RV8 inlet air flow?

[Steve_D]

I have a rover V8 3.5 efi in a Ranger Rover Classic that is becoming a Dakar.

The inlet has me confused so perhaps someone can spread some light.

I have seen people advise that gains can be made by fitting the Jag throttle body as it is larger or boring out the existing from its current 65mm diameter to 72mm.

Now here is where I’m confused.
Throttle body 65mm diameter = Area 3318mm sq.
AFM 44x50mm = Area 2200mm sq.
Inlet pipe into the air filter 44mm diameter = Area 1520mm sq.

So how can this work with the incoming area almost exactly half the throttle body? Secondly how can increasing the throttle body diameter improve things?

Is it something to do with changes in air speed and or pressure?



Steve

Edited by Steve_D on Sunday 21st October 19:49

[shpub]

The trick is not quite what your mates suggest:

72mm throttle body + Jag AFM which flows more air.
Throw away air filter/fittings and fit a bigger one.

The whole idea is to flow more air into the engine. May need to uprate the injectors as well to match the increased air flow.

Edited by shpub on Monday 22 October 09:01

[eliot]

Steve, on a 3.5 engine a 72mm plenum isn't nessesary IMO. Its just the fact that TVR used the same plenum and AFM on their 5L engine, which does become a restriction at high RPM (proved by datalogging)

As with all upgrades, it works best with a combination of changes such as changing trumpets,removing the afm and only then really on a larger / higher revving engine which requires more air flow.

[Steve_D]

Thanks for the answers but it still does not quite answer why LR designed it that way.
If the air flow into the air filter is sufficient then why is the throttle body twice the size.

I’m not looking to upgrade the motor or injectors quite yet but if I can gain something just by giving the filter a bigger inlet and a K&N filter then it’s worth doing.

This all came to mind when I started to look at making my own snorkel and trying to decide if a standard house drainpipe would do the job. It was then that I found the tiny filter inlet.

Thanks
Steve