air flow question for a diesel mechanic

s.w.blackwell · Post by **s.w.blackwell** » Fri Jan 04, 2008 8:27 pm

Hi all

I am trying to come up with a method of measuring the economy of the bongo while i drive, all my old cars had them and the bongo is missing one.

My question is " is air intake mass flow proportional to diesel use?" or "does turbo compression alter proportions?"

why you ask?

Well most cars have a mass air flow meter and they are cheap as chips on flebay.

could i use one as a economy measure?

ive thought about diesel flow meters, MAF sensing, cant even count injector pulses because the bongo is mechanical. No OBD either.

cheers

scanner · Post by **scanner** » Fri Jan 04, 2008 9:37 pm

No, not that I know of, a diesel just draws in unrestricted air and squirts in just enough fuel to go as fast as requested by the accelerator. They do not need a fixed ratio of air to fuel like wot a petrol does.

It is one of the reasons they are so much more efficient.

BongoMTBer · Post by **BongoMTBer** » Fri Jan 04, 2008 10:11 pm

Yes, I agree with the above. The mass flow is proportional to engine speed. The fuel is scheduled according to the power and engine speed selected.

If you could find a way of measuring fuel flow vs. road-speed that would do it.

However, if you had a vintage McCormick tractor, they had a butterfly conrtoled induction and scheduled the fuel according to mass flow...... but you haven't so I'll get my coat.

s.w.blackwell · Post by **s.w.blackwell** » Sat Jan 05, 2008 12:54 am

Thanks

nothing simple.

looks like a flow meter in the diesel line, is there a return line too?

Looking at the diesel filter pipes i assume at that point it is low pressure so it may be measurable.

cheers

ste

Captainsideways · Post by **Captainsideways** » Sat Jan 05, 2008 1:58 am

Theres a better solution - get a wideband Lambda sensor measures oxygen in the exhaust & converts the signal directly to AFR or Air Fuel Ratio. Wideband works over wider range than regular lamda probes

I run one on my drift car, its comes with data logging facilities, used for mapping my engine (thats 540bhp) but easy to plug into anything with a lambda probe hole (£10 welded to exhaust downpipe)

I can highly recomend the VEMS system/unit I have cost is about £180

In fact shortly I will be doing some bongo datalogging to see just how much they are chucking in!

bigdaddycain · Post by **bigdaddycain** » Sat Jan 05, 2008 2:16 am

Nice one cap'n...Keep us posted?

s.w.blackwell · Post by **s.w.blackwell** » Sat Jan 05, 2008 7:55 pm

get a wideband Lambda sensor

Can you tell me where you got your vems system from? would they sell a sensor on its own?

I plan to fit my own lcd datalogger to the dash and monitor other things, easy to read temps, revs, speed, battery voltage etc just finding it hard to measure fuel use.

ste

Captainsideways · Post by **Captainsideways** » Sun Jan 06, 2008 12:59 am

s.w.blackwell wrote:
get a wideband Lambda sensor
Can you tell me where you got your vems system from? would they sell a sensor on its own?

I plan to fit my own lcd datalogger to the dash and monitor other things, easy to read temps, revs, speed, battery voltage etc just finding it hard to measure fuel use.

ste

Contact rob at vems dot co do uk

or click on vems.co.uk & head to the forum, loads of info on there.