| Author | Message | ||
     Robert Noel Reddington Grand Master Username: bob_uk Post Number: 427 Registered: 5-2015 |
The design of the exhaust effects power, noise, output and economy. Obviously. But how is an exhaust designed. Obviously it has to physically fit the car. I have a theory that given a long enough plain pipe muffers wouldn't be needed. How long probably 100 foot. Which is not feasible. 3 types of mufflers. Perforated tube with glass or rock wool around the outside inside a tubular case. Generically know as a cherry bomb. These filter high frequency noise and give a rumble sound. Baffles which make the gas double back on itself. This causes the pulses to collide and break up, this cause back pressure and filters the low frequency. Expansion chamber. This is a void. When the gas reaches the chamber it expands anf slows down. This defuses sound. When it reaches the exit back fown to exhaust pipe size the gades speed up again but with pulses merged. Exhaust systems are made with a combination of these 3 types. Catalytic convertor also muffle a bit. Power and economy go together. To explain I will use a 4 cylinder engine first. When the exhaust valve opens the gases explode out of the port. This pulse not only gies down the pipe but will U turn and pulse towards another exhaust port. The pulse can actually go backwards. Waves in the sea can go one way and the current in a different way. So if the manifold pipe from no 1 cylinder is joined to no 4 cylinder when the no 1 exhaust opens no 4 is shut. Also if the place where the pipes join is a long way from the valve the pulse won't have time to bounce up no 4 exhaust pipe and also the valve is shut. If yhe pulse hits an exhaust valve on overlap with the inlet valve power will go down due to poor cylinder filling. Cylinders 2 and 3 are the same. Then 2 and 3 are joined to 1 and 2 furyhet doen the system. 1 into 2 and 2 into 4. This set up gives good all round performance. V8 systems. Two types of V8. Flat plane crank engines like Ferrari are two 4 cylinder engines on a commom crank. The exhsust system follows the 4 cylinder version only two of every thing nice and easy. Cross plane engines like RR pose problems because the opposite cylinder is on the opposite bank which makes for a plumbers nightmare. Plus this also means that the carbs get uneven pulses. To get round carb uneven pulses the carbs are connected A1 A4 B2 B3 and the other carb B1 B4 A2 A4. To do this the inley ports go under and over each other. Dual plane inlet manifold. The exhaust manifold is a mess. Because the pulse is going into other cylinders. This type of arraignment must have a cross over which is the y piece or x piece. It's about pumping efficiency. On full throttle the engine is meant to suck in 6750 cc of fuel and air. By using the exhaust to drag out gases and pull new ones in an engine can suck in more than its physical capacity. More power. The main killer of power on a Shadow is the exhaust manifold. There's a photo of a 69 shadow with exhaust manifolds comeing out of the bonnet and going over the roof, a bit drastic. The car didn't finish the rally in North Africa. In my mispent youth we used reverse mega phone muffers which were louder than no exhaust system. A 500 single on a mega phone at 5000 rpm and pulling hard is very loud. New type of muffler is called a vortex. Inside is a helix of smaller pipes which causes a vacuum in the main pipe like a steam injector does when it injects water into the boiler. However this won't overcome bad exhaust manifold design. The vortex is stainless steel 304. And not cheap. | ||
| Bob Reynolds Grand Master Username: bobreynolds Post Number: 321 Registered: 8-2012 |
"The main killer of power on a Shadow is the exhaust manifold." It takes some really special engineering to make a 7 litre engine and get just 220 bhp out of it. I often wondered how RR managed it. | ||
| Robert Noel Reddington Grand Master Username: bob_uk Post Number: 434 Registered: 5-2015 |
The engine can't breathe properly. There's just not enough room for proper exhaust manifolds. I have been checking Vortex silencers. They are claiming up to 25% power and mpg extra. The science behind the Vortex smacks of wishful thinking and bad science. The whole concept relys on the twisting of exhaust gases like a helix. This creates low pressure and draws the gases out. 25% gain engine tuning wise is huge. So huge that car makers would be swarming all over the Vortex. However the cost when having a bespoke exhaust made up is about the same with or without Vortex silencers. Unless one is running without mufflers. There are tables for pipe dia for given bhp. 2" is about 225bhp and 2.5 is about 275bhp. The smaller the pipe the quieter the exhaust. The Shadow is 2". RR put the smallest pipe possible without strangling the engine to much. My car is 60mm bore which is 2.3" bore. If I were to go to say 3" then getting the system to run quiet gets differcult. After market exhaust stuff is also aimed at more noise because You tube has videos which emphasis the sound aspect. I think a little bit of exhaust noise when the engine is pulling is not necessarily a bad thing. Plus the air intake to the carbs. UK legal limit is 100 db. 100 db is quite loud. | ||
| Robert Noel Reddington Grand Master Username: bob_uk Post Number: 440 Registered: 5-2015 |
Back pressure and pipe dia. Back pressure is thought to be by some necessary for the correct running of an engine. Often quoted is the loss of low down grunt. This mistake in thinking comes about because when too bigger pipe is used the low down power drops thus less back pressure has caused it due to bigger pipe. The real reason is that the bigger pipe has reduced gas flow speed. As the gases move along the pipe they pull a vacuum behind the pulses. Which does 2 good things. 1 the piston doesn't push rhe gases out. And in some cases the vacuum is pulling the piston up with a small amount of force. 2 on valve overlap the vacuum is sucking on the inlet charge starting to come in often before tdc. Back pressure actually loses power. Because the piston has to pump against it. Size of the pipe if a too bigger pipe is used then the speed of gas drops and so does the savangeing effect. At high rpm the big pipe will produce more power however not a lot more say 1%. To smaller pipe will give low rpm grunt. But at high rpm the volumetric efficency will be pants. So the choice of pipe size is not critcal but must be considered. The Shadow 1 is 2" pipe or 52 mm. I am using 60mm. This just about right for 200 to 250 bhp range. The RR design is like a curates egg good in places. 2 things let the side down The log type manifold and that front box. I think its restrictive. The good points. The rear resonator is a glass pack cherry bomb. The round box is an expansion chamber. The next wedge shape silencer is also an expansion chamber. The pipe at 2" is a wee bit on the small side but does cover the rev range. The Y convergence is in about the right place and balances out the right left left right right left left right bank firing. Crush or press bends are restrictive so I use mandrel bends which keep the pipe round. There will always be some back pressure. Ideal system would be no mufflers just a straight pipe with no bends. Note. Aero piston engines. The makers will specify a maximum back pressure. Usually around 1 psi. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 3221 Registered: 4-2003 |
What is the message here ? If the exhaust system is damaged don't we simply repair it to meet its original, optimal state ? | ||
| Bob Reynolds Grand Master Username: bobreynolds Post Number: 322 Registered: 8-2012 |
We might be able to improve on it.  Personally, I would just buy a new one. | ||
| Robert Noel Reddington Grand Master Username: bob_uk Post Number: 441 Registered: 5-2015 |
Original and optimal unfortunately don't go together in this case. The manifolds are such a mess that anything fitted after the log manifolds won't yield much improvement power wise. Silence wise the standard system is about the best I have heard or not heard. My system differs from standard in that the tail pipe resonator is 4" longer and 1" bigger in out side diameter and has twice as much glass pack. Plus the tail pipe is 3mm wall stainless 304. My system is just as quiet and will flow better. When I cut the original apart I found louvred holes in the inner pipe. Louvred holes cause back pressure. I would like to get inside the first box so I can re-arrange the baffles. I have in mind adjustable baffles, with a reflector cone. I make exhaust systems because I can. The Shadow is so untuned that it's easy. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 3222 Registered: 4-2003 |
Here we go again. These cars are 35-50 years old and by design understressed and incredibly long-lived. They were never exactly inferior in any way when new, and if you want modern just buy a new Continental GT for heaven's sakes. Fooling around with practically anything, as one did with MG TCs and FJ Holdens, may bring a one cent benefit for a while. Then you sell the vehicle to a new owner at some stage. That proud owner may take it to a specialist for routine maintenance. The outcome will no doubt be the owner being turned away (with a few expletrives thrown in by the specialist) or a huge bill to put it back to the way it can be supported. It happens too often here: a new owner buys a well-presented Silver Shadow for just $20,000 then has to spend $10,000 on repairs and another $10,000 to reverse the improvements. That assumes that the motor and drivetrain are essentially sound as an in-situ motor renovation (pistons, liners etc) will add $20,000 or a full motor overhaul $30,000 plus. So, perhaps the simplest way to improve the breathing of Silver Shadow is to sell it and to buy a 1995 Rolls-Royce Flying Spur. | ||
| Bob Reynolds Grand Master Username: bobreynolds Post Number: 323 Registered: 8-2012 |
The Shadow was never a perfect car, even when new. There are many ways these cars can be improved and brought up-to-date, if the owner so wishes. In most cases, our cars are not museum exhibits. If the owner values driveability, usability and reliability over originality, then that is their choice. We are all 'grown-ups' and able to make our own choices. In many cases, modifications will involve a simplification of the system and bringing it into line with current practices, making maintenance easier and less specialised, not more complicated. I see no harm at all in doing effective modifications, but I would make a list of these and pass it onto any new owner. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 927 Registered: 5-2012 |
Re: If the owner values driveability, usability and reliability over originality, then that is their choice. I agree this is the owner's choice. However the sentence can be interpreted in vastly different ways. It covers simple upgrading to electronic ignition, which is easily reversible back to the original points system, or it can mean replacing the engine with a big block Chevy and converting to conventional brakes. Not quite so easily reversible. For my part, my general rule is "can I easily convert my car back to original." Any changes I make, I keep the original parts for reconditioning. I suspect this is also true for Bob's car. I think there is also a difference to cars that have well considered minor upgrades (e.g. spin on oil filters) and cars that have been bodged because the owner could not afford to maintain the car properly. With the low prices of these cars, I suspect minor changes are not going to affect sale prices too much, particularly if the changes are documented and the car is in really good condition. If ever these cars appreciate enormously, which I doubt, then I suspect there will be a mad rush to get them back to original spec. Geoff | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 3223 Registered: 4-2003 |
I assume that you mean downgrades. Even a Conti GT has an oil filter element, as does a Phantom. The spin filters are long gone. | ||
| Bob Reynolds Grand Master Username: bobreynolds Post Number: 324 Registered: 8-2012 |
The spin-on oil filters are only 'long gone' because of environmental issues. Not because they are inferior. I know which one I'd rather have. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1615 Registered: 6-2009 |
Bob, Seriously, where have they disappeared? The USA tends to outlaw things due to environmental concerns fairly quickly. Spin on oil filters, and the recycling industry for same, are both still going strong here. I have yet to see a cartridge filter sitting out as stock on the shelf of any department or auto parts store. Spin-ons are already messier than I'd like. I definitely don't relish the idea of a return to cartridge-type filters for oil. There certainly is no problem with the efficacy of spin-ons versus cartridges since both are pretty much the same as far as filtration media goes. No one's rushing away from paper filtering media. Brian, who believes Twain's quotation on his death has a parallel here | ||
| Bob Reynolds Grand Master Username: bobreynolds Post Number: 325 Registered: 8-2012 |
Yes, paper element type filters have made a come-back here in Europe since the 1990s. There is less waste involved, as the whole spin-on cartridge has to be thrown away. A retrograde step if you ask me. But don't worry, you Americans have that pleasure soon to come: https://en.wikipedia.org/wiki/Oil_filter You can even get conversion kits to replace your convenient spin-on filter with a messy cartridge type. What sort of idiot would do that? | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1616 Registered: 6-2009 |
Bob, Thanks, but I'll still be sleeping soundly at night knowing it will probably be long after I'm dead before the spin-on filter disappears from the US market. web search on oil filter recycling Since the entirety of the metal in a spin-on can be recycled and even the waste oil can be extracted from the paper media for other uses I just don't see them going the way of the dinosaur. They're just too convenient, conventional, and make so much more sense than cartridges in so many ways. The embedded base is just huge. There's absolutely no engineering justification for the switch, that's for sure. Brian | ||
| Robert Noel Reddington Grand Master Username: bob_uk Post Number: 450 Registered: 5-2015 |
I have often wondered if spin on filters were really an upgrade. The only plus is that its quicker. I apply the same rule that any thing altered must be able to be returned to the original spec. In this case one clamp and one bolt and the original box will go straight on. As I said the bulk of the RR designed system is fine. The exhaust is ok from the Y back. With reservations about the first box. The manifolds are just to differcult to sort out. So any alterations will be on back foot and at best 2% improvement. However engine response is what I am after. This makes engines seem more powerful than they actually are. Besides I don't drive flat out so extra power is wasted because its already there just press the pedal more. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1617 Registered: 6-2009 |
I'd say that quicker, less messy, less costly, and easier to deal with are all pluses (and that applies beyond spin-on oil filters). It has been my observation that ready availability of parts (or the lack thereof) is a very strong predictor of whether certain maintenance tasks will be carried out versus deferred. With regard to oil filters and other common service items, having to order parts from far flung niche providers rather than being able to "run down to the parts store" and get what's needed almost always leads to deferral of routine maintenance. That's been one of the primary motivations for my effort to find "off the shelf" equivalents for myriad parts for the SY series cars. Anything that makes maintenance easier to carry out and/or gives extended intervals for maintenance people commonly avoid are only positive in my view. Brian | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 3225 Registered: 4-2003 |
Sham that I seem to have trodden on the cat's tail about filters. Consider this. On a T One the filter comes off without any oil spillage. After a quick clean of the vessel it goes back on in minutes. On, for example, a 1987 Silver Spirit the spin-on device is located with the feed/outlet pointing downwards. If you like messy then this one is for you. Undo it for replacement and old oil pours over the LHF suspension wishbone and onto the drain pan that has just stubbed your right toe. Furthermore the chassis must be lifted so that the suspension is lowered to allow the exit of that messy spin-on thing. All-in there is really nothing in any argument between a cartridge and a cannister in my opinion. They both cost 50 bucks and the grands-prix for changing either must be a dead heat. To advocate a modification either way must be as rewarding as a vegetarian's joy of winning first prize in a pub chicken raffle. | ||
| Christian S. Hansen Experienced User Username: enquiring_mind Post Number: 50 Registered: 4-2015 |
Hmmm...I must be an "equal opportunity mess maker" as changing oil always seems to create a mess, irrespective of whether cartridge or spin on. Worse, if the recycling industry actually bothers to extract oil from the paper medium, I suppose that I should start including the mass of oily paper towels I have been used to clean up the aforementioned messes into the same bag when I surrepticiously throw the remnants into my neighbor's trash bin. (LOL) | ||
| Robert Noel Reddington Grand Master Username: bob_uk Post Number: 452 Registered: 5-2015 |
I like taking the oil filter off my car washing the bits and refitting with a new element. It's not a race. Extra 10 mins. I can buy filters locally. I plan things out. I don't all of sudden decide to change the filter. The odometer tells me in advance when it's due. I will buy a filter and actually fit it a month later. A lot of the consumables such as pipes are all available local to me. For specific RR stuff I go to Silver Lady Services in Winton Bournemouth Dorset. They can get every Shadow part within 48 hours usually. Including used parts. Plus I am a dab hand at making stuff. Such as exhaust systems. Made a brake caliper piston for a down hill racing push bike. Stainless 304. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1622 Registered: 6-2009 |
Christian, I, too, have never been able to change oil without creating some sort of mess that I'd rather not have. The Rolls-Royces, the Buick, and the GMC trucks are the least messy to deal with since the filters are located toward the bottom of the engine and are oriented either horizontally or vertically with the screw-on end pointing up. My 1989 Cadillac is miserable because the oil filter is located near the top of the engine bay and the filter screws in to the pedestal at around a 45-degree angle to the ground. There's no easy way to get the thing out of there without major spillage (which goes directly into the plastic bag I keep poised beneath the filter while I take it off. This is another of those, "The engineers who did this should have been forced to change the oil on this design before it ever made it to production!!," situations. I can't imagine who came up with that particularly perverse configuration. Brian | ||
| michael vass Experienced User Username: mikebentleyturbo2 Post Number: 14 Registered: 7-2015 |
Hi Brian I agree with that sentiment , I have to take my better halfs land rover freelander2 diesel to a garage to change the oil & filter ,the filter is screwed on horizontaly just behind the rad ,only accesable fron underneath on a 4 poster ramp at arms length so the oil runs all down your arm! shouldn't be allowed! oh and it's an element in a plastic holder! Well it's not a Bentley is it lol | ||
| Larry Halpert Prolific User Username: larry_halpert Post Number: 165 Registered: 9-2003 |
And, for those who find $50 expensive for an oil filter, the spin on is the same as a Jaguar V-12. There are much better quality filters than Fram, who puts the Rolls Royce labeling on their filter to then be upcharged to $50 for those that don't notice the money missing. I've used the Bosch 72175 since 2002, (or "0 451 103 278"). It costs about $5.50. Specific info here: Oil Filter Tear Down Oil Filter resulting Recommendations | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1666 Registered: 6-2009 |
Larry, Did you lay in a supply of 72175 way back when? I used to use these, but my "usual suppliers" don't carry that number any longer and Bosch is saying use 72209 instead. The WIX specs based on these two are not the same, but are still similar. As luck would have it that was the same filter that my 1999 Jaguar XJ8L used and that was handy when I had it that I could lay in a supply of a single filter number. The 72209s I have are all marked as being of US manufacture. Brian | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 963 Registered: 5-2012 |
Larry, Wow. "Oil filter resulting recommendations" should be of interest to all of us. Thanks for putting it up. No more Frams for me. Geoff | ||
| Larry Halpert Prolific User Username: larry_halpert Post Number: 166 Registered: 9-2003 |
Glad you liked the site. I've had links to it on my website over the years. Actually, I do have about 4 of the Bosch 72175 filters left that I got a few years ago. Rock Auto lists the 72209WS as the replacement, specifying Bentley, etc for $3.85: Bosch 72209WS I don't know the difference between that and the 72175 | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 964 Registered: 5-2012 |
Hi Larry My reference to not using Frams anymore was in regard to my day car, not the Rolls. This is why the link is so useful - it is relevant to all cars. My SY1 uses a filter bowl so I buy the older cartridge filters. I note on your website there is a reference to H.D.Rogers website where these can be purchased. I bought mine from the following website, which is a useful addition: http://www.post55parts.com/Oil-Filters-for-Silver-Clouds-Bentley-Ss-Silver-Shadows-Chassis-01001-26700_p_47.html In fact I bought 5, a couple of years ago, just in case the filters became difficult to source. Geoff |
