injectors

[JustenGT8]

Yup, what Stew said. I would have thought going to smaller injectors is exactly what you need to do....as long as they can handle your peak fuel requirements then you have better control and better atomisation...generally things that will deliver better torque.

Valve event injector timing is bogus in my poorly trained opinion...i can't se how you can get the timing events to work and account for mixture travel time etc etc thru and portion of rpm band to make it worth the trouble.

Now with direct injection, yes i can see that level of control being a big plus.

As for how i would run the staged injectors....i would have thought (depending on what delivers the torque and hp gains) that lower rpm you are using the inboard injectors until a point where you slow the rate of duty increase for them and begin to phase in the outboard set. If the inboard set have headroom (you'd never run them over 85% if you didn't have to) then at the point of standoff you would up the duty of the inboard set as these aren't effected (or are they?) to provide that little extra kick infuel you are looking for?

[Celica RA45]

i also tune 1st with lid off 1st to see and thought it was ok but after last race air box lid is getting wet again
ram tube is 10mm ring around a 50mm hole

[JustenGT8]

BTW your standoff is it just a harmonic that's catching the fuel but not slowing actual air flow right..a bit like a standing wave in a river for example?

In simple terms you have a wall stopping the fuel....a bigger hose just means a wetter wall, still won't get past it. I can't see how a bigger injector will help?

[Celica RA45]

the idea was with the 2 stage ,was to make the car more drivable down low .with 50 quads coming into corners it would just die but bring 2 stage into (i havnt increased the runner length either )it would pick up and drive out of corners because the out boards are 200mm further out than the inboards ,hope this makes sense and tried 7mgte injectors 1st in and out but it caused more stand off so went to single pintle injection

[Celica RA45]

but remember with 45lbs and 720cc stand off was from 7000 up wards going up to 80lbs on the fuel reg stand off is now from 8300 up wards

[JustenGT8]

Yeah that cause you have more pressure i would imagine so you are breaking down the wall so to speak...it's overcome the standoff which appears to be getting stronger thru that part of the rev range. Up pressure to 100psi and you'll find it's probably improved again...at some point the fuel pressure rise will give your injectors a hernia but i can't say what psi will start to give you probs....you're already at a higher fuel pressure than i have ever used

Maybe switch to piezo injectors has then handle high fuel pressure much better don't they?

[Celica RA45]

and inlet cam doesnt retard untill 8400 and it moves back 8 degress
exhaust advances from 2000 to to 3200 by half and stays there to rev cut

[Celica RA45]

and have tried cam posi all over as well

[oldcorollas]

move the outboard injectors in further.. so then even with the lower fuel pressure, you will get through "the wall" easier, or at least get more fuel in further...

hmm, have you seen spray pattern of the injectors? even with single pintle they could have a fair bit of spread. afaik you can get specific injectors with a smaller spray cone, ie designed for outboard applications

then again, check otu this renault F1 motor vid..
http://www.motorator.com/videos/299
they have standoff under WOT, and they wet the trumpets on closed throttle (can see the liquid)
of course they aren't ejecting the fuel past the standoff, and the standoff fuel is sucked in when going off full throttle... but still they have standoff.... but much higher pressure resonance stuff too

[ed]

your standoff is it just a harmonic that's catching the fuel but not slowing actual air flow right..a bit like a standing wave in a river for example?

In simple terms you have a wall stopping the fuel....a bigger hose just means a wetter wall, still won't get past it. I can't see how a bigger injector will help?

this man is smart

you cant move an aerosolised fluid through a region of non moving (or rather a resonating/standing wave) column of air when it uses the air as a vector to get into the valve throat. MAYBE with a theoretically/incredibly brief injection pulse as the valve opens as the column accelerates in one direction you might get a small gain, but i really dont know. and that time period is massively small, and i doubt running an injector that big would be sensible for a 'maybe'

whats been said about perhaps the momentum of the fuel of of the injector with the higher pressure being capable of 'delivering' the fuel down the port without the airflow is correct, it sounds sensible.

either way, you need to sort/minimise the resonant/standing wave if you want to get fuel down the port from outside the bellmouth... thats where the port injection comes in handy! also explains why standoff is so shit with carbs

edit, actually. just thinking....

are you getting true 'reversion' as in a specific rpm the fuel comes back up OUT of the runners above the level of the injectors or are you just getting a cloud of stagnant fuel around the bellmouth over a broad rpm band? (ie stewy, im not confident that video is actually true fuel reversion, just stand off of fuel in a harmonic cloud, which is entirely normal)

if its true reversion as in fuel goes into the comb chamber then gets spat back out up the port, im not sure where to start.... maybe just a bad point where intake and exhaust harmonics favour fuel/air going backwards... and no inj timing is going to fix that

and! another thing to consider with standoff is the bellmouth design. the way a tapering bellmouth generates its harmonic wave is different, and as such the standing wave at the lip is different, making different fuel cloud patterns:



again though, standoff is normal. full reversion in a limited rpm range with fuel 6" above the bellmouth is bad. which do you have?

[Celica RA45]

i have the no 3 ram tube pic but i do have ram tubes like in no 1 pic
the fuel mist is blowing out ,but it is less since i put up the fuel pressure to 80lbs ,but i have 3 different inlets with different lengths each are 75mm then 70mm and last 63mm so might try that so i can use the 30mm 1s to see if it stops it
but i got 6 new sard 1000 cc for 1090 to my door so im happy to try moore things

thinking again the fuel sits right out flush to the rim of the ram tube till about 8300 then it starts to come out after that and can feel the pulses hitting me in the face after about 8700 rpm

[jeffro ra28]

I know it seems the focus of this conversation is on Injectors size.

But, through my experience with piss and dribble alcohol sprint car type engines. A BIG variable for fuel clouds hanging above the ram tube was exhaust header type and injector placement. I realise its a completely different setup, we were running port inectors (spraying directly ontop of valve) and injectors placed just below the bell mouth of the ram tube. The fuel clouds actually hovered above the ram tube bell mouth. On the Dyno, the engine wouldnt hold constant RPM and would hunt in the rev range. The two major things that effected the severity of the standoff was choice of headers and the ram tube injector placement.

An identical engine with a gutted carby as its throttle body instead of ITB's didnt have any evident standoff and made more power. My theory for it working better was because the air speed at the carby throat (smaller then totall area for all ITB) was much higher then at the throttle body on the ITB's, basically eliminating this "wall" or perhaps harmonic effect. The reduction in overall throttle area didnt seem to reduce power, perhaps because each cylinder draws it charge at seperate times.

Sorry for all that jargon that probly doesnt interest you the slightest. But in saying that, can you still be sure injector size is the problem here?

Maybe placement of injector, manifolding, and exhaust?

The standoff is a result of reversion right? Why not try and reduce the reversion to start with?

Im really only self tought in this area and dont have a great deal of technical knowledge or theory on my side only what i have experienced myself, so please excuse me

[ed]

thinking again the fuel sits right out flush to the rim of the ram tube till about 8300

^^ thats normal

then it starts to come out after that and can feel the pulses hitting me in the face after about 8700 rpm

^^ thats bad

i call the first thing 'stand off' and is just some aerosolised fuel sitting in a resonant acoustic standing wave

the second thing i call 'reversion' where the whole intake flow is being pulsed back up the intake port by some whacky interference with intake/exhaust/cam timing effect.

maybe my use of the terms is loose, but i think of them as 2 different entites. the latter is mainly a length/exhaust/cam timing thing, and i doubt inj timing would change much there

[Celica RA45]

at the moment i will go with your idea edd and use no 1 ram tube and reduce the inlet track the same as i have now with the short ram tube and retune to see if this helps ,when i get car back from the panel beaters .if this works good .if it doesnt just try the 1000 to see as i can sell them very easy as i got 6 ,so to a sky line that make heaps of grunt

ps thanks