|
-
POSTING RULES

-
Donate yearly (please).
-
Advertise in here!
-
Today's Posts
|
Insert Pics
|

04-30-2015, 01:05 PM
|
 |
|
|
Join Date: Oct 2005
Location: 08A
Posts: 9,500
|
|
Quote:
Originally Posted by Sig600
My lycon built IO-360 cruises at 170kts TAS on 8 gph with a three blade MT for comparison.
|
230 HP. Gee, why so slow?
Way back, when Monty asked what I wanted, I told him to build a tractor motor, no hot-rodding at all, just careful dimensioning and balancing. I wanted one that would last.
So, my poor 'ole wimpy IO-390 was only making 205 corrected-to-standard-day horsepower when it left the Barrett dyno. It probably picked up some power with additional break-in, so I figure it makes the rated 210 now. It's still running mags, and breathes full time through a filter.
Yet, strangely enough, it seems to run with mega-motors from the land of fruits and nuts.
Here's the same altitude, 25~30F lean of peak; 7.8 GPH, 178 ktas. The 58% power figure is based on MP and RPM alone, as GRT doesn't bother with corrections for mixture. Running LOP, it's it's probably not even doing 55%.
Here's flat out on a good day:
Sure, I've done some cooling drag work, and it has a one-piece bubble. There are no other drag reduction tricks...no faired hinges or drains, no funky wingtips, single-sided tailwheel links....nothing. But, it's OK if you figure this strange equality with the Big Dog motors is all due to the airframe. That view simply illustrates that any drag reduction is a lot cheaper than hot-rodding, with more reliability.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
|

04-30-2015, 05:21 PM
|
 |
|
|
Join Date: Oct 2005
Location: 08A
Posts: 9,500
|
|
Quote:
Originally Posted by rv6ejguy
Ah, the old X dyno vs. Y dyno. The only way to know if your statement is true would be to do a calibration test. Who's to say that some other engine builder's dynos are correct? Everyone likes to think their dyno is dead on.
|
There are subtle differences, even when both dynos are perfectly accurate. For example, consider dynamic pressure. The prop reaction dyno in the first photo will show more peak HP than an identical engine will show on a water brake dyno. The prop dyno is pushing a strong stream of air at the horizontal intake, while the water brake dyno sits in a room full of still air. A nice little 145 knot breeze is good for an extra inch of manifold pressure at sea level.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 04-30-2015 at 05:25 PM.
|

04-30-2015, 07:19 PM
|
|
|
|
Join Date: Oct 2009
Location: lena, il.
Posts: 305
|
|
dyno
Since there seems to be a fair amount of interest in this topic I thought I would share my data. I have a Ly-con .010 over IO-390 that we dyno'd (not at Ly-con) recently. It has forged pistons with ceramic coated tops , moly coated sides and circlip retained wrist pins. I had the compression set up at 8.7 to 1 so it can function on lower grade fuel. Air flow performance injection, flowed cylinders,Ly-con cam & lifters and (2) latest version P-mags.
The dyno was a water brake type that used the intake air flow to cool the water in the dyno. I also don,t know about any calibration of the unit. My goal was to see what timing was needed to get max power and what was the reduction in power at "conservative" timing.It also provided some run in time.
The hp. numbers were 227 with usable timing but advanced more than I will probably run on normal use. 217 hp. was achieved at a very conservative setting. I will be using a EI Commander in this plane.
Up the compression to 10.5 or more, positive pressure intake, cold air intake one could see another 10% which would be 250 hp. It will be about 6 mo. till I fly this engine, and it is going into a 165 mph plane with a 80 inch prop. It won't be a fast plane, but I think it will be fun. Ron
|

04-30-2015, 08:33 PM
|
|
|
|
Join Date: Nov 2005
Location: KRTS
Posts: 1,798
|
|
Quote:
Originally Posted by DanH
230 HP. Gee, why so slow?
Way back, when Monty asked what I wanted, I told him to build a tractor motor, no hot-rodding at all, just careful dimensioning and balancing. I wanted one that would last.
So, my poor 'ole wimpy IO-390 was only making 205 corrected-to-standard-day horsepower when it left the Barrett dyno. It probably picked up some power with additional break-in, so I figure it makes the rated 210 now. It's still running mags, and breathes full time through a filter.
Yet, strangely enough, it seems to run with mega-motors from the land of fruits and nuts.
Here's the same altitude, 25~30F lean of peak; 7.8 GPH, 178 ktas. The 58% power figure is based on MP and RPM alone, as GRT doesn't bother with corrections for mixture. Running LOP, it's it's probably not even doing 55%.
Here's flat out on a good day:
Sure, I've done some cooling drag work, and it has a one-piece bubble. There are no other drag reduction tricks...no faired hinges or drains, no funky wingtips, single-sided tailwheel links....nothing. But, it's OK if you figure this strange equality with the Big Dog motors is all due to the airframe. That view simply illustrates that any drag reduction is a lot cheaper than hot-rodding, with more reliability.
|
Why's your manifold pressure so low at 11.5?  . Your cylinders are kinda warm too, may want to work on that. LOL. Seriously though, youre light on fuel and I'll bet my planes empty weight is probably 200 lbs more. The paint alone was >60 lbs, ouch.
Admittedly, the three blade prop is not optimal for cruise performance, but it climbs like a cat on a screen door!
__________________
Next?, TBD
IAR-823, SOLD
RV-8, SOLD
RV-7, SOLD
Last edited by Sig600 : 04-30-2015 at 08:38 PM.
|

04-30-2015, 09:15 PM
|
 |
|
|
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
|
|
Quote:
Originally Posted by DanH
There are subtle differences, even when both dynos are perfectly accurate. For example, consider dynamic pressure. The prop reaction dyno in the first photo will show more peak HP than an identical engine will show on a water brake dyno. The prop dyno is pushing a strong stream of air at the horizontal intake, while the water brake dyno sits in a room full of still air. A nice little 145 knot breeze is good for an extra inch of manifold pressure at sea level.
|
Well if they use corrected or observed hp in these two cases, could be very different even if the dynos are calibrated accurately. In the auto world, we usually correct to 29.92, dry air and 59 or 60F.
Using uncorrected or observed hp to compare two different engines or two different dynos is apples to oranges and a waste of time.
I'd sure hope aircraft engine builders are using corrected hp for atmo engines.
Now turbos are a different matter. The savvy operators use observed hp and simply state rpm and MAP. Many people in the auto dyno world erroneously apply SAE atmo correction factors to turbo engines which ends up with inaccurate (but impressive) hp figures, especially if the dyno is well above SL.
Last edited by rv6ejguy : 08-10-2015 at 04:24 PM.
|

05-01-2015, 05:29 AM
|
 |
|
|
Join Date: Oct 2005
Location: 08A
Posts: 9,500
|
|
Quote:
Originally Posted by rv6ejguy
Well if they use corrected or observed hp in these two cases, could be very different even if the dynos are calibrated accurately. In the auto world, we usually correct to 29.92, dry air and 59 or 60F.
Using uncorrected or observed hp to compare two different engines or two different dynos is apples to oranges and a waste of time.
|
In the example given (prop dyno with a horizontal intake vs a water brake dyno), corrected or observed would not change the comparison, assuming they both used one or the other. The engine on the prop dyno would still enjoy higher MP. Sure, a sharp observer would note the higher MP, but higher MP at the valve is the whole point of atmo engine intake tuning. It sure as heck isn't going to appear on most torque and HP graphs.
That said, yes, it's a safe bet that a lot of buyers, not understanding the difference, would talk about the best number they heard or saw, be it corrected or observed. To complicate the issue, some dyno software will make the correction, and some output observed only, thus requiring post-run correction by the operator.
__________________
Dan Horton
RV-8 SS
Barrett IO-390
Last edited by DanH : 05-01-2015 at 05:36 AM.
|

05-01-2015, 07:01 AM
|
 |
|
|
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
|
|
Quote:
Originally Posted by DanH
In the example given (prop dyno with a horizontal intake vs a water brake dyno), corrected or observed would not change the comparison, assuming they both used one or the other. The engine on the prop dyno would still enjoy higher MP. Sure, a sharp observer would note the higher MP, but higher MP at the valve is the whole point of atmo engine intake tuning. It sure as heck isn't going to appear on most torque and HP graphs.
That said, yes, it's a safe bet that a lot of buyers, not understanding the difference, would talk about the best number they heard or saw, be it corrected or observed. To complicate the issue, some dyno software will make the correction, and some output observed only, thus requiring post-run correction by the operator.
|
Yes, most dyno's software packages are correcting for atmospheric differences so the experienced operator using a prop dyno should also be applying a correction for static MAP vs. actual MAP WOT. In this way, corrected hp should be the same on the 2 different dyno types on the same engine.
As a further thought, many dynos don't make correction for reduced exhaust back pressure at high altitude so if your one dyno was in Denver and the other near SL, corrected hp might not be quite the same on the same engine.
Absolutely, many engine builders and dyno operators love to show peak numbers and possibly even over corrected ones to impress the less well informed customer.
When I was building road race engines, we really used our dyno to compare one change to another and look for useful increases across the effective rpm band or widening that band. Peak numbers, while exciting maybe did not always mean faster lap times. In the end, performance on the track was the true measure of successful engine development. I really didn't care if a competitor claimed 315 hp (a peak value) on some dyno in California. If we spanked him down the straight, that was all that was required, regardless of dyno numbers.
In racing aircraft or something like Salt Flats cars, where the engine is near peak power all the time, peak values are somewhat more important.
For every day use however, dyno figures are more of something to confirm that the engine is healthy after the build. Your plane goes as fast as it goes. If your 360 is faster in all regards than the guy beside you. You'll have the bigger smile.
|

05-01-2015, 03:14 PM
|
 |
|
|
Join Date: Oct 2005
Location: 08A
Posts: 9,500
|
|
Quote:
Originally Posted by rv6ejguy
Yes, most dyno's software packages are correcting for atmospheric differences so the experienced operator using a prop dyno should also be applying a correction for static MAP vs. actual MAP WOT. In this way, corrected hp should be the same on the 2 different dyno types on the same engine.
|
Everybody reputable corrects for station pressure, temperature, and humidity differences with standard day, either using dyno software or with a calculator and correction factor table (note the altimeter on top of the dyno console, first photo). For example, if station pressure is 30.11 Hg, the operator should correct the HP (downward) for what it would be at 29.92 (J607) or 29.234 (J1349) or 29.33 (DIN, 101.3 kPa) or 29.23 (ECE, 99 kPa).
Although somebody's software may be capable of correcting for manifold pressure vs a standard pressure, it would be pointless. Think about it. I could mount a wheezy manifold, a little bitty throttle body, and a dirty air filter, measure 24" MP at WOT because they are very restrictive, but then correct the resulting crappy HP figure for 29.92 and claim some large number the engine cannot produce.
Heck, the whole point of good intake manifolds and large diameter throttle bodies is to increase MP (and HP) to some level close to station pressure. The engine that does it better really is the better engine, at least at WOT.
Quote:
|
As a further thought, many dynos don't make correction for reduced exhaust back pressure at high altitude so if your one dyno was in Denver and the other near SL, corrected hp might not be quite the same on the same engine.
|
Wouldn't that be covered by the station pressure correction? Same atmosphere at the tailpipe as at the intake.
Quote:
|
Absolutely, many engine builders and dyno operators love to show peak numbers and possibly even over corrected ones to impress the less well informed customer.
|
And then there are the dyno-only runs, setups that nobody is gonna run in the airplane. For example, dial in 30 degrees of advance at WOT. Detonation margin is tiny, but that's not a problem with a pro at a console.
Quote:
|
I really didn't care if a competitor claimed 315 hp (a peak value) on some dyno in California. If we spanked him down the straight, that was all that was required, regardless of dyno numbers.
|
Yeah buddy!
__________________
Dan Horton
RV-8 SS
Barrett IO-390
|

05-01-2015, 05:41 PM
|
 |
|
|
Join Date: Mar 2005
Location: Calgary, Canada
Posts: 5,766
|
|
Notoriously hard to accurately correct for exhaust back pressure with baro, depends somewhat on valve overlap.
We also must consider oil temperature and heat soak of the intake. While these have a small effect, it can be cumulative.
Even with the example prop dyno and air coming into the intake at say 150 knots, the MAP rise is minimal with typical ram recovery effciencies, say less than 1 inch Hg. which would equate to about 3% more power. This would take our 253hp engine down to a real 246hp. Then again, who is to say what is real under flight conditions. A good ram intake could see a few extra ponies over a poor one.
The point is really that dynos are best used for comparative development purposes- on the same dyno especially so and only one change at a time to quantify results properly.
Comparing shop X's dyno hp vs. shop Y's on a different engine has some room for error, especially when different correction factors or running procedures are used.
People love to have that number though and are willing to pay to get it. Just be aware it's not strictly comparable and perhaps not even especially accurate in some cases.
I was often asked at the track how much power we were making. My answer was usually "sufficient" (like Rolls Royce used to say) or "more than you". Neither response went over too well with my competitors... The real world told the story.
Last edited by rv6ejguy : 05-01-2015 at 05:53 PM.
|

05-02-2015, 08:16 AM
|
|
|
|
Join Date: May 2008
Location: Sacramento
Posts: 377
|
|
The proof is in the pudding
I too have a Barrett IO 390 with a measely 212 HP. However I fly with many guys with Lycon 230+ HP engines. My 8 weighs 1134 empty and I weigh 290 lbs. So there is no weight advantage over the others. But when we go flat out I always move to the front. I have no drag mods like some do other that the 10 knot fuel drain fairings. (If I put on all the 10 knot mods on would I really have the speed of a glassair?) Horsepower is fun to look at but torque moves things. Lycon builds a good engine but I think their DYNO is there best salesman.
__________________
Horse Power is good, more is better and
Too Much is Just Right
RV 8 Super charged Barrett IO-390
Dues paid 2020
Dan "Nordo" West
|
| Thread Tools |
Search this Thread |
|
|
|
| Display Modes |
Linear Mode
|
Posting Rules
|
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts
HTML code is Off
|
|
|
All times are GMT -6. The time now is 03:43 AM.
|