I've been playing with boost (fun!) and I've been using MAP to stage the injectors instead of RPM. It seems pretty smooth and less jerky at the transition point.. I know I probably don't have it staging right, but it got me thinking; Wouldn't you only care about having secondaries on load, not RPM conditions?

I mean, if I'm at 80 MPH on the highway (Warning, this may be illegal, check local statutes before attempting), I'm right around what, 3500 RPM or so. If I'm only using 10% throttle, and I'm still in vacuum, wouldn't it make more sense to not have the secondaries on? As long as I can keep a proper AFR, of course.

Just thinking about it...

 

You should be using both. Set two parameters for injector staging. I generally use 3500 RPM and 90 KpA.

If you use only one parameter (ie. 90 KpA) then the injectors stage anytime the engine is over 90 KpA, whether it be 1000 RPM or 5000 RPM.

 

I guess my question was why is it a bad thing if the secondaries come on at 90KpA, even if it is 1k? I'd like them to come on and the fuel be perfectly stable before boost enters the picture...

 

I've had a lot of success staging off of the pulsewidth, so that when it reaches 80% or so for primaries, it goes off. The whole point in the secondaries is so that you dont try to work the primaries too hard and max them out, so this is a very nice, direct way of doing this. I think the stock system was MAP and RPM based, plus that is what MS1 supported, so people just continued doing it that way, even though other options were available.

As for when to stage, I found it was much smoother if you set it at 110 kPa; this is still very minimal boost, but it won't trigger at low engine speeds when the turbo can't build any boost so that just cruising around town isn't triggering all sorts of staging events.

 

Good idea, Topless!

 

I use the new table-based staging code to stage. You can't even feel it staging when using this tuned properly.

No matter what I did with the other staging methods, I could find ways to make it stutter a bit in certain conditions.

Ken

 

Which version is that on, Ken? That's what was bothering me about the RPM range one, it seemed a lot more pronounced than doing it with MAP, but a table would be the best I think.

Edit: I'm running 2.25p3 right now.