Injector firing

totta crolla
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Injector firing

Postby totta crolla » Fri Mar 15, 2024 2:44 am

Does anyone know how often the stock ecu fires the injectors?
Ideally in engine degrees (over 720°) or distributor teeth.
My distributor has 24 ne teeth at 30° and 4 cam? teeth at
180°

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Re: Injector firing

Postby davew7 » Fri Mar 15, 2024 3:30 am

The big port injection system is very primitive, when compared to current systems. The injectors are fired in pairs for two cylinders at a time! I do not believe there is any way to alter the injection timing with a stock ECU. One cylinder is always going to be to early, or to late relative to valve opening.

totta crolla
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Re: Injector firing

Postby totta crolla » Fri Mar 15, 2024 3:44 am

Sorry l should have said, l'm using a programmable ecu with the stock loom so l'm just trying to replicate what the stock ecu does.
l have no desire to go sequential.

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jondee86
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Re: Injector firing

Postby jondee86 » Fri Mar 15, 2024 4:41 pm

Image

Seems that despite what the 4AGE manual says, both of these strategies
may have been used with TVIS engines. AFAIK JDM and UK models only had
a single ignition transistor, but USDM may have got two outputs, a 4-tooth
reset trigger wheel and grouped injection.

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
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totta crolla
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Re: Injector firing

Postby totta crolla » Mon Mar 18, 2024 1:32 am

What a great 'find' that diagram is for me!
Takes a little thought to get your head around the timings but it is invaluable, thank you.
I will check again but I'm fairly sure my loom is set to inject all four at once (we have already had this conversation..) but my engine from the factory has the four point re-set distributor and this l think is my issue,
the aftermarket ecu wants to inject every 180° (from the four point distributor) this creates an obvious fueling issue and it also means that the ecu sees double the actual engine RPM
The ecu has lots of "tooth" strategies and now l'm armed with the info from the diagram l can look closer at those.
Thanks once again.

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jondee86
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Re: Injector firing

Postby jondee86 » Tue Mar 19, 2024 12:57 am

When referring to the above diagram, be aware that it shows the injectors being fired twice
per 720 degrees. According to Jeremy Ross below 6000 rpm the MR2 ECU (assumed to be the
same as the Corolla TVIS) injects half the calculated fuel every revolution. Above 6000 rpm it
changes to injecting 100% of the calculated fuel every second revolution. Your aftermarket ECU
will likely only allow one injection cycle per 720 deg so you can pretty much choose to inject
at any point in the cycle... it will still run OK.

If your ECU wants to inject every 360 deg you could halve the injector open time. That may
create a problem with injector duty cycle at high engine rpm, as the injectors will be operating
at effectively twice your engine speed !!!! Have fun :D

Cheers... jondee86

PS: Engine rpm is normally read off the Ne 24-tooth wheel.
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

totta crolla
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Re: Injector firing

Postby totta crolla » Tue Mar 19, 2024 1:53 am

Indeed l am desperate not to halve the injector pulse for the reason you mention.
Probably over the summer l will try to adapt a proper crank trigger wheel to my power steering pulley as this seems to be the best way forward.
I know there a a few companies that make a RWD P/S crank trigger pulley but they are really expensive!
To digress a little...
The problem with the rpm readout seems to be with the ecu and interestingly if l run the engine with CoP sequential ignition (from a 24-1 smallport distributor) l have no rpm problems.
I think it is because l can dedicate a specific crank tooth to a specific ignition trigger rather than having a single output to fire four times over 720°

It is though, in the end just as you say..
All good fun!
As always thanks for the help and the chat.

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Re: Injector firing

Postby allencr » Thu Mar 21, 2024 7:08 pm

totta crolla wrote:What a great 'find' that diagram is for me!
Takes a little thought to get your head around the timings but it is invaluable, thank you.

Where's it from??
Thanks jondee86, can count on you to always deliver such great diagrams & pics, besides all them words!

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jondee86
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Re: Injector firing

Postby jondee86 » Thu Mar 21, 2024 11:53 pm

allencr wrote:Where's it from??

Extracted from Page 15 of EFI #3 - FUEL DELIVERY AND INJECTION CONTROL article
published by Toyota Motor Sales USA. One of many articles that were once available
online from a site named Toyota Autoshop 101. It disappeared quite a few years ago :(

BTW Phil Bradshaw is alive and kicking and still busy restoring classic Toyotas. He lives
not far from me and I went to see the AE86 he has built up from a rusty shell. I sold him
a TVIS engine to put it it and a lot of bits and pieces I had over from my Corolla days !!

Cheers... jondee86
The reasonable man adapts himself to the world; the unreasonable one
persists in trying to adapt the world to himself. Therefore, all progress
depends on the unreasonable man.

totta crolla
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Re: Injector firing

Postby totta crolla » Fri Mar 22, 2024 5:57 am

allencr wrote:
totta crolla wrote:What a great 'find' that diagram is for me!
Takes a little thought to get your head around the timings but it is invaluable, thank you.

Where's it from??
Thanks jondee86, can count on you to always deliver such great diagrams & pics, besides all them words!

All of the 'regulars' on here are fantastic but Jondee?
He/she/it in my opinion is the fantatasticest :lol:

allencr
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Re: Injector firing

Postby allencr » Sat Mar 23, 2024 3:03 pm

My apologies to Mr Bradshaw who is in no way extinct, only his website which continues to live at web.archive, an invaluable resource & treasure.

Also, EFI #3
http://www.autoshop101.com/forms/h22.pdf