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Jett FIRE 50 (with a question for you engine gurus)

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Jett FIRE 50 (with a question for you engine gurus)

Old 10-25-2002, 03:40 PM
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Default Jett FIRE 50 (with a question for you engine gurus)

These readings are with a MACS quiet tuned pipe, length adjusted for max static rpm for given prop. Sig Champion 15% nitro, 20% oil (half synthetic, half castor)

Shorter header:

APC 7.5 (cut down from 8.75) X 9NN: 20,400

APC 7.5 (cut down from 8.75) X 8NN: 20,700

APC 7.4 X 8.25 carbon fiber: 21,400

The above combinations were used on a Diamond Dust and could only get it up to 150 mph out of a screaming dive.

Longer header:

APC 9X10 sport: 16,700

Question for you engine gurus: is there any engine around the size of a Jett FIRE 50 (12 oz w/o exhaust) that will turn that 9X10 at 20,000 rpm?
Old 10-28-2002, 04:11 PM
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Default Jett FIRE 50 (with a question for you engine gurus)

You might want to look at the Nelson engines. I know their 40 Fire/Fai is supposed to be one bad engine. Here's the specs:

Width: (to outside edges of mounting lugs): 2.00"

Height: (without glow-plug): 3.30"

Weight: AAC - 13.9 oz., ABC - 14.8 oz.

FAI Tuned pipe weight: 2.5 oz.

Effective RPM range: 26,000 to 30,000 RPM

Horsepower: 3.0+ HP

This thing sells for like $450. At that price I would hope it would dust all the competition. You can check it out at www.pspec.com
Or you can call Dave at Performance Specialties and he can tell you all about it. Their number is: 775-265-7523. They also have 2 more engines a little cheaper than this one. If you want to go as fast as possible and money is no object then this may be the engine to have.

Old 11-04-2002, 01:13 AM
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Default nelson

A nelson engine will not turn a 9 inch prop. Currently i am down to 7.2 x8.6 to get it to run right. Best bet may be jett fire 60. 20% more cubes than the 50. Should be close to 20,000 on the 9x10.
Old 11-04-2002, 07:32 PM
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Default Jett FIRE 50 (with a question for you engine gurus)


I will answer these questions again since I've answered similar question's in previous post.

The answer is NO for a .50 size engine's that would turn a 9x10 prop at 20,000 RPM (especially if the engine was tuned with a quiet pipe). Jett engines are the Most Powerful, period, and it won't even do that. I don't mean to discourage you, but I think you better give it up cause you're asking too much. On the alternative side, if you insist on running a 9x10 at high RPM then I would recommend you to call Dub Jett and ask him to modify the timing on his .60L (same casing as a .40) and tuned the engine with a MAC straight pipe (not quiet pipe) for the maximum RPM, and with this, you should be able to get close to the RPM you were looking for.

One other thing is...
The small props (7.4-7.5 inches) you were using to get over 20,000 RPM are not the right prop for the .50 Jett. That engine was not timed for high RPM and will not give you the speed you're looking for because RPM is not high enough for that little prop within that RPM range. If it was timed for high RPM like his Q-40 engine, then you would see 25,000 + RPM on the ground with that little prop. I believe your engine timing is approximately 165 degree exhaust duration vs. a Q-40 engine at 192 degree. Get my point?

My recommendation for you to run your Jett .50 with a MAC straight open pipe and tuned the engine with an 8.8x9.5 and squeeze out as much RPM as you can out of it. With it, you should be able to push your Diamond Dust in the 180+ if not closer to 190 MPH.

Don't waste your time running around in circle. Call Dub Jett, the Master and ask him yourself for all the answer's.


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