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Old 17th July 2007, 08:29   #76
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Originally Posted by mclaren1885 View Post

I have heard that dyno's from different manufacturers with the same numbers set for different parameters put out different figures. Some higher, some lower. This in itself can turn around quite a few tables. Now which one would you believe if you were to know the real BHP of your car?
True. But I would use the dyno more as a tool for comparison rather than as an absolute indicator.

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Originally Posted by mclaren1885 View Post
Also, doesn't one have to feed in the values for barometric readings, total weight, axle weight, vehicle's rotating mass, gear ratios, co-efficient of drag, vehicle frontal area, tire size, dyno roll mass etc? Now what if a common man who has no clue what CD his car has, or what his gear ratios do?
You dont need to do any of these things. Look at Dynojet Research's page to understand what their data acq takes care of:
Automotive Dynamometers - Innovations & Performance Products from Dynojet.com

Although, I've spoken to a couple people who use inertia dynos on a regular basis, and they seem to think the variation comes more from the operator himself. In other words, how and when you roll on the throttle during the run or "pull" as they call it MAY change the reading, but only by a couple of tenths of a HP. You decide if thats significant.

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Also in which gears do you peak out to check the final output? Does it depend on a particular dyno? Or are there any standard rules?
That depends on the rotating mass of the drum. If its a small drum, obviously there wont be enough oomph in it to load up a high-horsepower engine in the lower gears. For example, a 600 hp Nissan Skyline cannot be loaded in the 1st or 2nd gear enough to produce an accurate run. So you do the "pull" in sixth. But for a stock Zen with 50 hp, the run might take forever to do in fifth. So you do it in third or second just to get a quicker reading.

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Also aren't inertia type dyno's less accurate compared to load type dyno's? If so, how will this translate into measuring HP say for a common man like me?
No. Inertia dynos are accurate in practice because you dont have to calibrate them every other run like you need to with some brake dynos (calibration errors). For measuring HP, doing back-to-back runs with even small changes like switching from 20W40 to 0W20 oil CAN be measured.


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Originally Posted by mclaren1885 View Post
Also, cant dyno's be manipulated? Easiest ways are:

1. Entering the wrong set of values for air temperature & density.
2. Depending on which gear you take the run. Is it possible to do a dyno run just in 2nd gear? Suppose we do a run in 3rd gear wont the figures change? Also is there any standard procedure to this?
3. Getting the engines upto optimum temperatures for comparative runs.
And so on. I am sure you will be aware of all this.
1. not if you have a data acq that has sensors for these. See link above.
2. Figures wont change in second or third because you are sensing RPM as well. In other words, drum acceleration is normalized against rpm change per second.
3. Well no one who does a pull on a cold engine should be allowed NEAR a dyno.

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Originally Posted by mclaren1885 View Post
I did infact read that KS had mentioned it to be a Inertia Dyno only after I had posted. Agreed ID doesn't need much of a calibration except for setting of the air gap between the Hall Effect sensor and the trigger wheel.
I wouldnt know why dynojet would want that adjustment from the user end (KS is dynojet right?). Also, I doubt if you can find a chassis dyno that's not an inertia type. The risks in holding a car or motorcycle at high speed for long times are too many.

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Originally Posted by mclaren1885 View Post
But my question is since there are too many IF's & BUT's how does one go about it? Suppose KS' dyno shows my car putting out 130bhp @ crank and tomorrow another tuner gets another dyno that shows 110bhp @ crank whom am I to believe? All parameters being the same.
This is a common problem and the only workaround is go to the tuner you trust the most. And do back-to-back runs with and without the changes you made that mandated the dyno run in the first place. Then the cat will be out of the bag.

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How do I go about if I were to get a definitive indication of my cars HP without having to think twice.
Why would you wanna do that? The dyno is only a tool to understand what changes have affected the engine and by how much. Not to tell you your car has x amount of power and thats it.

Its a step in the right direction if Karan publishes baseline readings for popular stock cars. Then the confusion will clear itself.
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Old 17th July 2007, 16:58   #77
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Thanks for taking the trouble explaining everything in detail.

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Why would you wanna do that? The dyno is only a tool to understand what changes have affected the engine and by how much. Not to tell you your car has x amount of power and thats it.
Thought as much, so any auto manufac's claims are only that?

Also amongst the dyno manufacturers I hear Dynojet shows the highest possible numbers . If nothing else KS' customers will surely be happy seeing the figures.
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Old 17th July 2007, 17:09   #78
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Guys, lets give credit where its due... Hats off to KS for having the nerve to get one down inspite of all the risks involved..

Everyone cribbed about not having a dyno in India..Now that its here, lets not get into opinions on run costs (dont forget its an expensive system), accuracy (its a system with with built in corrections - weather station- used by hundreds world over) , tuner tactics or whatever it is....
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Old 17th July 2007, 19:41   #79
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You're welcome

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Originally Posted by mclaren1885 View Post

Also amongst the dyno manufacturers I hear Dynojet shows the highest possible numbers .
You might have meant this as a joke, but even if it is one, isnt that rather arbitrary? Can you quote a source for this information?
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Old 17th July 2007, 20:40   #80
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i guess its off one of the old magazine articles i read too... as per their testing dynojet would read a a wee little higher than other.. but there was an explanation on the reason as well.. let me see if i can find it..
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Old 17th July 2007, 21:34   #81
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Ananth, it isn't a joke. I had read this on another forum. A long time back. Shall see if I can find that now. AFAIK the other dyno's were Dyno Dynamics, Superflow & another (can't recollect the name but its damn popular).

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Old 17th July 2007, 23:07   #82
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Got it. Here is the LINK
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Old 17th July 2007, 23:40   #83
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Cool

mcl i was going through this sometime back and then just came across this thread so thought i'd put it down here for you guys.

What is stated by car manufacturers is flywheel power using an engine dyno vs what a commercial rolling road dyno mentions is power at the driving wheels.

As we all know there are lots of losses in tires, transmission, etc which means the bhp given by a rolling road dyno is always lesser than the engine bhp given by the automaker using an engine dyno.. To compensate for this some assumptions are made on losses and this number is added to the driving wheel power which a rolling road dyno gives.

Now these assumptions in transmission losses are different for different rolling road dyno makers, which is why dynojet may show higher numbers than others and make you happy

heres the link - a good read
Puma Race Engines Technical Guide - Measuring Engine power - engine dynos and rolling road dynos
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Old 18th July 2007, 01:25   #84
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Originally Posted by mclaren1885 View Post
Got it. Here is the LINK
Not to take anything away from that forum, but the guy works for one of the dyno companies there which apparently shows the lowest numbers (and the hidden meaning in that discussion is lower=more accurate).

This is a good discussion we are having in here, but at the end of the day, you guys dont have a choice but to go to KS (as yet). He's taken a pretty big financial risk and that deserves respect. I'm not soliciting or anything, just pointing out there's only one guy with a publicly accessible dyno in India.

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Old 18th July 2007, 11:34   #85
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Default Not a dyno jet

Hello,
Mines is not a dyno jet.BTW they(dynojet) dont make thier own dynos,then get them made from a dyno manufacturer,including the software.My collage in USA that i went o also had a Dyno jet.Our instructors would always tell use to tune the car according to the dyno and not according to the calculations that were done on paper.

This dyno that i have got in is for myself,which i will allow others to use as well.I know I will never be able to recover the money by just doing dyno runs.This is a tool i will use to perfect my tunning capabilities.I have not got it to challenge any car manufacturer.It will be a tunners pleasure to use.

Enough said on that,other than sepculating over a forum,why dont some of u get the cars that u have made(tunned),and run it and then justify ur claims.

Some of you have have wlecomed this dyno and some are still thinking.."oh may he should have got a dyno pack..or maybe a dyno jet"
All this makes me laugh at the ignorance of the people who first complained about a lack of dyno,and now about its effectiveness.

Looks like some of the people on this fourm are very intimidated by the dyno.We can go on with this thread,but whats the point.

Hope to see some teambhpians at the dyno soon.

Karan
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Old 18th July 2007, 12:02   #86
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Very well said Karan. Expect me at your place for a run by mid next month.
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Old 18th July 2007, 12:03   #87
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yeah.. you should give us "Team-Bhp Discount" we gonna prepare a list of cars from t-bhp who really want to tune/run on dyno. i am sure if the volumes are high you can give us all special pricing.

@ All members on t-Bhp

kindly vote in who are seriously thinking of tuning/run on dyno. or whoever just wants to see what power their cars are putting up.

the list begins with me.

1) Ford Rocam's - OHC Hybrid. (expect to be on roller in a couple of months time)
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Old 18th July 2007, 12:05   #88
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yeah.. you should give us "Team-Bhp Discount"

kindly vote in who are seriously thinking of tuning/run on dyno. or whoever just wants to see what power their cars are putting up.

the list begins with me.

1) Ford Rocam's - OHC Hybrid. (expect to be on roller in a couple of months time)
Hi Jitu,

I 2nd that we should get some Tbhp discount. Expect me there very soon after i finish running in the new engine.

Viper
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Old 18th July 2007, 12:06   #89
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I 2nd that we should get some Tbhp discount.
ahahaha! Maybe Karan should hand out Perk's to the first 50 guys!
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Old 18th July 2007, 12:10   #90
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Karan, as much as we appreciate your hard work and bravery in getting a dyno down I see there is no harm in doing ones research asto how it works or what are the cheats that can be carried on. It will only make us as end customers more knowledgeable. Isnt that what we all want?

No one (atleast wrt to myself) is thinking twice about dynoing my car. Its just that I am trying to set my goals straight on what to expect and what not to. Like busa mentioned coming down there and finding your stock company claimed figures to be higher than your figures after tune would be a let down for those who haven't done a detailed study on the subject. Or factored in the drivetrain losses etc.

Oh and btw dont laugh it off as ignorance. Its just that I like to ask questions and I see nothing wrong in it either. Isn't it the way we all learn?

Also, being a TUNER it would help if you spelled your professional status right .

Jitu, add me to the list. Hopefully will find some time and money to drive down to Bombay soon.

Last edited by mclaren1885 : 18th July 2007 at 12:11.
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