Thread: How to completely get rid of MAF on de-EGR'd TD5

what can i say ...i've graduated avionics engineering and used my theoretical knowledge corroborated with all the official data from RAVE and various tests made on a self built bench from old D2 harnesses and that's what i found... i thought i'll share that with everybody but not before i used my own car as guinee pig...what i couldn't test is if it would affect more an auto cos i dont have an auto ECU for tests but i have a friend with auto who made the mod and he is pleased as well

as a matter of fact i know that for different kind of diesel management the MAF is important but on those if you unplug it they will run bad or even cut out not run better like the Td5 does when the MAF is gone

Originally Posted by lpower85

Rave states this information is derived from MAP sensor readings.

Nope. Map sensor reads pressure, not airflow.

Originally Posted by sierrafery

what can i say ...i've graduated avionics engineering and used my theoretical knowledge corroborated with all the official data from RAVE and various tests made on a self built bench from old D2 harnesses and that's what i found... i thought i'll share that with everybody but not before i used my own car as guinee pig...what i couldn't test is if it would affect more an auto cos i dont have an auto ECU for tests but i have a friend with auto who made the mod and he is pleased as well

as a matter of fact i know that for different kind of diesel management the MAF is important but on those if you unplug it they will run bad or even cut out not run better like the Td5 does when the MAF is gone

If you unplug the maf it relies on a base table for limp home values. Normally reducing performance.

Your bench tests cannot even account for varying turbo and intercooler efficiency.
Which a maf does automatically.

i must disagree though...no offence, my apologies as a newbie but i must sustain my case:

i would hardly name "limp mode" the way a de-EGR'd Td5 runs with an unplugged MAF though ... the turbo and intercooler efficiency is measured by the MAP/IAT sensor on a Td5, what i have tested was exclusively the management's behaviour while giving voltage inputs for all sensors emulating a running engine with a multiple port signal generator to a connected ECM and measuring with an oscilloscope on the wastegate modulator and injector management outputs... cos that's what the management does on a Td5, it's whole addaptive strategy is based on all the other sensors except MAF... that's the odd Td5

Originally Posted by RAVE - Engine managment Td5

Engine management
The ECM controls the operation of the engine using stored information within its memory. This guarantees optimum
performance from the engine in terms of torque delivery, fuel consumption and exhaust emissions in all operating
conditions, while still giving optimum driveability.
The ECM will receive information from its sensors under all operating conditions, especially during:
l Cold starting.
l Hot starting.
l Idle.
l Wide open throttle.
l Acceleration.
l Adaptive strategy.
l Backup strategy for sensor failures.

The ECM receives information from various sensors to determine the current operating state of the engine. The ECM
then refers this information to stored values in its memory and makes any necessary changes to optimise air/fuel
mixture and fuel injection timing. The ECM controls the air/fuel mixture and fuel injection timing via the Electronic Unit
Injectors (EUI), by the length of time the EUI's are to inject fuel into the cylinder. This is a rolling process and is called
adaptive strategy. By using this adaptive strategy the ECM is able to control the engine to give optimum driveability
under all operating conditions.

During cold start conditions the ECM uses ECT information to allow more fuel to be injected into the cylinders, this
combined with the glow plug timing strategy supplied by the ECM facilitates good cold starting.

During hot start conditions the ECM uses ECT and FT information to implement the optimum fuelling strategy to
facilitate good hot starting.

During idle and wide open throttle conditions the ECM uses mapped information within its memory to respond to input
information from the throttle pedal position sensor to implement the optimum fuelling strategy to facilitate idle and wide
open throttle.

To achieve an adaptive strategy for acceleration the ECM uses input information from the CKP sensor, TP sensor,
ECT sensor, MAP/ IAT sensor, and the FT sensor. This is compared to mapped information within its memory to
implement the optimum fuelling strategy to facilitate acceleration.

all my theory is based on official data but my tests confirmed that also

Originally Posted by Dougal

Nope. Map sensor reads pressure, not airflow.

While this is correct, you need only pressure or airflow not both.
Either can be used to calculate the mass of air entering each cylinder and hence the required amount of fuel.

Any chance of a tutorial?

I am certainly willing to give it a shot if its reversible....

Cheers

This is a great topic. Love the debate and attention to detail. Thanks for starting this topic.

So if the MAF essentially does nothing other than control the EGR, why does it impact performance when it is not working correctly when the EGR has been removed? What is the ECU doing with this info when it is not working correctly, that it does not do when it does work correctly?

Sierraferry,

Well I'm not going to dismiss this outright and I admire your resolve standing your ground on this - obviously you've done your home work but I have a few questions, not trying to be obtuse but I think that they are valid.

Originally Posted by sierrafery

IMPORTANT with that mod is to not forget to replace the air filter regularly...that's all

Ok common sense says so, but why if the MAF has no input to fuelling is this more important with this mod done?

Also, I was of the understanding that if a MAF returned a reading over ~640 kg/hr then fuelling was cut to the engine, resulting in a characteristic drop in power (this can be seen on a nanocom log). Is this not the case? and if not to what can can the drop in power be attributed to if the MAF has no bearing on fueling? Or is (I'm just theorising here) the MAF reading used against the mapped information in such 'wide open throttle' conditions.

There has been a bit written on solutions to stop this characteristic drop in power attributed to a maxed out MAF when increasing boost on a TD5. solutions have included uprated MAF (i.e a MAF that returns lower readings), bypass hoses to fool the MAF, boost boxes (whatever hey do). If what you say is the case then none of these should work as the MAF has no input to fuel allocation yet none (well may be he boost box) of these would have any affect on the manifold pressure. I'd just appreciate your thoughts on this - plenty of people seem to have (and still do) made money selling such products.

Which type of TD5 are you emulating and do you drive, EU2 or EU3 type?

Have you monitored fuel consumption prior and post this modification on your truck? Was there any difference?

Thanks in advance for your response and thanks for posting - welcome to the forum.

Cheers.

Ian.