Spitting under Boost

[dylansword]

Just got done building my car, and got the boost leaks fixed. And now it is spitting under boost. I have a couple ideas on what it might be, but not sure where to start, and don't want to throw more money at it. It has a holder hy35, and 560cc injectors, running Maft pro in speed density.

I am thinking maybe I need a to get an aftermarket fuel pressure regulator? Or maybe better plugs?
I don't have a wide band installed yet.

 

[hvyman]

Close the plug gap smaller.

 

[IndigoMKII]

Just got done building my car, and got the boost leaks fixed. And now it is spitting under boost. I have a couple ideas on what it might be, but not sure where to start, and don't want to throw more money at it. It has a holder hy35, and 560cc injectors, running Maft pro in speed density.

I am thinking maybe I need a to get an aftermarket fuel pressure regulator? Or maybe better plugs?
I don't have a wide band installed yet.

What psi are you running the hy35 at? What are your other mods to support the 560's and the hy35? Any engine codes?

Without a wideband, how have you tuned your maft pro?

 

[dylansword]

Most psi I've seen is 20, it starts spitting at about 13-15. I've got a Walbro pump, hks ssqv, intercooler and hard pipes. Full 3 in exhaust. No codes. As far as the Maft pro, I haven't tuned much. I was using it before I installed this turbo and injectors, so I just left everything set as it was

 

[IndigoMKII]

Hard to tell if you're going lean under boost or not without a wideband.

I'm not too informed about the maft-pro but could it be that something needs to be corrected in the tune for the added airflow?

You could always pull a plug and check the condition of it.

 

[suprahero]

You definitely need to get it tuned before it's too late and you're throwing a lot of money at it.

Your problem sounds like it's either A. starting to run lean at the 13 psi level or B. it's blowing out the spark, in which case the smaller gapped plug will help like was mentioned above. I would not be running 20 psi without a wideband and/ or a good tune. Good luck.

 

[dylansword]

Thanks for everyone's suggestions. I'll be at the shop tomorrow and look at the plugs. What gap should I run them at?

 

[suprahero]

You'll have to keep adjusting them until you can make a clean run without it breaking up. I used to have to run my plugs at .020........I was running about 24psi, but I was also tuned for it. It still worries me that you aren't tuned. Running lean will make almost the same sound and feel, except if you stay in it, the noise you hear will be followed by a large cloud of black smoke..........lol

 

[IndigoMKII]

You'll have to keep adjusting them until you can make a clean run without it breaking up. I used to have to run my plugs at .020........I was running about 24psi, but I was also tuned for it. It still worries me that you aren't tuned. Running lean will make almost the same sound and feel, except if you stay in it, the noise you hear will be followed by a large cloud of black smoke..........lol

Mixed with a few crunching sounds.

 

[dylansword]

So I put new plugs in, gapped to .025 an no more spitting. I only drove it for a short distance, but it seems when I give it full throttle and it spools up, didn't see to what psi, it runs good and pulls hard, and them all of the sudden, falls on its face. Then I let off the throttle, and it is fine...

 

[supraguy@aol]

You might definitely be running lean then. Which means you could be just one WOT away from a melted set of pistons.
I would richen it up in the meantime, and get my ass to a dyno shop, or install a wideband already.

 

[suprahero]

Are you sure it's not hitting fuel cut? If you keep this up, you can ask for a new set of pistons and rings for Christmas.