Induction

[JMF894]

Hi all a couple of questions regarding the induction system:

1) To save me lifting the plenum again can anyone tell me the dimensions of the standard trumpets for a 450 please? 38mm across the top? But how long are they and do they taper?

2) Does the air filter (i have a k&n) need to be next to the afm as it always seems to be in pictures or can i fix it to the end of some flexipipe and mount it lower down/further away from the flapper in an attempt to get cooler air through it?

3) What experience does anyone have positive or otherwise of the insulator gaskets for the trumpet base as offered by ACT for example?

4) If i fit some bigger/shorter trumpets will the flapper automatically compensate and chuck more fuel in or will the car need to be set up and the flapper adjusted accordingly?

Cheers Jimbo

[pwd95]

JMF894 said:

Hi all a couple of questions regarding the induction system:

1) To save me lifting the plenum again can anyone tell me the dimensions of the standard trumpets for a 450 please? 38mm across the top? But how long are they and do they taper?

2) Does the air filter (i have a k&n) need to be next to the afm as it always seems to be in pictures or can i fix it to the end of some flexipipe and mount it lower down/further away from the flapper in an attempt to get cooler air through it?

3) What experience does anyone have positive or otherwise of the insulator gaskets for the trumpet base as offered by ACT for example?

4) If i fit some bigger/shorter trumpets will the flapper automatically compensate and chuck more fuel in or will the car need to be set up and the flapper adjusted accordingly?

Cheers Jimbo

Hi Jim, my angle on it.
1. They all may be different but just trumpets won't make much difference.......
2. Air filter would be better somewhere near the front where it can draw cold air & feed it through an insulated pipe to the AFM aka Chim/Griff.
3. All helps but again small gain.
4. Flapper system is very primitive system compared to the later stuff. Can't really be 'mapped' like the hotwire systems just a matter of using an adjustable fuel pressure regulator on the RR to get the mixture right to suit any modifications.

Better off puting the money towards getting a mappable ECU & coilpacks like Megasquirt or Emerald set up on what's there already. Probably release a lot more power per £.

My old 350i with the 450 JE lump had a flapper ecu with an adjustable mixture knob!
It could fool the ecu in to thinking the engine was cooler that it actually was. The ecu would then keep the mixture richer than normal to suit. Had to be set up on a dyno to get the right setting.....



If you could get hold of one of these I'm sure someone like Mark Adams would be able to make it talk to your Air Flow Meter properly.

[Wedg1e]

I run a plenum insulator (10mm thick) and after a good run it's possible to place your hand on the plenum top and keep it there; you can't do that with the standard installation. There must be some reduction of heat-soak into the intake air but what percentage gain in power it gives (if any), I don't think anyone has yet documented.

[vampire222]

Wedg1e said:

I run a plenum insulator (10mm thick) and after a good run it's possible to place your hand on the plenum top and keep it there; you can't do that with the standard installation. There must be some reduction of heat-soak into the intake air but what percentage gain in power it gives (if any), I don't think anyone has yet documented.

You had similar heat insulating intake gaskets for honda's and they gained about 5% from it, keeps your intake manifold a LOT cooler.