Exhaust manifold design

[Rippthrough]

Yeah if you wana spend 10k on making a one off racing mani for your xud....then carry on

Apart from those we've made for years for our own cars in anything from knocking one up in a lunch hour to a couple of days for the worst ones.....yeah, cost us thousands that....

[Ruan]

Yeah if you wana spend 10k on making a one off racing mani for your xud....then carry on

Apart from those we've made for years for our own cars in anything from knocking one up in a lunch hour to a couple of days for the worst ones.....yeah, cost us thousands that....

Yeah, but unless you heat treat them and spend hours and hours on them, they crack - that's my whole point!

[Rippthrough]

The flange is the easy bit

I bow to your expertise at making exhaust manifolds. You've obviously made many more than me.

[Piggy]

Knocking one up in a lunch hour doesnt constitue a high performance tuned tubular manifold in my eyes...nor can see it lasting long

I was referring to min cost of the racing manifolds you reffered to anyway

[Rippthrough]

Yeah, but unless you heat treat them and spend hours and hours on them, they crack - that's my whole point!

Nope, it's just down to bad design, poor materials or crap welding, there's no heat treating or anything necessary.

[Piggy]

The flange is the easy bit

I bow to your expertise at making exhaust manifolds. You've obviously made many more than me.

Measure up, create cad drawing, send off, pay £30, receive in post in 7-10working days.

Yeah that was tough

[Rippthrough]

Knocking one up in a lunch hour doesnt constitue a high performance tuned tubular manifold in my eyes...nor can see it lasting long

Well, that particular manifold had the engine make 15bhp more than even the manufacturers own race cars, and it did 3 years and it's still perfect.....

[Piggy]

But Ripp', we all dont have your workshop, welder, tools, and experience and expertise

[Rippthrough]

Measure up, create cad drawing, send off, pay £30, receive in post in 7-10working days.

Yeah that was tough

Yep, spend an hour measuring and checking, draw it up, outsource it and wait a week, as opposed to the rest of the manifold where you can make it yourself in a couple of days at the worst, and hour or two if it's not bad.
You were saying?

[Piggy]

But many of us COULD make a log style mani and get same result

[Rippthrough]

But Ripp', we all dont have your workshop, welder, tools, and experience and expertise

And yet you keep telling me I'm wrong?
We don't have much gear, probably not much more than Darren has to hand, he doesn't seem to have any trouble making manifolds either.

[Piggy]

Measure up, create cad drawing, send off, pay £30, receive in post in 7-10working days.

Yeah that was tough

Yep, spend an hour measuring and checking, draw it up, outsource it and wait a week, as opposed to the rest of the manifold where you can make it yourself in a couple of days at the worst, and hour or two if it's not bad.
You were saying?

A couple of DAYS? So its simpler to spend days making a flange than paying £30 for one?
Plus as I said, most of us dont have what you have available to us.

[Rippthrough]

But many of us COULD make a log style mani and get same result

And you still need:

Flange
Tube
Bends/some way to bend it
Welder.


For both designs.
So what's so hard about going for an EL tubular over the log?

[Piggy]

Yeah so for the majority of us making a log type mani would give us all the benefits we needed if not more going on power figures of different engines!

[Rippthrough]

A couple of DAYS? So its simpler to spend days making a flange than paying £30 for one?
Plus as I said, most of us dont have what you have available to us.

For the manifold, not the flange.

The exhaust on the buggy was made with a welder and an angle grinder.
You're telling me most people that are making a log manifold don't have those?

[Ruan]

Pipe bender :/

My point is that I can design it so it won't foul anything, won't crack, perform acceptably well....

And for *ME* cost around the same.

Unless you know someone who'll do all of that on a tubular for less than ~£400

[Piggy]

Well if you wana knock us all up some tuned tubular manis nice n cheap...then I will be first to pay buddy

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Pipe bender :/

My point is that I can design it so it won't foul anything, won't crack, perform acceptably well....

[attachment=12323]

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Space is the other issue to be fair

[Rippthrough]

Yeah so for the majority of us making a log type mani would give us all the benefits we needed if not more going on power figures of different engines!

If you get the tubular tuned right you should be able to pull 6-7% out over a log manifold of similar dimensions, even with a turbo stuck on the end of it and mild cams. That's 10-15bhp for most of the tinkered with diesels that would need one...

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Pipe bender :/

Wasn't used on the buggy, it was reclaimed dairy tube, because it was cheap as f*ck. That manifold probably cost less than your log would and it's f*cking huge

[Piggy]

For petrols, yes, i couldnt agree more...

But go look at power figures for tuned diesels, your R15 making 107bhp per litre with fancy mani vs mazda 2.2 making 204 on a basic design

[Rippthrough]

Apart from the R15 has both air restrictors and a maximum boost limit of 30psi, that Mazda engine is running 55psi and no restrictors....the R15 could double it's horsepower if you designed it without the restrictors in there, and that's being conservative, without even allowing them more boost - it's up at full power by ~3800rpms, then flat lines from there.

[Piggy]

So double it then...around 214bhp per litre...a massive 9-10bhp increase by spending a huge amount more time and money on a manifold

[Rippthrough]

Yes, on 30psi. Instead of 55psi.

Do you not think it significant that even with those limitations in place, and the massive package and aerodynamic restrictions on space in a prototype racer, that they still went with the size and effort to get a tubular manifold in there instead of a log straight back to the turbo?

edit, typo

[Piggy]

You just said 30psi?!

And to double the bhp figure to 1180bhp would need more than 30psi and wouldnt last long I wouldnt think

[Rippthrough]

Typo, and no, it wouldn't need more boost, that's the point, it's already making enough torque to hit that without the limiters.
Two different sets of regulations, you can't directly compare them without trying to make it equivalent - even a years difference between the Audi units makes a massive diffference to bhp/litre as the regs change - what you can do is look at what they've done and why they've done it...and if you look at why the Mazda unit uses that manifold, it'll be damned well obvious, if you think that's an easy and basic design to make you'll get a shock...

[Uberderv]

This is why I mentioned group buying on the flanges. Keeping the cost down is a good start. Long time ago I made this with a £20 Arc welder and a hacksaw.

Took a lot of faffing and quite a long time. I bought the flanges from the U S of A because it was cheaper believe it or not. Its as close to equal length as possible in a shed so its possible without spending loads of dosh.
But for a few HP loss and many hours saved I would go with a log manifold.

[Rippthrough]

I hope you kept it, I keep being told they cost thousands, stick in the for sale section sharpish!

[Piggy]

You can misquote me all day Ripp', I dont care, but in hdi 2.0 or xud9 form a log manifold is going to see you all the way to the limits of the head without all the effort n time spent making such a manifold...such time n effort would be better spent elsewhere

[darrenjlobb]

This thread is hilerious

[Piggy]

Do you not mean to say:

Useful, informative and helpful?

[Rippthrough]

Piggy, the flow limits of the head don't affect the benefits of pulse tuning. You can benfit from pulse tuning on a 36bhp beetle engine, and their heads are terrible.