SJ .46

SJ .46
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SJ .46 - 8/13/2007 4:11:48 AM

rlpfly

Posts: 28
Joined: 11/14/2002
From: Wilkesboro, NC, USA
Status: offline

I have a SJ .46 with just a few runs on it.
Is there a Jett .46 that has more power? If so, could I convert my motor.
This motor will be used for a club race, a low idle is not important.

Thanks.

Post #: 1

RE: SJ .46 - 8/13/2007 2:43:47 PM

bob27s

Posts: 4590
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline

Hi,

Thanks for writing....

There is not a different SJ-46 with more power..... its pretty powerful as it exists!

However, tell me more about the plane you wish to race and I can help with prop suggestions and engine setup.

If you will be flying a Q-500 type of aircraft, or something similar, you may want to change the jett-stream muffler. That is primary way to get more rpm and a touch more power for that application.

Jett has the SS muffler available - this is a sport racing muffler (same muffler provided on our SJ-60LX and SS-40 engines), and is tuned for about 1000 rpm higher than the standard muffler. You will want to prop the engine to run upward of 17,500 rpm MINIMUM peak ground rpm when using the SS muffler. You really want 18,000+ rpm ground peak. Props such as the APC 8.75x8W, 8.75x8.25 and 8.8x8.5 should get you into the right power band and work great on a Q-500 aircraft. Also worth trying an 8.5x7.25 or 7.5

Bob

_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to rlpfly)

Post #: 2

RE: SJ .46 - 8/14/2007 3:19:20 AM

rlpfly

Posts: 28
Joined: 11/14/2002
From: Wilkesboro, NC, USA
Status: offline

Hey Bob,
Thanks for the info.
I have sucsessfuly used this engine with our club's previous race plane (40 sized warbird).
This time around the plane is the Sig 4 Star (slow 500).
I thought I had read that there was a head that used the Nelson plug, and a different muffler.

Lee

(in reply to rlpfly)

Post #: 3

RE: SJ .46 - 8/14/2007 2:16:07 PM

bob27s

Posts: 4590
Joined: 4/9/2002
From: Cleveland, OH, USA
Status: offline

Dub does not offer the nelson plug head for the SJ46.... doesnt need it anyway. We only use those on the 428 and QM40 engines because of the rpm involved, and for survivability.

The Nelson plug tends not to transition or idle well... not an issued for these two engines, but not what you want in anything with a carb on it. So its not a standard product.

Sport or SS configuration engines run great on just a standard K&B 1-L or HP plug.

For the 4-Star you may want to stick with the standard jett-stream muffler. Its a big, draggy plane - so the engine will not unload a great deal... and it needs some prop area. Try flying with a standard blade 9x7, 9x8 and then try an APC 10x6 and 10x7..... the 10x7 loads a bit on the ground, so you have to be careful on the needle setting, but it tends to pull very well in the air. Practice.

_____________________________

Bob Brassell
Jett Engineering - Engine Mfg Support Forum Host

(in reply to rlpfly)

Post #: 4

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