Alternating/Simultaneous problems

mops · Post by **mops** » Thu Jun 08, 2006 2:49 pm

1. I think the firing order is 1-3-2-4

2. same issue is being discussed for bmw e30 cars. aparently some of them have stock injectors wiring as follows :
bank A - 1, 2, 3
bank B - 4, 5, 6

and some other have aparently as follows:
bank A - 1, 3, 5
bank B - 2, 4, 6

to make it furhter complicated some early motronic ECU's seem to fire bank A then bank B per cycle, while some others fire AAABBB in one cycle.
Go figure....

I presume the problem is that the objective of them game is to obtain even cylinder filling, while problem with bad injector sqeuence arranging might result is some injections happening on the open valve, while others not making then engine uneven...

Since i learned about this issue I switched from 2 squirts alternating to 6 squirts alternating and I have to admint, some of my wierd tuning issues dissapeared, but I cant confirm that the injector sqeuencinf fixed that. I learned how to make MS do what I want to happen instead of just blindly following manual.

MSBoostedEscort · Post by **MSBoostedEscort** » Thu Jun 08, 2006 7:28 pm

im prety sure when it fires the first event its filling the plenum with fuel then on the second event it actualy fires on the intake stroke so you get both squirts.... but im not sure, this is just some of the theorys i came up when i was tuning.. and still am

coyoteboy · Post by **coyoteboy** » Fri Jun 09, 2006 2:10 am

That might be the case with
throttle body injection but my injectors point right at the back of the valve so unless you do sequential youre always gonna squirt onto a closed valve at some point, even if you run alt/4 squirts, one of the two squirts for each valve will hit a closed one.

Incidentally i tried alt/4 last night and the car really wasnt happy with it. Im already bouncing off 80% DC on the stock injectors so going to 6 squirts will probably end up with them burning out or floating!

J

mops · Post by **mops** » Fri Jun 09, 2006 2:23 am

on 4 cyl car you cant run 6 squirts... my car is 6 pot, so i run that.

you cant switch from 2 to 4 squirts without retune. unless you injector opening time, pwm and voltage correction settings are 100% correct.

when i switched from 2 alternating to 6 alternating i had to do pretty much full ve table retune.

If i understand it correctly on my 6 pot, running 6 alternating squirts, every cylinder is going to get 2 squirts on the closed valve and one when the valve is open. they key things here is that it's going to be equal and always the same, as opposed to 2 squirts per cycle, where in case of 6 pot, one cylinder will be filled via open valve while two others will get squirt on closed valve.

if i'm wrong please correct me...

coyoteboy · Post by **coyoteboy** » Fri Jun 09, 2006 2:47 am

Hehe good point about the 6, i wrote that without engaging brain lol. It would be 8 i guess next!

I'm fairly sure my injector settings are correct, ive had information from someone who has scoped them to get the opening times and they're running behind resistors so theyre running 100% and full time threshold (25.4 IIRC?). Still fell over and felt like it was flooding, maybe my injector opening time is actually longer than first thought so its getting much more fuel with two openings? My req_fuel is 7.6 with with normal alt/2 but it halves with alt/4 and you're supposed to keep it around 8-12 IIRC? Or is that the 'top' req_fuel only? I might give retuning with alt/4 a go if we think its worth it - alt/4 on a 4 pot has to give one closed and one open squirt? How is this so hard to visualise

?

J

keithmac · Post by **keithmac** » Fri Jun 09, 2006 9:50 am

I run 2 squirt alternating on my 4 cylinder, runs great, rock solid idle. Bear in mind if you go to 4 squirts the injectors will be shut more often, this can upset the idle PW if you have big injectors or push you over the edge duty-cycle wise at the top end if they aren`t big enough..