Breaking up in boost ka-t

[apex128]

Hey everyone. I need some help diagnosing my zenki. It is a ka-t that breaks up every time i make full boost. Part throttle pulls are fine, but when I do a full throttle pull, as soon as I hit full boost, the car starts sputtering and breaking up real bad. The wide band reads super lean also. At first i thought it was an ignition issue, so I reduced the gap on the plugs from .032 to .020. I also put on a new cap and rotor, ngk plug wires, and it has new spark plugs that are one step colder than stock. I am trying to tune it on nistune, but I can't because it breaks up and goes lean everytime I try to do a pull. I can upload nistune maps / logs if needed. Any help would be greatly appreciated from you ka-t / turbo guys out there. Thanks :)

[KAT-PWR]

Post the map. Have you pressure tested the intercooler piping?

[apex128]

I haven't pressure tested the intercooler piping, but I have a boost gauge and it holds 8psi of boost the whole time. Could it still be a boost leak? Here is my map / log: https://drive.google.com/open?id=0B4E7nx8fH4GDdUdOTDBKMVV2Y1E

[apex128]

Right now I'm leaning towards fuel pump because I pulled it out the other day and the previous owner was running it with no sock! Also, the car had been sitting for three years before I bought it. I'm going to replace the fuel pump. Could it also be the injectors? I thought 370cc would be enough flow for 8psi on a t28 looking to make ~250whp with a ka24de. Thanks for the input.

[ZaK687]

do you have an adjustable fuel pressure regulator? i know i didn't realize i had set mine a little high and i had the same problem where i couldn't pull WOT but partial throttle it would be fine.

[KAT-PWR]

Yes you can still make pressure with a boost leak, the turbo will be spinning much faster than necessary.
Your symptoms sound like a boost leak. Or your plug gap is too large. If your fuel pump was the issue you would have probably already leaned out the engine and melted the piston.

[apex128]

Stock fuel pressure regulator.

Also my boost pressure remains constant the whole time so even if I do have a leak it would be really small, and that shouldn't cause a lean condition right? I have a draw through maf so it measures air coming in before the turbo.

What should my plugs be gapped to?

[ZaK687]

draw through is the setup that is affected by boost leaks because youre loosing metered air after the maf. I have some experience with KA-T's but not as much as KA-T PWR. You can still hit max boost with a boost leak but the onset of boost will be slower and there will be a steady loss of air. for example my setup had a boost leak but I would still be able to hit max boost(didn't have a big issue with bogging or anything since I have a blow through setup, Ive blown my piping a bunch of times and itd just run like a wimpy NA motor) after I fixed the leak I hit max boost faster.

that's just my .02 and my limited experience.

[KAT-PWR]

Stock fuel pressure regulator.

Also my boost pressure remains constant the whole time so even if I do have a leak it would be really small, and that shouldn't cause a lean condition right? I have a draw through maf so it measures air coming in before the turbo.

What should my plugs be gapped to?

Sorry didn't re-read the entire thread when I responded earlier was trying to do some candy paint stuffs for the first time lol. Does the car go rich, break up, then read lean?
Also as the dude above posted, the turbo will make 8psi even with a hemoraging leak, it is just spinning much faster (more than it should) to sustain that pressure but it will absolutely do it at sacrifice of turbo longevity.
Draw through maf is trash in my opinion. Blow through is up there on my list of things that make your life way easier. Draw through will suffer from any leak in the system after the turbo (so everywhere) a blow through maf will run fine as long as nothing leaks after it (usually run them shortly before throttle body) so basically the only place that a leak would matter would be the TB coupler or intake manifold.
Draw through has 6+ additional and more likely places to leak (intercooler couplers)

I gap plugs at .032 or .028

[ZaK687]

+1 blow through, makes having a bov easier (if you are so inclined), my setup has the maf a few inches before the throttle body with the couplers jbwelded to the housing to make sure that if the piping blows, it will still run as if NA so you can pull over and find where it blew apart. It doesn't take much to make it blow through and makes it a hell of a lot easier overall, also I believe my plugs are gapped at .28? one last thing to just be thorough is make sure your timing was done right, even if it runs as is, your timing may be off and itll cause issues when youre higher up in the power band.

[apex128]

I checked the ignition timing and it was set correctly. The afr starts at like 12, then gradually gets leaner and leaner until it hits 18+ and maxes out the gauge. I'm really afraid to hit boost until I fix this issue. Could a fuel pump work fine to a certain point, then fail to maintain pressure as fuel demands increase? Also, do you think my injectors are big enough to accommodate my setup?

[ZaK687]

I don't see any mention of what turbo you plan on running but from what ive read 370's are just about maxed out around 250 hp, im running a hybrid t25/28 with 370's at 14~ psi and at lower boost my afrs are in the 10-11 range but at 14~ psi I see it move towards 12 on the wide band, that's why im stepping up 550's. wishing I saved my money at the start of my build and went with 550's from the get go lol.

I don't think a fuel pump will drop off as fuel demands increase, its supposed to crank at a constant level all the time if im not mistaken?

[KAT-PWR]

Yes it could be fuel pump if it slow sly leans iut

[apex128]

I have an isr t28 turbo at 8 psi. From what you described the 370s should probably be fine for now. They came with the car so I'm not gonna complain lol. I will probably order a fuel pump this week. I was looking at the aem 320lph and the deatschwerks dw200. I've read a couple bad things about walbro and am kinda shying away from it. I also like how the dw200 supports ethanol incase I decide to go that route in the future. What do you guys reccomend for a ka-t?

[ZaK687]

ive got a walbro 255lph pump and its working great for the past 2 years. I don't think it makes a difference but I run it to a toggle. I got mine used and it does the job perfectly.

[KAT-PWR]

Have you direct wired your fuel pump using a relay?

[Frank_Jaeger]

16 with a Nistuned Zenki KA-T

God bless.

EDIT: I got a Walboro 255 for my SR. They seem to have a high DOA / early failure rate but personally I've never had any trouble with them.

[KAT-PWR]

It is common knowledge that Walbro is the most counterfeited pump out

[apex128]

Thanks for the input everyone. I have not direct wired my fuel pump, but I get 12 volts during priming before startup, so I think it's getting good voltage in boost as well. I'll replace the fuel pump and then post back here if it fixes the issue. It might take a while to test it though because it's winter now and I don't have snow tires lol.

[KAT-PWR]

Relay will cost you $4 and 10 minutes
start there

[apex128]

I thought the pump was fried from sitting so long and being run with no sock, I guess I might as well do the relay first though.

[apex128]

I should have updated this. Changed the fuel pump and it runs great.