Hittin fuel cut at 9psi......Why...?

[TBMSPED]

So I guess I need to get a fuel cut block, and the MSP has been flashed. But I know it is the cut because of the massive shut down of the engine. Has anyone else had this problem?

[03.5YellowMSP]

yeah iget that too. its happens becasue it is getting cold out.

[TBMSPED]

Whats the cold have to due with it? So it wont do it in the summer?

[BremertonMSP]

Originally posted by TBMSPED
Whats the cold have to due with it? So it wont do it in the summer?


Theory is, with the denser air the MAF sees more air at a lower PSI. Once the threshold is reach, fuel/spark cutoff is triggered. That's why you may not see fuel/spark cut at 9psi in the summer.

[TBMSPED]

Do you get around that....get a fuel cut block?

[03.5YellowMSP]

When the air gets cold it becomes more condensed. As the cold air passes through the MAF sensor the ECU tells the car it needs more fuel. If the car can’t put enough fuel in which would cause the motor to lean out. This is when it cuts and causes I sudden lose of power. It is just the ecu trying to protect the motor. FCD will get rid of this cut but you must be careful that you don’t boost too much or it will lean out and then BOOM.

[TBMSPED]

What about putting somthing on there to add more fuel?

[03.5YellowMSP]

A complete stand alone unit would be perfect. Those can be expensice from what I have heard. If you got the cash I would say that would work best. I think there is S.D.S. is a good one.

[turboge]

Or a haltech..... ;)

[t3ase]

Or you could do as many people do and turn the boost down when it gets cold outside to protect the engine/turbo.

[jersey_emt]

Yeah, I was running 9psi for a while, but now it's back to stock because of the fuel cut.

Stock 7 psi at cold temps is almost as fast as 9 psi in warm/hot temps.

[t3ase]

exactly

[spoolup]

So what if you got bigger injectors.....will that stop it from leaning out?

[Jeph]

You can't just add bigger injectors, you'd need a way to control them. Your ECU isn't going to know what to do if you just add bigger injectors. A piggyback, or Standalone is the only way to go if you don't want to hit the "spark cut"
I think Perf stated there was no such thing as a fuel cut, and it was caused by the MAF being maxed out. Too much air...

[Dexter]

why would you want to CUT fuel. that makes LEAN. that means YOURE FUCKED. :rolleyes:

[Jeph]

Hence the "there is no fuel cut" comment :)

[vodapas77]

So any guidance on running a FCD? I got Joe P's and his MBC. I live in Hawaii so I don't have to worry about the cold. How much boost can I run on a flashed car with an FCD before I start running into the danger zone? I want to spike at 12 and then down to 10-11 psi range. Is this safe in constantly warm weather or too high?

[MazdaDryvr]

If I turn the MBC all the way closed will that return things to stock boost or will that shut the boost off completely?

[azian6er]

^ it will be stock boost

[MazdaDryvr]

you are 100% certain? :)

[jersey_emt]

All the way closed would be infinite boost....if air can't get through it to the wastegate actuator, the wastegate would never open. It would boost until the motor blows.

All the way open will NOT be stock boost, it will be higher. My boost is 7psi stock, and 8.5psi with the MBC at the lowest setting.

The MBC is a restriction in the line...just having it will up the boost a bit.

[kwiktsi]

Originally posted by TBMSPED
Whats the cold have to due with it? So it wont do it in the summer?

Man, either no one ever pays attention or there are a bunch of newbs in recent months :).. The car does NOT cut based on PSI, it cuts based on airflow vs. load, RPM, etc. When the air is colder, it is denser- therefore, more air gets counted by the MAF at the same PSI and you will fuel cut. It is nothing screwy or special about the MSP, it is pretty much typical of most turbo cars.

I have told everyone this since Summer, but noooo, their MSP's were all different from the rest because they didn't fuel cut :D lol.. Anyway, that is your explination, hope it helps.
Joe

[kwiktsi]

Originally posted by 03.5YellowMSP
When the air gets cold it becomes more condensed. As the cold air passes through the MAF sensor the ECU tells the car it needs more fuel. If the car can’t put enough fuel in which would cause the motor to lean out. This is when it cuts and causes I sudden lose of power. It is just the ecu trying to protect the motor. FCD will get rid of this cut but you must be careful that you don’t boost too much or it will lean out and then BOOM.

In theory, you are right- but I dont think an MSP owner would EVER have to worry about leaning out with the stock ECU- flashed or not :).
Joe

[vodapas77]

Originally posted by kwiktsi
In theory, you are right- but I dont think an MSP owner would EVER have to worry about leaning out with the stock ECU- flashed or not :).
Joe

That's for sure, mine is flashed and still spits fuel vapor out the exhaust so bad that it gathers on the tip. Mmmmm rich!

[MazdaDryvr]

Joe! you can answer this! If I turn the MBC all the way closed is that just back to stock level or will that turn the boost off completely? I'm hitting the cutoff too much these days.

[igdrasil]

Im hitting this "fuel cut" also, doesnt matter if im 6-7-8 or 9psi it will loose power and go lean @ 6krpms when enough load is present, that means, in 3rd or over gears, sometimes in 2nd gear...how can we get rid of this?

[kwiktsi]

Originally posted by MazdaDryvr
Joe! you can answer this! If I turn the MBC all the way closed is that just back to stock level or will that turn the boost off completely? I'm hitting the cutoff too much these days.

There is no way to turn the boost off completely or even below factory levels. Other than that, the MBC itself being a restriction will still increase boost 1-2 psi even when it is wide open. I saw someone else answered this and they were right, so I didn't bother :). Let meknow if you have any other questions. Later.
Joe

[jersey_emt]

Originally posted by MazdaDryvr
Joe! you can answer this! If I turn the MBC all the way closed is that just back to stock level or will that turn the boost off completely? I'm hitting the cutoff too much these days.

I already answered your question a few posts above.

You can't go less than stock boost with an MBC, and simply having the MBC installed will increase boost a bit.

Even at the lowest setting (on either the JoeP or the TurboXS MBC's) I hit fuel cut when it's cold enough (under 40 degrees or so) @ high RPM's in the higher gears.

I've taken off my MBC for the winter...the car pulls about as hard at stock boost in cold weather than slightly upped boost in warm weather.

[1FASTMP5]

joe i got a qiuck ? for ya...your fpr what does it bring the a/f ratio's
on the msp's to? i know it leans them out...but how much... and is it consistant a/f ratio's?

[DocBoom]

I have the JoeP MBC its essentially wide open (without having the valve control completely removed) and it doesnt drop lower than a little over 9psi with a spike hitting around 10...Now I hit the fuel cut today for the first time....and the second and third time for that matter...I am thinking that I would like to revert back to the original set up (i.e no MBC) for the winter. There is one problem with that however, which is that the original hoses are pretty brittle, and well, I split them....which I suppose leads me to a question, being; what are the exact specs of the original hoses? I need to have some work done by mazda and I am concerned about them seeing a different hose on there, putting 2 and 2 together and voiding my warranty:)

Oh and by the way this is my first post...I have searched and been following the forum for about a month now...and...ya....welcome to me. Um, thanks, bye....I hope that wasn't too long winded:) .....stopping....post.....nnnnnow.

[jersey_emt]

Originally posted by DocBoom
I have the JoeP MBC its essentially wide open (without having the valve control completely removed) and it doesnt drop lower than a little over 9psi with a spike hitting around 10...Now I hit the fuel cut today for the first time....and the second and third time for that matter...I am thinking that I would like to revert back to the original set up (i.e no MBC) for the winter. There is one problem with that however, which is that the original hoses are pretty brittle, and well, I split them....which I suppose leads me to a question, being; what are the exact specs of the original hoses? I need to have some work done by mazda and I am concerned about them seeing a different hose on there, putting 2 and 2 together and voiding my warranty:)

Oh and by the way this is my first post...I have searched and been following the forum for about a month now...and...ya....welcome to me. Um, thanks, bye....I hope that wasn't too long winded:) .....stopping....post.....nnnnnow.

I'm replacing all of my vacuum hoses with colored hose for 'show purposes.' They can't void the warranty because you replaced some hoses... :)

[DocBoom]

Cheers, I appreciate that input...sincerely!
are you using 3/16" hose? and does this amount of boost on a open MBC seem high to you? Assuming that it is not caused by a leak (which i doubt that it is) is there any thing that i can do to drop it down? I am looking to boost at about 8psi.

[kwiktsi]

Originally posted by 1FASTMP5
joe i got a qiuck ? for ya...your fpr what does it bring the a/f ratio's
on the msp's to? i know it leans them out...but how much... and is it consistant a/f ratio's?

Mine was 11.2:1 or so on the wide band at 13 psi and 12.0:1 @18 psi (with race fuel). It is as consistent as you can get with the ECU in the car :). Never went lean though.
Joe

[MazdaDryvr]

I already answered your question a few posts above.

No offense jersey, but it never hurts to get a second opinion (especially from the manufacturer) when it comes to something that can have severe effect if done incorrectly. :)

So you guys are saying that even if I turn the MBC all the way back ( counter clockwise) that it will still up the psi? So I'll still hit the cutoff? crap , guess i'll be granny driving all winter. :(

[jersey_emt]

Originally posted by MazdaDryvr
No offense jersey, but it never hurts to get a second opinion (especially from the manufacturer) when it comes to something that can have severe effect if done incorrectly. :)


Of course :) I was just making sure you didn't skip ove my post.

I hit the cut with the MBC turned down all the way when it's cold outside, so I took it off for the winter.

[MazdaDryvr]

oooh, i dont want to go through that. :(

[kwiktsi]

Originally posted by MazdaDryvr
oooh, i dont want to go through that. :(

Fuel Cut Defenser (FCD) :). www.joepmbc.com/mazdaspeed.htm :).
Joe

[MazdaDryvr]

I dont understand well enough what the FCD does. I'm afraid I'll blow my engine. I had the MBC set to peak at about 9-10psi and fall back to steady at 8. Now that the weather is cold I'm hitting cutoff in 2nd gear under boost. So would it be safe to install the FCD and just leave the MBC set where its at?

[TBMSPED]

Issues, I just put a boost contrller on mine and its hitting the cut left and right, can that hurt the engine?

[kwiktsi]

Both of you guys need the Fuel Cut Defenser. I am having a sale on them now- $50 shipped instead of the usual $60 shipped. *IF* you leave the boost where it is now, you will be fine- just don't turn it up "just because you can" once the FCD is installed, you will blow it up :).. The FCD is really recommended for experienced tuners for that reason- if you turn the boost up too much, you can blow your motor. If you respect the fact that just because it will allow you to run more boost, you really *can't*, you will be fine :). Let me know if you have any questions.
Joe
PS- No, it really won't hurt the motor, but it is not the best for things either- the sudden shock on the drivetrain, etc. However, I have never seen any damaged actually caused by fuel cut. It is just senseless to run it like that- it is kind of defeating the idea of a performance car if you can't use it's performance :)

[MazdaDryvr]

Is the FCD a discreet item? Something that the dealer wont see on service trips? Easy to install? :) I really do hate the damn cutoff.

[kwiktsi]

Originally posted by MazdaDryvr
Is the FCD a discreet item? Something that the dealer wont see on service trips? Easy to install? :) I really do hate the damn cutoff.

Depends on where you mount it, but yes. It only has three wires and a vacuum line- ground, MAF signal (can be tapped down at the ECU or at the MAF) and the vacuum line goes to a boost source- many people just tap their boost gauge line and mount the FCD under the dash somewhere. No one wil ever know it is there :).
Joe

[igdrasil]

so....whats the technology behind the FCD? what does it actually do in terms of voltages and stuff?

[kwiktsi]

Originally posted by igdrasil
so....whats the technology behind the FCD? what does it actually do in terms of voltages and stuff?

It is actually a failry simple device incorporating a boost switch that allows it to cut MAF voltages back while under boost to keep it out of the boost cut range. I was going to make it 100% electronic with throttle and rpm inputs, but that cannot be done in this price range :). It cuts about .5 volts under boost.
Joe

[MazdaDryvr]

so is the reason for the fuel cut the fact that Mazda used a Protege ECU? I'm just trying to understand why it happens and how your FCD works. One guy on the thread seemed to think that supressing the cutoff isnt wise.