2 Rolling Roads 2 very different results?

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DavidAshton

Member +
Some people may remeber my earlier thread from last year.....if not its below, 204.4 bhp from a OEM ct9.

http://www.toyotagtturbo.com/forums/showthread.php?t=57686

Was very unsure on he result but with the racing line's reputation and experience i tend not to doubt it. So the UKSC rolling road day came round, i ran the same setup exactly, maybe a touch less boost.

Very different results?

So im basically after some clarification from the rolling road experts what seem to be more realistic.....

Here are the graphs

bhp/torque

DSC00249.jpg


DSC00463.jpg


Boost

DSC00251.jpg


DSC00461.jpg


AFR

DSC00251.jpg


DSC00462.jpg


So questions are,

Racing line was run in 4th gear MM in 3rd, any difference?

Any ideas why all the torque has gone?

Boost initially peaks then drastically drops off on second boost graph, this never happens on the road?

Full Boost comes in nearly 1000rpm later the second boost graph, on the road its not this late, its the same as the first graph?

My afr's are in a totally different range, although the look similar, why?

Any ideas guys? :confused:
 
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DavidAshton

Member +
Lol of course I get the scales are different, if I plotted them to the same scale they would look differet though. Plus my other questions still stand.
 
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steveatyork

Member +
i would personally take rr power figures with a pinch of salt,here is an artyicle i pinched of the rtoc(and this guy knows what hes talking about)

Ever wondered if those big BHP claims that tuners and the like make are true ? When it comes to tuners very few claims are accurate,
it doesn't pay to be modest ;-)

So how do you know how much power a car really has ?


A rolling road ? - not really, too many fudge factors here. They're a good laugh and a handy tool but don't take their results as gospel.
Sometimes they're no where near the right figure at all, readings can be low and others inordinately high. I've had rolling
road printouts for over 400hp, the operator assured me it was right, I actually had about 250hp - I knew this before I went.
Every rolling road I went to before and after that event gave me a different reading again. Rolling roads are especially
no good if your car is light and has a big steep torque curve that's likely to get the wheels spinning, rarther like a big-boosted R5GTT!
In order for a rolling road to be accurate you have to;

a) prevent wheelspin completley - wheelspin happens often, sometimes when you can't see it, there can be a degree of slip.

b) measure wheel power instead of flywheel power - at best flywheel figures are a guess by the computer, supposidly calculated from drag.

c) know that the dyno itself is calibrated.

Generally they are better suited to (often lower powered) n/a cars with smooth torque curves. This isn't to say that good, well engineered
rolling roads don't exist.


A Hub dyno ? - getting closer - they have a distinct advantage over rolling roads because wheel spin can no longer be an error
factor in our readings. Clutch slip might be though. Its on the operator to keep track of the recorded RPM and the actual engine
RPM - if the 2 spread apart then something's slipping. The only hub dyno I've sampled for myself was Thor's, very nice I thought,
and more importantly they insisted on providing only wheel HP figures so removing the need for the computer to guess the transmission
loss.

So, short of removing the engine and placing it on a 100 grand bench dyno how can we really know how much power a car has ?


The only system you can't easilly fool - the drag strip.

A drag strip has nearly no erroneous features, its just a track with timing gear, not much to fool.

The rule is that a car's wheel power is almost perfectly related to 2 things; its weight and its trap speed.

Ok, you can argue that areodynamics, gear ratios and such like play a part, because they do, but its a small enough percentage not to worry about.

A drag strip 1/4 mile records 2 main details - ET (elapsed time, the actual 1/4m time) and trap speed, sometimes called terminal speed.
Trap speed is the speed at which the car goes through the final pair of beams at the end of the run. It is easy to see that the more power
you have the greater the trap speed will be. You also need to know that the quality of launch (good or bad) has next to no
bearing on the trap speed, so you can dismiss those claims of "ahh mate, I had no grip in 1st gear, innit, the track was slippery..".

There's some pretty good java calculators on the web that let you input weight and speed to give you a fairly accurate wheel HP figure. I use a drag simulator that takes into account a full torque curve, basic aerodynamics,
gear ratios, shift RPM's, tyre height, etc but essentially it does the same thing only with a little more accuracy.


Here is a list I compiled that relates trap speed to approximate flywheel BHP (assuming a roughly standard weight R5GTT):

(Treat it as a guide, but I assure you the real figure will not be far from the following ;-) )

120hp - 86mph
130hp - 90mph
140hp - 92mph
150hp - 94mph
160hp - 96mph
170hp - 98mph
180hp - 101mph
190hp - 103mph
200hp - 105mph
210hp - 107mph
220hp - 108mph
230hp - 110mph - this is a common one because after this point it gets increasingly difficult to make more power with the c1j.
240hp - 112mph
250hp - 113mph
260hp - 115mph
270hp - 116mph
280hp - 118mph
290hp - 119mph
300hp - 120mph
310hp - 122mph
320hp - 123mph



If you fancy a quick play with a reputable calculator try the one on Ray Hall's website:
 
R

Rev

Member +
David,
I notice standard ct9 most powerful dynos I have seen are the coolest intake temp. For example your first dyno is 13 degrees the second I think says 22 degrees . They are not comparable at different temperatures as the spool strength and time is earlier with the cooler temp. and the start point of the curve will be different.

IMO blurred dynos or dynos without full mods listed on the forum especially with sellers can be misleading but properly listed are an awesome resource for us all. Thanks for following up your dyno.
 
HYBRID

HYBRID

Super Moderator <a href="http://www.toyotagtturbo.
if u look at the af chart on the 2nd printout its very easy to see that ur af (top end) is dropping into the 10s.. that is causing u to loose alot of power, ideally, for safe, yet good results in the uk (since u like ur cars nice n safe) go for a target af of 11.6AF .. here we tune for low 12s af wise.. up till 20psi.. over that we like to drop them into the 11s .. but keep them agressive anyways as timing is advanced to make sure she wont get stuck throughout the rev range.

kon
 
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steveatyork

Member +
its in lbs,it would be good to see what people are getting on this and what they are getting on the dyno pressumeing they know the weight of there gt/glanza.
 
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