Team-BHP (https://www.team-bhp.com/forum/)

-   Modifications & Accessories (https://www.team-bhp.com/forum/modifications-accessories/)

-   -   All about Dynamometers + DYNO visit with GTO's Vtec! (https://www.team-bhp.com/forum/modifications-accessories/91746-all-about-dynamometers-dyno-visit-gtos-vtec-6.html)

Hi,
Sorry man!

Don't spend/ waste too much time on figures. I'd rather go by commonsense, gutfeel, and basic engineering learned over the years. (and I know this statement can/ will lead to sniggers, derisive and condescending remarks etc :D)

Regards
Sutripta

Would this apply for these not-high-performance vehicles which are typically driven well below their max power? ie will there be absolutely no slip even when its churning out max power?

I guess one way to check clutch slippage would be with a hub dyno -- but i couldn't seem to find any real info on this.

Would be interested to hear more from your p.o.v on whether or not this could be part of the power loss.

As mentioned earlier, KS said the dyno's reading of the RPM was calibrated by taking the car up to 3,000rpm (on the tacho) and then pressing a button to calibrate it with the dyno. Sure, there could be a bit of error there between the tacho and the manual button-pressing as well.

True - but on an inertia dyno that "added weight" ends up showing as lost / lack of power - right?

cya
R

I was under the impression that BMW supplied a motor that was lighter and had a higher power output than was requested by mclaren and they were happy with that.
Though i have a feeling i heard this on Top Gear, which is probably not the best source of solid information.

Go ahead and post them here!

Not only will they be paying for the purchase, running and space for the equipment -- but the other alternative (the road) is free!
Hence, not something you'd see at a service center.

Great info.
It can be seen as a list of ways to manipulate a dyno OR as a list of variables influencing the amount of power that will get to the road.

Can you tell us more about this run-down, how it is done correctly and what can be pieced together from the results.


Very interesting... and surprising.

How exactly did you get these figures? Was the same engine tested on an engine dyno first?

When you say 12% loss @ 5000rpm, do you mean there is a 12% difference between the engine and chassis dyno @ 5000rpm? Or are these %ages calculated some other way?

Lastly, why are these figures so much higher than the "typical" 15% (at max hp) -- especially since this is also a more efficient FWD.

Could you tell us what the major differences would be between a single roller dyno and a dual?

Thanks,
R

i think this applies to racing engines only..
F1 engineers use to complain about it quite a bit
they dont have a fan to cool the engine like our cars do

Not at all. Its basic physics/chemistry that applies to all engines.

Its just that it probably has a more noticeable effect on race tuned engines which are always pushing the envelope.

This is also the reason why forced induction engines have a distinct advantage over N/A engines at higher altitudes -- ie they keep the intake pressure relatively higher.

cya
R

PS - Some more discussion on the "losses" topic - Heres an interesting thread on "The absurdity of fixed percentage drivetrain loss"

On inertia dyno's you can typically see the results of a slipping clutch in the dyno graph(data). On the Dynojet I used to own it was fairly clear when a clutch slipped during a run. I believe the dyno used in this thread was/is an inertia type dyno?

I'm not sure if things show up the same on a load dyno like a DD but I'll ask the next time I'm on that dyno.

That was just my opinion guys, i don't think getting that much power can be so simple with the mods done on the car. I know its a dyno figure but comparing it with a stock car will give more clearer picture, maybe as you said changing this engine to stock form and then comparing would be even better but again it depends on the owner and i don't think he will do that to clear our doubts :uncontrol

I know the car is serviced at regular interval, but isn't most of the cars, at least on team-bhp :thumbs up.
Even i have serviced my car every 5k kms and changed the engine oil to synthetic, it will improve the engine life and reliability of the vehicle but i don't think synthetic oil and regular servicing can do anything on performance front. I am a noob when comes to performance modding, so i maybe wrong on some points but honestly i find it hard to digest this dyno figures for car which has done ~75k kms.

Power loss in this case has nothing to do with cooling of the engine but because of less air at higher altitudes, so engine has tough time breathing.

See thats the thing. Bhp claimed by the manufacturer is just a reference point. The power of the engine never remains contant, any change in operating conditions will alter the power output of an engine.

A stock vtec in Bbay has a compression pressure of 200psi, this drops to 185psi in Blore and this process continues as you go higher. So who is to say whats the actual power of an engine?

This vtec did 106whp@sealevel under those conditions on that particular day. If another vtec does 106bhp on the same dyno today, we still can't say that both engines are equally powerful coz conditions keep varying all the time.

A back to back test is the closest you can get to finding out the actual diff between 2 engines in the real world unless you have access to a chamber which can maintain the exact same testing conditions at all times.

Shan2nu

I totally missed your last line.

It doesn't have much at all to do with cooling - it has to do with the density of air. The higher you go, the less dense it gets. The less dense it gets, the less fuel can be mixed with it in the correct ratio, resulting in less power per cycle.

Hi HPP,

Yep - inertia dyno (dynomite afaik).

What we are talking about here is not a majorly old, worn out, slipping clutch, that might be clearly visible on a graph -- but rather, the chances that the stock clutch is slipping even a small %age. Views?

Exactly. And we can't at the moment - so lets not go down this road of comparing this readout with what we have heard a stock car makes. It will be a never-ending and pointless debate. Lets save it for when a car does the before/after dyno runs.

Friction!
Some figures i've seen say 3-10% of power is lost due to friction within the engine block itself (ie pistons on sleeves etc)
If you've ever oiled a tight hinge or old bicycle and seen the difference it makes, why couldn't the same apply inside an engine? The quality and viscosity of oil amongst other things will definitely play a part in the performance.

cya
R

Sorry I missed this post yesterday.
IMO, clutch should not slip at all except when it is being operated, or the engine has been tuned for a whopping increase in torque, and the clutch has not been uprated.
The tyre on the roller, on the other hand, can slip. Also if the the roller and the tyre are at an angle to each other, for whatever reason, it will show up as slip.
Slip will result in a depressed power reading.

The added inertia is supposed to be calculated from the coast down, and added back.
It is this add back figure which is not given due importance, difficult to get right, and easiest to fudge.

As an aside, I would take absolute HP figures from a RR with large doses of salt. Would not like to get into a controversy over it. Just my opinion.

A long time back, for CAFE purposes, a manufacturer had used special oils in the cars given for testing. Was caught out, led to a scandal etc, but the end result was that it made less than a 0.5% difference IIRC.

Regards
Sutripta

But wouldn't that be dependant on the type of oil used by the manufacturer? For an engine to lose 10%, it must have been running on some really horrible oil. 2-3% is prob a more realistic figure, which you might see between mineral and synth on a car like the OHC.

Shan2nu

If we're going to talk about friction within the engine, we might as well talk about the energy wasted in turning the valvetrain itself. And knowing you and your physics, we would soon be talking about an imaginary engine called 'i' with frictionless piston movement and behavior of engine in vacuum and at 0 gravity lol:

Oh God!!! No more frictionless, vacuum, anti gravity stuff. Im sticking to the real world from now on. Hahaha......

Shan2nu

Hi All

We have been hearing about dynos and dyno tuning.

I thought I would give a multi part series of posts about dynos and how they can be used for tuning.

Dynamometers, or dynos for short, are like treadmills for a vehicle/engine. They measure the ability of a vehicle or engine to do work.

Dynos are invaluable tools in assessing the performance of a vehicle or engine, because they allow us to study the impact of any modifications we have done. BY comparing the dyno results before and after the modification, we will be able to accurately assess the effectiveness of the mods and make changes if needed.

Dynos can be segregated into types based on their application as
a) Chassis dynos
b) Engine dynos

They can also be classified based on their principle of operation as
a) Inertial dynos
b) Loading (or braking) dynos

In this post I will describe the Chassis dyno

The chassis dyno enables a vehicle to be placed or connected to the dyno without removing the engine and is therefore extremely useful in tuning applications.

The most common type of chassis dyno is what is commonly called the rolling road dyno. This consists of a single roller or 2 rollers on which the car (or motorcycle's) driving wheels are placed. There will also be a powerful fan to cool the car when running. The load on the car, especially on a loading type dyno, is very high and proper cooling is essential. Shown below is a loading type dyno installation at Spitfire Performance, Coimbatore.



In the case of 4 wheel dynos, there will be 2 sets of rollers



The vehicle is properly chocked and tethered by means of suitable straps/cables. This is to prevent the vehicle to prevent it from sliding to the right or left and also from jumping off the dyno.



The roller(s) are connected by various sensors to some computing electronics which measure the speed of the rollers continuously inthe case of inertial dynos. In the case of loading dynos, some additional devices are present (which I shall describe later) and their parameters are also monitored continuously.

There is a variation of the chassis dyno called the hub dyno. This dyno does not have the rollers as mentioned above. They have one unit for each wheel which is directly bolted on to the hub of the car after removing the wheels. This is to avoid the slip that is typically present when the tyres are driving the rollers in a rolling road. Most hub dynos are of the loading type.



There are advantages and disadvantages between the rolling road and the hub dyno.

The vehicle is then run through various speeds depending on the type of dyno (inertial or loading).

The method of the run depends on the type of the dyno (loading or inertial)

to be continued......

Nice dyno you guys have there :)

Are you friends with RD Chinoy by any chance? I'd got word one of the dynos in CBE through him, not sure if it was yours.

Nonetheless, can you give details about the pricing scheme by PM? Very interested in tuning on a load-type dyno