original 2.5 V8 with Fuel injection

[Martins Stag]

I believe that the originally the Stag was designed to have a 2.5 V8 running on Lucas(?) injection. I don't remember seeing any photos of these prototype engines?
Does anyone have any detail or photo's at all?

Martin

[Steve AKA vitessesteve]

I think that the 2.5 evolved into the 3.0 and switched to carbs due to emissions. Sure somebody more familiar with Stag history will be add some more authoritative comment.

[FloydP]

There's a picture of the injection manifold and a few words about it on the Canley classics museum page
http://www.canleyclassics.com/our-museum/parts

[Martins Stag]

Floyd thanks for this I hadn't thought of looking at Canley's Webb site. I wonder if you could use it as a master and if it would fit a Mk2 engine?
Would the manifold work for modern efi? Just dreaming.....

Martin

[StagNL]

It was upped to 3 litres as the torque on the 2.5 PI variant wasn't good apparently - and the emission problem.

Julian

[JohnD]

Thanks, Floyd!

But StagNL, I am far from surprised if "the torque on the 2.5 PI variant wasn't good" - the butterflies for each TWO 312cc cc cylinders, 624cc, look to be the same size or smaller than an inlet for a 2.5 straight six, and that supplies 417cc.    The design was strangled at birth!

John

[RobPearce]

Surely small butterflies would strangle top-end power but have little effect on low-down torque. Besides, the PI throttles are over-sized, really. At a wild guess I'd say those butterflies look around 1.5" - HS4 size - which means it will breathe as easily as a 1500 Spitfire engine even on a 3 litre.

[Slimboyfat]

1 3/4"

[Martins Stag]

So with 4 x 1 3/4 butterflys for a 2.5 V8 it sound too large for me . I used to run my 2.5 Spitfire on 2 x 1 3/4.
So would this be why low end torque was an issue?  So should they have just reduced the size of the butterflys? It can't be that simple?

Martin

[RobPearce]

I don't know how the bore/stroke of the 2.5 compared to the 3.0 but...
The Rover K-series V6 2.0 has the same bore as the 2.5 but a very short stroke. It's also got a dismally mild cam because with anything sensible it had no low-end torque at all. Would rev its nuts off and put out nearly the same power as its big brother... as long as they increased the rev limit to 9000 or more.

A highly-tuned small engine that revs nicely can give lots of power. If you want good torque, there really is no substitute for cubes.

[Clive]

VVT helps.....but we are talking old engines here. Just think, that mild cam in the V6 could become very interesting if it could be controlled. Also some clever stuff going on with inlet tracts.

On that prototype inlet, 1 3/4 butterflies should be good for well over 200bhp. They won't be the restriction. Not so sure about the inlet design itself...

[V Mad]

It looks like the inlet tracts are quite short, and that would not be good for torque.  It looks like a design where performance was compromised too much by cheapness.

[Jonny-Jimbo]

Or packaging space...