V6 fuel mileage

[_-Night-Shade-_]

whats everyones city mileage? ive been babying my last 2 tanks and they had the worst mileage ive gotten since i started keeping track. both were however the only tanks ive used completely in the city. first tank was 12.13L/100km and the one i just filled up with was 12.42l/100km. all my other tanks were city/highway blend and i averaged about 10l/100km of spirited driving.

for city driving ive been shifting between 2.5k-3krpm.

Jesus man my 4x4 truck gets 12L/100km, something's definitely not right there. Even when my KL-ZE was running on 5 cylinders and sounded like a Subaru due to bad plug wires the worst I got was 11L/100km.

[mikeinaus]

yeah thats what im thinking. its running good thow, tuns of power, doesnt stutter or throw any cels. i honestly have no idea what to look at anymore.

i just swapped in some new plugs and order some new wires. hopefully that has some effect. the car does seem to idle a bit smoother with the new plugs.

[MrMazda92]

Could it be running WAAAAY Rich? :/

[mikeinaus]

not terribly. it does run a bit rich but nothing like when i had a bad o2...

[MrMazda92]

I don't know what to tell you... your luck must be terrible. :/

[mikeinaus]

i just installed my new wires and filled up so i can gauge the effect of my new plugs/wires on a full tank. my last tank which had new plugs for half of it, shifting at 2krpm or less 98% of the time i managed 75k on 10.8L or 14.59L/100km . im starting to think my car enjoys being bagged on, the lower i shift and slower i drive the more gas ive used. im going to give it one more tank of babying then start driving the crap out of it and see whats up.

ill post some pics of my plugs after the next fill up and you guys can tell me if its running horribly rich.

any chance a leaky valve cover gasket could cause bad mileage?

[MrMazda92]

You'll see good signs of it running rich on your exhaust tips as well; if you clean them up and they darken fairly quickly, with carbon deposits forming, that's one of many signs that you're running rich. Beyond that, wideband O2 ;D

As far as RPMs go, I noticed mileage was better on my '93 when I shifted around 3k. KL(3k), and my K8 '92 mileage is roughly 2,200-2,500 shift points.

[mikeinaus]

You'll see good signs of it running rich on your exhaust tips as well; if you clean them up and they darken fairly quickly, with carbon deposits forming, that's one of many signs that you're running rich. Beyond that, wideband O2 ;D

As far as RPMs go, I noticed mileage was better on my '93 when I shifted around 3k. KL(3k), and my K8 '92 mileage is roughly 2,200-2,500 shift points.

well i did have some black water sitting in my exhaust tips today. i just dont get why its running so rich. as far as i can tell i dont have any exhaust leaks, disty cap/rotor are new, o2s are good, and its not burning much oil. ive put on 6000km since my last oil change and im still more then 1/2 full on the dipstick without adding any. i also have oil pool on top of my front valve cover so ive probably burned less then .4L (assuming Low to full is 1L on dipstick) maybe my probinator chip has a bad tune on it or something. perhaps i should try a mx6 ecu/airflow sensor. would that have any negative effects other then improper vris points?

id hate to have to spend that much extra on some wide band o2's. not knowing much about them i just googled what they are. aparently they are basically more accurate o2's that tell you how bad the fuel mixture is rich or lean (where normal o2s simply state its rich or lean). now would the ecu be able to use this information different from regular o2's? shouldn't i be getting an o2 code if they are bad?

is there anyway to get information from the ecu regarding fuel mixture similar to an obd2 system? if i can find a obd1 reader do they only read codes or is there any real time information to be displayed?

[MrMazda92]

well i did have some black water sitting in my exhaust tips today. i just dont get why its running so rich. as far as i can tell i dont have any exhaust leaks, disty cap/rotor are new, o2s are good, and its not burning much oil. ive put on 6000km since my last oil change and im still more then 1/2 full on the dipstick without adding any. i also have oil pool on top of my front valve cover so ive probably burned less then .4L (assuming Low to full is 1L on dipstick) maybe my probinator chip has a bad tune on it or something. perhaps i should try a mx6 ecu/airflow sensor. would that have any negative effects other then improper vris points?

id hate to have to spend that much extra on some wide band o2's. not knowing much about them i just googled what they are. aparently they are basically more accurate o2's that tell you how bad the fuel mixture is rich or lean (where normal o2s simply state its rich or lean). now would the ecu be able to use this information different from regular o2's? shouldn't i be getting an o2 code if they are bad?

is there anyway to get information from the ecu regarding fuel mixture similar to an obd2 system? if i can find a obd1 reader do they only read codes or is there any real time information to be displayed?

If your O2s are new, and aren't giving any sign of trouble, running rich might not be your problem. :/

I'd try the ECU/VAF swap, since it's pretty simple and would be a straight forward test. Beyond that... Well it's beyond me :/

[_-Night-Shade-_]

shifting at 2krpm or less 98% of the time

Way too low, you're bogging down the engine which will in turn cause it to do more work. This isn't a V8. 2.5-3 is fine for regular driving, higher if you need quick acceleration. Why do you think the RPMs are around 4k at highway speeds? (close to peak torque range). If you really want to see where the engine does the least work, install a vacuum/boost gauge. Keeping it in the range of most vacuum will yield best fuel economy (you're on the throttle less). You know how some luxury cars such as BMWs have fuel consumption gauges/meters? They're just vacuum gauges.

[marcdh]

x2 The vac gauge is a cheap way of getting a rough idea. It doesn't compensate for different parts of the map being richer etc but it's a good start. Like if you are going up a slope in 5th at <2k rpm it requires much more open throttle than 3rd at 4k with very little throttle. I try to stick to the bottom of the powerband for economy. I used to shift to 5th in 30 zones, but seeing the fuel load in megasquirt soon changed that habit. I'm in 3rd gear for 30mph and my mpg is better for it. It's probably been said, but consider your alignment, make sure brakes aren't sticking, tyres have good pressure etc. Though as I've said before probinator is a rich map, though responsive. Megasquirt netted me >3mpg with noob tuning abilities and more power.

[Nd4SpdSe]

shifting at 2krpm or less 98% of the time

Way too low, you're bogging down the engine which will in turn cause it to do more work. This isn't a V8. 2.5-3 is fine for regular driving, higher if you need quick acceleration. Why do you think the RPMs are around 4k at highway speeds? (close to peak torque range). If you really want to see where the engine does the least work, install a vacuum/boost gauge. Keeping it in the range of most vacuum will yield best fuel economy (you're on the throttle less). You know how some luxury cars such as BMWs have fuel consumption gauges/meters? They're just vacuum gauges.

Exactly! People are too obsessed with keeping revs low thinking it's for better fuel economy, but it's all about on how hard the motor is working

[mikeinaus]

shifting higher makes sense according to how my fuel logs have been going. im planning on getting a vacuum gauge im just trying to figure out which one i want. are cheap ones worth getting or should i spend some money on a decent one? i was thinking about this one but shipping is $50 to canada http://www.ebay.ca/itm/2-INCHES-RACING- ... 503wt_1398 i also havnt been able to find them anywhere locally. this one is a cheaper option http://www.ebay.ca/itm/UNIVERSAL-2-TINT ... 099wt_1253 i want a 2" gauge to fit in the 94+ vents correct?

ive always wondered if it was better to be in a higher gear with less rpm and more throttle up a hill vs a smaller gear with less throttle and higher rpm.

i installed my new plug wires yesterday. i was having a weird vacuum leak problem after with the idle rolling between 1000-15000rpm constantly but it seems to have fixed itself.

alignment was done a few months ago, as were brakes. as far as i can tell they are not dragging. i can push the car by hand fairly easily and it rolls very well when not in gear.

[Nd4SpdSe]

ive always wondered if it was better to be in a higher gear with less rpm and more throttle up a hill vs a smaller gear with less throttle and higher rpm.

I have video exactly that with my boost gauge in the X. Lower gear I could go up the hill at about 10inMg, in 5th, I was full boost

[MrMazda92]

I've found dropping the revs to 2k at the end of a shift(shifting at 2.4 ish) doesn't bog the engine down at all, for that matter I ran my idle at 2K before I unplugged my cursed IAC, cruising in 5th was fine (40 ish in a 35 around town).

Honestly though, 1-3 tolerate it better than 4th and 5th. I would not shift into 5th before 40 though, and I don't mean 39 As for economy, I get piss mileage on the freeway at 3.5-4k.