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The mkiv Supra Owners Club

Fuelling Questions


Mark Ayling

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I'm having 550cc injectors and a UK fuel pump fitted next week, so I'm going to need my AFC set up correctly - Justin's going to put some basic settings in but I understand I need to get to a rolling road to have it done properly?

 

Firstly, does anyone know of a good rolling road, location, price, and whether they can sort the AFC?

 

Also, I did contact Tuning Japanese who reckon they can do it, but they guy said this:

 

One question I have is what are you using to control the injectors? Simply fitting them alone does not necessarily mean you will have more fuel, under certain conditions, as the ECU will not understand that they are there.

 

Now I don't completely understand all this fuelling business, but I thought that the AFC controls the fuelling (to an extent) so I won't necessarily need a new ECU just yet?

 

Any advice/comments appreciated!

 

Cheers,

 

Mark.

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The ECU controls the firing of the injectors, not the dosage of fuel - that's controlled by the size of the injectors alone.

 

Going from 440 to 550cc injectors means you'll be overfuelling by 25% in theory. The ECU can try to correct this overfuelling in closed loop mode (a steady state throttle input) by detecting the air/fuel mix using the oxygen sensor (lambda sensor) in the exhaust system.

 

If these are UK Supra 550cc injectors, you'll need a resistor pack installing as well - I assume this has been taken into account?

 

I got my AFC set up by Chris Wilson, who had the car for a couple of days to do it. He used the real road :)

 

The AFC controls the fuelling by telling the ECU what it needs to hear in order to fuel correctly. Simplistically, if you now overfuel by 25% the AFC needs to tell the ECU that there is 25% less air coming in so it delivers 25% less fuel... But it's not as simple as that, it does need proper tuning.

 

-Ian

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Thanks, I'm beginning to understand it now - so am I right in thinking that assuming I have the AFC set up correctly I'll be alright for the moment, but an ECU would be a good move in the near future?

 

What is a "resistor pack"? :conf: I'm not sure what I've got to be honest, all I know is I bought a set of 550cc injectors!

 

:stupid:

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I've just looked at the stuff I've got in my garage - is the resistor pack a cylindrical shaped object with a sort of plastic thing coming from it which feels like its got springs in it? Or is that the fuel pump?

 

...can you tell that I'm not very knowledgable on these things...? :conf:

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Guest Terry S

Mark, who ever sets the fuelling up with the SAFC will need a decent AFR meter like a Motec PLM. I know Leon uses one & so does Chris Wilson. You would be shocked how some of the supposedly reputable firms try to do this without these. Always ask the question. With a Motec it should be set to 0.8 & with a conventional AFR you should be looking for aboy 11:5:1. I am sure if CW is reading this he'll confirm or correct.

 

Good Luck

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0.8 /11.5 while under full throttle acceleration, that is. Light cruising should give 1.0 and I think 14.7

 

I can't emphasise correct fuelling enough :)

 

I've given JB the pictures and writeup of my injector upgrade, so that may be appearing at some point on this site. If you want that info now, go to

Injector Upgrade (7.3mb)

 

The piccies are numbered and the text file relates to them.

 

The resistor pack has to be wired into the engine loom, a scary task (to me!). Who's doing the work?

 

-Ian

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Guest Terry S

I might be wrong but I don't think Justin has a PLM or similar, so you will need to take the car elsewhere to get the fuelling correct.

 

Justin was able to get hold of the resistor packs a while back.

 

Ian, you are right about the 0.8 or 11.5 being at WOT. These work out a percentage of 14.7 or 1 which is what the car should run a CLC.

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I don't know what the consequences of attempting to run the engine with the 550cc injectors in but no resistor pack are. I am assuming it will cheerfully fail to run in the slightest, but I don't know if anything could be damaged (the injectors or some sort of fuse blowouts).

 

I got mine brand new from Jay Marks Toyota but that's international shipping and won't be in time for wednesday :) Toyota probably sell them but I doubt very much they have one in stock anywhere other than Japan, as it's another never-goes-wrong item. A used unit may be your best bet, if JF can find one.

 

He may have one ready anyway, as he's doing the install for you and knows what is required?

 

-Ian

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