duty cycle limits standalone vs Me7

[ryan_s3]

Isn't it just dividing the two and working a percentage,like i said a few post back?

 

[m0rk]

does your DTA support twin injectors with different flows?

 

[ryan_s3]

i'd imagine it wouldn't matter mork as it's a combined fueling.

 

[m0rk]

ahh, so treat the pair as 'one' for set up in the ECU.

 

[ibizacupra]

does your DTA support twin injectors with different flows?

yea it does.. wired it for 8 injectors from the start as a plan.

its just a millisecond as far as the ecu is concerned no matter whats fitted. switch over points programmable.

 

[pj1985]

Thankful you wired for 8 injectors and twin rails from the beginning now I bet! If it cant be more than 100% then does it mean it must be a software calculation issue?

P.S- I dont envy your expected fuel bill with that size and many injectors!

 

[Wilko]

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

Bill do you not find it odd that at 3500rpm, where the turbo must be making minimal if any boost, so not much airflow, your large injectors are already open for 22ms?
At constant boost, you would expect injector on time to be similar throughout the rev range, but I'd guess you've got 4psi at 3500, and 18psi at 5000, so injector on time at the same a/f should nearly double, yet it only goes up 10-15 percent?
I'm asuming it's injector on time per rpm?

 

[ibizacupra]

Bill do you not find it odd that at 3500rpm, where the turbo must be making minimal if any boost, so not much airflow, your large injectors are already open for 22ms?
At constant boost, you would expect injector on time to be similar throughout the rev range, but I'd guess you've got 4psi at 3500, and 18psi at 5000, so injector on time at the same a/f should nearly double, yet it only goes up 10-15 percent?
I'm asuming it's injector on time per rpm?

john, these are'nt my ibiza figures, they're off a customer me7 ecu'd ibiza I had a log for.
its just a spreadsheet I threw together to see what figures work out.

13ms was my limit of injector at 8800rpm limiter. we only got to 1.3bar boost when the injectors hit their max duty cycle.

spool wise i think it got to 4psi @ 3500rpm, and by 4000rpm was at the 19psi level as limited by the control valve duty cycle set at that point. seemed slightly better, and certainly no slower to spool than the previous fp red, with comparitive same power output the red was max'd out at from 2.2bar boost vs the gt35's 1.3

DTA alarms when driving injectors >85% duty cycle as a warning, which made me want to review me7 logs I have done as I know I have seen high ms injector times, which when dialed into the rpms they were recorded at, confirms me7 runs beyond 100% duty cycle.. (undersize injectors)

 

[Wilko]

My calcs say a you'd need 730cc injectors to stay under 85% at 8800rpm, 18psi, 100%VE, with a 1893cc engine (you're 83.5 bore?), assuming 12:1 af. Running 11:1, you'd need 790cc, so yes you'd max out your 780's if you're that rich.
For 29lb boost at 8800 which is slightly over max compressor flow for your turbo, you'll need 1003cc injectors asuming 85% dc, 11:1 fueling, and maintaining 100%VE.

 

[ibizacupra]

depending which bsfc number you care to choose, injectors seem to vary between the 1000-1200cc size for my spec according to a number of on-line calculators I have seen.

780 or 840's as singles wont cut it.. makes you wonder how some folks of vortex manage to get these numbers from similarly sized injectors tho..

the single 840cc ones hiy 95% duty cycle at the 1.3bar level tho. twins.. is the way forward.

 

[Wilko]

bill bsfc only gives you power numbers.
I'm working on the basic principle of how much air you can fit into the cubic capacity, times the boost level, and then how much fuel you need for a certain af ratio. All bsfc gives you is a calculated power for the amount of fuel used.
For our engines, working a turbo gently, 0.47 works for me and working the hot side hard, about 0.54 for bsfc. It's an irrelevance though. If you know how much air your engine is consuming (either maf or calculated), then fuel requirements are easy to calculate.

 

[Wilko]

780 or 840's as singles wont cut it.. makes you wonder how some folks of vortex manage to get these numbers from similarly sized injectors tho..

forward.

All about rpm bill. Reving to 8800 needs 15% bigger injectors than 7800.
630's will do a genuine 500bhp, if you make it by 7500rpm, at 12:1 fueling and run 95%dc

 

[ryan_s3]

wilko's are you saying 630's can do 500bhp at max duty cycle? Have seen 4 gt3076R's set-up's all running 500bhp all at 90% duty on 750's ,when pushed to 550ish they were getting near 95% which isn't ideal.

 

[Wilko]

Yes ryan, maxed out (100%dc) at not masively over rich fueling, or excessive revs.
If you want to run 10.5:1 fueling then you need bigger. At 12-12.5:1 they're fine

A 3076 on an evo making 500 must be working the compressor to it's limits. Tuners will be dumping fuel to keep things cool, particularly at the top end. Run enough water meth, and only dump fuel or pull boost if temps get too high, and timing starts to suffer.

 

[ryan_s3]

They make 500bhp at 2 bar held,also make upto 550 at 2.1bar with headwork etc.Tried a 3082 too but did no better then the 76.They run 12 afr flat till 7500/8000rpm redline.No meth etc,super unleaded.

 

[PhilW]

I just worked out my duty cycle on standard injectors and i'm seeing 100-105% from 4k to 6k plus.

Interesting thread...

http://www.seatcupra.net/forums/showthread.php?t=34737

 

[Wilko]

ryan
on an 85 bore, 88 stroke engine 29lb boost, 12:1, 750's at 90%dc at 7500rpm acording to my calcs. Look pretty close to your real world figures, 53lb/min airflow, so a 3076 flat out.

 

[ibizacupra]

bill bsfc only gives you power numbers.
I'm working on the basic principle of how much air you can fit into the cubic capacity, times the boost level, and then how much fuel you need for a certain af ratio. All bsfc gives you is a calculated power for the amount of fuel used.
For our engines, working a turbo gently, 0.47 works for me and working the hot side hard, about 0.54 for bsfc. It's an irrelevance though. If you know how much air your engine is consuming (either maf or calculated), then fuel requirements are easy to calculate.

its also being used to size an expect power output to size suitable injetors.. I have been using 0.5 and 0.55 to approximate my requirements.. BobQ has a good thread from engine dyno tests he did.

Timing wise, so far we were able to run 27-33' at the top end without any sign of det. (yet) Not runnign the snow yet either, so it looks like its flowing nice so far as you would expect from a large turbo at low boost