering break pressures. Down to 125bar for instance.
Was I successful? Well I don't know, but my car beats official handbook economies. This was at 0.57, 46mpg [imp] round town and 62+mpg on a flat run. So despite low value timing it clearly doesn't all go out of the exhaust.
Huh, that is quite interesting. 0.57mm... How did it start when cold out? I have never even dabbled with the lower end of injection timing because I have always been told that the "advanced" side of the Bentley specs was where you wanted to be regardless..
This is very intriguing. 38mpg -city and 52mpg -hwy US MPG? That's surely not wasting fuel.
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Take it with a grain of salt. Giving a 'timing setting' in mm of plunger lift with non-stock injectors or non-spec pop pressures is very misleading. I believe that Mark has significantly lowered injector breaking pressure and so the actual timing of the start of injection or more importantly start of combustion is very likely similar to spec or more importantly completely unknown.
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Take it with a grain of salt. Giving a 'timing setting' in mm of plunger lift with non-stock injectors or non-spec pop pressures is very misleading. I believe that Mark has significantly lowered injector breaking pressure and so the actual timing of the start of injection or more importantly start of combustion is very likely similar to spec or more importantly completely unknown.
I would guess this is accurate. I would think any gains in mpg would be because of the pump not having to work as hard to open the 155 turbo spec or whatever n/a spec is.
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Take it with a grain of salt. Giving a 'timing setting' in mm of plunger lift with non-stock injectors or non-spec pop pressures is very misleading. I believe that Mark has significantly lowered injector breaking pressure and so the actual timing of the start of injection or more importantly start of combustion is very likely similar to spec or more importantly completely unknown.
I would guess this is accurate. I would think any gains in mpg would be because of the pump not having to work as hard to open the 155 turbo spec or whatever n/a spec is.
Makes sense to me as well, and an interesting perspective. The piston in the pump, moving non-compressible fluid into a high pressure chamber. The only variable in that equation is the spring in the injector.
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Hrrmmm...
125:155 (bar) is only ~20% difference. If memory serves, it takes about 5hp to drive the IP, so a difference of 1hp or ~750W. I don't see that making much impact on fuel economy.
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I believe I've seen Mark post of pressures lower than that. 105 bar? How much HP is required to make a Quantum cruise at 35MPH? Approx. 5 or 6... Regardless, the point of my post was to say that 0.6mm lift w/ 105 bar(?) injectors may well equate to the same start of combustion as 1.05mm lift with 155 bar injectors...
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I believe I've seen Mark post of pressures lower than that. 105 bar? How much HP is required to make a Quantum cruise at 35MPH? The point of my post was to say that 0.6mm lift w/ 105 bar(?) injectors may well equate to the same start of combustion as 1.05mm lift with 155 bar injectors...
No argument with that... Mark may have actual gauge vs. piezo data.
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How much HP is required to make a Quantum cruise at 35MPH? Approx. 5 or 6...
Takes about 2 hp to make a bicycle go 35mph, so I rekon it might take a little more than 5 or 6 for a 3000lb wagon.
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2,800 lbs, 25 sq. ft. frontal area and 0.35 cod @ 35MPH = 5.86 hp.
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2,800 lbs, 25 sq. ft. frontal area and 0.35 cod @ 35MPH = 5.86 hp.
That's some good info - can you break down your equation a bit?
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Neglecting rolling resistance, driveline, etc...
"During stop-and-go city driving, it's estimated that overcoming inertia is responsible for about 35% of the vehicle's resistance. Driveline friction is about 45%; air drag is about 5% and tire rolling resistance is about 15%."
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=29
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2,800 lbs, 25 sq. ft. frontal area and 0.35 cod @ 35MPH = 5.86 hp.
That's some good info - can you break down your equation a bit?
Sure. Punch them into a HP for speed calculator... E.G. (http://www.wallaceracing.com/Calculate%20HP%20For%20Speed.php) I was making educated guesses on the frontal area, cod and unladen weight.
Neglecting rolling resistance, driveline, etc...
"During stop-and-go city driving, it's estimated that overcoming inertia is responsible for about 35% of the vehicle's resistance. Driveline friction is about 45%; air drag is about 5% and tire rolling resistance is about 15%."
http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=29
Yup. I'm aware of those factors. I was only attempting to show that a saving of 1 or 2 HP may be a little more than insignificant as you initially proposed. I think I succeeded.
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Yup. I'm aware of those factors. I was only attempting to show that a saving of 1 or 2 HP may be a little more than insignificant as you initially proposed. I think I succeeded.
If 5hp (guessing) is 5%:
5 + 45 + 15 = 65hp total cruising P-in (ignoring inertial losses) for 35mph... less 1hp (a reduction of ~1.5% ).
A 1.5% increase in efficiency if not factoring inertial losses. 1% or less in the real world.
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Are you trying to say it takes 65 engine horsepower to go 35MPH? I wonder how I've managed to go 90 on flat ground with an engine that puts out a peak of 52hp... I do not think it is reasonable to use Tire Rack's estimates of the average driver's energy use to calculate the potential fuel savings of a hypermiler with injection mods, if that's what you're doing.
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2,800 lbs, 25 sq. ft. frontal area and 0.35 cod @ 35MPH = 5.86 hp.
That's some good info - can you break down your equation a bit?
[/quote]
Sure. Punch them into a HP for speed calculator... E.G. (http://www.wallaceracing.com/Calculate%20HP%20For%20Speed.php) I was making educated guesses on the frontal area, cod and unladen weight.
Neglecting rolling resistance, driveline, etc...
Cool - thanks for the link libby.
I usd .44 CD (from the Samba), a frontal area of 30.25 (5.5' x 5.5'), and 4000 lbs for the van. Here are the results.
Using your vehicle Speed of 65 MPH takes 24.95 HP to overcome air drag.
Rolling resistance is 9.01
For a total of 33.97 HP to run 65 MPH
There may be a bit of data missing from the calculator ;D
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It does not include drivetrain losses which are typically calculated at 15%. The CoD for a Westy is 0.51 (largely due to the luggage rack). Frontal area is also larger. Spec is 3.17m^2 = 34.1 sq. ft. Floored, a well-tuned 48hp 1.6 non-turbo westy will make it above 65 on flat ground with no wind. With drivetrain losses, that engine is peaking at 42HP to the wheels. Try those numbers again...
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I'm back...
OK here's some limited data. Alas I don't have current pietzo info as I dropped the SUN strobe, and it doesn't light up. Probably repairable. My other strobe is a Dieseltune one that clamps inline on the output of the pump and measures pump timing.
I am currently running old 293 nozzles @ 130bar. That has been giving me a static timing of 26 thou.
The lowest I actually went down to was 120bar, that liked a timing of 22thou.Winter starts have been fine down to -10C.
I did intend to go loweras I haveseen nozzles of this type run at 110bar factory on some engines, but my old nozzles weren't good enough.
The only set of 4 new old stock French ones I had, to do the job, had one faulty one and one pin I managed to break on another. Economy was good, so I left it at that meaning to return in the future.
Physical engine knocking became my obsession.
The big question no-one has asked, is how did I get to these timing figures, that were seemingly so far off the beaten track? I certainly didn't walk into the desert and have a vision, or did I? ;D
Well, I did have a bit of an inspiration, as I was looking for a way of determining 'best timing' I thought perhaps I could look for smoothness of running; so I first listened to engine, and adjusted at idle. Not easy to decide, I then moved on to listening to smoothness of acceleration.
I then combined with finger tips on the shifter, whilst on the road, to feel for smoothness. This was quite good and started giving me lower timing figures. Still this is quite hard in the absence of silky smooth roads. In retrospect, lowering tyre pressures may have helped...
The trouble with these methods is that they required some skill, and time. I wanted something I could do whilst stationary, and with repeatability.
OK another inspiration...
I was looking for maximum economy, so, presumably, by definition that must mean more miles per gallon; so back at the engine surely more revs per gallon.
Thus the jump to the most energy out per injection. This I thought would be reflected in the desire of the engine to want to increase revs.
I just happen to have an analogue rev counter from a truck that by luck works by the W connector, and is both accurate, and has an expanded FSD of only 3500 revs.
To operate, I have it connected in the engine compartment. I raise the revs to about 1000 to 1100, [from around 750] by altering the clip on the accn. cable.
I swing pump until I find a jump in the revs. I then tighten the pump, and hope it stays in the sweet spot.
Strangely, often the revs drop by about 30 when the bottom nut is tightened.
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I'm back...
OK here's some limited data. Alas I don't have current pietzo info as I dropped the SUN strobe, and it doesn't light up. Probably repairable. My other strobe is a Dieseltune one that clamps inline on the output of the pump and measures pump timing.
I am currently running old 293 nozzles @ 130bar. That has been giving me a static timing of 26 thou.
The lowest I actually went down to was 120bar, that liked a timing of 22thou.Winter starts have been fine down to -10C.
I did intend to go loweras I haveseen nozzles of this type run at 110bar factory on some engines, but my old nozzles weren't good enough.
The only set of 4 new old stock French ones I had, to do the job, had one faulty one and one pin I managed to break on another. Economy was good, so I left it at that meaning to return in the future.
Physical engine knocking became my obsession.
The big question no-one has asked, is how did I get to these timing figures, that were seemingly so far off the beaten track? I certainly didn't walk into the desert and have a vision, or did I? ;D
Well, I did have a bit of an inspiration, as I was looking for a way of determining 'best timing' I thought perhaps I could look for smoothness of running; so I first listened to engine, and adjusted at idle. Not easy to decide, I then moved on to listening to smoothness of acceleration.
I then combined with finger tips on the shifter, whilst on the road, to feel for smoothness. This was quite good and started giving me lower timing figures. Still this is quite hard in the absence of silky smooth roads. In retrospect, lowering tyre pressures may have helped...
The trouble with these methods is that they required some skill, and time. I wanted something I could do whilst stationary, and with repeatability.
OK another inspiration...
I was looking for maximum economy, so, presumably, by definition that must mean more miles per gallon; so back at the engine surely more revs per gallon.
Thus the jump to the most energy out per injection. This I thought would be reflected in the desire of the engine to want to increase revs.
I just happen to have an analogue rev counter from a truck that by luck works by the W connector, and is both accurate, and has an expanded FSD of only 3500 revs.
To operate, I have it connected in the engine compartment. I raise the revs to about 1000 to 1100, [from around 750] by altering the clip on the accn. cable.
I swing pump until I find a jump in the revs. I then tighten the pump, and hope it stays in the sweet spot.
Strangely, often the revs drop by about 30 when the bottom nut is tightened.
Geeze Mark, you are becoming a diesel whisperer ;D. I hope to try out my pulse unit this weekend after I finish putting a new seal on the Westy pop-top. I was a bit under the weather yesterday and didn't get much done. Do you have any data on what 26 thou (.66 mm) does to your EGT and low-end torque? I'm running four new 155 psi Giles injectors. I believe my old ones were 135.
I also need to switch some probe wires around as I'm getting some odd readings from my intake air and oil temp probes.
Your efforts to push the envelope is commendable but I just want dependability, low end grunt and lower EGT's on long hill climbs. I am still way early on the new rebuild to have any conclusive data though - probably only 20-40 miles so far.
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If you only have 20-40 miles in a couple trips how did it even warm up? The vehicle will run a little bit off until it is warm, at least mine does.
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If you only have 20-40 miles in a couple trips how did it even warm up? The vehicle will run a little bit off until it is warm, at least mine does.
It's warming up. Temp gauge shows 186 steady and I've had the fan come on once. I'm admittedly a bit timid cause there's so many mods I made it's a bit scary ;D
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What engine isnt HOT in 30 miles? Are you bent?
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Those boys above the 48th, they pack their radiators with card board and I bet they still have to do 30 miles to get the heat on. Mine warms up in about 5 miles of city driving. Warm air at the defrosters in like 1/2 mile. And I have extra lengths of hose for the Veg Oil heat exchangers.