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Gary's RV7A

Active Member
What is the advantage to having your cylinders flow matched? It's a $500 charge, what performance enhancement do you receive in return? Smoother running engine...
 
I am just a bubba so my viewpoint is subject to correction.

With a carbureted engine, I can sometimes run lean of peak. My EGTs may be closer than not having the cylinders flow matched.

The place I used advertised a power improvement but I cannot verify that.

My guess is that if you are fuel injected this option may be pointless.
 
Ron Lee said:
I am just a bubba so my viewpoint is subject to correction.

My guess is that if you are fuel injected this option may be pointless.
Click to expand...

Im afriad your guess is incorrect.
Flow matching is for fuel injection. Many Many Many archived discussions on it. You can search flow matching, LOP, lean of peak and the like for everything you ever wanted to know on the advantages, performance, how to, etc.
 
There are at least two types of flow matching------injector nozzles, and the ports in the head.

By the use of the phrase "having your cylinders flow matched?" I suspect the OP was asking about a port job.

Hey Gary, how about a little more info???
 
Interesting.
Ive never heard of flow matching via porting.
Id be interested in hearing how thats gets done.
Do they have machines to measure air flow through the ports?
 
Kahuna said:
Interesting.
Ive never heard of flow matching via porting.
Id be interested in hearing how thats gets done.
Do they have machines to measure air flow through the ports?
Click to expand...

http://www.lycon.com/ly-con/specialitys.html

Third item on list.

This is an old hot rodder trick from the dawn of internal combustion;) Remember the old song "Little Deuce Coupe" line in there "shes ported and relieved"....

Idea is to flow more air/fuel, and makes more HP.

Can be done by hand-----old school, or new way is CNC.
 
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Kahuna said:
Interesting.
Ive never heard of flow matching via porting.
Id be interested in hearing how thats gets done.
Do they have machines to measure air flow through the ports?
Click to expand...

Mike,

I've got hundreds of hours on one of these.

http://www.superflow.com/Flowbenches/sf600.html

Intake Port shape is considered by many to be black art, but as in most things, apply enough science it all becomes clear. The performance gains available on our slow turning aircraft engines aren't the same as on a 15,000 rpm 600cc alcohol burning mini sprint motor, but there are certainly gains enough to make the investment of time or money.

Kenny at LyCon has a 7 axis cnc machine and does a fantastic port matching job.

Slick
 
line item on quote

I just got a quote on an IO-375, one of the options is "flow match cylinders". Never heard the term, but it does make sense that it is related to port and polishing. Thanks for the informations.
 
When I was getting my engine from Aerosport back in about 2000, Bart said that they routinely sort cylinders based on their flow bench numbers. Not modify them, just sort. That, together with FI, allows one to balance both air and fuel. It is a way to move the "smoothness needle" a little further. How much? Don't know.
 
Well Ill be darned.
Learned something. Thanks gents.
seen lots of porting.
Didnt know they were now flow matching ports and selling as a premium.
Geez. My engine is now worth even less than I thought before.

Be interesting to see just how different the numbers really are between cylinders. What say you Slick with the hundreds of hours on the machine? Course I assume your time is not on aviation cylinders.
 
Penn Yan

Penn Yan flow matched mine to within 2%. They flowed them at valve openings varying from .05 inches to .350 on both the intake and exhaust side. The closer the flow between cylinders, the more uniform will be the air/fuel charge and result should be a more equal power pulse from each cylinder. This should make it run smoother and maybe a little more power.
 
Remember Bill Elliot's heyday?

Kahuna said:
Interesting.
Ive never heard of flow matching via porting.
Id be interested in hearing how thats gets done.
Do they have machines to measure air flow through the ports?
Click to expand...

Ernie Elliot had found THE cylinder head expert, somewhere in Texas, IIRC, and quickly blew away the competition, back in the eighties, Mike.

Many aspects enter into the equation, like smaller diameter valves for a higher induction airspeed flow and so on. The really good head shops know what the optimum valve diameter is for a given engine/RPM combination....and yes, they've had machinery that measures flow through the heads/ports for ages.

Good porting shops also re-shape the casting of the valve guide support to more aerodynamic shapes to reduce turbulence within the port and smooth airflow.

Best,
 
I've been wanting to drop my cylinders on a superflow not to port them...rather to find out what exhaust valve lift is for each cylinder and adjust valve lift with adjustable rocker arms I had made to set each cylinder so they flow the same. At the RPMs we run I don't think very much can be gained by porting and polishing, especially on parallel-valve cylinders.
 
I agree..

My opinion on flow matching would be more for smoothness, since you'd probably be making more equal power strokes.

Best,
 
rocketbob said:
I've been wanting to drop my cylinders on a superflow not to port them...rather to find out what exhaust valve lift is for each cylinder and adjust valve lift with adjustable rocker arms I had made to set each cylinder so they flow the same. At the RPMs we run I don't think very much can be gained by porting and polishing, especially on parallel-valve cylinders.
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FWIT Barrett Precision Engines offers flow porting on experimental engines but I passed on it.

However the valve seats are precision cut at 3 angles rather than lapped, all parts are balanced including the crank (FAA approved) plus some other stuff that makes the engine run smooth. The end result was 187 HP on the test stand. Flow porting might have improved the HP a tiny bit but more compression would have done that too.

All in all, not too shabby for a stock parallel valve IO360. I got what I wanted, a good light weight engine.
 
flow matching

Flow matching is more productive on the parallel valve cylinders. The angle valve cylinders are closer to optimum in their stock form. I would be very skeptical of getting a decent job at $500 for four cylinders. The prices I have seen are more in the $1000 range. Some shops claim little or no performance increase from flowing cylinders. Others make wild claims of increased horsepower. I believe the more conservative shops.
 
This is flow matching in this context

AlexPeterson said:
When I was getting my engine from Aerosport back in about 2000, Bart said that they routinely sort cylinders based on their flow bench numbers. Not modify them, just sort. That, together with FI, allows one to balance both air and fuel. It is a way to move the "smoothness needle" a little further. How much? Don't know.
Click to expand...

No port work for this price. Heads are matched on bench for flow. Result is smoother engine and better ability to run LOP. Got this on my Mattituck IO-360 parallel valve. With injection and electronic ignition, I can lean and the first time it gets rough is when the engine dies as all 4 cylinders lose the ability to fire at the same time.
GAMI injectors are used to correct for different flow rates of the cylinders. Getting flow matched cylinders fixes the problem at the source.
I still have my cylinders peak about 50 degrees spread, but they get to be the same by 100 LOP.
Not worth running that lean because you get REALLY slow, but running 25 LOP at an appropriate power setting is smooth and cool for the engine.

Seb Trost
RV-7A
470 hours
Boulder City, NV
 
Flow Chart 0360

Here's a flow chart for the stock 0360 that is fairly accurate. They are real close to the same CFM numbers that I get on my SuperFlow.
 
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