waterinjection.info  

Go Back   waterinjection.info > Injection Applications (making it work) > Gasoline Forced-Induction

 
 
Thread Tools Display Modes
Prev Previous Post   Next Post Next
  #11  
Old 30-09-2004, 09:17 PM
b_boy b_boy is offline
Member
 
Join Date: Feb 2004
Location: Seattle, WA
Posts: 45
Default

This is fascinating stuff!

I'm a biologist so my understanding can only go so far, but the physics is not so great that I can appreciate the content.

So, back to tuning.

HotRod suggests something that I've wondered for some time, that is, that fine tuning the water injection can permit an optimal balance between fuel, air , and power. This idea suggests a method of tuning quite different than is ordinarily taken. Whether the "angle", or the rate of burn, or the speed of the flame front is slowed by water injection is slowed, the effect with respect to tuning is the same: ignition needs to be retarded to achieve MBT.

We have a number effects happening in close succession: cooling of the charge, cooling of the cylinder, slowing of the rate/flame, and augmentation of the combustion itself. Most of these variables will affect ignition timing, not fuel. While WI permits more boost, thus more air, and a denser air, also more air, these WI effects are occuring pre-cylinder. The remainder are in cylinder effects.

Why is this important?

Well fueling is going to hover at a near constant ration of 12.5 to one. Thus from a tuning stand point fuel addition is constant value with respect to air mass. When tuning, fuel can be pulled back to this empirically derived minimum and left there.

Once fuel is set, the tuner has a choice: retard timing or reduce water injection. From the above discussion, I would say that reducing water is the first choice, finding a level that still permits 12.5 AFR and no knock. If the ignition advance (set by tuning with WI off) is still too little for peak power, advance can be further retarded to increase power.

In the end, a tuner will have achieved higher boost, cooler charge temp, elimination of knock, minimal water usage, and maximum power.

Now back to fuel

Is 12.5 AFR the goal for most power? I will suggest a way that this might be determined. If we use gas of differing octane, does the AFR of maximum power change? The octane rating everyone knows is a misnomer. It should be anti-knock rating, and the chemical composition of different octane fuels is different. While the maximum fuel efficiency occurs at around 14.5:1 AFR, I can see that "waiting" for the final stochiometric combustion products to form would be a detrimate to power production. The time associated with "waiting" for the final byproducts would probably hover close to a percentage of fuel left incompletely burned, no matter what the octane number.

Above is the perspective of engineer or scientist. In the real world of tuning another perspective holds. More fuel, means more power. While the 12.5:1 AFR may produce the most power per unit fuel, adding additional fuel may produce more engine power per unit time. My anecdotal observation is that no tuner tunes to greater than 12:1 AFR, usually 11.6-11.8:1 even with huge intercoolers and race gas.

Please comment on the difference.

Next I'd like to do another 1,2,3...tuning method revised to incorporate all of this discussion.
Reply With Quote
 

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On

Forum Jump


All times are GMT +1. The time now is 07:15 AM.


Powered by vBulletin® Version 3.8.4
Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.