E-penis size thread

[tsoob]

so basically what it sums up is dynapack wins again.

If you rolled up 200kw on st hitech, and drove to e&h motors, you would get the same power reading, and then on to glen sucklings dynapack you'd get the same

dynapack say there would be less than 1% variance between all their packs.

[Akane]

Wrong... operator will set a fixed rate for the dyno to run through the rpm range on a rolling road, a retarder provides the amount of resistance required to maintain that rate and reports to the software the tractive effort required, then calculates from there. Its much if a muchness, in terms of real world likeliness.... except the hub dyno is more accurate as the control is finer and more direct due to a solid link so the tyres only serve to compromise accuracy.

You've just said what I've said? :S

All dynos work on the basic principle of having a set resistance which the software calculates the time it takes to spin, unless you have one of the better hub dynos which you can set and HOLD the RPM which you can tune a specific load cell point. Something a rolling road cannot do.

except hub dyno is LESS accurate when it comes to knowing approximate what power you have available to the treads, because there's none? Might as well throw your car on it's brake discs and drive around.


If you are trying to say that the operator can $&#$% around what the resistance settings are, then yes all dynos can do that, unless you have one of http://wotid.com/dyno/ these dynos.

[iOnic]

All dynos work on the basic principle of having a set resistance which the software calculates the time it takes to spin, unless you have one of the better hub dynos which you can set and HOLD the RPM which you can tune a specific load cell point. Something a rolling road cannot do.

Some rolling roads are able to hold the RPM for steady state tuning. It's not just a hub dyno thing.

except hub dyno is LESS accurate when it comes to knowing approximate what power you have available to the treads, because there's none? Might as well throw your car on it's brake discs and drive around.

Sorry but I don't know how you can actually say hub dynos are less accurate than rolling roads. Tyres are a huge variable and one that isn't controlled or accounted for on rolling roads, There's no measurement of tyre distortion, inertia of the wheel and tyre, tyre temperature, temperature of the contact patch on the drum[s], tyre pressure etc even different brands and compounds of tyres have an effect. Also to maintain traction most cars have to be tied down very tightly with big strops which increases the loading on the tyres (again not accounted for) and what happens when strops stretch during the run - this affects the measured data but isn't accounted for.

In many cases you can actually see tyres shredding purely due to the amount of load that is being put on them - that doesn't happen in the real world, your tyres don't sit on a constant patch on the road with huge weight forcing them down and multiplying the load to prevent wheelspin.

The less uncontrolled variables you have - the more accurate your results will be. Don't be fooled, there's a really good reason behind hub dynos becoming more and more popular and having such repeatable results from run to run. I've worked with both and for run to run accuracy and repeatability - it's hard to beat a well set up hub dyno. I'm not particularly interested in the xxxKw number but the gains are where a dyno shows it's real accuracy.

[Akane]

You're all saying "ohh it's the times that matters" then you turn around and say "ohhh I just want an accurate as possible dyno reading and remove all the variable".

contradicting yourself. If it's all "ohh it's the times that matters", then why don't you say to yourself that it's the power available at the rubber that's all it matters?

As I said, you drive on rubber and not on the hubs.

You DO WANT to include that variable of rubber sizes / type / PSI of air inflated, size and shape / design of the wheels IN YOUR DYNO, to see what power that is available to you, when you drive, and unless you design a long treadmill that's made out of ashpalt, a big rolling metal pin is the closest you can get to knowing what power your engine will put down, to the rubber.

You might as well put your engine on an engine dyno and then turn around and said "oh I just want to know what times I'll get on the track".

can't be a hypocrite and win at the same time dude.

[iOnic]

I never said anything about times. I think you're mistaking me with someone else. Also

You DO WANT to include that variable of rubber sizes / type / PSI of air inflated, size and shape / design of the wheels IN YOUR DYNO, to see what power that is available to you, when you drive

If you DO WANT these things to be factored into the dyno run - why aren't they? There is no input to the rolling road dyno as to the tyre pressure, compund, shape, weight etc so how can it give accuracy based on variables it doesn't account for? Please explain that. Ignoring the changes in tyres is like ignoring atmospheric pressure and then claiming that your results are accurate - both have an effect on the load that the engine see's and therefore the accuracy of any power measurements you get. If you can't control or measure a variable, remove it. Simple science.

Hub dynos can calculate power available at the treads by entering wheel and tyre size so that the dyno can apply a correction factor - so your argument about not being able to tell power at the wheels from a hub dyno is flawed. It's not a perfect system but it's a damn sight better than loading up the tyres to prevent wheelspin which in turn applies extra load to the engine that isn't accounted for - and then saying that's an accurate way of measuring the engine's output....gimme a break.

If you are actually interested in accuracy of data then I'm sure you can come up with a better reasoning than "we don't drive on brake discs therefore it can't possibly be accurate". Based on your logic, engine dynos are pointless too.

[Akane]

There's no input such as tyre pressure compound shape weight on a rolling road, because it's actually there, you have it, it's called a rim and a tyre, real thing too! on your car! WOW!

Nope, I do want these variables on my dyno run because that's what I run on the streets. I want to know everytime I do a blast down the strip I have exactly X amount of power at the treads.

With a hub dyno you can enter wheel size calculations but what about the design of the wheel, the type of rubber wrapping around the said rims. Position of materials and the type of materials greatly affect the power it takes to spin it. No software simulation in this world can beat running the actual wheels against a dyno.

Hub dynos are great for putting mega amounts of power down and avoiding slippage. But I want to know I have exactly 300hp between the road and my car, not 315hp - my rims of unknown dimensions - tyres + magic dust + a bucket and a half of BS = amount of the power some software that's made up for 2000 lines of code thinks I have.

[iOnic]

I don't think you understand how dynos work or what their actual purpose is. You're purely interested in getting a particular number and being able to tell people that you got that number "at the wheels bro". You couldn't care less about how accurately that number reflects what's actually happening as long as you've got 300hp at the treads. For you, a dyno is less of a tuning tool and more of a penis measuring device.

Carry on.

[Mr.Phreak]

amount of the power some software that's made up for 2000 lines of code thinks I have.

How do you think a Dyno works??

[Akane]

I don't think you understand how dynos work or what their actual purpose is. You're purely interested in getting a particular number and being able to tell people that you got that number "at the wheels bro". You couldn't care less about how accurately that number reflects what's actually happening as long as you've got 300hp at the treads. For you, a dyno is less of a tuning tool and more of a penis measuring device.

Carry on.

Sure I don't. Just like how you thought some software made by a team of 2 can simulate wheel and tyre combo better than the real thing itself, because it's on a OMGZ HUBZ DYNO AU!

How do you think a Dyno works??

few lines of code is perfect for working out approximate power from the time it takes to spin up a roller, but to simulate wheel design and power loss from the composition of rubber.......? Not a chance.

[iOnic]

You seem to be really knowledgeable about how dynos are designed and how they work. How many different dynos have you had the opportunity of tuning/diagnosing vehicles on?

[Timmo]

Dont forget about it being a hot day...

True forgot that point.

Also don't forget "XX Kw on hub dyno, will have more power though as had shit tyres on so was probably slipping heaps"

I thought it went the other way- Nice sticky tyres will read lower because they stick to the rollers- For higher numbers it's better to run cheaper/harder compound.

[RomanV]

As everyone seems to agree on

Hub dynos dont count the differences that the wheels and tires make.

But that's all part of it, one person could have heavy as fark chrome wheels and deflated tires, another person could have light weight forged alloys and correctly inflated tires, another person could have wide wheels with low psi drag racing slicks on. they're all going to show different results, and this same difference is going to be reflected in the real world.

If all 3 of those people went to a hub dyno and got the same results, the'd likely be chuffed bout how they all had the same good figures. But the real world results would be different.

For tuning an ENGINE then a hub dyno is better I agree, but then an engine dyno is even better.
To account for as many real world variables as possible, (tuning your car as a whole?) I think rolling road is preferable.

In saying this, no dyno can measure transient throttle response, lag etc as dynos always seem to be run in a top gear under lots of load.

Neither a hub nor rolling road dyno can give you a meaningful difference between a highly responsive engine and a really laggy one.

The usefulness of dynos isnt just limited to comparison of runs from the same car, comparing differences to other cars with similar but slightly different setups can be useful as well. So long as run on the same dyno I guess.

[Bling]

Dont forget about it being a hot day...

True forgot that point.

Also don't forget "XX Kw on hub dyno, will have more power though as had shit tyres on so was probably slipping heaps"

I thought it went the other way- Nice sticky tyres will read lower because they stick to the rollers- For higher numbers it's better to run cheaper/harder compound.

[Akane]

You seem to be really knowledgeable about how dynos are designed and how they work. How many different dynos have you had the opportunity of tuning/diagnosing vehicles on?

None, but from what you have said, I believe that you might have tuned on a few dynos before and still don't know it from a bar of soap.

And what RomanV has said. Dyno your car as a whole, not part of it, include all the variables you have.

[iOnic]

Cool story bro Lith and I haven't got a clue what we're talking about People just seem to have this need to pay us to do this stuff and by some miracle of nature results are achieved. I'll forward them on to you from now on.

[Akane]

Then funny how I made the most power on the least amount of boost on standard cammed with the GT28RS and it was road tuned.

Just to show that because you own or have access to use something, doesn't mean you're know it all.

And yes the general concencious is that the TP dyno reads lower than the dynapak.

[iOnic]

Yeah you're the man. Dunno why tuning shops even exist since you've done it all and achieved far better results than anyone else.

[Akane]

Err I didn't road tune my car on the first time round, never said I did. But if you're trying to say that you know more than I do on tuning just because people pay you to do it, and you have access to some of the tuning tools that others don't, then you can't be more wrong.

[iOnic]

Cool story bro

[RomanV]

99% of times when people come to the dyno, it's when they've mashed together a whole bunch of bits, and they want the ECU tuned to suit the package they've assembled.

So they're not actually 'tuning' the cars setup at all, they're configuring it with the appropriate fuel and ignition advance to suit the cars 'tune'

It's not often that people often do 'tuning' via interchanging actual parts of the car, to make comparitive differences... costs a lot more money that way I guess, and you're potentially just as likely to take a step backwards.

In the first situation, where configuring the ECU is the goal, hub dyno is more accurate and more repeatable, no doubting that.

If I was getting an ECU configured (I dont think its right to call this tuning) then I'd prefer to get it done on a hub dyno, more to the point one that can hold at an RPM and load to tune for minimum ignition advance for best torque at several points under the curve, not just full throttle.

Doing a 'road tune' for light load and throttle is pretty rangy, compared to a proper dyno. But obviously a lot cheaper.