back on injectors

Post by **smorison** » Wed May 26, 2004 10:44 pm

Ok,
i'm back on this subject cause its pissing me off no end....i found a simple formula which will help here:

HP = cc per minute / 5

so and if i can remember back to highschool maths stock engine assumptions:

200hp = x / 5
200hp*5 = x
x= 1000
1000 / 6 (6 injectors) = 166.67cc

now whats got me concerned here is that this would mean the injectors are on a 100% duty cycle at what... i've found some anecdotal information that the MIVEC has 175cc injectors which work out at:

175cc = 315hp (about 220kw at the flywheel at 100% d/c)

the problem is that if we are running 175cc injectors they are already pretty busy so there isn't a huge amount that can be done to force more air into the car without putting on an extra injector or increasing the size of all 6.

thoughts?

TimmyD · Post by **TimmyD** » Thu May 27, 2004 12:03 am

soooo how do we increase the size of the injectors?

Post by **Supplanter** » Thu May 27, 2004 12:11 am

Replace them with bigger ones

TimmyD · Post by **TimmyD** » Thu May 27, 2004 12:17 am

Supplanter wrote:Replace them with bigger ones

LMAO nice one

sooo how do we increase the size? or how do we get bigger ones??
*no way is that intended to sounds dirty!*

wildfaye · Post by **wildfaye** » Thu May 27, 2004 1:04 am

before i say anything else...wats what??

So u r trying to say that increasing the capacity of the injectors will not reap better power alone rite? will onli be wasting petrol rite?
unless we have a corresponding increase in airflow to mix with it rite?

i'm not really techically minded...so bear with me okie

GPXXX · Post by **GPXXX** » Thu May 27, 2004 10:07 am

just a slight digression here Steve, but on the Zoom article re Angela's turbo conversion (EXC) it was noted that they managed to squeeze about 120kw-ish at the wheels from the std injectors at 97% duty cycle or something close to that mark... (GPX tip)

so i'm assuming our cars are running on about 75-85%-ish duty cycle (since i'm already netting about 105-106kw at the wheels without turbo - and please no dyno debate!

)

i have also been advised that adding an additional injector is only a bandaid solution, although they do have its benefits it also has the potential to result in uneven fuel distribution amongst the cylinders that may lead to premature wear (mechanic's words, not mine), which is why most ppl replace their stock injectors with larger items...

btw, what means 'Way Off Topic'

(my bad, that was a pathetic joke...)

*runs and hides*

MADFTO · Post by **MADFTO** » Thu May 27, 2004 12:54 pm

what = Wide Open Throttle

Larger injectors will allow more fuel to be put it, but you if you can remap the computer, they won't waste as much fuel.

Duty cycles are preset when you are running on open loop.

Eh, my definition of a duty cycle though isn't concrete as no one has ever told me.

I suspect is the percentage of time of the induction stroke that the injector is open =) but if anyone would like to confirm or clarify this, it'd be appriecated.

salacious · Post by **salacious** » Thu May 27, 2004 1:26 pm

The turbo kit that was developed by RPW uses 275cc injectors. I think these are standard Mitsubishi injectors but I ain't sure what car they are on. I did find that the 2.4l Galant and Eclipse Spyder GS (4G64) which are non turbo'd use this size of injector but I'm not sure if it is the correct one.

Brian

Post by **smorison** » Thu May 27, 2004 3:17 pm

duty cycle = % of time that the injector is pumping in fuel...

MADFTO · Post by **MADFTO** » Thu May 27, 2004 4:19 pm

Duty cycle defination clarification.

Percentage of what time though???

Is it the percentage of time over a full combustion cycle (two engine revolvutions), full engine revolution.
Or just over the induction stroke (1/2 rev)

I'm leaning towards the last as you can't really pump fuel during the other three strokes (ie, 100% duty cycle would be impossible if the base time was not just the induction stroke)

Sorry if this sounds inane, but I just can't seem to get the concept right in my head =)

Post by **smorison** » Thu May 27, 2004 4:30 pm

good question

i would assume (not knowing this 100%) that duty cycle is drawn from the induction cycle of the engine.

i.e.
Intake Cam's open
Sucks in fuel
sucks in air
Intake Cam's Close

ruchi · Post by **ruchi** » Thu May 27, 2004 4:57 pm

Before you scratch your head too much trying to figure it all out, you might want to re-evaluate those formulae.

This is my opinion, as I couldn't be stuffed doing any research on this topic, as I really don't think it is an issue unless you have done some serious engine and breathing mods, but it would seem to me that this forumla is not accurate and as such you might be chasing your tail.

The issue is two-fold, different octane fuels can release different amounts of energy / power when ignited and different engines / mappings / tunning setups can produce different power levels, even though the volume of fuel was to remain the same.

me thinks that this formula was probably arrived at by someone over simplifying the maths. What you'd want to find out is for what circumstances this formula is true - i.e. what octane levels, maybe even temperature, air / fuel ratio etc. At a guess I would suggest these calculations are probably based on 92RON fuel.

MADFTO · Post by **MADFTO** » Thu May 27, 2004 5:18 pm

Ruchi has a point =)

However, I was just trying to clear up my own knowledge at the same time, hence the minor deviation =)

One day, I'm going to tune for myself. Unfortunely, no one can know your car better than yourself after a long period of time. =)

Post by **smorison** » Thu May 27, 2004 6:05 pm

Umm this topic is changing, the formula is based on average fuel i would imagine so it would be a 92ron rated fuel.

Flow rates of Injectors are a different subject to how much fuel is requried to hit the correct AF ratio, Larger injectors may be required to hit the AFR, so may a Larger fuel pump, and a FPR. However this is a different from what i'm trying to work out...

high ron rated fuel means you can advance the timing of the engine... a higher ron rating simply means that the fuel ignites later, as a by product it creates more power... there isn't "more power" built into the fuel... the higher the octane the more you can advance the timing on the car without the risk of detonation.

at the same time, engine ECU's that read octane rating and adjust the car's timing accordingly can only automatically do this upto the ron rating they are tuned to (i.e. normally 98 ron), with a aftermarket EMS unit you can teach it to alter timing to xxx ron rating... whilst using higher rated fuel will give a more power for both of these the car that can advance it's timing further say on 110ron fuel will always be faster.

Miss_FTO · Post by **Miss_FTO** » Tue Jun 29, 2004 12:43 am

hey this is a little off the topic but i am due to get my back 3 spark plugs done as i am cumin up on 100,000 k's so it it worth replacing my injectors? factory or after market or should i just take them out and get them cleaned? or do nothing at all?? help! hehe

my car is running rough could this be the plugs alone? or do injectors make the car a little rough?

Luv your advice!

Post by **smorison** » Tue Jun 29, 2004 8:49 am

Inline injector cleans are pretty good (its a high pressure can attached to your fuel rail)... you can have them sonically cleaned if you want but that's just an extra expense....

Spark plugs are a definate change and get them to check your stepper motor that could be the problem.

Miss_FTO · Post by **Miss_FTO** » Wed Jun 30, 2004 12:15 am

stepper motor? what is that? is it a common problem?

i found out i coul dget 6 new injectors proper mitsi factory ones plus 6 platinum plus for about 330 which was sweet so i will get them from sydney by fri and get them installed

stay safe xox & cheers for replyin so quick

MarkFTO · Post by **MarkFTO** » Wed Jun 30, 2004 2:13 am

just had a very quick read so sorry if this has been mentioned before.

Don't forget injectors fuel delivery will also depend on base fuel line pressure. Upping this a little can squeeze out a little more fuel but put it too high and the injectors will not spray properly. Not a good way to get a bit more fuel though.

Forced induction on an fto IMHO needs larger injectors. Id rather not run a normal injector above 85-90% duty cycle.

//\\//\\ark

to4garret · Post by **to4garret** » Wed Jun 30, 2004 12:10 pm

FYI

the 275cc injectors come from the 6A12TT, i do happen to have a set of injectors lying round too

RallyMad · Post by **RallyMad** » Wed Jun 30, 2004 7:18 pm

Miss_FTO wrote:stepper motor? what is that? is it a common problem?

i found out i coul dget 6 new injectors proper mitsi factory ones plus 6 platinum plus for about 330 which was sweet so i will get them from sydney by fri and get them installed

stay safe xox & cheers for replyin so quick

I hope this is correct, please correct me if it isn't anybody. On a very basic level the stepper motor helps to regulate your cars idle and the inlet of air into the air flow meter. COngratulations on finding the good priced parts, but are you sure you need to replace the injectors? The plugs would definately be a good idea though I think.