Crank hp variations

[ImBetterDude]

Hey all,

Know dynos have tons of variance, but do identical blower kits vary kit to kit?

For example, should all P2 727 kits produce roughly (within 10 hp) the same crank hp?

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[80FoxCoupe]

Hey all,

Know dynos have tons of variance, but do identical blower kits vary kit to kit?

For example, should all P2 727 kits produce roughly (within 10 hp) the same crank hp?

Nope.

 

[ImBetterDude]

Can you elaborate? Don't even know if "nope" means you don't think output should vary, or you don't think they should all be within a percent or two of each other.

 

[Angrey]

Hey all,

Know dynos have tons of variance, but do identical blower kits vary kit to kit?

For example, should all P2 727 kits produce roughly (within 10 hp) the same crank hp?

Yes and no.

Firstly, all dyno's have a measure of accuracy, like any instrument. That means you could run the same car, on the same dyno under the SAME conditions and there'll be a variance of outputs for a few hp. Keep in mind that these measurements even on the same equivalents increase with variability the higher hp.

Secondly, 2 different dyno operators can have an impact on the output, how they strap the car down, whether they set or demand the same tire pressure, where they place the cooling fans, etc.

Then there's comparing dyno's, depending on where the temp/pressure sensor is located, etc, all can play a part.

But for the purposes of our discussion, let's assume EVERYTHING is EXACTLY the same, same operator, same exact dyno setup, same exact conditions (this is the most difficult to equate from one dyno to another or even the same dyno on different days), the output SHOULD be within a few hp consistently. When OEM's do their engine dyno testing, if it falls outside only a few hp one way or the other, it's rejected.

But to answer your question fully, no, outputs should be very similar, but in reality, even on the same dyno (on different days, with SAE correction) stuff can vary.

What I'm saying is the same stuff can swing pretty wildly depending on a lot of the differing factors discussed above. But in theory, 2 blowers should be very very close to one another in output, efficiency and losses.

 

[ImBetterDude]

Yes and no.

Firstly, all dyno's have a measure of accuracy, like any instrument. That means you could run the same car, on the same dyno under the SAME conditions and there'll be a variance of outputs for a few hp. Keep in mind that these measurements even on the same equivalents increase with variability the higher hp.

Secondly, 2 different dyno operators can have an impact on the output, how they strap the car down, whether they set or demand the same tire pressure, where they place the cooling fans, etc.

Then there's comparing dyno's, depending on where the temp/pressure sensor is located, etc, all can play a part.

But for the purposes of our discussion, let's assume EVERYTHING is EXACTLY the same, same operator, same exact dyno setup, same exact conditions (this is the most difficult to equate from one dyno to another or even the same dyno on different days), the output SHOULD be within a few hp consistently. When OEM's do their engine dyno testing, if it falls outside only a few hp one way or the other, it's rejected.

But to answer your question fully, no, outputs should be very similar, but in reality, even on the same dyno (on different days, with SAE correction) stuff can vary.

What I'm saying is the same stuff can swing pretty wildly depending on a lot of the differing factors discussed above. But in theory, 2 blowers should be very very close to one another in output, efficiency and

Yes and no.

Firstly, all dyno's have a measure of accuracy, like any instrument. That means you could run the same car, on the same dyno under the SAME conditions and there'll be a variance of outputs for a few hp. Keep in mind that these measurements even on the same equivalents increase with variability the higher hp.

Secondly, 2 different dyno operators can have an impact on the output, how they strap the car down, whether they set or demand the same tire pressure, where they place the cooling fans, etc.

Then there's comparing dyno's, depending on where the temp/pressure sensor is located, etc, all can play a part.

But for the purposes of our discussion, let's assume EVERYTHING is EXACTLY the same, same operator, same exact dyno setup, same exact conditions (this is the most difficult to equate from one dyno to another or even the same dyno on different days), the output SHOULD be within a few hp consistently. When OEM's do their engine dyno testing, if it falls outside only a few hp one way or the other, it's rejected.

But to answer your question fully, no, outputs should be very similar, but in reality, even on the same dyno (on different days, with SAE correction) stuff can vary.

What I'm saying is the same stuff can swing pretty wildly depending on a lot of the differing factors discussed above. But in theory, 2 blowers should be very very close to one another in output, efficiency and losses.

I think I understand and agree with where you're going with this post.

Okay, so then would you also agree that (unless you've got a very exotic build I guess) that paying $100 for a dyno pull is kind of an exercise of futility? Unless I guess you've got reason to believe a component is defective and you want to check output isn't wildly off, but even then most often you'll throw a code or there's some less expensive and more precise way to diagnose an issue than a dyno pull.

I guess the thesis I'm working towards is that all you're going to be buying for your $100 dyno day is satisfaction or disappointment over whichever direction variance happens to swing you; that your car produces more or less exactly what it should based on your components, and hitting numbers 15% above or below that (or whatever the standard deviation might be for dynos) is more or less meaningless.

 

[Jackson1320]

If you Have the exact same kit on two identical cars then yes they should be close. It’s rare to see the same kit on two identical cars. people use different brand headers, different exhaust system, there is a lot of variables. different intercoolers,different belt size, mileage on the car, tires, and so on

 

[Angrey]

I think I understand and agree with where you're going with this post.

Okay, so then would you also agree that (unless you've got a very exotic build I guess) that paying $100 for a dyno pull is kind of an exercise of futility? Unless I guess you've got reason to believe a component is defective and you want to check output isn't wildly off, but even then most often you'll throw a code or there's some less expensive and more precise way to diagnose an issue than a dyno pull.

I guess the thesis I'm working towards is that all you're going to be buying for your $100 dyno day is satisfaction or disappointment over whichever direction variance happens to swing you; that your car produces more or less exactly what it should based on your components, and hitting numbers 15% above or below that (or whatever the standard deviation might be for dynos) is more or less meaningless.

Pretty much. Like guys that do their car on "dyno day" when it's bone stock.

My opinion is that dyno'ing the car for anything other than very rough tuning purposes is just a dick measurement anyway. Road/street tuning and datalogging is the most effective way to dial in a car and putting it on a dyno is either for a very brand new setup where you're worried about initial tunes or just bragging rights. Vendors and manufacturers HAVE to do dyno for demonstration and marketing, but at the end of the day, unless you're going to tweak the tune, getting a number is just an ego thing.

There are other aspects, (like dialing in/rough tuning a car in a controlled environment where doing WOT pulls to redline on the street can be....problematic). But at the end of the day, the only thing that matters is how the car performs (on the street/strip) and dialing it in with real world conditions (like the hood being closed, outside air rushing through the engine bay at increased speed, actual weight and inertial loads on the power train, etc). You can get a sense of whether the car is under optimal tune without a dyno (by logging).

 

[ImBetterDude]

My opinion is that dyno'ing the car for anything other than very rough tuning purposes is just a dick measurement anyway.

I don't even mind dick measuring!

But if you've got a ruler and know your dick is 7.42", then what possible reason would you have to pay someone $100 to measure your dick with their "ruler" which you know 100% for a fact will measure your dick incorrectly by up to plus or minus an inch?!

 

[Angrey]

I don't even mind dick measuring!

But if you've got a ruler and know your dick is 7.42", then what possible reason would you have to pay someone $100 to measure your dick with their "ruler" which you know 100% for a fact will measure your dick incorrectly by up to plus or minus an inch?!

using your example, you don't know for sure, you've only been told that 200 of your clones have a dick that's 7.42" and until you measure it, your small ego will bother you until you confirm it.

 

[ImBetterDude]

I mean running with this analogy there really should be dyno operators who deliberately skew their dyno numbers positive so they get a reputation of giving dudes the kinds of dick numbers they're looking for. Like they should feign being objective, but rig their machines to just produce inflated results to satisfy the masses of insecure dude bros.

 

[Angrey]

I mean running with this analogy there really should be dyno operators who deliberately skew their dyno numbers positive so they get a reputation of giving dudes the kinds of dick numbers they're looking for. Like they should feign being objective, but rig their machines to just produce inflated results to satisfy the masses of insecure dude bros.

Well, not to indulge in conspiracies, what really matters is the delta or change on a dyno output. That's indicative of the desired effect.

Take for instance mustang dyno's, which are known as the "heartbreaker" everyone knows it spits out lower numbers, but it's still effective at telling you how much you improve over a baseline.

But yeah, if you've got a dyno queen and you want to brag, there's some places you avoid (like mustang dynos) and of course there's always accusations that some tuners "fudge" to try to sell services.

I don't like the whole dyno game. I think it's a bit gimmick, but it is a useful tool if you're putting together a brand new combination a tuner has never setup before. But with modern technology, street tuning/logging is much better (and should be done even after a dyno tune anyway).

 

[Angrey]

For instance, if I wanted to "pump" numbers on my own custom intake side or exhaust side component. I'd run a stock baseline. For the baseline I'd take the tires down to 19 psi. I'd place the fan further away from the car (or even turn it to a lower setting). I'd either move the temp pressure sensor or force it to read as low as possible. I'd run the car on a few runs and start my "baseline" run with a warm motor.

Then for my product dyno, I'd tweak the hell out of it. Let the motor fully cool, place the fan as close as I could (and turn it up), I'd increase the tire pressure as much as possible without getting spin. Hell some guys even play tricks on the settings that account for spin (which you can't see on the dyno sheet).

so what would be say a 15 hp improvement all things being equal, I can show a 27 hp improvement just by monkeying with simple stuff like starting temp, tire pressure, input settings....none of which the public will see on the dyno sheet. I'd even publish in STD smoothing 5 (opposed to SAE) which there are still people (a few) that don't know the difference.

Of course, I'd sell a bunch until aftermarket shops and tuners started doing their own independent tests and videos.

Perfect example would be naked intakes. They do really well on a dyno (with the hood open and a fan blowing on them). But in the real world, the hood is closed and the engine bay is hot. So while enclosed intakes might not breath as well, because modern cars are so sensitive to IAT, they end up performing better. But to the uninformed, they'll point to dyno sheets that show naked intakes are better.

 

[ImBetterDude]

For instance, if I wanted to "pump" numbers on my own custom intake side or exhaust side component. I'd run a stock baseline. For the baseline I'd take the tires down to 19 psi. I'd place the fan further away from the car (or even turn it to a lower setting). I'd either move the temp pressure sensor or force it to read as low as possible. I'd run the car on a few runs and start my "baseline" run with a warm motor.

Then for my product dyno, I'd tweak the hell out of it. Let the motor fully cool, place the fan as close as I could (and turn it up), I'd increase the tire pressure as much as possible without getting spin. Hell some guys even play tricks on the settings that account for spin (which you can't see on the dyno sheet).

so what would be say a 15 hp improvement all things being equal, I can show a 27 hp improvement just by monkeying with simple stuff like starting temp, tire pressure, input settings....none of which the public will see on the dyno sheet. I'd even publish in STD smoothing 5 (opposed to SAE) which there are still people (a few) that don't know the difference.

Of course, I'd sell a bunch until aftermarket shops and tuners started doing their own independent tests and videos.

Perfect example would be naked intakes. They do really well on a dyno (with the hood open and a fan blowing on them). But in the real world, the hood is closed and the engine bay is hot. So while enclosed intakes might not breath as well, because modern cars are so sensitive to IAT, they end up performing better. But to the uninformed, they'll point to dyno sheets that show naked intakes are better.

I could google it, but I assume crank hp figures aren't something we're able to attain because it's impossible to do with the engine not removed from the car?

 

[Angrey]

I could google it, but I assume crank hp figures aren't something we're able to attain because it's impossible to do with the engine not removed from the car?

There's pretty good data/assumptions for drivetrain loss. They know what the motor dyno'd from the factory engine dyno and there's quite a bit of data on bone stock chassis dyno's so there's pretty good indication of what the drivetrain is consuming.

 

[ahl395]

it will vary based on 100 different factors. The dyno, ampbient temp, correction factor, smoothing setting, tires, tune, belt tension, etc etc.

Even the same car on two different dynos can read vastly different. So the same kits on different cars on different dynos certainly will.

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