- Location
- Northwest Ohio
today it was in open till the coolent hit 100 deg, so i guess i didnt see it the first time
Fuel Economy/ScanGaugeII Discussion
- Thread starter BBeach
- Start date
- Location
- Northwest Ohio
BBeach, when i have one of the guages set on TPS mine jumps like 16 or more when im idleing and it jumps like 10 or more when im driving, does yours do this too?
- Location
- Northwest Ohio
Only problem is mine doesnt do it every now and then it does it like every 5-15 second or is that about what yours does
- Location
- Northwest Ohio
Good i thought my TPS was going crazy and the FSM says that you should not attempt to change the idle with the screw on the throttle body(whoops lol) and Idle is controlled by the PCM so i guess their is no way to adjust it, maybe you could try and clear the adaptive memory here a link to the directions http://www.mhjcontherocks.com/Community/TechWriteUps/196.aspx
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"The last dyno run I did was performing after I flashed the PCM Adaptive Memory while on the dynamometer. We then ran the test again, using in essence the Base Setting that come in the PCM from the factory. This resulted in a loss of 9 HP and 17 ft/lbs of torque."XJ01-08 said:
Idk how good of an idea that sounds. What do you get for MAP and GPH when idling? I
m usually at 6-7psi and .80-90 gallons per hour. I hope mines not too high..
- Location
- Northwest Ohio
I did it do mine just because i swapped out my head and riped off the precats, off the top of my head the GPH sounds about right but ill check it today
- Location
- Northwest Ohio
Yours are all about the same range as mine.
Just curious what you guys thought of this. I get about 22-23mpg average on the highway when going 60-65mph. However, I lost O/D on my last trip home, and not having much time since i had an interview i just kept driving at 2500rpm at 60mph. The reason I did this, was the scangauge was telling me I was getting almost the same fuel economy. Now this is something I was thinking of for a while, is the your fuel efficiency is dependent on your load, how much force you need versus how much you provide, etc etc. So I figured that with the additional thrust from the lower gear (3rd), that despite the increase in rpms (within reason...this didn't work past 3k or so) it helped balance out the drag on my jeep decently.
Some stats I found interesting other than the increase in mpgs. The load seemed to be a little lower than the usual, the TPS was less, as with the MAP and my ignition timing jumped from 35btdc ot 45btdc. At first I thought the jump was because the engine was spinning faster, less time for the fuel to mix, etc etc but when I'm doing 75-80 when I had 4th gear, it was ~36-38 or so. I guess as a rule of thumb, if you have more ignition advance (lots of variables to this statement), that you are going to have better vehicle efficiency. Take it or leave it, but one of these days I'll do a "load required" vs vehicle speed graph and see how I could match my gearing/tires to optimize mpgs (at least highway).
Any opinions or input?
Some stats I found interesting other than the increase in mpgs. The load seemed to be a little lower than the usual, the TPS was less, as with the MAP and my ignition timing jumped from 35btdc ot 45btdc. At first I thought the jump was because the engine was spinning faster, less time for the fuel to mix, etc etc but when I'm doing 75-80 when I had 4th gear, it was ~36-38 or so. I guess as a rule of thumb, if you have more ignition advance (lots of variables to this statement), that you are going to have better vehicle efficiency. Take it or leave it, but one of these days I'll do a "load required" vs vehicle speed graph and see how I could match my gearing/tires to optimize mpgs (at least highway).
Any opinions or input?
alex22
NAXJA Forum User
- Location
- CT: waterbury area
I was thinking about that a few weeks ago. I have a 96 with a 5spd so I just didn't go into 5th for two weeks. I was just using the non scientific method of looking at the gague move. I didn't notice any change in mileage. It was mostly country driving in CT with all the short windy roades, not much highway use.
~Alex
~Alex
Theres more to it than that i'd think. But there would be more vacuum due to the throttle being opened less. At the same time wouldnt that mean there would be less of a mass of air going in than we would think? As in, I know the rpm is 25% or more higher, but it also has less pressure so thatd be how it wouldnt be such a large drop in mileage. But the whole point of what im trying to say, is that the timing is advanced and itd be more efficient despite the higher rpms. I think its just a huge force balance kind of thing and we just need to match our force output as best we can.srimes said:
The simple explanation is that it take a specific amount of power to maintain speed under specific conditions. Lets say it takes 20 hp to cruise at 60. The 4.0 can probably make the required 20 hp at at any RPM above idle. Remember that at cruise it doesn't matter how much power the engine can make, as the power is throttled back to match the requirements.
If the engine's effecincy didn't vary you'd get the same mileage at 60 if it was turning 1600 rpm, 3200 rpm, or 4700 rpm, just for examples. But effeciency does vary with rpm and load. I guess ours just doesn't vary that much over normal cruising rpms.
If the engine's effecincy didn't vary you'd get the same mileage at 60 if it was turning 1600 rpm, 3200 rpm, or 4700 rpm, just for examples. But effeciency does vary with rpm and load. I guess ours just doesn't vary that much over normal cruising rpms.
Thats basically what I was thinking. Makes me want to swap some 4.10's in and with 4th gear back, Id be around the same rpm so same mileage while also being able to be quite a bit quicker around town. Only downside is going above 75mph the engine rpm is kinda high (not saying the mpg's would change differently than with stock gearing), but I dont like to run the engine too high for too long....doesnt fee right. :fuse:
I know about that. A few years ago I had a 78 MGB w/ over 220K on it. In 4th (top gear) it would redline at 5k (I think) about 90 mph. I had to take 4.5 hour trips every few weekends and would cruise with the rpms between 4250 and 4750 the whole time. I kept waiting for a piston to fly through the hood! Never did though...
Yeah it was kinda annoying driving at 2500-3000rpm for 50 miles but i didnt notice any problems. Engine coolant stayed right around 195F. Assuming the engine coolant temp, and oil temp (which is somewhat dependent on coolant temp), stay within reasonable boundaries, I couldnt see anything wrong with running our jeeps at high rpms (well for our jeeps high....between 3k and 4k) assuming we keep everything at the right temps.
derrickdrew17
NAXJA Forum User
- Location
- Duncanville
im running a tad over 2200 doing 70mph.. but i dont see how everyone is driving 70 on up.. i get vibs doing anything faster than 70. i get really noticeable vibs at 30 because of drive line angle then it smooths out till 60-70 i think i get vibs from the mud tires. and im getting around 250 a tank when my fuel gage lights come on i usualy put in between 16.5 to 17.3 gallons.
