Does anyone have any knowledge of what injector placement does to power production on a Zetec? The standard injectors are right against the head but most installs I have seen using aftermarket throbble botties have the squirters mounted in the TBs themselves, a good ways back from the head. I'm only askin as I'm fitting bike Tbs which have injector runners built into them and was going to use them, until I saw a piccie of a metal Zetec inlet manifold (mines placcy) and the injectors were mounted in a sandwich plate between the manifold and head. My idea now is to get said plate and make myself a short adaptor manifold up to mount the TBs on. Do I really need to or not?

Injectors are against the head in production engines for efficiency and emissions. As I understand it, there is no real need to do it for a performance engine.

when injecting on the ports...you get driveability...

but an less good mixture..

when you do TBS injection you get a better mixture..c.q. more BHP. but you play with the problem that your fuel / air mix.. won't enter the chamber totally..

(longer distance) think it has to do with lower rpm ranges..

Tks

As with everything on an internal combustion engine, there is no "ideal" position, as the engine is always in a transient state.

In basic terms, the higher the airspeed, the further from the valve the injector needs to be.

At low revs aiming it at the back of the inlet valve is no bad thing. At high revs injecting into the trumpets is probably nearer ideal. Somewhere in between will be a good compromise.

Not something to worry about too much, but err on nearer to the head rather than nearer the trumpets.

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Originally posted by tks
when injecting on the ports...you get driveability...

but an less good mixture..

when you do TBS injection you get a better mixture..c.q. more BHP. but you play with the problem that your fuel / air mix.. won't enter the chamber totally..

(longer distance) think it has to do with lower rpm ranges..

Tks

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in fact you just need that!

the only problem is gonna be....

that you will need an smooth change between both banks...and that will need allot of MCU skills. many MCU's aren prepared for that...

Altough it will depends on wich way you want to implement things....but i guess you wanted to do it like the balance button on you stereo..switch from one side to another smooth....

if you don't do it smooth i'm sure that the engine will come in an loop on certain rpm/pedal changes..

(it will fall back and rise and fall back) on certain rpm's....

i think that if you connect both banks always...you will get the worst of 2 worlds, because none of the 2 banks you fully optimise!

and offcourse the injection time will need to be very very low.....

Tks

Could you not just have 8 injectors four at the head, four at the trumpet each doing half the work?

would be the worst of 2 world..


none of the banks will do what it is placed for!

untherstand??
the best is an balance system...
that at 3000rpm the TBS injectors start with just 10% pulsing..

and at 6000rpm the balance it 100% on the TBS injectors..

that would be ideal..

Regards,

Tks

That must be possible to bodge up somehow, with a bit of reasearch into the standard electrics you could make something that runs off the rev counter signal to fade over the pulsing. Maybe. Im in over my head to be fair!!

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Originally posted by tks
in fact you just need that!

the only problem is gonna be....

that you will need an smooth change between both banks...and that will need allot of MCU skills. many MCU's aren prepared for that...

Altough it will depends on wich way you want to implement things....but i guess you wanted to do it like the balance button on you stereo..switch from one side to another smooth....

if you don't do it smooth i'm sure that the engine will come in an loop on certain rpm/pedal changes..

(it will fall back and rise and fall back) on certain rpm's....

i think that if you connect both banks always...you will get the worst of 2 worlds, because none of the 2 banks you fully optimise!

and offcourse the injection time will need to be very very low.....

Tks

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I've seen a couple of high end vauxhall xe engines with 8 injector setups. as nsdev says, its for high rpm. the installs i've seen have been 250+bhp and 8000+rpm.
from a ppc article i recall the benefit is seen from about 6500rpm upwards which is usually the red line for a production roadcar so hence they're near the heads for emissions purposes.

i think i have a picture somewhere of an example, if i find it i'll post it up.

Ned.

edit: found it:
http://www.locostbuilders.co.uk/upload/Im001311.jpg

[Edited on 17/1/06 by ned]

Big advantage is twin injectors give a better fuel mist over more of the rev range than one big one.

I'm sure there's an add-on for megasquirt that phases the 2nd bank of injectors in.

I don't think switching on both banks on half duty would work, would they not disrupt each others airflow.

Would the air already be "heavy" with fuel from the 1st set when it reaches the 2nd set and not mix properly.

Cossie RS500s had 2 sets of injectors fitted as standard, but only 1 was wired up as standard. To release the full potentional of the engine, you needed to get the second set wired up.

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Originally posted by MkIndy7
I'm sure there's an add-on for megasquirt that phases the 2nd bank of injectors in.

I don't think switching on both banks on half duty would work, would they not disrupt each others airflow.

Would the air already be "heavy" with fuel from the 1st set when it reaches the 2nd set and not mix properly.

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While we're on this subject, I just thought I'd let you guys know that the details of my 'work in progress' conversion of a zetec to bike TBs is all detailed HERE

Hope that it might be of use to some of you, I've tried to summarise a lot of the stuff I've learnt including TB & injector sizes etc etc.

Cheers,

Neil

Edit to say that I'm soon to be changing my web hosting company, so if the above link stops working in the next few days just access the info via www.mymojo.co.uk .......

[Edited on 18/1/06 by nre]

[Edited on 31/1/06 by nre]

On the software issue..when programming the double banks of injectors, it has been found that the way to get a smooth transition is to tell the system to turn on BOTH banks for X number of cycles, then turn off the other. Otherwise, the engine can develop a random 'miss', or give a brief cough.

The reason for double (and even triple) banks of injectors is to smooth out the torque curve, and lift it up the rev range.

Syd.

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Originally posted by nre
While we're on this subject, I just thought I'd let you guys know that the details of my 'work in progress' conversion of a zetec to bike TBs is all detailed HERE

Hope that it might be of use to some of you, I've tried to summarise a lot of the stuff I've learnt including TB & injector sizes etc etc.

Cheers,

Neil

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[Lookin' pretty flippin' good Neil! This is exactly the same setup I want to use so it's nice to have someone to take the pratfalls for me before I do it
Do you happen to know the ID of the rubber joints on the intake stubs of the ST170 manifold perchance? That looks like a good idea from where I stand simplicity-wise. The OE intake fannymould I got was a plastic one so I was intending to cut the runners off it and fab up an adaptor to go between this and the TBs but I'm now thinking ditch the sandwich plate altogether and just make a manifold to bolt straight to the head. Final question, I don't suppose you know the flowrate of the standard Mundano injectors do you?

[Edited on 18/1/06 by Browser]

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