rollin road RESULT!!!!!!!!

bens_cab said

no 0.7 ish bar is atmosphere pressure 100kpa i think

1 atm = 1.01325 bar = 101325 Pa = 101.325 kPa = 14.7psi

Beware also, gauge and absolute pressure measurements. Gauge measures the difference between pressure measured and atmospheric pressue, so you can have -0.3 bar g for example, to represent 0.7 bar absolute.

1.01325 bar absolute = 0 bar gauge
2.01324 bar absolute = 1 bar gauge

so there is never any pressure in the manifold just vaccum or normal atmospheric pressure?

thats the one with my ignition on my active map bin sits at 100kpa then drops to 25kpa once running and doesnt increase until the pedal is applied

heres a random fuel map from megasquirt to the left you have your kpa and the bottom row is rpm as the rpm increase the kpa increases to the fuel bin betwen the two

cabriaulait said

so there is never any pressure in the manifold just vaccum or normal atmospheric pressure?

There is always pressure in the manifold, but on a normally aspirated car, its always less than atmospheric pressure.

On a turbocharged (or supercharged) car, the pressure would range from below atmospheric (say, 0.15 bar) to above, say 1.75 bar. Most turbo boost gauges would read this as 0.75 bar of boost, though, and not 1.75 bar, since they are measuring gauge pressure not absolute.

Note, that 'supercharging' as in not normally aspirated, could include a number of things you might have forgotten about, including ram-air effect.

Also remember that normal atmospheric pressure varies with the weather, but not significantly.

the numbers in the map are your ve so fuel

your car wont have a map but the metering head will do a similar thing i guess using the vac and rpm

with mine i can adjust each bin to richen or lean out the map where cruise is at 40kpa the ve is smaller so less fuel the higher the kpa and rpm or load the more fuel

interesting partic the diagonal why the drop ayt 2500?

i read on the ms forum that one guy was struggling with his map because the atmosphere pressures in canada varied not sure how this would effect the map but i guess

if your up the top of everest say the atmosphere pressure is gonna be pretty high  

that map is just a random one which probaly isnt tuned just gives you a rough idea on how kpa and rpm effect fueling

bens_cab said

the numbers in the map are your ve so fuel

your car wont have a map but the metering head will do a similar thing i guess using the vac and rpm

with mine i can adjust each bin to richen or lean out the map where cruise is at 40kpa the ve is smaller so less fuel the higher the kpa and rpm or load the more fuel

On a K-Jet car, the manifold pressure and rpm both have an influence on the mass of air sucked in, and its the air against the air flap (acting against a spring, or more accurately the spring partially compensates for gravity) which pushes the lever which pushes the needle valve which controls the fuel pressure which controls the amount of fuel delivered.

The air/fuel ratio 'map' is optimised and fixed, by the slope of the sides of the cone in which the air flap rises in. So the amount of fuel delivered, against the mass of air flowed, doesn't necessarily follow a constant relationship.

Later developments (Mk2 16V, Audis) also had a WUR which had a vacuum input from the manifold, so they could alter the fuel pressure and thus compensate for leaning out at WOT (ie during acceleration). Later still, various solenoids were used to fiddle around with the fuel pressure, under electronic control, in the KE-Jet system. The combined the basic mechanical control of the fuelling, with adjustments done by a closed loop control system, which was fine enough to allow a cat to run (cats are damaged by overfuelling and thus need the lambda in the range 0.98-1.02).

PS Lambda is the proportion away from optimal stoichiometric, ie AFR of 14.7:1 (by mass = lambda 1. Remember though, that max power is achieved at AFR around 13, ie lambda 0.88 or so.

bens_cab said

i read on the ms forum that one guy was struggling with his map because the atmosphere pressures in canada varied not sure how this would effect the map but i guess

if your up the top of everest say the atmosphere pressure is gonna be pretty high  

Pressure is lower as elevation increases. After all, the pressure is from the mass of the air above us (pulled down by gravity) so the combination of less air above, plus the gravitational force being less, the further from a planet you are (in a squared relationship) makes less force.

Also, of course with less pressure at the same temperature, there is less mass of air. So less fuel can be burned with it, lowering power.

cabriaulait, if you're trying to understand all this, you're best off seeking a decent text book, since ben and I are randomly meandering through several areas of the gas laws, thermodynamic principles, combustion chemistry etc.

ive got a lambda chart somewhere which gives voltage to afr conversion must dig it out

i could never get my head around the whole k-jet thing wasnt until i got my ecu and could see how the map worked that i started to unsterstand it a bit more


paul your just a fountain of knowledge :wink:

its supprising how differently the k-jet versus efi varies i know k-jet is more of a mechanical system but with the efi maps it seems to make it look simpler

im so used to having maps now that id be lost with a k-jet engine i think its harder to tune due to all the varying factors like spark advance ect

i was never one for chemistry unless it involved killing somthing or blowing somthing up    

im with ya paul dont fret, abreviations slow me down mind!

itll come in time.

i wonder weather theres a need for a sub forum for tuning as its quite spread about on the forum in different areas like this thread
 :dontknow:

defo
reckon it puts peeps off when it starts gettin in depth, needs to be seperated.

i did a compression test a while ago cant remember exact results but around 165ish i think

it seems low on torque /bhp

i put it down to compression yes?

not sure mate dont think your bhp is effected as it seems above average anyway i would say

you can see where it leans out on that rr printout :wink:

i think theres so many posts on how to adjust fueling and map and timing for perfomance gains it would be good to have them in one place could even add 1/4 mile times ect for each show :dontknow:

and build up evidence for mods, r/r graphs etc

cabriaulait said

defo
reckon it puts peeps off when it starts gettin in depth, needs to be seperated.

i did a compression test a while ago cant remember exact results but around 165ish i think

it seems low on torque /bhp

i put it down to compression yes?

Nope!

Power = torque x speed

So if you achieve low torque compared to power, all it means is that you've achieved the power at high rpm.