duty cycle limits standalone vs Me7

[ibizacupra]

I had an interesting find yesterday when mapping the badgerwagen.... on what I thought to be as bought 870cc injectors.. (turn out to be 780cc injectors... fecking suppliers!)

anyhows.. starting at max throttle positions first to see if a problem would show itself, we got as far as 1.3bar boost before running out of injector duty cycle. Some head scratching done at that point.. Checked fuel pressure under power run again and under boost rail pressure was 5.5bar so all there ok and sustained. Not pump then.

swapped injectors for some known 620 siemens ones, and ran again... lean... adjusted them up by the difference in delivery size, re-ran and all was as before, but ran out of fueling from these early up the rpm.. 5500rpm out of puff.

break out the fluke meter which had injector millisecond and duty cycle.. which confirmed indeed that injector duty cycle was going 95% as reported by my standalone DTA.

I am sure I have seen >12ms injector milliseconds on me7 vag-com logging, which at my new rpms of 8800rpm is max'd duty cycle.

Duty cycle is a function of rpm and millisecond opening, so not technically variable... fully open (saturated). Fully open is open.

How is Me7 or vag-com reporting these duty cycles and reported millisecond durations... as from logs I have done before on mine before DTA, my injectors were saturated.

from an on-line site we found yesterday, injectors I will be needing will sit between 1200-1400cc size to run at a max of 85% duty cycle.

2 x 4 injectors it is then.
SEM going to be modified for additional fuel rail etc...

something is mis-reporting injector opengins in me7 tho.
physical fluke meter confirmed saturation so its a real phenomena..

Anyone got suggestions?

 

[ibizacupra]

been reviewing some logs... and some customer cars have logged injector ms which run to 113% duty cycle.. so vag-com or me7 is reporting injectors stuck open.

 

[m0rk]

curious.... you'd think that 113% of something that should only be 100% would be impossible.

unless it's 100% of some 'limit' rather than (as you would expect) the open time / open+closed time

 

[m0rk]

just found some 1200cc injectors @ $1200 looked like these

 

[DPJ]

Injector pulse width must be mistimed - there can't be another answer....

 

[pj1985]

Been thinkng about this since you posted it yesterday and its got to be either what Mork said as in 100% is only 100% of a certain set limit not of the injectors actual max or that the software is not reading right.

Got any logs of a totally standard car Bill? And one with standard injectors but mapped? Does this only happen on mapped car, only ones with larger injectors?

 

[ryan_s3]

bear in mind the duty cycle is a measurement of injector open time vs available valve open time - as I've been told touring car engines run up to 108% on MoTeC.
4 x 1000cc injectors have done 680bhp on v-power and 800bhp on race gas should be more than up to the job on a gt35R mate.
Not sure on prices on vag stuff but i can get a set of Evo RC 1000's for £300.
http://www.rceng.com/Peak-Hold-Fuel-Injectors-C5.aspx
just had a quick look at the worksheet and it says 1200cc for 85% at 650bhp @ 3 bar but at 5.5bar fuel rail pressure 1000cc good for 730bhp!

 

[DPJ]

bear in mind the duty cycle is a measurement of injector open time vs available valve open time -

I thought it was a % of the whole Otto cycle - ie 2 complete engine revolutions.

 

[DPJ]

Do you think it's a case that Me7 doesn't have a maximum Injector Pulse Width written in, so therefore it could ask for pulses whose time length are greater than 100% ?

Vag Com is then reported 'requested'......

 

[ryan_s3]

Just means that the ecu is saying the injectors would need be open 108% of the time to achieve requested afr levels,obviously it cannot go past 100%(static) in reality.

 

[ibizacupra]

just found some 1200cc injectors @ $1200 looked like these

lol @ m0rk

 

[Feel]

bear in mind the duty cycle is a measurement of injector open time vs available valve open time - as I've been told touring car engines run up to 108% on MoTeC.

That makes sense...

So on Mr Bill's, with different cams, do the valve open earlier/close later than stock? That would further extend the duty cycle value, wouldn't it?

I read somewhere about them spraying a little when the valve was closed...

I thought it was a % of the whole Otto cycle - ie 2 complete engine revolutions.

That doesn't - even if the injector was spraying the whole time the inlet valve was open, the maximum you would see would be something like 25%

 

[ibizacupra]

Been thinkng about this since you posted it yesterday and its got to be either what Mork said as in 100% is only 100% of a certain set limit not of the injectors actual max or that the software is not reading right.

Got any logs of a totally standard car Bill? And one with standard injectors but mapped? Does this only happen on mapped car, only ones with larger injectors?

the duty cycle is calculated.. not reported from vagcom.
take an engine rpm... convert its injector firing opportunity to time and you factor in the injector millisconds, and you get the % duty cycle

as said its the available time which the injector has to open vs the engine rpm..

the vagcom logs I have reviewed have shown an apparent 113% duty cycle.

 

[ibizacupra]

bear in mind the duty cycle is a measurement of injector open time vs available valve open time - as I've been told touring car engines run up to 108% on MoTeC.
4 x 1000cc injectors have done 680bhp on v-power and 800bhp on race gas should be more than up to the job on a gt35R mate.
Not sure on prices on vag stuff but i can get a set of Evo RC 1000's for £300.
http://www.rceng.com/Peak-Hold-Fuel-Injectors-C5.aspx
just had a quick look at the worksheet and it says 1200cc for 85% at 650bhp @ 3 bar but at 5.5bar fuel rail pressure 1000cc good for 730bhp!

you cant go beyond 100% duty cycle.. 100% is continuously on as is anything >100%

peak & hold injectors have been suggested to me (low impedance) which I can run on dta with suitable load resistors.

controlling single large injectors on low end tho is not easy.

twin rail, 8 injectors are what I will run with and get my 750cc and 840cc injectors in the twin rails.

surprised tho.. me7 is doing something beyond 100% duty cycle.

 

[ibizacupra]

That makes sense...

So on Mr Bill's, with different cams, do the valve open earlier/close later than stock? That would further extend the duty cycle value, wouldn't it?

I read somewhere about them spraying a little when the valve was closed...



That doesn't - even if the injector was spraying the whole time the inlet valve was open, the maximum you would see would be something like 25%

nope its related to engine rpm

 

[ryan_s3]

You can get 1000's to idle at 1000rpm no probs.
Alot easier set-up than twins mate.
As stated above a real 100% duty is static.Wonder what hooch's 440's are doing?Prob 150%

 

[ryan_s3]

yep it's the time to do two full engines cycle(100%) to the injector pulse width in percentage.

 

[ibizacupra]

rpm	milliseconds
1000	0.120
2000	0.060
3000	0.040
4000	0.030
5000	0.024
6000	0.020
7000	0.017
8000	0.015
8800	0.014
9000	0.013

available injector ms @ 100% duty cycle

 

[DPJ]

That doesn't - even if the injector was spraying the whole time the inlet valve was open, the maximum you would see would be something like 25%

Clicky.

As Bill says, 100% means the Injector is continually on. As I see it, with the inlet valve closed and the injector spraying, it's loading the air charge ready for the next inlet stroke.

 

[ibizacupra]

rpm	milliseconds	injector ipw	duty cycle%
1000	0.120	0.015	12.5
2000	0.060	0.015	25.0
3000	0.040	0.015	37.5
4000	0.030	0.015	50.0
5000	0.024	0.015	62.5
6000	0.020	0.015	75.0
7000	0.017	0.015	87.5
8000	0.015	0.015	100.0
8800	0.014	0.015	110.0
9000	0.013	0.015	112.5
from logs
3560	0.034	0.02255	66.9
4360	0.028	0.02583	93.8
5040	0.024	0.02583	108.5
5040	0.024	0.02706	113.7