has anyone used an intake plenum such as a snort plenum, if so did you notice any differences of power in the rev range

I know its not exactly what your asking,

But I am using a set of lowers that were on a nizpro turbo plenum. They had been ported and the little butterflies in the runners were removed. I was told this was fine for N/A.

Hasnt made any noticeable difference really and logic would say it would only help breath a bit better at high RPM. However I wont get maximum benefit until I fit my lumpy a** cam and ported head that will allow my motor to accept that much air lol.

Only cost me $100 but I defiantly wouldnt go spending large amounts of money unless its for showing off. (mine look stock lol)

If the short runner butterflies have been removed you just lost all the benefit of the BBM,

better placement of T/B and more even flow than a log manifold. Also the longer intake piping makes a f**k load more difference than the s**t extra 15 cms it has to go around the long runners. Also those butterflies are always open at high throttle therefore useless and impeding flow at high RPM.

The claim was better fuel economy as they were shut at cruising speed therefore it had to go the way of the long runners producing more torque at low RPM.

Its a load of crap, fuel economy has not changed at all. From what I can tell of the FG intakes, they do not use a BBM style manifold. Seems to just be normal runners after the T/B, albeit plastic but thats not the point.

they switch at a set RPM (3800rpm) not a throttle position, and the narrow long runner is about 30cm longer and is for increased torque. It was never an economy thing, it was always about producing more torque.

dont bother mate, plenums are no where near as good as other mods when talking power vs $$$
in saying that, id imagine you would pick up a couple rwkw if that

Well perhaps they were designed with only a stock motor in mind as I dont feel that have not lost any torque. And if you ask anyone who has done a BBM conversion on their ea-ed they barely notice a difference, keep in mind that not only do they have that extra 30 cm but they also have probably a meter and a half or so of extra intake piping.

Also, at high RPM when the butterflies are open they do nothing but restrict flow and as i mentioned earlier when i put on my ported head and big cam it will make a difference.

If i could afford it I would have done back-to-back dyno runs for my own knowledge. Even in best case it cant of been that great if it was dumped off the fg falcons.

Ive still got the original runners and if I wasnt happy with how it felt id just swap em back.

Edit:

Also I want to know how they know to swap? I know it works on vacuum but the vacuum on my heater lines goes away as soon as I pass about 1/2 throttle and wouldnt that cause the runners to open as well?

The runner switching is ECU controlled through vacuum solenoids.

It wasn't "dumped" for the FG, it was replaced be a more refined system, (the BBM is a 15 year old design) the FG manifold variable plenum geometry. Apparently the new system achieves a better torque spread with less intake noise. the new plastic manifold is also 5KG lighter, and in about 6 years time they will all start devoloping vacuum leaks just like all the other plastic manifold car makers have been fitting for years.

Most people that fit them EA-ED dont fit the EL ecu that has the right tune in it. All they do is use a Jaycar RPM switch.


as far as restricting flow, The combined cross sectional area of the two runners is greater the area of the largest part of the port. The port draws through both runners when the BBM is open,

I have put these manfolds and cylinders through a drop saw and cut them up to find out exactly what makes them tick.
I can also calculate the change in effective RPM of the runner length brought about by the change in valve timing from your new cam. i can also calculate the effect of the ramport length (pipe from air box plenum) and tell where the old EA-ED pipe would have been helping vs: where the EF-AU would have helping, then there the numerous custom made ones that all them to significantly different lengths.
Air temp also effects the speed of sound, which will change how any given valve timing/ runner length/ plenum volume/ ram port length combination would resonate, so heat soak and position of any intake to the filter will change things too.

Are you making custom intakes then?

If you had the funds to make any intake, what would you make?

to be honest, I just don't have the time to do it.
see if you can get a hold on an FG manifold when people start modding the crap of the FG XR6T.
and start with that.

start with that? do you mean you would build a design based on it? Do you think there is any merit to tuned length intake runners?

do you think all the car manufacturers would be spending huge amounts of money and time designing them if they didn't work?

Well i try to be humble when I can, yesterday i replaced my stock lowers into my motor. Yes you were defiantly right. seems to be much more responsive than before.

So ill be selling them off again, hopefully back where they came. A motor with a custom top plenum meant for a turbo.

cheers

tickford6, you would make a damn good engineer, they pay well too....

my old boss was a Engineer who worked for the Council, and he knew bloody well everything in theory