smoknrv4

My Feedback: (11)

I hear a lot of guys talking about the jett 90, I'm running an 0.S. 91 FX in my Patriot XL w/ a full tuned pipe, Is a jett 90 a better engine?

Cyclic Hardover

My Feedback: (3)

There is no comparison One thing many forget is that engines like the 91fx, G90, TT 90, Magnum and Jett all have one thing in common and that is they are the same size. Its the design of it that makes one more powerful than the other. A Jett will take it easy.

Now my favorite all around sport engines are the G90's which i will take over the 91fx. They are just as powerful but cost much less. Just my opinion.

bob27s

My Feedback: (19)

Depending on how you set up and prop the OS91, it can put out some decent power... especially with a full pipe. Nothing wrong with that combination, and I have no doubt it will provide outstanding performance in the Pat XL. Although as you will see there have been a few folks who had difficulties with the OS91FX in the past. Others have been very successful. The 91XL I tested was one of the early ones, and it ran ok. I may have just gotten lucky. The ST90 is a very good engine too.

But, for your review and comparison....

The standard SJ-90L side exhaust engine, with the jett-stream muffler, will turn a 12x6 APC above 14,000 rpm (14,300-14,500 rpm is typical after some run time) using 15% sport fuel, at or near sea level. These are ground-peak rpms. Here in Ohio, I get 14,300 easily.

The newly released SJ-90LX is set up for a bit higher rpm on smaller props. Baseline on this is APC 11x8 turning 15,000 rpm, and turns a 10x10 at 16,000 rpm (either of these props work well on the XL). Props like an 11x9 and 11x10 work pretty well on faster aircraft (has to be able to accelerate and unload in the air)

All of this, with easy starting, excellent idle and transition, good bearings, and no pipe/header/coupling to deal with. Use standard 10-15% nitro fuel.

Look up jetpilotrich in the SU-27 thread, and request the link to his SU-27 video. That plane has a standard SJ-90L up front with the 12x6.

I hope this is helpful.

Bob Brassell

hattend

My Feedback: (20)

Bob,

Is a Jett .90L a drop in replacement for any of the other .90 size engines? ISay, I wanted to upgrade to a Jett and I can't remove the engine mount, could I unscrew an engine and drop in a Jett?

Just curious and I can't believe this would be the first time this question came up.

Don

bob27s

My Feedback: (19)

The mounting pattern is a drop-in match to the OS61 and 91. Drive washer spacing is pretty much the same (+/- 1mm)

hattend

My Feedback: (20)

Great! Nice to know. After I pay taxes (ugh), I think I see a Jett in my future. Rich's video and the ability to do a drop-in replacement has convinced me.

Don

fschultz

I have an OS61Fx in a King Kobra. Now that I know a Jett 90 will drop in I think I see a Jett in my future also.

kmtranmd

My Feedback: (71)

I'm about to build a Patriot XL to upgrade my Kangke F20. I have both the ST S90 and OS91FX in near new condition. Suggestion here is for APC 11x8 or 10x10 props right??? I will test the props on these motors but wonder if you guys have done this already. Also, what specific quiet pipe should I look for to match either motor??? How high can I safely rev up the above motors before they burn up??? 14K acceptable??? A little help here can save me some time testing on my own...[:-]

Rudeboy

Hello Bob,

That's great news I would say.
Is the SJ-90LX going to be the same price as the standard 90L? Are they available yet?

And would a standard 90L be "upgradeable" to "X-specs"...? Different muffler perhaps?

bob27s

My Feedback: (19)

Rudeboy.....

The LX engines are about $25 more.

Different sleeve timing, and a different muffler (new muffler is about 1" shorter)

Good question on the upgrade though. I will ask Dub if he tested just them muffler.

The LX project sorta started because of the GP Little Toni. A few guys wanted a real 'fast' setup. The problem was that we had to add about 1/2" of exhaust extensions (with the angled piece) to make the muffler fit properly. This messed up the 'tune length' for the regular muffler... especially if the goal was smaller props/higher rpm. Dub wanted to compensate and recover the lost rpms.

So one thing led to another... we reviewed some ideas Dub and I exchanged a while ago about building a "90SS" for prop-jets... with the result being, along with compensating for the muffler length in the Toni, Dub made it even a bit shorter and bumped the port timing. Trades torque for RPM. Turned out to work very well in the Toni installation......but when he tried the muffler without the extensions, it worked really great.

All I have to do now is find 20 uninterupted shop hrs to finish my friggin plane, so I can get mine in the air and experiment some with props!

RANIERY

My Feedback: (3)

OH MEN I WISH I WOULD'VE KNOWN OF THE NEW JETT90 TWO MONTHS A GO. I JOST BUT A NEW BARSTOCK 90 FOR MY NEW PATRIOT I'M WORKING ON, AND I SPENT THAT MUCH MONEY FOR THE ENGINE ONLY TO FIND OUT HE HAS NEW ONE AND BETTER ONE [&o]. IT ONLY HAS A COUPLE OF TANKS FOR BREAK IN. (THE PLANE IS NO EVEN READY JET. I WANT THOSE NEW RPM[:@]

HaveBlue

that new 90xl sounds like just the ticket for my juno hornet..now off to see how I can raise the funds!!!

bob27s

My Feedback: (19)

Rainery,

Your BSE will be perfect for the plane. Not to worry If you have seen jetpilotrich's SU-27 video, you will understand what I mean.

On the Patriot either engine will work as well as the other. Quite honestly, the Pat XL is a 'big' ship. Its only going to go so fast with either engine. The standard BSE 90L will carry bigger blades better, and provides more of a prop selection. You can lug it down toward 13,000 rpm without any real worries, which allows the use of a variety of props. An 11x9 or 11x10 after some run time is not out of the question. With the 90LX you must prop it for over 14,000 rpm for it to run best.

Bob

SSAN

Good luck, Bob!

I consider myself lucky if I get an hour of uninterupted times in my model room to built.

smitty9969

My Feedback: (7)

OK Bob,
Going to put you on the spot.
If I wanted the fastest lil toni at the field, which engine should I get.
As soon as you respond to this. I will be emailing Dub..


I feel that need...

Smitty

smitty9969

My Feedback: (7)

P.S.
I'll cut, chop, modify whatever is in the way of installing the engine.. Every other part of the plane is just support for engine anyway


Really feeling that need....

r-c-guy

My Feedback: (37)

Hi,
Maybe consider an OS 91 vrdf fan engine with an 11-9 or 11-8 apc propeller and a full wave pipe.

I am flying these on a Dago Red(EZ) and Lil Toni (GreatPlanes). Better than 22k in the air.

Randy

smitty9969

My Feedback: (7)

Hey Randy,
We already talked.. Already moded my Dago. Awaiting coupler to fly.. Ran the engine and 25% nitro ate thru the last one i had.. I'm using a .65 ducted fan.. Tach at 19 consistently and went to 21 on a short burst.. Running a 10x6 apc.. Cant wait to see if my expectations pans out..

Smitty

r-c-guy

My Feedback: (37)

Fantastic! Sounds fabulous!
If you can get a 91, the it will actually throttle like a pattern engine.

randy

Cyclic Hardover

My Feedback: (3)

OKay, I'll donate "ONE FREE SHOP HOUR" to you. Now you only need 19 more. Common guys reach down deep.

bob27s

My Feedback: (19)

You would want this ...

Jett SJ-90LX with the Lil Toni extension kit

start with an 11x8 prop, gradually move up to an 11x9 and 11x10 prop as you become familiar with the engine.

Nothing Dub sells will turn 22K an 11" or larger prop even with a full pipe. The LX with the muffler as shown will turn the 11x8 well over 15K rpm on the ground, and can turn much higher rpm on smaller props.

Keep the Toni light. Start with the recommended CG, and after you are comfortable with the plane, slide it back maybe another .25".

Bob