I measured the stock MAF opening and it’s 2.75”, so a big reduction from the 4” throttle body. Use the formula Area=Pi X radius(squared), where Pi is 3.14. For a 4” intake the area is 12.56 square inches. For the stock MAF the area is 5.94 square inches……or slightly more than one half the area of the 4 inch intake. So it’s no wonder the stock MAF robs power. Gotta love 7th grade math.
I thought about mounting just the sensor in my 4” intake too, but after conversation with Captain Aaron I’m not sure that’s a good idea. If the sensor is in a larger tube it may detect reduced air and air velocity, which may result in a faulty reading. The Captain pointed out that a “bad reading” may be worse than no reading at all. If you consider a MAF that is dirty may give a reduced reading of air volume, and that lower MAF reading may result in less transmission line pressure, you might conclude that that is bad for the transmission. The reduced line pressure may result in slippage in the trans, and possible trans failure. I’m guessing here, because I’m no expert.

The transmission shifts without the input of the stock MAF when the MAF is unplugged. I’m not sure how the transmission does that. My guess is the the transmission receives input from other sensors, including the TPS (Throttle position sensor), and shifts in some kind of default mode. With my Foxwell NT530, I can see live data, and throttle position is one parameter in can see change when I mash the gas pedal. Does the Rover PCM also receive input from the GM MAP sensor (Manifold absolute pressure), crank position sensor, and camshaft position sensor through the connection via the ACE ECM (the magic little black box that comes in the ACE kit)? I don’t know…..maybe someone on the forum can enlighten me.
So what is worse…..a bad MAF reading or NO reading at all. I know eliminating the MAF altogether means noticeably more power, but am I going to ruin a transmission?
Too bad the Compushift trans controller is unavailable…..otherwise I would buy one and be done with it.

 

Not sure but im willing to be the guinea pig. Mine has the btr truck norris cam in it and I'm not so easy on it all the time either.

 

Mr. Boostle I’ll be joining you as a Guinea pig. It looks like we have virtually identical engines, and my Disco was not built to be pampered.
I will run with no MAF until I blow up my transmission, or I become better educated on more acceptable solution.
I wish us good luck.

 

Well I’m gonna continue to assemble with no rover MAF and see how she goes.

 

I have over 30,000 miles on my swap now with the MAF and truck runs great.

 

Just wanted to add some of my thoughts / conjecture to this a bit. From what I understand, the MAF is used as the best method for calculating torque, which is used for a number of things, including changing shift pressure for the transmission for smoother shifts and traction control.

Without the MAF, the system defaults to backup methods for estimating torque / shift pressure using other inputs. The backup methods rely on estimates from tables that are mapped to the respective 4.0 or 4.6 engine originally in the Discovery.

Therefore, I assume with the LS, the MAF is a more accurate source of torque information (actual data) that can better compensate for the changes in torque output between the LS versus the 4.0/4.6. Deriving the torque from other values only gives estimated data that is a guess and is not as good at correcting for the different engine characteristics of the LS.

That being said, the torque estimates from other values may give values that are good enough for shifting. However, it’s also possible the converse could be the case as well. For the most part, I think it hasn’t been tested much long-term. I’ve heard some people say they’ve run without it for a while though.

I personally would avoid any idea about pulling the MAF sensor out of the MAF housing and sticking it in a larger housing. The tune in the Rover ECU is coordinated to read using a particular sized housing. Changing the housing without changing the tune would cause the ECU to read torque lower than it is, which I don’t imagine would be good (going from a 3in to 4in pipe for example, without changing the tune I believe would result in a mass air flow reading just over half (~56%) of what it should be). In my opinion, I think would better to run with no MAF than a MAF giving out bad data, especially data that incorrect. I feel like if the transmission shift pressure was set for ~half the torque of what it was receiving, that would hurt things.

I will also add that while the reduced diameter of the MAF is a restriction, by far in my experience the larger restriction is the Land Rover airbox / air filter design. Something like this: may be the best solution for keeping the filter enclosed and drawing air from the outside efficiently. I think replacing the airbox will have a significantly larger effect than pulling out the MAF, power-wise.

You can switch to the Compushift which doesn’t require a MAF (optionally uses MAP) and lets you set the shift pressure from the app. I’ve discussed that in a thread here. I need to finish the writeup, but wiring it in and keeping stuff working can be done, but is not straightforward. It’s a fairly large job, but also a fairly large upgrade too. Probably about $1k+ or so and they are supposed to be back in stock soon. For a performance engine, I think this would be the best choice so you can up the shift pressure. It also has other advantages, like being able to modify the shift map to match the engine and shift right where the LS wants.

 

Thanks All. Understood Bad idea to install Rover MAF in larger tube. I’ve got about a week and hope to be back on the road with the new engine. May run without Rover MAF as well unless I see it not performing well. Once this project is complete definitely will be reading CaptainAaron upcoming instructions on the Compushift.

 

Wondering what your Horsepower reading was ?

 

When the truck came from the factory the specs were 188 horse power and 250 foot pounds of torque. My baseline horse power with the Rover MAF installed was 172….I’m forgetting the torque figure.
After removing the MAF and running a 4” intake system, plus tweaks to the tune, the final figures were 240 horse power and 265 foot pounds of torque at the wheels. Not too shabby.

 

Tube size reminded me if the displacement of the 5.3 is 15% larger than the 4.6, the Rover MAF would be accurate if it was in a tube with I.D. of 3" in terms of RPM as that relates to shift points/ firmness; Assuming engine torque curves are proportional. Area of the tube size would be 6.84" vs. 5.94" and that ends up being 2.95xxx" or 3".
I doubt that's enough to get the 50 horses back, but might be less crappy than 2.75"??? I don't think Bernoulli cares.