newbie....

yokohama

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As it seems, there has been a need for another technical discussion on tuning theory. I think more and more questions arise why you run 12:1 afr vs. 13:1 or 14:1 or this certain ignition timing. Anyone can just find threads where such and such ran this ignition timing and this AFR. I think very few people know why you would run this certain AFR or Ignition timing.
Until now, i didnt want to get in depth of the reasons why, but to justify the reasons I recommend certain AFR's and Ignition timing, we will discuss it.

In order to really under stand this discussion, you will need to know a lot of mechanics of the engine. IE. the cycles the motor takes. i really dont want to take the time to go into detail for now, maybe later.

The name of the game to making power is making the burn duration when the peak combustion pressure occur around 16 degrees after top dead center. The reason you want this is because it creates the most force on the crankshaft at the optimum angle to produce the most power. Sometimes people refer to this as MBT (maximum brake torque) but i dont really use that term much.

So in order to do that, we need to know a few things. Our boosted application allows the cylinder w/ more dense charges.

Lets talk a bit about AFR's. Many people just see people running XX:1 Air Fuel Ratio, and thats what they go by. You have to look deeper into Heat Transfer theory to really understand what is going on here, and why you would run certain AFR's.

About 25 % of the air/fuel mixture energy is converted to work, and the remaining 75% must be transferred from the engine to the environment. .

Octane Levels

The octane number of a gasoline is NOT a measure of it's hotness or coolness in the burning process, and it is NOT a measure of how 'powerful' it is. The octane number is simply a measure of how good the gasoline resistance of detonation. This is a huge misconception. Higher octane fuels are better at controlling the decomposition into auto-ignition compounds than lower octane fuels. Many people think they can run higher octane fuel at leaner temps. well they are simply wrong.

this is some tip for u guys....
e-mail me if u want [email protected]
RB26 rocks...^^
 
Thanks for the tip but I have to disagree with you

16 deg of igniton? I run that at idle..maybe you are generalizing a bit...there are more to gaining power that just assuming that anything after TDC is the rule. Alot of variables needs to be factored into the equation..type of fuel, tempreture, pressure and compression.

I have to say that you don't need an extensive knowledged of Heat Transfer technology to know at what AFR you should running at..What's the point of us knowing that the upper left hemisphere of a piston crown is experiencing heat spots ? we usually work on parts and components that are available to us and work our way around its limitations.I would suppose the knowledge would be useful if only you design and manufacture components.Knowing what to look for and using the right measuring tools ie, Dyno, Knock Sensor, Lamda,exhaust tempt.. etc are just what you need

What's the point of dumping in high octance fuel if you can't run leaner and more advanced?
Do let me know cause I would gladly switch to 92 octs...i

I'm most probably wrong with all this so do fiil me in :)
 
does this only applies to skyline engines?? or it applies to any petrol internal combustion engine ???

y here in the Skyline Club thread? just curious....:unsure:
 
.S K A G E E. said:
Thanks for the tip but I have to disagree with you

16 deg of igniton? I run that at idle..maybe you are generalizing a bit...there are more to gaining power that just assuming that anything after TDC is the rule. Alot of variables needs to be factored into the equation..type of fuel, tempreture, pressure and compression.

I have to say that you don't need an extensive knowledged of Heat Transfer technology to know at what AFR you should running at..What's the point of us knowing that the upper left hemisphere of a piston crown is experiencing heat spots ? we usually work on parts and components that are available to us and work our way around its limitations.I would suppose the knowledge would be useful if only you design and manufacture components.Knowing what to look for and using the right measuring tools ie, Dyno, Knock Sensor, Lamda,exhaust tempt.. etc are just what you need

What's the point of dumping in high octance fuel if you can't run leaner and more advanced?
Do let me know cause I would gladly switch to 92 octs...i

I'm most probably wrong with all this so do fiil me in :)

Thanks for your comment..but if u getting all the tools with you and u dont pretty understand all the basic theory..dont u think is meaningless?
Let's talk about charge density affects the burn rate.

We need to ignite our charge at the right moment that will trigger our peak combustion pressure around 16 degrees after top dead center. We also know that because the air is more dense and more dense the charge is, the less time needed to complete the burn. This all correlates with gas burn rate, however also know that the faster the engine is turning, the shorter the time for the crank angle to reach that 16 degrees ATDC. so we would need to advance the ignition timing accordingly to rpms. Most so called tuners dont know this.

Obviously the afr and charge density are some big factors affecting the burn rate. as mentioned before the higher charge density will burn faster because of the function of gas pressures and gas temps. chamber size, spark plug location and other factors will also affect burn right, but we wont really be concerned with that for now. Slower burn time reduces pumping efficiency, thats why you want to use the lowest octane that will not detonate. The pure fact of higher octane does not make the fuel burn slower, its actually the chemical composition, many people do not know this either.

Correction Factor. You go and tune the car to a risk taking 12.5:1 AFR on a high boosted application and lets say your intake temps that day on the dyno are 90 degrees. You take it to the track on a cooler night say 65. I can almost promise you, you're going to be over 13:1. Thats another reason why its important to not only tune on a dyno for high boost, but to put the car in real life conditions, things change a bit from the dyno to the street.

Ok, I got down the reason we want a Rich AFR under boost. But what about out of boost?

well im sure you've all heard of Stoichiometric conditions. This is described as 14.7:1 AFR. This is an important number for manufactures because this AFR allows the catalytic converter to maximize its effect of reducing harmful exhaust gas emissions.

This isnt the best in terms of Fuel efficiency. you can lean the motor out as much as possible when you are at lower load levels (cruising).

Anyway, i'm just sharing some basic ideals..and is just my personal experience and it's applied for mostly all racing engine.
 
DRiftAGster said:
does this only applies to skyline engines?? or it applies to any petrol internal combustion engine ???

y here in the Skyline Club thread? just curious....:unsure:
For further more info, pls reply me personally, i will reply your e-mail individual...=.=v
 
yokohama said:
We need to ignite our charge at the right moment that will trigger our peak combustion pressure around 16 degrees after top dead center. We also know that because the air is more dense and more dense the charge is, the less time needed to complete the burn. This all correlates with gas burn rate, however also know that the faster the engine is turning, the shorter the time for the crank angle to reach that 16 degrees ATDC. so we would need to advance the ignition timing accordingly to rpms. Most so called tuners dont know this.


Hi Yokohama,.

Are you suggesting to advance ignition as the rpms go up ? You can't be talking about a turbo charged engine, can you? Or does the RB26 engine has the ablitiy to defy the law of Pyhsics? heeheeehee

This is interesting stuff...why do we need to PM you to get our answers via e-mail? You should share it with all of us, in fact if you keep this up , I might even do a "ASK YOKOHAMA A TECHNICAL QUESTION" section..what do you think?
 
yokohama,

can you kindly introduce yourself? tell us your training background and experiences with mostly all racing engines as you mentioned. what engines you worked on and what involvement you had with them. thanks!
 
interesting talk
but i tak paham

may be need to ask some engineer to teach me one by one
:biggrin: :biggrin:
 
.S K A G E E. said:
Hi Yokohama,.

Are you suggesting to advance ignition as the rpms go up ? You can't be talking about a turbo charged engine, can you? Or does the RB26 engine has the ablitiy to defy the law of Pyhsics? heeheeehee

This is interesting stuff...why do we need to PM you to get our answers via e-mail? You should share it with all of us, in fact if you keep this up , I might even do a "ASK YOKOHAMA A TECHNICAL QUESTION" section..what do you think?

oiskagee!

rb26 kengchau engine la... wat u trying to say ah?? i'm big fan of rb26! u dun talk bad about rb26 ah! hhmmmppp!!!





:lol: :lol:
 
blackie
RB26DETT keng chau engine
want to swap engine ?
i swap a RB26DETT with your 2JZ engine in your car rite now
want ?


:lol:
 
yokohama said:
For further more info, pls reply me personally, i will reply your e-mail individual...=.=v

what info do i need? i dont need any info, i am asking for an answer, not info, its so secretive to share your knowledge here meh??

like skagee says, he can setup another forum for you to share all your technical knowledge with all of us, why have to email?
 

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