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Discussion Starter #1
Thought I would post up a pic of the exhaust manifold on my Sud. DrAlf fitted it and tells me it's an ANSA. Not sure if they made different types as the others I've seen are a different design. This ones a 4-2-1 but with pipes which cross over, the others I've seen cross at the front? Not sure what difference it makes to my little 1350 but it seems quite torquey for it's size, with no flat spots.
 

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the reason for different lenght's in each pipe is so it creates a scavenge effect, which means that every time an exhaust valve opens, its puff of burnt fumes will help draw the next exhaust valve fumes through creating a free flowing system. Hope that makes sense.
 

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The Iresa I have crosses at the front. All the pipes have the same lenght. If possible you should allways try to have the same lenght on all pipes. What you want is to create a underpresure when the exhaust valve is open. By that you make it easier for the cylender to fill when the intake valve is opening. Hope that this makes a little sense. It's really hard to explain in english :)
 

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I believe the crossovers are intended to provide improved scavange effect by pairing the cylinder that is on its exhaust stroke with the one that is on its induction stroke - this creates a train of vacuum pulses that work with the valve timing overlap (where the inlet opens just before the exhaust closes at the start of the induction stroke) which helps to "pull" the air/fuel mixture into the cylinder.

This type of crossover exhaust design can be seen more clearly on multi-cylinder engines. American V8s are a good example - standard engines with a dual-plane crank need a crossover exhaust system to work most effectively, but there's usually no room to cross the manifold pipes and you end up with two separate headers with a balance pipe between the two downpipes. Compare that to a full race GT40 "nest of vipers" exhaust, which has all the crossover pipes on top of the gearbox :eek:

Looks like a really neat exhaust system you have there. That 1350 must be a real screamer :D

Lauren
 

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the reason for different lenght's in each pipe is so it creates a scavenge effect, which means that every time an exhaust valve opens, its puff of burnt fumes will help draw the next exhaust valve fumes through creating a free flowing system. Hope that makes sense.
It makes perfect sense ! It also lets me know that I will never ever be able to calculate the correct lenght to make new exhaust manifolts :lol:
 

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I believe the crossovers are intended to provide improved scavange effect by pairing the cylinder that is on its exhaust stroke with the one that is on its induction stroke - this creates a train of vacuum pulses that work with the valve timing overlap (where the inlet opens just before the exhaust closes at the start of the induction stroke) which helps to "pull" the air/fuel mixture into the cylinder.

This type of crossover exhaust design can be seen more clearly on multi-cylinder engines. American V8s are a good example - standard engines with a dual-plane crank need a crossover exhaust system to work most effectively, but there's usually no room to cross the manifold pipes and you end up with two separate headers with a balance pipe between the two downpipes. Compare that to a full race GT40 "nest of vipers" exhaust, which has all the crossover pipes on top of the gearbox :eek:

Looks like a really neat exhaust system you have there. That 1350 must be a real screamer :D

Lauren
That is exactly what I was trying to say :)
Like i said earlier. If possible you want equal lenght on the pipes to get maximum performens.
 

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Discussion Starter #8
Thanks all, that confirms my thoughts on it. Interesting comments Spacenut re V8's, presumably that is one of the reasons why some V8's ie Ferrari have flat plane cranks, manifolding then can be arranged as for 2 4 cylinder engines?
 

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Hi Bruce,
Yes that is an Ansa exhaust - I know from the welded patch that it is one which I gave/sold to Nick. I had it on my 'Sud Green Cloverleaf but when I lowered the car it was too close to the ground and got whacked - hence the patch which Nick did.
Don't forget we are meeting at the pub in Widdicombe on Monday rather than Kenn.
Cheers,
Mark
 

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Discussion Starter #11
Cheers Mark and 85Sprint, will watch out for speed bumps then! Mark out of interest, how did you find this manifold compared with the standard one?
 

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Used to run the Ansa crossover manifold on my 1.7 Sud Ti. (Coudn't fit 1.7 manifold as I still had inboard brakes).
It was matched to an OMP group N system which used to be sold through Demon Tweeks.
Gave up eventually and fitted a proper 1.5 QV manifold as the car was too low for the Ansa one. It was constantly getting damaged. They definately help breathing but was too restrictive on a uprated 1.7 8V, as was the 1.5 one. Never really got the exhaust sorted.
Sold the engine to a guy who fitted it into his race Sud. Gave the Ti away for nothing. Never seen it again. A227 HLF, silver Ti QV. If it's still alive, will be in the Dundee/Aberdeen area.
 

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I had a manifold that was supposed to be an Ansa and the pipes crossed over much nearer the front, and went from 4-2-1 in very short lengths, compared to the longer lengths on the pic shown here. One is meant to give more torque but the other gives more bhp, if I remember it is the one I had with short lengths that gives the torque advantage according to a tuning book I was sad enough to read.
 

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Hi Steffan,
Your manifold looks pretty similar to the one I had made up by Maniflow (Salisbury, UK) when I was racing. The main difference is that yours is welded at the tube joints while mine was clamped, which allowed the primary and secondary pipe lengths to be adjusted to give different power charactaristics.
Cheers,
Mark
 
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