Custom inlet manifold, 998
Turbo Mini Forums

Hi lads,

I dont really have any bulkhead/bonnet worries, so I've been considering making a custom inlet manifold.

Has anybody tried this?

I'm sure I read that Vizard suggested long runners post carb, but I dunno if there would be any benefit with a turbo?

Any thoughts? :)

context:

A whole day and no replies, dear me :( A few years ago you would have had a couple of pages by now. Sad.

I've spent a lot of time researching this subject and have carried out lots of simulations to determine optimum runner length. I'm using injection, but the is is equally applicable to a carbed engine. The simulations have been verified by dyno runs.

A long runner inlet will make as big an improvement as a highly modified cylinder head. It's a bold statement, but one that can be backed up by reference to many sources around the web.

The science of manifold design was only fully understood in the 1990s although the general principles were accepted well before then. Work by the best scientists developed a detailed understanding of the pulses present in inlet manifolds and also the method to predict the impact of changes to inlet tract design.

Until then, manifolds were really just seen as a packaging problem. Make them short to make everything fit under the bonnet was the general approach. I find it quite ridiculous that people spend £100s on cylinder head work and flow benches and then bolt on the factory manifolds. Air flow through an engine is driven by pressure pulses, not flow capacity. The pressure pulses can be harnessed to greatly improve the engines breathing capacity, even with a standard head.

The Metro turbo manifolds are about the worst option for the turbocharged 5-port from a performance/efficiency perspective.

Look under the bonnet of any modern high performance car and you will find long intake runners. Not throttle bodies bolted directly to the head or simple log style manifolds. Things have moved on, but the Mini world is still stuck in the 80s.

As usual, there is an optimum inlet runner length/diameter. It really depends on the spec of the rest of the engine.

A standard engine/cam/head will make the best torque with a runner length of around 450mm, but will be hampered above 6k rpm. Whereas a well modified engine with a big turbine will make best torque and rev to 8k with 250mm long runners.

Anything shorter then 250mm will hurt torque in the 3k-5k range.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

what Paul says.

for your instalation you may have an easy way out....

the 1.3 maestro manifold.

http://www.ebay.co.uk/itm/Rover-Maestro-1-...=item485e175a0a

however, with the std metro manifold it wont fit as the inlet manifold has to kink up at the head face to miss the metty exhaust manifold.... but if you are putting on a long inlet for pulse tuning... then you may as well put on a long exhaust for the same reasons....

Schrödinger's cat - so which one am I ???

A few questions stemming from this...

I have a metro turbo manifold, and now reading this you say theyre pretty cack. With my current planned setup, I'm going to be using a 5 port head, turbo phil ported metro turbo inlet, hif44, a montego turbo plenum, and feed the carbs float with a pitot tube. Now I'm going to be tidying up all around my bulkhead, and I can put a box in if needbe, is there any advantage of adding a rigid pipe from between the metro inlet, and the plenum chamber? even if it is just a short one? maybe around 2" in length, and 45mm in diameter, effectively increasing the inlet length.

Edited by Carlzilla on 12th Dec, 2013.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Ah okay, thanks for answering Paul.

I guess it's all down to interpretation. To me, they imply negativity towards other people posting on the forum.

I don't plan to change my forum settings and wouldn't want to force people to change their personal settings based on my opinion (Like Avatars for instance...)

I think this links to a writeup on the Advanced Products Torque Ram which is what I was talking about...

http://www.theminiforum.co.uk/forums/topic...on-in-mtn-1982/

(Photos are blocked here so I can't check).


Nial

1275 N/A Sprite, 998 T2 Turbo Mayfair
1275 EFi Turbo

These replies are really really helpful, Thanks very much.

I'm going to get my tape measure and some steel out and I'll report back :)

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

For the sensitive ones, I've changed my signature...

I thought the previous ones were better, but WTF....

Sorry, OP, not your fault.

Schrödinger's cat - so which one am I ???