I have an '04 G35 with a JWT TT kit on, using the standard SS box, only timing wires hooked up, like it comes from jwt, running fmu and walbro 190. My car has been running lean (12.5 to 12.8 A/F) After trouble shooting just about everything I finally got the Cipher and we took some logs and it turns out my injectors aren't on long enough. 20 milliseconds and I think it should be 23 or 24 milliseconds. Does anyone have any idea what could be causing this? How should I proceed from here? Any help or suggestions would be greatly appreciated!

 

just wondering what is the best a/f ratio to be at anyways? i have the jwt kit too. when my car idles it reads 14.7 to 15.0 is that normal? but once i stomp on it i get about 12.5

 

At WOT, you want to be in the 11's.. specially when you hit your max torque, around the mid range for the standard JWT kit. An A/F ratio of 12.5 at WOT and full boost is too lean for pump gas in my opinion.

 

How much boost are you both running i think on a stock block you should be around 7psi?? I now that my car also runs lean but its because my boost is at 10-12psi.

 

Check fuel pressure - I believe the stock JWT kit using a rising rate fuel pressure to force more fuel through per given time. If you have Osiris you can reflash to increase injector time... I would figure out why it's running lean in the first place though (i.e. either airflow increased or fuel decreased). If you have TP, you can go back to cats .

 

Fuel pressure is right around 78 - 80 psi, which should give me the correct A/F according to JWT... I am running lean because my injectors aren't opening long enough, that is the problem. We tested the fuel pump, the FMU, got A/F readings from both banks, and finally found out that it's the injector pulse width. Without modification the pulse should be 23-24 as far as I know, and instead we're seeing 20 milliseconds... So I am basically trying to see if anyone knows why I would see that pulse width.. and is the only solution to re-flash the ecu? (no test pipes either). Thanks for your help and suggestions!

 

I am running a stock kit, on the stock wastegate springs, they are supposed to be 6.8 psi.

 

Maybe the MAF is not seeing the correct volume of air. You could try cleaning it. That's the only thing I can think of for why it would be supplying less fuel than usual if you checked everything else using Cipher. Are you sure your A/F readings from both O2 sensors are similar? Maybe one of them is out of whack, causing incorrect feedback to the ECU to lean things up. Also I believe there is a way to get the ECU to use the other bank for making corrections - might want to check the FSM on that. Another easy thing to try is an ECU reset...

 

The Cipher shows the MAF readings as well I think, so I will check to make sure it is reading properly..About the ecu reset, I had my battery disconnected for quite a while, I think that also resets the ecu correct? Guess it won't hurt to reset it again!

 

20milliseconds is alot to command of an injector. It sounds to me that you're maxing it out.. Can you log injector duty cycle?

Are you clamping the MAF Voltage, and or tuning with an external pressure sensor? or are you solely based on MAF Voltage.. It doesent take a lot to max out the Factory MAF Sensor Show us all some logs, that'd help us help you

I've never installed / tuned / worked on a JWT TT car so I have no idea as to what it comes with.. btw so excuse my ignorance lol.

What size Injectors come with the JWT TT kit?

 

The JWT kit uses the stock injectors, and it does indeed almost max them out. An FMU simply increases the fuel pressure to get the desired amount of fuel out of the stock injectors. The MAF is also close to being maxed out as well, but not quite there. I'll get some logs and post them up, just going to be crazy busy the next two days at work, then I should have some free time.

It doesn't look to me like I can log injector duty cycle, only pulse width. Here is the complete list, incase it's staring me in the face and I can't see it
http://uprev.com/text/cipher_functionality_matrix.pdf

 

20ms at what RPM?

It might be time to throw in some bigger injectors and put a Haltech on it. This would alleviate your problems of running lean, maxing out the maf, etc. You could run the car safer and gain power at the same time.

 

just wondering are you still getting on this car with it running that lean?

 

My first thought was going with bigger injectors, but as you mentioned, that requires a more capable EMS and also removing the FMU.. My plans were to run the JWT kit unmodified for a while until I saved up for upgrading further.. so everything should be working properly with just the stock jwt kit

I am not even driving the car at this point, until I figure out this leaning issue..I have it at a shop now and we will put it on the dyno and see what we can do..there goes my plan to save up for more upgrades

edit: 20 ms at peak torque, I think it was around 3500rpm

 

At 3500rpm, you are at ~58% IDC. Now 20ms @ 6500rpm is ~108% duty... no good.

 

There is little you can do to alleviate the problem, except by using larger injectors, and retuning with something other than the included SS box.

 

Hal and Sharif and IntenseFab, (and everyone else too!) Thank you for your responses and advice. I am going to go ahead and get larger injectors and re-tune. One question, because money is a problem right now as I was not planning on upgrading and tunning till half way through the year, I would like to stick with the ss box for now. It can be hooked up to adjust the MAF readings going to the ecu so I can adjust fuel that way. First, if you think this is a horrible idea guaranteed not to work, please let me know If not, and I think this should be fine for just the stock kit for now, what size injectors should I get? If I go too big, I'm worried the stock ecu will freak out while it runs in closed loop at having to cut so much fuel.. so I'm thinking of just going 1 or 2 steps up, to 380cc or 440cc injectors. What are your thoughts?

Again, thanks for the help to everyone who has posted

 

Just a quick update. I picked my car up today, and it's running great The shop ended up using bigger injectors and wiring up the ss box to pull some fuel. Now I can finally drive my car, woot!