Breaking up under boost

[98gstbrad]

Ok so here is my situation, I am running e85 for starters. When pushing 15 psi I have no problems but then when I bump up to 20 psi it starts breaking up at full boost. I am reading 12.5 on gas scale even during break up and I am not pulling any knock, any ideas on why it's doing this?

 

[420a dsm kid]

Have you look for vacuum leaks? Try to do a boost leak test.

 

[dsmpat95]

How old are your spark wires, spark plugs, and what did you gap them too. A BLT would be a good idea too.

 

[98gstbrad]

I have no boost leaks and I am running a gm maf with my vacuum line for my boost gauge directly off the intake manifold. When I cross referenced boost on gauge and boost est. on link they were almost exact. Spark plug wires are maybe 6 months old and I have brp6es plugs gapped to .028.

 

[GSLENK]

I had the same thing happen to me, turned out to be plugs. Mine were less than 6 months old, but they weren't cold enough. I would get nasty power robbing break up above 5000 rpm.

EDIT: I see they are 6 series, I dont think you would need any colder than that for almost any setup . Is it possible they are too cold a range?

 

[ExtremeTurboSystems]

I would gap those plugs down. shoot for .020. High boost applications run down to .018

 

[Boostdriven]

If would get a map sensor like GM 3 bar and wire it in to your car so you can log your boost pressure. You can wire that up in to your stock MDP sensor, it makes it much easier to reference boost and boostest. There is a nice write up on ecmlink.com in how to do all that.

You also want to log airflow and MAF, there is a point where the GM MAF sensor gets over ran and it starts giving wrong reading in which case a MAF clamp needs to be used. It functions like the MAF sensor and you still need to calibrate it like the MAF sensor. I would had the switch point on the MAF clamp be somewhere between 2600-2800 htz.

Get 7es spark plugs and gap them at about .018-.020 and if your planning on running 30+ psi of boost I would try 8es

 

[gimmie11s]

Ive never heard of a GM maf sensor being overran... or an EVO maf for that matter... That is not to say that the GM unit doesnt SUCK becuase IMO it does.

Nonetheless... im having the same issue right now on 20 psi with a billet wheel 20g on e85. Just swapped in brand new BR7es (5122 new part number) and gapped them to .19.

Still breaking up... driving me nuts.

Turn your base timing down... see the thread i just posted in this section...