SAVAGEJIM

I took a rough measurement of my Zen 26cc, and these were the numbers I came up with:
Exhaust duration: 134 degrees
Intake port durations: 90 degrees.

Are these numbers typical for stock gassers?

I know for the much smaller nitro engines, the timing profiles are much much higher: more like
Exhaust: 160-165 degrees
Sleeve intake duration: ~110-115 degrees


Also, for ported and modded gassers, what timing profiles are those raised to?

savagecommander

i think you're a bit off on your measurement- more like 165 for a zen 26, maybe even 170 dependent on if its new or old. and the transfer ports should be around 140. zens make good power at high rpm- you cant do that with anything less than i'd say 150deg

savagecommander

and here's some porting

http://www.modelgasboats.com/Magazin...e_Porting.html

SAVAGEJIM

Thanks for the porting link, that is great! When I get up to speed in running gassers, I might try my hand at modding a gas engine.

As for the timing profile numbers you gave, the exhaust duration is huge, like race grade for a nitro engine. And 140degree seems extremely high

Granted, these measurements I made are very rough. I didnt have a rig to hold it in place nor could I get teh needle to point accurately to the degree wheel. The rig I have is made for nitro engines, and a gasser i easily 6x larger than a nitro engine.

I will therefore have to try to measure again.

As for that 170 & 140 degree durations for gassers, can you link the site where you found that profile? Hopefully they will have measurements for not just teh stock Zen 26cc, but also foer the Zen 23, Zen marines, modded Zens, and even the numerous Chang Yangs (CY).

SAVAGEJIM

I attempted another measurement of my Zen, and my new numbers came up as follows:
Exhaust duration from measurement: 180 degrees
Intake duration from measurement: 100 degrees.

The intake still looks far off, and due to dispairingly different results form my first attempt, I do not trust these result one bit either.
I did another Google search for Zenoah timing profiles by changing my key words and I did find this boat site that went into some performance timing profiles as follows:
Intake: 140/145 degrees
Exhaust: 165/170 degrees
Transfer: 124/126 degrees

Colt4g63

Ive done my fair share of modifying zen 26cc marine engines. I usually set my EX timing depending on application on those engines "remember this is a boat application" at 176-182 ex timing for reference.

I know this isnt a boat or vid section lol.. but heres a vid of a Zen 26 I modfied for a Challenger 43 pro I had. This boat was GPS'd at 60mph quite a few times... The boat trimmed out as light as possible with the engine completly stock on the same pipe got a best of 48MPH and was very light and loose The problem was that at 60MPH+ it would blow over when i trimmed it to run that speed So i trimmed it and proped it down to run 55-58mph on average which is what it was running in this vid. The Challenger 43 Pro isnt the best boat in the world to go fast or race competitivly with. But was a good all around boat to get out and have a ball with thats for sure!


Highlight the whole link and copy paste I dunno why its not posting the link right...
www.abmods.com/videos/Gas Mono CH 43.wmv

SAVAGEJIM

As for my measured intake duration of 100 degrees, does tat sound right? based on what savagecommander said and the gas engine website in which I found those numbers, that 100 degrees looks too small to be correct.

I guess my next project is to make a proper rig so I can measure the timing profile of gas engines correctly. Using a twisty tie as a pointer onto one of the bolts on an improper "collet" between teh flywheel and the degree wheel is a woefully poor way to measure degrees. What I used as a spacer collet was a small roll of masking tape! Even worse,the degree wheel was nt on flat and proper, as it tuned the flywheel, the degree wheel would still wobble.

So, between trying to make sure that stupid twisty tie stays pointing in the proper place, looking at teh degree wheel and turning it such that it wont wobble, as well as watching for teh point when the ports just open was sensory overload for me. I often lost place on the degree wheel and mistook which quadrant I was on. That was why my 1st attempts were way off, by more than 45degrees, I lost place of which quadrant was on the degree wheel.

Colt4g63

I can tell you that on the marine Zen 26s that if you take out the head gasket and just run three bond 1211 sealant as a gasket to raise compression and ALSO raise intake timing... the intake timing falls between 152 and 155. You dont want to go much higher then that.

savagecommander

this is true but you're also lowering the exh timing, and ive seen that hurt power more than a lower intake timing. not to mention the squish band may be too close.

jim are you looking to get more power? or is this an information quest?

(correction-transfers are 125, intake is around 140)

Over_revO

Im sure ABmods know if its good or not to remove the head gasket

Nice vid Adam!

savagecommander

i never said it was i bad idea, i just said it lowers exh timing, which can hurt power. this is true ABmods?

Over_revO

you said the squish was too close, it looked to me you said it was a bad idea, no biggy then
Im not trying to start anything here lol

You are absolutly right it will lower the exhaust timing, but when you are looking for more power, you will also alter the exhaust to be where it need to be for your application...

Thats what i meant...

Colt4g63

Yes it does lower EX timing but it raises intake timing and adds compression. And the squish isnt too close on a zen marine engine by just dropping the jug down with no gasket... we have actually had the cylinders milled even more for MORE compression You just have to move the ports to your desired timing profiles. Which if your fully modifying an engine your doing this anyways

SAVAGEJIM

For right now, it i an information quest, more or less to absorb as much as possible before I even dare try to do it myself.

Right now, seeking the timing profile numbers, both stock, and modded durations.

Next is to learn the processes of the mods commonly done and which ones work best.

After that, I want to learn of all the pitfalls and the do-nots and memorize those like gospel. Everyone posts of their successes, but there is very little info on the all the failures that everyone commits.
Knowing the numbers of the timing profiles to shoot for and the processes and specific mods are important, but I personally find the what-not-to-do the most important info. This was the approach I took when learning to mod nitro engines, then I practiced, practiced, and practiced some more on worn out sleeves and junk engine blocks until I developed a good feel.

This is the same approach I want to take in modding gassers. And before I attempt to mod an engine I intend to run, I want to practice on junk engines. I guess I better start hoarding broken down weed-eaters, leaf blowers, chain saws and such.

Colt4g63

Jim I can tell you from my experience with the gassers that you dont want to take too much material away in the transfer ports while trying to do "flow mods" as its commonly called I have deffinatly went to far in the past when working on my modifications and lost power due to hogging it out too much in that area. You will have a blast diggin in there and working on these gassers. There alot of fun and pretty cheap too!! Heck modifying any engine is fun to me lol

SAVAGEJIM

It definitely looks like there is much more room to reach around in the cylinder, but still trying to reach into teh lat port recesses would be a challenge for me. I guess I should get like a dental flexi-cord and wand for the cutting stones and bits!