Bbrstompit
Member
What are honest hp and tq numbers on a good AKRA unrestricted, and all size plate engines? I’ve never seen what each one of these should make
Honest hp numbers
- Thread starter Bbrstompit
- Start date
Depends on the dyno and how it is set up. I have seen the same FH engine make 8.5hp on one dyno and 14hp on another. A good clone on my dyno is 14.5 but it is set 30% to the high side. This makes tuning easier as small changes are amplified, Almost all dynos use the same percentage.
1fasttiller
Member
Exactly, and remember a builder can tell his dyno to read anything you want. They all have corrections and modifiers built in that you can manipulate. Dynos are a tuning tool and that is all they should be used for.
Bbrstompit
Member
I know they have correction factors and you can make them read whatever you want to. That’s why I was asking for honest numbers.
racinnut15xm
Member
I think the important thing is to go to the same place over and over, make sure they aren't messing with the correction factors. Be honest and upfront with them, I don't care what it makes I want to know if what I changed made more or less than before. You are collecting data and not trying to beat your chest with the highest dyno numbers around.
Sorry that's a bit off base but the ones ive seen dynode made 10-12
Sorry that's a bit off base but the ones ive seen dynode made 10-12
Bbrstompit
Member
How much power difference is there between a green or red plate and unrestricted ?
alvin l nunley
Site Supporter
My water break dyno that I built back in 1985 (the dark ages) used a strain gauge. Now I strain gauge puts out an analog signal. You run that signal through a analog-to-digital converter, and that goes to the computer. I had a known weight at the end of a 1 foot bar that was bolted to the dyno. The software had a calibrating routine. Running a that on the computer would show me a number, I could then tell the computer how many foot-pounds of torque that number represented, i.e. the weight I had hanging on the absorption unit. Based on that number, the computer could calculate what numbers, bigger or smaller, represented how many foot-pounds of torque the engine was producing.
I don't know how accurate strain gauges are today, but in those days they were very sensitive to the ambient temperature. Not having a temperature controlled room, I had to calibrate often.
It would have been real easy to cheat by just telling the computer that that number represented more or less weight.
Knowing this, you can see how cheating is not built in for the purpose of cheating, it's just something you can do if cheating is your purpose.
In retrospect, I should have installed a barometer and a temperature gauge to do it automatically. It's just a little more money for the gauges and some programming.
I don't know how accurate strain gauges are today, but in those days they were very sensitive to the ambient temperature. Not having a temperature controlled room, I had to calibrate often.
It would have been real easy to cheat by just telling the computer that that number represented more or less weight.
Knowing this, you can see how cheating is not built in for the purpose of cheating, it's just something you can do if cheating is your purpose.
In retrospect, I should have installed a barometer and a temperature gauge to do it automatically. It's just a little more money for the gauges and some programming.
Jmuck1
Member
True statement, I've used the same dyno for years. Once you have a baseline you can tell where you stand with each motor.
When I upgraded my Hewitt Dyno 2 years ago with the latest sensors and software from Performance trends. My clones went from 13.5hp to 18hp. It took a bit of adjusting to lower the numbers back down to 14hp. All I changed were the sensors, cables, wires and software, the mechanical parts of the dyno were unchanged.
Johnny Smith
Member
If your dyno says the engine makes 10 horsepower and the engine will win, build to 10 hp. Performance Trends software can be manipulated with out even having an engine on the dyno it is hooked to. You can make it say what you want without even starting an engine. Use it as a tool to get you where YOU need to be to win.
I use inertia dyno with all the clone measurements input and not the Briggs a really good pro clone on mine is between 91/2 and 10 hp that’s what we shoot for on all our non restricted our software is performance trends 4.2 and is very consistent I even use it on the sf60 flow bench I’m looking forward to racing to see if the hours of r&d have paid off We have one engine that has probably 200 pulls on it so we thought we would pull it apart and check it out but after pulling the head and side cover looking at the rod we left the bottom together (the cylinder looked great) but the head needed a rebuild actually the exhaust valve was all that needed attention I do want to say the builder prepared national motors they earn their money!!!!
DynoDon
Moderator
On my old analog water power prake dyno, i am showing high 12 and low 13 h.p. on an unrestricted clone. I frequently put a 212 hemi on my dyno to calibrate it. The hemi is 7 h.p. @ 3600 rating. Those numbers are very close on my dyno. With that being said, i am satisfied my dyno is very close to accurate
alvin l nunley
Site Supporter
I'd love to see one of your pulls. Torque and RPM is all I need. Raw numbers with temp and baro.
alvin l nunley
Site Supporter
I would be very interested in hearing how you compensate for ambient weather conditions. Temperature and barometric pressure differences are significant when it comes to torque readings and calculating corrected horsepower.
DynoDon
Moderator
Oh and by the way, you also need humidity readings. You arent going to get correct numbers if you
Calculate with just temp and baro
steve baker
Moderator
Yes, from best to worst air over the years, we have seen a 10% power variation due to atmospheric conditions. Also remember humidity plays into the calculation as Don stated.
If your not using weather correction information, Dyno R&D activity is going to be very inaccurate over time.
Steve
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alvin l nunley
Site Supporter
According to information that I've read on-line, using 30% to 80% absolute humidity (different from relative) the horsepower correction factor only changes by .021. That's not a lot! And you have to consider that's over a 50 point difference. Hardly something you're going to see in any given days humidity readings.
I suggest reading up on "relative humidity" versus actual humidity.
steve baker
Moderator
We use vapor pressure, derived from wet bulb / dry bulb readings. Additionally Al, .021 for a 10 HP engine is .21 HP, in our world of R&D that is huge!
Steve