Injector questions

[barryogen]

It's come time for me to chose a few things about fueling etc for my project...

And I'm trying to get some info on injectors.

Big ones(800cc) appear to have issues at idle, and smaller ones(550cc) may not be suitable for my end goal of ~450WHP*.

So, how tricky is having a second set of injectors? The rotary guys appear to do it ok, as do a few of the higher end Evos.

My rational is that I could have the factory 330cc injectors sitting there handling idle, and have a set of 550cc ones that kick in when boost is causing a need for more fuel.

Engine management is being decided at the moment, and it looks that the scale of ECU I'm going for handles 8 injectors just fine.

I'm open to all sides of whatever arguements people are willing to present.



*I realise my current project doesn't scope to that point, but just bear with me.

[Burning Angel]

A Link plus G3 will run full sequential staged injection on your engine.

The problem you get with large injectors is that they cant open for a short enough time to deliver the small amount of fuel needed at idle.

With the staged injection the extra injectors will start deliviring fuel at a certain Load/Boost point.

The hardest part will be getting a custom fuel rail and injector bosses fabricated into your current intake manifold. Also tuning is a little more difficult.

[barryogen]

thats what I thought...

I'm using this rough guide for fueling...

550ccm of fuel per 100HP maxed out
650-680ccm of fuel per 100HP with room for safety

Which, leaves me with 731.25cc per cylinder.
Stock are 300-330 depending on model, meaning a 440cc should do, but I'd rather have extra fuel than not enough.


I've found some guys in the states running dual fuel rails on Celicas, for drags, so they are able to be purchased... albeit from yankys. :lol:

[barryogen]

From what I have read the 2zz-ge also has a crazy low BSFC(high .30s), meaning that it gives much HP for unit of fuel than a heap of cars... but my head is still trying to figure out BSFC

[IH8TEC]

with big injectors, it's all in the tuning, guys in the states run 1000cc injectors and have no trouble gettign them to idle, get a decent computer, and run bigger injectors if you want, i will be going to sard 800's in the future and expect to have no problem with them on my piddly 1600cc motor.

i'm changing my 550's (flowed 576cc each) because i have them pretty much maxed on 25psi at 92% duty cycle. and a higher base pressure up to 52psi.

if your thing is anything to go by i guess i'm making alot more that 196kw atw

[Lith]

If that stuff is anything to go by, using both Barry's and another way I use to estimate such things I'd imagine you'd be running ~220-230kw @ wheels area on the dynos I am used to (ie, Speedtech in Welly) which is pretty good going.

With the Skylines, we tend to estimate an injector size based on 1cc = 1hp - yay for having 6 cylinders to simplify the calcs. I run 555cc in mine.

[IH8TEC]

not bad for a really rich tune, i've mentioned to jeremy i'll organise to put it on speedtech's dyno next time i'm down those ways.

[~SlideWays~]

not bad for a really rich tune, i've mentioned to jeremy i'll organise to put it on speedtech's dyno next time i'm down those ways.

That'd be real interesting to see the difference in readings! Good man

[barryogen]

Just found this...

Originally Posted by monkeywrench
Our 550whp red GTS still has the stock rail on it with no distribution or flow problems.

Very interesting. People are always saying how much better distribution a center feed has, but I don't know if anybody has actually tested this.

My goal is under 550WHP, so I guess I just buy a big set of injectors and see how it goes.

The celica GTS he's talking about was 666WHP before they switched to an Auto

[Lith]

not bad for a really rich tune, i've mentioned to jeremy i'll organise to put it on speedtech's dyno next time i'm down those ways.

It'd be interesting to see, I have been trying mine on various dynos to try and get an idea of how things compare and to dispel or justify various beliefs.

I had the car tuned on Speedtech's hub dyno and made 271rwkw with peak power reached at 14.2psi - then ran it with NOTHING changed and ran it on a DynoTorque rolling road dyno at the Toyspeed MM dyno day and made 251rwkw. After that I fiddled with my wastegate setup and got it holding 1bar more steady, peak power being reached at ~1bar and had another run on the same rolling road dyno and made 262rwkw.

A few weeks later I went down to a dyno day at Chequered Flag's new hub dyno in Welly and ran it with the new boost setup and ran 280rwkw there (peak power now at a full 1bar) which I reckon is relatively consistant with the gain I made on the rolling road dyno, if applied to Speedtechs dyno.

The strange thing is looseunit's Starlet GT ran at both the Toyspeed dyno day on the Dynotorque dyno and then at the dyno day at Chequered Flag and made 156kw on the rolling road dyno, and 153kw on Chequered Flag's dyno - though there are theories involving wheelspin floating around to explain why the Starlet made similar power on both whereas I lost 20kw. I'm going to have a go on STHitec sometime when I am up in Auckland to see how it goes there.

[RedMist]

with big injectors, it's all in the tuning, guys in the states run 1000cc injectors and have no trouble gettign them to idle, get a decent computer, and run bigger injectors if you want, i will be going to sard 800's in the future and expect to have no problem with them on my piddly 1600cc motor.

Its not quite true. Tuning can certainly make a difference, however sometimes you simply cant trigger the injector and snap it closed before you flood the cylinder. Very short injector duty cycles are difficult to control.
There are a tonne of online injector size calculators. If I were you I would run the injector as hard as you can, ie as small as you can get the injectors for a realistic horsepower to expect. If you work the injectors hard you get better atomisation and consequently more HP.

Also be very hard on yourself, 450whp isnt easy but is expensive. Have a look at your proposed modifications and attempt to find someone with a similar setup. Query them about their peak HP and possibly what injectors they run.
My 3SGTE should, with any luck, run around 280whp. Thats for around a 10k investment. Hence I'm not altering my injectors, just had them cleaned and flowed. Its just a pity its strangled by the rally intake restrictor.

[IH8TEC]

so is 92% duty cycle bad? and would leaning my car out more from 10.5's to 12:1 afrs save the injector much to be worth it?

i know people in the states and one in particular in aussie that ran 550s in his 4agte and 30psi boost and got 267kw atw in a cortina. just seems weird i'm maxing mine and only at 196kw i know dyno differences, but thats ALOT of difference lol.

[RedMist]

http://www.witchhunter.com/injectorcalc1.php4

It would appear that 800cc/m injectors are about right (if not slightly light). I compared the results with what was achieved on my 4age and its pretty accurate.

[RedMist]

so is 92% duty cycle bad?

You're certainly pushing it. Injectors fuse (generally open) when the overheat. At that duty cycle, for a prolonged period of time, I would bet on some injector damage.
Are you running a Link? Its purely speculative, however I think certain Links miss calculate the duty cycle. The reason for the speculation is becuase I know of an offroading collegue who runs his injectors at 100% (I kid you not!) and hasn't had an injector fail. And he's WOT for a greater period of time than you are!

[IH8TEC]

yeah link g3. is there an accurate way to find out? or not really.

[QikStarlie]

lean it out man 10.5! sheesh you'l find the injector dc% will drop alot once you take some fuel out.
a certen 4agte i played with was pinned on 99% (max old link plus will show) on 15psi boost. afr was in the low 10's from memory. after leaning it out to 11.8ish then winding boost up to 18psi. the dc had still droped down to around 90%. has 550s? with stock fpr

my car only runs 450cc's with a rising rate reg. at 12:1 afr it hardly makes it to 80%dc makes 3kw mor than the 4agte above. shame

[IH8TEC]

yeah, base pressure of 52psi, it's 10.5 between about 19psi all the way to 25psi from around 5500-8000rpm.

might get it leaned out some time early new year and see how that goes. either that or just put the bigger injectors in and get it re-tuned,

but mid range and cruising is awesome and really fuel economical.

[QikStarlie]

yeh, you should gain a bit of power as well. 8000rpm and 10.5:1 will be using alot of duty cycle. probably find it'l drop down to 80ish witch would be all good. i wouldnt stress about 92% tho. unless your trying to land speed it at 25psi and 8000rpm. as it would hardly stay at 92% very long

[barryogen]

Also be very hard on yourself, 450whp isnt easy but is expensive. Have a look at your proposed modifications and attempt to find someone with a similar setup. Query them about their peak HP and possibly what injectors they run.

I just had a look at the link you provided, and from feeding in what I know of my engine, and fudging the numbers a bit depending on drive train losses, I put in the following.

550
4
.45
80

and got an answer of 812... 850s was what I was probably going with anyway, so I have some head room in there.

aside...
The BSFC appears to change considerably on a boosted engine...
The guys on the celica forum were working it out as .36-.38 on an NA 2zz, and .45-.48 on a boosted one... although that still makes it a very efficient HP producer.

The guys doing this in the states got past the 450 mark about 2 years ago, and details on their setups is pretty hard to find, but I'm mostly copying the lotus supercharger setup, and will probably head to a turbo later on once the boost bug bytes properly... although I'm thinking of just skipping straight to it as it looks like an easier route.

[ChaosAD]

The evo's have a solenoid on the vacum hose to the fpr.
How about doing something like that to reduce the fuel pressure at idle