Dyno Shortcomings - When Dyno tunning

[Pinkfluffybunnys]

Chassis dynos measure the amount of power being developed at the wheels over a range of engine speeds, recorded at steady-state full throttle. That’s great, but it often tells you little about on-road performance – and invariably, little about the subtleties of good driveability.

For example, what does a dyno chart tell you about the action of a turbo boost control? In short, almost nothing at all.

Here’s why:

1) The dyno acceleration rate in each gear is not representative of what is achieved on the road. This one’s a killer because boost overshoot on transients is hugely affected by the rate of engine rpm increase.

2) Very few people do full throttle gearshifts on the dyno. You know, race up through the gears – to the redline, change gears, to the redline, change gears. Again, it’s in just these conditions that you look for boost overshoots and/or slow increases back to peak boost after each gear-change.

3) I have never seen anyone do a full-bore launch from a standstill on a dyno. And how quickly boost can be brought up in these conditions – ie controlling wastegate creep – is a major aspect of good boost control.

4) On a dyno the intercooler never works as well as on the road, so the actual peak boost is likely to be different in those systems that don’t use boost pressure feedback.

5) On the dyno people never bother trialling all the different combinations of throttle position, load and engine rpm that you’ll find in half an hour on the road.

And it’s not just boost controls. Most dyno operators don’t start a run at very low rpm, so the engine revs being used most often in daily driving are not tested. The ‘area under the power curve’ (especially at part throttle) is ignored, while aerodynamic pressures (eg on the engine intake and intercooler) are all wrong.

A dyno is a great tool. But unless it’s inside a climate-controlled wind tunnel, can replicate all the different acceleration rates and inertial characteristics of the driveline, and operates on real world drive cycles, it’s only a starting point.

What a dyno is good for is engine management tuning for maximum power – and even then, this must always be followed by extensive road testing.

In short, when you’re doing on-road testing, you do not want an ‘on-road dyno’ – instead you want to test road car performance!

Thanks AutoSpeed

[Gary57]

When you on a dyno you are not there to sort out the acceleration transients, you generally turn all enrichments off when on a dyno. A dyno is a simple tool to help you tune fueling and timing maps safely, it is not safe to tune the 5500rpm max load site on the road (especially in a fast car) because in order to get that site in steady state you need 4th gear and that is close to the 200kmh mark.

Part throttle is used when dyno tuning in order to get the required load site.

I prefer road tuning because I can simulate every day use, but I can tune a car on a dyno in half the time it will take on the road and it would be safer too. The dyno is there for the basics, once the basics are there then you can go on the road and sort out the transients and stuff.

Tuning a timing map against a knock sensor isnt the best way either because when the motor knocks and you pull back 2 degrees timing you may only be making 1hp more than if you pulled it back 5degrees, I would rather pull it back more and be safer.

Dynos have there own place when tuning.

[Pinkfluffybunnys]

When you on a dyno you are not there to sort out the acceleration transients, you generally turn all enrichments off when on a dyno. A dyno is a simple tool to help you tune fueling and timing maps safely, it is not safe to tune the 5500rpm max load site on the road (especially in a fast car) because in order to get that site in steady state you need 4th gear and that is close to the 200kmh mark.

Part throttle is used when dyno tuning in order to get the required load site.

I prefer road tuning because I can simulate every day use, but I can tune a car on a dyno in half the time it will take on the road and it would be safer too. The dyno is there for the basics, once the basics are there then you can go on the road and sort out the transients and stuff.

Tuning a timing map against a knock sensor isnt the best way either because when the motor knocks and you pull back 2 degrees timing you may only be making 1hp more than if you pulled it back 5degrees, I would rather pull it back more and be safer.

Dynos have there own place when tuning.

Slow down there gary, Giving me a headache

Im glad you said it , Road tuning plays a very very important role for example in my car it took me 3 months of logging my work and home trip to get my AFR’s and timing to a point where I was happy with good economy. Light load and boost transition was also difficult.

I am more helping the other fourm guys out just because your gotech,Mr Turbo .. ect was tuned for two hour on a dyno doesn’t mean it’s the best it can be also if you read through the flaws plus take into account that almost 70% of dyno tuned car knock on the road during light load it makes you wonder

[Gary57]

I can almost gaurentee you that you can get a car smoother on a road than a dyno, road tuning is super important but takes time, time that isnt for free.

Think of it from the tuners side, he can tune a car in 45mins on a dyno or 3 hours on the road. They charge R1200 for a dyno tune that means you must pay R4800 for a road tune. No one will pay that for a normal tune so they choose to dyno tune them and get there money. Its a business and they out to make money that is all.

[Pinkfluffybunnys]

Your just angry today.

I can almost gaurentee you that you can get a car smoother on a road than a dyno, road tuning is super important but takes time, time that isnt for free.

Think of it from the tuners side, he can tune a car in 45mins on a dyno or 3 hours on the road. They charge R1200 for a dyno tune that means you must pay R4800 for a road tune. No one will pay that for a normal tune so they choose to dyno tune them and get there money. Its a business and they out to make money that is all.

I don’t get this statement, I know road tuning is better its a given I even said it in my last post and you know its better as you said but then why say go for the dyno tuning its cheaper?

That like giving your engagement ring to a flee marker jeweler to be made smaller its not like we are fitting a set of mag's , Your engine spends 90% of its life in the zone under the graph where most dyno tuners don’t even spend 20 minutes tuning, I don’t understand the logic I would rather take 1 hour dyno , 1hour road if I dint know how to tune my car and just pay the tuner for the time but what good fuel economy and low to mid range torque when peak power is so strong

[RB25SX]

2) Very few people do full throttle gearshifts on the dyno. You know, race up through the gears – to the redline, change gears, to the redline, change gears. Again, it’s in just these conditions that you look for boost overshoots and/or slow increases back to peak boost after each gear-change.

3) I have never seen anyone do a full-bore launch from a standstill on a dyno. And how quickly boost can be brought up in these conditions – ie controlling wastegate creep – is a major aspect of good boost control.

Watch this
http://www.youtube.com/watch?v=V-_kM7S0hDY

[Gary57]

I was just explaining why tuners choose to tune on a dyno and not the road.

When I dyno tune a car I tune the entire map not just WOT. If the car has a MAP sensor it is even easier to get it smooth.

[Pinkfluffybunnys]

I was just explaining why tuners choose to tune on a dyno and not the road.

I know why, its also cheap plus they dont need to take the time.

When I dyno tune a car I tune the entire map not just WOT. If the car has a MAP sensor it is even easier to get it smooth.

Why would a MAP be any easyier?

Watch this
http://www.youtube.com/watch?v=V-_kM7S0hDY

Sorry RBSX cant do you tube at work, will check at home

[Gary57]

I know why, its also cheap plus they dont need to take the time.

Yip...

A map sensor is alot easier because directly relationed to VE where as TPS isnt, a MAF would be the same as MAP. You CANT tune a turbo car on TPS as load, it is never smooth.

[Pinkfluffybunnys]

You CANT tune a turbo car on TPS as load, it is never smooth.

?!? Sorry but that’s obvious, MAF plus TPS will be just as easy as MAP plus TPS.

I personally thick MAF would be easier as it will correct better for ambient changes but this is not related to this topic.

But you will still get differential fueling in cells based on load that can only be seen on the road, this still begs me to ask why most cars are tuned on a dyno and not at least one hour on the road logging AFR/Boost/RPM inputs. I think the answer is money but then why cut corners here

[KD21sx]

i think u 2 should open up your own place......

[Sokar]

i think u 2 should open up your own place......

I think they should just get married? Hey Chuck and Larry???

[veecee]

lol - reminds me of the monty python skit, where the dude comes in to the place, for an argument.

dude 1: is this arguments?
dude 2: no
dude 1: but the sign on the door says arguments?
dude 2: no it doesn't...

and so on!!!

hehehe...

[Pinkfluffybunnys]

LOL...

Just getting my pint accross

[veecee]

i know, just pulling your leg dude!