Multiple fuel injectors

[SomptingGuy]

Don't ask why I'm asking this, but...

Can anyone point me to an example of a port injected gasoline engine that uses more than one injector per port? These may be in series (i.e. one before the other) or both located the same distance from the intake valve.

- Steve

 

[ivymike]

Not exactly what you're after, but related:

http://www.sae.org/automag/techbriefs/12-2006/1-114-12-20.pdf

Lexus gives V6 dual injection
The latest and most powerful member of Toyota’s
GR-series V6 family, the 2GR-FSE, encompasses
the company’s leading-edge injection gasoline
engine technology. As fitted to the Lexus IS350
and other Toyota models, it employs two (port
and direct) injectors per cylinder with new “double
vertical fan-shaped spray” to achieve a homogeneous
and dense fuel mist.

custom bike setup

http://www.rbracing-rsr.com/zx11tubo.htm

RB Racing only builds sophisticated state of the art systems that feature: ... custom throttle bodies w/2 injectors per port;

Honda bike setup

http://www.superbikeplanet.com/2004/Sep/040909a.htm

Dual Stage Fuel Injection (DSFI) system features two injectors per cylinder.

 

[SomptingGuy]

Interesting, thanks.

The Toyota one sounds reassuringly expensive. I didn't think anyone would employ both systems on a single engine!

The Honda one sounds a bit like their solution to a driveability problem. I wonder if the FSAE crowd use these engines??

- Steve

 

[dgallup]

The original Corvette ZR1 used 2 injectors per cylinder as well as the Maclaren (SP?) F1 road car.

 

[Bribyk]

The FSAE crowd usually runs the 600RR's with only one injector per cylinder. Since your air flow is limited by the restrictor there's little to gain. The team's I've talked to had a heckuva time trying to tune it and get drivability with staged injectors while not being Honda.

 

[Cargeke]

Drag racers use multiple injectors per cylinder, but only when they need more fuel than a single injector per cylinder can supply while maintaining a precise fuel curve. Otherwise it's not worth the hassle of tuning the system.

 

[globi5]

The Mazda RX-8 has 3 injectors per rotor.

http://www.rx8club.com/showthread.php?t=150432

(But then again, it also has three intake ports per rotor).

 

[dgallup]

Cool, I forgot about the rotaries. My old RX-7 only had 2 per rotor even though it was a "6 port" engine.

 

[patprimmer]

Drag racers normally use multiple injectors when using alcohol or nitromethane fuel. I have never seen them on a drag race petrol engine that was not supercharged or a rotary.

Drag race engines with roots blowers normally put some fuel in above the blower to lubricate, cool and seal the rotors, then some into the port to fine tune distribution. As a general rule on American V8s they run carbies for petrol and mechanical fuel injection for alcohol, but they run EFI on smaller engines. The tendency not to run EFI on bigger engines is the limits imposed by fuel flow through the injectors and the need for costly multi injector systems. I am not saying no one does it, I a just pointing ut what the vast majority do and why.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[thundair]

I seem to remember a Kawasaki motor that had an injector at the throttle body to enrichen on high speed runs. Something to do with the pressurized air box.

Cheers

I don't know anything but the people that do.

 

[BrianPetersen]

Quite a few production motorcycle engines use two injectors per port. There is an "inner" one at the usual location just downstream of the throttle, and an "outer" one that uses a shower-type spray patter in the airbox pointed down each intake runner.

Current-production Honda CBR600RR is like this, to give but one example.

 

[GregLocock]

In the late 80s it was difficult to get good idle control from an injector that was big enough to flow enough fuel for WOT, for turbo engines in particular. So a fairly common solution was to use multiple injectors. I vaguely remember Lotus ran 6 injectors on the 4 cylinder Turbo.





Cheers

Greg Locock

SIGlease see FAQ731-376 for tips on how to make the best use of Eng-Tips.

 

[PackardV8]

It is not uncommon in street drag racing engines to have two complete fuel systems, one for street use-91-octane and one with race gas/alcohol and nitrous oxide.

Back in the bad old days, when EFI was new and large capacity injectors were not available, I tried my hand with a Haltec F1 with a wiring harness for sixteen injectors. It was a staged system, but the software was not able to handle the progressive transition. Not surprising it didn't survive.

thnx, jack vines

 

[allessence]

In designing a system for 2 injectors it really has to do with needs.

In my quest for ever increasing VE and greater boost pressures you soon find that the amount an injector can flow to the amount the stock ECU can control becomes an issue.

Say you have a turbo charged SAAB. ( my favorite) and on 94octane I can run 28lbs of boost with a 9.5-1CR. (I can and do)

The problem becomes in theory that for the amount of HP say 320HP I am supposed to run 46lbs injectors for the Inline 2.0L engine.

On standard Bosch 2.4LH the system can't handle the timing of the injectors though they are fired in batch.

So, the next step is to make(megasquirt) or buy an aftermarket that will control the injector.

This sounds good right. Well, with that large of injector you will have a hard time at idle to set it up and fuel MPG will suffer.

the next best solution is to keep the stock 24lbs injectors and add another further upstream pointed up the runner not down.

Use a throttle switch and pressure switch to control the on/off of the secondary injectors and just use the pulse signal from the main bank as the trigger signal for the secondary injectors. You can setup a small relay circuit for the secondary injectors.

Anyhow, in the next few months I am actually building such a system as a test bed for some parts I am producing. Should be interesting.

 

[Bribyk]

We discussed this recently (in relation to a dual-injector Corvette) but I couldn't find the thread again.

There are ECUs available that will control large injectors at idle.

 

[DigitalGT]

FWIW MegaSquirt has more than enough resolution to accurately control large injectors (like 46 pounders) at idle and low load. I know plenty of guys using 46 lb/hr or larger injectors with MS and they have no issues at all and still have good fuel economy.

I use 60 lb injectors on my 2.0 twincharged SVT Focus running upwards of 25 lbs of boost and I had perfectly good low load and idle fuel control using the a modified OEM ECU and later on using a Haltech E6X. I have lost economy but that is to be expected when adding a roots blower and a turbo.

Take a look at your fuel pressures and lower them if you don't need extra headroom. If you can flow enough fuel through your injectors at WOT and 45 PSI of fuel pressure, why keep fuel pressure at 60 PSI and decrease injector pulsewidth down to the point where the injector can't respond quick enough? So long as you still get a good spray pattern AND you don't max the injector out during peak fuel consumption, a lower fuel system pressure does nothing but increase your accuracy.

 

[JoeSchmo62]

Actually we sell and use an engine management system called Big Stuff 3. It is a sequential efi system and can drive at least two sets of injectors. The injectors can be different sizes for the primary and secondary. Its very easy to do. You size the smaller injector like you would for light load, idle and cruise and after you go to wide open throttle and reach a user definable parameter like 82% injector duty cycle. The ECU switches, determines the fueling strategy and controls the second bank of injectors as well. If you only run at WOT like in drag racing, it would be no different. We use 16 injectors at 160 lbs/hr at 65 psi. Alcohol would also work fine. We run mid 6 sec at over 210 mph at 3045 lbs on race gas. It would be no different for pump gas. The system is a stand alone engine management system that's model based, so it's reasonably easy to configure and tune. You have complete control of timing, fuel and target air/fuel if in closed loop and many other parameters. If this is something along the lines of why you are asking the question and need more info, email me. -- Mike

 

[havok91]

Look at

http://www.nelsonracingengines.com

They have set-ups like mentioned above - octane on demand is what they call it.

 

[patprimmer]

A comment like octane on demand does slightly less than zilch for their credibility.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers for professional engineers

 

[SomptingGuy]

My innocent, low key question seems to have attracted all the petrol heads. My reason for the original question was quite mundane - I was probing to see if a restriction on fuel injectors to one per location was likely to be a problem in a simulation.

- Steve