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Discussion Starter · #1 ·
Actually it's a bit more complicated than that....

The engine, 4G64 NA, I'l spare the details on the mod's, they're extensive. The relevant issue is since a complete rebuild, and putting in 880 CC injectors, If I floor it, engine sputters and coughs, If I let up to about half throttle it will run and accelerate nicely and will let me roll the throttle up to about 3/4 and then start the coughing and sputtering again.

I'm oscillating between the timing being too advanced and crappy stock fuel pump. maybe a little of both. I'm compensating for the bigger injectors with a SAFCII, the E-prom is for 450CC injectors, so the fuel is dialed back, also the plugs are showing lean
 

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LSR Mike said:
Actually it's a bit more complicated than that....

The engine, 4G64 NA, I'l spare the details on the mod's, they're extensive. The relevant issue is since a complete rebuild, and putting in 880 CC injectors, If I floor it, engine sputters and coughs, If I let up to about half throttle it will run and accelerate nicely and will let me roll the throttle up to about 3/4 and then start the coughing and sputtering again.

I'm oscillating between the timing being too advanced and crappy stock fuel pump. maybe a little of both. I'm compensating for the bigger injectors with a SAFCII, the E-prom is for 450CC injectors, so the fuel is dialed back, also the plugs are showing lean
You cant compensate enough with a safc for the 880cc injectors. You are running rich with no boost and lean during due to the fact you still have the stock fuel pump.
 

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Discussion Starter · #4 ·
Well, Its a normally aspirated engine, so it isn't rich with no boost. I am leaning toward the stock fuel pump being "inadequate" . any comment about the SAFCII affect on timing? I'm dialed back to -25%
 

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Discussion Starter · #6 ·
ECU is a Stock e-prom unit. The prom is a custom job from Tom Dorris at DSMLink.
I ordered a Walbro 255 yesterday.

I have a AEM 30-1300 unit sitting on my desk at the moment.

I have to make my truck look like an Eclipse for it to work.
But thats going to be another thread.....
 

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Injector size is totally irrelivent to the stock pump, if you aren't making any more power than what the stock pump can handle than you don't need a bigger pump to run the larger injectors, they will be running real low duty cycles.
 

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Discussion Starter · #8 ·
I am making more power, I'm aware of BSFC. Since I'm outputting more than twice the Horspower of stock (116HP), and not knowing the numbers of the stock fuel pump, I thought it a prudent upgrade. What bothered me was the lean condition on the plugs, and the total lack of function at WOT. The stock setup is 275CC injectors, on that setup I had to add 35-40% more fuel via the SAFCII ,went to 450's was still in the +7-10 range,and now I'm at 880 in anticipation of a Turbocharger. Yes I ran NA to check out the build. I was at -25% up to -10 % with the 880's. I was expecting a really rich condition, and to come up lean made me think fuel delivery and or timing. Timing more the problem at WOT. but not sure....Oh well what's another $100 into a race car...
 
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