Another item on the engine compartment clean-up, how important are the air horns?

[LeonV]

Your arguing completeness ...

In your attempt to educate or just look smart on the intewebs you can confuse most people.

I don't think anything was confusing, and if it is, then I didn't see anyone (but you) chime in about it. I have no problem clarifying any statements that are not well understood. I'm not arguing completeness, I'm just pointing out that what you said is wrong.

No, what I said was correct. They do that function exactly. However, it is not ALL they do, but they definitely do make the air flow entering the carb less turbulent. I will admit to leaving out the whole tuning the rpm range aspect of it, as that is an intake velocity discussion, which admittedly the air horns do influence. I just did not feel like getting into that.

No, that is incorrect, again. The air flow is not made less turbulent! A rounded inlet decreases flow separation (the vena contracta which you mentioned), not turbulence. If the air flow was made less turbulent then flow separation will be more likely (bad). Even if it did make the airflow a little less turbulent, does that have any effect on engine operation? Nope. Air flow in the intake will always be turbulent, and you really want it to stay that way for fuel atomization purposes.

Also, air horns do not directly increase intake velocity, they increase intake pressure. It is not an intake velocity discussion. Intake velocity is another internet term (like backpressure) that is thrown around all the time with disregard to what it really affects...

Look, you can say what you want and maybe you were inferring something completely different than what your post seems to say, but such a vague statement like "smooths out airflow" is not nearly describing the actual function of the air horn. Shouldn't someone know what the part does before deciding whether to ditch it or not?

Also, it depends on what your definition of proper is I suppose. Datsun though enough of them to integrate them into the stock intake manifold. They were needed then as well. Proper has many meanings depending on who you talk to. If you want your L series to run as Datun intended. You NEED air horns.

All I'm saying is that someone with the right knowledge will be able to make an educated decision. Others will grasp at straws. If the decision in Healey's case involves air horns vs. better filtration, then I think the proper decision is the one that gets you the most torque, power, volumetric efficiency, whatever you want to call it. In his case, it could be a wash and going either way doesn't change things much, whether he uses an air horn with a restrictive filter or no air horn with a less restrictive filter. The gains and losses may cancel each other out, and nothing noticeable happens. So no, he clearly doesn't need an air horn to have a great running car, as he seems to have already found out!

I guess by your logic, if you want you L-series to run as Nissan intended, then you really NEED to be running an air pump and stock exhaust too.

[240260280z]

You don't need horns under the filters, short radius-ed plates will do quite well.

[240260280z]

For the breather on the valve cover top. You can shave it an fill (like you did to the balance tube) and drill a hole in the side of the valve cover next to the fire wall and run a tube from there back to an air filter to draw the poison from the motor at high rpms.

[Arne]

As I understand it, the turbulence from no horn messes up the fuel metering in an SU. Remember that the SU design is velocity-sensing. If the air is swirling around in the mouth of the carb, the pistons (and needles) may rise inconsistently. This affects fuel metering.

[Zedyone_kenobi]

Oh, I get it, you are one of those pick-a-part multi-quote internet forum guys.

Now I understand.

Still, you are very thorough, can't fault you for that.

[LeonV]

You don't need horns under the filters, short radius-ed plates will do quite well.

Bingo, that's exactly what I'm getting at! That radiused plate will diminish entrance losses to the carb, as good as or better than an air horn (depending on air horn geometry). You can use filters that fit and flow with the benefit of a radiused entrance!

As I understand it, the turbulence from no horn messes up the fuel metering in an SU. Remember that the SU design is velocity-sensing. If the air is swirling around in the mouth of the carb, the pistons (and needles) may rise inconsistently. This affects fuel metering.

That's exactly the thoughts I'm trying to avoid. As I've said, the air is already turbulent, regardless of having a horn or not. There will be more entrance losses without a horn but fuel metering will be unaffected, for all intents and purposes. I've had no problem at all with fuel metering when running SUs without horns, along with many others who have done the same (as Mortensen mentioned and Healey realized). Again, an air horn will be beneficial for performance, but because it decreases entrance losses and increases powerband bandwidth. That's it, that's what it does.

Oh, I get it, you are one of those pick-a-part multi-quote internet forum guys.

Now I understand.

Still, you are very thorough, can't fault you for that.