mopowers
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Which shop?
2 different dynos,2 very different numbers.why?
- Thread starter jdsduster
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Which shop?
604B1duster
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Pm sent
Bob Book
New Member
Different Dyno Manufacturers along with different Software can make big corrected power swings. I had Stuska with Depac until 2009 and went to a Superflow 902 with Win Din software - 1500 HP engines suddenly became 1400. That's why you should dyno at the same location once you have established a baseline for your engine and don't make your purchase decisions off dyno numbers. Check your potential engine builders record at the racetrack and remember an Engine Dyno is only a tool - and should only be taken seriously as a tool to track your progress if you're trying to update or evaluate that the rebuild didn't cost you any power. In the right hands it's a great tool - in the wrong hands it's a tool use to prop up artificial numbers that your racetrack performance will prove...
yellow rose
Overnight Sensation
yellow rose
Overnight Sensation
^^^^^^^^^^^^^^^^THIS^^^^^^^^^^ don't know how many times I've been told a dyno is worthless, a flow bench is worthless and now I'm hearing a spintron is worthless.
All ridiculous.
They are tools.
You can't have too many tools.
Just because your buddy uses his hammer to break an egg isn't the hammers fault.
use a tool correctly and it will tell you the truth. If you can't run on your truthful record, your customers will learn soon enough.
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justinp61
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I asked many times for this builder to post time slips, he never did.
As far as dyno's go they are a tool, just like a timing light or a vacuum gauge. If a person don't see the value in using one they probably will never build anything that needs to be on one.
Bob Book
New Member
Engine Dyno's are excellent tools - just very easy to manipulate and can vary 10% and more from one shop to another. You have to keep that in mind when relying on Dyno power numbers - and their accuracy - when making an engine purchase. Most of the bigger shops will have a well known reputation for a "Happy" Dyno if their numbers are inflated to the norm. As long as each shop uses the same formula and software when running an engine it can be an excellent tool - even if the numbers are suspect. My criticism is shops that openly advertise these wildly inflated power numbers and get work off of those numbers. As shop owners we all know where our respective dyno reads to the Industry norm so a disclaimer should always be included. IMHO....
604B1duster
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Oh boy
BigBlockMopar
BigBlockMember
Take the engine back to the first builder and have him dyno it again, just for comparison-giggles. ABA testing.
That's way you don't "compare" dyno's, you compare your before and after modifications on your engine.
That's way you don't "compare" dyno's, you compare your before and after modifications on your engine.
About 2 years ago, someone PM me about a 360 that he made a deal on with an engine shop that recently closed up. X amount of dollars for a 550 Hp stock stroke 360. The dyno sheet he got only showed just over 500 hp. He asked for a refund of x amount dollars since he did not get what he paid for. Several days later he got a new dyno sheet in the mail showing the engine made 545 hp with the comment that they had re calibrated the dyno and that no refund would be coming.....Should have saved those PMs.....
j par
Well-hung Member
Why in the heck would you disagree with my answer and then say exactly what I did? Anyways I just liked your post because you said what I did it's a tool and then someone else had this long answer that's it exactly what I did it's a "Baseline".
Honestly on this subject I'm going to completely go at the Yellow Rose and whatever he says. Even if he does say what I say lol because this is where bench Racers really really really really shine!
I have about 370 some horsepower to the back tires and I like to tell people that calculates up to about 475 or so? Anybody else want to hear honest numbers!? I think it was about 3100 lb and about 119 miles an hour? That was with me in the car at about 220.
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he would not honor his build(rings)and he has closed shop anyway.
yellow rose
Overnight Sensation
As I've said...these are tools. There are standards and if (a huge IF ) would all use the same SAE standards, and control for environment we would have all the disparity between dyno's and flow benches.
Same with micrometers. Good mic's come with a standard that is certified. Good machinists verify their mic's on a regular basis. There is absolutely three different machinists, using different mic's all set to a certified standard should have any more than a .0002 discrepancy at the most.
One big issued I've found over the years in the difference between crank and wheel dyno's is that most engine dyno's are in a controlled space so they don't use ambient air. Where a chassis dyno almost always uses ambient air.
Also, the engine dyno is often done with dyno headers that are much better than what goes in the car. The chassis dyno will use the headers that fit the car. Lots of guys have a dyno carb, a known working piece to establish a base line. That's all good. But you need to test with the actual carb to be used in the car, like a chassis dyno would.
Never overlook ignition systems. Engine dyno shops usually have an ignition system already on the dyno. It's usually a tricked up piece, or at least it's been well tested. On the chassis dyno you are dealing with the ignition system in the car. Who knows what the grounds are like, or the wiring in general.
As I've said before, testing, testing accurately is very expensive. A local dyno to me (way back in the day) were stumped when I brought in a brand new ignition to run with my engine on the dyno. We sorted everything out on his dyno then wired up my stuff, including the coil. The operator assured me that my ignition would be a power loser because his box was warmed up by a guru.
Big disappointment when my off the shelf ignition was better across all the RPM range.
You have to test like you intend to race of drive. Whoever coined the phrase paradise makes perfect was an idiot. If you continually practice, but practice incorrectly you will only get perfect in doing it wrong.
Perfect practice makes perfect. Doesn't matter if it's bowling, golf or building engines. Duplicate real world as close as you can and your results will correlate between the flowbench, dyno and track.
Same with micrometers. Good mic's come with a standard that is certified. Good machinists verify their mic's on a regular basis. There is absolutely three different machinists, using different mic's all set to a certified standard should have any more than a .0002 discrepancy at the most.
One big issued I've found over the years in the difference between crank and wheel dyno's is that most engine dyno's are in a controlled space so they don't use ambient air. Where a chassis dyno almost always uses ambient air.
Also, the engine dyno is often done with dyno headers that are much better than what goes in the car. The chassis dyno will use the headers that fit the car. Lots of guys have a dyno carb, a known working piece to establish a base line. That's all good. But you need to test with the actual carb to be used in the car, like a chassis dyno would.
Never overlook ignition systems. Engine dyno shops usually have an ignition system already on the dyno. It's usually a tricked up piece, or at least it's been well tested. On the chassis dyno you are dealing with the ignition system in the car. Who knows what the grounds are like, or the wiring in general.
As I've said before, testing, testing accurately is very expensive. A local dyno to me (way back in the day) were stumped when I brought in a brand new ignition to run with my engine on the dyno. We sorted everything out on his dyno then wired up my stuff, including the coil. The operator assured me that my ignition would be a power loser because his box was warmed up by a guru.
Big disappointment when my off the shelf ignition was better across all the RPM range.
You have to test like you intend to race of drive. Whoever coined the phrase paradise makes perfect was an idiot. If you continually practice, but practice incorrectly you will only get perfect in doing it wrong.
Perfect practice makes perfect. Doesn't matter if it's bowling, golf or building engines. Duplicate real world as close as you can and your results will correlate between the flowbench, dyno and track.
Go to the dyno and break in the engine, tune it to the max, ask for an honest reading because your curious, get the paper work and then through it away.
Your done, go out and play.
Your done, go out and play.
RAMM
Well-Known Member
It's way easier than most think. Look at and tune by RAW-uncorrected #'s, look at fuel consumed LBS/HR/BSFC.
For example: 550HP "uncorrected" would be 248 lb/hr fuel divided by the B.S.F.C (.45 in this theoretical case) at whatever the RPM was so= 248/.45 = 551.1hp
Then look at and understand the correction factor /C.F. and how that works. J.Rob
Brian Hafliger
Well-Known Member
For engine builders like myself and others, the Dyno is a great learning tool WHEN you compare that data with flow bench data, and real world at the track data...to customers the Dyno is a great way to get the engine broke in, check for leaks, fine tune the engine for the air it's breather on that particular day (baseline tuneup) and try a few things that might make more power like lash, timing, etc...saving some time at the drag strip possibly.
I've seen a poorly setup car (with incorrect front end alignment) make a good engine look bad...what do your calculators say about that???? Oh, NOBODY has a poorly setup chassis....LOL!
I've seen a poorly setup car (with incorrect front end alignment) make a good engine look bad...what do your calculators say about that???? Oh, NOBODY has a poorly setup chassis....LOL!
RAMM
Well-Known Member
Nevermind the bold part in this case-the OP is talking one engine dyno to another engine dyno. This gets way to convoluted when a chassis gets involved. I'm telling the OP what to look at if he can. J.Rob
604B1duster
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Haha, Touché
j par
Well-hung Member
The only answer to the op's question is YES.
Edit: but I do prefer post #9.
Edit: but I do prefer post #9.
Hemirunner
Well-Known Member
This statement assumes that everything for your particular car is optimized for the combo. Converter, gear, shocks, chassis stiffness, etc. To make a fair and accurate comparison you would have to optimize all of those for each combo. Just changing rear gear ratio will change that substantially on a chassis dyno. You can give 6 people identical wedges that made 700hp on the same engine dyno on the same day and have 6 vastly different timeslips at the track depending on their experience.
Great perspective.
It can be used for break in - but that can also be done on an engine stand for the same purpose. Using it as a tuning tool - that's what its for! The power it shows at various rpm is just a reference for whatever you are checking and changing.
Any of you who haven't seen this thread should check it out, -especially the first post. That one shows how much a really good tuner with experience can figure out on a dyno.
Motorsports Village • View topic - How a Wideband gets tricked to read wrong AFR
The rest is about widebands and combustion - which was Shrinker's main point, but what he figures out in that story would have been much more time, even a bit of tail chasing, if it hadn't been on a dyno. Also notice how many times peak horsepower is mentioned. lol.
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RAMM
Well-Known Member
I had an experience a couple of years ago on the dyno with an engine I didn't build and what it did and how it acted was a real head scratcher. I should describe exactly how it was acting and then post up all of the data and see if anyone can figure it out. The customer left with the engine and a couple of days later I called him up and told him what to look for-I was amazed that the dyno was able to tell me what was going on. Basically halfway through the 2nd pull it would drop 50-60hp. The first pull was something like 380hp and every other pull was 330hp or something like that. In the car this guy would have never ever ever figured it out.
Moral of the story is the dyno should be used for many other reasons and oddly enough HP/TQ is one of the last. J.Rob
lil red
Well-Known Member
Good read fellas, lots here i didnt realize
I did QA work for a machine shop a couple years back (we actually had an old Heenan and Froude water brake dyno for our marine engine testing/calibration) and our mics / measuring equipment /manufactured parts were calibrated and kept in temp controlled environment as per ISO regs., so that (as yellow rose stated) the repeatability/reliability of the measurements were maintained to a small percentile.
my point is cant a dyno be calibrated for repeatability and wouldnt an owner want the equipment to be accurate? just wondering?
We calibrate everything in our current shop that does a quantative measurement - mics, surface finish testers, verniers, precision levels, electronic dials, weight dyno scales , precision squares, etc.
most pieces of precision measuring gear are calibrated or set to a known standard, micrometers, surface testers are first run over a known piece of surface finish to calibrate, electronic levels calibrated on a flat surface before use, hardness testers on a known rockwell hardness, blah blah
anyway isnt there a known resistance or baseline that an engine dyno would be first 'setup' to or calibrated to before an engine pull?
I did QA work for a machine shop a couple years back (we actually had an old Heenan and Froude water brake dyno for our marine engine testing/calibration) and our mics / measuring equipment /manufactured parts were calibrated and kept in temp controlled environment as per ISO regs., so that (as yellow rose stated) the repeatability/reliability of the measurements were maintained to a small percentile.
my point is cant a dyno be calibrated for repeatability and wouldnt an owner want the equipment to be accurate? just wondering?
We calibrate everything in our current shop that does a quantative measurement - mics, surface finish testers, verniers, precision levels, electronic dials, weight dyno scales , precision squares, etc.
most pieces of precision measuring gear are calibrated or set to a known standard, micrometers, surface testers are first run over a known piece of surface finish to calibrate, electronic levels calibrated on a flat surface before use, hardness testers on a known rockwell hardness, blah blah
anyway isnt there a known resistance or baseline that an engine dyno would be first 'setup' to or calibrated to before an engine pull?
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