Designing a header for fuel economy (for a Metro G10 1.0L)

[BabyDiesel]

Lol you're welcome Tim! I enjoy bouncing ideas around and trying to help excellent work on deducing the info down to what you need!

That does seem ridiculously small, even for a 1.0!

If you do not mind ordering pipe, I found this site - Order Stainless 316 Tube in Small Quantities at OnlineMetals.com Where you can get 8' of 5/8" OD, 0.495" ID 316/316L tubing for around $80 after shipping and a 10% discount. That would be more appropriately sized for what you need, but it would not be mandrel bent. You would have to find an exhaust shop to do it for you, and I doubt you want to do that.

[darcane]

Originally Posted by BabyDiesel

The math worked like this for me - A 1.5" primary SBC Header will have a primary cross section of 1.767". 25% of this would be 1.325". Since there is a greater focus on low-end, I believe Tim could go slightly smaller. A 1.25" primary gives ((0.625" x 0.625")3.14), which equates to a 1.227" cross section, a 30.6% decrease.

So 1.25" seems to be the front runner unless there is some specific exhaust information that we are missing...

Edit: Tim posted right before me. Throw all this malarky out the window!

CFM is the key metric. The SBC with 1.5" primaries is likely trying to improve torque at relatively high RPMs. The large displacement and high revs will mean a very high rate of flow.

Designing a header for a small displacement Geo engine running at low RPMs, and part throttle will need a very different design since the CFM is so low. If this header ever gets built, be aware it will significantly restrict high RPM performance.

[Daox]

From: https://en.wikipedia.org/wiki/Suzuki_G_engine#G10

Cylinder bore 73.9 mm (2.91 in)
Piston stroke 77.0 mm (3.03 in)

[freebeard]

Tubing lengths and diameters will be whatever they turn out to be. The three things I'm wondering about are:

• the transition from the square port to the smaller tube
• the collector, when the pulses are 120° apart
• the exhaust tip coupling to the ambient atmosphere

[Gasoline Fumes]

Originally Posted by Daox

Do you know a good way to get in contact with him?

http://www.teamswift.net/3tech/
http://geometroforum.com/pages/3tech/

Also check this out:
http://geometroforum.com/pages/maas
http://geometroforum.com/topic/4569879/1/
I'm not sure if he's still making headers, but there's good info there.

[Gasoline Fumes]

Originally Posted by BabyDiesel

My apologies if I was not clear. CID is Cubic Inch Displacement. The 350 SBC will have 43.75 cubic inches of displacment per cylinder, therefore per primary. The Metro 1.0 has around 33 cubic inches of displacement per cylinder, roughly 25% less.

993 CC = 60.6 CID. Or about 20 CID per cylinder.

[Daox]

Originally Posted by Old Tele man

Using "first-cut" design equations, the equal-length exhaust pipe dimensions are roughly:

• LENGTH (exhaust valve to collector):

2000 RPM ≈ 108" (longer than the 89.2" wheelbase!)
5100 RPM ≈ 42.4"

• DIAMETER (inside pipe):

2000 RPM ≈ 0.77"
5100 RPM ≈ 1.23"

...which looks like 1.0" dia and very L-O-N-G header pipes between the engine and collector.

How did you calculate this?

[Daox]

Ahhh, you deleted your posts, thats why I couldn't see it.

[Ecky]

Daox, have you condsidered a water jacket? You'll need to open up your grille block a little, but it will significantly improve warmup times.

[Daox]

Originally Posted by Ecky

Daox, have you condsidered a water jacket? You'll need to open up your grille block a little, but it will significantly improve warmup times.

That is a great idea, and if I actually go about fabricating the design it will definitely be considered.