Thanks abhijeet,kaynmantis,boon for your support and understanding

No, i asked him if he has removed or added any metal from the chamber, and he said he didn't. But he removed some metal from the piston, to make it a dish-top(something similar to stock piston), which creates an additional volume of 2.464cc, if the cavity carved is of 1mm depth and 56mm in diameter.

Hence, I mentioned this in the same post:
Since the volume created due to additional dish-top would be 2.464cc(as per above assumptions only), the cyl volume would effectively be 171.54800 + 2.46400 = 174.012cc, and that's what I used for above calculation. Also note I mentioned the corrected chamber volume in the above calculation.
Now, if we instead assume the cavity to be of only 0.5mm in depth, I mentioned this as well in the same post:

That's just one of the reasons, the other reason is the increased compression . Also, note that lightening the con-rod while making the piston heavier and increasing the force generated in power-stroke COULD be risky, especially if the alloy used is same. ofcourse, it'd be different if the metal used for the lighter con-rod is different though.

There're many reasons why Harish's setup could be smoother, due to lesser compression, the oxidized coating of cylinder, bearing coating, etc. The piston, being located farther from the crankshaft's center, compared to the con-rod, plays more critical role in weight balancing.

I'm sure you tried your best to explain us the mods that you did Shah, and I appreciate this fact . Thanks for all the information provided, and please keep us informed about anything that you can share. I agree laws can be bent slightly, but it's only "slightly", they can never be broken for sure, right? This's what I was trying to explain everyone over here. All I was trying to tell is that both kits have their own characteristics and traits...

Great thoughts man and your Questions are very deep into the setup..

Off course all the measurements were based on practical experience and not theoretical. So if you want me to answer in calculation then I have to strip the engine again the take the measurements for you.

And correct me if am wrong,

The stock compression ratio is not only depending on the Cylinder, piston and head (valve openings), the exhaust bend pipe, muffler has a crucial role to play in providing enough back pressure to the engine. Mostly OEMs decide the compression ratio in a balance with the Exhaust, so it not only ends after the Exhaust charge at the head.

You also know that any bike over 150CC (mostly OHC) needs more back pressure than a 100CC to effectively complete Scavenging and that is the main reason for uplifting the Exhaust (Angle Bend pipes) while the 100CCs remain flat.

As shahdupeshkhan mentioned, he has corrected everything till the exhaust and exhaust was still tuned for the stock compression and made the setup a bit uneasy. Also I did not go for Joel's FFE, as I wanted the setup to be silent (No offense, offcourse FFE will be loud worldwide)

Like I have said, I removed the Catalytic Converter from the exhaust for better exhale (Approximately) and did not do any Exhaust porting to the Muffler unit, coz I never wanted any change in Exhaust note. Also I did this in approximation and it did work and don't have the ratio in which the exhale differs between stock and after removing cat-con.

I would say a 10-15% approx, coz the engine seems to be torquey than before over 9000RPM in 6th gear. But I tried till 141 causally and a lot left in there, so I am sure it will break pass the redline in 6th gear when tested purposefully.

Also to be accurate, the combustion chamber remains stock and bike uses stock spark plug.

Having all this said, I not sure, how exactly we can derive at the accurate compression ratio in my setup to answer you.

I did try a casual Dyno test (Just like weighing yourself suddenly when you see a weigh machine ) , see if that helps you, with the current Bore, Stroke and exhaust setup it has about 16.12 hp at the rear wheel and the bike performs silky smooth than stock. (Power may be lesser than urs , But my setup lacks FFE, HL CAM and I did restrict shahdupeshkhan on performance, rather focus on reliability and smoothness ). Not sure it must be about 19-20 Hp at the crank(But not sure)

Today I stepped in the service center for a different bike and I did inquire about the Dyno to see if I can get detailed numbers as quoted by the Manufacturer and they said they cannot even check the Power at Crank and that particular Dyno is usually used for testing Yamaha SBK's performance alone and not an advanced one. If you have any idea or place to check it directly, I can do it and update this post.

Thanks.

Thanks!

Don't worry, even my calculations were based on a few assumptions Guess it's better you don't disturb your setup much, it's just now that you started enjoying the ride after all!

Yes, and this is what is called Dynamic Compression Ratio. I did mention that D-CR depends on inhale and exhale abilities as well, which includes the port, air intake tract, exhaust path, etc.

I'd differ on the exhaust thing you said there. Scavenging is achieved through resonance. Everytime the exhaust valve opens, it generates a sound wave, and a tuned-exhaust is designed to utilize the energy of this sound wave, on the principle of resonance, and pull out the exhaust gases better. So, Scavenging and Backpressure are two seperate parameters. Backpressure is the restriction you put on flow rate of exhaust, and scavenging is the process of pulling out the exhaust from the cylinder. Ofcourse, an exhaust is designed keeping both of these in mind

I dont ask you to measure the CR, but if you want to do it for your own knowledge, I can tell you how it is done. SVCs which service SBKs usually have a device to measure the CR in a fully built engine, you could try it if you're interested.(noo for me )

My bike also doesn't have a HL cam or FFE as of now. Doesn't even have the aftermarket ECU. I'm just using the reworked head, big-bore, Simota air filter as of now. FFE will be added soon And yes, the regular dynos cant check power at crank, few provide estimations though. I believe crank measures can be done only if the engine is removed from the bike, not sure though.

@digislayer - I had considered another possibility to change the combustion chamber volume - what if the new piston sits a bit lower compared to stock, that is the piston pin sits a bit deeper and closer to the piston top? That's possible right?

Hi

The thread is going more in to the intricacies of Engine and it's functioning...Here is a link on CR and DCR ...helpful for noobs like me...
Kennedys DynoTune- Dynamic Compression Ratio Explained

Finding the thread more intresting :-)

@ digislayer

Bingo!!!

Just now I remember the TVS Tech head talking about the Apache 150 some 5 yrs ago when I got the bike.

Since I did not look deep into R15 Muffler, I am not sure if it has separate resonators in the Exhaust, for Intake and Exhaust as Like the TVS Apache (Not sure about RTRs)

Coming to the point,

Do correct me if am Wrong

Scavenging and Backpressure are two separate parameters. True!

But I have two questions to you...

1) Scavenging depends on the Exhaust design's back pressure capability for Scavenging efficiency isn't it?

2) Is Scavenging completely achieved through resonance only? or just a part of it to increase Scavenging efficiency?

Like say, during the actual Scavenging cycle

I suppose the 1st part of Scavenging cycle is purely Exhaust Dependent

1st the large pressure difference between the exhaust gas in the combustion chamber and the atmospheric pressure outside gets EQUALIZED only with the help of exhaust system, so only if the Exhaust is designed accurately (I mean bent in accurate angle it can serve the purpose) the entire process will be executed normally in the right interval, with FFEs the process is rushed.

FFE will always be grounded lower without much appropriation and Lower the duration in which the pressure reaches the Head and hence lower the exhaust gas pressure in the combustion chamber rapidly which increases the exhaust gas exit velocity, but inturn affects the entire exhaust stroke by making it a tad shorter (Tad is in milli secs ). So any day FFE will perform better than stock.(There are other aspects too, I am speaking in terms of Scavenging alone)

For this, you can easily compare Daytona FFE with Joel's FFE. The postion and angling with Daytona's FFE will be much acute.(No offense, just comparing) But end of the day, FFE itself isn't good for an everyday engine.

2nd part is purely not depended on Exhaust.

2ndly, as the exhaust gases equalize between the combustion chamber and the atmosphere, the difference in pressure decreases and the exhaust velocity decreases.This relatively low pressure helps to extract all the combustion products from the cylinder and induct the intake charge during the valve overlap period when both intake and exhaust valves are partially open.

Coming to the resonance part,

Again correct me if am wrong,

Resonance tuning is just to utilize the low-pressure reflected wave pulse which can help scavenging the combustion chamber during valve overlap much efficiently. This pulse is created in all exhaust systems each time a change in density occurs, such as when exhaust merges into the collector. So this pulse is re-induced by the resonator in the muffler (In Indian budget bikes, I am not sure they differentiate resonators in muffler and utilize this procedure)

But well I know, Apache 150CC was the 1st Indian designed bike to have separate resonators in the Exhaust, for Intake and Exhaust, to re-induce this effect in a faster pace and likely to have both the scavenged gas and overall resonation in balance.

So I end my post by telling,

Resonance helps the Scavenging to happen better and efficient, but not entirely dependent on it.

Also Exhaust back pressure plays an important role in Scavenging by equalizing the pressure between Combustion chamber gases with the Atmospheric pressure in the right interval. (Coz even FFE does the job, but incorrectly)

I personally thank you for being so informative and straight to your point man .

@HarishK:
First of all, thanks for all your compliments!
And please correct me if I'm wrong anywhere during this explanation.


I'm sorry, I didn't get your question completely, but this is what I can say:

All exhausts do both scavenging and backpressure parts. But what makes a "tuned" exhaust special is, it uses the tuned characteristic to perform scavenging and apply back pressure at a precise timing.

For the exhaust stroke:
The resonance generated by the exhaust is used to create an area of negative pressure right after the exhaust valve, which sucks the exhaust gases as soon as the valve opens and creates a negative pressure in the cylinder, which in turn helps suck the intake charge as soon as the intake valve opens.

This is with a PROPER cam timing. But when it comes to reality, cams usually maintain an overlap, which means there'll be a particular point of time when both exhaust and intake valves are open simultaneously. This is done to increase the "valve open" interval which is very critical at high RPMs. Now, when this happens, some of the charge can actually come straight out of the exhaust valve as soon as it enters the cylinder, without staying in the cylinder. This results in less charge being filled in the cylinder, power loss, poor FE. To combat this, Tuned Exhausts use another property- backpressure.

The exhaust takes care of producing a resonant pulse that actually creates a positive pressure after the scavenging is done, so that it applies pressure at the exhaust port at the right timing, in order to not allow the intake charge to come out of the exhaust unburnt. Sometimes, both these properties- scavenging and backpressure can be applied in sync to supercharge an engine too.


A tuned exhaust uses atleast two cone frustums to reflect the pulses and create resonance. And the distance between these reflectors is what decides the timing of "negative pressure" and "positive pressure" at the exhaust port.

@ digislayer

I find this part slightly twisted the other way, does resonance used to create an Negative pressure to extract the exhaust gases from cylinder?

(Here negative pressure means lower, I suppose)

Not sure how will resonance lower pressure?( create an area of negative pressure)

or

My perception,

The exhaust gases are extracted from cylinder when the pressure lowers in the combustion chamber due to the Equalization of atmospheric pressure, which happens with the real world contact through the exhaust.

As I have mentioned earlier "Resonance tuning is just to utilize the low-pressure reflected wave pulse which can help scavenging the combustion chamber during valve overlap much efficiently."

Utilizing Resonance is relatively a newer technology which in works in combination to help scavenging.

Pls comment if you disagree with this, else we will drop this conversation as its getting too much OT.
More over I believe, Tuned Exhaust in your terms means exhaust like Two Brothers and not FFEs . Isn't it?

Well if you meant Two Bros, I think the point made by you is very accurate.

Also another crucial thing you missed in my post (I was expecting you to raise a question there) is the comparison of Joel's FFE and Daytona's FFE for the R15, if you get in depth to the Daytona's design you will know the how the design matches and the pipe Angles blend accurately and hence the experience and heritage of Daytona is proudly reflected there.

hey guys i got the big bore installed a day ago, thing is i got the bike serviced 10days ago and replaced the oil. now am using motul 5100t semisynt and its run abt 500kms before the big bore. now after the installation should i change the oil to mineral or can i fin the runin with the same??

^ I did run in with 300V. Replaced with the same after 500km. No issues at all.

I'm getting the FFE+Bore+Filter for the R15 this week.
But, not getting the headwork done, or rather can't get it done.

What exactly does the headwork do?
What are the cons since I'm not getting it done?

I think you should go for the headwork too...It will make your bike a lot smoother...
Why dont you ask JOEL?He will give you a precise explanation.

I'm getting the same kit as you next week, I have sent Joel a mail regarding headwork, to ask if I can send the cylinder head to him and he can return it with the other parts. The purpose is to modify the inlet and exhaust ports to allow more and a different airflow, properly done requires a flow bench, each vehicle is different, the flow bench will guide you to getting your desired results. Just like a free flowing air filter and exhaust, this will allow your engine to breath better, usually a combination of mods yield the best results over individual components. So don't just let any grease monkey do your porting, if done incorrectly will make you lose power.
Sorry my explanation my not be the best, maybe someone else can elaborate further.

awesome , but they say new engine must be run in with mineral only to get best performance at later stages??