Wiring semi sequential fuel injectors V8 to Haltech Sprint 500 with 4 inj output

sindre83

New Member
I'm in the process of creating a wiring harness for my 1uzfe swap into a AE86 drift car. The ecu I have purchased is the Haltech Sprint 500 since it is a cheap and by the specs a good option to power my simplified V8 with manual conversion.

However I found a problem. The Firing order of the V8 is: 1-8-4-3-6-5-7-2. So assuming the fuel inj order will be the same. The sprint 500 has only 4 inj outputs so it must run semi sequential fuel with wasted fuel. Now how do I pair up the injectors?

Having a look at the original wiring diagram from lextreme: http://www.lextreme.com/lexuecc2.pdf
You can se that the original lexus ecu also only has 4 outputs and is pairing injectors: 3+5 1+7 8+2 6+4.

But if I start googling how to connect up semi sequential fuel on V8 one of the top searches is: http://www.extraefi.co.uk/Drawings/PDF_Files/8cy_SemiSeq.pdf
It uses the same firing order V8, but the injectors are paired differently:
1+6 8+5 4+7 3+2

So now I am confused. Which one do I use? The extra EFI makes more sense when you consider the firing order.
 

sindre83

New Member
found another one

Now this guy obviously had the same problem in 2008: http://www.v-eight.com/tech_forum/viewtopic.php?f=8&t=676&st=0&sk=t&sd=a&view=print

Injector wiring sequence
http://www.v-eight.com/tech_forum/viewtopic.php?f=8&t=676 Page 1 of 1
Author: EFMotor [ Sun Jun 08, 2008 4:19 pm ]
Post subject: Injector wiring sequence
I'm doing the wiring of my new Motec Mls (m4) ecu, and I became aware of a issue when I was wiring the injectors. The ecu has 4 injector outputs, so that 2 injectors must share one output.

I had a look at how I wired this on my last ecu (microtech), and it was wired like this:
1-7, 8-2, 6-4, 3-5. This is also how it is wired stock.

But I could not see the logic in this. The way I see it the two injectors wired together should be the ones going oposite from eachother in the cycles. Like this: 1-6, 8-5, 4-7, 3-2. And both injectors would open once each crank revolution. (this is how I want to do it)

Or the other logic way of wiring is two mate the two injectors closest to eachother in the firing order like this: 1-8, 4-3, 6-5, 7-2. And then only open the injectors once on 720 degrees on the crank.

What do you guys think about this? Can someone please explain the sense in the stock wiring?

And he did not either get a propper correct answer that "this is the way to do it".

Anybody? common a lot of people have wired V8's with only 4 inj drive outputs.
 

gloverman

Well-Known Member
When I wire them I pair them like Toyota did. Toyota know a thing or two about making cars. I have only done about 20 like this but they have all worked well. Cheers
 

Cobber

New Member
It makes bugger all difference.

I have tried 3 ways.

Same as Toyota 3+5 1+7 8+2 6+4
Paired 360 degrees apart and fire the injectors twice per 720 1+6 8+5 4+7 3+2
Paired in firing order and fire the injector pairs once per 720 1+8 4+3 6+5 7+2

They are currently paired as per the last option and gives a slightly better afr at idle. This also makes the more logical sense to me.

I don't think the std injectors are accurate enough to be fired for such a small amount at idle twice per 720 degrees as per option 2.

Anything above idle there was no difference that could be noticed.
 

1uzvl

New Member
ive wired two different brands of v8 with aftermarket ecu's ive always used wired the first four to the last four, in this example it was 1+6, 8+5 etc

1 8 4 3
+ + + +
6 5 7 2
 

1uz747

New Member
When i wired up my Haltech E8, I asked Scott from Haltech to clarify due to the factory grouping. This was his response:

"To wire for semi-sequential injection you would normally wire in opposing cylinders. This means the cylinders that are at TDC together.
so in your case,
INJ1 - cylinder 1 and 6
INJ2 - cylinder 8 and 5
INJ3 - cylinder 4 and 7
INJ4 - cylinder 2 and 3"
 

Cobber

New Member
Once per 720 cycle will always see 4 cylinders getting injected at valve opening and 4 on closed valves (ignition point) all the time. Twice per 720 cycle will see this situation reversed and even out.

When you work out the injector duty cycle by rpm and load the valve open time v's the injector spray time starts to overlap so even the injector that was spraying in to an open valve now overlaps on to a closed valve.

The std lower manifold has longer runners so there will be little port scavenging going on. The more open supercharger manifold as in my case I suspect there was some port scavenging causing a slightly rougher and richer idle. I also feel the injectors were not accurate enough for such small opening times when injecting twice per 720.

As per my original post it makes bugger all difference above idle. In all cases the idle is still very smooth.
 

sindre83

New Member
Thanks for the replies guys. I agree it probably makes no difference at revs but still I want to make it right when it's first made from scratch. So I will follow Haltech-scott's advice as it makes most sence to me also.

But if anybody wants to explain toyota's logic then have a go :p

When i wired up my Haltech E8, I asked Scott from Haltech to clarify due to the factory grouping. This was his response:

"To wire for semi-sequential injection you would normally wire in opposing cylinders. This means the cylinders that are at TDC together.
so in your case,
INJ1 - cylinder 1 and 6
INJ2 - cylinder 8 and 5
INJ3 - cylinder 4 and 7
INJ4 - cylinder 2 and 3"
 

Cobber

New Member
I have a program that will do this, I downloaded it from the web but can't remember where from. It is a .exe file so I cant post it up here. Send me a pm and I can try to email it to you. Enter the cam spec, rpm and injector duty and it graphically shows when you are spraying on to the inlet valve.

Also some information on injector pairing here. Toyota inject in paired firing order for the 7M engine just prior to valve opening. See autoshop 101 link.

The 1uz has always been a mystery to me why they pair the way they do, the only reasoning I see is that it was easier to make the loom to pair on the same side of the engine.

http://www.autoshop101.com/forms/h22.pdf


http://www.toymods.org.au/forums/archive/index.php/t-56633.html
 
VERY ODD!!! makes no sense when you look at it charted out with intake valve open times... must be a cheaper to wire and makes no difference OR if you lose an injector channel in the ECU the engine will limp home better?
 
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