Lycoming engine guru help needed.

[RetiredRacer]

I have a 0-235 C2C narrow deck 6.7 to 1 compression ratio engine. All the narrow deck Lycomings seem to have low comp pistons. Is there a reason for this as I would like to fit some 9.7 to 1 pistons.

bob

[F1Boss]

Hey Bob:

I cannot say about the 235s, but the narrow deck 320s use cyl flange plates when going from 7:1 to 8.5 - might be the same with the 235? Might talk to Lycon or Barrett about this mod.

BTW the narrow deck cases are used when building up a higher HP 540s as the case is stronger than the wide deck case. Could apply to your engine too - check it out.

Also: there is an STC to raise the compression on the 235 - get a copy & see what they do. No sense in re-inventing the wheel....

Report back with what you have learned, please!

Carry on
Mark

[RV10inOz]

Given you are operating on the RAA register are there any HP/MTOW or other formula that need to be considered here? I just know folk will be watching anything you do carefully as you are right on the limits of the rule book. Just keep this in mind.

Other thing to consider is you might find fuel is limiting, you could run PULP in your current engine. Maybe even ordinary ULP, so having to run AVGAS all the time might not be as attractive.

Having talked at length with our mutual engine guru man, he tells me that the modifications to the Rotec and a blade in the airflow have evened up the distribution. I would love to have a look at the performance and EMS data some day soon to see what has been achieved.

DB

[jrs14855]

If you can track down the Sport Aviation article about Gary Hertzlers Varieze, I think he is running a C model engine with lots of performance mods.

[RetiredRacer]

Here is a reply we got from a retired Lycoming employee.

[quote] I hate to ruin someone's fun, but I would never put these high compression pistons in an O-235-C model. The high comp. version of the O-235 was the O-235-L and N series and was designed to run the Hi Comp. pistons.

Maybe this advice will keep someone from getting hurt, even though my advice may hurt their feelings a bit.]

Don't worry David, I spent so much time getting the weight down, (I'm not going to stuff up now. The extra GG's were going to cost us .4 kg (1 lb), by the RAA formula (But we won't be going ahead with that now). Plus the blade etc. And I had worked it out, we could also fit the pants and fairings (with hardware etc), and still be just legal.

Bob

[flyingriki]

Maybe you'd find good advice here:
http://groups.yahoo.com/group/lycomi...guid=416751750

[RV10inOz]

Gooday Bob,

That is great news about the pants and fairings....will make a big difference to your speeds and cooling.

I am keen to see you and your machine for a quick fly some time soon!

[RetiredRacer]

Originally Posted by RV10inOz

Gooday Bob,
I am keen to see you and your machine for a quick fly some time soon!

Our Air Chalet/Hanger is taking up most of our time at the moment Dave. But as soon as I get a break, I'll duck over.

Bob