Bending an M40

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Ryan Blake
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Bending an M40

Post by Ryan Blake » Mon Nov 10, 2014 2:33 am

Hello,

I am contemplating building an M40 powered go kart (possibly 2 engines on it :D ), and have been thinking over the possibility of augmenting the intakes to get a little extra thrust (I am estimating I would get an extra 10lb at least, if I do everything right :D - or is that overstating it a bit?). The biggest problem with this is fitting the augmenters on the engine. This has been discussed in another topic viewtopic.php?f=3&t=6066&p=74774#p74774, but there wasn't really any conclusion that I could see there.

Any way, after thinking on this for a while, I came upon a possible solution, :idea: and decided to float it on this forum and see if it would be worth trying. :D I remembered that I had read that pulse jets can be bent without much, if any, affect on their performance. I thought it might be possible to put an 's' bend in the exhaust straight after the CC, allowing for intake augmenters to centre on the intakes. The size of the M40's exhaust makes this easy, as I could just use standard 2 3/4" exhaust bends. This would also shorten the overall length of the engine slightly, making it easier to fit on the kart. :D I have attached a 3D I drew of it to illustrate the idea a little better. :wink:

Also, I have joined the augmenters to allow them to centre on the standard 75 degree intakes, but I also wondered about opening up that angle a little more, say 90 degrees, to separate the augmenters fully. Would this make the augmenters work better, or would it affect the performance of the engine?

I would be glad of any further ideas anyone has. :)
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M40 bent.jpg

metiz
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Re: Bending an M40

Post by metiz » Mon Nov 10, 2014 3:38 pm

Hi Ryan,

Don't make any bends in the exhaust! it isn't going to like that! If you want to augment the engine "easily", try building it with 1 intake (same length, twice the volume (so not twice the diameter) and then use an M500 style ejector (it blends with the exhaust somewhat)
Last edited by metiz on Mon Nov 10, 2014 8:20 pm, edited 1 time in total.
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Ryan Blake
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Re: Bending an M40

Post by Ryan Blake » Mon Nov 10, 2014 7:53 pm

Thanks Metiz,

That is exactly why I floated the idea here before just rushing into it like I normally do. :lol:

It is just that I had noticed the picture of a lockwood with quite a few bends on the Valveless page of this website (attached), where Bruno says that "pulsejets do not appear to be greatly affected by bends in their ducts", and thought that it would work the same. Or would a lockwood be more suited to bending as it already has a bend in the exhaust?

With making just one intake, would I be able to make the intake a little further off the exhaust by extending the angled part of the intake, but keeping the centreline measurement the same, or would that not work? It would just allow the augmenter to fit easier.
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metiz
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Re: Bending an M40

Post by metiz » Mon Nov 10, 2014 8:24 pm

Lockwoods are more suitable for bends, yes. Chinese engines don't like it, and highly tuned engines (don't want to blow my own horn here) hate it. They'll run like shit or not at all.

If you want more room for the ejector, try angeling the entire intake upwards. It's horizontal now relative to the exhaust. Don't mess with any of the lengths.

top picture is the original, bottom picture is the modified version. Keep the red line in the top picture the same length.
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Ryan Blake
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Re: Bending an M40

Post by Ryan Blake » Mon Nov 10, 2014 8:32 pm

metiz wrote:Hi Ryan,

Don't make any bends in the exhaust! it isn't going to like that! If you want to augment the engine "easily", try building it with 1 intake (same length, twice the volume (so not twice the diameter) and then use an M500 style ejector (it blends with the exhaust somewhat)
Thanks again,

With making just one intake, this won't affect performance significantly? What are the actual benefits of 2 intakes?

metiz
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Re: Bending an M40

Post by metiz » Mon Nov 10, 2014 10:18 pm

Better mixing of air and fuel, so a dual intake engine is a bit more efficient. A single intake engine is easier to start and even a bit more powerfull, but it will consume more fuel doing so. (but the thrust/ TSFC won't differ hugely)
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