dyno numbers
 

this web site is all about performance and for you guys that means motors for the most part. i have read a lot of the stuff here and the level of intellegent analysis is really good and my suspicion is that the general technical smarts is really good as well... but what i see is a heavy reliance on the dreaded "dyno numbers" for these motors and some of the same folklore and voodoo that has plagued the motor industry forever... so... lets talk about the easiest thing first... the dyno.

the dyno is nothing more than a water brake that measures the torque the motor puts out at any given instant. period... nothing more. any information it generates beyond that for you is a function of a mathematical algorythm that has a number of different varients and a fair number of user assignable variables. this algorythm is called a " correction factor" and is used so that the operator can correlate his data from one day to the next in some intellegent and repeatable fashion. as you well know, different conditions will make the same motor make different power at different times.... nice cool 50 degree air will make a LOT more power than humid 110 deg florida august air. so what do you do if you are dynoing motors in dec AND august ? the correction factor is supposed to take care of that... and most dynos do it automatically based on the parameters dialed in by the operator...

also... the running conditions of the motor are critical.... 20 degrees of oil temp one run to the next can make 3 and 4 % difference in the raw number.... so if you run your base line run at 180 oil and make a change and then run your next run at 210 oil and see a 3 % increase you might believe you actually MADE more hp.... instead of doing nothing at all or actually losing hp. running a dyno so that the results are true and meaningfull and not just sales litterature is a science..not an artform or magic.

there where litterally dozens of occassion where we would get motors in the door, fresh from builders with dyno sheets attached that were LITTERALLY corrected over 100 hp...and sure enough...when we ran them in the cars they were slugs and when we ran them on our dyno they where slugs.

you need to use your heads and the good brains that you have and stop thinking there is some magic to all of this motor business... there isn't.

if someone tells you the changed their fuel pressure and got 50 hp... they are wrong

if someone tells you can run an 11: 1 motor on 87 octane ... they are wrong

if someone tells you they are making 650 hp out of a single 4 barrel 454 on 87 octane without a turbo or scharger... they are wrong

when someone tries to sell you the magic bolt on widget that will get you 30 hp with no other changes... they are wrong

a good number for a normally aspirated reasonabbly hot 9:1 motor that has a good wide usable power band and will last a long time and that you can run on 87 fuel is a little more than 1 hp per cubic inch. can you get more ? sure... but the law of diminishing returns will bite you in the butt VERY quickly in terms of reliability.

and remember.... the dyno sheets are just pieces of paper from someones machine. if the operator took the air temp sensor and out of the intake when he made the run and layed it someplace hot, then that dyno sheet now says that that motor made a LOT more hp then it actually did....

and when the next guy that tells you he has a bolt on flame arrestor that will make 50 hp just look down... he is probably wearing shiny white shoes and plaid pants and his other job is selling aluminum siding...

Re: dyno numbers
 

Thanks for this, Steve... Now I know that there is at least one more person out there that thinks kinda like I do. I always maintained that the dyno was a tool to make comparisons of different components and adjustments as used on a given modified engine, NOT to generate a piece of paper to be used for bragging rights at the bar or to inflate the value of a questionable piece of iron that you want to sell. --- Jer

Re: dyno numbers
 

Bottom line Power Numbers sell enignes. . .hell they sell cars. What would be the fun in comparing the Z06's interior comfort to the M3's!!! Automotive advertising and marketing caters to our needs of power. Dyno figures in our industry are used the same way. . .to sell engines. A dyno I agree is nothing more then a tuning tool. It allows any engine builder the ability to check, change, and develop power to fit a customers needs. When knobs are turned, false data inputed, then it becomes a marketing tool.

Re: dyno numbers
 

Well you would sure hope that a shop that you've been using for years or any other dyno facility would be playing the game straight and not falsifying data to mislead the consumers. If a person is trained to work the dyno I would hope they take these conditions and add them in the final results... But in the end if there selling you the motor and or parts they can tell you anything you want to hear.

Great now we know Stez dogs are really only 400hp anchors!!!!! :evilb: :evilb: :evilb:

Re: dyno numbers
 

dyno's are cool

Re: dyno numbers
 

From what I understand torque is the better # to look at or can that be fuzzy too?

Re: dyno numbers
 

well...as you say, you would hope so. and im not certain or even suggesting that these guys are dishonest... although i am equally certain that some are... after all... where is their risk ? unless you are racing against like boats, all you guys know ( and myself included) is that the thing makes a lot of noise and is gonna go fast enough to make everybody scream and thats why you bought the boat anyway. if they tell you you have 650 hp and you really only have 575, you wouldn't know the difference anyway. ( thats the corporate "you" not anyone specific)

the bottom line is that building motors and making power is a serious science andthat includes a lot of hours working on combinations on the dyno... an investment a lot of guys don't want to make. they buy the parts off the shelf based on mfg propaganda, bolt them together and , if it starts say... well there you go... 650 hp because i added up all the numbers that the cam, cyl head, and carb guys said... not because anyone took the time to load it up with all the ancillaries and exhaust that your boat actually has and then spend the time to break it in and jet it properly...

and if you believe the dyno sheets you get.... well ... lets talk about swamp land. i'm sorry im such a cynic but 25 yrs in the racing industry does that to you.... ive seen more magic beans come and go then you can count and suddenly anyone that can read a summit catalog is an engine builder.

Re: dyno numbers
 

That is so true about builders and dynoes. Its been that way for a long time. All I want is what I paid for. If they tell me it makes 1000HP you know its not going to be cheap. Their are plenty of packages out their for the doit yourselfers. I wish you guys all the best of luck with them because in the long run my season is short enough to have to do it again and again. And yes you can have 2 identicle motors make different power, Its more than just part to making power. The wrong carb can cost you 50hp. Happy Holidays to All.

Re: dyno numbers
 

As a dyno operator, I think anyone that buys a performance motor should take it to a local tuner to have it dyno'd / tuned for local conditions. A good tuner has no interest in jacking the numbers, he'll be more interested in giving you a good, safe tune. If you already paid 15k plus for a motor, it's worth the extra 500 or so to get the local tune. Plus, tuner's have to eat too!

Re: dyno numbers
 

Case in point. About 4 years ago a customer of mine built a very competitive Nascar Limited Late model engine. These 2 barrel engines by rule are very restricted. Well his combo was a 10th off of the track record, qualified the car in the top 10 just about every night, and at the end of the year the driver and car were 2nd in points. . .just a few back of the Champion. The driver owned the car and my customer's customer owned the engine. Due to some obligations, the driver bought the engine from his partner for $5K. Now for any of you that know anything about this class, that is about 25 cents on the dollar compared to what a new one cost. We'll he took it to an engine builder and the builder put it on the dyno and said it was down about 80HP from his best engine and it needed a list of parts to make it right. $7500 later the engine went back on the dyno and walla, it was 70HP better. Needless to say the driver/owner was excited. . .this lasted till opening day of the new season. The new engine was 3 tenths slower then the old engine and would not pull his old gear off the corner.

So do you think we really had an extra 70HP?

Re: dyno numbers
 

Testing, is only as good as the people doing the testing, and interpreting the information. I never compare dyno sheets when I'm doing A B testing that have more than 1 degree difference in oil temp at the start of the pull, and I normally try to avoid that. The more accurate or (anal) you can be with your testing the better the numbers are going to be. Now here's the tricky part you've got to have someone who can interpret the data for your application. More peak power outside of the range you're running in, but sacrificing your acceleration rate you might not be happy. Just like Chris's customer the engine may have made more power, but may not have been set up for what the racer actually needed.

The main thing is a dyno is only as good as the people using it. I hear on a daily basis how much more power this one makes vs. that one. The bottom line is that the engine needs to fit your requirements. If Your boat runs x MPH, and you want it to run Y MPH within these guidelines (type of fuel, reliability, etc) than the only thing that matters is your boats performance when the engine is done. It's not as masculine, but if I can run 100MPH with 500 HP vs. 80 MPH with 950 HP who cares!

Re: dyno numbers
 

Good discussion. Regarding correction factors...recording temp, barometric pressure (and humidity) allows you to correct your readings to "standard conditions". This evens the playing field, otherwise the dyno shops at sea level in cooler climates would always appear to have stronger engines.

However. find out what "standard conditions" are being used. If they are correcting to 60F and 29.92"Hg the corrected HP numbers are going to be a higher than if they are correcting to SAE standard conditons (77F and 29.6"Hg).

Steve suggests one way that the air temp sensor location can be changed to "help" the HP reading, by putting it some place where the air is hotter than that entering the engine. The opposite can easily happen. Case in point; we were dyno testing a centrifugally supercharged engine in a dyno room at 75F, so HP was corrected using this figure. We also happened to be measuring the air temp entering the supercharger (you need this to calculate efficiency) and found it to be ~95F because the inlet was close to the dry dyno headers. We didn't really care because we were doing back to back testing of other components, but if this test was for a customer, would you correct the HP upwards? (Damn right you would!)

Re: dyno numbers
 

I'm not an engine builder, the dyno and flow bench are tools to establish a base line. For me, the true test is in the boat, but it's nice to have some kind of reference point. HP = speed.

Re: dyno numbers
 

Possibly, but it's all about drive ability isn't it? He made the peak horsepower, but the power delivery (torque curve) wasn't suited to the track.

I know that our racing is small time by comparison. But we have gained time by installing a restrictor plate and in one case pulling a spark plug wire on a short slick track.

Point being that you built a motor suited to the application.

Re: dyno numbers
 

I'm always slightly suspect of dyno pulls where the dyno operator has also built the motor for BIG dollars for a customer! Tyler Crockett always says_"you can't race a dyno,numbers are for accountants".I don't trust the numbers our local dyno's generate at ALL. The proof is in how fast a boat actually goes. This time when I built my 540 I had it dynoed and it made 944hp and over 950 ftlbs of tq and my single engine baja 272 runs almost 95 mph. Last time I dynoed it the motor made 630 hp/700 ft lbs tq and ran 76-78 mph before turning up the boost and timing further. After installing it in the boat with the 630hp/700 ft lb tq combo one day while out on the water I ran acrossed a identical boat with a carbed 540 that a local marina had built the motor for. I know the marina owner who built it and he had already told me how this normally aspirated motor made 70 hp more than my sc motor made and how my motor must be junk. Well after racing the guy's 700 hp carbed 540 boat and pulling about 5 more mph on him with 500 more lbs in my identical boat he was PIZZED :D . I don't know if they manipulated the dyno to give him a fancy piece of paper or what BUT he was pulling 200 less rpm's with a 26 pitch prop vs my 28 pitch,shot the credibility of that shop and the place that dyno's there motors all to crap :D . The guy who owned that boat was happy with his "big"numbers until that,the proof really lays in what pitch prop something can turn and how fast it actually goes. I think they dynoed his motor with step tube auto dyno headers and bumped up the correction factor when it didn't deliver for the 15,000$ he spent,Smitty

Re: dyno numbers
 

Wobble,
True, I always say it is 80% driver and car and 20% engine. This ole boy was a 10 + year veteran of the track and a 2 or 3 time past champion. . .you know yourself with that kind of experience you should be able to take advantage of that kind of increase if it was there...

Re: dyno numbers
 

Smitty,
The "power knob" is under the consol, turn it clockwise to be a hero, turn it counterclockwise to make the last guy look like a zero. I have gotten dyno sheets with 1.15 correction factor.

At the end of the day it is how it runs in the application.

Re: dyno numbers
 

ArticFriends, Your example is great to show the N/A vs. boosted TQ curve. Again I say forget about HP and look at the TQ curve and Peak. You probably had 50-70 more lb-ft of TQ than his N/A motor. Superchargers and TORQUe rocks.

Re: dyno numbers
 

I agree except its probably more like 98 % driver/car set-up and 2% motor on our local short tracks. 5 years ago a local company gave me 50,000$ to build (2) smallblock race motors and (2) back-up motors (just thrown together with leftover parts) for 2 FACTORY STOCK (bombers) circle track cars,I did it for free as a sponsor (it was fun spending SOMEONE elses money on cool parts though). They spent more time hitting the wall and spinning out than anything but they swore they didn't have enough motor!!!! :rolleyes: The cars actually were faster with the spare motors I built out of junk because they had 70 hp less and they could control there cars better! It was fun BUT I had to babysit these guys because they would do stupid crap like dumping 3 gallons of nitromethane in 10 gallons of gas without rejetting or changing timing if you weren't at the track every time they raced to keep them from getting stupid,it got old quick,Smitty

Re: dyno numbers
 

Classic example: I dyno'd a friend's race truck on my chassis dyno. The truck series allows either a 305 homebuilt, or the gm 350 sealed motor. He buys a factory sealed race motor from gm. Gm says set the timing to 32 and max rpm is 5500. I dyno it and sure enough, the power drops after about 5200rpm. I told him to gear the truck to hit 5500 max rpm. So, he resets the timing to 34 and spins it to 6500. two races later the motor is junk. Of course, he says the sealed motors are junk. Some people will never learn.

Re: dyno numbers
 

well... point proven. lots of folklore and voodoo here. the dyno is a tool like anyother and the mathematics that allow the data correlation are well established and proven. everyone that says they have gone faster with slower motors is wrong. everyone that says that they ' tune by ear" is wrong. everyone that says that they can throw parts together in some haphazard fashion and end up with better motors than contientious and well skilled professionals is wrong. it is a romantic notion but simply not the truth.

a skilled and well trained professional will produce the correct motor for the correct application with the correct power band and the maximum reliability 99 times out of the 100 instances. the one random time that the homebuilder gets lucky is just that... luck and not even remotely repeatable. that was not my point in the beginning and is not now.

my point is and remains that the number of genuinely skilled engine builders that take the time and apply a true and genuine engineering approach to the design of a combination and package for a customer and then spend even more time on the development of that package in a ( again) a fundementaly and scientifically sound engineering manner are few and far between. for the most part it has been my experience with lots and lots of engine shops that their engineering and design is merely a matter of believing what the sales people are telling them about the parts they are buying.

it is also my experience that the dyno sheets that accompany these motors are mostly self serving fiction and seldom , if ever, represent what the truth of the matter is... and even at that it isn't that simple... again... my experience is in the cars and not boats but i can tell you that the same motor i built for road america or daytona was NOT the same motor that i built for sebring or mid ohio. if you are going to spend the entire race accelerating off slower corners then motor better have the cam advanced a couple degrees and have small high velocity ports as opposed to a motor thats going to daytona where the ports can be decidedly bigger and the sacrifice of 40 hp down low to make the same 40 up top is a MUCH better deal.... it is not only the AREA under the curve but the very shape of the curve itself.

i guess all i am saying is ( again) in the real world there are no magic beans and magic turbulators or magnetic fuel aligners that will make you 50 hp for free...and no easter bunny either. when someone tells you they are making 650 hp from a 454 on 87 octane fuel with a single four barrel just nod and keep your money in your pocket...

and then look for someone that will tell you the truth

Re: dyno numbers
 

If I may step in on this subject and ask a question about Dyno results and get some opinions from all of you who own and operate Dynos...

We (my engine builder and I) just finished dynoing my 325 hour HP500 carbed engine. Using an automotive header, it made 450 peak horsepower and 455 ft-lbs of torque at 5200 rpms. The torque number decreased steadily from 550 ft-lbs @ 2600 rpms down to 455 @5200. We will use this as a baseline up against the new builds. I have talked him into modifing his dyno set-up to allow us to test and tune the new motors using a wet marine exhaust. Can I compare the old to the new now? Or, should we run the new motor using the same set-up as the old motor?

I really want to run the new motors wet, so I can tune the carbs and have them broke in and ready to run in the spring. I already know what the boat ran before with the old motors. So can I take the difference between the new to calculate props and speed before I hit the water?

Sugestions please!!

Thanks,
Dave

Re: dyno numbers
 

apples to apples. if you really care you will re run the baselines in the configuration you are going to run the finished product... however the bottom line is always what are you trying to accomplish.... set a goal and a hard target and design your configuration around that.. regardless of what it is... decide at what rpm you will want to run and what fuel system you are going to drive it with... THAT will define the port sizes and cam profile... then decide what fuel is available and that will define your compression ratio... the rest is hard parts... and how long you want things to last....pistons with thick heavy rings will last a long time but make less power than thin rings... etc etc....

the first element is always to decide precisely what you want... then the configuration becomes almost self evident.

and the jetting is everything on a carburetted motor.... you will need to be prepared with all manner of jets , powervalves and the like when you get on the dyno... and step testing is what you are going to want to do as opposed to sweep testing.

if you are on your game youll set up the exhaust with exhaust gas temp sensors and jet that way... thats the only way you know whats really happening.

Re: dyno numbers
 

when my engine was dynoed , everything is on the engine as it would be in the bilge. only item not connected was the ps pump. all i may have to do is jet up 1 more size
when it is installed , but i should not have any problems(engine wise) and should live a good life on 87. i am satisfied with 1.04 hp per cube.



great thread...

Re: dyno numbers
 

AXAPOWELL,
I am not a builder or dyno operator but common sense tells me that in order to compare old to new, you should use the same baseline configuration (i.e. setup). After that, go with the wet exhaust and observe the difference.
This thread has prompted me to read further into the world of dyno correction factors.

http://wahiduddin.net/calc/calc_cf.htm

As Smitty said, "It is the on Water Performance that tells the true story."
Russ

Re: dyno numbers
 

I agree to a point but there is ALOT of info for the average gearhead out there regarding cylinder heads and camshafts on the internet that you only found in a occasional magazine article even 10 years ago. There are guys building legit 650 hp 93 octane 540's that have maybe only built a few motors in their whole life. I have assembled/built about 50 or 60 motors in past 22years,many of them stock rebuilds,and I set out to build a 900 hp sc'd 540 and ended up making closer to 950 hp (on a LEGIT DYNO using MARINE HEADERS)with tq forever (850 plus ft lbs tq from 3300 rpm's to 6000,peaking at 962)using a home modified 502 mpi intake and stock plenum and throttle body. Motor runs on 92 octane,idles at 700 rpm's and can spin to 6000 rpm's. 10 years ago something like this was UNHEARD of,don't under-estimate some of us "average "guys on this board. Keep the INFO coming,Its appreciated,we are all EARS and eat up all the info we can find,Smitty

Re: dyno numbers
 

Steve, you are dismissing the comments from a lot of people here and the point is proven in your mind only.

As for faster with a slower motor, you apparently have never raced a dry slick dirt track or a green race track. HP is not the be-all and end-all of short track racing. A point that any Saturday night racer could make. If you really want to make time, get the setup book from a veteran. Chassis setup and driving is what it is all about.

Engine builders that cater to the racing crowd live and die on the reputation and reliability of their product. Dismissing the majority of them seems a little arrogant to say the least.

Re: dyno numbers
 

truth in all of that... and apologize for it. on re-read it is dismissive in a lot of respects and for someone like myself , new in a forum and marine environment in general is simply out of line. sorry about that. re the "slick track " comment , that does in fact illustrate exactly what i was trying to say... those conditions on that day would require exactly what you say they would... NOT nec bigger numbers. and you as that professional in that arena would know that and build the correct motor. thats what being a professional is.

as for the other.. for sure you can make big numbers ( legit) with supercharging and turbo charging thats pretty straight forward and becomes more of a structural exercise than anything else... normally aspirated, nominally configured is a different deal... and that discussion could take 1500 pages...

i started this, not as commentary against anyone . just as a reminder to those in the engine BUYING business that there is more to selecting your vendor than that nice 5 color web page with that impressive curve or that piece of paper straight from the word processor.

racing is different... " res ipsa loquita" ( if i remember my latin correctly) that means " it speaks for itself" in racing , the dyno sheets mean nothing... and the motor shops live and die on the true performance of their product. the motors either perfrom or they don't and the evidence is there immediatly for everyone to see...

in the recreational " hot rod" arena both boats and cars, it becomes more a matter of salesmanship rather than truth. that annoys me and i let it show through and apologize for that completely... hard as this may be to believe at this point was just trying to be helpful and unfortunately let my figers type without my brain being in gear all the way.

i go down to the marina on any given day and there is always some guy standing next to his boat thats been hauled out and the guys are just yanking one of the motors and the story always starts with " i JUST bought this from a shop in miami. SUPPOSED to be fresh rebuild and in four hours on the way to anguilla its started making this noise and then..... "

well... at anyrate... you are right and im wrong. will try to stick to factual issues from now on rather than philosophy

Re: dyno numbers
 

Steve, thanks for your thoughts and welcome to the forum.

Here are some more of mine.

BTW I am not an engine builder, I have used their services for years and have been around racing of many types for most of my life.

Building a hi-performance engine is for the most part a thankless task. From what I see the real money for an average shop is in re-manufacturing specialty type motors. Repetitive stuff etc.

It is rare that an engine builder is given free rein to produce exactly what he wants to build except at the very top end of the market. There are always financial/time or other considerations.

Lets say that he has come up with a very reliable 600hp NA package which he can produce time after time. The customer takes the motor, puts it in his boat/car with his cooling/oil/fuel system and the motor fails because one of these items that was adequate for their old power is now inadequate. The engine builder often gets bad mouthed.

If you search this forum re oil coolers/ oil lines/ fuel pumps/ fuel regulators/ ignition timing. You will see what I mean.

There is indeed much more to selecting an engine builder than reading their sales pitch as you say. There are undoubtedly people that use sub-standard components, produce dyno sheets that are optimistic etc.

I think that in this day and age, the smart approach to buying a package performance motor is to research the builders in the various forums. Run a BBB report and go from there.

Had I started here when I moved up from a jet boat to an offshore type boat I would have saved a bunch of money. Same horsepower but a world of difference in the demands placed on the motor even at 4K rpm.

PS You may not be aware, but some of the people that have responded to this thread (not me) and added their anecdotes are an invaluable source of information and experience.

Re: dyno numbers
 

Steve,
I think in life we find this with almost any profession. The home builder with the fancy trucks and big ads in the paper may cut corners and use inferior products but because of the "show" he is considered good. Where as the guy driving a 1998 Dodge with 200K miles is a very skilled builder and refuses to use sub par material and low cost subs.

You bring out some good points about our industry and I agree the problem is if we combine the years you have been doing it, I have been doing it, Smitty's been doing it, and some others we still don't have enough experience to change human nature; we like new flashy stuff for the most part.

Salesman, I resemble that remark. My take on my profession. I am a problem solver. A customer calls with a need/problem. It is my job to solve his problem. Simple. It is not my job to sell him something that may increase the problem. By doing the first you keep customers, by doing the later they will look for other resources. When I got into sales in '95 in this industry a fellow by the name of Len Sabatine of Sabatine Automotive in Easton, PA was my first sale. Len to this day still buys from me and I am with my 4th company in this industry. It's all about problem solving.

Welcome to the board!!

Chris

Re: dyno numbers
 

Hey Steve: We need some new blood in the Tech section and appreciate your viewpoint. I wouldn't want you to worry too much about offending anyone. Lively discussion makes it interesting and many will learn from the debate.

There is another tool that is getting a lot of attention these days and that is engine simulation software. It is becoming more common for engine builders to build your engine in the computer first for discussion of the combination with you. You think you can make a dyno say anything, play with one of these programs without knowing what you are inputting and watch the big numbers start flying around.

BUT...if you are very careful and input only measured head flow, cam profiles etc. and compare your results against real dyno results you can build a realistic model of an engine. The real advantage of such a model is being able to make changes and learn from the model's response whether you are headed in the right direction. Properly used this tool can save time and money by eliminating some of the trial and error.

I recently started working with Engine Analyzer Pro. You can download a free fully functional demo for 10 days from Pro Trends. Your best use of time for this short period is to enter a well known engine combination and get it predicting the correct known HP. Then start changing heads and cams and watch what happens. At the least it is very educational.

Re: dyno numbers
 

i had heard of that but have never seen it... my understanding is that it uses the same computational thermodynamics model that nasa came up with and , if so , am sure its a hell of a tool. you have to know that that software has been in use by the japanese for years in the bike industry.... now there are beautifuuly thought out and executed motors... street bikes from the factory w/ 11.5 to 1 compression running on 87 octane because the heads and combustion chambers are so good...

Re: dyno numbers
 

TC, where would I find Pro Trend, just curious what it would say about my combo.

Re: dyno numbers
 

Have any of you, or do you know anyone, who has dyno'd a motor with dyno headers VS a wet flow IMCO thumper or EDDIE Marine Thunder type of system? I would only suspect about 20 hp difference considering that there can't be too much back pressure with 4" exausts.

Re: dyno numbers
 

Sorry, it's Performance Trends; here is the web page.

http://www.performancetrends.com/Eng...r_Pro_v3.3.htm

GPM: For centrifugal systems you need to enter flow vs. pressure drop data for the intercooler piping. You can do this using the restrictor plate function. I had this number because I flow tested those parts. The program also asks for pressure drop across the intercooler core, data that I had from the manufacturer. You also need to make an educated guess about your operating point (flow, pressure, RPM and efficiency) on the compressor map.

You may not have all this data, but you have actual dyno numbers, so you can build the engine and play with those entries until intake manifold boost and HP agree with reality.

It's not so much that you run the program to see how it agrees with your dyno numbers. You use the dyno results to "calibrate" the model, then you can try different ideas on the model.

P.S. Take a look at the predictions for compressor HP.

Re: dyno numbers
 

Thanks TC.

Re: dyno numbers
 

Pressure drop varies depending on the acceleration rate of the engine.

Actually, depends on alot of factors, but, that is one that will be most noticed on dyno pulls.

Re: dyno numbers as they relate to boat performance
 

I can honestly say that I am amazed at how much emphasis is put on "dyno numbers" in the performance industry. In performance boating it should be obvious that engine power, ie horsepower and torque is only a part of the equation. When it comes to boats, the whole list is a long one.
1. Hull weight
2. Hull form
3. Wetted surface configuration
4. Center of Gravity
5. prop speed
6. Prop type
7. X-dimension
8. Steps
9. Ventilation
10. Hooks and such
11. drive ratio
12. beam
13. water type
14. water temp
15. air temp
16. humidity
17. altitude
18. load
19. fuel temp
20. driver skills
21. wind and direction
22. current and direction
23. driveline losses
24. bottom finish
25. etc.
26. etc.
27. etc.
One can see that with all of the states and conditions that can affect a boats performance, an engine alone will not get it done! Dynos are great ways to test a motors output when operated to calibrated SAE standards and output values corrected properly, however the end result of how a motor performs in a boat is subjected to so many variables that one must be very careful to compare any two boats performance levels unless they are identical and in identical condtuions and states. Confusing and sometimes frustrating, there will never be a perfect boat motor, we just have to keep testing and trying!

The need for Speed! Its Magic !!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Ray @ Raylar

Re: dyno numbers
 

[QUOTE=RichardCranium572]Pressure drop varies depending on the acceleration rate of the engine.QUOTE]

I have heard this before but what does it mean? Just talking about air intake piping, not intake manifolds where all sorts of things are going on. If an air intake pipe/ filter/ intercooler/whatever flows a certain amount of air at a given pressure drop then it will flow twice that amount at roughly four times the pressure drop. Granted we measure these things at steady state on a flow bench, but why would the result be different if the pipe was on an engine that accelerated from flow1 to flow2 at different rates?

Re: dyno numbers
 

Great Thread...
I am about to start building my 4th BBC so I am most definitely a rookie.
Debates like this a vary informative, keep them coming... :drink: