Sonnax Electric Line Booster for 545RFE Transmissions

geordi · **Posted:** Mon Jan 04, 2010 8:22 pm

I know my turbo is not putting out as high of pressure as it should be, since I'm fairly certain that the controller solenoid is losing its grip. BUT... That doesn't explain the RPM differences the OP reported. Once the transmission is into 5th and the converter locks up... 75mph should be 2200~ rpm, not a lot lower than that.

The only other explanation for the RPM differences was if the differentials were somehow changed out to numerically lower gears. (taller) If that is the case, I want to know how much, and what new gearsets were installed. Taller gears in the pumpkins are similar to much taller tires on the wheels - Slower engine speed at the same road speed, at the expense of using more torque and slower acceleration. For a torque-happy monster like our engines tho... This could be a way to better mileage, IF the gearing was available.

Randy B · **Posted:** Fri Jan 22, 2010 11:04 am

Well here is my feedback on this mod. Fuel mileage has not changed. Under a heavy load the trans shift is more pronounce. Have not towed with this mod yet. Seems that it shifts out of overdrive faster on throttle responce on the highway. Still getting 22 mpg by miles driven and gallons used. Not by the onboard computer, it says about 24 to 25. Here in Maryland where I live it is very hilly and when pulling a hill you can feel it shifts out of overdrive faster than before. I feel that if you tow this might be a mod to consider. As for driving I do feel the change. To me the $50.00 spent was worth it. Just my FYI :idea:

dieseldoesit · **Posted:** Fri Jan 22, 2010 2:46 pm

DOC4444 wrote:

Regarding the EVIC displaying higher mileage @ higher RPMs:

1. It seems very unlikely any diesel would return higher mileage at higher engine speed, everything else being equal.

2. When I was driving a couple of years ago to a friend's shop to install a Cummins lift pump, I realized I had forgotten to run the tank level down to minimize the weight we were going to have to deal with when we dropped the tank. So, I drove at close to the redline for 45 minutes on the highway to get rid of as much fuel as possible. Much to my suprise, the EVIC displayed significantly higher mileage readings than I had ever observed before under ANY conditions. I wrote it off at the time to some sort of glitch in the system, assuming that could simply not be possible. But, now that I think about it, what about all those people reporting towing in lower than OD fifth lockup and getting better mileage, running higher RPMs than they could?

DOC

Good points. Fuel millage has much more to do with load (throttle setting) then just rpm. The amount of fuel required to increase rpms with no load is very small (think hitting gas pedal in park).

007husky · **Posted:** Fri Jan 22, 2010 3:30 pm

Would this be the same as the resistor that comes with the transgo kit ? ?

From the pictures, it doesn`t seem they could add a lot of logic within the plug itself...

LibertyCRD · **Posted:** Fri Jan 22, 2010 4:04 pm

Yes MPG has a LOT more to do with engine load than RPM. You can drive downhill at 80 and use less fuel than driving uphill at 50. Many times higher RPM will equal better MPG because the engine isn't working as hard. That's why the idea of 3.07 gears in a Jeep or truck like they are using now days is a ridiculously stupid idea. Do engineers actualy test these things in the real world??

As far as the OP saying his RPMs at 80 went up after the install...sounds to me like maybe the converter isn't staying locked up now and that is BAD. :grim:

CATCRD · **Posted:** Fri Jan 22, 2010 4:22 pm

007husky wrote:

Would this be the same as the resistor that comes with the transgo kit ? ?

From the pictures, it doesn`t seem they could add a lot of logic within the plug itself...

Yes, all it is is a resistor.

geordi · **Posted:** Fri Jan 22, 2010 7:41 pm

LibertyCRD wrote:

Yes MPG has a LOT more to do with engine load than RPM. You can drive downhill at 80 and use less fuel than driving uphill at 50. Many times higher RPM will equal better MPG because the engine isn't working as hard. That's why the idea of 3.07 gears in a Jeep or truck like they are using now days is a ridiculously stupid idea. Do engineers actualy test these things in the real world??

I have to disagree with that. Higher RPM is a means to deliver more torque during a given time segment (lets say one minute to make the math easy) when the available torque is not where it should be for the load.

Hamster-wheel motors like on your average honduh are rated with insane HP numbers b/c per-rev they only have a minuscule amount of torque... So they spin said engine up to 9000 RPM to try and cram more events into the same time. Big truck motors NEVER spin over 1500 rpm, b/c the per-rev work is so much more, and they have 500hp motors, but 1500 lb-ft of torque.

It is a fairly simple relationship. Which does more actual WORK - Transporting dirt in a wheelbarrow slowly, or in a teacup 10x faster? The burn rate of the fuel (specifically diesel here) will be EXCEEDED by the RPM over a certain limit, which I tend to believe is about 2000 rpm. Generators are tuned to spin at 3600 rpm... Except diesels. Those are at 1800rpm. Big trucks, no faster than 1500rpm. Yes, our little motors (and the TDI too) can spin faster, but are we REALLY doing more work, or forcing the fuel to complete it's combustion inside the turbo?

Give the fuel the time it needs INSIDE THE CYLINDER to burn and make it's power. To do that, you have to spin it slower, with more transmission gears and taller differentials.

GM, the great avoider of innovation bucked and moaned for YEARS about putting a THIRD GEAR into their transmissions. Was it about efficiency? NOPE! They didn't give a rip about that, despite whatever the engineers wanted. It was about not spending that extra $1 to install that gear, which wouldn't 'make' the company any money directly.
Ford pulled the same nonsense with International, by flatly IGNORING International's directions for the Powerstroke engines. Don't spin them faster than 3500, put more gears in to keep the RPM even lower for durability and longevity.

Ford's answer? 4 speed transmission and 4.56 rear end so at 70mph, the engine was turning 4000+ rpm. Gee, wonder why the engines started failing? Ford knew better, b/c spinning the engine faster makes the HP number go up, and causes spontaneous 'bodily enhancement' of the driver.

The Engineers at International TOLD THEM what to do... The marketing wonks told the Ford builders to do something different to lower the efficiency, but make the on-paper numbers look sexier. Which is why we will NEVER have another small diesel from an "American" car maker. American car marketer's answer: "Didn't you know that nothing with less than 8 huge cylinders can tow more than 1000 lbs? Certainly a 4-cylinder can't ever tow 7000 lbs... That diesel Jeep must be 'modified' or something. It can't do that."

ATXKJ · **Posted:** Fri Jan 22, 2010 9:06 pm

3.07's work really well on the highway, you just can't accelerate with them
but official mileage figures were (are?) at steady state - they don't measure acceleration

stoutdog · **Posted:** Fri Jan 22, 2010 9:48 pm

geordi: Question. Are you saying that our CRDs operate at peak efficiency @ 1800rpms? After that, we are not allowing the fuel to combust fully?

Sorry if I read you completely wrong... :dizzy:

MrMopar64 · **Posted:** Fri Jan 22, 2010 10:24 pm

Official "window sticker" numbers are generated by running the vehicle through a certain series of tests (EPA75, FTP HWY, and US06). The 75 mimics in-town start-stop traffic, the highway is self-explanatory, and the US06 is a lot of heavy accelerations. The results of these tests are weighed in certain ways to come up with final numbers that determine emissions compliance and also your fuel economy rating. All vehicles run the same test on an electric eddy-current dyno where the dyno rollers give the correct loading to simulate the coast-down (road-load) of the vehicle.

A numerically lower gear ratio does sacrifice some "performance" but the fuel economy gains far outweigh the sacrifice. Towing usually isn't compromised except for maybe launchability on a grade, otherwise you just downshift a gear and go. Spinning the engine slower is always the way to go, regardless of the ignition type (compression or spark).

For the fuel economy, your best fuel economy will always come when you operate the engine speed at the point of lowest BSFC (Brake Specific Fuel Consumption). At this point, you maximize the energy conversion from the fuel into power generated by the engine. This point always comes at the peak torque and continues to rise all the way to the peak power point. The burn rate of the fuel isn't really a factor since that is optimized by injection timing. Since the burn rate of the fuel is more or less constant, this is why you continue to advance the timing of the start-of-injection so that the combustion event happens are more or less the same point relative to crank angle.

geordi · **Posted:** Sat Jan 23, 2010 12:03 am

stoutdog wrote:

geordi: Question. Are you saying that our CRDs operate at peak efficiency @ 1800rpms? After that, we are not allowing the fuel to combust fully?

Sorry if I read you completely wrong... :dizzy:

Mr Mopar explains it more scientifically than I did, but basically... My experience has been that the peak torque point on a small diesel engine (I've only owned the TDI and the CRD, and worked directly with non-adjustable diesel and gas gensets) is right in the 1800-1900rpm ballpark. On the TDI, the torque peak was at 1800. Someone would have to come up with a dyno chart for the CRD to see if it is at the same spot, but my point was what MrMopar said: The best economy is found at the peak torque, where the fuel is being completely converted to energy.

There is a modest rise in most dyno charts above that point to the peak 'power' point of HP... But is that trade off worth it? The torque curve is beyond it's peak, so you are merely applying less power, faster. Every time you accelerate, you have to ramp up that mechanical spinner to get to that much higher RPM.

Here is a thought experiment for you. Generators, trains, big ships are all diesel motors that operate at steady-state (like cruising on a highway for us) for extended periods. It doesn't really matter what the specific job at the other end of that crankshaft is, it's a power demand. In a very real way, if the power band continues to rise above the torque peak, why not spin a generator at 2500 or 3600rpm, or a big ship's diesel at 4000 rpm, if that is where the HP peak is at?

Because at that point, you aren't effectively combusting the fuel. HP does not equal torque, it is the application of torque over time. For motive performance, it is more of a marketing gimmick or a definition of how quickly you can accelerate to the next traffic light. A big ship or a generator needs the engine to produce WORK, which is torque. As long as that torque is sufficient for the job, the application speed is more a question of desired function. Big ship generators make BIG BIG torque numbers... At maybe 200-500 rpm. Portable generators are much smaller, so can get proper combustion (torque peak) at 1800 rpm, and are geared to double that speed at the powerhead, b/c our USA power is 60 hz, or exactly 3600 rpm.

My CRD isn't a drag racer, but it does accelerate plenty fast for my needs. I would HAPPILY drop down to 3.02 gears or whatever the number is close to that, for the economy offered. I want my CRD to be as close to it's torque peak as possible for the speeds that I drive, which is usually between 70 and 80 depending on the road. The economy WILL go up at those speeds, IF the RPM can be brought down closer to the torque peak number.

blacksmoke · **Posted:** Sat Jan 23, 2010 1:28 am

Glad you put the "generators are running at 3600rpm because" its 60hertz (60 times/sec) x 60sec

Saved me from saying it (well I just did anyway).

You're right, any engine is most efficient when the max torque is reached, which according to the older VM Motori literature is 1800rpm but when looking at the current site info is 2000rpm. That's why CVTransmission is efficient, they keep the engine on the sweet curve and adjust the final ratio accordingly; too bad it can't absorb so much torque!

Now if only I could put a nice 6speed manual transmission and do that job myself instead of relying on that 545RFE

In the meantime I'm thinking about trying that $50 solution

stoutdog · **Posted:** Sat Jan 23, 2010 1:30 am

geordi wrote:

My CRD isn't a drag racer, but it does accelerate plenty fast for my needs. I would HAPPILY drop down to 3.02 gears or whatever the number is close to that, for the economy offered. I want my CRD to be as close to it's torque peak as possible for the speeds that I drive, which is usually between 70 and 80 depending on the road. The economy WILL go up at those speeds, IF the RPM can be brought down closer to the torque peak number.

Okay, I think I follow. Thanks.

So here's a question for you, can we run 3.02 gears? I hear "gear" numbers thrown around a lot and, forgive my car-tech noobishness, but what the heck do they mean? :?:

In other words, is changing your gear ratio actually a feasible upgrade?

Thanks! :POPCORN:

stoutdog · **Posted:** Sat Jan 23, 2010 1:37 am

Fyi, these are our torque v. hp #s, from GDE:

So does this mean that we should get our best mpg at ~2000 rpms? Cause I have a good bit of actual data that shows a significant drop in mpg between 60mph (1800rpms) and 70 mph (2100rpms)

blacksmoke · **Posted:** Sat Jan 23, 2010 1:47 am

Yes it's optimum at 2000rpm, but only on a roller bed! Going faster in real life mean more drag, and we know how the Liberty is more a "barn door" than a water droplet when related to air-coefficient.

All of that to say you're most efficient at 55mph than 60mph than 70mph even if you can manage 2000rpm at each speed, give or take a bit.

geordi · **Posted:** Sat Jan 23, 2010 2:27 am

I'm inclined to believe that the MPG will go up. Here's the thing: Wind resistance is a factor, not gonna get away from that. But the physics of it says that wind resistance quadruples with (IIRC) the square of the speed... But when we are talking about less than a 20% change in speed (60-72 would be 20%) then the wind shouldn't be that much of a factor.

But even if it is... The increase in available torque by lowering the RPM back to the torque peak means that the engine might be injecting the exact same amount of fuel as with the higher-number gears... BUT it will be injecting it less per minute, AND be doing more work (faster speed) than simply slowing down would have.

Logically, if you lost 2mpg by increasing speed to 70 from 60... You should see at least half that come back, b/c you are still asking it to push the same wind at the faster speed, but you are injecting less cycles of fuel to do it, and asking that fuel to more completely convert to energy.

nescosmo · **Joined:** Sat Jul 14, 2007 11:17 pm **Posts:** 202

My two p. I think that speed is not in direct proportion to rpm and torque.
If a generator or any engine it peek performance is at 2k rpm and the engine go to that rpm from the start then to stay there it will need more fuel if the load increase and so is it torque.
So you could have less use of fuel at higher rpm if the load is low to mantain that rpm.
maybe i am wrong but that is what i think.

LibertyCRD · **Posted:** Sat Jan 23, 2010 10:10 am

I keep a spreadsheet and log my mileage religiously. I use the EVIC and hand calculate each time. My EVIC is (and has been with all my Chrysler products) perfectly accurate.

Also, I have regeared a lot of Jeeps and trucks. EVERY time I put lower (numerically higher) gears in....my fuel economy goes UP. I drive 50/50 city/highway. In one case, I had a Jeep Wrangler that increased 4 MPG after going from 4.11 to 4.88 gears! Most of the time I pick up 1-2 MPG on vehicles though. So I know for a fact that in the real world....numerically lower gears do not equal better MPG. Why? Again...the engine doesn't work as hard. Its like riding a bike...the lower the gear the less you sweat.

ATXKJ · **Posted:** Sat Jan 23, 2010 10:59 am

The common factor in that spreadsheet is the driver
Which is why the official tests are done on a controlled dyno - it eliminates that factor.

it's very easy to push a little harder on the accelerator pedal and burn a lot more fuel.

LibertyCRD · **Posted:** Sat Jan 23, 2010 11:31 am

That's why in my sheet I have a field for driving style, weather conditions, aftermarket parts added, etc. to account for this. I also have a field for where I fill up and I try to put the same amount in each time. So I can wash out any error pretty well.

The biggest fuel economy gains I've seen are from going with numerically higher gears. The second biggest is from going to an electric fan.

Sonnax Electric Line Booster for 545RFE Transmissions

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