Dynos and the real world

[chickenstrip]

You often hear of folk seemingly proud of a read-out obtained from a dyno run of their bike, especially if they've had a bit of tuning or remapping done to it. But how closely does this illustrate what's going on in the real world, when the rubber hits the tarmac? How accurate a dyno figure does anybody actually need?

Once the wheels are turning on road or track, you've got air pressure into the airbox, which is in itself tuned to optimise air flow on a high performance bike. Maybe you even add forced induction: a turbo or supercharger or ram air, which takes the importance of all that air pressure up another notch or two (or maybe I've got that the wrong way round as far as turbo and superchargers are concerned, and such systems actually reduce the importance of the moving bike?). So if you were to measure power and torque curves on a bike being maxed out on the road or track, surely things would look a great deal different, and those dyno runs would count for pretty much nothing?
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[Pete.]

The power figures are mostly bragging rights. If you put a datalogger on a high powered bike you'll find that your everyday rider uses 10% throttle most of the time. Full throttle (which is where the bragging comes from) is rarely used on the road.

It can be a useful tool if you change out your exhaust system which on a fuel injected bike will make rich and lean spots in the curve (more rich than lean in many cases). Mapping out those spots can improve both the mid-range and the fuel consumption along with improving the overall delivery.
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a.k.a 'Geri'

132.9mph off and walked away. Gear is good, gear is good, gear is very very good

[jeffyjeff]

The thing about a dyno run is that the results are objective. On XX date and time with XX ambient temperature and XX barometric pressure and at XX humidity, the engine produced XX torque at XX rpm, resulting in XX horsepower. The beauty of that objectivity is that the technician can assess the results of his/her tuning efforts or map changes in real, measurable terms.

On the road, the bikes performance is overly influenced by the skills of the rider. How many of us regularly take full advantage of all the power our bikes are capable of? Unless you are riding a 125 or maybe a 250, not many.
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History shows again and again how nature points out the folly of men - BOC

[Polarbear]

The only bike I ever put on a dyno was my busa after I put aftermarket silencers on it. The dyno bloke said it was a slight improvement on stock.

I'm sure I could feel every one of those 3 extra horses on top of the 170 odd the standard bike produced.
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Triumph Trophy Launch Edition

[wr6133]

Dyno runs are illustrative of the bikes change over stock. Ideally you'd have a before and after of the bike done on the same dyno in the same conditions (ideally).

It's a (theoretically) controlled environment so you can make a comparision Vs pre-tuning figure, book figure, some other bike on same dyno figure, etc.

How else would you compare? Lining up on an airstrip is not really a reliable way to measure.

[The Shaggy D.A.]

[redeem ouzzer]

I love fiddling on the dyno, but unless you always use the same dyno it’s as much use as tits on a fish. I especially enjoy playing with ignition maps back to back and seeing losses / gains from run to run (same with carb setup), it’s a major buzz seeing gains (or losses). Also I don’t care what people say, it’s impossible to set up AFR properly without dyno time.

Plus you can do cool stuff like quantify why a £700 quid set of pipes are shit.

https://farm8.staticflickr.com/7922/46890984801_920aa618a1_z.jpg
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Be a REAL MAN!

[Polarbear]

[ThatDippyTwat]

The curve is far more important than the numbers anywhere that isn't a drag strip.

It's no good having 200+ ponies if you cant use them properly. I've ridden some older GSXR based bored/turbo'd bikes putting something like 200 out, and I've ridden a Ducati V4S. The former were by and large un-rideable on the street, you would feel wiped after a short journey trying to keep it all in check. The Ducati is a dream in comparison, though still something to be respectful of. We have the technology to make the power manageable by mere humans these days, and it was either non-existent or unobtainable beck then.
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'98 VFR800 (touring) - '12 VFR800 Crosrunner (Commuting) - '01 KDX220 (Big Green Antisocial Machine)

[Easy-X]

Can't remember who's car it was on YouTube but they took their little shit box and put on better laid out steel headers (you have the variety of 4 into 1, 4 into 2 into 1, even vs uneven lengths etc.) and you could see from the dyno that the low end of the curve had a dip. The headers sorted it right out, quite surprised how effective they were.

Dynos are much more visual at getting a point across. If you've got something nagging at you about real, street performance they might reveal something you'd not been able to adequately describe previously.
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Husqvarna Vitpilen 401, Yamaha XSR700, Honda Rebel, Yamaha DT175, Suzuki SV650 (loan) Fazer 600, Keeway Superlight 125, 50cc turd scooter

[MCN]

I use full throttle quite regularly when the need and conditions exist. 😎

A dyno test is just another tool.

People even brag that they get their shite serviced at the dealership. 🤣


But as mentioned, it is a more exact method of comparison than time to ride a big steep hill near where you stay.
Before phaph and after phaph is important.
Or if a need for phaph is suspected.

Ultimately competition industry makes most use of them.

Manufacturers also use them for post-repair load testing. For many reasons, insurance is one reason.
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Disclaimer: The comments above may be predicted text and not necessarily the opinion of MCN.

[spottedtango]

A dyno is basically just to check you still have your 33bhp restrictors in.

[chickenstrip]

[MarJay]

I've had my Street Triple R set up on the dyno... It's not for maximum power.

It did gain a couple of horses at the top end, but to be honest that's not what I wanted. I wanted a smoother, more direct throttle response and to ensure the fuelling was right throughout the range. Apparently Triumphs are usually rich at the bottom end and lean at the top. This is exactly what my bike was like. Also I had the Arrow full system to contend with.

This did all get sorted by the dyno setup, and now my Street is very lairy and the connection to the twist grip is much more direct. I love it, it's exactly what I wanted. It was well worth the money.
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British beauty: Triumph Street Triple R; Loony stroker: KR1S; Track fun: GSXR750 L1; Commuter Missile: GSX-S1000F
Remember kids, bikes aren't like lego. You can't easily take a part from one bike and then fit it to another.

[Pete.]

[chickenstrip]

[Polarbear]

[wr6133]

[chickenstrip]

It seems they wasted their time and money then

They should have stuck with turbochargers. When I wrecked the turbo on my 750 turbo and sourced a second hand replacement, when I first tried the repaired bike out, it was gutless, presumably because the replacement turbo had sat around for a while and the impeller had got gummed up a bit with old oil (?). Only took a couple of miles for it to get up and running properly though. But without it, you have a heavy 750 with very low compression, 7:1 or something like that, slow as feck.
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THERE'S MILLIONS OF CHICKENSTRIPS OUT THERE!

[The Shaggy D.A.]

[MCN]

[Pete.]

[chickenstrip]

Ok, I think it has clicked. Air intake systems on normally aspirated bikes are designed to ensure that changes in air pressure surrounding a moving bike do not alter how it performs, but rather are designed to isolate the intake from such external effects. Correct?
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Chickenystripgeezer's Biking Life (Latest update 19/10/18) Belgium, France, Italy, Austria tour 2016 Picos de Europa, Pyrenees and French Alps tour 2017 Scotland Trip 1, now with BONUS FEATURE edit, 5/10/19, on page 2 Scotland Trip 2 Luxembourg, Black Forest, Switzerland, Vosges Trip 2017
THERE'S MILLIONS OF CHICKENSTRIPS OUT THERE!