How to read dyno graphs

Hennie Marais · Post by **Hennie Marais** » Thu Mar 15, 2007 8:00 am

I hope that was not aimed at me, I'll wait for a reply before I say something.

Vlade · Post by **Vlade** » Thu Mar 15, 2007 8:19 am

Good one Duane

What causes power loss through the drive drain? Or rather what can be done to increase power to wheels?

I know that on the S13/S14 even S15 guys go for 1 piece prop shafts and also lighter aluminum ones to increase power to wheels. What else can be done? (For interest sake only, got other priorities

)

Gary57 · Post by **Gary57** » Thu Mar 15, 2007 8:39 am

How do you calibrate the power from the wheels to the flywheel?? Do you measure the diameter of wheels to change the tractive effort into torque on the wheels?? Agian how do you calibrate the torque from the wheels to torque on the flywheel??

If you ask me; to do this you would have to know the efficency of the drive train.

qewrty · Post by **qewrty** » Thu Mar 15, 2007 9:22 am

Hennie Marais wrote:I hope that was not aimed at me, I'll wait for a reply before I say something.

I think it was for everyone's benefit. Especially me and Woohaa..

Draco · Post by **Draco** » Thu Mar 15, 2007 1:50 pm

Here is my last dyno sheet, don't be nasty...., Duane how does my grafs look? He didn't stop on 5000 and 5500 to put in the figures, he was abit in a hurry, see the Grafs . This is what I read about the "What is this" thingy(secondary butterfly system) that comes with the 8port head.....this might explain my torque?
Basic Theory of Operation
The amount of fuel and air sucked/forced into a cylinder is dictated by several factors, one of which is charge velocity. Higher velocity means more gets in. At low RPMs, you usually aren't generating much boost, and since you don't have much displacement, you're not sucking much either. A larger opening lets the charge in slower, a smaller one faster. Think of a garden hose: just holding the hose out, the water comes out at a decent rate, but it's in no real hurry. Press your thumb over the opening to restrict the exit area, and flow velocity must increase, for flow to be maintained. At some point, you are restricting total theoretical flow, but at lower flow levels, this will cause a higher exit velocity. The same is true with the CA18DET's secondary butterfly system. At lower airflow points (i.e. RPM), the butterflies are closed, forcing nearly all intake charge to go through half the space, increasing its velocity into the cylinder and therefore the rate at which the cylinder fills. More charge = more power, all else being equal.

The Calibrator · Post by **The Calibrator** » Thu Mar 15, 2007 7:01 pm

Hennie that was not aimed at you at all.
Gary57 the dyno "measures" the rolling losses on the coastdown its nowwhere near 100% accurate.
I only use it to account for changes in rolling losses as the gearbox and diff temps change.

Its possible to see a 5kw gain on the wheels without doing anything except warm the hearbox, diff and tyres up.

Draco your torque figures are not engine torque at all. I have noticed before when using Dateks software that the torque figures are very high I am not sure exactly what calculations they use to arrive at those figures but they are meaningless when compared to another dyno or as absolute figures.

AS I said to you before compare what you had before and after on the same dyno.

veecee · Post by **veecee** » Fri Mar 16, 2007 7:18 am

the drivetrain losses. i was discussing this the other night.

i've heard its measured after the power run on a load dyno, while the car is decelerating. like calibrator said on the "coastdown".

but how do you set up a load dyno? i ask this because someone mentioned that you are supposed to set the car's weight so that the dyno "loads" that factor into the power run.

for example:

if a car weighs 1.3 tons, it will have a certain inertia, or resistance to movement. calibrator you could probably explain this better than i could. this will be higher than a car that only weighs 1 ton.

so if you tell the load dyno that a 1.3 ton car weighs only 1 ton, and you do a power run, then you will get a higher power figure than if you told the dyno it was a 1.3 ton car.

also - if you set the load to the equivalent for a 1.6 ton vehicle, then you will get a higher power figure. i was told its a similar concept to the resistance setting on an exercise bike for example.

is this theory correct?

Hennie Marais · Post by **Hennie Marais** » Fri Mar 16, 2007 8:11 am

The Calibrator wrote:Hennie that was not aimed at you at all.
.

Oh ok, sorry if I took it up the wrong way.

Draco · Post by **Draco** » Fri Mar 16, 2007 8:41 am

Forgetting the figures on the sheet, how does the curves on the grafs look, to me it seems quite smooth whitch I think is good then or am I wrong.

widowmaker · Post by **widowmaker** » Fri Mar 16, 2007 9:21 am

has everybody here still got the standard final drive ratios?
to me it would be more important to get to say 180 quickquick than to be able to say that I have done 240 once or twice (or maybe 6 times, or 9 )
disclaimer : of course these runs were conducted by a professional under controlled circumstances on a prepared high speed oval race track
of course!

Draco · Post by **Draco** » Fri Mar 16, 2007 9:26 am

It just hit me, I am now heavy dissapointed, I will never know what figure my car does, nor will anyone else, claiming your car does 200kw meens f*ckall because you can not compare dynos, you can't compare figures, your car can do 120kw here, 200 there 150 somewhere else.....who's dyno is right or is there no such thing as an accurate dyno...it seems not.

It seems a dyno is only good enough to show if you improved on a dyno from your 1st run to the last tuned run. Great I improved with 20kw....from where...from 80...100....so how strong is your car...um 20kw stronger than before.....suck a figure out of your ass and ad 20 to it!

Take the engine out and measure it on the fly wheel.....here 20 there 40...

Aint life f*cken great!

widowmaker · Post by **widowmaker** » Fri Mar 16, 2007 9:43 am

thats why the guys that give you the 200KW printouts make the most money

but still, even if they charge you R200 extra it is the cheapest mod you can make!

Draco · Post by **Draco** » Fri Mar 16, 2007 10:26 am

A question Duane, Hennie and whoever can answer it, seeing as a dyno is basically useless exept showing gains, can a car with a unichip be set while driving on the road?

I am thinking.....if the car can be mapped properly on the road with real driving coditions...who cares about the figures of a dyno, you know your car is tuned optimumly for road use and it is as strong as it can be with your current mods.

On a dyno normally you can not set accurate boost as far as I understand because you are not using optimum wind/atmosphere....conditions as on the road, so if I can get lets say only 0.8 boost on the dyno maybe you can boost 1bar on the road....hence hopefully optimum use/settings.

I would then rather take to the road and get optimum mapping on the road than on a dyno.

Vlade · Post by **Vlade** » Fri Mar 16, 2007 1:52 pm

Draco wrote:I am thinking.....if the car can be mapped properly on the road with real driving coditions...who cares about the figures of a dyno, you know your car is tuned optimumly for road use and it is as strong as it can be with your current mods.

Look tuning it only on a dyno isn't a good idea - and vice versa. My opinion it should be a combination of the both, I think a dyno should only be used as an aid.

My buddy Slade (Martin) tuned his golf running a Dictator on the road only, it ran very very good, when it eventually got to a dyno they (Rightway Developments) could only smooth the map other than that they couldn't improve. But that is was with a Dictator and it ran TPS only, and given it took months, every day represented different conditions and instances he fine tuned and improved.