suganuma

I thought I would start a thread concerning fuel injector staging here since there seems to be little traffic in the EMS sections and this applies to all generation turbo rotaries running a staged injector setup.

Many of us making higher power levels are using the Bosch style 160lb (1680cc) secondary injectors with a primary injector sized somewhere in the 550-850cc range. A lot of us are also having issues when the fuel map transitions to the larger injectors sometimes even having a short pause/stutter where the motor goes a little lean. I think most people are running this transition at/around 0 psi.

I was reading in the Haltech manual a few days ago and IIRC I read that it suggested using 60% of the bar pre transition for the first bar after the transition to help it smooth out. If we did this with as large an injector as 1680cc compared to 550 or 850cc it would be dumping a lot of fuel in there.

Thoughts? Advice on what you've found to help smooth the transition?

Maybe we need a tuning section....

TIA,

suganuma

I bring this up b/c I'm having a stutter at partial throttle, high rpm, and low boost (<10 psi) situations getting in and out of the power. I also see a dip in my afr when the injectors are transitioning. I am using 850cc/1680cc injectors on a Haltech E6K. I'm at work so I don't have the map in front of me, but IIRC I have the transition at bar 13.

Silver7

I have been fighting with this transition problem for quite some time now. I'm using 160 lb/72 lb injectors. I've even gone as far as taking my car to KD and letting Dave try to figure it out. No luck there either. This would be a life saving thread if we get anything even slightly useful out of it. I have tried the following:

1)Experimenting with different fuel pressures

2)swapping out different injectors

3)swapping ECUs

4)loading and adjusting several "proven" fuel maps from people who have a similar setup but no hesitaion problems

5)Adding chasis and engine grounds

6) Pulling my hair out (hehe)

Playing with the maps lessens the hesitation but doesn't seem to get rid of it completely. I have called haltech with my concerns and they just told me it was poor tuning.

suganuma

Well, I made a stupid mistake adjusting the map, but have it corrected now. The partial throttle problem is gone now, but I am still having a quick dead spot at WOT going past the transition point. I don't really feel it, I can just see it on a Greddy AFR gauge I have.

Silver7, before I figured out my stupid mistake in the map I found that giving it a little extra fuel on the bar before the transition and the two after really helped to smooth things out.

teeter

I hesitate to try to explain this because its kinda hard to explain completely with words. I like to draw pictures for this kinda thing. And it may not be exactly what is being experienced here...

but...around the 0 psi point is kind of a tricky tuning point with any MAP sensor based tuning. I first saw the behavior in my mitsubishi...and have observed it in every MAP based system since then. I didn't see on the same motor when using a MAF based system.

when using the MAP/intake temp/RPM sensors for tuning...you are utilizing some basic fluid flow equations/laws...that for the same air pressure, temp, velocity(rpm based)...you will have the same air mass flow. Basic assumption here is that you have a constant pressure drop across the ENTIRE system. On a side note this is why adding all the mods makes such a difference...you are violating this basic assumption by changing the entire system pressure drop.

Problem is that with the throttle plates...you don't have a constant pressure drop across the entire system.

example:

lightly cracked throttle plate...barely boosting at 0-1 psi at some specified intake temp and RPM. You have a system pressure drop or efficency of X...based on these readings the ECU dumps X amount of fuel in.

WOT throttle place that is instantly open...you'll instantly be at ~0-1 psi because now you're open to atmosphere...and lets say your intake temp and RPM are exactly the same at that point as the example above. your system pressure drop is MUCH less because the throttle plates are now open...but based on the readings of pressure, temp and rpm...you still get X amount of fuel.

The ECUs try to tune around this by dumping in some "extra" on WOT events for a certain period of time...but in my experience...the lag in our systems is such that that "certain period" of time is never long enough. SO...by adding "a bunch" more fuel right before and 2-3 PSI positive pressure...tends to signifigantly reduce that lean spot you get when going WOT.

having the secondary injectors kick in at the same time will add to the complication...

Granted...this means you are tuning the main maps for transitionary behavior...but what you are sacrificing is your partial throttle acceleration at 1-2 psi. Big deal...you'll have to decide that.

john
chem E.

Michael Filippello

I also had this problem with my power FC. I have 550/1300's. I never had this problem with the stock sizes. As soon as I put in the larger secondaries, I had the stuble. At first everone said it was a rich stumble but it felt more like it was lean. This was the case after confirming with air/fuel meter. There was a lean spot at the transition point.

On the power FC, you can change the overlap settings for 3 different boost readings. This supposedly has to do with the crank position at which the inj. starts to fire. By increasing the #, you start adding fuel earlier i believe. It helped reduce my hesitation but did not completely solve it. This issue also seems to be more problamatic at light to moderate accelerations than at WOT.


Hope this info helps

Mike

enzo250

Try moving the staging bar so that your secondaries come on later. So instead of say 0psi try 2~3 psi.

RETed

I have zero problems running 1600's on Haltechs, but I (initially) run my staging bar at 14 to make tuning easier.



-Ted

little rotor

teeter, you make some good points. I have noticed exactly what your talking about with the transition point between vac. and boost. Interestingly the most noticable case I have seen was on a mitsubishi as well. A turboed 4G63 to be precise. But why is it only the transition point? Why is there not the same effect at say 5psi partial throttle comparted to 5psi WOT?

twokrx7

iTrader: (1)

Many discussions on the PFC forum here about this. The staging is transparent on my PFC with 1600 secondaries after adjusting inj overlap and sec transisiton values with a datalogit.

teeter

I believe it is there as well(higher boost)...but the difference in the pressure drop percentage is just so much smaller that you don't notice it.

you have to just barely crack the throttle to cruise at 0 psi...large permanent pressure drop/inefficency added to the system...but you have to crack it say 40-50% for 5-6psi and by that time you are flowing a lot of air and so the permanent pressure drop created by the throttle body is signifigantly less...in relation to the entire system permanent pressure drop.

I could probably prove that with equations...but don't really feel like it

John

Wargasm

For my 550/1600 setup, I run these settings:

primary lag time 0
secondary lag time 0.20
pri/sec trans% 50
sec trans time (ms) 0.968

injector overlaps
--------------------
14848 7
9984 7
4864 2

I think you should start out with some settings at whatever... like mine or something.

Then change the pri/sec trans% by 10% up or down and see if either one is "better". This can have a large effect, as it shifts WHERE on your map the staging is occuring. For example, having staging occur at 60 mph 5th gear cruising range is BAD because you're always there at a tiny throttle opening and it will hesitate or stumble annoyingly... in other words it's very noticeable there. By moving the trans point around you can get it to work better. Keep in mind when you shift your point around, you may/may not need to fiddle with the overlap ms time.

Anyhow, it took me hours of tuning to get my transition to work right so don't give up! Try to drive the same way in the same gear so you can judge what is working and what is not.

Brian