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Leiden

6cyl Injector Grouping

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Im sorry if this has been covered before

What is the correct way to group injectors for a 6 cylinder engine with a 153624 firing order running group injection.

I have done a bit of research on the topic and it seems to be either:

INJ1 to 135, INJ2 to 624 or

INJ1 to 123, INJ2 to 456

If a possible explanation as to why each one is correct is possible that would be great, on early Bosch systems in BMW they grouped the injectors 123 & 456, later Bosch systems with a TDC reference grouped them 153 & 624. From what I can understand the ecu can sync up either at TDC #1, or TDC #6 with only a crank trigger, this would mean injection events could be 360 out of phase between one start and another

Edited by Leiden O'Sullivan

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With multi-group fuel the two groups are fired in two out of phase groups. This means that the injection timing will not be ideal for all the cylinders. Normally we recommend wiring odd numbered cylinders (1, 3, 5) to odd numbered injection drives (1 and 3), and even numbered cylinders (2, 4, 6) to even numbered injection drives (2 and 4). 

So long as the total current draw of a group of 3 injectors does not exceed 5 amps you can use just the one injection drive instead of two.

When on multi-group injection mode, and the injection rate is set to '1/2 Engine cycle'  each group will inject every 360 degrees (out of phase). When on multi-group injection mode, and the injection rate is set to '1 Engine cycle'  each group will inject every 720 degrees (out of phase).

 

Edited by Scott

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Thanks Scott,

The injectors are about 13ohms each so the total current draw for 3 doesn't exceed 5amp. I currently have them grouped as 153, and 624 as you recommended but I'm having a little tip-in trouble that I initially thought was to do with the pairing, I took a log and a couple of screen shots of whats happening.

I'm having a bit of trouble understanding the TPS Delta, is this the ROC or 'Rate of change' referred to in the Acceleration enrichment section of the help file? The help doesnt seem to explain what it actually is, just mentions it here and there.

What I'm finding is sometimes the ecu will add acceleration enrichment at say 0.3% TPS Delta, but other times wont? In the first screenshot it shows the TPS Delta at 0.4% with no enrichment, the 2nd one shows enrichment with only a TPS Delta of 0.3%, Am I just confusing myself about the TPS Delta or could there be another issue?

 

 

 

Enrichment 1.png

Enrichment 2.png

RB30DET_Traditional.pclr

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Yes TPS delta is a measure of the rate of change.

All other conditions will also need to be met for the Accel to activate.

One important thing to remember is that accel tuning should be done after the main tune has been finished as it could mask issues with the main fuel table tune.

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Hi Simon,

I am pretty sure the main fuel table is quite close to the target afr's, this was done on a hub dyno holding various loads since I couldnt get into those zones easily via road tuning, the only way I was able to eliminate or rather minimise the hesitation was richening the low load and cruise areas up to about 13.0:1, there is still a lean spike when the enrichment fails to activate but it isn't noticable as a hesitation.

What are the other conditions that need to be met before enrichment activates? All I can think of is the Accel Load Correction table but this has 1.2 in the -60kpa zone and 0.9 in the -40kpa zone so if anything there should have been more enrichment when first coming on the throttle (-58kpa, 0.4 tps delta, 1.2 load correction) rather than later on (-44kpa, 0.3 tps delta, 0.9 load correction)

Could this be because of the Accel Deadband? I have it set at 0.5%, there is virtually no noise in the TPS signal so do you think I should try lowering it to maybe 0.2%. Most if not all other tunes I have seen have the deadband from about 0.5 up to 1%

 

Scott, would you be able to explain in a little more detail how exactly the fuel is injected in the 1 engine cycle multi-group mode, are the banks activated 360 degrees apart? So INJ1&3 -> 360deg -> INJ2&4 -> 360deg -> INJ1&3 -> 360deg -> INJ2&4 360deg, are these events timed in any way? I see the Injector Timing option still exists when in Multi-group mode, in my case its set to 390deg btdc, would that mean bank 1 activates when cylinder 1 is 390deg before tdc and bank 2 activates when cylinder 6 is 390deg before tdc or is this just ignored? I originally had the Link configured to run as a 3 cylinder 2 stroke which worked quite well until I upgraded the injectors and could no longer control the pulsewidths at idle, hence switching to group. Most people just tune and go but I try to understand how it all works :)

Edited by Leiden O'Sullivan

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Hi A bit of info below that could help in you situation.

Semi-Sequential Injection

Semi sequential fires injectors in groups of two.  It allows injection timing control and minimizes the time available for fuel to condense on the port walls.  This mode requires sufficient triggering to determine engine position in the 720 degree engine cycle.  In this mode, ideally injectors are wired in pairs according to the firing order with the pairs wired to the injector driver that corresponds to the lowest numbered cylinder in the pair.  However, with some firing orders this is not possible.  In cases where that rule is not possible the idea is to group injectors in such a way that the time for fuel to sit in the port is minimized.  Select Sequential Injection Mode when using this wiring configuration.  Note that unused injection drives will not be available for other use and will still be firing according to their position in the firing order.
    Examples:

  • 6 Cylinder, firing order 1 5 3 6 2 4.  Works nicely as per rule.  Fuel sits in port for 120 degrees longer on the higher numbered cylinder in the pair than the other.
    • Injector drive 1 is wired to injectors for cylinders 1 and 5.
    • Injector drive 2 is wired to injectors for cylinders 2 and 4.
    • Injector drive 3 is wired to injectors for cylinders 3 and 6.
  • 8 Cylinder, firing order 1 8 4 3 6 5 7 2.  Does not follow rule due to firing order.  Pairs as per OEM Toyota 1UZFE wiring.
    • Injector drive 1 is wired to injectors for cylinders 1 and 7.
    • Injector drive 2 is wired to injectors for cylinders 2 and 8.
    • Injector drive 3 is wired to injectors for cylinders 3 and 5.
    • Injector drive 4 is wired to injectors for cylinders 4 and 6.
  • 10 Cylinder firing order 1 10 9 4 3 6 5 8 7 2.  Follows rule but note that the order of the high and low cylinder in each pair changes.  eg in the 1-10 pair, cylinder 10 gets its fuel 72 degrees before deal.  In the 9-4 pair, cylinder 9 gets its fuel 72 degrees after ideal.
    • Injector drive 1 is wired to injectors for cylinders 1 and 10.
    • Injector drive 2 is wired to injectors for cylinders 2 and 7.
    • Injector drive 3 is wired to injectors for cylinders 3 and 6.
    • Injector drive 4 is wired to injectors for cylinders 4 and 9.
    • Injector drive 5 is wired to injectors for cylinders 5 and 8

 

Main condition is going to be the TPS dead band and the Accel clamp.

If you TPS is nice and stable / clean then a lower dead band will make it more responsive. Just avoid going too fine as it could then bring on accel when its unwanted.

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Thanks for the reply Simon, I dropped the threshold to 0.2% and things are working much nicer now!

I'll give the semi sequential option a go, in that mode does the ECU just run in sequential mode but ignores the 4, 5, and 6 cylinder squirts because the available outputs are lacking?

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Simon - If I can also ask - On a V8 with a Atom G4+ .  If I run semi sequential do I set up as a 4 cylinder in the ecu setting up or just input the v8 firing order ? And can I just run a toothed wheel off the crank and a crank sensor ( which one do you recommend ?)  to sync the injection timing ?

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You set up as per normal V8 entering the firing order as per normal. However you need a Sync pulse at CAM speed to know the position with in a 720 engine cycle.

With out a sync you don't know if the cylinder is on exhaust or compression stroke.

This mode requires sufficient triggering to determine engine position in the 720 degree engine cycle

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Hi - Could I run a crank angle sensor ( VR type )  with a 4 tooth trigger wheel on the crank for my distributor ignition on a v8 . And as a cam signal grind 7 teeth off the 8 point reluctor in the distributor and use that pickup as a 720 sync for the semi sequential injection timing ?

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You would probably be better off with more teeth on the crank wheel, somewhere between 12 and 36 works pretty well. 360 degrees needs to divide evenly by the number of teeth. For example 15 is ok, 16 is not. Leaving just 1 tooth on the distributor will work well for the 1x cam pulse sync.

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No you want all missing teeth in the one spot, and then combine that with a single tooth sync at CAM speed.

The Cam sync gives us a reference in a 720 engine cycle and then the cylinder timing is calculated from the teeth on the crank.

If you have a cam sync there is no need to have a gap in the crank pattern.

So a simple option is a 12 tooth crank wheel and a single tooth on the cam.

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