help! Boost cutting and boost fluctuating

[bdillon]

ok so i need some help! ill start off by telling you my only performance mods are turbo xs BOV cobb SRI and i just installed a turbo xs downpipe/race pipe two days again and that seems to have made my problems worse. Before the dp my car would boost cut in 3rd and 4th gear rarely but now it is becoming more frequent and i need to do something about this, also my car is on stock boost and it will reach that in every gear but will slowly creep down to 11 or 12 not sure what is causing this! I was told to do new spark plugs and i was thinking i should do a step colder so if anyone who has done that has any suggestions on what to go with that would be great! any help you can give me would be nice!

 

[MSMS3]

How many miles do you have on the car? How many miles on the current set of plugs? What is the current gap on those plugs? What is the weather there now - outside temperature? How is your BOV set up -- full recirc, I hope? Where in the rpm band does the "cut" occur and at what boost psi? Answering these questions will help with diagnosis.

 

[bdillon]

How many miles do you have on the car? How many miles on the current set of plugs? What is the current gap on those plugs? What is the weather there now - outside temperature? How is your BOV set up -- full recirc, I hope? Where in the rpm band does the "cut" occur and at what boost psi? Answering these questions will help with diagnosis.

I am at 49,000 on the car and i would assume they are the stock spark plugs with means that is the same amount of mileage on them as well. The weather is around 50 or 60 degress. Yes my BOV is full recirc. Rpm ranges between 4 to 6 grand when it boost cuts and i am assuming that it is around 14 psi but i am not sure of that due to the fact my boost slowly creeps down. i am stock boost. it has not been messed with since i have owned the car.

 

[Darth Vader]

Get those goddamn iron s*** stock plugs out. 49,000 on a turbo car is WAY too long. See what that does for you. I love this, man, putting a bunch of flow mods on a car and leaving high mileage stock plugs in. This is basic stuff, man.

Something's weird here, if the plugs don't cure. If you used to "boost cut" in 3rd and 4th, you should be boost cutting like mad in 5th and 6th, where load is higher.

Boost cut, is a wham, right in the kisser, cut. Is that what you're feeling?

A gradual softening suggests fuel cut. This cut isn't bad until the pressure gets really low.

Load cut is also a smash in the face hard cut.

 

[MSMS3]

Agree. Darth has described the kinds of "cut" well. With your mods and old plugs, you gotta replace them. Stock heat range is probably o.k. where you are in tuning, although I went one step colder just for a little protection against possible detonation. Not really needed. Make sure those plugs are thin wire iridium tips, either OEM, Denso or NGK and gap those mothers down to about .028. Be careful messing with gap because the iridium on the center electrode is very easy to damage.

With the catless dp/rp you should be seeing 17-18 psi and maybe some spikes to 21. After putting in the new plugs if you are not seeing something like that hit us up again and we'll try to figure out what is going on.

If you are still getting "cut" after the new plugs, try to describe it a little more accurately. Like Darth says, true load or boost cut will try to throw you into the windshield. It's abrupt and strong, and it's likely to happen under full boost but before 5,000 rpm. It will get your attention, a lot like what you feel when DSC kicks in when you lose traction. It's a bucking sensation. If it's softer and higher up in the rpm band, it's more likely to be ignition misfire or fuel flow problems (pressure or volume), especially in the higher gears under load.

 

[manselainen]

If it's not the plugs, couldn't it be just normal behaviour of stock tune with it's safety limits and boost tapering, in connection of said mods? You might want to try HT...

 

[the_caruch]

Yes i would change plugs. But if they are gapped correctly i doubt that is the actual problem. Your HPFP is probably maxed out too. At this point you are most likely hitting boost/load cut. You can get the AP to fix it but would also look into upgrading the HPFP as it's a crucial part to keeping the engine happy