excesssive diesel consumption

[mud_slut]

hey all

was on the way back from echuca on the weekend and notice the L/100 was jumping up sitting around the 15 mark for 95-100 kph (will usually run around 8-9-10) and sitting just over 2k RPM. i did have a bit of camping gear on the roof so was happy to point the comsumption down to that, there were moments where consumption would drop to 9L/100 but then would shoot up to 14,15 again???

unloaded the camping gear and spare tyres last night and was doing the same on the way to work this morning (sitting very high around the 15 mark and then dropped back to 8 for a while). i have no idea what would cause it to sit so high? i did think the roof cradle at first would be the culprit however there were moments where the car would sit quite comfortably at 7 8 or 9L/100 while carrying all of the excessive weight.

any ideas on troubleshooting this one? or has anyone had this issue before? im thinking it could be anything from MAF to vaccume lines to a potentially locked on brake in the rear.

i don't currently have the boost gauge in (will be going back in tonight or tomorrow as it had to be sent off for repair (lights for no reason stopped working) but would be happy to give a boost reading when i put it back in. the turbo did sound like it was boosting quite hard to sit around the 95-100 mark

[layback40]

do you still have egr connected?

[Adrian D]

Aerodynamics play a big role at that speed, anything extra which creates turbulence will hurt fuel consumption, especially roof racks.

I did not notice any fuel consumption changes after I removed the EGR, only a bit less black smoke when accelerating very hard. But I don't drive for short distances (that's what the bike is for )

Boost would be pretty useful for figuring out when you eat more fuel, EGT gauge is even better for that

[mud_slut]

no the EGR is still connected however the PCV does not connect back into the turbo inlet and vents to atmosphere (has been since the bought the car).

i did change the fuel filter tonight and gave the MAF a clean. a friend said he had the same issue but on a different car and it turned out to be a faulty MAF.. drove it consistently up and down the road (@100kph) to try and replicate and it seemed sometimes is would want to sit around 9 and some times it would want to sit around 13,14,15

i might take the cradle off tomorrow night to see if that is the issue however i feel it might be something else, first and second seem fine but 3rd feels sluggish and 4 and 5th also seem to be the same. i noticed the water temp would rise from sitting around the 80 mark to mostly at 100 while on the fwy as well

i thought it might have been the brakes but the car seems to roll fine with the handbrake off and in neutral, unless they are locking on somehow while driving i don't think they are the problem

ill be picking up the boost gauge tomorrow and i might hook the egt i have sitting here to get a better idea.

at 100 KPH what boost/fuel/rpm do either of you sit on, i run my boost line from the intake manifold and run stock 237/75/15's. Boost might be a bit different i think layback runs his from the vac line for the turbo i think

[Adrian D]

Pretty weird that it's an intermittent issue.

On flat ground, at 100 km/h I'm right around 1900 rpm and under 8 psi (manifold pressure but I have sold the boost gauge a while ago and my memory of boost is unclear). Can't comment on fuel consumption as I don't have the trip computer but I average anywhere between 8 and 9 L/100 km. 235/75R15 bone-stock suspension.

Collapsed or crushed exhaust? EGT would pinpoint that if you have baseline values. Are the brakes hot after a long drive?

This reminds me of troubleshooting a 50cc 2-stroke, it would run well, hit a pot-hole run bad for a while then good again. Turned out it had tons of carbon in the exhaust.

[layback40]

I mentioned the egr because if it is opening it will increase fuel consumption. they have a bad habit of jamming both open & shut. i would pull the vac line off it, & plug the vac line & see if it still does it. In the long run you are best putting a blank plate under it or remove it all together so it doesnt leak.

[Adrian D]

Perfectly valid point on it jamming open, it could explain why the issue is the intermittent