How injector staging works
 

Ok......
Here's an answer to a question that i get asked almost every day.I noticed a few guys have been having drama's getting their head around the way the staging works & it isn't described real well in the manual either. I'll try to explain this as easy to understand as possible................
The injector staging has NOTHING to do with the secondary injectors.
The % stage value works only on the primaries & works as a percentage of the main load map.It adds fuel by adding to the millisecond value before the switch on point.
for example.......
you have the map stage set at 05",the rpm stage at 3000rpm & the % stage at 50%.Below these points you will be running only on your primary injectors.Say the millisecond value at the current load point is at 1.00m/s,with the stage set at 50% you will in actual fact be running 1.5m/s but only on the primaries.
Once you go above 05" & 3000rpm & the secondary injectors become active,the primary injectors return back to normal (1.00m/s) and all 4 injectors will be running 1.00m/s.
This is why some guys have been playing with the % stage number & the idle is affected.
Adjusting the % stage has no effect once the secondary injectors are switched on.
By moving the % stage value up it it lowers the "step" when the secondaries come in by running the primary injectors at the larger M/S value.
The larger the difference in primary/secondary injector size the higher the % stage value needs to be to get a smooth transition at the switch on point.
Most cars with 550cc primaries & 1600cc secondaries will need to be up around the 95% mark in the % stage.Once you change to a setting like that you will then have to go back & take out fuel in the lower load points to compensate.
I hope that was easy enough to understand!!!!!
RE gards
Jon

OMG thank you so much!! Im going dyno tuning on saturday and this information is going to be so helpfull. I have 760 and 850 cc injectors. When my 850s come online the car wont even rev any higher. So should I set this to about 75% and tune lower maps??

Can we make this Sticky??

PLEASE stick it or else!!

Yes, thanks for the excellent information and support. This makes it a lot easier for us.

Hey, MODS, please make this a sticky

yes Evil makes this a sticky plz

This worked!! with my 760 pri and 850 sec I set the %stage value to 68% (65 still wierdness) and its soo much better!!!

Then all I did was subtract 15% from each load map below 2psi. (65% - 50% = 15%, kept it a little rich) Idle map still needs fine tuning but its going very well. Once I dyno tomarrow I'll post some numbers and hopefully get a good tuning job.

I also changed my secondariy turn on point to 3500 which was suggested by John. Thanks guys!!!

Good to hear!
Good luck on the dyno!

done.

Is there a formal equasion for figuring out what %stage should be based on our injector size??

I just want to see if my 68% is in the ballpark for 760 and 850 injectors. I cannot seem to figure this out on my own.

68% is pretty darn close.
There is no eqation to work it out.Each engine will react differently so it really is just a case of trial & error.

jon,

great info..totally opposite to what i have always thought...do all microtechs work like this?

what i cant understand is why do u want to add %stage onto the primary ms?

so with my car if i change from 1700cc in the primary to 850cc all i need to do is bump the % stage from 50 to 100 and it will run the same as now...before the secondaries come on..

but how would i compensate for the drop in cc of the primarys once the sec come on...

this is to keep the tune the same before its gets dynoed of course.

thanks paul

i suppose i could change the mix trim up by 33.33%

since my total inj size has gone from 6800cc to approx 5100cc.

and lower the main load/idle maps up to say 05hg by 50% and up the %stage to 100?

bloody hell..maybe i should have keep the 4 x 1700cc

as you change the %stg it changes the amount of fuel added in the maps till the injectors stage, so you change the injectors from 1700 to 850 and change the %stg to 99 you should be able to start and drive to the dyno,

thanks mate..... :)

i upped the %stage from 50% to high 90% but it still wouldnt idle so then i upped the idle maps by 50%...

since im running 850 i think i had to go 100% more on the primarys to get the same as i had?

the total cc of my old injectors were 6800cc and my new around 5100cc so i increased the load maps by around 40%...(hopefully a little rich)

i havent had a chance to see if it drives but it starts now :)

i also set the boost cut to 5psi so i dont stuff it :)

Jon,
I have a few questions for you. I am running an LTX-12 on my 20B. When my 20B was stock, I was running an MTX-12. Mycar seemd to run a lot better before I did all the upgrades and work to it!
I have since street ported the motor, went to a single
T-66 turbo and now have the LTX-12 ECU. The car has trouble starting when cold. ( Takes numerous cranks to get it to even fire up and then half way run. ) Once I get it fired up I can get it to run with a slight pedal pressure. Too much gas and it sputters and dies. Once I have it running a minute or two it will idle smoother but wont take a lot of throttle for another minute or two. once it warms up a bit it will idle better and drive with out too much sputtering and bucking. when warmed up it seems ok. Since I am on my own in tuning this thing I dont know where to diagnose the next thing. When I get it all warmed up to temp it will run great with small amounts of boost, but when I nail the throttle say in 3rd or 4 th gear to WOT around 4500-5K and beyond it will sputter and break up making me grind my teeth and back off the throttle. So I can't get it to wind out to red line under WOT. If I am in 4th and then keep it just out of WOT, it will pull like a mother F***er to red line but I have to keep the throttle under control. I also can't seem to run much more than around 10psi with out it freaking out. Do you have any clues or direction that I should look to getting this baby to run to it's full potential? I also can't get it past 125mph in the 1/4 mile. I loose tons of speed when it starts to break up on the track. I know it will run much faster once I can get over this tuning issue.

Derrick, I can help you out with your tuning, and I am local. My name is Peter Burkes, and I am a short ways up north in Austin. I am an associate of Brandon Mattews(no7yet). gimmea shout,
AIM: poindexter10thAE
Yahoo IM: driftfc3s91
email: eightysixed@austin.rr.com

Derrick, I will be at the Texas Rx's meet tonight, I know you are in SA, but if you are coming up to austin, I will see you there. I will have my laptop, bring your car.

How can I wire for stage injection on my 4 cylinder Mazda B8 assuming I am going to run one bank of 4 primary injectors and another bank of 4 secondary injectors?

you have to run batch fire, you put 1,2,3,4 on channels 1 and 2 then your stages on 3 and 4, you will have to run it in batch fire, set the %stg and the map and rpm stage and away you go

Dale

I am running 1000cc primary and 1600cc secondary... What do i need to set the stage and and where will I need to take fuel out of to get it to idle.

Edan

i would start with a 70% %stage and then tune the idle at the idle map in normal mode or the 500rpm map in matrix mode. i would then progress to retune the rest of the load maps to hit your target AFR's. once you get that all done i would keep an eye on the AFR's where the secondaries are set to come online and make sure you don't have any deviations in your AFR curves. they should demonstrate a smooth curve as boost builds.

Ray

jon i have a microtech mt4 running my 13 b bridge port i am having trouble with it it will idle fine but it wont rev as soon as i go to rev it it dies and starts to idle funny any tips on wot to do no one around here where i live will touch it and the nearest tune shop is 2 hours away from where i live

So does it work backwards also? like if im running 4 1600cc injectors do i bring the percentage down to like 20 or 30 so the primary injectors aint completely open?