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The setup is a 347 with a 85mm turbo and 139lb injectors. We are have a hard time starting with initial start up. once the car starts it surge from 1500-3500rpm. The fuel pressure has been turned up to 60psi injector opening time is setting at 1.7 and the duty cycle is also at 60% just to make it idle. Help!
 

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That's a really high injector opening time. My understanding is, the higher the dead time in relation to the pulswidth, the harder a time you'll have tuning it. If it's getting enough air to rev to 3500rpm, and seems to want the fuel to match, then maybe check for vacuum leaks first and foremost? Sometimes you get into a wierd spot in the fuel tables with vacuum leaks, as the kPa and RPM don't fall under normal operating conditions, leading to really wierd surging (unless you're running alpha-N and/or some TPSdot setup). I had a similar issue (vacuum leak putting me in odd parts of the VE table) on my junk when I first started it on EFI and E85.
 

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Thanks for the info. I will go over everything checking for leaks. I also fail to mention compression somewhere around 10:8 on this setup. Could this be a factor? Or do I need to run a much bigger injector to run E85 for my combo??
 

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I can't help you with injector sizing (I'm obviously at much lower HP than you), but I'd check your MAP at idle and go from there.

Could a sticking wastegate do something like this? Do you run an idle air controller? That could also be a leak, as some of the Ford 2-wire systems require manifold vacuum to pull them closed, and then the motor pulls them back open against the draw to balance the flow. I don't think those would work at all in a FI situation...
 

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what efi system are you running? what do you cranking fuel tables and after start tables look like? I have 160lb injectors with 43 base fuel pressure and it idles pretty good. I only get a surge if im too lean or too rich at idle and the o2 sensor is trying to correct the af.
 

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You have something way wrong mine has 225 atomizers and a belt pump at 75 base and mine will idle fine at 2.6% dc 800rpm


Mark
 

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The norm is that you will add roughly 45% fuel min when converting from gas to E85. I second looking for a vacuum leak on the idle problem also what timing do you have at idle?
 

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The setup is a 347 with a 85mm turbo and 139lb injectors. We are have a hard time starting with initial start up. once the car starts it surge from 1500-3500rpm. The fuel pressure has been turned up to 60psi injector opening time is setting at 1.7 and the duty cycle is also at 60% just to make it idle. Help!
What engine management system are you running?
 

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Discussion Starter #10
The timing is set to 30 degrees at idle. Also the injector is at 60% duty cycle just to run at idle.
 
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