rcbobp

I have a Dave Patrick Ultimate with a Webra 1.20. I've never been totally happy with the Webra's performance. Not very consistent...usually runs a little sluggish. Due to an unfortunate incident involving gravity and my late, great Super Chipmunk, I now have a spare O.S. 1.08. The OS ran great and provided the Chipmunk with superb power. Any thoughts on whether this would be a good substitute on the Ultimate?

Hobbsy

My Feedback: (102)

The Webra 1.20 is the equivalent of a Swiss watch when it comes to running smoothly, you must not have it set correctly.

rcbobp

I do have the same engine in a Super Stearman, and it works fine. Perhaps I hit upon some Swiss Cheese, because after 3 years of adjusting, and having more experienced people than I trying to adjust it, I can't seem to get it running properly on a consistent basis. Sorry, but I guess even Webra isn't perfect.

bdtsr

My Feedback: (5)

I have several Webra motors including the 1.20. I also have many OS's inlcuding two OS 1.08s. Power wise they are about the same. Both are great running motors. The OS 1.08 does not like small chamber mufflers as they tend to run hot and quit. The Webra 1.20 like good fuel draw and short fuel lines and/or a pump. Both turn 15X6 and 16X6 props with no problem. I have not had good luck mounting either one inverted.

Hobbsy

My Feedback: (102)

It also likes 5% nitro max.

Flyer95

My Feedback: (1)

I do not have the Webra120 but I do have the OS108 and this engine is wonderfull. OS108 has everything one could ask for when it comes to twostroke engines and burns any fuel from 5-20% nitro with no problem. The engine becomes even more powerfull if you use a quiet pipe and a Perry VP-30 pump/regulator. Thats my setup with a OS-F glowplug, works great!

Julian537

My Feedback: (9)

What fuel are you using in the Webra 1.20?

rcbobp

I've used both 10% and 15%.

bob27s

My Feedback: (19)

I have found that both the OS108 and Webra 120 engines are excellent engines. I still fly a 20 year old 1.08.

Performance edge would go to the Webra, but only by a bit.

One thing on the Webra - if you are using an aftermarket muffler the engine NEEDS good backpressure and stable muffler pressue to the fuel tank to run well. Some pitts type scale exhauts are a bit too large, low back pressure, and the engine will struggle to run consistantly. Something to consider. If you have a twin-tube exhaust, try a little experiment block off one side (temporarily) and see if the engine responds favorably.

rcbobp

I tried it and it really didn't help much. I'm running a Webra 1.20 on my Super Stearman with a Bisson Pitts muffler, no block, and it runs fine. Could be I have a less than stellar performer. Heck, even the best of them have a bad day once in a while.

bdtsr

My Feedback: (5)

I run 15% in pretty much everything except Moki's. How much time is on your 1.20? Could be that it's just not broken in yet. Try 5% fuel as Hobbsy said. What kind of prop and numbers are you getting? What type of carb is it, rotating barrel or slide type?

DarZeelon

Quote:

ORIGINAL: Hobbsy

It also likes 5% nitro max.

RC-Bop,


I fully agree and endorse Dave's words.

If your Webra 1.20 is broken-in properly, running too much nitro in it makes it misbehave...


Glow engines are originally designed to run with a methanol/oil mix... US costs and availability made higher nitro fuels more popular there, but European made engines that were not 'Americanized', still need no-to-low nitro, or to be 'decompressed', to run well on 15% nitro.

Sport_Pilot

It could be your Webra has shims added under the head to allow higher nitro. Or at some time Webra has made that engine with a lower compression ratio.

DarZeelon

Quote:

ORIGINAL: Sport_Pilot

It could be your Webra has shims added under the head to allow higher nitro...

Hugh,


Adding head shims to reduce the C/R is the lesser of the two solutions...

The squish clearance is an important attribute in any engine, which among other properties determines how it runs and the power it makes.
Adding head shims increases the squish clearance, making the engine less tolerant to higher compression ratios...

So, to adjust for higher nitro, you will need to reduce compression, by more than you would if you opt for a 'nitro head' that simply has a slightly larger 'bowl', with the same squish clearance.

djlyon

I have 3 Webra 120s. Running them 15% nitro, misbehave is an understatement.

Denis

Hobbsy

My Feedback: (102)

Dennis, you think the Webra 1.20 gets contrary on 15% nitro, you should try it in a SuperTigre 3000, no fun at all.

Sport_Pilot

How does that make the existing Webra on the Stearman not have shims? I never said it was or was not the best solution. However, it would be a lot cheaper than buying a low compression head, if such a thing even exists.

djlyon

The ST 2300 can turn ugly on 15% also even though the instructions say 15% is OK. I don't try to run any of my 2 cycle engines in this size range or bigger on more than 5% intentionally. It's just counterproductive.

Denis

bdtsr

My Feedback: (5)

I have two ST 2500's and one 2000. All run 15%. One 2500 turns a Mezjlik 18X8 at 8900. Was always tearing up gears in the Hitec 605 servos from pushing my Sig Cap too hard. Some like more nitro, some like less. Experiment until you find what YOUR engine likes best.

jaka

Hi!
Isn't it so that all Webras are made to run on 0-5% nitro? At least the Webra GT .40 I have run in Q-500 pylon here in Sweden are such good engines on just 0% nitro.
No running in is needed with modern ABC, ABN and AAC engines!! They throttle perfectly even from the start...provided you run the right fuel.

rcbobp

This is one of the things I like about the hobby. Ask 3 people a question and get 4 opinions . I'll try messing with my nitro content and see what happens. I will say this...the engine that gives me the problems has almost no compression when cold, but I'm told that's to be expected of the Webra. Is this so?

djlyon

The Webra 120 uses a dykes ring. This will show very little compression when turned over by hand. The ring is a low tension ring and relies on combustion pressure to seal.

Denis

bdtsr

My Feedback: (5)

My 1.20 has good compression (just had it in my hands) maybe not as much as an ABC but it does have a distinct compression stoke. My Speed .61, Blackhead .61 and Speed 40 are flawless on 15% nitro.