9 replies to this topic

[Wazzah]

About the SPI manifold ears.

Remove or leave as is?

[andysspanners]

Very good question. Im facing the same dilemma porting my spare manifold! 

SPI,1380, ported large valve head, larger throttle body, adjustable FPR, larger injector.....
remove the ears or keep them? or maybe something in-between....

[Pops_Guild]

I think you probably know this already but the 'ears' were introduced in 92 to help solve two cylinders being lean. They aid the flow and mixture to be even across the siamese ports. 91-92 the inlet manifolds were without the ears, so I assume Rover did it because the uneven fuelling was causing issues.

 

That was on standard engines (both normal and Cooper). I've experimented on my relatively standard Cooper with both inlet manifolds and I can confirm that you get uneven fuelling by examining the plugs with the non-ears manifold. So on a standard / mild Cooper I don't think it makes sense to remove the ears. 

 

When folks ask me to refurb their manifold and its a non-ear version I give them a choice to change to an ear version, all that have, have reported their Minis run better with the later type.

 

 

When building a high performance system as you are Wazzah, you might get different results. Your 45mm TB & adjustable FPR might introduce a very different flow from the original setup so its possible it could remove the need for the ears and not incur the uneven fuelling.  Your side-draught setup isn't using the SPI manifold though right?

 

The honest answer is I don't think anyone will actually know, SPI tuning is largely ignored, usual porting logic says remove anything that gets in the way of the mixture flow but in this case the ears do seem to do something positive. 

Attached Files

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Edited by Pops_Guild, 25 September 2020 - 10:31 AM.

[sonscar]

The definitive answer would be to run the same motor with both manifolds back to back on an engine dyno and fully measure the inner/outer AFR and output,but who can afford that?IExpect Rover did but that was a standard motor.Seat of Pants dyno I find to be wildly innacurate.Happy tuning.Steve..

[andysspanners]

yep......
seat of the pants testing whilst inner/outer afr checking and spark plug checking will have to do for me.....

I thinking along the lines of increasing the size/cleaning of the inlet whilst keeping the ears but reducing them in size to start with
 

[Wazzah]

MPI's don't have ears.

They get over the port problems by staged injection.

I'm working on a little ECU project that definitely allows twin lambda sensors.

One on the Y and one on the centre branch would enable Soncars idea.

[sonscar]

I believe Mpi injection is not staged but sequential.I have no hands on experience with Mini injection but I did lots of reading when injecting my MGB,which is incidently staged running on two injectors until 2200 rpm then four after that.When I built this in 2003 Siamese port injection was not available aftermarket so I experimented and ended up with a system which works but is sub optimal.I am easily satisfied.have fun,Steve..

[Wazzah]

Very interesting Steve.

[podifold]

Just bumping this to the top to see if anyone else had any other ideas/comments about the "ears"?

[podifold]

From this interview with Mike Theaker who worked on the TBI system at Rover:

 

 

There were emissions limitations caused by fuel puddling in the manifold - which we tried to cure by inserting weirs in the manifold tracts.

 

http://www.turbomini...ts/493117-1.pdf