Just bought a new 230 rc motor and also rebuilt one. What psi compression test numbers should these motors be pulling. Both motors are the same after 45 minutes of break in time
Let me know
Thanks

There is no official technical data from Zenoah except for the Effective Compression Ration at 9.2

The psi can range from as little as 40 to as high as 70 psi but that can be a deceiving due to the ratio of oil you ran and how hot the motor is. I worry more about the percentage of leak down you have in a given time frame and where the is the leak coming from.

If you have a tach you can measure the Max. Power. Normally the data shows at 14,000 rpm is the max, also the Max. Torque is at about 10,000 rpm so if you start to notice a drop off from these numbers then maybe you want to check for leakage or other mech. problems.


Again these numbers are only a guide line due to ambient air, fuel mixture, carb settings, gear ratio, stagger, what fuel you are using.

Bottom line is if the motor is running the with the pack and you feel it has plenty of power then leave it alone. Also make sure your car handling. As a good driving car will make more power for the motor.

Mike
www.willmannracingproducts.com

usually what i go by is , hours on motor. If i notice a big drop in power or RPM readings on track. I take note of how much i've ran the motor, and if im confient that its not the handling killing off all the power. more a less a matter of elimination to find out what the problem is.

we had a friend who wouldn't listen to any advice when he complained of not having any power coming off corners. we kept telling him his setup was the problem. he kept messing with carb and motor tuning. finally the following week we got him to change something on the setup and suddenly he found a bunch of power. same motor same carb tuned the same as it was from the start .

you are correct on the handling issue. For me I like to read the spark plug during testing and after the race to see whats going on inside the motor. If the plug is correct color then i move on to the important issue, and that is handling.

I do believe that both should work together to have a great week of racing.
I hate to have a nice handling car all weekend and by the time the feature starts the motor stumbles because i forgot to check the spark plug for correct fuel mixture or for mech. failure.

Just a thought

Mike
www.willmannracingproducts.com

Compression Testing

Zenoah Does have a specification on compression
Compression (kg/cm2) 8.8 / Psi 125 Standard
(kg/cm2) 7.3 / Psi 103 Low Limit


I did compression tests on 40 or 50 engines and never got readings that good
Zenoah must be using different equipment?.But I did get consistent readings of 75/80 Psi using a gage desiged for small displacement engines and testing at 125 degrees on new engine or re-ring after break-in

When reading are lower that 60 psi I would always find a problem , need a new ring, scratched cylinder , bore over limit ,Plating damaged.

This stuff in very interesting to me I hope someone else will jump in with input
Thanks Bill

All my engine have 100 to 115 running three onces of oil per gallon around a 44 to 1 mix. Oil makes alot of the difference up. Just my 2 cents

All my engine have 100 to 115 running three onces of oil per gallon around a 44 to 1 mix. Oil makes alot of the difference up. Just my 2 cents
Your 100% right Jeff ,it would be interesting to see what the numbers would be at 25/1 ratio that's what the the engine is designed for ? .
Bill Scott

Your 100% right Jeff ,it would be interesting to see what the numbers would be at 25/1 ratio that's what the the engine is designed for ? .
Bill Scott
may not perform at the rpm with a 25 to 1 thow.

The best thing for a motor is to have a fresh ring about every 6 to 8 events. That will keep the motor at it best and keep the ring grove clean.

The best thing for a motor is to have a fresh ring about every 6 to 8 events. That will keep the motor at it best and keep the ring grove clean.
By events do you mean normal race weekends at your local track?

By events do you mean normal race weekends at your local track?
You can get a few more out of one on a local level but I will be doing mine before each QSAC race. Thats around 4 weeks on a engine. But thats me and alot of people run them all year.

I have tried a lot of differant oil mix since i started build the boys karts. (we use the same engines at the 1/4 scale fyi) and the best numbers i get is around 40 to 50:1 on mixture. There has been a lot therories on what mixture to run. Some guys like the heavy mixture because it increase compression however, i find a lot of stuck rings or build up in the piston groove and a lot of carbon build on the top and bottom of the head. Less oil some say gives more fuel to burn and a bigger bang at the plug. i have seen some motors in our class which turns up to 18,000 rpm's use 100:1 ratio. This issue is on going thing that will last for years. I believe what ever you feel good about and how your motor runs then keep the ratio as is. A good quality oil is the key to the mixture and not some hardware oil you find on the shelf.

I would like to hear other idea's on oil mix.

The original question was compression numbers and how it relates too engine condition that what my comments are based on. It looks to my that a good compression gage is a valuable tool for forecasting when and if a new ring or something else is needed you just need to be consistent in your testing procedure.I like 50/1 on mixture Good stuff guys
Bill Scott

Jeff, you say your going to rebuild before each qsac event? You might want to re-think that one. By that time the motor is JUST getting broke in good and l have found that the looser one is (to a point) the better! A tight (newly rebuilt engine) will only have more drag on it and if your running a recently rebuilt motor at the qsac races then hmm, your already behind! :)
I prefer 50:1 mixture. The more oil in the mix, the leaner your engine will run! I agree with Mike that a lot of motors are being run with junk oil and that does nothing to help cleanliness on the inside! I have built a lot of motors and you wouldn't believe the condition they show up here as. Carbon build up is the worse thing that happens, then seal leakage, then a ring not necessarily in that order!
As for compression ration? Keep in mind that zenoah designed these as low compression motors and the first thing guys want to do is raise the compression. There's more to it than just that! To do it right, it would involve internal work which we all know is NOT legal! LOL

Ace

Jeff, you say your going to rebuild before each qsac event? You might want to re-think that one. By that time the motor is JUST getting broke in good and l have found that the looser one is (to a point) the better! A tight (newly rebuilt engine) will only have more drag on it and if your running a recently rebuilt motor at the qsac races then hmm, your already behind! :)
I prefer 50:1 mixture. The more oil in the mix, the leaner your engine will run! I agree with Mike that a lot of motors are being run with junk oil and that does nothing to help cleanliness on the inside! I have built a lot of motors and you wouldn't believe the condition they show up here as. Carbon build up is the worse thing that happens, then seal leakage, then a ring not necessarily in that order!
As for compression ration? Keep in mind that zenoah designed these as low compression motors and the first thing guys want to do is raise the compression. There's more to it than just that! To do it right, it would involve internal work which we all know is NOT legal! LOL

Ace
Ace,
I run my engines on a prop for about 3 hours after installing a new ring. My engines are broke in when they hit the track. I will do mine and they always run great. New rings don't tighten a engine up. Seals, Bearings, and Pistons will tighten one up thow. Maybe you need to think about yours a little more. A ring is the best thing you can do for a engine about every 6 to 8 races.

Jeff I wasn't trying to upset you. The way you worded your post was that you rebuilt it every time you went to a qsac event! Yes you are correct. Seals, bearings, and sometimes pistons, but rarely, will tighten a motor up. A ring is tight once new but now you say you run it on a prop stand for 3 hours which is good to seat it in. You didn't state this the first time so I must have misunderstood!
Oh and as far as mine? They do just fine but I DO go a few steps further! :)
Sorry for the confusion....
Rattler...

They are a lot of unsaid tips that all of us don't just let out. See you at the track.