Aerovee twin plug 044?

[skipnsb]

For a street car: Does anyone have information on the Aerovee normally aspirated engine kit? It is a Type 1 for experimental aircraft, 92bore 82 stroke, with twin plugged 044 heads. I think it is tuned for about 3000 rpm. Would these heads be of interest in building a performance engine? As a low rpm engine I doubt there was any porting but I have not seen them yet.

Anyone know anything about the engine/crank/head/rods parts used in the kit? Obviously the carb will be changed. Thanks in advance.

Skip

[Chip Birks]

If you want twin plug, contact MOFOCO, pretty sure they'll do it to any set of heads. Saves you from having to pay for airplane parts.

[petew]

I looked into this a while back. Here's a kit from a forum member...

http://awesomepowdercoat.com/twin_plug_ignition.html



I had a long conversation with my local car guru/mechanic. His basic verdict was this. On most motors it's a waste of time and energy. A hot, fat spark will get you to the same spot.

The only place where you'd REALLY want them is if you're running really big pistons in inefficient chambers. I guess Harley's and top fuelers are a good examples of that. Then the two plugs can give you a better, more even flame front. But again, it only really helps if the chamber/head has been designed for it (Eg. Alfa Romeo twin spark motors). If not, it can lead to weird flame fronts, turbulence and less power. Airplanes only run them for redundancy (I suspect Porsche race cars were similar). As for the emissions angle, a wasted spark system will do almost the same, without more distributors and coils to run them. Ie. more things to go wrong.

However, a few guys have done them over here and swear by it. Still, none of them posted before and after dyno charts. And I can't think of one modern production engine that still uses them. Alfa stopped in 2009. What does that tell you?

P.s. and we haven't even started talking about the timing/location of the second plug. Apparently that's an element of things too.

[FJCamper]

The Porsche (Carrera Spyder) Type 547 engines had dual distributors and two plugs per cylinder were for redundancy. There were two knobs on the dash to run one or both ignition systems.

The Spyders also had dual electric fuel pumps. All this contributed to endurance racing wins.

[petew]

A part of me is still attracted to the idea. But not with distributors. With a crank and/or cam trigger and ECU, it would be much easier. With the right ECU, you could experiment with a slight advance/retard on the second spark plug to see if it helped.

[onwardtothestars]

The point on an aircraft is redundancy. Nothing to do with performance

[Jadewombat]

Do a search on the engine management forum here for twin plugs, it's been done a few times over there.

[buildabiggerboxer]

Adds weight and complexity...But.... as an aside, i had a refusal on a pair of CARRERA 4 cam motors in the 70s, a 2ltr and a 1600, i turned them down!!!
they were no lightweights as id handled them both and saw their power within reach of T1 motors of the day, i wont say the asking price of the time,
but i know i should have had them both..

[hardrada]

A Cessna 170 on the tarmac running WOT with one mag working will produce about 50 rpm less than if both mags were working.

[petew]

Interesting... serious question though.

Is that because of the....
Head design?
Mag output?
Spark plug output?

I only ask because from what I understand about twin plug setups is they're effective because of all of these things.

[hardrada]

It is there for redundancy. The side effect, more complete burn of the charge.

[petew]

Cessnas run lycoming 6 cylinder engines, right?

[hardrada]

They run 4,6 and 8.

[petew]

Im in California at the moment and went to the Peterson the other day. When I get home I'll post a pic of the 4 cam engine they had on display with the Porsche exhibition.

[farmer]

Hello.
WRT "payback" efficiency the general consensus is that anything less than 94 mm bore is not worth the hazzle. There a "hot fat spark" makes about for the same efficiency. We are talking solely ACVW engines here.
Then last year an old aquaintance of mine finished a Historic rally car with a limited 1600 cc displacement. One of the "free" areas with tuning is ignition, and since he had already done a few twin spark heads for both aviation and street he used it too on this engine. Long story short, this engine pulls 7 hp more with twin spark as opposed to without. Is much more responsive on the throttle especially when "off the cam"

On of the general things the cons forget, so to speak, is that when you use twin spark you can run a good deal higher dynamic compression with the same octane. Meaning that you can build an engine say for 93 us premium fuel if it was to be run with conventional ignition, but you can easily run it on 90 octane with twin plugs and then still get the power it would pull on 93 and then some.

WRT full exploitation of the second plug.
- The Aviation location was/is mostly for security, but still works well, hence the typical 50-100 rpm drop on take off if you turn off one Magneto. But if the full potential of the second plug is to be taken, the plug should face the exhaust valve. Tha´t not an easy task, but doable nevertheless. I forget who took the challenge and worked with the problem. I saw pictures at one time. I even used those pics to get ideas on how to make my own and had my local toolmaker make a program for his 5 axe cnc so we can make it now. We use a 10 x ½" second plug . It does require that 2 pushrod tubes are taken off when you newed to switch plugs, but apart from that it works well.
With this approach there is an easy 12-13 hp and 15-20 Nm torque improvement across the board along with a cooler running and significantly more fuel efficient engine, even on a relatively simple 1914 size. With the aviation location we are talking about 2 hp less, so it is minor at the end of the day.