How many hosses??

[GRANT ED]

I have been in contact with Mahlon in the last few days regarding buying on of his engines. He said.
'Higher compression pistons are a way of increasing the engines power output and we offer an increase from standard compression of 8.5:1 to 9.2:1. The result is an increase of power of about 5 horse power."
and
"We also offer an option to change the induction system on the engine to a
forward facing cold air system from a vertical induction system. This also
increases the horsepower output of the engine by about 6-7 horse power."

[Captain_John]

OK, So if 9.2:1 is 188 hp... is that right? Mahlon told me once, but I forget.

188 plus 6 is 194. Add in angle valves, what are they worth? Maybe another ten hp there? I gotta say with those numbers we are getting there.

I realize these things aren't perfectly cumulative and totally additive, but by doing this exercise beforehand it will make it interesting to check it on a dyno later.

CJ

[GRANT ED]

Originally Posted by Captain_John

OK, So if 9.2:1 is 188 hp... is that right? Mahlon told me once, but I forget.

188 plus 6 is 194. Add in angle valves, what are they worth? Maybe another ten hp there? I gotta say with those numbers we are getting there.

I realize these things aren't perfectly cumulative and totally additive, but by doing this exercise beforehand it will make it interesting to check it on a dyno later.

CJ

Hi John,
Firstly I'll explain something about the IO-360.
There are two versions of the IO-360 lycoming engine
There is the Parallel valve version which puts out 180hp standard.
Then there is the Angle valve version which puts out 200hp standard.
The valves in these engines are not interchangable. You cannot put the angle valve setup in the parallel engine expecting to gain horsepower.
Mahlon has told me that the 9.2 CR pistons will add 5 hp.
So that gives you 185 or 205hp depending on the engine you get. Adding the horizontal induction will add about 7 hp but this is only for the 180hp engine because it is standard on the 200hp engine. So now your totals are
192 and 205.
Now this is where it starts to get interesting. I have spoken to serveral engine builders all of which say the 200hp IO-360 is not actually 200hp. The general concencus was that they average about 193hp on the dyno. I'm not sure what the 180 averages. I believe it is less than 180 but only very slightly (1 or 2 hp).
So what we have now is 190 ish Vrs 193 ish, not much difference there.
Also we have to consider something else and that is weight. The Angle valve 360 weigh's 44 pounds more than the parallel valve engine.
I would rather sacrifice the 3 hp for 44 pounds less weight.
It is because of all this that I will be buying the 180hp engine with horizontal induction (using the superior version save a few pounds). Most probably the Mattutick FADEC engine.

All this info is from what I have been told. All the information came from people that have much more knowledge regarding aircraft engines than I.
Take this for what you will but outright horsepower is not always the best answer for performance. Weight is also a factor too.

[Captain_John]

Ed, I see. Cool, some of that I already knew. It was interesting to hear the way you put it.

Anyhow, I agree entirely. I also agree that the 180 Para engine is the one for the -8. I am building a -7. I feel that the 44 extra pounds of the Angle valve engine on the nose to be beneficial to W&B.

One more question:

Although I intend to run AVGas, what is typically the highest compression generally accepted for running MOGas?

I suspect that I will be too high CR-wise to use MOGas, but it is an interesting thing to know.

CJ

[GRANT ED]

I have been told by Mahlon (A very helpful person) that Mogas can be used on the standard engine but Avgas must be used with high comp pistons and/or electronic ignition and FADEC.

I am building an RV-7 and have decided to use the 180hp motor to keep the weight down and CG back a bit.

I have spoken to a few local's with RV-6's. One has an O-320 with fixed pitch prop, another has a O-360 with constant speed. The O-360 is faster but I'm told the O-320 powered plane is much "nicer" to fly due to the lower weight and the CG being further back.

[mahlon_r]

A hos is a hos, of course of course, unless of course, you are talking about a hos off course...... I wasn?t ignoring you guys, just was out on the road with no internet access. Man in the last month I have been away more then home! Tired of traveling!!!!!
Anyway, the 200HP angled valve engine normally is a little light 196-197 corrected. Although some do make a little more then 200, on occasion. On average, it would be safe to say 197-198. Now the normal easy compression increase, in the case of the angled valve engine, is from 8.7:1 to 10:1. This normally adds about 10Hp to the stock 197-198 you get regular.
The parallel valve engine normally comes in pretty close to 180 HP stock. Adding the forward facing cold air sump adds about 6-7HP and increasing he compression from the standard 8.5 :1 pistons to 9:1 pistons adds about 5 HP.
So a forward facing 9:1 compression engine typically yields 192-193 HP as compared to a stock angled valve engine at 197 or so. In that comparison the FWF hi compression parallel valve engine would seem to be the way to go. Only 4-5 less hp and a lot less engine acquisition cost and a lot less weight.
However, the angled valve engine with 10:1 pistons as compared to that parallel valve engine with fwf sump and 9:1, will gain you a fair amount of power (10-15 HP), along with the extra weight (approximately 37 lbs for the counterweighted angled valve version and approximately 22lbs for the non counterweighted angled valve version) and expense (5-10 thousand depending on sources) of that engine.
The standard parallel valve engine was certified on 91 octane fuel and thus will stand up to MOGAS at 92 octane OK. The 200 HP angled valve engine was certified on 100 octane fuel and many do use real high test type mogas in them but generally speaking and in my opinion, that engine along with any compression ration increases from standard on any engine, the operator should orientate themselves to 100LL.
Good Luck,
Mahlon
"The opinions and information provided in this and all of my posts are hopefully helpful to you. Please use the information provided responsibly and at you own risk."

[RV7ator]

"I am building an RV-7 and have decided to use the 180hp motor to keep the weight down and CG back a bit."

Ed,

Regarding the c.g., my -7 has the 180 hp parallel valve engine and a Hartzell. The empty c.g. is rearward enough even with all that weight up front to push the loaded c.g. out of limit with less baggage weight than the structure limit for the baggage area. I can take off with nearly 150 lbs in the baggage area, but it must be with full tanks; as fuel burns, you would have to shed bag weight to stay within the aft limit. The shift is noticeable. Our bird is fully primed with the heavy chromate/lead stuff and fully painted, so it's empty c.g. is biased rearwards, which exacerbates the baggage problem.

I say all this because I would caution against driving the c.g. aft during construction. I would do everything I could to bias the c.g. forward. Still, I wouldn't make an engine choice solely on c.g. worries, but c.g. is worth considering if most of your missions involve taking the kitchen sink.

John Siebold

[GRANT ED]

Originally Posted by RV7ator

"I am building an RV-7 and have decided to use the 180hp motor to keep the weight down and CG back a bit."

Ed,

Regarding the c.g., my -7 has the 180 hp parallel valve engine and a Hartzell. The empty c.g. is rearward enough even with all that weight up front to push the loaded c.g. out of limit with less baggage weight than the structure limit for the baggage area. I can take off with nearly 150 lbs in the baggage area, but it must be with full tanks; as fuel burns, you would have to shed bag weight to stay within the aft limit. The shift is noticeable. Our bird is fully primed with the heavy chromate/lead stuff and fully painted, so it's empty c.g. is biased rearwards, which exacerbates the baggage problem.

I say all this because I would caution against driving the c.g. aft during construction. I would do everything I could to bias the c.g. forward. Still, I wouldn't make an engine choice solely on c.g. worries, but c.g. is worth considering if most of your missions involve taking the kitchen sink.

John Siebold

Thanks for the info John.
Hmm it seams as though I am getting conflicting reports. When I was looking at engines I was warned against getting the 200hp motor because the extra weight moves the CG near the forward limit. I am not saying this is true but it was what I was told.
I plan on using the 180hp motor with a Whirlwind prop. I will be priming everything but my RV will have no lights or autopilot (thinking of extra weight down the tail).
If your CG is at the back limit it makes me wonder how the fixed pitch O-320 guys get on!!!
It make's it tough when different people tell you different things

[Captain_John]

Well, the kitchen sink will make many trips with me. He is fuzzy and weighs in at about 54 lbs.





Anyways, I like the luxury of extra horsepower and always buy the engine option in everything I own. With this said, the 200 will likely be the way I go.

Mahlon, how many horesepower is this recipie likely to yeild?

TMX IO-360, Angle Valve, non counterweighted, FWF induction, P-Mags, Auto plugs and 9:1 compression... ok, should I go 10:1?

My goal is a solid 200 hp's. If I get 201, I will be happy. I realize it is just a number, but I really want a robust engine setup.

If I fall short of 200, I won't lose any sleep either.

CJ

[penguin]

This has been a real interesting thread, but perhaps there are a couple of other issues. The exhaust has significant impact on power. The Vetterman exhausts are very good quality with truly excellent support, but do they produce maximum power? I don't know, but companies like Sky Dynamics offer 4 into 1 systems that (apparently) maximise power output. Also consider the ignition system, if Mahlon's numbers are with magnetos then an electronic ignition will almost certainly produce more power - I recently added an emag to my O-320 and got another 80rpm static.

Another point is heat, more power only comes from burning more gas and creating more heat. I'm having trouble keeping the CHTs in my RV-6A below 380F (but only have 30 hours since overhaul). What will high compression pistons, and other goodies, do to the temps - and therefore the longevity - of the engine? There's no free lunch! Also consider the vibration, it has taken me a long time to get the vibration to a point where I can cruise for 2 hours in comfort. Will high comp pistons make the vibration worse? Can the additional power be had with regular pistons at 2800 or 2900 rpm?

BTW I think the cg issue is a hangover from early RV-6 days (light wood prop & O-320) where it was quite possible to get the cg out of the aft limit with only 30 or 40lb of baggage at low fuel states. The -7 is much less sensitive (the firewall is an inch further forward), but if you want to carry the kitchen sink it would pay to be careful with what is installed in the back end. A CS prop should help keep the cg far enough forward.

Yours, Pete