I ran my 17% on stock injectors (340cc), pinged, not good, had it tuned, pinging improved, but came back as the temp here (san diego) dropped below 60 degrees.
green dotted line-- 17%, stock injectors, pre tune
red doted line-- 17%, stock injectors, post tune

you can see that there isnt much improvement in the early RPM range, this is where I would ping(4-4.5k)
I'm at sea level, doesnt get that cold here, and I know theres a ton of people running these pulleys without a thought to what there is to gain from injectors in protection, not to mention power.
the outcome after 450cc injectors was a lot more control and great gains in the width of the torque band, I've got over 190tq from 3-5.25k

compare this to the first tune, you can see not only is there a lot to be gained, even though the motor we have is cast there is a risk of running too lean...


hopefully this is helpful and gets some folks to treat their cars right.

 

thank you, you answered my question with proof on weather or not i should go with bigger injectors when using a 17% pulley

 

The octane of the fuel does make a differance too...with 93 on the eastcoast, the pinging is generally not annissue, especially if you are using sparkplugs one step cooler than stock.
That having been said, when my S was on the Dino (pre-tune) with the JCW 380's the fuel/air ratio was actually pretty good...still a tiny bit lean (at the top end) but pretty safe (a little bit rich down low, but pretty good), not the super rich like folks said...with a 15 I bet it would have been too rich....
Remember, modded cars need more fuel to make more hp, and with E-10 fuel, the volume of fuel needed higher in even a stock car, modding a mini and adding more fuel (a tune really helps, even though thecJCW's can be run without) is needed to make SAFE power...our cars come from the factory pretty rich...and that gives us some flexibility, but IMO the $$ spent on the injectors with a 17% is money well spent.

 

Great point with the 93 octane zippy, not even an option for me (thanks CA) so didn't even consider it while writing this

 

hmm thats true, i live on the east coast so all ive ever been able to put in the MCS is 93 as almost no one has 91 over here.

 

A tune does help overall, but for practical concerns...from what i understand...
The larger reduction pulley makes a hotter intake charge... The warmer the intake charge, the higher the octane (in part) needs to be to prevent pinging. The motors computer will enrichen the mixture quite a bit as the intake temps climb to both cool the motor, and make the motor run a bit richer, preventing detonation and ping...the side effect of this is richer than optium operation, and the other thing the motor adjusts is the timing...it it retarted, also reducing power. With 93 octane, the charge is hot, but the timing is usually not pulled....a few tests showed that with 91 and a 15 on a warm day, the timing was always retarted a bit (done on a cylindar by cylinder basis on the mini from the article I read by Dr O (Matt).
IMO if you are going to run a 17 as a low rpm daily driver on 93, youbshould be fine, but if you like rpm's, want max power, or are going to spend $$ on a tune, get the injectors....mine is a daily driver, but I did the injectors and tune out of an abidance of caution...and it is a huge improvement...saved me the cost of a sprintbooster perhaps, got me a few mpg's, and made the car run smoother, and the dsc less intrusive.
The 15 seems fine from no other mods, the 17 seems to benifit more from injectors, tunes, etc...more aggressive mod, but more fun!!

 

Awsome info!! Very useful in helping folks "connect the dots" so to say with difference mods and the effecton A/F ratio's and different issues. Nice pics too!

 

I really don't like the idea of aftermarket injectors, though my experience is with other cars, the mini might have a great aftermarket segment for this. Obviously 400's and up offer considerably more room but for a car with an intake and a 17% pulley do you think the jcw 380's would be enough with 93?

 

Take a look at RC engineering's website and use their calculator, I don't have a link handy, sorry. It doesn't take octane into account at all... not really sure why. You'll see what size injectors you need by crunching real numbers. The reason I posted this thread is because of questions like yours, there is a very good reason Bosch makes a huge range of injectors sizes, they work under ideal conditions for their application until we change those conditions... the charts show exactly what that change does to the afr.

and of course the jcw injectors will work, this is more about having the engine run as wells it can, I would never want to run a boosted can lean.

 

The spray pattern on the mini is a "dual-cone", so a redrilled injector does not duplicate this.
Early on in mini tuning, the only injectors the tuners had maps for were the JCW's from the jcw tuning maps..but now they have maps for other sizes to use. A basic 17% with an intake and tune like mine, no exaust and no cam is ok with the 380's...could I have gotten a couple more hp with more fuel, maybe, but with the 380's I am confidant they are an oemmproduct, and were plug and play before the tune...bigger ones are iffy if you install them before the tune...just too rich without the scaling a tuner does to the fuel maps for the injectors...
IMO of you are gonna do a cam or more go big, but otherwise, just get quality, not redrilled injectors, that suit youbplans...
For me, the 380's were perfect, good price, and could be installed well before the tune. Other people may have different opinions, since we all have different priorites.

 

PS from a technical standpoint the octane does not effect the volume the injectors flow, but from a practical standpoint, the car's computer will try to run the car richer (more fuel) to deal with high intake temps, and/or possible ping/knock...it is one of the "copeing" strategy's the computer uses, along with timing adjustments....
So functionly the octane affects the volume of fuel needed on some level