V8 Rimmer sports exhaust

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G

Graham A

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53
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Kent, The Garden Of England
I'm about to transfer a stainless exhaust with tubular headers from one V8 to another.

Is it worth replacing the large middle box with a straight through pipe to release a few more horses, or will it bugger up back pressure and ruin things?

I like the idea of a more fruity V8 sound too!

Any thoughts gents?
 
i have\had a rimmer system on my classic and had problems with it leaking in places due to the poor quality of it. It ended up being replaced under warranty and i removed the centre-box and had a straight through pipe and it sounded great with my 3.9 engine, but when I put my 4.6 in, it was ridiculously loud!! I have now put a small centre box in from a company in nuneaton, I think they were called custom chrome.

If you have a 3.5 or 3.9, remove the centre box and go for the straight through pipe, but try and check all welds for leaks before you fit it all if you can, mine was full of them and the brand new replacement didn't look much better to be honest...
 
MOT testers manual Section 7.1. Reasons for rejection, item 4.

4. A silencer in such condition, or of such a type, that the noise emitted from the vehicle is clearly unreasonably above the level expected from a similar vehicle with a standard silencer in average condition.
 
STOP, there is an easier way.

The one thing of use the clown of a mechanic who fitted my rimmers exhaust did right was show me that there is s simple blanking plug in the middle of the center box which is is only tacked in and directs the exhaust through the packing in the box.

All you need is a peice of pipe or bar about 700mm long and a hammer and you can just punch the plug out. I have found this gives you just the right ammount of v8 noise but doesnt drive you mad on a longer a trip
 
Does this 'remove centre box' theory apply to standard systems? I ran a 3.5efi with no rear box (after it rusted & fell off as usual) & just used a piece of plain pipe which made the 'waffle' more noticeable. Is it better to delete the main 'box instead & is there any detrimental effect on emmissions?
 
In regards to the original post, the back pressure argument is silly, you don't want back pressure as it slows the speed at which the gasses escape, however what you do want is the gasses to stay hot on the way out. Big fart cannons allow the gasses to cool which makes it less dense and slows down flow, hot gasses stay dense which speeds up the flow. By having high flow you create a vacuum on the way out of the engine, this allows the cylinder to completely empty of exhaust gasses and starts sucking in clean air.

norseman said:
Does this 'remove centre box' theory apply to standard systems? I ran a 3.5efi with no rear box (after it rusted & fell off as usual) & just used a piece of plain pipe which made the 'waffle' more noticeable. Is it better to delete the main 'box instead & is there any detrimental effect on emmissions?
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The only part of the exhaust that controls emissions is the cat and only when it switches on, which requires high temperatures. The rest of the boxes are suppressors that lower the db level and refine the tune that comes out of the rear box.
 
Bix said:
In regards to the original post, the back pressure argument is silly, you don't want back pressure as it slows the speed at which the gasses escape, however what you do want is the gasses to stay hot on the way out. Big fart cannons allow the gasses to cool which makes it less dense and slows down flow, hot gasses stay dense which speeds up the flow. By having high flow you create a vacuum on the way out of the engine, this allows the cylinder to completely empty of exhaust gasses and starts sucking in clean air.



The only part of the exhaust that controls emissions is the cat and only when it switches on, which requires high temperatures. The rest of the boxes are suppressors that lower the db level and refine the tune that comes out of the rear box.
Click to expand...

Hot gases are denser than cool ones. That's a good one, have another think about that please.:D
 
Saint.V8 said:
Well I must have missed that Thermodynamics lecture at Uni.....:D
Click to expand...

Looks like all the jet engines you design actually run backwards Ant. Think this revelation may cause a total re think at Rolls Royce and Pratt and Whitney will be calling a scoping conference as we speak. :D:D
 
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wammers said:
Looks like all the jet engines you design actually run backwards Ant. Think this revelation may cause a total re think at Rolls Royce and Pratt and Whitney will be calling a scoping conference as we speak. :D:D
Click to expand...
I was wondering what I was doing wrong for the last 12 years Tony...!!!

I guess I'll have to speak with the software boys and tell them that the Airbus 'Flex to Temp' input in the FMCU needs to be revised as apparnetly now, when the ambient decreases, we don't need to downrate the take-off thrust settings, we have to increase instead to compensate for the less dense colder less oxygen rich air!!!

Better hop over to Rolls Royce too, and let them know their software is to be revised to take into the allowance of this new information of hot air is denser than cold air so they can can re-write the software to control the N1 Fan max % at different ambient take off temperatures too....

(I only design components for Jet Engines - I haven't progressed up the Design Office that far yet to get my hands on a whole engine as yet - few years to go for that I think!!)
 
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Saint.V8 said:
I was wondering what I was doing wrong for the last 12 years Tony...!!!

I guess I'll have to speak with the software boys and tell them that the Airbus 'Flex to Temp' input in the FMCU needs to be revised as apparnetly now, when the ambient decreases, we don't need to downrate the take-off thrust settings, we have to increase instead to compensate for the less dense colder less oxygen rich air!!!

Better hop over to Rolls Royce too, and let them know their software is to be revised to take into the allowance of this new information of hot air is denser than cold air so they can can re-write the software to control the N1 Fan max % at different ambient take off temperatures too....
Click to expand...

I await with bated breath for his explanation of the liquid gas manufacturing process. :D
 
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Things I've learnt, my memory sucks in general and should actually dig out all of my old notes rather than going from a hazy memory of it. Reading what I put in daylight, I made my skin crawl. Maybe it is a good thing I no longer work in a garage, or a sign I need to get out of IT as it is killing my brain. Easier to do just this:

As discussed earlier, exhaust gas is hot. And we'd like to keep it hot throughout the exhaust system. Why? The answer is simple. Cold air is dense air, and dense air is heavy air. We don't want our engine to be pushing a heavy mass of exhaust gas out of the tailpipe. An extremely large exhaust pipe will cause a slow exhaust flow, which will in turn give the gas plenty of time to cool off en route. Overlarge piping will also allow our exhaust pulses to achieve a higher level of entropy, which will take all of our header tuning and throw it out the window, as pulses will not have the same tendency to line up as they would in a smaller pipe. Coating the entire exhaust system with an insulative material, such as header wrap or a ceramic thermal barrier coating reduces this effect somewhat, but unless you have lots of cash burning a hole in your pocket, is probably not worth the expense on a street driven car.
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