MoTeC Global Forum

I have some problems starting a V2 motor. It has low injectors on manifolds and hi injectors as shower injectors. Exact same setup is already running on another bike, curently only on lo injectors.
With this setup, I want to crank and run only with hi injectors. Lo injectors are disconnected (Will be removed in future). Setting the lambda sensors to fast heat allow us to observe a lean value during cranking, even with fuel values doubled/tripled compared to those used at idle.

- To wich set of injectors are directed the first injection and cranking comp when balance=0% ?
- are both set of injectors used during cranking ?

Thanks

Angelo

Primary injectors will ALWAYS give you better cold start and cranking start. You might have to wind the engine over a while to wait for the higher injectors to reach the engine.

even with fuel values doubled/tripled compared to those used at idle.

Try some post start comp, this made a big difference to my engine as soon as it kicks over and runs, it takes around 30 seconds to taper out this fuel trim and settle before it runs completely on the engine temp comp map.

Also injection timing can have some gains on difficult cranking, you need lots of patience to try lots of different configurations of trims and comps before you get close to what you want.

Actualy, the motor will not start at all It has something special. Exhaust cams have a part (don't know the name in english) which push on one valve even during compression, to help the starter motor. This will allow a smaller starter motor and a smaller battery for motorbike weight saving
We first thought setup was flooding everything. We mooved to low values. Still no start. We tried a lot of different setup without success.
Now I am thinking about ignition advance too retarded. We kept the 5° we had with previous version. But I think it should be in the range of 10-20° with these "decompressors".

Angelo

Polux RSV wrote:...
(don't know the name in english)
...
these "decompressors".

Close enough - "Compression Release"
On a large truck they are sometimes called a "Jake Brake"

Low injectors have a reputation for working well at idle and partial throttle.
And high injectors have a reputation for working well at WOT and high RPM.

If you have existing holes and wires for both, it seems to make sense to consider running both.

a little bit about Hi/Lo injection....
Engine is a 4Cylinder with ITBs

red = Exhaust change made to see back to back difference (Ignore)
Orange = Lo injection only, Lambda kept to aim value during run
Blue = Hi Injection only, Lambda kept to same aim value during run

Both were done back to back, directly after each other.

Hi Injectors are not in the runner at all, they are on a mounting point at the trumpet mouth about 30mm outside trumpet. Hi Injectors have a very wide spray pattern. Car was impossible to run in low trumpet airspeed sites with Hi only. Car would not idle with Hi injectors only at all.

Thanks for the info and graphs. The throttle body is vertical, hi injectors spraying on plates even at idle. On the first version I made last year, idle was very good, easy starting, smooth transitions, etc... I was also surprised it worked so good. We want to implement the same setup on the second bike.

And we finally found whats wrong: not enough ignition advance and not enough fuel.


Angelo

Polux RSV wrote:Thanks for the info and graphs. The throttle body is vertical, hi injectors spraying on plates even at idle. On the first version I made last year, idle was very good, easy starting, smooth transitions, etc... I was also surprised it worked so good. We want to implement the same setup on the second bike.

And we finally found whats wrong: not enough ignition advance and not enough fuel.


Angelo

Why would you not use the lower injectors if you already have them in place?

Hi All,
Just to confirm. The starting fuel (First injection etc) are applied to both injectors based on the balance table. If you have 0 in the balance table all starting fuel is delivered through the secondary injectors. Stopped fuel is equal for both sets on injectors no matter what the balance taable is set to.