CosRush

If i were to improve airflow through my plenum, this would cause the VE to change.

The change should effect the entire map making it leaner throughout due to any increase in airflow, but what im wondering is can this be corrected by increasing the fuel pressure???

i.e. With the car running as it should (runs sweet ), fit modifed inlet then road test car, take lambda readings, adjust fuel pressure up and retest until lambda is restored to original setting......

Would this work???

JesseT

It will work if the change is not too drastic. If however you are moving the inlet resonance frequencies by changing the dimensions, then you need to address the map directly.

BMEP

The difference that the Intake manifold would make to power output would have to be quite substantial to warrant an increase in fuel. For instance if the intake manifold gained a 10% flow increase at a particular rpm/load point then you would expect a 10% gain in power at that rpm/load point and offcourse 10% more fuel would be required and possibly a decrease in Ign advance due to the increased in dynamic compression.

If there was a gain you will find that the gain will be at boost/certain rpm’s only and not at light throttle/cruise. If you increase the fuel pressure to compensate you will find it “may” help at certain rpm's/load but not everywhere and may run rich at light throttle/cruise due to the increase in fuel pressure.

I'm talking from experience based on the re-tuning i did on my Autronic ecu once i fitted my Intake manifold to my cossie.




Good luck with it mate

CosRush

Oh

So there's no way of using a new plenum design without having to have a remap???

Thats bad news

Like you plenum by the way

Who made it???

BMEP

CosRush,

It really would come down to the design of the Intake manifold and how accurate you want the map to be. Its worth fitting your new plenum and trying it on a rolling road/chassis dyno cos if there is a major lean out then the dyno operator can back off the throttle.

The Inatke manifold was made by a friend of mine "Jim", if you would like one built there is one slight problem..... we are on the other side of the world mate (Australia)

CosRush

We have things called 'aeroplanes' here, they can move things all over the world

Only joking , thanks for the advice, basically i want to switch to the 'Swedish' style plenum as its known, not only because its a better design, but because of space limitation is much better suited to my setup........

CosRush

On a more serious note, who actually designed it?
What formulas did you use?

With the inlet runners spaced out and the inlet at the end of the plenum the airflow obviously has to flow differently for each cylinder as each effective runner (throttle plate to inlet valve) is of a different length.

How did you cater for this, as ive been looking into the Maths of it and its not that simple at all.......

yet i know of a few people who have made their own and has shown to work well.
Although none of the ones ive ever seen have been tested for flow through each cylinder to ensure they are the same, so potentially some people could be running lean on one cylinder.

Any thoughts?

JesseT

If you look closely, the inlet seems to be at the middle.

CosRush

yeah, sorry i meant on the normal 'Swedish style'ones......

throttle housing on extreme end.........

BMEP

CosRush,

As JesseT said , the intake to the plenum IS in the middle. The Intake manifold spent more time on the flow bench then it took to make. Yes the flow threw the runners are very very close. There are dividers within the "elbow" to deflect the air to runners 1,4. See here for the performance of the Intake manifold combined with the rest of my engine spec.

https://passionford.com/forum/viewtopic.php?t=151775