I'm always reading that bigger injectors aren't necessary unless going bigger turbo. What about stock turbo and bigger cams? I'm working on my tune and no matter what I do, I can't get A/F lower than 11.6:1 after 5500rpm. I've dropped applicable cells to by 2 full points with no effect. At 5500, IDC calculates over 100%, but I've read that it isn't always accurate since IPW has other factors involved that we don't understand yet. It seems to me that I'm maxing out the stock injectors above 5500rpm. Mods are listed below. Log is attached. Is it time to go bigger?

 

I really would like to know also I'm going to be adding some mods and going for a retune but don't know about injectors

final mods

Ams tbe
Ams fmic
Nisei licp
Hks rs intake
Cosworth cams
Fuel pump
Hallman mbc 23-24 psi 93 oct

INJECTORS ?????

 

I would trust your IPW readings. Some people do not believe them because they don't think it is possible to run over 100%, but it is entirely possible.

At 25 psi on pump with GSC 264s I logged 105% in the mid 6k rpms.

You can also look at it from the standpoint of a generic injector sizing formula. I don't know the numbers off the top of my head but you can go to RC Engineering's website and punch in your HP and other factors to see what size injector they recommend. It never hurts to go bigger for a margin of safety.

 

well the formula must be wrong... from memory its:

IDC = IPW * RPM / 1200

Now if you are running 100% that means your injectors are constantly injecting right? any more than 100% means you injectors are unable to keep up and potentially you are leaning out...

eitherway its a fairly cheap upgrade once you are already at 230kw+atw...

 

So greddy 720cc good enough for me then??

Ams tbe
Ams fmic
Nisei licp
Hks rs intake
Cosworth cams
Fuel pump
Hallman mbc 23-24 psi 93 oct

 

The ECU can command over 100% open time, but it's physically impossible for the injector to stay open more than 100% of the time. Fuel delivery will be the same regardless of duty cycle, once it's over 100.

The stock turbo, regardless of other mods, can not flow more than ~43 lbs/min. Most poeple see 42. I saw 42 99% of the time, and 43 on cold nights. This is with the wastegate actuator vacuum line completely removed and the WG wired shut. That being the case, the stock injectors will hold AFR at 11.0:1 or very close to it. IDCs will vary between 98% and 102% depending on circumstances and fuel used.

11.6 is too high, first thing that comes to mind is fuel pump (but you've upgraded sifficiently), and then low fuel pressure (but I don't see an adjustable reg in your sig). I'm not sure what the problem is in your case, but you have two options. Find out the source of the reduction in fuel delivery per IDC, or simply upgrade injectors and be done with it for now.

 

I thought the stock IX turbo was good for 47-48lbs/min.

 

As far as I know, the IX turbo has the same compressor wheel as the 8 turbo, so it is still limited to 43 lbs/min. The EVO Green only does 49, for comparison's sake.

 

try adding a lot more fuel, if the car doesn't get richer then you probably do have a fuel pressure issue or the injectors are too small.

some people botch the fuel pump install and get an internal leak inside the tank so the pressure isn't where it's supposed to be

 

we discussed the over 100% IDC on another board and came to conclusion that the injector scaling was wrong, I think on our IX's its set to 513, but the injectors are 550cc's... hence the IDC going over 100%..

 

I fought this problem for weeks. I had to keep pulling the pump and putting the grommet back where it belongs. As soon as I hit full boost, the fuel pressure would push the grommet all the way down the pump's outlet. Tried 2 or 3 different parts. Ultimately I just cut a short length of 3/8th fuel line to act as a spacer between the grommet and the pumps body, and cut it a touch too long so there is some preload on the grommet when you snap the cover over the pump. I can now build 100 psi on the regulator (compared to about 75-80 on previous installs with the same reg).

 

fuel pressure is a wonderful thing

on my Stealth I have the LM-1 + RPM converter setup to get a signal from my fuel pressure transducer and map sensor. Now I can make sure that as I raise boost I see an equal gain in fuel pressure, and if I don't, I crank the voltage up on my Kenne Bell boost a pump.

 

I installed the TTP 745cc injectors and set the scaling and latency according to Scott's recommendation. IDC from 5500rpm and up are now at 80% and AFR is 10:1 flat. I'll be retuning the top end back to mid 11's, but its nice to know I've got some head room now.