hi, seeing as tech topics seem to be taking off recently!
i have a couple of questions

on higher power/boost engines

1: Whats the advantages/disadvantages of 8 injectors, instead of 4 higher flowing injectors?

2: What are the pros and cons of mounting 8 injectors RS500 style
as opposed to siamese type mounting? (i have read a tuner guide say they would not use RS500 style mounting for a few reasons, but never gave any!)

IS The Rs500 style better for higher revving cars as there are 4 injectors further away?

just been wondering today! as i kinda been thinking about tech subjects on here!
thanks!

 

id rather 4 larger injectors TBH (less chance of things failing and running lean on a cyllinder)

only possible reason i can think of with 8 inj plenums is spray distribution eg motune etc.

But i stand to be corrected

maybe back in the day there were no big enough injectors or management/mapping problems for them ?


EDIT miss read what you said but seeing as i mentioned spray pattern you might be correct with power delivery difference between the two

 

The main reason that 8 injector setups existed in the first place was all down to induction stroke timebase and injector flow required versus the resolution needed at idle.

Basically older injectors arent as quick to respond (open and shut) as modern injectors.

Now at high rpm you dont have long to get the fuel into the cylinder, so you need a BIG injector, but then this means when it will only open and shut at a certain speed you end up over fuelling it at idle and low rpm, cause the injector has a imnimum fuel delivery per operation thats simply too high.


To get round this, you use 2 banks of injectors, and 1 bank only operates at higher rpm, that way you can still use small injectors in the first bank and maintain a good idle.

Read the "803" topic on here for a lot more info on this

https://passionford.com/forum/viewtopic.php?t=157305

 

im a massive fan of 8 injectors )rs500 style)

the reason for the 8 injectors as in the rs500 manifold is

there is an injector mounted further up the inlet track,, this helps the fuel to gather heat from the air on the ralative long journey too the combustion chamber, this heat helps atomise the fuel more! the smaller the atomised size of the fuel, the better it burns (and better emissions )
so why not just have four injectors and mount them like the secondary injectors on the rs500 manifold? well at low engine speeds the inlet air wouldnt have enough energy too carry the fuel too combustion chamber and the fuel would "drop out" of suspension

the primary injector are then used for low air speeds (revs) and high air speeds,,, but the secondary injectors are only used when airspeeds are high enough too carry the fuel so the injectors dont have too be as massive as one set of injectors as there is only a short amount of time too get all the fuel in!

 

Ohhhhh


how does this compare to siamese WRC configuration then ??

 

Gareth, i agree 101% on massive power N/A motors, but do you really reckon that its an advantage on a turbo motor where the charge is so hot anyway?

Its not something ive got any data to support one way or the other, but it seems like its going to be less useful on a turbo, especially when you are fully on boost and not managing to burn all the fuel anyway because you are running so rich to use the fuel as a det surpressant?
(or am i missing the point and it allows it to work BETTER as a det surpressant for the same reason?)

 

could you switch? say 803s til it was really going,then switch to a set of 1000cc injectors (for example) to take advantage of both systems?ie the low down with small injectors,the high end with injectors further away,and the reliability of only having one injector firing so if it cuts itll just stop fuelling,NOT underfuel?

 

when looking at the wrc inlet,, you gotta think what it was designed for, massive torque at low engine speeds (they cannot make massive torque high because of the restrictor)
so you dont want a secondary injector mounted far away from the inlet as engine speeds are lower,, so you need the injectors closer

 

is that in english?8 injectors,4 small 4 big,one set for low rpm etc,then they turn off and large ones take over

 

chip-3door

i was going too say that the advantages are very very very small,, but some people engine builders still use a staged 8 injectors, mostly in the rallycross world! so i guess they might of tried it and it works

big_wig_074
no problem at all with the right ecu

 

More typically they keep going and 4 more join in, but potentially you can do either

 

like the rs500 yeah,but have heard of one out of a set of two failing then BOOM! so wondered if u could do one then another?quality. im learning,slowly!

 

everyone always goes on about injectors failing,,, its a rare condition but is a risk! its a risk anytime we play with out cars!
you could minimise his risk by having your injectors cleaned and checked,, but sadly there still is a risk

 

sounds like a valid reason to swap to the other.

But in reality any ECU that can do that can probably also monitor if an injector isnt firing anyway TBH

 

does this mean the atmoisation theory of the 500 set up is not applicable here then what with both the injectors in the same place ?

 

yes mate

 

thanks guys!