Injector placement

[Parker]

We will be tuning our suzuki motor via a simple piggyback system which retains the bike's original sequential injection. My question is whether or not the effects of moving the injector up or down the runner will cause any discernable effect on performance. Should I be worrying about the change in distance to the valves affecting the injector timing? I have done this mod on vehicles equipped with Batch fire before without any adverse affects but am not sure about sequential.

Thanks,
Parker

[Parker]

We will be tuning our suzuki motor via a simple piggyback system which retains the bike's original sequential injection. My question is whether or not the effects of moving the injector up or down the runner will cause any discernable effect on performance. Should I be worrying about the change in distance to the valves affecting the injector timing? I have done this mod on vehicles equipped with Batch fire before without any adverse affects but am not sure about sequential.

Thanks,
Parker

[Cody the Genius]

The effects of changes in injector timing are very minimal in concerns of power gains though it is fairly noticible in terms of fuel economy, which is the major purpose for sequential injection. There are gains from allowing the fuel to atomize from the injector and then not recondense near the valve, though this effect should only be sought when your looking for the last 1% of power.


In my opinion having good injector placement for atomization is much more important than concerns with changing the timing. I would easily justify having compromised the injector timing in order to get the injectors at the right angle and hieght up the runner. The runner diameter, shape, and position of the injectors are major in getting the basics right in order to make power where you want it.


Look forward to seeing you guys at the SAE meeting in Atlanta again and am glad hear how well your doing.

[John Stimpson]

At 5000+RPM, injection timing is already to the point where its not a big issue. By 10krpm, its almost entirely a non-issue. Remember that sequential injection approaches batch as engine speed increases.

That said, with a small engine that already has a hard time making usable power at low rpm, you can run into serious low rpm drivability issues by drastically changing injector placement. Consider what volume of air a (600cc/4) cylinder pulls at 5-10% VE (at idle), and then consider what volume exists between the backside of the intake valve and your injector... Its totaly feasible for the fuel delivered by an injection event to be burned many, many combustion cycles later.