still burning too much gas...

[Nd4SpdSe]

think its possible my car is running ideal and its just the; 200ish lbs ive added with my stereo and rx8 seats, short city driving, 2.5" exhaust/intake and larger rims?

I had a 12" sub with a 750w amp, a huge CarPC with a 1200w inverter and a 17" lcd, leathers, and ran 17" Konig rims (with a matching spare in the trunk) and a 2.5" exhaust

[davmac]

think its possible my car is running ideal and its just the; 200ish lbs ive added with my stereo and rx8 seats, short city driving, 2.5" exhaust/intake and larger rims?

short city driving and larger rims are a drag on your fuel economy - you gotta figure all the idling is 0 mpg or infinity liters / 100km
No version of a ZE (or DE or K8) could be considered a fuel miser.

Sorry no perfect car - just perfectly satisfying cars in the eyes of the owner. Sounds like yours is not making the grade in that sense. You own one of the finer looking examples of an MX3 but you're pretty frustrated with it. If you want a fuel miser there are plenty around. If the MX3 can't deliver 30+ mpg or less than 8 liters / 100km would you be happier with another car that could?





Sorry to get all philosophical, but I don't think there is a mechanical issue here.

[wytbishop]

Mike have you actually confirmed a rich A/F ratio? Is there some diagnostic equipment at your disposal that can tell you that with any accuracy? Can a basic emmisions test be related to A/F ratio?

In general, if I'm not mistaken, an injector uupgrade is required to add more than about 8-9psi of boost. You're getting a little better than half the mileage that I'm getting on my ZE, which means that your ECU is injecting almost 50% more fuel than mine is. If your AFRs were correct you'd be making a lot more power by burning that much more air/fuel mixture, so it must be going through the engine unburned...right? So how does an extra bunch of fuel go through the engine without being burned? Answer that question and you'll be getting somewhere.

I agree with Mike (Nd4Spd) that big wheels, big stereo, leather seats doesn't account for what your experiencing. I also agree with Ryan that our expectations get the better of us. It's probably pretty close to any of ours.

[crazycanadian]

Mike have you actually confirmed a rich A/F ratio? Is there some diagnostic equipment at your disposal that can tell you that with any accuracy? Can a basic emmisions test be related to A/F ratio?

In general, if I'm not mistaken, an injector uupgrade is required to add more than about 8-9psi of boost. You're getting a little better than half the mileage that I'm getting on my ZE, which means that your ECU is injecting almost 50% more fuel than mine is. If your AFRs were correct you'd be making a lot more power by burning that much more air/fuel mixture, so it must be going through the engine unburned...right? So how does an extra bunch of fuel go through the engine without being burned? Answer that question and you'll be getting somewhere.

I agree with Mike (Nd4Spd) that big wheels, big stereo, leather seats doesn't account for what your experiencing. I also agree with Ryan that our expectations get the better of us. It's probably pretty close to any of ours.

He has labscopes and gas analyzers at his school.. Unfortunately the gas analyzer you can't use while driving, and he hasn't been able to use the labscope while drive the car either... Driving is when he needs to be doing all of his testing... A wide band O2 sensor would go along way to help though... The biggest thing mike needs to do is determine if the computer is keeping good fuel control while driving.... If it is, then the only way he's going to get better millage is to try tuning it... If its not then we have to figure out why...

[mikeinaus]

It's not that I'm expecting 8l/100km. Id just like to not have to put in 45l of fuel when I've gone 300km. I know the idling doesn't help but if you saw the readings my mpg comp is putting out while driving you would get the idea. Maybe ill take a video of just that for you guys today. I honestly believe the amount of fuel I'm using during accelleration and cruise is the biggest problem.

At this point, in my current financial situation it would make sense to sell the mx and get a more efficient car. The problem is Id probably get $2500 max for my car and I've spent probably over $6000 in the past year and I'm unwilling to looose that much at this point in time. It would make more sense to part it out but I'm unwilling to do that cuz its in such good shape. Thus I'm stuck trying to figure this out as cheap as possible.

[wytbishop]

No there is definitely an issue there somewhere. It's not just one of those things we live with.

Don't give up man. It will haunt you forever.

Have you tested the ignition system? It seems to me if the spark was really poor and you were missing enough on acceleration and cruising that your mileage would suffer pretty badly, but wouldn't be obvious troubleshooting wise.

[mikeinaus]

but thats the thing there is no obivious misfiring or anything. i did have some misfiring a while back after the car sat hotsoaking for 20min or so but that has fixed itself. i think something was going on with one of the injectors and it just worked itself out. i think it would be alot easier to fix the problem if there were some kind of major symptom like that, it would atleast give me something to go on, or hint at a specific area of the vehicle. at first i was testing as much as i could to try and find the problem, then i got frustrated and just started replacing everything that could have an effect. now im at the point where ive literally replaced everything except the engine itself and im still having problems.

[Nd4SpdSe]

big wheels [..] doesn't account for what your experiencing.

Depends, Trevor had some HEAVY rims on his car (blew an axle at the track, we blame them for that) but for the amount his car is consuming, i want to say even than's pushing it unless they're like lead rims, lol

[wytbishop]

Well I look at it like this. I am running full leather interior, chipped K8 ECU, JE50, 2.25" exhaust, no CAT, single 16" resonator, dual tip Magnaflow muffler and 17's that aren't particularly light on a stock straight neck ZE. So Mike's situation and mine are not so dissimilar. A few differences, but nothing crazy.

I normally get about 8.8-9.4L/100km in the city and like...7-8L/100km if I to Calgary and back lets say...about a 6 hour round trip. It's a bit over 600km and I use about 44L to do it. I can easily do it on a single tank. Based on what he's saying Mike would get maybe 350km out of a tank on the highway??? A slightly rich condition or heavy rims and a big exhaust don't account for that.

Here's what I'd do. Find someone local with a ZE or K8 that's getting good mileage and doesn't mind helping you out. Fill the tank just till the nozzle clicks. Zero your odometer. Create a route of about 50km and measure the distance as close as you can in your car as it is. Refill the tank exactly the same way. If you're using about 15L/100km you should need between 7 and 8L to refill.

Start switching their sensors onto your engine. Start with their ECU and VAF. Drive your route and refill the tank. See if there's a difference. I would only need 5L after 50km so even a 1/4 liter improvement is significant. Put their O2 sensors on and try that. Put their Distributor on and try that. Put their Throttle Body on and try that. Put their thermosensors on and try that.

At some point you'll see a significant change. It's worth a try. Invest a day on that.

[mikeinaus]

Well I look at it like this. I am running full leather interior, chipped K8 ECU, JE50, 2.25" exhaust, no CAT, single 16" resonator, dual tip Magnaflow muffler and 17's that aren't particularly light on a stock straight neck ZE. So Mike's situation and mine are not so dissimilar. A few differences, but nothing crazy.

I normally get about 8.8-9.4L/100km in the city and like...7-8L/100km if I to Calgary and back lets say...about a 6 hour round trip. It's a bit over 600km and I use about 44L to do it. I can easily do it on a single tank. Based on what he's saying Mike would get maybe 350km out of a tank on the highway??? A slightly rich condition or heavy rims and a big exhaust don't account for that.

Here's what I'd do. Find someone local with a ZE or K8 that's getting good mileage and doesn't mind helping you out. Fill the tank just till the nozzle clicks. Zero your odometer. Create a route of about 50km and measure the distance as close as you can in your car as it is. Refill the tank exactly the same way. If you're using about 15L/100km you should need between 7 and 8L to refill.

Start switching their sensors onto your engine. Start with their ECU and VAF. Drive your route and refill the tank. See if there's a difference. I would only need 5L after 50km so even a 1/4 liter improvement is significant. Put their O2 sensors on and try that. Put their Distributor on and try that. Put their Throttle Body on and try that. Put their thermosensors on and try that.

At some point you'll see a significant change. It's worth a try. Invest a day on that.

my rims arnt even that heavy, they are like 18 or 19lbs each. the thing with swapping individual parts until i find what works is i have spares of almost everything as i have a parts car. everything has been swapped and tried. back on page 7 i listed everything i have checked and replaced with little improvement. other then swapping the intake im unsure of what else i should even try swapping. fyi the farthest i have made it on a tank of gas was 409km back last august. i recent had a tank where i made it 390km but that was probably 60% on the highway babying the car to try and get the best mileage possible.

tire pressure 45 all the way around, 17" 205-40-17 tires on 18lbs rims
spark plugs wires and disty rotor/cap were all replaced 6 months ago
2 distributors tried no effect
two alternators tried
O2 sensors: checked and replaced
air filter: cleaned and in good condition
all belts/pullies and bearings have been replaced so theres no drag in the belt system
injectors have been replaced
tried 2 aftermarket klze chips for my 94 k8 ecu with no difference, also tried ecu from a 94 mx6 as well as airflow sensor with no improvement
3 different vafs have been tried
2.5" high flow exhaust thats like a year old without any clogs or leaks.
all 4 calipers were taken apart cleaned and greased so there is no drag from them or the e brake cable (even pad wear all the way around)
only cel code refers to egr
fuel pressure/regulator were checked and found in good condition
pcv is new
both coolant temp sensors were replaced and tested in spec
timing is set to 11 degrees
no smoke from exhaust in the light of day
exhaust feels quite humid when i put my hand infront of it and it never gets extremely hot. i can put my hand on my exhaust tip after an hour drive and not get burned...
compression is around 205 on all cylinders
engine is extremely clean under the valve covers and has always been properly maintained.

im starting to think its something internally wrong with the engine or possibly transmission. everything electronic involved that i can think of has been swapped. anyone have any ideas of internal problems that could cause this? my compression was a bit low when i did the test 190-195 each cylinder if i remember right. i could try a leakdown test but i think my valves are seating properly from the compression numbers so im doubtful im getting a bad burn with an ideal mixture. anyone know of any internal drag problems that could exist with the transmission and not be obvious? maybe i have a bad bearing somewhere thats causing excessive drag in the powertrain?

[wytbishop]

try another tranny...it only takes a few hours and they're everywhere.

[Ryan]

From my experience, a problem like this is usually something little that you overlooked as you dove into the complicated s---. I did it with my black car, I see many other threads with it

Go back to basics.

Grounds
Intake leaks


Don't just say its good, check half-a--, literally go and do it.

[mikeinaus]

i was thinking of upgrading the grounds. however theres no intake leaks. all the vacuum lines have been replaced as well as all gaskets related to the intake. car has a strong smooth idle.

[wytbishop]

What about the fuel delivery system? Have you verified the fuel pressure? Maybe everything electronic is fine and the injectors are dumping too much fuel because the pressure is too high.

[mikeinaus]

fuel pressure is in spec and the regulator is functioning properly, i havnt done a volume test but i didnt think that would be relevant to a engine running rich...