Beardy
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 posted on 25/2/14 at 04:13 PM |
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exhaust U bend
Any idea how much power do you lose putting a U bend in an exhaust pipe?
There are plenty of ccurvy exhaust manifolds and no one seems to care, but it is clearly not ideal...
Context is that in middy you have the transverse FWD drivetrain sitting just in front of the rear axle. It would be nice to push some weight
forwards. One option might be to run the exhaust forwards up the sill and the a U bend and double pass the silencer prior to dumping out at the
typical spot just in front of the rear wheel.
Any thoughts as to what this might cost in terms of power on a 200bhp engine?
Assuming mandrel bent 2 1/4inch pipe
thanks
Beardy
cross posted to middy forum
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MikeRJ
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| posted on 25/2/14 at 04:55 PM |
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It would depend entirely on the radius of the bend, very small radius bends (close to the diameter of the pipe) are far more restrictive than longer
radius bends.
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v8kid
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| posted on 25/2/14 at 05:07 PM |
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I had exactly the same problem and never really solved it. My exhaust is wrapped round the rear and it's far from ideal I'd be interested
to see your solution
Cheers
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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43655
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| posted on 25/2/14 at 05:35 PM |
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Not a lot, but wouldn't it be cheaper and easier to use ballast if its the foreward weight you want?
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coyoteboy
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| posted on 25/2/14 at 05:45 PM |
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Hardly enough material pushed forward to make it worth the effort, surely?
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Beardy
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| posted on 25/2/14 at 06:53 PM |
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There's not a lot of `movable' weight in a car. Once you have the engine and people in it you have minor flexibility in headers tanks
etc., but the only real weight you can shift is the battery, tank and the exhaust system.
In something like a Fury/Pheonix/J15 you have the ability to put stuff in the sills, which are low and central, so it makes more sense to pull a 20lb
exhaust and shove it forwards than it does to have it hanging out the back of a Middy. Likewise in a conventional Locost you can push the battery
towards the rear if desired.
I dont want to add weight, but you maybe right - it might more effort than its worth.
cheers
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v8kid
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| posted on 26/2/14 at 09:19 AM |
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Not a lot of weight can have a big effect. remember if the exhaust is behind the rear wheels it is subtracting weight from the front wheels and moving
it to between the wheels shares the weight. About 3% difference in the F/R weight not a lot but it all adds up.
I'm sure I've seen single seater hillclimb cars where the exhaust is enclosed in the sidepods going forwards with the silencer adjacent to
the driver and the exhaust turning back the way. Unfortunately I can't find any pics.
Cheers!
You'd be surprised how quickly the sales people at B&Q try and assist you after ignoring you for the past 15 minutes when you try and start a
chainsaw
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Slimy38
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| posted on 26/2/14 at 09:34 AM |
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Is there any problem with using those silencers that have the entry and exit on the same end? Or do you still have the u bend but it ends up being
inside the silencer?
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Beardy
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| posted on 26/2/14 at 04:39 PM |
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I would envisage welding up a soliencer that is not round, but one that fits the cross sectional shape of the sill and then cutting out the fiberglass
skin so that it is like an old works healey
http://3.bp.blogspot.com/-RhShsPVxack/Tv9C34MWWfI/AAAAAAAAATQ/eKD6bocy9K8/s1600/44079k.jpg
put two perforated pipies through and do a mandrel bent U bend on the front end and exit in the normal place in front of the rear wheels.
Shovng the battery forwards increases the weight by requireing more battery cable to the starter - not much but again it all adds up
The fuel tank is a special case as its a variabel load - so ideally you want that at the c.o.m. of the car so that when it changes it doesnt impact
the weight distribution.
ot sure what else one can move around.
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mcerd1
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| posted on 26/2/14 at 04:55 PM |
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sounds like your exhaust is going to be a balancing act of total weight vs moving the weight - just like everything else 
quote:
Originally posted by Beardy
ot sure what else one can move around.
Dax put the fuel tank under the scuttle in the bike engined rush (very close to the prop too, but with catchers as standard) can't get much more
central than that
depending on the space you've got you can more things like coolant header tank, oil tank (if you've got a dry sump), brake fluid
reservoirs (if they are remote ones)
you might also be able to move the coil / coilpack towards the front of the engine, change the side the alternator is fitted to and so on....
[Edited on 26/2/2014 by mcerd1]
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rdodger
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| posted on 26/2/14 at 04:58 PM |
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Why not have the exhaust running forward and exit behind the front wheel?
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loggyboy
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| posted on 26/2/14 at 05:15 PM |
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Thats what I was about to suggest: seen it before on someone here, in fact I bought the exhaust off them!
[Edited on 26-2-14 by loggyboy]
Mistral Motorsport
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Beardy
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| posted on 26/2/14 at 05:57 PM |
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Can anyone speak from experience on whether this gets smelly in the car?
seems like a great eay to go though...
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