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4cyl NA fuel starved at 3K rpm


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Hope you can help a novice,  got a storm blue ecu installed on a Porsche 944 S2 over the weekend, car will idle fine but I'm having problems getting the car to rev past 3,000 rpm without going extremely lean/misfiring.  I'm using LS2 Truck coils for ignition, stock injectors, and a 36-2 trigger with the stock hall sensor.  I'm not getting any trigger errors to suggest the timing is thrown at high RPMS. Is there anything that screams to you as setup incorrectly in this setup file and log? 

 

Thanks

 

 

 

 

basetune944s2.pclr

Long Start up.llg

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I only had a brief look but dont see much wrong in your map and log.  In the log you have taken it to ~3700 but it is still showing correct or richer than target lambda.

However I am suspicious either the injectors are too small or there is a fuel delivery/pressure problem - You are already at 45% duty cycle at 3500RPM and only 25% throttle so it is going to run out of "injector" very quickly.

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 I agree,  it feels like the injectors begin to shut down at higher RPMS. What determines the duty cycle in traditional mode?  I see I can enter injector data if I switch to modeled fuel (shows 999cc/min Mine are 315cc/min).  

I'm just trying to wrap my head around why the stock injectors worked fine before the switch to Link, but now they're 'underpowered'.  I installed 4.7 ohm 25w resistors on the power supply to each injector (they're 2.8ohm peak-hold stock) per recommendations on the forum because the storm blue doesn't have peak-hold drivers, would that cause the problem?

 

 

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Ok, so I think I found that the duty cycle is just the percentage of Pulse Width vs Time available to fire.  And starting pulse width is set by master fuel #?

So at 3000 rpms, I have ~ 40ms to fire the injector and it's taking ~18ms of the injector open to flow sufficient fuel to hit target lambda (which is purposefully rich right now).   So when load or more RPMS are introduced the injector has to stay open for the full duration of the increasingly shorter rotation and thus its not getting enough fuel?

My fuel pressure is steady at the rail, ~50PSI raises to 55 briefly under acceleration, doesn't drop at higher rpms. (hard to see when driving). So if fuel volume was an issue I should see the PSI Drop as it becomes starved for fuel, right?

Now I'm going back to the in line resistors with peak hold injectors on a saturated driver.  Would that cause the injectors to not 'open' completely?  Should I be looking for replacement high impedance injectors with more flow?

I believe I am at the upper limit HP wise for the stock injectors, which are 30lb/hr injectors and the car is making ~220 hp.

 

Thanks again.

 

 

 

 

 

 

 

 

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I just done some calcs on fuel flow and assuming your injectors really do still flow 30lb then they should be adequate for 220HP.  So perhaps they arent fully opening/staying open due to current/driver?  The ballast setup normally works ok so it would be unusual not to work correctly but I dont have any other explanation for your observations. 

If it were me and budget was a consideration I would go to u-pull-it or whatever you have locally and find a cheap high resistance injector out of a modern engine with similar horse power level.

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It was the ballast resistor/low impedance injector combo.  The new high impedance injectors work great. Cars running awesome, just need to adjust the tune for the higher fuel volume.

 

Is there any downside to having high fuel table numbers?  The help file says to target numbers in the 50's,  the samples I've seen online are in the teens, my table is a range of 60-110 (haven't tuned it yet).  As I understand it I can adjust the Master fuel and it will raise/lower this range?

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Good news. 

As for your fuel table numbers, your logic is correct in that the Fuel master and Fuel table numbers are directly related.  If you increase fuel master by 50%, then you decrease the Fuel table numbers by 50% to end up the same.

However if you are only peaking around 110% in your fuel table then I would just leave it alone, that is perfectly fine (or even preferable).  The biggest number you can enter is 150% so our suggestion to aim for around 50% in the middle of the table is just to ensure users didnt run out of adjustment when they got to the high load areas.  Usually it is only when fuel pump isnt keeping up or some other hardware problem that you would need that much range.

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