cossie604

iTrader: (2)

Whats the advantages and/or disadvantages, if any, to using the older method for more fuel of having 8 injectors, either in the rs500 style or the later idea of the wrc lay out of a siamese pair per cylinder...as opposed to the more recent use of just one much larger and more modern injector design per cylinder?
In other words...have two greens or one 750cc per cylinder??
Stu.

Basky

suppose if you,ve allready got the 8 inj set up then you might aswell use them(rs 500) to keep the cost down


other wise use the new injectors and after market manifolds
just my opinion

Deleted by Request

...now people like stu/karl can map these i'd go 4 injectors over 8 for the simple reason if one injector failed in 8 youd be fucked ...i had 4 x 1000cc injectors on Level 8 ecu and passed an MOT ..enuff fuel for 700bhp


8 injector is real old hat thanks to proper new school mappers

bud-weis

the only single reason i can see for people using them is for those with RS500 plenum fitted...

i've never heard one GOOD reason to have 8 instead of just 4....

abdr500

iTrader: (1)

well I know there are many cars running 4 small injectors per cylinder for better fuel controller and you can get them to do what you like but 4 big ones will do the same thing only not as good as 2 per cylinder or 4 per cylinder

Nash

iTrader: (3)

Yes but wouldnt the same happen if one of the 4 injectors failed?

Andreas

With 4 injectors you would hopefully notice it running rough before something breaks. Atleast thats what happend when one of my standard injectors started to fail, it ran like a tractor.

Stavros

no, as it wouldnt run lean if it stopped working would it.

you cant be lean if there nothing all, lol.

itd just run on 3.

but if one of 8 failed, lean and pop.

Nash

iTrader: (3)

Oh right cool cheers bud, get what Phil was saying now.

boXXer

i know someone with a 450hp RS500, and to make things easier, he doesnt run 8 injectors. He uses 4x Siemens injectors instead as they are a more modern injector that can supply the fuel.

rapidcossie

i have had 4 1000cc injectors for about year and a half now and have no probs with emmissons and fuel economy is ok for the bhp.

Martin-Hadland

iTrader: (2)

So for safety 4 big injectors is best ..... BUT what about the use of 4 injectors with 2 fuel pumps?

Lloyd

how would 2 fuel pumps affect 4 large injectors ? as long as there is the right ammount of fuel at the right pressure.? or am i missing something?

GARETH T

i love 8 injectors,,, if done right you can gain very very slight bhp by having an injector further up the inlet track, can also can in BEFC

Martin-Hadland

iTrader: (2)

Why I have 8 injectors

Martin-Hadland

iTrader: (2)

Having 2 pumps means you could have one fail ....

Disabled Account

Lloyd, the problem is, qiute a few Cossies that used to run 8 green injectors with twin fuel rails/ fuel lines and twin pumps have now been converted to 4 large injector set up. Most of these cars have been fitted with a "Y" aeroquip fitting and a single link pipe to the new (single) fuel rail arangement.

In this situation if one pump fails completely, or suffers reduced flow - then IMO there is a fair chance of a piston melting - especially if on WOT.

Lloyd

it should still be ok if using twin 044.

GARETH T

tabetha

The primary reason for more injectors is because of fuel atomisation.
The effective atomisation will be different depending on where the injectors are positioned due to air speeds, latent heat control etc, for good emisions, low speed running they need to be as far from inlet as possible but for max power they (ideally) need to point straight down the throat into chamber.
It is not the injectors that have got better, it is the software that controls them in the main.
A cheap way to get a very effective 8 injector setup on a cos is to drill and boss the plenum cover, no stupid RS500 prices then!!
tabetha

RichardPON

BEFC?

GARETH T

brake effective fuel consumption

GARETH T

i say you got that the wrong way around

low speed needs to spray straight on the back of the inlet valve,

GARETH T

i made myself one a few years ago

Mike Rainbird

iTrader: (3)

All this bollocks about four injectors being more reliable is just that -BOLLOCKS. If a single fuel pump or injector failed on a high speed run, it would take the engine out just like an 8-injector one would (due to the sudden loss of fuel cooling at 850°C (ask Martin - he has had this happen). The ONLY time where there is a benefit is if you started the run with only one pump of the two running and didn't notice this. I have had this happen, and noticed it immediately - I could feel the car holding back the second it came on to big boost. It turned out a wire had come off one of the pumps .

Chip

iTrader: (3)

Not the whole truth at all, ask Doug Stirling for an exmaple of a car that was running 8 injectors and one of the injectors came unattached (clip was missing when the engine was built IIRC) which led to one cylinder running lean, but not enough for you to feel, so he was unaware and carried on with relatively spirited driving (was doing an A road fairly quickly but nothing like the load of a top speed run), if it had been a 4 injector setup on his car then I personally dont believe it would have died because:
The cooling effect you mention wouldnt be needed on the sort of driving he was doing to stop a piston melting once there was no fuel to burn and hence no heat (too lean = hot, almost no fuel = not hot)
He would have felt it straight away and backed off knowing something was wrong.

8 injectors is more than just twice the chance of a clip coming off, its also the fact you are many times more likely to not notice and carry on driving when it does happen (especially on part boost)

I agree with gareth and martin though to the potential performance benefits of injectors futher up the runners at high RPM though, very proven effective technology even on N/A cars

Mike Rainbird

iTrader: (3)

If a clip came off four, it would do the same thing. Obviously you would notice it if it came off at low speeds, but if it came off at high speed you would be just as fucked as if one did on eight injectors.

It's all about knowing your car inside out. I have had both scenarios happen on my own car (it was an injector wire that fractured on mine). I could feel something was wrong.

Garage19

Come on phil.... i thought injectors and their control would be your specialist subject?

Its not the "new school mappers" that have enabled you to use bigger injectors. A mapper can only do the best with what he is given and in the past the ecus had less resolution eg 0.1 m/s rather than 0.01 m/s so fine control over large injectors at low pulse widths was hard and closed loop operation next to impossible.

Injectors have probably got better with more reliable opening and closing times.

In short tecnological advances have allowed mappers to run big injectors and still meet emisions. Its not mappers suddenly being better at mapping.

Garage19

#


Chipidee doo da,

The eight injector thing does bring an increase in power if used/set up properly on a lot of N/A engines. Dave Walker did some good back to back dyno tests. Also just about every 1000cc twin super bike runs twin injectors for this reason. Ducati pioneered it in the WSB years ago as they found a power advantage.

Deleted by Request

....no denying the WRC siamese setup which i ran has a good spray pattern.....but if one fails slightly or fully your fucked...but on 4 if one failed no probs.....if one failed slightly whilst flat then yes again BANG.........but i like the odds for 4 rather than 8

If you ran 2 smaller pumps instead of one big un then you get the same problems..run 2 x 044's and i think most cars would be safe....Fuel pressure gauge in my car was my most valuable gauge after AFR moniter.

Martin-Hadland

iTrader: (2)

Injector clips should never come off!

Deleted by Request

.....quite correct unless not fitted properly!!!!

Chip

iTrader: (3)

Not at the same amount of load it wouldnt, it would neither melt not would it be so hard to notice, in fact if you want proof of that, have a word with si b and phil who drove all the way from germany to england with 1 injector disconnnected on a YB (they had to due to a cam issue) do you think you could safely do the same on an 8 injector setup at load sites where both injectors were mapped to fire? I honestly dont believe for 1 minute that you do, you are merely avoiding talking about the situations in which you know 8 injectors are potentially more likely to cause a problem for whatever reason you have for doing so (close links to a tuner who still favours them on road cars maybe?)

Well at least that is some admission of the potentially different effects, so we are getting somewhere slightly on that front at least!

There is a point at which that is the case, but it is NOT a point you are likely to be at very often on the road, you are talking about full boost and massive RPM, and for a sustained period before the failure, not something that is likely to be the case on a 500bhp road car (typical 8 injector power) due to the practical implications of using that much power for long on the road with regards to the speeds it results in.

I dont think it should be a requirement of engine reliability that you utterly know your car inside and out and back to front in terms of its exact response, failures like an injector plug coming off due to a missing clip for example often happen the first time the car is used in anger as its the time the engine first vibrates massively.
Obviously the correct answer is to not do something such as misplace a clip, but even the best tuners in the world can still make basic mechanical errors or be the victim of a mismanufactured clip that fails etc, so anything that increases the chance of the engine surviving in those circumstances is only a good thing surely?

Chip

iTrader: (3)

Of course they shouldnt, that goes without saying, but the fact still remains that they do so (esp if not fitted correctly or there is a component fault).

Martin-Hadland

iTrader: (2)

How can the fuel pressure guage be of any real help in the situation of high speed / boost and lack of fuel? You can't watch the guage or you will crash and unless it's linked to boost a warning lamp is useless...

Chip

iTrader: (3)

Not seen one so unsure if they are made but a simple alarm that referenced boost pressure to fuel pressure would be massively useful in that situation I guess, but I definately agree about trying to stare at the two gauges at once and then subtracting one from the other to ensure its within spec whilist doing 120mph round a left hand bend

It amazes me that more of this sort of equipment isnt available.
A good ECU should do the check for you too of course and limit boost accordingly.

GARETH T

the wrc inlet was built for midrange fuel supply,,, not top end like our unresitricted cars

Deleted by Request

Martin hence why i said after the AFR......idle pressure is important to me..lets me know everything is regulating nicely..AFR is the real indicator of everything.

...on time of the drivers crash he reported AFR and oil pressure were optimum

GARETH T

Martin-Hadland

iTrader: (2)

You mong, you could have a pump on its last legs (or have low voltage)and still make decent pressure at idle..