Talk Morgan Forums Morgan Sports Cars Maintenance & Servicing Air Intake improvements

Concerning the S1, some of the cars - including mine - came without the trumpet that aligns with the inverted louvres. So my air intake is directly over the exhaust manifold, wich i dislike quite a bit. I have spoken to MMC and also the manufacturer of the trumpet, but the part is no longer available. Now, Dave W on this forum has stated that the cars without trumpet seemed to rum better than the cars with a trumpet. How sure is this, and what could be the explanation? Anyhow, I would like to get more cold air in or at least not the hot air from the manifold - anyone with an idea of how this could be done? And would I really notice a difference.....

Robbie,
I did see a car at Mog18 in the as driven part of the concourse that supposedly raced & didn't have the trumpet.
I would come over & we could make say a papermache mould or 3D scan it but Bergen is a bit far.

The fibreglass on mine also needed repairing & I was wondering if a metal unit would be better pulling air in from above the rad.

The reason is supposed to be because the airflow along the bonnet is turbulent. I've never run mine without the trumpet, but if I didnt have one, Id be tempted to take the air from above the radiator.

I wonder if worrying about cold air intake is necessary now a days. I know it was back in the Carb days, but now We have EFI Computers that measure the temp of the air and with other inputs compute the optimum fuel/air mixture. As I have been reading here I was becoming more concerned about cool air. My New EFI gets the air in the same place as My carb did. Probably the hottest point in the engine compartment. So I started looking thru catalogs and measuring for space to remedy this seemingly important problem. Than I put on My "Boy Scientist" brain and thought "What For". I now have a computer to do this for Me.

Whats wrong with My 89 year old brain???

Button, you are right that a modern EFI always can balance air and fuel. But if the air is very hot it will dose less fuel to keep the balance of the mixture so the result means less power. If the air is colder the EFI will also keep the same balance but it will deliver more fuel to do so and you have more power. As far as I know, this applies at least to the partial load range. For full throttle one should adjust the ECU to the air volume and temperature.
I am only an interested layman and other TM members can explain this topic much better but in one point I am very sure, your your brain works totally very well and it is in best order:)

JohnV6, you would be more than welcome to a visit in Bergen, but I get your point. So I am also toying with the idea of air from above the rad...

DaveW, what you are saying is that the trumpet seemed to be a nice idea, but not so nice in real life because the turbulence along the bonnet prevented the theoretical entrance of air through the louvres, correct? So plenty of hot air from above the manifold is actually better than restricted cold air from the louvres?
I have a barbeque thermometer with a wireless display. Toying with the idea of taping the sensor to the air inlet and have the display in the car while I am driving to see what is really going on - with and without John Taylors bonnet latch extensions etc.

Robbie,
we visited this year for a few hours on a cruise & it didn't rain. We loved the place & the roads must be epic in Norway.
John

Button,
it is to do with what is called the stoichiometric mix. That is the ratio of fuel to air to get the biggest bang for your buck.
If the air is hot it is less dense and has fewer O2 molecule per cylinder full on the inlet stroke. So you need less fuel to get the right mix but you also get less power on ignition.
If the air is colder it is denser so more O2 molecules & so more fuel can be added per cylinder & thus more power.
Of course you can also make the air or air fuel mix denser by compressing it with a turbo or a supercharger & ideally an intercooler.

The air will be turbulent across the bonnet (with a Reynolds number of over 2000) but that is why the louvres on the Roadster face forward to help the air flow in under pressure of driving forward rather that trying to suck in from a low pressure eddy zone if the louvres face backward. The traditional louvres are there to vent air out not in from the engine bay & the eddy will help suck it out.

Hope that helps.
John

There's a film on You Tube somewhere which shows a tufted bonnet being driven. Down each side, the airflow is chaotic.

I suspect the the trumpet and reverse louvres were adopted as a sensible idea which was never tested.

I tested the air temperatures on my Plus8 by fitting my OBD meter and going for a run.
I measured incoming air temp.
Ambient air.....15degC
Incoming air....35degC and still rising slowly.
The intake is at rear of the engine pointing generally towards the side louvres but a gap back. The exhaust manifold is below. I used a thermometer once to measure the surface temp of the polished stainless filter box..48degC!
Basically, cold air is denser than warm. The ECU senses this and adds more fuel to match this so a small power increase is obtained. The explosion in the cylinder with denser cold air is a bit more powerful. Think of the principle of a turbo or supercharger supplying more air and how an intercooler works.