We All Know About Cold Weather Boost Cut, But...

[Alexsered]

I know that it is common knowledge about the cold weather boost cut. My question is why??? Turbo'd engines are supposed to run more effeicent in colder weather, right? If anything, I could understand a boost cut in hotter weather as the turbo's could cook themselves if boosted too hot.

It is noticable in my car, even on the highway, I can just feel that the engine just does not feel as spirited. Why did mazda do this?

P.s. It was around 60 degrees yesterday, compared to the freezing temperatures we have been having for the last month or so, and the car felt so much different.

[Element]

I believe it has to do how colder air is more dense, and thus has more O2 per volume of air. As a result not as much boost is required to make the same amount of HP and TQ. At least thats what happened when I had my SRT4. The ECU would drop the boost as it got colder. Not sure if this is what you are referring to or not.

[Alexsered]

I believe it has to do how colder air is more dense, and thus has more O2 per volume of air. As a result not as much boost is required to make the same amount of HP and TQ. At least thats what happened when I had my SRT4. The ECU would drop the boost as it got colder. Not sure if this is what you are referring to or not.

yeah, it drops boost, but it's a definate power drop to the wheels. I don't even drive the car hard at all during the winter, it's just not as fun.

[Element]

yeah, it drops boost, but it's a definate power drop to the wheels. I don't even drive the car hard at all during the winter, it's just not as fun.

Funny I found that my MS3 really likes the cold weather. I went from +30 to now -30 and have noticed the drop in boost but not a drop in performance. Are you running stock or winter tires?

[AutoEuphoria]

Boost builds up faster with denser air. The ECU can't keep up and regulate it fast enough. That's my understanding anyway.

[Alexsered]

Funny I found that my MS3 really likes the cold weather. I went from +30 to now -30 and have noticed the drop in boost but not a drop in performance. Are you running stock or winter tires?

I'm running some sumitomos, but on the highway, that really shouldn't matter.

You feel like your car likes the cold weather? Man, my speed3 just feels sluggish, even down shifting from 5-4 around 4000 rpms is usually the sweet spot for the highway, but when it's really cold, it feels sluggish with the boost cut. Yesterday my car felt totally different.

I also remember hearing somewhere on one of these threads that people were getting the best times at the track around 70-75 degrees outside.

[opt_ms3]

anything colder I would think it would be hard to get decent traction, unless the sun was out

[Element]

I'm running some sumitomos, but on the highway, that really shouldn't matter.

You feel like your car likes the cold weather? Man, my speed3 just feels sluggish, even down shifting from 5-4 around 4000 rpms is usually the sweet spot for the highway, but when it's really cold, it feels sluggish with the boost cut. Yesterday my car felt totally different.

I also remember hearing somewhere on one of these threads that people were getting the best times at the track around 70-75 degrees outside.

I know my car likes the cold weather. Even my girlfriend notices it. Well tires will definately make a big difference. I am running studded tires and they are awesome on the ice. I can safely say that my car hasnt felt sluggish at all in this cold. The only problem I have is with suspension noise.

[shane02pro5]

It may have to do with the fact that in cold weather with more dense air the fuel system is trying to keep up and the duty cycle is getting high the ecu thinks you're running out of fuel so it pulls timing to keep the engine safe???

I tripped a cel this morning at 33 degrees due to maf high input voltage which is typically triggered from what i mentioned...fuel can't quite keep up.

[wheresthericego]

lol at stock computers that think they know what is best

[NYSP33D3]

I know that it is common knowledge about the cold weather boost cut. My question is why??? Turbo'd engines are supposed to run more effeicent in colder weather, right? If anything, I could understand a boost cut in hotter weather as the turbo's could cook themselves if boosted too hot.

It is noticable in my car, even on the highway, I can just feel that the engine just does not feel as spirited. Why did mazda do this?

P.s. It was around 60 degrees yesterday, compared to the freezing temperatures we have been having for the last month or so, and the car felt so much different.
Just a science Lesson for you.. Cold Air is LESS DENSE then HOT AIR... and your gettting boost cut cause like said earlier boost is building faster then in the warmer air and your hitting boost cut sooner.

[mattj3636]

Just a science Lesson for you.. Cold Air is LESS DENSE then HOT AIR... and your gettting boost cut cause like said earlier boost is building faster then in the warmer air and your hitting boost cut sooner.

wrong. completely.

the colder the air, the more dense the air.

Effect of temperature
°C - kg/m³ (DENSITY)
−10 - 1.342
−5 - 1.317
0 - 1.292
+5 - 1.269
+10 - 1.247
+15 - 1.225
+20 - 1.204
+25 - 1.184
+30 - 1.165

theres a science lesson,

and heres another..

heat rises.
(less dense).

[jazzman]

Just a science Lesson for you.. Cold Air is LESS DENSE then HOT AIR... and your gettting boost cut cause like said earlier boost is building faster then in the warmer air and your hitting boost cut sooner.

I call BS. How do you think hot air balloons work? You have your science lesson backwards.(homework)

[lil_red_wagon]

one thing that everyone is forgetting is that the outside air is cold, but the engine air is warm. the cold air expands as it heats and produces more psi.

[Alexsered]

yes, cold air is more dense, but why would mazda mess with the boost. Let the turbo run better in the cold weather, don't mess with my boost!!!

[Alexsered]

yes, cold air is more dense, but why would mazda mess with the boost. Let the turbo run better in the cold weather, don't mess with my boost!!!

I need more NOS.

[mattj3636]

if you spray to much the screws on the metal floorboard on ur passenger side might explode out and you might lose the metal piece.

so watch out.

oh and its not how you stand by your car, its how you drive it.

oh also, it doesn't matter if you win by an inch or a mile, winnings winning.

[AutoEuphoria]

Cold Air is LESS DENSE then HOT AIR

Fail statement of the year.

And are you people talking about BOOST CUT or BOOST REDUCTION? Boost cut is from boosting more than you're supposed to (stock ECU is set around 18psi) and causes a fairly violent bucking of the car.

[pidass15]

Just a science Lesson for you.. Cold Air is LESS DENSE then HOT AIR... and your gettting boost cut cause like said earlier boost is building faster then in the warmer air and your hitting boost cut sooner.

lol FAIL.

[shane02pro5]

I was going to say go easy on the guy but soooo many threads these days with people throwing insults and calling names it really is rediculous.

Probably from a 17yo kid that just got an MS3 with a bow on it from mommy and daddy and don't even know how to change their damn oil!! Not saying anyone here is one of those people maybe 90% of the insults should be held back!

[magnumP5]

I tripped a cel this morning at 33 degrees due to maf high input voltage
This is exactly what happens. It isn't "boost cut" it's "fuel cut" and it's because the voltage the ECU is receiving from the MAF is too high. I'm not sure about the 3s but Protege MAF max out at 5V. Anything higher than that will trigger fuel cut and if you repeatedly encounter it you will through a CEL as shane has mentioned here. It's what you all have been saying: colder air is denser air. Greater density means more molecules per unit volume. So, for a given amount of flow, there is a larger amount of air passing by the MAF on a colder day than on a hot day. The voltage transmitted by the MAF is directly proportional the amount of air it is reading. So more air means greater voltage. Too much voltage means fuel cut. This can be alleviated through the use of a simple MAF clamp.

[shane02pro5]

My situation might not be quite as typical with my 22psi but I even have a JoeP FCD MAF clamp. If I gently accellerate and once I get to "traction speed" and hit it hard my WB shows a superquick lean spike from the majorly dense air at well over 500cfm makes it kind of hard to react to. It can also happen if I lose traction and hit high boost with less load than normal and I go rich for a second and cel.

This has been the same occassionally even way back at 8psi.

[magnumP5]

^^^ Interesting. I've actually only hit fuel cut once or twice at high RPM in colder temperatures and that's with a relocated MAF (doesn't actually cause anything though)! For your case though I can see where it would be insufficient injector/fuel pump flow in which case fuel really is running out (well, more that it can't respond quickly enough), not getting cut. I wonder if a too-lean condition read by the primary O2 sensor can also trigger fuel cut?

[shane02pro5]

After I got everything tuned near perfect I didn't need the JoeP until after 17psi but i also put in the walbro so...

I'm sure it's a combination of the maf and 02 readings on a stock ecu. Both of my stock 02's are wired to +12v to keep the ecu from complaining since they don't do anything for me using the Haltech.

[rednofive]

I can't tell if I'm seeing cold weather boost cut or something else.

I have a stock 2008 MS3 and I've noticed that sometimes when hot-dogging into something like a traffic circle or a standard 90-degree turn, I'll get no boost at all while in turn.

example, I'll be hard in 3rd gear, then hard on the brakes, heel-and-toe blip into second, turn-in and then squeeze hard on the gas and...
nothing.

then, when I straighten the wheel I'm usually up at 4K RPM and the boost LURCHES on.

This is NOT the LSD limiting traction, this is simply having no real power for the LSD to have to limit.

thing is, it doesn't always do this. sometimes in a traffic circle (that I entered while in 2nd gear already), I can get the wheels to spin and give the LSD one heck of a hard time until I feather and let the front-end re-bite...

thoughts?
I've only really noticed this lately here in Indiana so maybe it is cold-weather related?
or maybe just steering related?
(dunno)

[Alexsered]

I can't tell if I'm seeing cold weather boost cut or something else.

I have a stock 2008 MS3 and I've noticed that sometimes when hot-dogging into something like a traffic circle or a standard 90-degree turn, I'll get no boost at all while in turn.

example, I'll be hard in 3rd gear, then hard on the brakes, heel-and-toe blip into second, turn-in and then squeeze hard on the gas and...
nothing.

then, when I straighten the wheel I'm usually up at 4K RPM and the boost LURCHES on.

This is NOT the LSD limiting traction, this is simply having no real power for the LSD to have to limit.

thing is, it doesn't always do this. sometimes in a traffic circle (that I entered while in 2nd gear already), I can get the wheels to spin and give the LSD one heck of a hard time until I feather and let the front-end re-bite...

thoughts?
I've only really noticed this lately here in Indiana so maybe it is cold-weather related?
or maybe just steering related?
(dunno)

It should always do this, our speed3 actually lower the boost when the steering is turned past a certian degree to limit wheel spin, we get max boost in a straight line, but when turning, you won't get max boost. It's actually a pretty cool feature for street driving, but at the track, I can see how that gets annoying. Does this answer your question?

[rednofive]

It should always do this, our speed3 actually lower the boost when the steering is turned past a certian degree to limit wheel spin, we get max boost in a straight line, but when turning, you won't get max boost. It's actually a pretty cool feature for street driving, but at the track, I can see how that gets annoying. Does this answer your question?

Yeah, thanks!

How did you know that?

I assume they did this to keep us from killing ourselves with hellacious "push"?

[Alexsered]

I remember reading about it when the car was first coming out. It's pretty good because turning the wheel and having all of the power would just cause a FWD to slide.

[rednofive]

I remember reading about it when the car was first coming out. It's pretty good because turning the wheel and having all of the power would just cause a FWD to slide.

I mostly agree, but I'd rather let my foot and the mechanical LSD decide that more than the ECU. I'm not saying that because I think I'm some kind of amazing driver or anything, but it seems like they drew the line in the sand pretty close to the kiddie's sand box.

No boost at all is what it feels like and I have no gauge to confirm that. Its pretty obvious that the car could handle more boost than none while turning, especially with the stock summer tires and an excellent LSD.

What is the boost curve for the MS3 in each gear, BTW? Is there a FAQ on this site for the MS3 that shows me things like that?

thanks again,
Pete