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The mkiv Supra Owners Club

Injector sizing


adi2009

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I m going to be doing a turbo project with the spare 2JZGE engine I got. I will be running a PT61 turbo, walbro, Emanage Ultimate, TT headgasket etc. I have currently ordered for a set of Precision 650cc injectors but I was just thinking if it would be better to go for 780cc instead just incase I run high boost in the future. Would it be adviseable to run 780cc for the PT61??? would idle and low rpm driving be fine??? any advice would be great.

 

Cheers

 

adi

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I agree, you'll be on the limit of airflow adjustment and be pulling duty as well, although it's still do-able, it's not elegant. But 650's are fine for a T61 unless you go mad and run north of say 1.6bar of boost. The considerations of an NA engine running high boost have to come into it as well - you've got a high compression engine there, it's not going to like high boost...

 

-Ian

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Thanks Ian and Martin. One last question, on the EMU's injector setting, once you input the injector size difference (from 330cc to 650cc) does the I/J map automatically adjust the flow of the 650's to what the 330cc would flow at any given rpm??? For ex. if the setting at say 3000 rpm and 5psi boost are ''0'' then would the EMU make the injector flow what the 330's would have been flowing at that rpm by reducing duty cycle???

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Thanks Ian and Martin. One last question, on the EMU's injector setting, once you input the injector size difference (from 330cc to 650cc) does the I/J map automatically adjust the flow of the 650's to what the 330cc would flow at any given rpm??? For ex. if the setting at say 3000 rpm and 5psi boost are ''0'' then would the EMU make the injector flow what the 330's would have been flowing at that rpm by reducing duty cycle???

 

Nope, that's not how it works. It works out a %age, in this case 330/650 = 51%, and takes 49% off the airflow signal. Do not confuse a %age reduction in airflow signal as exactly the same %age reduction in fuelling :) The stock ECU then spits out a duty cycle based on this airflow signal, but halving the airflow doesn't mean halving the fuel - not exactly. I mean, yes, it's going to reduce the fuel delivered, but may only be by 40% or whatever.

 

I have always maintained that this global adjustment is a nasty way of doing things. This reduction isn't logged in the datalogs. It also means you have to start putting positive values into the airflow adjustment if you want to fine tune things and that's unintuitive too. Plus the %age values you put in act on the remaining 51%, so +10% would be 56%, not 61% :blink: See what I mean?

 

Also, mapping an NA is an interesting balance between airflow adjustment and duty cycle adjustment. Y'see, if you halve the fuelling using the airflow signal, by the time you are on boost your stock ECU is still only delivering half the duty cycle it would be. The most you can increase this by is 100%, which takes you back to 100% duty cycle. So this works in your case with 650's, but not with 780's as you'd be taking out 58% duty to make it run off-boost. This means that on boost you could run 42% duty +100% of that which = 82%. 82% of 780cc = 640cc so you end up with a slightly smaller fuel system :blink:

 

Great fun this isn't it :)

 

That's where the Blue E-Manage fell over with NA's, but with the Ultimate you can pull just enough airflow so that when the stock MAP sensor runs out of range, the stock ECU sees a low enough amount to not log a fault, and then pull duty cycle using the injector map. That can go down to -80%, which is more than enough.

 

There is more than one way to skin this particular cat, no one way is right, you just have to put some brain into it to make sure you don't set a trap for yourself later in the process.

 

-Ian

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Ooh I can check that. I messed about a bit at the weekend and checked out that self-populating table, that's great. And I fiddled briefly with injector lag and reaffirmed my view that it's best zero'd and left alone when it almost stalled the car ;) So that's something else to look at.

 

-Ian

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Nope, that's not how it works. It works out a %age, in this case 330/650 = 51%, and takes 49% off the airflow signal. Do not confuse a %age reduction in airflow signal as exactly the same %age reduction in fuelling :) The stock ECU then spits out a duty cycle based on this airflow signal, but halving the airflow doesn't mean halving the fuel - not exactly. I mean, yes, it's going to reduce the fuel delivered, but may only be by 40% or whatever.

 

I have always maintained that this global adjustment is a nasty way of doing things. This reduction isn't logged in the datalogs. It also means you have to start putting positive values into the airflow adjustment if you want to fine tune things and that's unintuitive too. Plus the %age values you put in act on the remaining 51%, so +10% would be 56%, not 61% :blink: See what I mean?

 

Also, mapping an NA is an interesting balance between airflow adjustment and duty cycle adjustment. Y'see, if you halve the fuelling using the airflow signal, by the time you are on boost your stock ECU is still only delivering half the duty cycle it would be. The most you can increase this by is 100%, which takes you back to 100% duty cycle. So this works in your case with 650's, but not with 780's as you'd be taking out 58% duty to make it run off-boost. This means that on boost you could run 42% duty +100% of that which = 82%. 82% of 780cc = 640cc so you end up with a slightly smaller fuel system :blink:

 

Great fun this isn't it :)

 

That's where the Blue E-Manage fell over with NA's, but with the Ultimate you can pull just enough airflow so that when the stock MAP sensor runs out of range, the stock ECU sees a low enough amount to not log a fault, and then pull duty cycle using the injector map. That can go down to -80%, which is more than enough.

 

There is more than one way to skin this particular cat, no one way is right, you just have to put some brain into it to make sure you don't set a trap for yourself later in the process.

 

-Ian

 

Ian, so suppose I dont want to be messing with the airflow map (as I m planning to use the airflow output to eliminate the stock map sensor) Can I not use the Global injector adjustment and just work off the I/J map???. Very interesting stuff, really looking forward to learning about it but need to get my head around the basics first!

 

I think on the Ultimate it uses the injector adjustment when you use the injector size feature, not the airflow adjustment like the blue used to.

 

I am using the Ultimate, so is this what it does then?

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the NA is not Digital Ignition and there for cannot pull timing in the sense mentioned here. But the NA is able to retard the main coil somewhat based on its knock map.

 

IF I was doing an NA-T of this size, Id be converting it to the TT digital Ignition for sure!

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Okay, here is an idea, shoot me down if it is wrong, but see if you can follow me with this....

 

Being dizzy based, it will generate a spark for a main coil pack, is this coil pack controllable, and if it is, would it be possible to route a single ignition lead to the entire coilpack, I do realize this means you have only a single control for the entire bank of 6, however there shouldn't be any reason to advance/retard on a cylinder basis.

 

Since the NA ecu is able to advance/retard slightly, it might be worth while hooking into that in order to open that avenue of tuning.

 

Plausable?

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It can indeed do it, implementation...well... don't know

 

Channel Change Feature - Vehicles with a distributor type ignition system may able to use group fire or individual ignition systems (Replacement parts and modifications to the wire harness is required)Also, Group injection systems may be changed to sequential injection (Modifications to the wire harness is required).

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HI

 

I'm going single early spring next year, but was thinking of upgrading my injectors to 650cc with a Apexi power fc now, would the Apexi be able to trim the 650cc injectors down for my bpu sup until i go single, the single i'm thinking of is a t61 or t67.

 

cheers jayson

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HI

 

I'm going single early spring next year, but was thinking of upgrading my injectors to 650cc with a Apexi power fc now, would the Apexi be able to trim the 650cc injectors down for my bpu sup until i go single, the single i'm thinking of is a t61 or t67.

 

cheers jayson

 

The power fc is complete standalone, so it doesn't trim as such, it controls from scratch.

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It can indeed do it, implementation...well... don't know

 

I think in order for the EMU to be able to convert the ignition from distributor to coil on plug (if at all it can), you would need a crank position sensor and camshaft position sensor installed on the car and I believe the NA does not have the crank position sensor and I m not sure if it has a cam position sensor.

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Can we pl stay on the topic pl. Its something extremely useful thats being discussed on the emanage and would be useful for anyone for future reference too.

 

*awaits for further input from Ian C* :search:

 

Mmm, well, my experience of E-manage tuning on NA's is precisely zero so I can't really input any more on this!

 

Theoretically it can control the single coil to the dizzy. How the hell this works in practice I don't know, I'm not sure how timing advance and retard is controlled in the NA...

 

-Ian

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