998 turbo mod

[NYTurbo]

Yes, I agree (thought I said that?) injectors can (and will be) overtaxed at some point.
But also, the fuel delivery in your example is at a given fp. 88% on a 3-bar system might be 65% on a 4-bar system (didn't do the exact math) because fp is 33% higher (43 psi base vs. 58 psi base). Each injector pulse will deliver maybe 30% more fuel.
I'm not sure what stock injectors can handle pressure-wise. What is too much?
So far so good is all I can say. I like my chances better on a 4-bar tune at the max end (for example waste gate lock installed - max boost - C16) with stock injectors.

I’m not following what your saying here, the only difference between a 3 bar and 4 bar is the amount of pressure they can read , has nothing to do with base Fuel pressure.

 

[justinator]

I’m not following what your saying here, the only difference between a 3 bar and 4 bar is the amount of pressure they can read , has nothing to do with base Fuel pressure.

Precision efi labels there fuel pump regulators in bar so 3 bar regulator is 43.5 psi and 4 bar regulator that is used in stage 4 and up is 58psi. stage 3r and down use 3 bar fuel pressure regulator. Earlier doc asked about 3 and 4 bar map sensors and turboflash was talking about pressure regulators so I think thats where the confusion set in

 

[NYTurbo]

Makes sense .

 

[twyztid]

Do the logging devices for these units allow for logging injector duty cycle? Back in my turbo Eagle Talon days (2.0L Mitsubishi 4G63 engine), I ran a DSMLink ECU and was able to log almost anything I wanted, adjust timing, etc. As I increased the boost on a much larger than factory turbo, I found that I was running 110% injector duty on some 1/4-mile passes. I was told you should shoot for a max of 85% injector duty. Larger injectors cured this. I never had that car on a dyno but I was told that it should have been around 450hp at the crank on this fairly mild build (at 24psi).

 

[NYTurbo]

Not I’m aware of.

 

[earthling]

Do the logging devices for these units allow for logging injector duty cycle? Back in my turbo Eagle Talon days (2.0L Mitsubishi 4G63 engine), I ran a DSMLink ECU and was able to log almost anything I wanted, adjust timing, etc. As I increased the boost on a much larger than factory turbo, I found that I was running 110% injector duty on some 1/4-mile passes. I was told you should shoot for a max of 85% injector duty. Larger injectors cured this. I never had that car on a dyno but I was told that it should have been around 450hp at the crank on this fairly mild build (at 24psi).

You cannot have an injector open for longer than 100% as 100% means it is always open (at least during the timing window). Depending on the setup for that particular engine (open or closed loop, type and points of reference for pressure), the ECU is calculating an effective duty cycle and reporting that.

The tune has injector sizing and fuel pressure as inputs as well as timing (phase alignment) information, while the engine is running it calculates a duty cycle that will meet the timing requirements and fuel demand.

My understanding is that this more or less works because at low RPMs there really is a duty cycle, the manifold is running a vacuum, and fuel is being pulled into the cylinder and there is no pressure compensation by the fuel pressure regulator. As boost builds, the fpr is forcing the system to build more pressure in the fuel system to overcome manifold pressure. In a non-boosted environment the fixed pressure for fuel delivery simply has to exceed the total demand. At some point, the ECU is calculating 100% duty cycle but the effective duty cycle is greater than 100% because more fuel is being delivered than expected or that the ECU can account for based on the injector size and timing. Since it really isn't possible to have an injector open greater than 100%, a reading of 110% must means that the engine is either running lean (which it wasn't) or that the actual (effective) fuel delivery exceeds the expected fuel delivery by 10% or whatever error it is reporting. This also means that you are maxing out your injectors..

 

[twyztid]

You cannot have an injector open for longer than 100% as 100% means it is always open (at least during the timing window). Depending on the setup for that particular engine (open or closed loop, type and points of reference for pressure), the ECU is calculating an effective duty cycle and reporting that.

The tune has injector sizing and fuel pressure as inputs as well as timing (phase alignment) information, while the engine is running it calculates a duty cycle that will meet the timing requirements and fuel demand.

My understanding is that this more or less works because at low RPMs there really is a duty cycle, the manifold is running a vacuum, and fuel is being pulled into the cylinder and there is no pressure compensation by the fuel pressure regulator. As boost builds, the fpr is forcing the system to build more pressure in the fuel system to overcome manifold pressure. In a non-boosted environment the fixed pressure for fuel delivery simply has to exceed the total demand. At some point, the ECU is calculating 100% duty cycle but the effective duty cycle is greater than 100% because more fuel is being delivered than expected or that the ECU can account for based on the injector size and timing. Since it really isn't possible to have an injector open greater than 100%, a reading of 110% must means that the engine is either running lean (which it wasn't) or that the actual (effective) fuel delivery exceeds the expected fuel delivery by 10% or whatever error it is reporting. This also means that you are maxing out your injectors..

Yes, I understand that an injector can't be open more than 100% of the time. I was mentioning what the DSMLink software was reporting and that it was way above the recommended limit of 85% duty.

 

[earthling]

Yes, I understand that an injector can't be open more than 100% of the time. I was mentioning what the DSMLink software was reporting and that it was way above the recommended limit of 85% duty.

Understanding that what the DSMlink was reporting to you was derived (calculated, not actual) you likely have the information you need from your existing logging to calculate duty cycle.

 

[twyztid]

Understanding that what the DSMlink was reporting to you was derived (calculated, not actual) you likely have the information you need from your existing logging to calculate duty cycle.

Sounds like none of what I was mentioning matters anyway if NYTurbo is correct and logging for these can't log injector duty.

 

[earthling]

Not my point. You can calculate duty cycle from the data in the logs. The actual formula is based on injector capacity, air mass (boost), AFR, RPM, displacement, the fact that the engine is a four stroke, has a turbo, pressure is xxpsi, and fuel pressure. The missing component is likely fuel pressure but you can probably get close. About these logs: Do the loggers allow you to save out a CSV file so you can do your own charting? If so, do the samples carry timestamps?

 

[NYTurbo]

Yes I do believe you can get a csv from your log , time stamps are available and I believe the capability to log fuel pressure with the edition of a sensor obviously , was developed but never released by GAP.

 

[earthling]

If someone wants to post a log file as a CSV I can have a look.