generally speaking, more air = more torque and equally more power.

assuming you run the same fuel, and run the max advance before detonation, you will make more power with more boost.

Your limit on advance will be lower with more cylinder pressure, but more cylinder pressure results in more power.

It's not a simple question that can have a simple answer. I think that's the problem.

in general, you want to get the most air you can in the motor to make power. Advancing to the knock limit for a given boost level will not increase the amount of air you have to work with. It will only maximize the cylinder pressure you create with the availible air. Upping the boost, providing an addition source of oxygen (nitrous), or increaseing the efficiency of the motor as a pump are the ways to increase availible air.

 

oh yeah, or add more cubes <img border="0" title="" alt="[Big Grin]" src="gr_grin.gif" />

 

ive herd a roumor that reversing the coolant flow through the engine, say return from the rad to the heads first then out of the block back to the rad may lower cylinder running temps,
hence cooling the cylinder head most where combustion takes place, allowing a little more ignition advance.
what do you think? anyone try this?

 

has anyone out there run a blower or turbo with nitrous?
if so ,please share your system and specs ,
like max timeing with said boost.
then how much timeing retard at said boost with nitrous applied.

 

Midengine, I have not heard of the coolant trick . . . also have not run NOS with turbo . . . I think some have sprayed a small shot though.

So Harlan . . . do you run pump gas at all? I'm just trying to figure out how low I should go on advance to run more boost on pump gas . . . I think I'm sitting at a low of 17 or 18 degrees right now . . .

- Dug

 

Let's say you can run 5psi with about 22 degrees of timing on 91 octane. You're running to the limits of the fuel, as you get knock when you bump it to 23 degrees. But does it make sense to pull back an additional 6 degrees so you're at 17 degrees, and then run more boost? What's the tradeoff? I hear some people say minimal timing, maximum boost, and then other people say the exact opposite.

HI DUG
Lets look at this a little closer,

in my first post i stated that the only time i retard the engines timeing , usually no lower than 15 degrees , is when the engine is not loaded very much and are running in vacume. (throttle plate closed)
and that retarding the timeing,creates heat ,lowers power , causeing the throttle plates to open up and run the engine ,( at the same load) at higher manifold pressure.

When i retarded it i added boost because the throttle plate opened up and let in the reserve turbo air in right,

lets leave fuel quality out of the picture for now , and just look at the timeing.

most people look at the timeing as the start of ignition in relation to crankshaft degrees before top dead center, true, but what happens after the the spark?

timeing is not only the start of ignition but the duration of the flame front and pressure building time, to peak cylinder pressure and then as the pressure falls off, AFTER top dead center.
YES timeing is important after top dead center!


to understand how the engine reacts to the timeing we have to look to the crankshaft!

the crankshaft is just a lever,a lever from the center of the rod journal to the centerline of the mains .

remember when you were a kid rideing a bike,
and when you went up a hill , you would push with your feet and the best power to move along was(if the petal was up at top = TDC) from
20 degrees,BTDC to say 40 degrees ATDC.
the first 20 degrees was the hardest, then you hit TDC and it got easyer and you were rolling,
after 40 DEG ATDC The leverage fell off, no power no torque until the other petal came up to 20 deg btdc you pushed and away you went again.
power and torque.

lets call tdc to 40 degrees ATDC the sweet spot! (ideal mechanical advantage)

ALL DEGREES ARE FICTISOUS AND USED FOR EXAMPLE

now back to the engine,
we run engines with advanced timeing because of the speed of the crankshaft relitive to the time of spark to peak cylinder pressure pushing on the crankshaft after tdc.

the faster the crank turns the more advance we need to stay in the sweet spot of makeing torque and horse power,
we are keeping the cylinder max pressure between tdc and 40 deg because after 40 degrees
the mechanical advantage is lost and all the power goes out the tail pipe.

that is what happened to the engine when i retarded the timeing from a fine tuned position of perfect o2 and best timeing for fuel quality.
remember i only did this to make the oil hotter!

i retarded the timeing past the sweet spot and started looseing horsepower and torque, the govener saw the speed was decreaseing and gave the engine more throttle added boost just to try to maintain the speed , i could have kept retarding the timeing until the throttle was wide open, if i had run it retarded and wide open like that for some time the cylinder temps would have burnt the valves out of the heads.

so running with excessive retarded timeing and adding boost does not make horse power,
if you retard it out of the sweet spot.

back to the bike,

if a ten year old girl and a body builder had a race to the end of the block, and the ten year old was running the petal timeing advanced, pushing at 20 degree btdc and the body builder started pushing his petals 30 degrees atdc
who would win?

hope you said the girl !

now how do we make absolute boosted max power then?
back to the fuel quality,

you have to run the highest octane you can c110 or better yet c112, so you can run the timeing as advanced as you can maybe up to 30 degrees then work on bringing up the boost

if you are only running 92 octane all you can do
is find a balance between your boost and max advance and know your power is limited due of course to the low octane fuel.

there are alot of variables ,this is just my view .hope you are amused and this gives you something to think about