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Bigger throttle body? Smaller fuel pump? 

 

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 Post subject: Bigger throttle body? Smaller fuel pump?
Posted: Tue Apr 04, 2006 12:21 pm 
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Ok two things.

1) Can you just slap on a bigger throttle body? And if so would it make much of a difference to anything? And if so what throttle body should be used?

2) I've heard the e series falcons, particularly xrs are overfueled... is this true? Is it possible to just put in a smaller fuel pump (ie. falcon gli pump) and make it run a little leaner? Surely it would get a bit more power by increasing the air to fuel ratio... but would it run the risk of leaning out and f**k the engine?
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Posted: Tue Apr 04, 2006 1:07 pm 
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the fuel pump has nothing to do with "flooding" or overfueling the motor. Thats the job for the fuel regulator.

 

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Posted: Tue Apr 04, 2006 1:44 pm 
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plus the fuel pumps on the xr6/glis are all the same


aslo a bigger throttle body will make fuel econ go through the roof!

 

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Posted: Tue Apr 04, 2006 1:55 pm 
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As mylo correctly points out... an EFI fuel pump cannot deliver too much fuel really. It can, in the sense that too much is being sent to the engine and returned to the tank, potentially putting uneccisarily warm fuel in back in the tank...

Even a regulator cant really be blamed... EEC is resonsible for calcuating how much fuel to inject - and it does this assuming a certain fuel pressure. However, if, for some reason, the regulator is creating too much fuel pressure in the fuel rail, EEC will notice (through feedback from o2 sensors) that the engine is running too rich and will make the necessary adjustment to injector pulse width in order to return fuelling to the desired level (this is within reason).

The question of TB... is the I6 manifold suited to a larger throttle body? For example, the V8 manifold has an intake port (near the EGR/TB end of the manifold) which really defeats the purpose of putting a much larger TB on....

 

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Posted: Tue Apr 04, 2006 1:59 pm 
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It's the fuel pressure regulator that controls the amount of fuel in the fuel lines, the pump will constantly pump the same amount into the lines (provided there fuel in the tank for it to do so). Thee fuel pressure regulator is basically a valve that stops the pumped fuel in the lines from going back to the tank until a cerrtain pressure is reached (off the top of my head it is 300kpa in Tickfords, 275kpa in standards, but at idle [the regulators senses idle I presume through the vacum tube on the top of it and so adjusts the pressure accordinly] it is only 250kpa in Tickfords and 225kpa in standards). Basically if there is more fuel pressure in the fuel lines and fuel rail, then when the injectors open it shouldd allow more fuel into the engine than it would at lower pressures. as far as I understand injectors don't actually inject as more just open up and allow the fuel to flow through as it is already pressurasied! thhis is just my basic conception that i have picked up over thhe last yyear of reading on here and playing with the wagon - I'm not saying it's fully correct - and if not hopefully someone can correct me!

 

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Posted: Tue Apr 04, 2006 2:12 pm 
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lol, silly me, i meant regulator not fuel pump lol. i'm at work - not thinking straight
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Posted: Tue Apr 04, 2006 2:12 pm 
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4.9 EF Futura wrote:
Even a regulator cant really be blamed... EEC is resonsible for calcuating how much fuel to inject - and it does this assuming a certain fuel pressure. However, if, for some reason, the regulator is creating too much fuel pressure in the fuel rail, EEC will notice (through feedback from o2 sensors) that the engine is running too rich and will make the necessary adjustment to injector pulse width in order to return fuelling to the desired level (this is within reason).

Just to confirm, closed loop becomes a moot point at WOT, yes?
Also at WOT it will read solely off the maps, and forget any 'learned' behaviour?

 

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Posted: Tue Apr 04, 2006 2:22 pm 
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EEC observes the behaviour of the engine during closed loop and makes the necessary adjustments.

Constant adjustments are stored in the long term adjustment values (KARMF i believe the value is). If the long term adjustments are, for example, 5% too rich across the board - these values WILL be applied to open loop/WOT fuel trims.

This is consistent with EEC's strategy of learning over time as an engine degrades... would kinda defeat its purpose if these trims were not applied to WOT fuelling.

 

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Posted: Tue Apr 04, 2006 2:26 pm 
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Mmmm...
Might be hard to drive around constantly in open loop :lol:
Cheers Martin!

 

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Posted: Tue Apr 04, 2006 2:33 pm 
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i've a ported TB on mine - car seemed to have a bit more response to it - as for rwkw gains/loss - i've no idea! but i was happy enough with it!

 

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Posted: Tue Apr 04, 2006 2:35 pm 
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uglybob wrote:
i've a ported TB on mine - car seemed to have a bit more response to it - as for rwkw gains/loss - i've no idea! but i was happy enough with it!

You attack it with the die grinder yourself Frase?
I might get a die grinder and do some DIY porting of various bits and pieces at some stage...

 

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Posted: Tue Apr 04, 2006 2:41 pm 
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not schmee - got it off johno when he went twin TB's - its been ported out to 68mm - pretty sure it cost him ~$100 mark from a shop - i swapped it for a 6-pack & a stock TB i had around lol

 

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Posted: Tue Apr 04, 2006 3:00 pm 
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Bigger throttle bodies do SFA for performance (Yes Ive tried and done before/after dyno runs). If you compare the I6's throttle body to other engines you will see it is massive already.

And yeah, open loop maps do change based on closed loop trims, but not by a big amount so if you make a significant change to the fuel system (such as changing reg) chances are it will max out the trims and will change the WOT AFR's. It is hit and miss though, and I think you are better off just getting a chiptorque or similar to change the targets in the EEC.

 

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Posted: Tue Apr 04, 2006 3:03 pm 
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stockstandard wrote:
And yeah, open loop maps do change based on closed loop trims, but not by a big amount so if you make a significant change to the fuel system (such as changing reg) chances are it will max out the trims and will change the WOT AFR's.


Lol, i guess at this point EEC throws a fault code..... constantly running rich or constantly running lean...

 

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Posted: Tue Apr 04, 2006 3:28 pm 
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stockstandard wrote:
And yeah, open loop maps do change based on closed loop trims, but not by a big amount so if you make a significant change to the fuel system (such as changing reg) chances are it will max out the trims and will change the WOT AFR's. It is hit and miss though, and I think you are better off just getting a chiptorque or similar to change the targets in the EEC.

What I was getting at was, say, XR ECU with stock 275kpa reg...
Or vice versa, stock ECU with XR 300kpa reg.
Big enough to max out the EEC, and have a constantly lean or rich scenario?

 

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