Air cooled auto engines

[JoeWScott]

Hi All, Is anyone running an air cooled auto .25-.30 engine in an outrigger? I'm tossing around this idea but am unsure. Machine work & cooling are my two main concerns. It would be going into a Hawk so there is no cowl. That big ole' finned head would be sticking right on up there! Thanks.

JOE

 

[izitbrokeyet?]

Usually the .25-.28 motors are called "outlaw" motors and are buggy motors. The exhaust timing on a buggy motor will be too low for you to turn any appreciable Rs in a rigger. I personally woudn't try to run a buggy head on a rigger either...even if on a decent motor..I'd consider having someone machine a water cooled head for it. The Heat sink heads work backwards since they cool too much in the straights and undercool in the corners when the rigger loads up. Water cooling is much more consistent IMHO.

 

[ken t.]

Hi All, Is anyone running an air cooled auto .25-.30 engine  in an outrigger?  I'm tossing around this idea but am unsure.  Machine work & cooling are my two main concerns.  It would be going into a Hawk so there is no cowl.  That big ole' finned head would be sticking right on up there! Thanks.JOE

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I have been struggling with the same situation. I wanted to try a car motor, i think the onroad versions would be better. The two main problems are the slide carbs and the heads are huge. I personaly think that in a boat you could probably cut the head down a bit. Most of the cooling will be done closest to the bottom portion of the head. A slide carb will work providing your hull has the room to set it up. Mine does not.

I am still juggling this one around the ol noggin.

 

[Brad Christy]

Ken,

Listen to Kevin. There are a couple disadvantages to the air-cooled cylinder head. Like Kevin said, they over-cool when they don't need to (straights) and don't cool enough when you DO need them to (turning). They are also a MAJOR source of aerodynamic drag. Plus, also already pointed out, is the fact that water cooling is more consistant. Consistancy leads to predictability and predictability produces reliability, and, ultimately, more power. If you opt with the car engine, look around and see if someone can make you a water jacket that will fit it, it will be time/money well spent.

Personally, I'd suggest getting one of those MAC21's from Andy Brown. I think it's the best engine, overall, right out of the box, and the price is right.

Thanks. Brad.

Titan Racing Components

BlackJack Hydros

 

[Bob Kensill]

I hate to disagree with Kevin but I have had great luck with my engine. I put a Sirio 27 in my 21 size Eagle SG. I cut half the fins off the head and cut the diameter down too. I put a D&J carb on it and a "long" Andy Brown pipe. I cut down a Nova Rossi flywheel to fit the SG crank. Everything else was stock. I ran it for the first time with 65% Cooper fuel and an Octura 2047 prop with 4.8 inches of pitch. I could drop the boat in the water and it would take right off. My best pass with this setup,at Huntsville,was right at 90mph.

 

[Ian Inverarity]

The water cooling systems are based on velocity pressure, that is the faster the boat goes the higher the water pressure and flow, so wouldnt the same scenario occur, ie more cooling in the straights because of higher speeds? :blink: The only reason I can think of that this may not be the case is rudders drilled on the right would present more pickup area to the oncoming flow, but not all rudders are drilled on the right, and some people dont use rudder pickups. :blink:

Isnt it possible to run higher compression with water cooled heads? This would be the main advantage.

Ian.

 

[izitbrokeyet?]

Hi Bob,

Actually you wouldn't be disagreeing with me if you used the Sirio .27 7-port motor (non pull start) since that one has decent timing.

If memory servs that one is about the only outlaw motor available in a 7port

There are of course some exceptions to the rule if you come across a non-standard motor.

Maybe I should restate that Most Outlaw motors will not work because the timing is too low.

Now if you were to say that you took that sirio to 90mph with 172 on the exhaust..and 120 on the transfers..then I'd be impressed

sounds like you needed about 25krpm for that 4.8" prop to go 90...still impressive though.

Ian,

You actually get much more consistent cooling from water….especially when it’s restricted. You can run higher CRs with water mostly due to the fact that you can put controlled cooling via water right above the combustion chamber rather than have the whole head heat-soaked. The function of Speed VS. Heat loss using restricted water cooling is very tamed compared to an exposed heat sink.

I have never really even considered trying to run any of my converted car motors with Air cooling. The only time I've succsessfully air cooled a motor is on an outboard with lots of natural ((skeg) and spray)

 

[DJT]

Joe

Here is my Hawk with a Dynamite Mach .26. Hope the pictures show. I'll figure this out if it kills me. Don't seem to be able to post pictures at this time, but i'll keep trying.

https://www.intlwaters.com/gallery/displayimage...10032&pos=-2693

https://www.intlwaters.com/gallery/displayimage...10032&pos=-2694

https://www.intlwaters.com/gallery/displayimage...10032&pos=-2692

finally some pictures!

 

[6cuda6]

I think you could probably make any motor work if you really wanted to...gear drive whatever, heck offshore in Europe run diesel power!!!...but i think it would be a real pain to have the carb backwards/pipe out the front etc....

Kevin is it class legal to run a .27 in a .21 class???? I know most of the "Buggy motors are all torq based and the car motors are RPM/power based...porting and timing on the buggy motor is pretty lame by boat standards...

I do realise that these motors are relativaly cheap today and easy to come by....

 

[izitbrokeyet?]

Kevin is it class legal to run a .27 in a .21 class????

no, I suspect it was run in a "C" class ...still very respectable speeds for "C"

just my opinion...but I wouldnt try to run a buggy motor in a rigger and I wouldn't try to use Air cooling in a rigger either....that's just my thinking.

Who knows....maybe some inovative individual will set a record some day using an air cooled pull-start buggy motor purchased for $100 with lots of replacement parts

 

[AndyBrown]

IMPBA "C" class =.22 -.30

I have water jackets that fit all of the Novarossi based .21 and .28. 4- bolt cases Bolts down right on the stock head button.

The buggy engine timing numbers are not that bad. We raced riggers with those low numbers years ago. Pulled big props.....1455's with K&B 3.5's. Buggy motors are reasonably priced. On-road engines are not cheap.

$20 for the water jackets.

 

[Finne]

This is confuseing me.

In a car, you use aircooled engines. the entire car is covered by plastic, wich pritty much stops most air circulation. except for the classes where you are allowed to cut a round hole for airflow. but still, not a very open construction.

Then we have a rigger.

The engine is mounted wide open ontop of the thing. Lots of fresh air. And to make things better there's waterspray.

...yet, the engine is supposed to work good in a car, but get overheated on the boat? :huh:

please explain this to me before I make a mistake with my aircooled engine.

 

[GReeToZ]

This is confuseing me.
In a car, you use aircooled engines. the entire car is covered by plastic, wich pritty much stops most air circulation. except for the classes where you are allowed to cut a round hole for airflow. but still, not a very open construction.

Then we have a rigger.

The engine is mounted wide open ontop of the thing. Lots of fresh air. And to make things better there's waterspray.

...yet, the engine is supposed to work good in a car, but get overheated on the boat? :huh:

please explain this to me before I make a mistake with my aircooled engine.

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i am no expert on this but my 1/8 scale car has a fan driven directly from the engine to cool the engine. even when the car is standing still.. and i also have the rear windows cut out for more air. then again i have never used a aircooled engine in a boat.

and its a bit hard to get water in a car.. well there are r/c cars with radiators etc but its not worth the trouble

 

[Mark]

All my cars always had holes front and back and all my road race cars have the head fully exposed. You can't buy road race bodies any other way. Sedans however are enclosed but if your going to race properly and especially on an oval or velodrome u better cut some holes or scrabbled eggs will be on the menu. Keep in mind also that boats run flat-out non-stop, cars most of the time are on and off and in between even in the velodrome my 1/8 4WD roadcar with Group C body won't run full noise in the turns.

What sort of car has the engine driving a fan for cooling? I've never seen this.

 

[izitbrokeyet?]

Andy's right....I suppose it's how you look at it.... and use the power you got. I know there's no way any of our high reving motors going to pull a 1455.

least not with stock diameter.

 

[ken t.]

I think it's fair to say that not all car engines are going to work well in boats. But it is also fair to say that all boat motors don't work well in boats.

I think it would be a mistake to dismiss them all together.If it wasn't for thinkers and tinkerer's the hobby might not be where it is today. I'm sure that many of the things being done with boats now were only marbles rolling around in someones tin can a few years ago. :unsure:

If the problem is port timing then can't this be adressed with some mod work. It's fun to do anyway so why not.

As far as cooling, don't cars run on tracks with much more turns which means the car slows down quite a bit more hence the need for more cooling fins.Do riggers not corner at very high speeds.

Butch cutting head fins has been done in twostroke motorcycles for many years. It can be done because most of the cooling is done at the lower portion of the fins, and only in extreme cases would it be a problem.

The ff12's and similar boats are using car engines and from what i can tell people are having a ball with them. So why cant the same be true for .21 size boats.

I think the gear drive idea has great potential.

Who knows what kind of interesting results could turn up from experimenting with it.

 

[6cuda6]

This is confuseing me.
In a car, you use aircooled engines. the entire car is covered by plastic, wich pritty much stops most air circulation. except for the classes where you are allowed to cut a round hole for airflow. but still, not a very open construction.

Then we have a rigger.

The engine is mounted wide open ontop of the thing. Lots of fresh air. And to make things better there's waterspray.

...yet, the engine is supposed to work good in a car, but get overheated on the boat? :huh:

please explain this to me before I make a mistake with my aircooled engine.

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The one factor everyone forgets is the CHASSIS!!! It is used as a big heatsink, the engine is bolted to aluminium blocks that attache to the chassis....and beleive me after a 1hr main it's very hot!!! On 1/8 scale the head is usually above the chassis in the open air, but we still try to run a 220 to 260 degree engine temp....

I'm not the most knowledgable guy when it comes to boats [newbie]....it boils down to how competetive you want to be verses how deep your pockets are!!!

The great thing about water cooling is you can get the heat out of the motor fast and control how hot you want the motor to run consistently....

 

[6cuda6]

I will admit that a boat screaming accross the pod at 44000rpm would sound awesome!!!! I think if you were careful with your engine selection as to not pick a motor that was to peeky [norrow powerband] you would make it work....

Has anyone ran a car motor with a gear drive AND a 2 speed trans from a car??? Now that would be thinking outside the box....power in the corners....speed down the straight....A the heck with the water hit the pavement [just kidding]...lol...

 

[Terry Keeley]

I will admit that a boat screaming accross the pod at 44000rpm would sound awesome!!!! I think if you were careful with your engine selection as to not pick a motor that was to peeky [norrow powerband] you would make it work....
Has anyone ran a car motor with a gear drive AND a 2 speed trans from a car??? Now that would be thinking outside the box....power in the corners....speed down the straight....A the heck with the water hit the pavement [just kidding]...lol...

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I think I'd try that if I was running 20 SAW... h34r:

 

[anthony_marquart]

In my FF12 I have a Picco .15 rear exhaust engine. I ran it stock first and got very good results. Over the winter I increased the engine timing. This spring I ended up running a smaller prop and with higher rpms. (no surprise) It's a little faster and gets on the pipe quicker. It's air cooled and I think over cooled. I think when I take some fins off it will reach a better running temp. Of course it's not very hot here yet. I think the air cooled engines have lots of potential in boats.

Even with controlled water flow in a water cooled boat you will see variation in water volume through the head. Increased water pressure = increased water velocity even if you are restricting the flow. Wqter will flow through the restrictor faster if it has higher pressure.