can someone tell me the diff between boost cut and fuel cut, by the feeling

M

Munnugles

Member
:
2008 Mazdaspeed 3
so yesturday, i was driving around and i hit the gas, i was in second, i started peeling out, bov goes psshh, and then all of a sudden the car jerks foward a bit, (im still flooring it) and my bov goes off again and im still going pretty much, scared the crap outa me when it jerked and im thinking to myslef boost/fuel cut... i dont have a boost guage installed yet so i couldnt really tell...
so my main question is how do i know which one it is... this is the first time its happened, and i cant really do it again...
mods: trz poly, twm bushings, ets 3.25, hks bov, ms cai... stock tires/rims/suspension
ive searched but i cant figure out how to tell the diff
 
Seem like ur still pretty much running stock boost,even with the few mods u did..check ur hoses make sure they are all tight..IC hoses, cia hoses etc..
 
yea lol go hop in a msp and have fuel cut vs boost cut. fuel cut feels liek you hit a brick wall and you almost launch out of your seat lol
 
Rode in a turboback+intake MS3 last night, kept hitting fuel cut. It feels like you are WOT, and then tap the brakes, then WOT, then brakes. Another MS3 that was with us said it looked and sounded like we just kept slow shifting.
 
Sierra117 said:
Rode in a turboback+intake MS3 last night, kept hitting fuel cut. It feels like you are WOT, and then tap the brakes, then WOT, then brakes. Another MS3 that was with us said it looked and sounded like we just kept slow shifting.
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.......that my friend is boost cut, not fuel cut.......once you fuel cut once you'll know the difference.
 
JSpeed 6 JLA said:
.......that my friend is boost cut, not fuel cut.......once you fuel cut once you'll know the difference.
Click to expand...

Yeah, I typed fuel cut, when I was thinking boost cut. No sleep, yesterday was a long day, and I was thinking about the CDFP I'll be installing tonight. Or should be, at least.
 
If you heard your BOV blow off while floored its because the ECU closed the throttle plate. So in essence that is boost cut but the ECU does so by modulating the throttle and not cutting back on fuel like fuel cut.
 
i have experienced both types several times on my car and always thought they felt the same. going, going, going..... fall on its face.......going, going, .
i could never tell the differance. i had boost cut until i added the MAP clamp. after the map clamp i got fuel cut in cold temps. felt the same to me.
 
interesting... so im guessing i hit boost cut?... it did feel like it slamed on the brakes. and let go right after...
 
JSpeed 6 JLA said:
.......that my friend is boost cut, not fuel cut.......once you fuel cut once you'll know the difference.
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No it was definitely fuel cut, he just described it wrong. When he said "tap the brakes," he meant "slam on the brakes." While it's not impossible, I have a hard time believing I got boost cut when I'm still running stock boost levels. And to further convince me, it went away last night when the fuel pump was upgraded.
 
SLS MS3 said:
No it was definitely fuel cut, he just described it wrong. When he said "tap the brakes," he meant "slam on the brakes." While it's not impossible, I have a hard time believing I got boost cut when I'm still running stock boost levels. And to further convince me, it went away last night when the fuel pump was upgraded.
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...you can hit boost cut with while running stock boost levels if your running a FMIC and TBE in 5th and 6th gear. with the better cooling and lack of restrictions the car wants to boost 19. I know this cuase my car is like this now on my speed 6. none the less-all i know is fuel cut is more violent then boost cut, ive experienced both.
 
I just had some sort of "____ cut" today. This is the first time this has ever happened. I just put on my ETS 3.25" TMIC this weekend. Today is was 40 deg F, I was on the freeway in 5th gear at 4k RPMs testing out the power. I went WOT and at about 4500-5000 RPMs, the car jerked violently. It felt like I hit a large dog or something. That's the only way I can describe it. The only noise I heard was what sounded like a loud thud. I think it was the transmission gears slamming back against the engine's loos of power. Which cut was this? I immediately thought "fuel cut", but after reading this, i'm not sure. I can be getting more boost now with the TMIC, but isn't boost cut gradual?

My car pulls a hell of a lot harder now since I added the second gutted cat and TMIC.
 
SLS MS3 said:
No it was definitely fuel cut, he just described it wrong. When he said "tap the brakes," he meant "slam on the brakes." While it's not impossible, I have a hard time believing I got boost cut when I'm still running stock boost levels. And to further convince me, it went away last night when the fuel pump was upgraded.
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It didn't really feel that violent to me when it cut in? I mean, I don't mean tap the brakes like to slow from 65 to 60, but I'm don't think it felt like you hamered them to get from 60 to 0.
 
this may be a stupid observation but since you stated you that your tires were spinning you sure it wasnt the traction control stopping you? cause i have expeirienced that same thing your describing and it was because of the TC.
 
07speed3 said:
this may be a stupid observation but since you stated you that your tires were spinning you sure it wasnt the traction control stopping you? cause i have expeirienced that same thing your describing and it was because of the TC.
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Yes. to me also, a little freaky, really threw me forward during second gear wheelspin. Have kept it in off mode for any speeds less highway driving
 
All I know is that I'm peaking out at 20.5 psi in 4th gear at WOT when quick-shifting from 3rd. Thats what I logged today, but didn't get the cut. I do know that I was only above 20 psi for a little over 100 ms. I wonder what the threshold is and time required above that threshold for the ECU to cut fuel.
 
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