[Rehaan]

How many horsepower?

Thats a question thats asked way too often and never seems to get an answer that can be trusted!

However, that changed quite radically when KS Motorsports in Mumbai got their own dyno installed and offered it as a service to anyone who wished to use it. A great move on his part.


What is a dyno?

In short - a chassis dyno like this one is a machine onto which you strap your car down with the drive wheels over a large metal roller, and then accelerate till redline.
The machine then gives you an accurate graph of the horsepower and torque being put down at the wheels.

Finally, a way to get a trustable answer to the "how many hp?" question!


Here's what the setup looks like



When GTO had his Vtec, he had kitted it out with an air-filter, headers and exhaust system - but never got the chance to take it to the dyno. Recently he sold the car to Avinash_m, but he was still keen to see the real world results of those mods made years back. Better late than never i guess!
Dippy and Avinash were to make the trip to the dyno and I was more than happy to tag along for the run.


The car is driven into the dyno space


The drive wheels (front in this case) are positioned perfectly on top of the "roller".


The rear wheels are chocked up as a preliminary measure


And then the heavy duty strap-down is done at the rear. Without these straps the car could move around on the dyno or even lift off / drive off - which would be a catastrophe


The front is strapped down as well. The "X" crossing layout of the straps not only ensure that the car doesn't move forward or back, but even side to side on the roller - which would be dangerous and also affect readings


Mods: Synthetic Mobil 1 engine oil, K&N Extreme, 4-2-1 Greddy headers and an Automech exhaust.
(I guess the battery could be relocated to help the K&N breathe better).
Everything else is stock! (Read more about the modifications)


The interface for the controllers laptop


Notice the fan up ahead, which does its small part in trying to keep the air flowing over the radiator. Probably helps a bit when a car is doing multiple consecutive runs.
The red tube going into the ground is a feed of compressed air used to slow down or emergency-stop the dyno roller.


Here's the heavy machinery of the dyno. A 30" dia. metal roller that weighs a LOT. The car needs to accelerate the rotation of this drum as quickly as possible to get the best results. Hence the term inertia dyno. More on this later.


205/45 Yokohamas on 16" wheels.


The grooved metal surface of the roller to provide good grip.


Got BHP? We're about to find out!


A few basic parameters about the car and weather conditions were entered into the dyno software.
(Karan said that he has played around with different ambient temperature and humidity too see how they affect the final readout - and its not more than a 2-3hp.)

Some dynos connect to the spark plug wires in the engine-bay in order to measure RPM, but in this case, the car is taken to 3,000rpm in the chosen gear and a button is hit to co-relate the engine RPM to the roller RPM.

After a few "warm up" runs (where the laptop battery ran out), the actual run was started - in 3rd gear


Watch the video! >

http://www.youtube.com/watch?v=HdsCul-rtmE

The results then show up on the laptop screen in graph format as well as a tabular breakup



THE RESULT?
106 bhp!! Definitely an impressive figure for the relatively minor mods that were carried out. To be honest, i was pleasantly suprised!

Look at the linear climb of horsepower, and the relatively FLAT torque curve all the way up to 6,700rpm, with a peak of 91 lb-ft @ 5,400rpm.
Karan mentioned that a FPR would put up the power by another 2-3bhp and also increase throttle response.



If you notice, the graph isn't drawn past 6.7k even though the engine revs till 7.1k! I checked with KS and he said this was due to tyre slippage (and clutch slippage too). Remember that the "RPM" reading is coming from the rollers and not the engine - so even though the engine might have been at 7.1k, due to the slippage the rollers think it is at 6.7k.
Keeping the above in mind, its best to use RPM as a relative reference between many runs on the same car. For eg, to see how your powerband shifts up or down the RPM range after certain mods.


But wait. 106bhp ?!?! Isn't that what a bone stock OHC Vtec is supposed to put out?

Well yes, but the difference here is that this HP is being measured at the wheels instead of at the engine's crankshaft (which is the standard procedure for all manufacturer horsepower claims).

Whats the difference? Well, horsepower at the wheels is always less, due to frictional losses in the drivetrain, inertia of drivetrain parts and a dose of clutch slippage. Typically an average guesstimate of around 15% is added to wheel horsepower (whp) to get a decent guess of the hp at the crank.

So, even if we take a reasonable window for drivetrain losses, (say 10% to 20%), this Vtec would be putting out 116 - 127 bhp!

As i said earlier, I'm pleasantly surprised!!

[Rehaan]

THE RIGHT WAY!
First things first, we have to realize that even though a dyno like this might be more accurate than any other power measurement method we have access to - it still works best as a comparative tool.

Simply put, you're better off dynoing your car once before and once after a specific modification and then comparing the two for the truest results.

Right now we can only guess how many hp the modifications added to this Vtec, but if we had got the chance to do a stock run a few days before the modifications, that would have clearly shown the difference in the most accurate way. Unfortunately, in the case of this vtec the modifications were made way before this dyno existed!



TYPES OF DYNOS
We can break this up into two basic types :

1) Chassis Dynos : Like the one shown above, these are basically "rolling roads". They are easy and convenient to use and also give a more "real world" result, because what you make at the wheels is what makes your car go fast at the end of the day. There are also some chassis dynos that mount on to the car's hubs so as to eliminate tyre slippage etc from the final result.
2) Engine Dynos : This type of dyno links up directly to the engine, hence giving a readout of what the engine is capable of. Obviously, to test your engine on this type of dyno it would have to be removed from your car, and hence makes little sense for us. However, manufacturers use this type of dyno for engine development and testing.

The major differentiator in the results is that the chassis dyno will produce a lower number due to drivetrain losses.

Related link : Types of Dynos / How do manufacturers calculate HP?



TRANSMISSION LOSSES? 15%? REALLY?
Its hard to believe that you're losing somewhere between 10-25% of your power between the time its made at the crankshaft to the time it reaches the road isn't it? But as you begin to add the pieces together it starts to sound more believable. Heres the list :

- Gearbox (the friction caused as the gears mesh together)
- Each gear has a different amount of friction, with a 1:1 drive ratio usually being the least (However the gear for the run is eventually chosen based on the dyno's capabilities and car's power output)
- Quality of oil in the gearbox makes a difference too!
- Auto transmissions apparently lose even more than MT gearboxes
- Clutch slippage (a stock clutch will slip more than a performance clutch which has the ability to handle more power)
- Differential (many gears meshing together causing friction once again)
- Part inertia (just the additional power used up in rotating heavy parts in the drivetrain factors in too)
- Tyre flex & Rolling resistance
- Keep in mind that this "percentage loss" will change with rpm, but its safe to assume it will me a maximum loss around max power
- Apparently FWDs are supposed to have more efficient drivetrains, so sometimes people use a 10-12% figure for them
- Bikes have lower losses since their drivetrains are more efficient (chain drive, less part inertia, no differentials, etc)

Related link : Lost power? Inefficiencies of the drivetrain and engine



OTHER FACTORS AFFECTING THE DYNO RESULTS
As mentioned before, these are not absolute measurement tools and there are a lot of variables that can affect the readout :

- Brand of dyno (Some claim that certain brands are more optimistic than others - however we're talking very minor differences here!)
- Weather conditions - humidity & temperature (Karan said he had played around with these, and the max difference it made was about 2%. Not sure if his dyno has a weather station or it is all manual input)
- How the car is strapped down! (If its too loose, it sways side to side on the roller and loses out on power. If its too tight, the tyre sidewalls flex more and require more effort to spin)
- Tyre size
- Airflow (If you're doing 5000rpm in 3rd gear, some smart cars expect a certain volume of airflow, which won't be happening on the dyno - so the ECU changes the fuel supply and other parameters accordingly)
- Engine's operating temperature
- Engine oil (Viscosity, grade and synthetic/mineral all make a difference. It comes down to friction after all)
- Software smoothing (When displaying the results in the graph)

That said, this is an inertia dyno that doesn't require much regular calibration, so repeatability of results should be fairly good. In other words, if youre using the dyno the way it should be used for comparisons, the above points shouldn't matter much to you too much.



WHAT NEXT?
Hopefully we'll get a chance to use the dyno to do some comparative runs in the near future! Wait and watch....



RELATED LINKS

Avinash_m's vtec ownership thread + his report on the dyno run:
Realization of a dream-A dream of owning an OHC VTEC!!

KS Motorsport Website:
KS Motorsport

TBHP Discussion when the dyno first opened up :
Dyno facility in Mumbai...finally!!

A super article and interesting thread dating back to 2004 !! I quote myself from that thread:

Originally Posted by Rehaan

he was telling me about how he was part of a S2000 forum (s2ki.com) and they were planning a meet to go and dyno their cars together at a nearby shop!!
Someday we at team-bhp will be in the same situation......

Great article on measuring Horsepower



And here's a mean looking lancer conversion parked outside the KS garage!

[GTO]

That engine revvs like that of a motorcycle! It just climbs on and on the RPM meter, smooth to the limiter (can clearly hear the revvs bumping off in the video). As I posted in Avinash's ownership thread, this is a testament to the way that Honda builds their petrol engines. Heck, the number is 106 BHP @ the wheels @ 75,000 kms!! On the stock factory-fitted clutch! Even after 7 years of hard-revving, it's still "crisp" and an absolute delight to high-revv. Show me one engine from the current breed of 10 lakh cars that can match this jewel.

Taking into account an averaged 15% transmission loss, my Vtec is churning out 122 BHP. No wonder its left ANHCs & stock Civics for dead in acceleration runs. I'd give substantial credit to perfectly timed Mobil 1 oil changes for the engines pristine health at such age. Believe me, that Vtec has seen the redline on a daily basis through most of its life. Also to the Greddy headers that I bought from Psycho & Automech's freeflow exhaust kit. I remember the car's throttle feeling sharper right after bolting them on.....we know why now!

The post September 2002 Vtecs came with an upgraded ECM. While they lacked the jerkiness of the earlier Vtecs, Shantanu (after his first drive in my then stock car) immediately said "Your car feels quicker than mine". I wonder if this upgraded ECM also led to a bump in power, as my Vtec didn't have any of the driveability issues faced by other pre-2002 Vtec owners.

Another Video of the same run. Engine sounds better here:

YouTube - My VTEC's Dyno TEST

[s3va]

Thats really a cool way of sharing the test.

I remember the way I used to measure the RPMs out of an electric motor during my engineering days. I used to shove the measuring rotor lead of the RPM meter(dyno) directly into a point designated in the motor that is infact the closest point to measure the engine power. Then the motor is switched on and the meter had to be firmly held so that it is firmly in its place. Now this is the actual power and true test of power. The power at wheels is the trimmed one due to factors as listed above, although it is the feed to our adrenaline highs !

[iceman7]

This is amazing. A sure shot testimony of how strong these Honda engines are. Super!!

@GTO - Don't you wish the City was still with you?

[balenopower]

those are some surprising results. Someone should get a stage 1 baleno and a palio GTX on the roller as well. Should cough up some interesting results.

[Shan2nu]

Awesome writeup Rehaan. 106whp with just filter and exhaust is way too cool!!!

Even if we consider 15% losses, thats a good 125bhp@6600 and 146nm@5400 at the crank.

@GTO - Don't you wish the City was still with you?

He just sold a 125bhp/985kg City to pick up a 132bhp/1210kg Civic. Oouch!!!

Shan2nu

[NOS Power]

That read out is actually mind blowing considering only the filter, headers and exhaust have been replaced with performance ones.

What i want to know is that how is the torque curve of a stock VTEC. Is is also flat, cause if it isnt then the conculsion would be that the Greddy headers have done an awesome job.

This the best form of linear power delivery one can think of. Especially since the Greddy headers take care of the bottom and mid range and the VTEC takes care of the top end (GTO & Avinash correct me if i'm wrong).

GTO, hats off for refurbishing the car in that shape till u sold it and Avinash, you have a stonker in your hands (not that i need to remind you of that).

[mnhegde]

Thanks Rehaan for the nice and detailed Dyno report and Videos. Honda engines are simply .

GTO : Missing the sweet V-Tec ? That car is a sure head turner.

[Shan2nu]

Taking into account an averaged 15% transmission loss, my Vtec is churning out 122 BHP

Its 125bhp@15% losses.

The post September 2002 Vtecs came with an upgraded ECM. While they lacked the jerkiness of the earlier Vtecs, Shantanu (after his first drive in my then stock car) immediately said "Your car feels quicker than mine". I wonder if this upgraded ECM also led to a bump in power, as my Vtec didn't have any of the driveability issues faced by other pre-2002 Vtec owners.

Yes, your car did feel quicker than mine bcoz it was more powerful than mine.

What we forgot to consider that day was the altitude diff. An engine loses upto 3% of its power for every 1000ft evelation above sea level. So even if our cars were tuned for the same power output your car in Bbay would still be producing around 6.6% more power than my car.

I realised this when i took my car to Mlore. It felt pretty quick compared to how it perfomed in Hubli

Shan2nu

[lancer_rit]

Man, that's one impressive result for mods done.

@GTO, I once suggested (on your VTEC thread) to do a dyno run, but you felt it will be a few bhp, and no use going for it ...
Looks like you were off mark for once :-)
Besides, I can't think of a better candidate for a dyno result for a modded VTEC of our tbhp co-founder !

[alpha1]

Will the torque / rpm characteristic of an engine change with the load encountered?

[safari_lover]

Awesome write up Rehaan. Thanks for sharing this.
Also the engine sound in the second video is very addictive.

[abhi1309]

Rehaan, I love your car, this is probably the best made City in the country and I am sure how many of us would like a car that is exactly this. Perfect equipment, perfect car, perfect mods. Just awesome. This is a great thread.

[Shan2nu]

If you notice, the graph isn't drawn past 6.7k even though the engine revs till 7.1k! I checked with KS and he said this was due to tyre slippage (and clutch slippage too). Remember that the "RPM" reading is coming from the rollers and not the engine - so even though the engine might have been at 7.1k, due to the slippage the rollers think it is at 6.7k.

So whatever is causing this slippage is creating a difference of 5.6% between engine and wheel rpm.

So does this indicate that another 5.6% in addition to the 15% is being lost in the process, due to slipage?

Coz be it wheel spin or clutch slip, the power being transfered from the engine to the ground is being affected.

Rehaan, I love your car, this is probably the best made City in the country and I am sure how many of us would like a car that is exactly this. Perfect equipment, perfect car, perfect mods. Just awesome. This is a great thread.

Poor Avinash, he's having to split the ownership with GTO and Rehaan. LOL

Shan2nu