Breaking up under pressure

[2K4NightRiderSRT]

MS2-Extra RC1b code

I've seemed to have hit a wall in my tuning efforts. When I boost to ~145-150 Kpa or higher (or 10 psi boost on my mech gauge), my exhaust sounds (which is the only thing I can hear) like a little kid making low-pitch machine gun noises with his mouth and feels like heavy engine breaking. Every time in that area and higher. What's confusing me is that my AFRs seem to be fine (~ 12.5-12.7:1 AFR) and my spark angle is between 17-20 in that area. This is at 2500 RPM, and my rev limit is set at 6000. But it does remind me of hitting the rev limiter in previous cars.

What am I missing here?

Vic

[SpeedEuphoria]

whats your plug gap? what gas?sure its not detonation?

couple easy things to do are run higher octane gas and see if it goes away or richen it up to 11.5-12.0 A/F(meaning its knock), 12.7A/F I dont think thats good for 10psi and up

gap your plugs down(meaning its spark blow out)

[2K4NightRiderSRT]

Quote: Originally Posted by SpeedEuphoria

whats your plug gap? what gas?sure its not detonation?

couple easy things to do are run higher octane gas and see if it goes away or richen it up to 11.5-12.0 A/F(meaning its knock), 12.7A/F I dont think thats good for 10psi and up

gap your plugs down(meaning its spark blow out)

I forget what the gap is off the top of my head. It's what was recomended for 300+ whp with the NGKs (they are the recomended NGKs for Stage 3R). I'll check em and gap them down to test.

I can try both, richen and higher octane. I can get 94 oct Sunoco here... and I'll try richening it too with the 93 that's in there now.

I really can't say if it's knock or not cause my exhaust is so damn loud. My exhaust consist of a 3" O2 housing and a 3" down-pipe... and that's it. So my exhause ends right underneath my shifter and it's loud as shit when this is happening.

I'll try things in this order...
Spark Gap
Richen
Higher octane

[2K4NightRiderSRT]

Iridium NGKs gapped at .033

I know what you're thinking... but they worked flawlessly with the stock turbo all the way up to 21 psi.

Richened it up to 11-12 AFR... same thing.

And I have too much 93 in the tank now for it to be worth putting 94 in. (Plus it's damn near $4/gal for 93 already.) :-/

Any other suggestions?

[SpeedEuphoria]

Quote: Originally Posted by 2K4NightRiderSRT

And I have too much 93 in the tank now for it to be worth putting 94 in. (Plus it's damn near $4/gal for 93 already.) :-/

Any other suggestions?

Dont use 94 octane, get something more potent like 110 or at least 100 to test with, or throw in some octane booster to get to that

I was trying to give you easy things to check/try 1st, like does it do it at higher rpms at that boost level?(if not it would be compressor surge)
What turbo are you running? What exactly does your setup/engine have, mods list including CR

There could be other things involved. But normally it either fuel(wich you can add so your good), air or spark(which could be plugs/wires/gaps/coil/some wiring to the ecu or coil or electrical interference/grounds, ect..
Do you use a knock sensor?

check the wires and coil, what all have you changed from when you had 0 issues?

[2K4NightRiderSRT]

Quote: Originally Posted by SpeedEuphoria

Dont use 94 octane, get something more potent like 110 or at least 100 to test with, or throw in some octane booster to get to that

I was trying to give you easy things to check/try 1st, like does it do it at higher rpms at that boost level?(if not it would be compressor surge)
What turbo are you running? What exactly does your setup/engine have, mods list including CR

There could be other things involved. But normally it either fuel(wich you can add so your good), air or spark(which could be plugs/wires/gaps/coil/some wiring to the ecu or coil or electrical interference/grounds, ect..
Do you use a knock sensor?

check the wires and coil, what all have you changed from when you had 0 issues?

I know where I can get some turbo blue around here. I'll try that later.

It doesn't seem to matter what RPM. I'm running a 50 trim on the stock block, heads and cams. Hard pipes, LFMIC, MBC, 3" O2 & DP (and no more exhaust after that), 3" CAI, BOV mounted by throttle body, 38mm WG.

Knock sensor is still connected to stock ECU. I would have to clear it before I check it for codes because I haven't messed with it since I've installed MS.

I've read on the .org that it's likely my VB921's aren't giving me enough dwell to fire the mix at that Kpa. I've bumbed up my dwell, and it's a little smoother; but the problem is not gone.

[SpeedEuphoria]

post your timing map up over on neons.org

[2K4NightRiderSRT]

I'll post it on the other .org...

I've only boosted to 21 psi on my MS1 unit... which, also had VB921s. But it was also rough past 10 psi and it wasn't consistent. I honestly don't remember what spark map I was using at the time because I was testing a lot of different things out. I thought then it was because I hadn't spent a lot of time tuning because I knew I was going to use MS2.

Now that I think about it, the MSQ I posted on boost's site was the last MS1 MSQ I used, and I could boost that high.... but it would also break up. Not as bad as my MS2 does, though.

Lets continue this post on the other org...