4 vs 8 injectors

Not sure if this qualifies:







Work in progress...

Could be done with a deeper domed filter really, to get the outer injectors further out of the bellmouth, and to give the option of longer trumpets...but I'll need to double check clearances before buying any more 'stuff'.

 

20vt rails employed i see

 

Ingenious and I like it.

 

Sure is Bill...1.8T injectors too.

Credit to F2Stu for the tips on getting the inner fuel rail to fit, and the making of the mounting plates.

 

I have plenty of pics of the build stages...mocking up and fitting the outer injectors etc...but that's probably better off in its own thread instead of cluttering up this one.

 

Very nice

 

Not slating it....but surly a bank of injectors in the way of the air flow kind of cancels out the need for the individual bodies in the first place and cause lots of strange air turbulance?

Id like to know more about this set up....it certainly looks the bizzo but I've seen too many cars produce great figures without another bank. What might we be possibly looking at extra here or are you not injecting petrol?

 

pug engines have responded well to outboard injectors as a 2nd set.. if i remember correctly did'nt dave walker get another 15-25bhp out of a mi16 motor doing this?

 

that sounds like a lot (a bit too much IMO) but will try and find the article

It all comes down to the engine 'needing' the charge - I reckon you need a pretty greedy engine to warrant the extra complication

 

Sorry to sound dumb but what is trying to be acheived? A second bank of injectors that turn on at a higher rev range? Why not fit larger injectors if the standard ones are maxed and re map? Or are you looking for a fine mist to be drawn in with the air? Any explanation would be good! I might no be able to see the wood for trees but I don't get it!

 

The theory suggests that you get longer for the fuel air mix to properly mix before entering the head...and less chance of the fuel spray hitting the back of the valves etc.
Injectors near the inlet valves give good drivabiulity where outboard injectors give better top-end power.

It probably doesn't need it...but since when do many of us do things because we 'need' to...rather than because we want to?

There is unlikely to be a restriction to air flow, based on the gains expected over a single ABF throttle plate...there is plenty of air flow round them.

As for set up, running large injectors can cause poor idle problems if running with a Cat etc (probably unlikely again, but who knows) so running smaller inners and larger outers, phasing onto outers when the engine comes 'on cam' again makes sense.

It may work...
It may not.
In which case I'll undue 4 cap screws, remove the outer injectors and change one trumpet - nothing ventured, nothing gained.

Reading the theory and other examples, it seems that around 5% is the sort of gain that can be expected, from better atomising and mixing of the fuel/air mix.
That seems to be about right for other examples I've seen/heard of.
So a possible 10 BHP, when combined with the relevant ignition timing changes.
I am sceptical...but who knows. We'll see.

The ECU will allow 4, or 8, so I can swap about...if it works, great...
If it doesn't...then everyone else will know not to waste their time trying.

There is plenty of info out there that shows outboard injectors work...if they didn't, pukka race engines wouldn't use them. Whether there will be a gain on a fairly mild 16v engine remains to be seen.
Only time will tell.

 

My understanding is that it's more a factor of efficiency, rather than need for more fuel.
Longer for the air/fuel mix to combine, giving a better - more efficient - burn...rather than a need for more fuel.

The theory/examples seem to suggest the gain is found with no other changes that outer injectors and ignition changes.
If nothing is changed hearware wise, and the ignition timing was optimised perviously for 4 injectors, then what else can give gains?
It has to be better - more complete - mixing of the air & fuel.

 

What I am getting at is that a lot of these things sound like they should work 'in theory', and on a F1 or supertourer engine they make a difference due to the increased mixing giving efficiency gains, but in reality on our relatively low-tune engines that are pretty inefficient anyhow, it makes little difference.

I have been advised not to bother on my engine/install by a chap who knows his onions. Concentrate on getting a good sized filter and plenty of clearance at the end of the trumpet he said.

But the kit cars pretty much all had them.

It will be interesting to see what data you get from your experiment though - it all adds to the pot.

 

injector pintle and spray pattern alone may be worth experimenting...

Motorsport systems dont run on the normal 3bar fpr's etc... they seem to run significantly higher, which maye be improved atomisation.. vis a vis the TSi motors have superb effeciency/power

I would hazard a guess these atomisation gains would yield power/torque and allow more optimal mapping.

just a thought.

 

could well be a senior moment memory wise.. on my part.
think it was in an old CCC of Walkers Workshop I saw it in.

 

Absolutely, got a few ideas along these lines myself - tests coming in the new year

 

On a related subject...
Any reason why a mix of FPRs can't be used on a common system?
Say 3 bar on the inners and 4 bar on the outers?

The FPRs should work just the same, regardless of the supplied pressure, assuming the pump is up to the job...so I can't see why not.

Higher pressure on the outers = more mist, less spray?

 

if it works or if it gains you very little, nice work anyway. Gotta love having a fiddle.

 

That's the spirit in which it was built...

Some said it couldn't be done...there wasn't room - especially under a domed filter.
It can...and there is.

Much of the accepted thinking suggested a staggered cam set-up with a bigger exhaust cam was what was required...but thats proven not to be the case on my engine...
Nothing ventured, nothing gained etc.

Whether it adds anything power or torquer wise has yet to be seen.

 

Folks, I asked Chris to move this as it was starting to dilute the ITB Porn thread...

Glen.