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May 24, 2020, 11:24:13 PM

Digging out stuff from all nooks and crannies

This is a discussion for the topic Digging out stuff from all nooks and crannies on the board Beach Buggy Engine and Exhaust Help.

Author Topic: Digging out stuff from all nooks and crannies  (Read 1035 times)

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Reply #15 on: November 01, 2019, 09:12:34 AM
What if they put a length of pipe coming from where the the heat riser joins back to the exhaust on 1 side only? I think to be effective it would have to rejoin the gas flow after any silencer to avoid back pressure similar to what VW did. If you are having a bespoke system built it may be worth a thought.


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Reply #16 on: November 01, 2019, 11:31:03 AM
VW fitted twin hot spots on later engines guess this was for the weaker running later emissions carburettors where as Rob says when the choke comes off they stalled on initial start up as a single hotspot manifold was still too cold.  The inside of a genuine VW silencer contains a lot of pipe work it is not just an expansion box.

Appreciate the internal bits Keith which is what has raised my interest a notch. I have, or did have, a very hot riser pipe at last engine run which was back last winter post Xmas. Did the usual and caught my hand on the riser trying to get screwdriver to the carb idle screw.  I have never seen a "twin hotspot". Is this simply a doubled up pipe ?


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Reply #17 on: November 01, 2019, 12:18:28 PM
What if they put a length of pipe coming from where the the heat riser joins back to the exhaust on 1 side only? I think to be effective it would have to rejoin the gas flow after any silencer to avoid back pressure similar to what VW did. If you are having a bespoke system built it may be worth a thought.

Flags... all comments appreciated... honestly. I do appreciate that the beetle silencer was not just a box with a baffle inside.
 In my ignorance, some time last year, I paid quite a bit of cash out for stainless bends, straight pipe and collectors. I have a friend who is capable of very neat tig welding. I also paid a fair sum for two expensive Remus silencers. This driven by my preference visually for two "cannon style" exhaust system. As they say "hindsight is a great thing and believe me in my instance it really has become quite a factor. Iva is very variable among examiners in what they approve\dissaprove during examination with instances whereby they station can have two examiners who both have differing interpretations. Wanted to be sure I end up with something acceptable. Never realised what the end cost would be as I "learned along the way".  IVA requires a max of 99db. No problem thought I. Was advised to ensure silencers were "E mark" compliant with certification hence Remus purchase. Silencer end pipe\s have to be of the beaded end if exposed. Remus complies.

Now then... I have a pro quality db meter that has been calibrated and checked yearly for re-certification. (Long story how I come to have this), Simply placing this behind an aircooled engine exposed as it is in a buggy rockets the db count up just from mechanical noise alone. For iva the db meter is placed behind each exhaust outlet at a given distance and at an angle of 45 degrees from the outlet. Fire up a buggy engine, with bike style silencer and place the db meter correctly and you can only dream off 99db.

The pitfall I hit next.... trying to bend stainless pipe as you would on a pipe bender using carbon steel and no matter how careful I was the bend\s came out really crap so bought polished pre-formed.

So to the present..... Mike has come across the db issue with FIA.... They use the same method of checking db. To minimise the additional mechanical noise he mentioned he uses "cheater" pipes. Never heard of this up till this point. Simple beyond belief. Silencer exit pipe cranked at
45 degrees. This then means the iva db meter will be at 45 degrees to a silencer exit pipe by a further 45 degrees and much of the additional mechanical noise becomes as good as null at 2000 rpms.

I passed a comment quite some time back that in my opinion Mikes bespoke exhausts were not expensive and I maintain this based on my experience as written above. Had I talked to Mike before spending money I would now have an exhaust system that I believe would pass latest iva needs and be many hundreds of pounds better off than I now am.   

You are correct also I believe in stating the issue of back pressure. Cobble the two exhaust ports together each side without some equalising of pipe lengths and you have a far from ideal exhaust as I have found out along with some rough running.

This brings back a memory of a long conversation with an early seventies "race engine" builder.  He basically stated that all school kids were taught that for every action there is an opposite and equal reaction. If I undertood him he was describing what I think is covered by the words.. "tuned pipe lengths".
He said imagine one exhaust pulse leaving the exhaust port travelling along the system. A reaction pulse will travel back towards the port. If the returning pulse could be timed to reach the port as the next pulse exited then the 2nd pulse would gain a shove and so on.

Wow... need to put the kettle on now... far too much thinking for me and my heads hurting  ;D ;D ;D







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Reply #18 on: November 01, 2019, 02:13:53 PM
I have a pro quality db meter that has been calibrated and checked yearly for re-certification. (Long story how I come to have this), Simply placing this behind an aircooled engine exposed as it is in a buggy rockets the db count up just from mechanical noise alone. For iva the db meter is placed behind each exhaust outlet at a given distance and at an angle of 45 degrees from the outlet. Fire up a buggy engine, with bike style silencer and place the db meter correctly and you can only dream off 99db.


As someone who set up the Competition car audio scene with a £10K dB meter, and went on to do many exhaust "Sound Off" events over the last couple of decades, (as well as working with Boeing for Richard Branson's 1st class seat noise levels) if I may add some things here.

1) You will NEVER EVER comply with the dB ratings if stood behind the exhaust in its wake

2) If you (or any professional person) tries to measure sound levels in this way, the equipment being used will be damaged. Carbon particles from a car exhaust will clog the microphone and render it useless. 45 degrees is actually problematic, and any decent microphone repair center will be able to back that one up with data for you. We lost many mic's (at £1K each) and learned this the hard way. There is also another reason why it is not measured this way, and you will get that one in a minute.

3) dB (decibel for those not up to speed) readings are also always quoted as a distance at which they are taken. It stands to reason that a sound measurement taken at 20 feet away is not going to be as loud as one taken at a few inches from source. Most lower readings are measured and stated at a distance of between 1 and 5 meters away - I do not know what the IVA states, but 1m is usually the industrial standard.

4) Measurements are usually taken at 90 degrees to the source, and if anyone disagrees with that one, then remind them of the benchmark that is always badly quoted of a jet aircraft - and ask them how they actually measured that one at full throttle whilst in the path of the noise whilst standing one meter away. It certainly would not have been at 45 degrees either !

Getting your IVA inspector to acknowledge this may actually help you pass your noise levels whilst maintaining enough noise to make Buggy ownership a bit more fun. Ever driven an electric car through a tunnel at full tilt? I did recently and was near suicidal at the end of it - how boring.
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Reply #19 on: November 01, 2019, 03:53:31 PM
Has anyone tried solid copper round bar to transfer the heat? We use this as earthing spikes on radio equipment for high power static sites and although not that flexible it can be bent.
It would not get as hot as a well maintained OG setup but would certainly be better than a fully coked 40 plus year old exhaust.
Cut off the old pipes, braze on new flanges on the bar to leave the tip of the bar exposed in the gas flow, drill the centre section of the manifold to an interference fit for the bar and hey presto a steam punk exhaust.


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Reply #20 on: November 01, 2019, 04:08:32 PM
Surely a flow of hot air would work "faster" at heating up the manifold than thermal convection of a solid pipe   :-\
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Reply #21 on: November 01, 2019, 04:42:11 PM
I have a pro quality db meter that has been calibrated and checked yearly for re-certification. (Long story how I come to have this), Simply placing this behind an aircooled engine exposed as it is in a buggy rockets the db count up just from mechanical noise alone. For iva the db meter is placed behind each exhaust outlet at a given distance and at an angle of 45 degrees from the outlet. Fire up a buggy engine, with bike style silencer and place the db meter correctly and you can only dream off 99db.


As someone who set up the Competition car audio scene with a £10K dB meter, and went on to do many exhaust "Sound Off" events over the last couple of decades, (as well as working with Boeing for Richard Branson's 1st class seat noise levels) if I may add some things here.

1) You will NEVER EVER comply with the dB ratings if stood behind the exhaust in its wake

2) If you (or any professional person) tries to measure sound levels in this way, the equipment being used will be damaged. Carbon particles from a car exhaust will clog the microphone and render it useless. 45 degrees is actually problematic, and any decent microphone repair center will be able to back that one up with data for you. We lost many mic's (at £1K each) and learned this the hard way. There is also another reason why it is not measured this way, and you will get that one in a minute.

3) dB (decibel for those not up to speed) readings are also always quoted as a distance at which they are taken. It stands to reason that a sound measurement taken at 20 feet away is not going to be as loud as one taken at a few inches from source. Most lower readings are measured and stated at a distance of between 1 and 5 meters away - I do not know what the IVA states, but 1m is usually the industrial standard.

4) Measurements are usually taken at 90 degrees to the source, and if anyone disagrees with that one, then remind them of the benchmark that is always badly quoted of a jet aircraft - and ask them how they actually measured that one at full throttle whilst in the path of the noise whilst standing one meter away. It certainly would not have been at 45 degrees either !

Getting your IVA inspector to acknowledge this may actually help you pass your noise levels whilst maintaining enough noise to make Buggy ownership a bit more fun. Ever driven an electric car through a tunnel at full tilt? I did recently and was near suicidal at the end of it - how boring.

Yup. Back in my rallying days in the 70s, during scrutineering before the event db readings were taken at 90 degrees to the source and at a certain distance (can't remember but 25/50 yds?).
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Reply #22 on: November 01, 2019, 08:44:54 PM
I do not know what the IVA states, but 1m is usually the industrial standard.

Here's the measurement details from the IVA manual

Quote
Using sound level meter to the manufacturer’s instructions, carry out a stationary noise check.
Position the vehicle within the authorised test area. With the sound meter horizontal, set the microphone height so that it is at the height of the exhaust outlet or 200mm from the ground, whichever is higher.
a. At an angle of 45 degrees to the exhaust outlet in the direction which gives the greatest distance between it and the vehicle contour
b. At a distance of 500mm from the exhaust outlet.
With the vehicle at normal operating temperature, run the engine at 3⁄4 of its ‘maximum power’ speed, and note the sound level reading obtained.
Note 1: Manufacturers drain holes are permitted in silencers
Note 2: The exhaust may have several outlets up to 300mm apart connected to the same silencer. In this instance the microphone must face the outlet closest to the vehicle contour or highest from the ground. In all other cases, separate measurements must be taken for each exhaust outlet; the highest value obtained is the test value.
Note 3: Where the engine maximum power speed is not available, the test may be carried out at 2/3 of engine maximum design speed.

Must have a measured sound level not exceeding 99dBA.


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Reply #23 on: November 01, 2019, 09:04:47 PM
99 dba is not that loud, thinking from memory that is what killed off the Cosworths and other high performance stuff back in time.


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Reply #24 on: November 02, 2019, 03:06:51 AM
Surely a flow of hot air would work "faster" at heating up the manifold than thermal convection of a solid pipe   :-\
Yes it would be a compromise but copper has a very high W/m k which to me and you is how many watts it transfers per meter per kelvin of input. Until it was tried I suppose we will never know.


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Reply #25 on: November 02, 2019, 04:01:00 AM
Another problem could be melting point, what temperature is the exhaust at the heat riser take off? As copper melts at around 1080'c and any restriction in the gas flow would create a hot spot like you see on bends and collectors.


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Reply #26 on: November 02, 2019, 10:25:00 AM
I often thought of running some wire stripped from T+E cable from the exhaust to my washer bottle to defrost it. Bit far apart on a buggy.

That was with my first car when I couldn't afford washer fluid
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Reply #27 on: November 05, 2019, 11:37:10 AM
I do not know what the IVA states, but 1m is usually the industrial standard.

Here's the measurement details from the IVA manual

Quote
Using sound level meter to the manufacturer’s instructions, carry out a stationary noise check.
Position the vehicle within the authorised test area. With the sound meter horizontal, set the microphone height so that it is at the height of the exhaust outlet or 200mm from the ground, whichever is higher.
a. At an angle of 45 degrees to the exhaust outlet in the direction which gives the greatest distance between it and the vehicle contour
b. At a distance of 500mm from the exhaust outlet.
With the vehicle at normal operating temperature, run the engine at 3⁄4 of its ‘maximum power’ speed, and note the sound level reading obtained.
Note 1: Manufacturers drain holes are permitted in silencers
Note 2: The exhaust may have several outlets up to 300mm apart connected to the same silencer. In this instance the microphone must face the outlet closest to the vehicle contour or highest from the ground. In all other cases, separate measurements must be taken for each exhaust outlet; the highest value obtained is the test value.
Note 3: Where the engine maximum power speed is not available, the test may be carried out at 2/3 of engine maximum design speed.

Must have a measured sound level not exceeding 99dBA.


This is 100% correct.    The angle measured at an actual test is 45 degrees from the axis of the silencer outlet. Generally, but very probably not in every single case, 2000 rpms is the speed during actual test. The examiners db meter measures to 1 decimal place so a pass is possible with a meter reading of 99.9 db. If it flicks, even only for a moment & only once, it is a fail. Mike has had issues in the past preparing exhausts for the FIA racing guys and the FIA requirement at test is 45 degrees from silencer outlet.

99db is achievable.... listen to a modern motorbike with a factory standard exhaust sytem. It is only when the knuckleheads scream the revs or blip the throttle does it go way, way above. Quiet exhaust are now a fact of life and this won`t change should we exit the eu.

As I have said before the iva guys are not out to fail you to appease the beaurocrats.. just to make sure you are safe and meet the regs as laid down by the same beaurocrats.   It`s a challenge but I will get there.


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Reply #28 on: November 06, 2019, 09:38:58 AM
With my 1641 and cannons I tested at 3000rpm (3/4 of my rolling road tested max power speed of 4K)
Initially it was coming out at 134dB

I then added baffles and exhaust wadding held onto the baffles with stainless wire.  I managed to get my reading down to 103dB.

I must admit I hate the quietness  :'(

I did this because they were getting noise complaints at my local classic car meet.  It was mainly modified vehicles showing off driving past, but my buggy was singled out by a complainant.


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Reply #29 on: November 06, 2019, 11:33:18 AM
' I did this because they were getting noise complaints at my local classic car meet.  It was mainly modified vehicles showing off driving past, but my buggy was singled out by a complainant. '

That's irritating Gordon and I'm sure deeply unfair. I imagine the complainant didn't know how to describe one of the legion of samey looking tinted windowed, low wheel arched, unbadged modified cars but did 'recognise' an open topped beach buggy in the gathering and that was the limit of their vocabulary.
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