8 Injectors On An Mi

[acox99 74 1 Cars]

Is it worth putting 8 injectors on an Mi i know they do on things like cossies, but does it help with power gain, or give you a significant power gain? has anyone done it? i saw an article on it:

 

Clicky

 

go into article and it the first one.

 

what do you think?

[Miles 331 1 Cars]

Yes it does give a gain, I've found that buy having the injectors in the bell mouths you can get upto a 10% increase in power at the top end and not allot lower down but this is what the other 4 injectors are for, But on Race car's it's not really a issue. You just get the ECU to phase the injectors over at around 4500rpm

[Batfink 201]

just watch out that fuel doesnt drip down and set your car on fire

[Sandy 191]

That article is on my friends car. That site credits the engine to Mark Shillaber, he did the headwork (which was very basic, but worked very well), but Colin did the rest himself. If you're going to use the set up on a road car, you need to approach it more cautiously. Colins early set up (shown there) cracked out of the trumpets on one event and the fuel rail sprayed all the engine bay. For road use you need to mount the injectors very solidly to avoid vibration related fatigue and the weight of the extra fuel rail etc needs to be well supported or mounted off the engine all together, which makes filtration awkward. The power gains on his engine were genuine and the grunt it produces in the mid range up to the 7000rpm peak, is something only those who've driven it really believe!

[Jonmurgie 2]

It's something I was considering at the start of the year... I was put off by the hassle of mounting the second set of injectors securly... but 10bhp @ peak is very tempting TBH!

[smckeown 1]

It's something I was considering at the start of the year... I was put off by the hassle of mounting the second set of injectors securly... but 10bhp @ peak is very tempting TBH!

 

yeah 10% is a nice increase.

 

shame your expensive ECU doesn't support more than 4 injectors jon

[Jonmurgie 2]

ha ha... that's why I went for the M4 though, given up with the whole fecking thing and want it running and gone

[PumaRacing 2]

I fail to see the scientific rationale behind why 8 injectors would give so much more power than 4. Perhaps you get slightly better atomisation or fuel/air mixing but 10% extra power?? Come on folks, apply a little grey matter here. Are we saying that every engine ever built with a simple carb or one injector per cylinder FI system has produced 10% less power than it otherwise might have done because of imperfections in the fuel/air mixture?

 

You just don't find 10% power gains from anything trivial in engine tuning. You might find 1 or 2% and think yourself lucky to have done so but finding 10% generally means a big valve head or radical camshaft.

 

If a 4 injector setup was working so badly and losing so much power there'd be massive amounts of unburned fuel in the exhaust. That means you'd see very high HC readings and catalytic converters would fail in days. It just doesn't happen. On most engines every particle of fuel you fire into the thing gets burned properly and you get all the power out of that fuel you ever could do.

 

If 8 injectors were so necessary every car on the road would have them because OE manufacturers can't afford to lose 10% to the competition and still sell cars.

 

Maybe there is some small advantage in certain circumstances but in most cases I think the extra injectors are only compensating for some problem in the basic setup.

[Batfink 201]

i think its about atomisation and the ability for the fuel to cool the air a little in the inlet but really its minor gains. Important on a race car when you want that edge over a rivals car

 

I would say its 2 or 3% at most unless there is something wrong with the inlet system in the first place. Surely the gain will depend on the cam and head design, some engines would gain nothing at all?

[Sandy 191]

Better mixture homogenisation and charge cooling is worth something; they found the difference at peak to be 8-10bhp on Colin's (which is about 4%), but more important was that much of the improvement was in the mid range. It made 229bhp at 7000rpm, BMEP of 220psi at peak power, which is pretty remarkable, on standard valve sizes as well.

 

What is important to bear in mind is that injectors mounted part way up the tract and operated sequentially/phased ideally will probably give virtually the same results, but this set up was done on a shoestring with a cheap ECU, you could also account the advantages (on a road car) of better idle and emissions by having the inner set close to the valve.

[Dream Weaver 2]

ha ha... that's why I went for the M4 though, given up with the whole fecking thing and want it running and gone

 

Gone, as in SOLD??

[Batfink 201]

still got that 200sx to make into a drift racer?

[Miles 331 1 Cars]

Forgot to say about the catching fire, On Nick Williamson's old car his theory was just put your foot down and suck the flames in!! Problem solved.

But I;ve seen injectors in the std position and in the bell mouths in various positions and it does give more power, It would be good if you could adjust the position on them when running (I know impossible) to get the most torque and power when you need it.

[Sandy 191]

I know what you mean, the popular way for the outers to switch in is to simply half the duration as they double up, it would be nice if there was a mini map or table to vary the proportion between the two sets according to rpm and load, but it would take alot of dyno time to optimise I would think and considering how many tuners junk VVT without trying to use it, I doubt it would be popular.

[James_R 3]

Emerald can only do a forec switch point rather than said mini map, but alot of people dont have the time (= money) to test it. Although whenever I mentioned it to emerald they've said stick it on can't hurt to test it out

[Rippthrough 98]

I know what you mean, the popular way for the outers to switch in is to simply half the duration as they double up, it would be nice if there was a mini map or table to vary the proportion between the two sets according to rpm and load, but it would take alot of dyno time to optimise I would think and considering how many tuners junk VVT without trying to use it, I doubt it would be popular.

 

 

Which is nuts, because VVT gives a nice torque bost through the lower/midrange. You'd think after try to extract as much performance as possibly they'd do everything to keep it wouldn't you?

 

Megasquirt'n'S-e has got some code for VVT control I think, and dual injectors....

[Jonmurgie 2]

Gone, as in SOLD??

Not sure...

[acox99 74 1 Cars]

cheers for your replies, shouldnt be such a problem of catching fire, because of the angle the MI the fuel should run into the engine anyway, what about race regulations towards to this sort of modification? what sort of internal mods would compliment this best? i can guess bigger valves would make quite a bit of difference.