Hey guys,

Did a datalog of my recent trip to the dragstrip. IDC showed high 90's most the run and hit 100 once. Am I really maxing out the stock injectors?

Mods are: Buschur TBE, no cat
Buschur filter
Flash w/ ecu boost control and pill. Boost is around 26psi I believe, my gauge is not very accurate and I am on the waiting list for a jdm map. I will post up my log when I get a chance (or figure out how)

SQ

 

If you get a fuel pump, you will be able to reduce Inj. pulse width and it will give you some more room, but I was running out of injector at redline with high boost and my basic bolt ons... now with 780's I only hit 70% IDC at redline

 

I do not think you are. The IDC calcultion is pointless on an Evo 9. A stock Evo 9 hit 100+ IDC. So are the injectors getting maxed on a stock 9? Hardly.

The best way to figure out if your injectors are maxed out is to richen your target AFR and see if your actual AFR changes. If it does, then you are good. My 9 hit 99-100 IDCs and I am still able to richen my actual AFR with a 0.1-0.2 change in target AFR.

 

I still think that percentage is based on scaling anyway. But like NJ said if you can adjust your AFR's still you arent maxxed.

 

ok thanks guys. I was just going off the idc value in the logs, didn't realize it was not accurate.

SQ

 

If the IDC is based on scaling etc, can you not use the presets in Mitsulogger to get a real number? Or is this what you mean of not getting a real number?

 

They are basically saying that the IPW is based on the scaling and the IDC% calculation is based on IPW. Since the injector scaling is actually lower than the real injector size it skews the results. At least that's what I got from it.

 

Right now I'm at about 370 whp on the stock injectors and walbro 255 and I'm running super beyond rich....like 10.0 at full throttle according to my A/F meter

 

I'm sure there's a way to reverse engineer it from an existing log if you knew the forumla it was applying to the ipw for the scaling? Then you could change the formula to be for stock inj size and get a viable IDC?

I just remember where I cleaned a set of injectors plow from my DSM days and new what I needed for what turbo. In other words I threw a set of 850's in and called it a day.

 

To adjust the value of the IDC you logged to one based of scaling it would be like this:

IDC * (scaling/actual injector size)

e.g.

100% IDC * (513/560)=91.6%

 

I knew one of the resident genius'es would know how to.

JB with the save.

 

Rule of thumb also is you don't want to have your injectors running above 85% duty cycle, and most seem to keep it towards 80%. Sure, you might not be maxing your injectors running at 95% duty cycle, but I'll bet you they're not liking it. I ran the numbers real quick, 560cc injectors at .55 bsfc (probably is a hair higher for evo's) @ 95% duty cycle is right around your 360hp mark (I actually come up with 562.30 as suggested injector size for that d/c). To keep it closer to an 85% d/c your injector size should be somewhere near 628.46cc's. Bigger is sometimes better though

 

The other thing that your formula isnt taking into account is the increase in fuel pressure making the injector act larger to keep it cool. Really as long as the injector isnt static the amount of IDC below 100% is inconsequential more or less. Eric posted up some really nice math showing exactly how much fuel the stock 560's are capable of flowing in lbs per hour/min compared to what the turbo (stock in his example) is capable of (42 lbs/min).

Remember there is ideal and then there is real world. Mitsu has overengineered pretty much every other part of the engine I am sure there is enough injector there. Kreionic made 370whp on stock injectors and a fuel pump, as have many others.

 

I'm lost on the scaling affecting IDC values, since IDC should simply be IPW vs available cycle time. Unless people are suspecting that the IPW value used in the IDC calculation is something other than "actual" IPW/IOT? I'm the lost new guy here though. Though I've been reading this forum section for a week non-stop, I'm sure I've missed a lot of discussion here regarding this topic.

I can however post up a comparison using stock turbo and stock injectors on both the stock EVO8 ECU and the 2g DSM ECU. Mathematically, 560s at 43 psi with a fuel specific gravity of .76 and a target AFR of 11:1 will support 41.2 lbs/min, and provide a calculated IDC of 102% at 42 lbs/min.

The 2g ECU with the stock turbo maxed out at 42 lbs/min reported IDCs of 101-102% consistently. I love it when the math matches reality.

The EVO ECU is also reporting 102% IDCs, which is what I expected. The EVO ECU definitely adds fuel with knock, which I gathered from reading here and looking at the tables in ECUflash. I had it bump IDC up to 115% this morning at 4 counts. The DSM ECUs only used timing retard as a countermeasure against percieved knock. Interesting to see this in the logger this morning. In all fairness though I have to add that I haven't verified airflow yet, but the turbo is maxed out so I don't expect it to be anything other than the usual 42 lbs/min. And I've also been logging the stock ECU for a short time only. I don't know that no additional fuel is being added over 100% IDC on the EVO, but that was the case on the 2G ECU.

I'll also add that in the last 7 or years of maxing out injectors on DSM and EVO daily driver/drag cars I've never been able to spot any measureable downside to running injectors at or near 100% IDC. Theoretically due to the dead time you lose some resolution/control over the injector at high IDCs, but I've never seen any negative impact from this. YMMV, and I'm certainly not recomending everyone run them at 100% for years on end, of course.

 

Well this is where I go from proof to "what I think". Chances are I am wrong about the method, but just based on logged airflow vs the amount of fuel it would take to maintain a given AFR I think it may plausible at any rate. I think its a case of a 1byte verus 2 byte reporting method (or similar concept). I noticed when I started the base tune on my car when I went to the Green that at 21psi I was getting 78% IDC with 780's. Now I am not the best when it comes to ECU specifics (I punch keys thats it) but even I could tell that 78% IDC with 780s was not likely at that boost level on that turbo.

There should be an easy enough way to test this theory though and I honestly didnt think of it until I was typing this. Someone on a stock turbo and stock injectors that is rescaled to 472 compare a log to when your car was on 513 scaling. Or if there are 2 cars that are similar enough in mods other than scaling we can compare.

I dont mind being proven wrong, I just dont have time to prove myself right.