port and polish

hey all,

I was reading from Penn Yan about their XS-IO-360. It has a port and polish option for $800. Claims it adds 10-15 horsepower. Anyone have any thoughts or comments on whether it is worth the $800?

Thanks,
Jonathan

Racing days

Hi Johnathan,
Back in my old drag racing/go kart racing days, porting/polishing would be the starting place for sure. We did it with model airplane two strokes as well. IF the amount of horsepower gain is a documented fact then I can't see any cheaper way to gain that much horsepower. Disassembling the engine and adding hi-comp pistons which would cost quadruple that,
Regards,

I've flow benched several Lyco and Conti heads years ago and they were pretty poor relatively speaking. There are some areas in the guide and seat areas where the stock design could be improved on with minor work. I saw a quick 8% gain on the intakes and 10% on the exhaust ports.

I'd agree, this is the cheapest 10-15 hp you are likely to find.

This thread discusses porting and polishing and has my report from visiting Penn Yann and directly asking the question.

http://www.vansairforce.com/community/showthread.php?t=3535&highlight=Penn+Yann

Jekyll

YES YES YES

You will find smoother operation, better fuel economy and more HP...

Sometimes yes, it helps a LOT; sometimes not so much.

ECI, TCM, and Lycoming cylinders are helped significantly in most cases. Superior cylinders are not improved much by porting because they start out so smooth and uniform as a result of the casting process.

Porting does a LOT to the above mentioned cylinders. Polishing is not as good an idea fomr my experience. Polishing results in a surface that does not flow as well because the boundary layer is kept in better condition with a slightly rough surface, like is present after porting.

I have always ported, but never polished the above mentioned cylinder sets until I had a Top Overhaul with Millineum cylinders. We did not touch those.

Hope that helps.

Walter

Polishing and porting

Read this thread with much interest, but the only mention of the use of instrumentation is the entry of the flow bench. I, too agree that Continentals, and especially Lycoming are pretty poor.
Typically, looking carefully beneath a valve seat of the majority of Lycoming cylinders, and you'll find a gap, which does not a smooth flowing port make. From dyno experience, there is a gain in a properly shaped port, with correct flow, and there will be a power gain. The gain can only be measure with the use of a dynomometer. Conjecture, ain't gonna cut it.
It is true that by removing all the "hockers" hanging on any typical Lyc/Conti cylinder, will indeed aid cooling, which in it self, is a power robber. Polishing is another matter. A bright mirror polish is a very poor idea, especially in air cooleded engines. A smooth finish is far superior. The natural tendency for fuel to "stick" to the surface, will aid tremendously in cooling and fuel/air distribution, in addition to dissipating unwanted heat.
On dynomometer pulls, we found that "polishing/porting" was not an automatic power gain, and that if it was to be, it required flow charisteristics that complied with the remaining ot the components of the engine.
In the case of Lycomings, unless dractic measures are taken to significantly improve porting shapes, which will improve flow in conjunction with the rest of the components, the 15hp gain is very questionable.
The gains to be had will be that all ports can be made to be somewhat equal in volume, and that they can help out in much need cooling, which will prevent power from being robbed. Yes, it would be a power gain, but power that's already there.
Keep in mind that horsepower is also a function of engine speed, and for that reason, a 15 hp increase is questionable, however, better cooling and "evenly" flowed conduits is always a help, if for any other reason, a reduction fuel consumption for the same power setting, which in itself can be construed as a power gain.
One other little tidbit, if the Lyc was to be a candidate for improving flow, engines can be "overflowed". This is a fine balance in which all components, manifolding, carburation/FI, engine speed, cams, etc, must be "balanced". Just because the flow bench indicated that gases movement can be quadrupled, for example, does not meat that it will increase power. In most cases is just the opposite.
T88

In and Out

tacchi88 said:

One other little tidbit, if the Lyc was to be a candidate for improving flow, engines can be "overflowed". This is a fine balance in which all components, manifolding, carburation/FI, engine speed, cams, etc, must be "balanced". Just because the flow bench indicated that gases movement can be quadrupled, for example, does not meat that it will increase power. In most cases is just the opposite.
T88

Click to expand...

T88 ... I think you are correct about the whole "system" needed to be balanced..... but compared to certified planes that have exhaust systems like this...



Our crossover Vetterman exhausts are much more efficient.

If this is the case, then opening up the inlet system will just allow us to use the improved (over a std. Lycoming set-up) efficiency of our typical exhaust systems.

This has been shown in Grumman Tigers, where the dealers are delivering the new models with Lycon "porting" and a Powerflow exhaust system (note that no crossover exhaust systems are certified for the Tigers).

As you say, the "in" and the "out" both need to be taken care of.... ...but I think we start off with a fairly good "out" in our RVs....

gil in Tucson

The local shop, which is very well respected and has a ton of experience, and which does not sell porting services has documented a repeated 10-15% increase for customers using Lycon porting.

I tend to believe them, since they do not sell the service, and offer the same warranty on the engines with such cylinders installed.

Dumb question perhaps, but assuming the 15% gain is the peak, at what RPM does this occur? My experience with cars and bikes is that such gains are usually at pretty high revs, but I have no idea about lycs.