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[feeutfo]

3.0 twin exit box is for show. Oh the irony. 

It's a silencer first and foremost. It is not restrictive with either exit.

[2woody]

as simple as I can put it....

the shape of the power curve is determined by a) the cam spec, b) the compression ratio and c) the inake ram pipe diameter and length.

large, short ram pipes, together with high compression and long duration cams = a top-heavy power curve (all the power at the top end)

small, long ram pipes, together with low compression and shorter cams = a low-rev biased power curve.

If the manufacturer can't fit variable compression or variable cam timing, then one thing that can be altered is the length of the ram pipes.

In an admittedly small way, the multi-ram system takes the first part of the power curve from the long rams, adds this to a middle part from medium rams and adds that to the high-end from the short rams. The result is better low-end power, better mid-range power and better high-end power.

you're maybe gaining 10 BHP by leaving the system in place.

[2woody]

as simple as I can put it....

sorry, that's a bit condescending. It would be very easy for me to put too much detail into this - I almost did a Masters degree in cam timing and inlet system design at one point.

[feeutfo]

Go on....

[aaronjb]

I, for one, am interested to understand more about how compression ratio affects the torque curve - all I've ever really understood about it is lowering to prevent pre-ignition on forced induction engines

[2woody]

it's about cylinder filling really. If you have long-duration cams, then at low revs a lot of the intake mixture will get blown back out of the inlet, so the cylinder may be only 50% full. An over-high compression ratio will help to redress the balance.

Usually, CR is worked out using cylinder full and clyinder empty. A more realistic method is to use cylinder contents at inlet valve closure point. This gives a link into the cam spec and how that affects the torque curve.

In general, you need as high a dynamic CR as possible to give the best power and economy, but not to stray into pre-ignition.

[Martin_1962]

Why would they spend a lot on the induction system unless it was beniificial.

Some of the valves improve high RPM air intake

thats exactly what i thought, but then with more thought i came to the conclusion that the calibra/cav works just fine without the multi ram

"why would they spend a lot on the induction system unless it was beniificial"

i dont know, you tell me?

when tuning for power one normally takes out all restrictions and most even go as far as shaving off fractions of a mm off the throttle plates, and even removing the traction control.

i have read that the multiram is there to help fuel consumption and flatten the torque curve....why is this benificial?

Because they are cheaper cars and it saves money. Omega was top of range and they fitted it out better than the other cars. Also Omega is heavier and needs the boost in torque more

[Kevin Wood]

Because they are cheaper cars and it saves money. Omega was top of range and they fitted it out better than the other cars. Also Omega is heavier and needs the boost in torque more

.. and the engine's not been shoe-horned in sideways so there is actually room for it under the bonnet.

[mr carl]

This is my multi ram, nothing was moving with the throttle full open....excuse the sound it my be my phone because the engine does not sound like that

http://static.photobucket.com/player.swf?file=http://vid283.photobucket.com/albums/kk311/mrcarlxx/VIDEO0004.mp4

[Pitchfork]

Leave it alone!

Because it can not be, has not been, and will not be improved upon for this application. Thats why it is the way it is! Gm RnD ain't daft.

Perhaps a better approach would be to say why you think it should be changed. What you want to achieve and why...?

If it's for track work then fine, rip it out, chip it, make it all top end, and ragthe tits off it in every gear. But for road I big lump like the omega needs grunt to get going. Which is what the multi ram system gives you along with top end as well.

Induction tuning isn't a simple thing to get right afaik.

If you want to see what its like without it, disconnect the plug and or vac pipes to it and go for a spin. It's flat as a witches tit.

Actually I know a Witch in Reading who has a fine pair of protruberances - would you like her address?

[feeutfo]

Leave it alone!

Because it can not be, has not been, and will not be improved upon for this application. Thats why it is the way it is! Gm RnD ain't daft.

Perhaps a better approach would be to say why you think it should be changed. What you want to achieve and why...?

If it's for track work then fine, rip it out, chip it, make it all top end, and ragthe tits off it in every gear. But for road I big lump like the omega needs grunt to get going. Which is what the multi ram system gives you along with top end as well.

Induction tuning isn't a simple thing to get right afaik.

If you want to see what its like without it, disconnect the plug and or vac pipes to it and go for a spin. It's flat as a witches tit.

Actually I know a Witch in Reading who has a fine pair of protruberances - would you like her address?

In witch case, she'll be merely a trainee Witch, so she'll have all her teeth as well. Decisions decisions. 

[TheBoy]

This is my multi ram, nothing was moving with the throttle full open....excuse the sound it my be my phone because the engine does not sound like that

http://static.photobucket.com/player.swf?file=http://vid283.photobucket.com/albums/kk311/mrcarlxx/VIDEO0004.mp4

Hard to tell if it revved high enough with the noise, but that certainly wasn't moving.  Couldn't see the back one, as you videoed the scuttle instead

[mr carl]

This is my multi ram, nothing was moving with the throttle full open....excuse the sound it my be my phone because the engine does not sound like that

http://static.photobucket.com/player.swf?file=http://vid283.photobucket.com/albums/kk311/mrcarlxx/VIDEO0004.mp4

Hard to tell if it revved high enough with the noise, but that certainly wasn't moving.  Couldn't see the back one, as you videoed the scuttle instead

oh bum, i just pointed it in the direction while i was looking at the throttle 

do you have to hold it at full revs for a amount of time, before it moves?

i just realised i put this video on the wrong bleeding thread 

[weasel]

Ok, i guess its time i added my 2 cents...
Here is what ive made up and fitted to my mv6 to remove it.....


And here is the dyno graph it produced....



If anyone has a dyno graph from a standard one for comparsion, that would be great?

[TheBoy]

Only really worth comparing on the same engine TBH