KA-T Breaking Up in Boost

[apex128]

Hello everyone,

My car is a ka24de with an isr rs3871. Right now I'm just on the stock internal wastegate pressure, so 8 psi. My car also has nistune, a z32 maf, a deatschwerks dw200 fuel pump and deatschwerks 370cc injectors. It is also a 1996 automatic ecu, with a manual transmission swap. The issue is that the car breaks up under boost, causing the afr to go lean. I am fairly sure that it is getting enough fuel, because in nistune it is setup correctly, and everything works in part throttle when I am not making full boost. However, when i hit 8 psi (about 4k), it starts to break up causing my wideband to hit like 18 afr. This led me to believe it was an ignition issue. I replaced my spark plugs with ngk bkr6es, one heat range colder than what I had before. I also got new ngk wires, and a new cap and rotor. When this still didnt fix my issue, i regapped the plugs from .032 to .020. The issue remains. Can someone please help me figure out what is causing the breaking up under boost? This is also my first post, so I hope this is in the right section. I look forward to hearing everyones responses.

Thanks

[apex128]

I put my log and map from nistune in this folder: https://drive.google.com/open?id=0B4E7n ... DBKMVV2Y1E

[PapaSmurf2k3]

Does it happen in every gear?
I'm guessing you have a wideband O2 sensor with in-car gauge. Does it read super rich or super lean before misfiring?
How did your plugs look when you pulled them?

Welcome to NICO! Hopefully we can get this sorted out for you. I'm trying to open your CSV file at the moment.

[PapaSmurf2k3]

Ok, I plotted your RPM vs time based on the CSV file you made. Can you explain what's going on here? Are you revving the engine pretty quickly? Hammering through gears?

I ask because I've had a problem in the past (on my turbo miata) where my crank angle sensor was getting some kind of noise in it, causing the RPM signal to go nuts and read all sorts of different RPMs in a very short time. This caused bad misfires, bucking, etc.

[PapaSmurf2k3]

Not sure how well that video is going to work, but it shows the breaking up I was talking about.

[apex128]

Thanks for the reply. When mine breaks up it's almost as if I can't pass a certain rpm once I'm in full boost. It happens in every gear. Also my wideband goes lean. I can't tell if yours went lean or not in the video. The plugs looked ok. That part of the graph is me doing a WOT third gear pull, so idk why it's all messed up like that. Regarding the crank angle sensor, my car is an s14 with an s13 manual transmission swap. On the s13 transmissions there is no crank angle sensor bracket. Basically I don't have a sensor and I just leave it unplugged. Could this be the issue? I thought if there was no data from the sensor the ecu would just assume everything is fine. I'm not sure though.

[apex128]

If it was the cas wouldnt it be an rpm based issue though? I can freely rev the car to red line with half pedal, but when i put it to the floor and make full boost it breaks up. Fuel issue?

[kingtal0n]

370cc injector is a stock sr20det injector and barely enough gas to run one of those engines to 250-280rwhp.

the turbo you have is not a t-25. I dont know what it flows but I am fairly certain that even if you max the duty cycle at 8psi there still wont be enough fuel for that engine, considering it isn't a 2.0, its a 2.4

IMO you need 550cc injectors for 8psi of boost, assuming that is as high as you ever go, and that will put you what, 70-85% duty cycle (350~rwhp) just spit balling.

[apex128]

The thing is that my max duty cycle shows around 60 on the logs. I can check it again tomorrow though.

[PapaSmurf2k3]

Maybe ask the wiring specialty guys where they are supposed to get the RPM signal for your car then.
S13s the crank angle sensor is in the distributor.

[kingtal0n]

The thing is that my max duty cycle shows around 60 on the logs. I can check it again tomorrow though.

how is this confusing to you? The injector duty would need to be around 125% or something to fuel the engine correctly. You thought duty cycle would automatically adjust to the correct value without any tuning necessary? What did you think 'tuning' was?

[apex128]

60 is the max duty cycle it hits before breaking up. That's why I think it could the fuel pump not supplying enough pressure. I adjusted the fuel map to increase duty cycle, but it never accesses that part of the map, because it can't reach it from breaking up too bad. Also, I pulled my fuel pump yesterday, and the last people who worked on my car were running it without a sock. The car also sat for 3 years before I bought it.. It's probably ruined.