Thread: TD5 MAF Bypass

I posted some of this on Kelvin's orogonal thread, but thought I would post here for technical comment.

....Why not put the pipe in as shown in the previous post. Use 12mm (1/2in) pipe. Take it from the airbox to the crankcase breather hose inlet on the 90 degree connector thing that is there. Take the crank case breather hose and just whack on (for now) a 12mm crank case breather filter using a plastic hose joiner, or brass if you insist.

I run a provent, like this (and for those not familiar I also run a VNT):

Im thinking, Im going to disconnect the provent outlet hose from the provent, and connect that hose to the airbox. Then, on the provent outlet, Im going to stick one of these from DRIFT PERFORMANCE:

Total cost of experiment.....$14 for the filter (autobarn)
Probably $10 for brass fitings for the airbox.

Id be interested in TECHNICAL comments.

I too would be interested in peoples thoughts on this.
Hamish,I like your Provent work,I would get rid of that hoseclamp around the brake lines ASAP.The potential to chaffe thru the brake lines,despite the plastic sleeve is too great.
Andrew

Originally Posted by LandyAndy

I too would be interested in peoples thoughts on this.
Hamish,I like your Provent work,I would get rid of that hoseclamp around the brake lines ASAP.The potential to chaffe thru the brake lines,despite the plastic sleeve is too great.
Andrew

Already gone. Old photo

The MAF tells the ECU what the air demand is.
The ECU fuels according to the airflow and demand from throttle input.
Adding more air is not going to produce more power in a diesel unless you add more fuel to go with it. You possibly will lower EGT's by a miniscule amount, but you wont produce any more power.
Diesel is not an aromatic fuel like petroleum, its a fuel oil. Its burn characteristics are the reverse of petrol ie, a lean AFR for petrol burns hot and a rich mix burns cooler whereas a lean AFR in diesel burns cooler and a rich burn hotter.
As i siad previously, there is no throttle plate in a diesel, the engine has a full supply of air constantly, its solely the amount of diesel injected that that depends on how big the bang is.

Cheers

Andrew

Interesting topic. Has anyone else had a sneaking perception that after installing a snorkel the fuel economy drops??? Was chatting with local Engel repairer today and he reckons his F250 has gone from 15 lp100kms to 17lp100kms after fitting the snorkel. Have spoken to a couple of others with other 4x4s that are thinking similar. In no way want to get rid of the snorkel as it serves its purpose.
May look at cutting the pipe so it is a bit more open under the filter in the housing as it does seem a little restrictive.

Originally Posted by LOVEMYRANGIE

The MAF tells the ECU what the air demand is.
The ECU fuels according to the airflow and demand from throttle input.
Adding more air is not going to produce more power in a diesel unless you add more fuel to go with it. You possibly will lower EGT's by a miniscule amount, but you wont produce any more power.
Diesel is not an aromatic fuel like petroleum, its a fuel oil. Its burn characteristics are the reverse of petrol ie, a lean AFR for petrol burns hot and a rich mix burns cooler whereas a lean AFR in diesel burns cooler and a rich burn hotter.
As i siad previously, there is no throttle plate in a diesel, the engine has a full supply of air constantly, its solely the amount of diesel injected that that depends on how big the bang is.

Cheers

Andrew

Yup, but I think the theory of this approach is not necessarily more air. It is more air than the MAF thinks. Above, and in Kelvin's original thread which sparked this one, we seem to have a mix of different theory's. In my opinion, one is about allowing more air in, and the other about the MAF and letting air past it.

Theory/Solution 1. Allowing more air in is the domain of bigger airboxes, modding the airbox, hi-flow filters and whether or not the snorkel creates a choke point.

Theory/Solution 2. The MAF bypass, I believe is different.The theory is that with the VNT, the air demand is creating a value higher than what the MAF thinks is normal, in fact above its maximum range, and it thus registers an out of range, or fault signal, and that signal is upsetting the running of the car. By disconnecting the MAF, and letting the ECU use default values, performance actually improves. The theory is that by allowing air to go around the MAF, the MAF doesnt max out, or go out of range. Thus you have the same air, but a value that is higher than the "default value", but lower than the maxium value.
So, its not about MORE air, its about letting the engine use the air it wants and can already get.

For what it's worth, there have been many anecdotal stories, and somewhat subjective tests about snorkels and fuel efficiency. I think the most recent I saw was in 4wd Action. They took two cars (not LR), did a circuit before and after snorkel, and if I recall put them on a dyno. The snorkel was better, the difference in fuel economy was enough to mention, but not enough to rave about. Power difference was negligible, but slightly positive. If you approached it from a purely commonsense POV, you are getting cleaner air, it might well be slightly cooler, and as long as the aperture of the snorkel was similar to stock, airflow should not be much different. I could go into a lot of detail as it applies to high performance PETROL engines, but to be honest, I dont know how it applies to diesels. But, in essence:

Some strategies used in designing cold-air intakes for petrol engines are:

• Increasing the diameter of the air intake, reducing airflow velocity and pumping losses.
• Smoothing the interior of the intake to reduce air resistance.
• Providing a more direct route to the air intake by eliminating muffling devices.
• Shortening the length of the intake.
• Using a less restrictive air filter, usually trading filtering quality for increased airflow capacity.

I dont say this to take a particular point of view. You can only use the air you get. If your performance and economy has decreased because you have changed the airflow somehow, then you need a tune to reoptimise it

I have just purchased this from IRB developments.

IRB Developments - Diesel Tuning and More

The proper fix to your problem

THAT Concept has been spoken of a lot by all the usual suspects, but no one has done it until now....

Im going to buy one as soon as I stop typing this sentence.

I have another question though. According to RAVE, the MAF does, well, what is says below. If ALL it does is EGR, and I have removed EGR entirely....why do I still need it?

From RAVE:
The MAF sensor is located in the intake system between the air filter housing and the turbocharger. The ECM uses
the information generated by the MAF to control exhaust gas recirculation (EGR).
The MAF sensor works on the hot film principal. The MAF sensor has 2 sensing elements contained within a film. One
element is controlled at ambient temperature e.g. 25 °C (77 °F) while the other is heated to 200 °C (392 °F) above
this temperature e.g. 225 °C (437 °F). As air passes through the MAF sensor the hot film will be cooled. The current
required to keep the constant 200 °C (392 °F) difference provides a precise although non-linear signal of the air drawn
into the engine. The MAF sensor sends a voltage between 0 and 5 volts to the ECM proportional to the mass of the
incoming air. This calculation allows the ECM to set the EGR ratio for varying operating conditions.
Input/ Output
The MAF sensor receives battery voltage from the main relay in the engine compartment fuse box. Signal output from
the MAF sensor to the ECM is a variable voltage proportional to air drawn into the engine.
Input to the MAF sensor is via pin 5 of connector C0570 at the engine compartment fuse box. This 12 volt supply is
provided by the main relay via fuse 2 in the engine compartment fuse box. The MAF sensor receives the input voltage
at pin 3 of the sensor connector.
Output from the MAF sensor is measured at pin 11 of the ECM connector C0158. The earth path is via pin 20 of the
ECM connector C0158.

The MAF sensor can fail the following ways or supply incorrect signal:
l Sensor open circuit.
l Short circuit to vehicle supply.
l Short circuit to vehicle earth.
l Contaminated sensor element.
l Damaged sensor element.
l Damaged in wiring harness.
l MAF supplies incorrect signal (due to air leak or air inlet restriction).

In the event of a MAF sensor signal failure any of the following symptoms may be observed:
l During driving engine speed may dip, before recovering.
l Difficult starting.
l Engine stalls after starting.
l Delayed throttle response.
l EGR inoperative.
l Reduced engine performance.
l MAF signal out of parameters.

The MIL will not illuminate in a MAF sensor failure, and the ECM will use a fixed default value from its memory.