crd mileage

Uffe · **Posted:** Fri Jan 18, 2008 5:05 am

groovin1 wrote:

Darby:
Thanks for the info - I have been following the thread. I feel a bit better because I finally was able to get on the highway and check the od, and sure enough 10 miles by the mile markers was 9.5 on my od. Therefore my mileage is a little better than what I was figuring.
I brought my tires back up to 40psi as they went down when it got cold here in NY. I have been using the Standyne additive and I have a K and N air filter installed. Next I will get a grill insert. However, I do keep it in the garage so it never goes below about 58 degrees in there, but I am sure the insert will help.
groovin1

What tyre size are you going on? Sounds very interesting to me as I have debunked my EVIC calculations to be optimistic. Perhaps in reality the EVIC is spot on and the ODO itself is pessimistic. I will look into this with a handheld GPS device when I'm going on a longer trip. Perhaps this weekend.

DarbyWalters wrote:

Now keep speeds to 64 or so in the final OD...about 1800 rpm...you will hit 30+ most likely

You guys are running 3.55 diff gearing with those readings. I'm running 4.10 here. If I do 64ish miles (102ish kph) my engine turn at near-as-makes-no-difference 2000rpm. My sweet spot is 91ish kph (56ish mph) at 1800rpm in second OD(tricked it by going up to 100kph and back to 91ish kph - the programmed hysteresis will keep it in second OD at 1800rpm if I stay above 90kph). I have another option of going 1800rpm in first OD and get about 75kph (46ish mph) I will get same economy from doing that.

Just wanted to chime in with my readings...

groovin1 · **Posted:** Fri Jan 18, 2008 8:13 am

I am using the stock tires - 225/75/R16

Uffe · **Posted:** Fri Jan 18, 2008 9:12 am

groovin1 wrote:

I am using the stock tires - 225/75/R16

Ok I run 235/70 R16 which means my tyres are a little smaller than yours in diameter. There's an 8.25mm difference in diameter of the tyres, so you tyre in total is a whopping 1.1% larger than mine (743.9mm vs 735.4mm)! Since mine are worn as well you probably got 2% bigger diameter. This will lead to a few more revolutions over distance, but probably not enough to counterbalance the pessimistic ODO.

I will soon find out what my measurements are. I'll use my Garmin GPSMAP 60CSx to measure distance and find out what is what.

groovin1 · **Posted:** Fri Jan 18, 2008 10:46 am

I actually already went through that. The speedo is about 1-2 mph over - if it says 45, you are going 43 or 44. The odo is under - if it says you went 100 miles, you really went app. 105. I checked it, and it was also confirmed by a very knowledgeable person on this site. My calculations for the 25.5 mpg included that differential. According to the odo, I got about 24.6 mpg.

DarbyWalters · **Posted:** Fri Jan 18, 2008 11:03 am

Uffe...we have 3.73 gears in out KJ CRDs. Our Speedos say we are going faster than we are and our Odometers say we have traveled less than we actually have...so we adjust. With 235/75/16s my Odometer is 6% off...it says 100miles and I have traveled 106miles...my Speedo says 60mph and I am actually going 58.4mph.

groovin1 · **Posted:** Fri Jan 18, 2008 11:09 am

Darby is the knowledgeable person I was talking about....
Thanks for the exact numbers.

Uffe · **Posted:** Fri Jan 18, 2008 11:59 am

DarbyWalters wrote:

Uffe...we have 3.73 gears in out KJ CRDs. Our Speedos say we are going faster than we are and our Odometers say we have traveled less than we actually have...so we adjust. With 235/75/16s my Odometer is 6% off...it says 100miles and I have traveled 106miles...my Speedo says 60mph and I am actually going 58.4mph.

Ahh my fault. Sorry for that, you're right. I went from memory on the 3.55 thing, but the calculations I just did show that you should have 3.73 gears for the rpm, gear, ratio, tyre size to match up.

I still have the 4.10 ratio though

I will check what my numbers are this weekend - will be fun to compare to your findings. When I compare my hand calculated fuel economy I always rely 100% on the ODO, which led me to believe the EVIC is off by ~0.5l/100km. Now it seems the ODO might be stuffed and the EVIC is spot on. And that is a positive thing, really

dgeist · **Posted:** Fri Jan 18, 2008 12:26 pm

DarbyWalters wrote:

Uffe...we have 3.73 gears in out KJ CRDs. Our Speedos say we are going faster than we are and our Odometers say we have traveled less than we actually have...so we adjust. With 235/75/16s my Odometer is 6% off...it says 100miles and I have traveled 106miles...my Speedo says 60mph and I am actually going 58.4mph.

So, if my calculations are right, you have to have 28.186 inch tires in order for the speedo to be correct? Is this the issue where the odo, speedo, and evic all get data from different places? Which of them are programmable via the computer? It just makes me twitch to know that I have incorrect numbers for EVERYTHING on the CRD...

DarbyWalters · **Posted:** Fri Jan 18, 2008 12:42 pm

Actually a tire that was about 30.44" would correct my speedo( I am still about 2% low with 29.84" tires)...but the odometer would have >6% difference.

A bigger tire would make the SPEEDO more accurate...a smaller tire would make the ODOMETER more accurate.

retmil46 · **Posted:** Fri Jan 18, 2008 12:47 pm

DarbyWalters wrote:

groovin1 wrote:

I always thought higher rpm's means you are burning more fuel. Isn't neutral at a light higher than drive in terms of rpm's?
.......

Why don't you try the suggestion and look for yourself?

I confirmed this one via Scanguage. In drive with your foot on the brake, it's pulling around 1.3 GPH fuel flow. In park or neutral once the engine is warmed up, it's only pulling around 0.6 GPH.

LocoCRD · **Posted:** Fri Jan 18, 2008 1:02 pm

Anybody ever tried gearing to 3.55?

CRDLIBERTY · **Joined:** Thu Aug 02, 2007 11:52 pm **Posts:** 72

Tires i bet over 34 would have been doable with these crds.

DarbyWalters · **Posted:** Fri Jan 18, 2008 3:57 pm

Well with 235/75/16s (29.84"), I am effectively running 3.62 gearing

With a 30.5" tire, you be effectively running 3.55 gearing

dgeist · **Posted:** Fri Jan 18, 2008 5:01 pm

DarbyWalters wrote:

Actually a tire that was about 30.44" would correct my speedo( I am still about 2% low with 29.84" tires)...but the odometer would have >6% difference.

A bigger tire would make the SPEEDO more accurate...a smaller tire would make the ODOMETER more accurate.

So, does that mean for my mileage calculations (assuming I also have a %6 off reference tire) that since I record my mileage from the dash odo, that I should multiply every single mileage reading by 1.06 when I do the math?

Dan

LocoCRD · **Posted:** Fri Jan 18, 2008 6:33 pm

Anybody know if there is a lock out hub we could use on our KJ's?

DarbyWalters · **Posted:** Fri Jan 18, 2008 8:57 pm

dgeist wrote:

DarbyWalters wrote:

Actually a tire that was about 30.44" would correct my speedo( I am still about 2% low with 29.84" tires)...but the odometer would have >6% difference.

A bigger tire would make the SPEEDO more accurate...a smaller tire would make the ODOMETER more accurate.

So, does that mean for my mileage calculations (assuming I also have a %6 off reference tire) that since I record my mileage from the dash odo, that I should multiply every single mileage reading by 1.06 when I do the math?

Dan

Yep...if it says 100 odometer...use 106 for mpg calculations

dgeist · **Posted:** Fri Jan 18, 2008 9:27 pm

DarbyWalters wrote:

dgeist wrote:

So, does that mean for my mileage calculations (assuming I also have a %6 off reference tire) that since I record my mileage from the dash odo, that I should multiply every single mileage reading by 1.06 when I do the math?

Dan

Yep...if it says 100 odometer...use 106 for mpg calculations

Sweet. Just re-did the code that generated my web-based tracker, and I'm liking the numbers a lot more:
http://www.polter.net/~dan/automotive/

CATCRD · **Posted:** Sat Jan 19, 2008 1:37 am

DarbyWalters wrote:

dgeist wrote:

DarbyWalters wrote:

Actually a tire that was about 30.44" would correct my speedo( I am still about 2% low with 29.84" tires)...but the odometer would have >6% difference.

A bigger tire would make the SPEEDO more accurate...a smaller tire would make the ODOMETER more accurate.

So, does that mean for my mileage calculations (assuming I also have a %6 off reference tire) that since I record my mileage from the dash odo, that I should multiply every single mileage reading by 1.06 when I do the math?

Dan

Yep...if it says 100 odometer...use 106 for mpg calculations

Mine was 1.02, by GPS. Stock tires.

Cowcatcher · **Posted:** Sat Jan 19, 2008 12:27 pm

groovin1 wrote:

I thought it was 21 city, 26 highway.
I have been putting it in neutral at stops, and also coasting in neutral when feasible, which is more often than people think. There are spots you can go for a mile or more in neutral even locally.

If you are on a long, steep hill your mileage will actually be higher if you stay in gear and coast rather than shift to neutral. I haven't taken the time to caculate the break even point here but it can be significant if you are monitoring it on a ScanGaugeII.

BlackLibertyCRD · **Posted:** Sat Jan 19, 2008 5:18 pm

Cowcatcher wrote:

groovin1 wrote:

I thought it was 21 city, 26 highway.
I have been putting it in neutral at stops, and also coasting in neutral when feasible, which is more often than people think. There are spots you can go for a mile or more in neutral even locally.

If you are on a long, steep hill your mileage will actually be higher if you stay in gear and coast rather than shift to neutral. I haven't taken the time to caculate the break even point here but it can be significant if you are monitoring it on a ScanGaugeII.

I tried doing that downgrade through the passes and found I had to use my brakes too much. With the trailer connected behind me I must of looked like a freight train coming up from behind to a few poor souls. :twisted:

crd mileage

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