Injector Duty Cycle

[TurboChrged93]

Recently installed Stage 3 Eprom with all the goodies including injector compensation.

Importantly noted mods:
BEP 50 Trim @ 20 PSI
GM MAF/T
SAFC II
FMIC
Walbro 255 HP
Aeromotive AFPR @ 38 PSI Base
FIC 650s
264/272s
3" Exhaust
Adj. Cam Gears
And all your usual bolt ons.

Upon logging with my chip freshly installed, I put the MAF/T for 450cc injectors with no corrections. I have my SAFC II set at about -5% across the board and all my fuel trims are LFTR 99.2%, MFTR 100%, HFTR 99.2% Which in my book is excellent. WOT pulls i get about 15 knock sum from 5800 RPMS on up but the car pulls like a pig. Timing is about 15 degrees WOT give or take 1/2 degrees. My injector duty cycle is hitting about 106%. How is this possible? I can honestly say I don't fully comprehend and understand all of these values completely, but I have a decent head on. Any suggestions with this situation?

 

[TurboChrged93]

By the way. According to my SAFC I'm hitting over 3000 hertz. Isn't that alot of airflow?

 

[DGajre777]

I say that you either don't have 650cc injectors or your map on the chip was based at a different base fuel pressure.

 

[TurboChrged93]

I say that you either don't have 650cc injectors or your map on the chip was based at a different base fuel pressure.

Definitely are 650s and i hope the chip is flashed correctly. I just recieved it from Nate @ keydiver.

 

[CanadianTSi]

Simple, your MAF-T isn't calibrated and is giving you screwy(high) airflow readings like that almost always do.

 

[TurboChrged93]

I realized how much of a piece of junk the MAF/T is. But you think that is my primary and only problem? I mean... flowing 3300 hertz is a bit much isn't it? What is another alternative to a MAF/T that isn't ridiculously priced.

 

[tom04841]

Speed Density chip.....free if you have a programmer for your chip.

Gm 3 Bar Map sensor............@ $65
Connector for Sensor............@ $15
GM AIT Sensor w/ connect.....@ 15

Other than that, you just need to wire it up, and tune it.

I have been running this for a month and LOVE it. Throttle response is great, and if you have boost leaks (small or big), car won't run like ASS.

All the info you need about it is at DS-MAP

 

[Reese92tsi]

It looks like you have a case of rich knock. lean it out some.

 

[CanadianTSi]

I realized how much of a piece of junk the MAF/T is. But you think that is my primary and only problem? I mean... flowing 3300 hertz is a bit much isn't it? What is another alternative to a MAF/T that isn't ridiculously priced.

Yes there is no way your flowing 3300hz.

As for a good Alternative, a 2G MAS is good for 50lbs/min of airflow...

 

[TurboChrged93]

It looks like you have a case of rich knock. lean it out some.

Now shall I lean it out via fuel pressure, or via piggy back. The whole reason I went with a keydiver chip is so that I don't have to make such big corrections with my piggy back units. Thus advancing timing too much and blah blah blah you understand. Everyone I talked to had to make minimum corrections after the chip. Why me? I don't trust my MAF/T worth more than a paper clip actually holding papers together. ^^Those settings I have listed above, are those correct for 450cc injectors and that IS what I should have it set at correct? Thanks for all the input guys, keep it coming. I've been fighting with this car for quite a bit now.

 

[Reese92tsi]

The GM maf has to be scaled before it will read like the stock sensor. It looks like you have the low airflow areas tuned pretty well so just lean out WOT some with the MAFT. If leaning out yields too much timing you'll just have to retard the CAS a little.

 

[TurboChrged93]

I shouldn't have to make such large corrections on my piggy back with this chip. Wahhh I'm crying. Thanks guys for all your input again.

 

[oldman]

The grossly mis-informed post has been removed to keep the thread clean, please continue.

 

[TurboChrged93]

Wait, what was removed?

 

[oldman]

Wait, what was removed?

The part about setting maft to 650s even when already e-promed for 650s.

 

[steve]

Have Nate double check his work. It wouldn't be the first time he made a mistake.
I'm surprise Bruce hasn't told you to pressyre test your intake. A boost leak is one way for your car to run rich and max out your IDC's due to high airflow counts.

Sure the MAFT has calibration issues but this sounds way off.

Steve

 

[oldman]

Boost Leak Test!!!

 

[jrpmp69]

Why was my post removed? The MAF Translator does the same thing that the AFC does, It alters the airflow signal that is fed to the ECU. If the computer is already compensating for 650cc injectors, wouldnt setting the MAFT to 450cc injectors alter the airflow signal going to the AFC?

 

[oldman]

Why was my post removed? The MAF Translator does the same thing that the AFC does, It alters the airflow signal that is fed to the ECU. If the computer is already compensating for 650cc injectors, wouldnt setting the MAFT to 450cc injectors alter the airflow signal going to the AFC?

Think about it, if the above statement hold true, how will anyone be able run a eprom/afc combo when running the stock MAFs? If you were to set the maft to 650s in this case, you will end up compensating twice.

 

[jrpmp69]

Think about it, if the above statement hold true, how will anyone be able run a eprom/afc combo when running the stock MAFs? If you were to set the maft to 650s in this case, you will end up compensating twice.

The stock MAF does not alter anything, the MAFT does. The chipped ECU is running the 650's and if they were stock, hense less airflow correction needed by the AFC.

 

[oldman]

The stock MAF does not alter anything, the MAFT does.

Exactly the point. According to your logic, one must alter the MAFT signal to reflect 650 before outputing to the SAFC, how would you go about doing that with a non-adjustable stock MAF?

The chipped ECU is running the 650's and if they were stock, hense less airflow correction made by the AFC.

I think you're confused because SAFC and MAFT uses difference adjustment interface although they both do exactly the same thing. Let's pretend that instead of eprom/safc/maft combo, we have eprom/safc/safc, which is the same exact thing. Since setting the maft to 650s is approximately -33% on the SAFC, would you then suggest setting the first SAFC to -33% as if you would a MAFT? Or would you set it to 0 as if setting the MAFT to 450s? OP really doesn't need a SAFC in his setup because the MAFTdoes the same thing like you mentioned.

 

[force it in]

The stock MAF does not alter anything, the MAFT does. The chipped ECU is running the 650's and if they were stock, hense less airflow correction needed by the AFC.

I have my MAFT set for 440's with my Keydiver chip. My injectors are PTE 680's. Less than 3 counts of knock with 91 octane, water/meth injection, Evo3 16G @24psi. My fuel trims are all close to 100%

 

[Quasimondo]

With the chip installed, there shouldn't be any adjustments on either the SAFC or the translator. SAFC settings should be set back to 0% for both hi and lo throttle. The MAFT should be set to 450's with no correction on the idle mid and wot knobs.

Even though the chip is set for 650's it will function best with the safc and translator set for no corrections. At this point the ecu knows it's running with 650cc injectors and there is no need to alter the airflow readings from either the translator or the safc to make the ecu think otherwise.

 

[force it in]

I kept my SAFC so that I can do some fine tuning. My low settings are 0 across the board. I added about 3% between 3 and 4k. Around 4.6k -7k I subtracted about 3-4%. I don't have a wideband. I just tune for knock on the logger.

 

[steve]

With the chip installed, there shouldn't be any adjustments on either the SAFC or the translator. SAFC settings should be set back to 0% for both hi and lo throttle. The MAFT should be set to 450's with no correction on the idle mid and wot knobs.

Even though the chip is set for 650's it will function best with the safc and translator set for no corrections. At this point the ecu knows it's running with 650cc injectors and there is no need to alter the airflow readings from either the translator or the safc to make the ecu think otherwise.

Exactly. Once we correct for the injectors in the ECU we don't want to continue lying about the airflow like would without the chip. One problem is that the MAFT isn't really good at behaving like a normal MAF so even when it's set for the default 450cc injectors there is tuning required to calibrate what it outputs.

Steve