I'm not quite sure if I understand the math/formulas/ where you get the numbers from...ie x. I'm running 1000cc injectors on E85 which should be scaled to 30% more than pump. I've got 636 as my scaling- it seems to be correct, as my fuel trims are really good (+-2). Just wondering if my scaling fits/equals the equation correctly.

 

RC Engineering cleans SOOO many injectors and I bet they have a database of tested injectors if someone is ambitious enough to e-mail them lol. www.rceng.com

 

The JDM Evos have 54(0x36) for injector size.

31050/54 = 575cc

I'm unsure why the US Evos have a smaller injector size. Most likely because of the amount ethanol and other junk in our gas, slightly more fuel is need to maintain stoich.

 

This is what I recall hearing a longgg time ago. We'll probably know for certain what the reason is though.

 

You would think that simply throwing in a larger "KNOWN" flowing injector and doing the EXACT injector size for that particular injector,lets say FIC 1050'S (which the closest value available is 31050/30=1035), would net the closest trim values.

It doesn't help that everyone modifies their airflow so much with:

• free-flowing air filters
• intakes
• better flowing piping & IC's
• throttle bodies
• Intake Manifold's
• head porting,valve work

These things can alter the MAF readings and its easiest to compensate for it with the injector scaling, so you will find a lot of different injectors scaling for the same injector.

 

Ages ago I did my own formula for injector scaling which is 30240/x This was for a JDM VII with 560 injectors. Works pretty much fine for me.

 

Since this thread is being discussed again, I'll toss out a few observations.

- In the actual fuel pulse width calculation, the injector size is not used with any scalings.

- The injector size is used for a few OBD calculations, and when it is used for these, it is consistently used as 582/(injsc*256).

582/256 = 2.2734

It doesn't correlate to either 29241 or 31050 in any simple way, but I figured I'd mention it.

- I would assume that the ECU is setup to use the injector size as cc/sec, so a factor of 60 likely has to be in the injector scaling value for cc/min. Interestingly, 60*512 = 30720 which darn close to the scaling values that are being discussed. If I had to bet on anything right now, I'd bet on that value.

- When talking about basing a scaling value on the fuel trims and a known injector size, it has to be kept in mind that there are a bunch of other factors that play into the fuel trims, in particular, the MAF scaling table plays a role, so its pretty tough to make the connection that way.

- The ideal thing to know would be what Mitsubishi thinks is the correct injector size for several different Evos.

- The most practical thing to do at this point would be to send a factory injector to a place like Fuel Injector Clinic to have the slope flow calculated, and then use that to set the scaling formula. Perhaps I'll do that.

 

My Denso 720cc (Sard brand) is 714 cc/min after using Mychailo's new scaling number.

One proof that is very close.

 

You sir are dedicated . I know there's a lot of threads cross talking about this Rom, but will the maf definitions be brought up to times as well? It would seem like some would have to but after some time I've grown to appreciate the physical measure of airflow. And I'm looking forward to fully understand a maf system

 

the true maf scaling would be even more work to determine. however, i also think its not needed if the true injector scaling is known because the maf scaling and compensation both just serve to linearize the maf reading and make the afr table true. if good injector size and latency values are used, then the maf can be dialed in by watching fuel trims and open loop afrs. besides, who runs maf anymore except me?

 

Mrfred, from a theoretical perspective, I would bet they are actually converting to g/s at some point. This means there is likely a fuel density value factored in some where.

 

Got a point. So the density of gasoline is ~0.7 gr/cm3. I guess I'll think about it a bit more.

 

Mitsu use a calc based on mcc/mSec

with a eval of 569/x

where x is the injector raw size

for our purposes, this works out at

34140/x

for a scaling in cc/min

 

Well that's hella different. That makes the USDM Evo 9 injectors 600 cc/min injectors. Now I really want to have one measured.

 

Its a bit of a head scratcher I will admit.
I know that eval is true for evo6 and evo7, plus most if not all earlier ecus.

Did they change it for the evo9, I do not know.

But I have found that using that 34140/x eval does seem to give the correct size (with 2.7bar) on most non-stock injectors, which helps a lot in dialing in new injectors.