z4 35i fuel consumption

[Busterboo]

As I've posted elsewhere, I use my 35is for fun and plenty of it. So, I've done 16,000 non-commuting miles in the last year. These have included quite a lot of short-burst, high-speed/fast-acceleration driving, but little long-distance.

The 35is's fuel consumption has, however, remained remarkably consistent. Push it as hard as I like, and I do, it still does about 295 on a tank of 95RON: 25.4mpg.

So, the OP's figures suggest he's losing quite a lot of something somewhere and removing carbon deposits ain't going to make enough difference.

[Lazza]

Could it be a seized brake caliper?

[R.E92]

Snake oil ain't going to give you a 20% 'correction' of your fuel consumption.

Take it to a good indy or BMW.

No snake oil involved with walnut blasting. You may be confusing it with other carbon cleaning procedures like seafoam.

Walnut blasting involves ... physically blasting the carbon deposits away. Fairly well established method of removing carbon deposits in direct injection engines.

I understand how it works, but doubt that it will work in the way the OP wants.

Then you mis-used the term "snake oil".

Coked intake ports cause loss of power and misfires. Increased fuel consumption is also noticed.

[R.E92]

Poor fuel consumption could be bad injectors or lambda sensors.

How old is your car and has it ever had injectors changed?

Snake oil ain't going to give you a 20% 'correction' of your fuel consumption.

Take it to a good indy or BMW.

No snake oil involved with walnut blasting. You may be confusing it with other carbon cleaning procedures like seafoam.

Walnut blasting involves removing the valve cover and physically blasting the carbon deposits away. Fairly well established method of removing carbon deposits in direct injection engines.

Don’t you mean removing the inlet manifold rather than the valve cover?
Rob

Yes, my mistake.

[Busterboo]

Then you mis-used the term "snake oil".

Yes, you're right. I did.

I meant 'a solution that is not the product of examination of the car and informed diagnosis of the problem'.

[sachak]

lol I live in South Africa, I definitely don't have it set to miles, I would have a serious amount of speeding fines if that was the case.

With regards to injectors, I checked last night and they are definitely Revision 12 injectors...all of them. and as far as I recall I think they were replaced less than 10k km ago.

I have no miss fires
I had a bad 02 (Lambda sensor) a while back but I replaced that last year September with a brand new one and both are reading correct AFR values that being 14.7 while car is idling and making there way to +-12.5 under boost. I ran some logs yesterday to be sure of that.
Also on that note, before changing that bad o2 sensor, I used to get o2 sensor errors all the time on MHD and Carly which I no longer get since changing it out.

I can't see it as being bad coils or spark plugs at this time due to the car not having a missfire or rough idle.

What I do know is that when I did the oil filter housing gasket and I had to pull the intake manifold back I had a good look at my intake ports and the carbon build up was VERY VERY bad. However when the carbon build up is bad to the point of causing bad fuel consumption wouldn't it also cause a rough idle?

My brake calipers are perfect....I changed all 4 pads recently and replaced sensors and lubed those calipers up very well, they are functioning perfectly.

[R.E92]

lol I live in South Africa, I definitely don't have it set to miles, I would have a serious amount of speeding fines if that was the case.

With regards to injectors, I checked last night and they are definitely Revision 12 injectors...all of them. and as far as I recall I think they were replaced less than 10k km ago.

I have no miss fires
I had a bad 02 (Lambda sensor) a while back but I replaced that last year September with a brand new one and both are reading correct AFR values that being 14.7 while car is idling and making there way to +-12.5 under boost. I ran some logs yesterday to be sure of that.
Also on that note, before changing that bad o2 sensor, I used to get o2 sensor errors all the time on MHD and Carly which I no longer get since changing it out.

I can't see it as being bad coils or spark plugs at this time due to the car not having a missfire or rough idle.

What I do know is that when I did the oil filter housing gasket and I had to pull the intake manifold back I had a good look at my intake ports and the carbon build up was VERY VERY bad. However when the carbon build up is bad to the point of causing bad fuel consumption wouldn't it also cause a rough idle?

My brake calipers are perfect....I changed all 4 pads recently and replaced sensors and lubed those calipers up very well, they are functioning perfectly.

I'd get the carbon buildup sorted. Only cost me £300 in the UK. I wouldn't expect an extra 200km per tank but it will help performance.

What do your fuel trims look like in the logs? both long term and short term.

[sachak]

So the car is at the carbon doctor as we speak getting the carbon clean walnut blasting done, they are also going to run a bunch of diagnosis on the car and see if they can pick anything else up that might relate to the high fuel consumption.

Will show before and after pics of the carbon clean when I get them and let you guys know the outcome.

[willgill]

[sachak]

So got the car back yesterday afternoon after the carbon doctor and she definitely idles smoother and seems to be smoother and more responsive in general.

I will let the pics do the talking.

These are pics sent to me from the carbon doctor:



Before:








And then After:

[Smartbear]

certainly cleaned it up well think i'd get a catchcan plumbed in to stop that gloop making a reappearance
Rob

[sachak]

I have a catch can sitting in my garage that BMW decided to cut the pipes up or loose them.

However I have done allot of research and spoke to The Carbon doctor who told me he has done tests with the catch cans over extended time and found that it made little to no difference in the build up at all. After 40k km the build up was the same.

[1000rr]

Would a carbon clean be the same as terraclean?

[Kugaman1]

Nope, not at all.

Terraclean is definitely a cousin of snake oil! It cleans injectors but little more. It only works on manifold injection engines, not direct injection engines. Theres nothing that can clean direct injection engimes without some form of dissassembly.

Walnut blasting is a proven method thats really effective, just look at the pics!

[Gaffa22]

Terraclean, Ed China's snake oil