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

[Shawn D.]

Originally Posted by freebeard

I was already backing away from the flow bench. What sensor would you say are used on the dyno. A high-speed recording manometer? Microphones?

The only sensors regularly used during dyno testing are exhaust gas temperature (EGT) and air-to-fuel ratio (AFR), to ensure proper running, not to determine flow. Vacuum is also measured, but to determine "streetability" of a combination, signal to the carburetor or sensors, or if portions of the intake tract are a restriction, but again it's not to determine flow. In any case, the point dyno testing is to determine actual running effects via the resulting calculated torque and horsepower.

Originally Posted by freebeard

I did this to illustrate the end-cuts I proposed. The collector would have three tabs. Convergent angle is not represented. This is thirds of a Christmas wrapping core, not what you were thinking.

That's a goilet, as has been pictured and discussed before in this thread.

Originally Posted by freebeard

What is the relationship between scavenging and anti-reversion. It seems they are at cross purposes.

They are not at cross-purposes. Scavenging is to help ensure the exhaust gases are pulled from the cylinder and anti-reversion is to help ensure the exhaust gases are not pushed back into the cylinder by pressure waves or flow from that cylinder or others.

Originally Posted by oil pan 4

What if its too efficient and vacuums out the cylinder causing more air and fuel to be pulled in?

Originally Posted by RobertISaar

possibility, generally one would design a cam around it with a tiny amount of overlap

Yep, this does happen at higher speeds and excessive overlap is a primary culprit (and at low speeds, the same physical configuration will usually cause some backwards flow into the intake tract). Not only will over-scavenging hurt power and efficiency, the unburnt gases will cause problems with the sensed AFR. One might think this would be sensed as a rich mixture, but due to the excessive oxygen, it is sensed as a lean mixture, causing the ECU to add more fuel.

[Daox]

Yep, I've seen that site and that header before. Unfortunately, it is WAY oversized pipe diameter wise. I think he used 1.5". Its also not nearly long enough IMO. It also uses crush bends instead of mandrel bends.

I agree the O2 sensor location is correct. I'll address that in some final notes after finish up the last step.

I haven't read too much about anti reversion stepped headers. I've always read that if anything you make that small step at the flange of the header.

[Shawn D.]

Originally Posted by Daox

I haven't read too much about anti reversion stepped headers. I've always read that if anything you make that small step at the flange of the header.

The current trend in stepped headers is as Old Tele man's picture shows -- a few inches away from the flange. The purpose is to broaden the power band while keeping the anti-reversion capability of a step.

[Daox]

That is interesting.

I think that it may hurt more than help with regard to this specific design. My reason being that the cross sectional area between a 5/8" and 3/4" primary tube is a very big step. Going from 1 7/8" to 2" isn't nearly the same. If we have material in steps of 1/16" I think it would be more suited to this specific design. Would you guys agree?

[freebeard]

The part of the cardboard tube example I didn't complete (as I didn't have the right sized tube) would be the collector with three tabs bent inward and slipped onto the three primaries. It would have an anti-reversionary effect, would it not?

Fig.3: One of these things is not like t'other.

[oil pan 4]

The whole point of negative supercharging on a gasoline engine is to cram more air and fuel into the engine so you can go faster.

[Xist]

Wahoo! Go faster Daox!

How is the Gen1 Insight designed?

XL1?

[Shawn D.]

Originally Posted by Daox

I think that it may hurt more than help with regard to this specific design. My reason being that the cross sectional area between a 5/8" and 3/4" primary tube is a very big step. Going from 1 7/8" to 2" isn't nearly the same. If we have material in steps of 1/16" I think it would be more suited to this specific design. Would you guys agree?

I agree. For your design intent, it's probably going to be a larger jump than you'd want.

[renault_megane_dci]

Best header for economy would be one who would make use of that wasted exhaust energy and put it back in the engine ...
Like overcoming the vacuum of the engine ...
That would help torque !
Let's say a kind of turbine thing that would compress air on the other side ...
I should patent that idea ...

[serialk11r]

Originally Posted by renault_megane_dci

Best header for economy would be one who would make use of that wasted exhaust energy and put it back in the engine ...
Like overcoming the vacuum of the engine ...
That would help torque !
Let's say a kind of turbine thing that would compress air on the other side ...
I should patent that idea ...

A turbocharger doesn't put energy back into the engine, because the energy returned to the piston on the intake stroke is given back on the compression stroke. They increase peak efficiency a little bit only because the giant increase in torque raises the mechanical efficiency of the engine.

To increase efficiency you have to use less power at the compressor than the turbine generates and send the difference to a battery or the crankshaft.