Over boost cutting in?
 

Alright so I took my 95 running MS1 as a standalone, for its maiden voyage today. I made a set of mechanical det can headphones to hear for pinging and bought the full version of TS to use VE analize. So the majority of the day was spent driving around town in cruise, which the car does very well. It will roll into boost just fine but when I tried to really roll into it hard it would accelerate and begin a bucking followed by what the wideband read as 22.4. I look at my over boost protection and it was set to 7.5 psi, my wastegate is at 8 so believe that to be the problem. I always thought it cut spark and not fuel? although wouldn't 22.4 be too lean to run? afr's seem good rolling in, injectors are 440cc wrx's, ill look through my log to see if I can find the section of hard accel.

don't have the full log viewer yet :( here's the tune, also do my afr tables look rich in the cruise area? I'm new to this and far from experienced, the basemap is from an MS1 pnp

yes.

change it to spark cut and 3 psi or so above your target boost.

that's a fantastic suggestion

...that will likely blow his motor

Ve analize was run as well as det can headphones, raised to 9.5 and still cuts, waste gate not opening?

possibly. or you're creeping. what is your setup again.
post complete list of parts

Brain turbo, imported which should probably be done, waste gate read off of comp housing. Ms1 extra, 440cc wrx, taco taco Mani, full 2.5 exhaust

brain turbo? imported?
I'm guessing you're calling the popular t3 chinacharger the "brain" turbo, and I'm guessing "imported" is un-ported.

which is really stupid, and explains the massive creep.

gape that wg before you hurt your engine

Sorry, autocorrect, il pull the turbo and port the WG

Why do you say that? Is spark cut that bad? I thought it was a reasonable suggestion.

spark cut?

that's retarded. Go back to Toyko Drift.

Both or Fuel Only, or Bust.


~3psi above boost target isn't bad, however. MS looks at the trend and if it *thinks* you're going to surpass the boost cut value, it will cut before you get there, so giving yourself a little headroom will prevent it from engaging when you dont want it to.

It's supposed to be there just in case something happens, like your actuator fails, otherwise learn how to tune so you don't have massive boost spikes.

No need to be a dick Brain. I have always been told to use spark cut since you could potentially create a lean situation by cutting fuel.

Now, if that is completely off base then teach me, dont insult me.

If that turbo is not ported at all it probably wants to hit 12+ psi.

LAWL @ "demanding" respect. you gon learn today

how is cutting fuel altogether going to cause a lean situation?

plz explain

or site the mor@n that you got this info from so we can go berate him

if u no haz cats, and a free flowing un-baffled exhaust, sure it's likely fine

I definitely love the sound/effect lol

I know better than to demand respect from here, lol. I am simply saying that you should explain why so we all can learn rather than jumping straight to the insults.

Insult me and teach me, that works for me.

if you cut fuel, you haz no fuel. without fuel, you cannot haz a combustion event. without a combustion even, you haz no lean event.
fuel cut is what like 99.99% of the OEM's use for rev limiter
kthxbi

we tend to get insult-ey when people regurgitate false information without even understanding what they're actually talking about.

...unless you preface it with a disclaimer

consider this: does your miata blow up when you let go of the gas and coast in gear?

In this scenario, not only is no fuel being injected, but your coils are still sparking away as the wheels spin the motor.

Yes, you don't want a lean condition under load. Lean conditions cause increased temperatures that can lead to auto-ignite, and moves the flame-front bringing peak pressures closer to TDC which can lead to knock.

With that being said, cutting fuel is the safest way to cut power to the motor. No Fuel, no Bang. No Bang, No Boom.

As soon as you cut fuel, you're no longer making any power, and the engine is no longer under any load. This is the typical fashion an OE manufacturer will implement a rev limiter or boost limiter.

When you cut spark only, you keep injecting fuel. So again, no bang; there's nothing to ignite the air/fuel mixture. But what happens when you spark again? Shit ignites with a vengeance -- It's loud and destructive. It can damage your turbo, it will kill your cat, and it could lead to bent rods depending where the mixture ignites on the stroke. And there's the possibility you can straight up flood the motor and bend a rod on the compression stroke.


and yes, there's a need to be a dick. that's what i do!

:brain: