GDE fuel economy

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

The viscous heater is not timed and will turn on based on engine rpm, ambient temp and coolant temp. The second two are the most important factors. A stock CRD has the following settings to have the VH on: ambient temp below 53.6 F and coolant temp below 161.6 F. With the tune the new limits are: ambient temp below 44.6 F and coolant temp below 131 F.

The fuel economy gain is minimal if the thermostat is working properly and the vehicle is not idling for a ling time or running at very light loads. However, with an old thermostat it is possible to have the stabilized coolant temps in the winter in the range of 155 F to 160 F and in this case the VH will stay on indefinitely. This is where the new settings will have a greater impact on the fuel economy.

The largest driver for improved fuel economy with the tune is the optimized combustion parameters (injection timing, boost and pilot injection quantity). Hopefully this will clarify the VH changes.

GreenDieselEngineering · **Joined:** Sun Jun 07, 2009 5:10 pm **Posts:** 1111

Rixram,

The stock KJ CRD thermostat starts opening at 176 F and is fully open at around 191 F. This is much lower than virtually every other diesel we have tested, most others have opening temps in the range of 194 F to 210 F. To our knowledge there is not drop-in replacement available on the market to increase the thermostat opening temp. This is the main reason some on the forum are investigating mods to the existing t-stat to allow the installation of a higher opening element.

Rixram · **Posted:** Wed Mar 24, 2010 11:09 am

GreenDieselEngineering wrote:

Rixram,

The stock KJ CRD thermostat starts opening at 176 F and is fully open at around 191 F. This is much lower than virtually every other diesel we have tested, most others have opening temps in the range of 194 F to 210 F. To our knowledge there is not drop-in replacement available on the market to increase the thermostat opening temp. This is the main reason some on the forum are investigating mods to the existing t-stat to allow the installation of a higher opening element.

How difficult is it to reach the t-stat? Has anyone considered modifying (nudge towards GDE) an existing t-stat to work in this spaghetti-diesel?

BVCRD · **Posted:** Wed Mar 24, 2010 11:09 am

Sorry, posts not showing up.

Rixram · **Posted:** Wed Mar 24, 2010 11:27 am

DOC4444 wrote:

BVCRD,

Based on my experience, I think it will be worth your trouble to drive for 10 minutes in sub-40 degree weather, pop the hood and confirm that the VH has disengaged as you think it should have. (Just make sure you look at it on cold startup so you can tell the difference between when the clutch is engaged and it is not engaged.) Even if you find your particular CRD disengages the VH this quickly, I do not think that is typical of most CRDs.

BTW, GDE has a track record of not offering "baloney" tweaks. They would not include the VH mod if their winter testing did not show that the stock VH settings result in excessive VH operation, compromising winter fuel economy.

DOC

Hmm. I may have been referring to DOCs own post. My bad.

kapalczynski · **Posted:** Wed Mar 24, 2010 8:38 pm

Rixram wrote:

GreenDieselEngineering wrote:

Rixram,

The stock KJ CRD thermostat starts opening at 176 F and is fully open at around 191 F. This is much lower than virtually every other diesel we have tested, most others have opening temps in the range of 194 F to 210 F. To our knowledge there is not drop-in replacement available on the market to increase the thermostat opening temp. This is the main reason some on the forum are investigating mods to the existing t-stat to allow the installation of a higher opening element.

How difficult is it to reach the t-stat? Has anyone considered modifying (nudge towards GDE) an existing t-stat to work in this spaghetti-diesel?

Currently working on a simplified thermostat housing with replaceable thermostats in temps of 180* and 192* which are both hotter than the factory 176*.

http://www.lostjeeps.com/forum/phpBB3/viewtopic.php?f=5&t=50940

I hope to have a operational prototype by this weekend. However, I just purchased the GDE tune and will be installing a new timing belt/ waterpump this weekend along with the tuned ECU. I want to run a tank w/ the old thermostat first, and then run my new design to get an economy comparison.

The new thermostat setup should run under $100 and include new upper radiator hose, gaskets, etc and choice of 180* or 192* temps.

CATCRD · **Posted:** Thu Mar 25, 2010 6:05 pm

I'm pretty sure my thermostat is opening too early. My water temp won't go over 161 even with the grille totally blocked, driving in traffic on a mild day.

kapalczynski · **Posted:** Thu Mar 25, 2010 6:20 pm

CATCRD wrote:

I'm pretty sure my thermostat is opening too early. My water temp won't go over 161 even with the grille totally blocked, driving in traffic on a mild day.

Sounds like its toast. I'd expect your fuel economy to be down running that cold too.

LibertyCRD · **Posted:** Wed Apr 21, 2010 11:32 am

Another update:

I have about 4,000 miles or so on the HOT tune now. The weather is getting warmer now, and the winter fuel should be phased out by now leaving us with better stuff at the pumps.

I've gotten some highway and interstate trips in...and I am averaging around 26 MPG when I spend a lot of time cruising around 65-75 MPH.

Still trying to get a good feel for what my MPGs will be on Summer fuel during my normal driving cycle...but it appears that somewhere in the 23-24 MPG ballpark would be accurate at this point.

In both cases (normal driving cycle and interstate/highway)...my MPG is IDENTICAL to what I was getting with my previous CRD BONE stock 5 years ago before ULSD fuel.

So to recap: '05 CRD Sport, 100% stock engine (not even a ProVent), straight-thru muffler, Daystar lift spacers, 255/70-16 Grabber AT2s, slightly more aggressive driving style = 23-24 MPG normal / 26 MPG interstate

'05 CRD Limited, EHM, GDE HOT tune, removed clutch fan, Euro TC, Daystar lift spacers, 255/70-16 Grabber AT2s, more conservative driving style = 23-24 MPG normal / 26 MPG interstate

I am not seeing much improvement in economy at all with the GDE tune...especially when you consider that I have also removed the fan and I'm driving more conservative now than I did 5 years ago. Possible reasons for this: stock muffler vs. straight pipe/Magnaflow that I used to have OR ULSD fuel to blame?

stoutdog · **Posted:** Wed Apr 21, 2010 2:43 pm

Well, the lift spacers and more aggressive tires probably knock a couple of mpgs off... Plus, what is your definition of conservative driving style? Around town, I keep it under 2000RPMs when accelerating, and do so smoothly and gradually. This nets me 26-28mpg in mixed driving, with a good portion of that being 10 minute trips down the interstate.

On longer trips, 60mph = 33-35mpg; 70mph = 30-32mpg and 75mph = 29mpg. I probably saw a gain of about 3-5mpg from the tune, most of which would've been negated by installing a lift and AT tires.

Other thoughts:
- Try running PowerService (silver bottle) for a couple of tanks. Clogged injectors could be lowering your mileage significantly
- What psi are your tires at? I keep mine around 40-44.
- Is your air filter clean? I check my Amsoil reusable at every oil change
- Consider cutting out the muffler; I don't know if it improved my mpg, but it didn't hurt
- Check your MAP sensor

Hope that helps... :JEEPIN:

PhoenixCRD · **Posted:** Wed Apr 21, 2010 3:01 pm

LibertyCRD wrote:

Another update:

I have about 4,000 miles or so on the HOT tune now. The weather is getting warmer now, and the winter fuel should be phased out by now leaving us with better stuff at the pumps.

I've gotten some highway and interstate trips in...and I am averaging around 26 MPG when I spend a lot of time cruising around 65-75 MPH.

Still trying to get a good feel for what my MPGs will be on Summer fuel during my normal driving cycle...but it appears that somewhere in the 23-24 MPG ballpark would be accurate at this point.

In both cases (normal driving cycle and interstate/highway)...my MPG is IDENTICAL to what I was getting with my previous CRD BONE stock 5 years ago before ULSD fuel.

So to recap: '05 CRD Sport, 100% stock engine (not even a ProVent), straight-thru muffler, Daystar lift spacers, 255/70-16 Grabber AT2s, slightly more aggressive driving style = 23-24 MPG normal / 26 MPG interstate

'05 CRD Limited, EHM, GDE HOT tune, removed clutch fan, Euro TC, Daystar lift spacers, 255/70-16 Grabber AT2s, more conservative driving style = 23-24 MPG normal / 26 MPG interstate

I am not seeing much improvement in economy at all with the GDE tune...especially when you consider that I have also removed the fan and I'm driving more conservative now than I did 5 years ago. Possible reasons for this: stock muffler vs. straight pipe/Magnaflow that I used to have OR ULSD fuel to blame?

Sorry to hear your mileage didn't improve. My wife took over the Liberty (stock except for the SEGR & transmission cooler) and was getting about 24.5 mpg. The first tank after the hot tune netted 27.5, mixed rush-hour city-freeway driving. I'm anxious to see what straight highway mpg is going to be.
Gary

Rixram · **Posted:** Wed Apr 21, 2010 6:02 pm

I just installed my ECO-tune this morning.

I also changed my oil, and was disgusted at the results of that. I swapped the 5w-40 for 20w-50 to increase the compression keeping ability and cut blow-by. Will let you know how well that works out.

I also re-routed my Crankcase oil pressure line last weekend. Plugged the original input, and rerouted it to the air-box, so it is now upstream of the air filter, versus downstream. The kind of crap that was in my oil, and picturing that running back through my engine, or vented to the outside? No thanks. I figure If I need to clean my air-filter every oil change, it's no big deal.

I am a bit concerned about changing the oil to that high of weight, but I am definitely have noticed less oil crankcase stench around the vehicle now. Muy Bueno!

Thoughts on the change of the oil?

CATCRD · **Posted:** Wed Apr 21, 2010 8:35 pm

So you re-routed crank case fumes to go through your air filter? It's going to get wet, oily and messy in there. Check it soon.

stoutdog · **Posted:** Wed Apr 21, 2010 9:03 pm

CATCRD wrote:

So you re-routed crank case fumes to go through your air filter? It's going to get wet, oily and messy in there. Check it soon.

x2. You're going to ruin your air filter in no time... And I wouldn't run 20w-50; not when the service manual specifically states 0w-40 or 5w-40. That is far too significant a change for me...

LibertyCRD · **Posted:** Wed Apr 21, 2010 9:50 pm

stoutdog wrote:

Well, the lift spacers and more aggressive tires probably knock a couple of mpgs off... Plus, what is your definition of conservative driving style? Around town, I keep it under 2000RPMs when accelerating, and do so smoothly and gradually. This nets me 26-28mpg in mixed driving, with a good portion of that being 10 minute trips down the interstate.

On longer trips, 60mph = 33-35mpg; 70mph = 30-32mpg and 75mph = 29mpg. I probably saw a gain of about 3-5mpg from the tune, most of which would've been negated by installing a lift and AT tires.

Other thoughts:
- Try running PowerService (silver bottle) for a couple of tanks. Clogged injectors could be lowering your mileage significantly
- What psi are your tires at? I keep mine around 40-44.
- Is your air filter clean? I check my Amsoil reusable at every oil change
- Consider cutting out the muffler; I don't know if it improved my mpg, but it didn't hurt
- Check your MAP sensor

Hope that helps... :JEEPIN:

I did run multiple tanks with PowerService recently. Tires are at 38 lbs. which is actually WAY too much for a vehicle of this weight but I'm doing it for the economy benefit. Air filter is new. MAP sensor removed and cleaned.

What I can't understand is why two CRDs, built in the same month, with the exact same tires would get the exact same mileage when one was bone stock otherwise, and the other is heavily modified for economy including a GDE tune.

Also...by conservative driving I mean cruising at 59 MPH whenever possible because that's the slowest speed I can drive and keep 5th in lockup....accelerating from stop lights so slowly that people flip me off....shutting the engine off in drive-thrus if the wait is long, etc. Despite all this...my mileage hasn't budged. AND...this engine is more broken in than my previous CRD that was new at the time. Just makes no sense.

All I can figure is the ULSD fuel now days is garbage or maybe my stock muffler needs to go. I'm not seeing the 3-4 MPG improvement that many people are seeing.

OH...and my EVIC is anywhere from 1 to 4 MPG too high. Usually 2....but I've seen it from 1 to 4 off. So I hand calculate everything. It's important to note that in every other aspect I am very happy with the tune. GDE made this Jeep more enjoyable in every way. I just wish I could see the mileage benefit too.

geordi · **Posted:** Wed Apr 21, 2010 9:59 pm

You will be replacing your turbo (before the air filter) with oil that heavy. Too heavy to lube the turbo properly, especially when cold. The lack of cold oil lubrication is what killed my turbo, followed rapidly by the engine b/c I didn't know what had happened when it died. Also, making your pistons slog through that stuff will NOT "help your compression" but what it WILL do is destroy your existing MPG to the tune of losing another 2-3mpg at a minimum.

Short story: GET THAT OIL OUT OF THERE ASAP. It cost me $8000 to learn that lesson. You just got a bargain for it: the cost of an oil change.

As for the rest...

Where do you figure that 38psi is "too much" for the tires? Do you have 35-psi sidewall max Goodyear passenger CAR tires? I'm running 215/85/16 BFG tires, sidewall max is 80psi, I generally run them around 60. You need more air or better tires... Probably both, and then you will see some better economy from that. Tall and narrow is the way to go.

Lose that stock muffler PRONTO. It is a 60-lb sandbag under your CRD, and a Flowmaster from Advance Auto will give you MUCH better performance, the same quiet, at only about 15 lbs.

stoutdog · **Posted:** Wed Apr 21, 2010 10:01 pm

Well, you've got me stumped... That doesn't take much, though :juggle:

It's not the ULSD fuel. Everybody else is running the stuff, as well.

CATCRD · **Posted:** Wed Apr 21, 2010 10:03 pm

LibertyCRD wrote:

I did run multiple tanks with PowerService recently. Tires are at 38 lbs. which is actually WAY too much for a vehicle of this weight but I'm doing it for the economy benefit. Air filter is new. MAP sensor removed and cleaned.

What I can't understand is why two CRDs, built in the same month, with the exact same tires would get the exact same mileage when one was bone stock otherwise, and the other is heavily modified for economy including a GDE tune.

Also...by conservative driving I mean cruising at 59 MPH whenever possible because that's the slowest speed I can drive and keep 5th in lockup....accelerating from stop lights so slowly that people flip me off....shutting the engine off in drive-thrus if the wait is long, etc. Despite all this...my mileage hasn't budged. AND...this engine is more broken in than my previous CRD that was new at the time. Just makes no sense.

All I can figure is the ULSD fuel now days is garbage or maybe my stock muffler needs to go. I'm not seeing the 3-4 MPG improvement that many people are seeing.

OH...and my EVIC is anywhere from 1 to 4 MPG too high. Usually 2....but I've seen it from 1 to 4 off. So I hand calculate everything. It's important to note that in every other aspect I am very happy with the tune. GDE made this Jeep more enjoyable in every way. I just wish I could see the mileage benefit too.

How's your thermostat? Do you have a scanner that can look at actual coolant temp? I wonder if a lot of people are getting low mileage because of running too cool.

LibertyCRD · **Posted:** Wed Apr 21, 2010 10:50 pm

T-stat seems to work because the Jeep runs at the mark before mid-point most of the time. Sometimes it will hit the half-way mark if I work it hard.

As far as tires...the rating on the sidewall is the MAX the tire can withstand. It is NOT in any way what you should run in the tire. The pressure you need is a product of A) How much volume your tires can hold and B) How heavy your vehicle is. With 255/70s you have more volume because the tire is larger...which means you can run less pressure to support the weight of the Jeep. Also...these Jeeps only weigh 4,300 lbs. So if you actually do the research...you'll see that pressures in the upper 20s PSI range is plenty!! The stock rating was 35 PSI..but that's with small tires with flimsy sidewalls. Anybody running 60 PSI in tires on a Jeep....well, that's just scary. Has to ride like a log wagon too. :shock:

I guess my next mod will be to do something with this exhaust. I'm not straight-piping though...I didn't like that ricey sound at all last time. :oops:

geordi · **Posted:** Wed Apr 21, 2010 11:12 pm

You are the first person to ever discuss the volume of the tire when talking about the proper air pressure. While I can get the rim to lift off the ground with merely 10psi in the tires, would I ever run the tire at that? Even if I had 355mm-wide tires which possibly could support the weight at such a low pressure... No. You are missing a KEY fact in your calculation: We might be in a 4300lb Jeep... But that is only the static weight. When you add in the physics of "live loading" on the tires caused by cornering, starting, stopping.... The individual tires are NOT supporting 1/4 of 4300lbs, they could be supporting as much as DOUBLE the entire weight of the truck!

You are correct in that the sidewall max is what the tire manufacturer has rated the tire for. Tire makers do NOT rate their tires for specific much-lower-than-max pressures, b/c of the difficulty of calculating that live loading. What is on the tire placard on the KJ is ONLY for the stock tires, NOTHING ELSE HAS BEEN TESTED, and should you get in a roll-over with an 80-psi-capable tire that you have decided to operate at 35psi... The tire manufacturer WILL hang you out to dry for operating their tires at less than 50% of the rated pressure. This will cause excessive sidewall flex and heating of the tire, glue failure, improper wear (which my tires are wearing square) and possible blow-out. Remember the Ford / Firestone mess? That was b/c Ford had taken a strong-enough tire and rated it themselves at about 60% of the tire's max pressure... And they were overheating and blowing out causing wrecks.

Your tires are not the main component of the suspension system, and should not be treated as such. You want a softer ride? Change the springs and shock rates... Or buy a passenger car. My CRD does not ride like a "log truck" as you put it. I would be happy to let anyone drive or ride in my CRD to try it out. This has been a standing offer since I got these tires. The on-road performance is crisp and precise, rather than the wallowing and drunken handling of my CRD on the stock tires.

Good luck with your 20psi setting. Be sure to let Sir Sam know when you wreck your CRD so he can rebuild it.

GDE fuel economy

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