Megasquirt Port Injection Trial
Turbo Mini Forums

I wonder if you had two injectors per port, one firing upstream, one downstream and calculated the transport delay (hence position relative to the valve) that it could still work with the current code.

I wonder if you had two injectors per port, one firing upstream, one downstream and calculated the transport delay (hence position relative to the valve) that it could still work with the current code.

Just thought that this could be difficult as we dont know the velocity of the jet or the direction of the travelling waves within the port at any one time.
Maybe easier just to try it!

Edited by matnrach on 26th Jan, 2008.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

ve would effect the pulse width , rpm and flow speed the point of inj .in my rarely expressed and ever so humble opinion .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

I have based my calcs on Marcel's method as detailed here:

http://www.starchak.ca/efi/speed.htm

I've applied volumetric efficency to reduce the airflow and get the following results:

http://www.jaservices.co.uk/photos/Injecti...se%20Timing.pdf

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

yep the point is paul , the ve doesnt reflect the mass of air that is going into the cyl , it reflects the mass of air that is going into the cylinder,,,and being trapped there upon the valve shutting ... ,eg
if you have a load of air going out of the ex port in crossover ,then not all of it getting back to the cyl ,your calc will show one ve for the air flow ,and one different ve for the torque output ,this is called in analysis ,'''ve1'' and ''ve2''

another scenario ,is where you have a strong pulse wave tuning effect ,and the density of the gas moving through the port has a certain speed ,but a change in density ,this can really make a mess of calcs based on averages.

looking at the links to marcels stuff , i cant see a component that adresses the fact that the valve is only open fully a few degrees per inlet period and even then the port is not the size of the cross section , but the size of the valve opening ,and then not acting that due to the cross sectional area change as it flows past the valve ,making the port act a lot smaller ,and the rest of the opening sequence the valve is at less than full lift so effectively the port acts even smaller ,also the piston at tdc is not creating the draw it would at 90 degrees to tdc ,so the port again drops flow at tdc ,but then again inertia and port resonance can affect that to create more flow too !
i think the idea to rely upon the torque curve data is a better one ,but you need to get accurate data for that too ,remember that the long stroke engine creats a lot more friction than a modern engine with a shorter stroke ,so results have to take this into account ,the engine may be making a lot of torque ,but what gets to the rollers may be less , and have to worked back theoretically to asses the actual cylinderr torque , unfortunately ,the coast down method used on sun rr's will not measure the internal friction levels unless you want to take it up to 100mph ,and then whip the plugs out as it coasts down and let out the clutch in the test gear ,hey ,that sounds like a fun experiment !

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

This is a very complicated subject if you start to consider what is happening in too much detail. My intention is to try to get a base timing curve that will get the car working and then Sturgeo will fine tune it whist I'm driving it with my eyes fix firmly on the road ahead

I've backward calculated some VE numbers based on a typical power curve for an NA 1275:

http://www.jaservices.co.uk/photos/Airflow%20Calcs.pdf

I've then applied them to the spreadsheet above:

http://www.jaservices.co.uk/photos/Injecti...ming%20RevA.pdf

This is all at WOT, so I know need to consider the effects of vacuum.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

yep thats what i would do too paul , looking at the sheets , i may be drivelling but your not going to get the same bhp at 6k as at 5k if it flows the same amount of air ,due to the internal friction going up maybe 5 to 8 bhp .

hmmm yes vacuumwize its a intersting sit ,air speed i guess must drop as well as density the mass of the charge will be less so inertia lower ,the map for inj point will have to be 3d wont it revs versus map and degrees in the boxes ?oh and air temp compensation, i imaging this is old hat and all the people involved in this know all this , im just getting up to speed being laid up and nothing to do lol.

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

!!!is this whole siamese code allready in existence then paul ?

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

yes it is. Jean finished it and made available for testing quite a while ago.

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

gosh ,the amount of times i ve heard that in the bedroom!
(but not , i should hasten to add ,from paul!)

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

lol!

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Yesterday I read some recent papers to check if Heywood's statements are still confirmed. It looks like they are still true, the fuel film dynamics can be described by a liquid fraction (MAP/engine temperature dependend) and evaporation time (tau, 0.5-1.5 seconds on MPI).
I believe the fuel extra of the inner cyl is the amount of fuel that has evaporate since the outer pulse (1.5 revolution duration) and inner pulse (0.5 revolution duration). So to get the correction we have to do:
<inj pulse> * fuel fraction * 2 * <rev duration> * <custom coeff> / <evaporation time>
It's not very precise as <inj pulse> should be different for both cyls but should work. I'm going to test that may be this WE, the time to implement the algorithm.
All modern correction algorithms work on an event (intake event) and not monotonic rate basis.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

Yesterday I read some recent papers to check if Heywood's statements are still confirmed. It looks like they are still true, the fuel film dynamics can be described by a liquid fraction (MAP/engine temperature dependend) and evaporation time (tau, 0.5-1.5 seconds on MPI).
I believe the fuel extra of the inner cyl is the amount of fuel that has evaporate since the outer pulse (1.5 revolution duration) and inner pulse (0.5 revolution duration). So to get the correction we have to do:
<inj pulse> * <fuel fraction> * 2 * <rev duration> * <custom coeff> / <evaporation time>
It's not very precise as <inj pulse> should be different for both cyls but should work. I'm going to test that may be this WE, the time to implement the algorithm.
All modern correction algorithms work on an event (intake event) and not monotonic rate basis.

Edited by alpa on 1st Feb, 2008.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm

I'm not convinced that evaporation is the problem, but you probably know a lot more than me about this subject, so best of luck.

I'm all excited because I've now got the siamesed code on the ECU, Megatune is talking to it and the .msq file is ready to drop in. The weather forecast for tomorrow is good although its going to be cold.

So watch this space. I'll start a new thread to record the results (if it works OK).

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

Looking forwards to it!

It's going to snow here in Grenoble :(
Looking forward your tests.

std 998 A+, g295, MD266, RHF4, 109hp @0.8bar/5400rpm