Polishing intake manifolds

Re: Polishing intake manifolds

by Eugene Klimenko » 7 years ago

Eugene Klimenko

12 74 1

Sorry for confusion.

Manifold kit from FLYGAS is out there for sometime now for about $1200.

I did about same thing for $200 with very good results.

After removing intake manifolds I noticed that they are pretty rough on inside. That was original post with question = if there is benefit of polishing them and port match.

Re: Polishing intake manifolds

by Genival Pacheco » 7 years ago

Genival Pacheco

4 87 135

So am I.

But it is an interesting product.

This topic rises the discussion of the crossover pipe again.

Is there anyone that can explain Why this is not standard if it seems to be the solution for the low rpm vibration?

Re: Polishing intake manifolds

by Roger Lee » 7 years ago

Roger Lee

131 5.38k 5.44k

If the engine is setup correctly, engine mounts aren’t old and carbs synced and the ideal rpm is not set excessively low it shouldn’t vibrate.

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Roger Lee
LSRM-A & Rotax Instructor & Rotax IRC
Tucson, AZ Ryan Airfield (KRYN)
520-349-7056 Cell

Re: Polishing intake manifolds

by Eugene Klimenko » 7 years ago

Eugene Klimenko

12 74 1

Here is result of my homework:

- in 4-stroke engine with 4 cylinders only way to have continuous flow = is 4 - to - 1 situation with 1 carburetor feeding 4 ways. Because in any position there will be always one piston is in suction mode.

In Rotax 912 with 2 carbs we have flow inside of this 2 carbs in constantly "stop and go" mode. Creating giant tsunami back and forth waves inside of intake manifolds. Effect of this "stop and go" we feel only at low RPM as vibration. Makes it worse with unbalanced carburetors.

Large diameter balancing tube is creating one large common supply plenum effect = were is more room for this waves to go. As a result at low rpm 1600-1700 feels almost like sitting in small car.

Re: Polishing intake manifolds

by Genival Pacheco » 7 years ago

Genival Pacheco

4 87 135

Thanks Roger

It seems a perfect solution!!
Is there any issue that we are not seeing that explains why it is not standard????