Omega Owners Forum
Chat Area => General Discussion Area => Topic started by: geoffr70 on 28 December 2010, 20:32:57
-
I think I'm right in my understanding of multi rams.
In brief, a manipulation of the air flow so that it is narrow and restricted at low revs and idle, then wide and unrestricted at full throttle and high revs, so that at any point in the rev range the flow of air is fast so that more torque can be generated. Or something along those lines.
I know that the multi rams are meant to smoothen the torque curve, well I've checked the operation of mine, but at 4100 rpm it seems to take off.
Anyway to the point. Why don't the majority of other cars have multi rams? Anyone know?
Thanks
-
It's more about keeping the intake system near resonance over a wide range of speeds. At lower RPM an engine makes better torque when fed from a long intake duct. At higher RPM you need a shorter duct for best results. Any engine will have surges and flat spots due to resonances in the intake and exhaust system and making the intake system variable is a good way of moving these resonances around as the engine accelerates, so they can be positioned to cancel each other out and give a flat torque delivery.
It, or something similar, is probably used on more engines than you realise. ;) http://en.wikipedia.org/wiki/Variable_length_intake_manifold
Kevin
-
Nice wiki find Kevin, I'd always wondered what the theory was behind the variable inlet.
-
That's an interesting read, thanks for that.
-
I think I'm right in my understanding of multi rams.
In brief, a manipulation of the air flow so that it is narrow and restricted at low revs and idle, then wide and unrestricted at full throttle and high revs, so that at any point in the rev range the flow of air is fast so that more torque can be generated. Or something along those lines.
I know that the multi rams are meant to smoothen the torque curve, well I've checked the operation of mine, but at 4100 rpm it seems to take off.
Anyway to the point. Why don't the majority of other cars have multi rams? Anyone know?
Thanks
I think the simple answer to your question is cost and complexity.
There are a vast number of tricks that can be done to improve i.c. engines and steering, brakes, transmissions. But only enthusiasts will buy them and most manufacturers have to look to the mass market.
In the case of multi-rams, they are only really useful on naturally aspirated engines and they have turbos and superchargers looking over their shoulders as soon as they get too complicated.
-
Quite a few cars do have variable inlets
-
Quite a few cars do have variable inlets
12 valve senny didn't pitty though
-
Quite a few cars do have variable inlets
12 valve senny didn't pitty though
2.6 12 valve did!!!
-
Quite a few cars do have variable inlets
12 valve senny didn't pitty though
If I remember rightly it did. I've had a 12 and 24 valve senny. The sennys had dual ram
Both 3 litre though. My dad had a 2.5 12v, I can't remember if that had dual ram or not.
-
Loads of engines have variable inlet manifolds.....inlcuidng diesels!
-
Loads of engines have variable inlet manifolds.....inlcuidng diesels!
That's interesting, I certainly didn't know that diesels did!
I take it having a variable inlet on a charged engine wouldn't be useful then?
-
Kinda heavy going but you might see whats intended...
http://books.google.co.uk/books?id=RC_k4q6y-JIC&pg=PA183&lpg=PA183&dq=pulsed+constant+pressure+turbocharged+marine+diesel+engines&source=bl&ots=rz8LwxUDUR&sig=5DW7UEYs1sTT2-8-p_gSPvISTHc&hl=en&ei=tK8bTYDNA86ahQeGko3yBA&sa=X&oi=book_result&ct=result&resnum=2&sqi=2&ved=0CCIQ6AEwAQ#v=onepage&q&f=false
-
Kinda heavy going but you might see whats intended...
http://books.google.co.uk/books?id=RC_k4q6y-JIC&pg=PA183&lpg=PA183&dq=pulsed+constant+pressure+turbocharged+marine+diesel+engines&source=bl&ots=rz8LwxUDUR&sig=5DW7UEYs1sTT2-8-p_gSPvISTHc&hl=en&ei=tK8bTYDNA86ahQeGko3yBA&sa=X&oi=book_result&ct=result&resnum=2&sqi=2&ved=0CCIQ6AEwAQ#v=onepage&q&f=false
Thanks for that! It does look like heavy going! I'll save the bulk of it for the long nights at work!
-
Loads of engines have variable inlet manifolds.....inlcuidng diesels!
That's interesting, I certainly didn't know that diesels did!
I take it having a variable inlet on a charged engine wouldn't be useful then?
Yep, its basicaly what the swirl flaps do on the multivalve diesel engines.
-
Loads of engines have variable inlet manifolds.....inlcuidng diesels!
That's interesting, I certainly didn't know that diesels did!
I take it having a variable inlet on a charged engine wouldn't be useful then?
Yep, its basicaly what the swirl flaps do on the multivalve diesel engines.
When they actually stay attached to the rod :P
-
Nice wiki find Kevin, I'd always wondered what the theory was behind the variable inlet.
Here's an interesting article on a Variable Compression 2 Stroke engine. The idea's been around for a while but has recently been picked up again by a collaboration between Lotus Engineering, Quens University Belfast, Jaguar Landrover and fuel injection specialists Orbital Corp. They are boasting fuel efficiency savings of up to 30% when compared with some of todays four stroke engines. It is also able to run on more than just one fuel type and uses "Homogenous charge-compression ignition" meaning no spark plug. I think up to now they have only been experimenting with a single cylinder, but plan to start looking a multi cylinder. One interesting fact I picked up on was that for them to meet the industry standard for cold starting without assistance of -30DegC, the engine compression ratio would need to be 50:1. I think they have managed -25DegC up to now.
http://en.wikipedia.org/wiki/Variable_compression_ratio
-
Loads of engines have variable inlet manifolds.....inlcuidng diesels!
That's interesting, I certainly didn't know that diesels did!
I take it having a variable inlet on a charged engine wouldn't be useful then?
Yep, its basicaly what the swirl flaps do on the multivalve diesel engines.
When they actually stay attached to the rod :P
Nah, fixed once and for all in 2006 with a modified inlet ;D
-
Loads of engines have variable inlet manifolds.....inlcuidng diesels!
That's interesting, I certainly didn't know that diesels did!
I take it having a variable inlet on a charged engine wouldn't be useful then?
Yep, its basicaly what the swirl flaps do on the multivalve diesel engines.
When they actually stay attached to the rod :P
Nah, fixed once and for all in 2006 with a modified inlet ;D
Interesting, neighbours e39 D has had swirl flaps removed and blanking plates fitted, reckons it makes no odds to remove them, they are about the area of a 1pence piece on his....absolutely appalling construction btw.