Magnum 15XLS Carb Modification for SSC

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midair02
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Re: Magnum 15XLS Carb Modification for SSC

Post by midair02 »

Oh yeah, you gotta like this price.

http://www.hobbypeople.net/gallery/210605.asp

210605 210605 Magnum XLS 15 R/C Engine $39.99
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lightning
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Re: Magnum 15XLS Carb Modification for SSC

Post by lightning »

You betcha - got two of 'em! :D
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Blue Note
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Re: Magnum 15XLS Carb Modification for SSC

Post by Blue Note »

midair02 wrote:Guess what I got in the mail.

Image

Image

Image

This came with my new engine. Now to order some inserts.


http://www.hobbypeople.net

280022 S15801X Magnum Carburetor Assembly - XLS 15 w/Insert $23.95

280023 S15869-5.5 Magnum Insert - XLS 15 Std 5.5 (for S15801X) $4.00

280027 Magnum Insert Set - XLS 15 (3.2, 3.8, 4.2, 4.7) $12.99

Glad to see the adapters have made it to the public. I have had good results so far with mine, but the season has yet to really make full testing and tuning possible. I think with the price drop of the Magnum, we'll be seeing more of these on the line, and at legal RPMs.
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Re: Magnum 15XLS Carb Modification for SSC

Post by gsjames »

Will the new adapters fit in the older carbs? It kinda looks like the new carb has a step cutout for the insert to fit into.
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lightning
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Re: Magnum 15XLS Carb Modification for SSC

Post by lightning »

Hmm, the two engines I just got from Hobbypeople don't have carbs that look like that!
Is that just bored out or are there threads in there?
BTW, according to their web-site, the inserts are "On order".
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Re: Magnum 15XLS Carb Modification for SSC

Post by o1moregil »

that carb shure looks diffrent, are they gonna make inserts for the older carbs?
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Re: Magnum 15XLS Carb Modification for SSC

Post by lightning »

o1moregil wrote:that carb shure looks different, are they gonna make inserts for the older carbs?
They offer carb bodies for $11.49. If they offer the new bored out ones for that it may be the way to go.
If they are simply bored (and not threaded) I might just bore out the originals once I know what size the inserts need.
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Re: Magnum 15XLS Carb Modification for SSC

Post by Blue Note »

It seems that my original posting has been stomped with the restructuring of the forum, and I can't edit it, so I'm going to try and repeat it here with the report sent back to Magnum from the prototype testing, pictures, and spreadsheet. Wish me luck...I might need it.

Magnum .15 XLS RPM Testing

The Bench Tests

The trials were performed on five ( 5 ) different engines to to increase validity of the acquired data. The group of engines were run on 5% and 10% Wildcat fuel using the same MAS 8X3 Combat prop and the same O.S. #8 glow plug, with the exception of one engine that was equipped with an O.S. A3 glow plug to confirm the expected performance changes from previous trials. The control stock carb runs used the same new carb for all engines to reduce the variability expected from manufacturing differences or wear.
Based on the results of the bench testing, I have concluded that a properly graduated set of restrictor inserts will allow a gradual and controlled alteration of peak engine RPM. Interestingly, an increase in peak RPM was observed with the 5.5mm and 4.7mm carb inserts over the stock carb, with changes being less dramatic with use of the lower nitro fuel. I suspect that this RPM increase may be due to the finish on the inserts being much smoother than the cast surface of the stock carb allowing less impeded air flow. The 4.2mm insert was about the same as the stock carb with 10% nitro fuel, and provided a bit of a performance drop when using 5% fuel. The 3.8mm and 3.2mm carb restrictor inserts provided useable reduction in peak RPM of each engine, but the difference between the 3.8mm and 3.2mm inserts is too broad for competitive detuning and would require more graduated steps for optimal results. A net reduction of approximately 1000 peak RPM was achieved with the inserts on the bench while maintaining a strong full throttle run. The percentage of deviation also shows a direct correlation to the percentage of nitro in the fuel. A total detuning ability of approximately 1500 RPM should allow control in most conditions, and the “tuning up” inserts may prove beneficial on those rare occasions when the weather forces a drop in your RPM to a touch below the target of 17,500 RPM.
Little attention was payed to the required low end needle adjustments in this series of tests due to time constraints, but I suspect this would be the most logical starting place to address the poor idle of the engines with the smaller inserts in place.

Preliminary Flight Tests

Initial flights were performed with the 3.8mm carb insert and demonstrated sufficient fuel draw throughout the duration of the required flight times, although further flight testing with the other inserts is certainly warranted and planned.

Considerations

The weather conditions during this round of testing was uncommonly neutral for this region and not indicative of the usual weather patterns in the southeast during the competition season. It has been observed that the increased temperatures and humidity levels of the summer months will have a substantial influence on the obtained data, but the relative comparisons should be valid and may apply to other geographic regions.

If the implementation of this carb control system is to be considered as a marketable addition to the Magnum line, and is relatively focused on the needs of the SSC combat and competitive uses of the engine, it may be worth providing a “performance control package “ that may include the modified carb with the series of the restrictor inserts as well as fine thread remote needle valve assembly to prevent shearing off in the event of a collision or impact ( as previously discussed ).

Successful development of these adaptations to the Magnum .15 XLS engine line may also be worth considering with the upcoming .25/.28 XLS as well. With the discontinuation of the O.S. 25FX, many combat pilots have been frantically trying to find the “next” engine to fulfill the needs of “B” class combat. The RCCA has sent a proposal to the AMA to adjust the allowed engine displacement for 2548 and Limited B to .29 and up to .30 for Open B combat. Most competitors will try and run the same engines in multiple classes, and the restrictions from Open B to Limited B and 2548 impose similar obstacles as what is seen with SSC. While some will go through tremendous efforts to maximize the performance of an engine via port polishing, compression changes, etc for Open B, they will have to detune again to be legal for the restricted classes. I know this to be the case for myself, and I will again require a viable method to tune with better precision to meet these restrictions in variable conditions.

In Summary

I am very optimistic with the preliminary results of the new insert reduction system you have constructed. With a little fine tuning and further testing, I feel that the setup would be quite well received by many groups of competitors that may have the need for greater control on the tuning of their engine. I have been impressed with your level of participation and commitment on addressing these issues. As the weather cooperates, I will continue to perform more testing of the system to uncover any issues.
The carb modification has already generated quite a bit of interest among my local competitors, and I'm sure there will be building interest if I am able to campaign next season with a fleet of SSC “legal” Magnums. I'm sure the online combat community will be very interested as well, when the timing is right.
I hope this information helps and gives you adequate feedback on your efforts to this point. If you have any other questions or testing scenarios that would be of benefit, just let me know.

Attachments
XLS 15 Modified carb with insert in place.jpg
XLS 15 Modified carb with insert in place.jpg (150.3 KiB) Viewed 11751 times
Profile of Carb Insert.jpg
Profile of Carb Insert.jpg (138.09 KiB) Viewed 11751 times
Modified XLS 15 Carb.jpg
Modified XLS 15 Carb.jpg (151.7 KiB) Viewed 11751 times
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Re: Magnum 15XLS Carb Modification for SSC

Post by Blue Note »

And here is the rest, with the figures to help predict the changes that can be expected.
Attachments
Magnum Carb Insert Test Data.jpg
Magnum Carb Insert Test Data.jpg (184.3 KiB) Viewed 11751 times
Set of XLS 15 Carb inserts.jpg
Set of XLS 15 Carb inserts.jpg (133.38 KiB) Viewed 11751 times
Showing venturi taper on insert.jpg
Showing venturi taper on insert.jpg (129.47 KiB) Viewed 11751 times
Chris Gunter
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midair02
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Re: Magnum 15XLS Carb Modification for SSC

Post by midair02 »

gsjames wrote:Will the new adapters fit in the older carbs? It kinda looks like the new carb has a step cutout for the insert to fit into.
They do not fit into the older carb.
lightning wrote:Hmm, the two engines I just got from Hobbypeople don't have carbs that look like that!
Is that just bored out or are there threads in there?
BTW, according to their web-site, the inserts are "On order".
The ones I got from Hobbypeople were backordered, so I got some fresh ones. No threads - just a couple of o-rings holding it in.
lightning wrote:
o1moregil wrote:that carb shure looks different, are they gonna make inserts for the older carbs?
They offer carb bodies for $11.49. If they offer the new bored out ones for that it may be the way to go.
If they are simply bored (and not threaded) I might just bore out the originals once I know what size the inserts need.

283028 S15863X Magnum Carburetor Body - XLS 15 w/5.5 Insert (for S15801X) $7.24 (Internet only)
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Air Scharnell
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Re: Magnum 15XLS Carb Modification for SSC

Post by Air Scharnell »

Tell me how well those inserts stay in the carb after a DIRT NAP.

Just another thing too forget at home before a meet!
All the inserts :shock:
Frank S
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