Fuel cut or boost cut???

[I`m Batman]

So after I installed TMIC yesterday, I took my car out on a test drive and got boost/fuel cut in 4th gear at a little over 5k rpm. I know people say it's boost cut but is it really boost cut or is it really fuel cut? Both probably happen about the same time, but what is the root cause? Boost or fuel cut? I know at higher RPMs, the car usually run rich at about ~12-13 AF... so it should be boost cut right? It seems like the injectors are OK with putting more than enough fuel in der...

If it's boost cut, will a boost controller take care of that? I don't really want an AP right now.

I just want to ask the experts out there and see what are the possible solutions are besides AP.

BTW, here's the list of mods... SRI, TIP, BPV, Test Pipe, TMIC...

[~Barn~]

Nice. I was getting a similar fuel/boost cut myself, after installing the most basic Stage1 Map on my Cobb the other day.

It was the same feeling of like hitting a rev-limiter (a very abrupt jerking), but it would only happen in 3rd gear (or higher) at WOT. First hit was around ~4000RPM and then as it would continue to accelerate, it would do it another time or two.

4th and 5th gears would show the samy symptoms, but I was haulingass at that point, and had to slow down.

[erod550]

It's the computer seeing you are boosting higher than stock and saying "whoa, we don't want that" and cutting you off.

You can get a "boost cut defender" which will keep the ECU from seeing boost above stock levels, but you have to be very careful with that cause it can't protect you if you spike to really high boost levels. So you'd need a good boost controller plus you'd need a separate boost gauge (since a Dashhawk will no longer read accurate boost) and also a wideband would be a really good idea too. At that point I think it's easier to just get an AP and have the cuts under control plus have more power and the ability to tune the car.

Here's a link to the boost cut defender.
http://www.jscspeed.com/catalog/Mazda/07_10_Mazdaspeed3/Turbos_Turbo_Kits/ATP_Boost_Cut_Defender_for_07_10_Mazdaspeed3.html

[tbot]

if you're running 12-13 afr's at that rpm than you're getting fuel cut. Basically the fuel psi is dropping lower than what can supply the needed amount of fuel. I doubt its boost cut. Monitor ur fuel pressure (should be >1650) and your boost...that should tell you which cut your getting, but my guess is fuel since your running REALLY lean (should be 11's)

[tbot]

Nice. I was getting a similar fuel/boost cut myself, after installing the most basic Stage1 Map on my Cobb the other day.

It was the same feeling of like hitting a rev-limiter (a very abrupt jerking), but it would only happen in 3rd gear (or higher) at WOT. First hit was around ~4000RPM and then as it would continue to accelerate, it would do it another time or two.

4th and 5th gears would show the samy symptoms, but I was haulingass at that point, and had to slow down.

Barn lets meet up sometime soon...this weekend maybe and get you taken care of. I can bring my laptop and get you a base tune that will get you going at least.

[~Barn~]

I'm down for that, 'Bot. I got my first round of data-logging done, to figure out how my fuel-trims are. Hopefully I'm monitoring enough variables to be helpful.

I'm still waiting to get an email from Cobb, with instructions to get ATR downloaded. They say that they've received my request, and I'm waiting on them now.

[erod550]

Just got an email that they are doing maintenance on the ATR download servers starting tomorrow through Monday so hopefully you get the email before then, otherwise you won't get it until next week.

[~Barn~]

Thanks for the heads-up. I'm not gonna hold my breath, but we'll see!

[I`m Batman]

if you're running 12-13 afr's at that rpm than you're getting fuel cut. Basically the fuel psi is dropping lower than what can supply the needed amount of fuel. I doubt its boost cut. Monitor ur fuel pressure (should be >1650) and your boost...that should tell you which cut your getting, but my guess is fuel since your running REALLY lean (should be 11's)

Isn't 12-13 is rich? ~ 14.xx air to 1 fuel is optimal right? So, 12 or 13 air to 1 fuel would be rich not lean.

My car has always run around 13-14 psi. I see peak of 18-19 psi (from 16) after I changed my plugs to Denso and the hesitation in high gears under load is gone.

[tbot]

i guess it depends if ur running WOT or not...stoich (14.5ish) is part throttle...11's is wot

[tbot]

Isn't 12-13 is rich? ~ 14.xx air to 1 fuel is optimal right? So, 12 or 13 air to 1 fuel would be rich not lean.

My car has always run around 13-14 psi. I see peak of 18-19 psi (from 16) after I changed my plugs to Denso and the hesitation in high gears under load is gone.

that basically means u got rid of KR w/ the Denso plugs which is what the hesitation would be, so a good thing.

still need to clarify tho if those AFR's are WOT or part throttle.

[erod550]

Yea 14s are optimal for gas mileage purposes when you're just cruising and there's little load on the engine. You don't want 14s when you're hard on the throttle. Rich when you're WOT is 10s and lower. Like tbot said you want 11s optimally when you are WOT.

[rmeeker13]

I'm down for that, 'Bot. I got my first round of data-logging done, to figure out how my fuel-trims are. Hopefully I'm monitoring enough variables to be helpful.

I'm still waiting to get an email from Cobb, with instructions to get ATR downloaded. They say that they've received my request, and I'm waiting on them now.

It takes almost 24hrs to get the email...ive done it a few times!

[rmeeker13]

So after I installed TMIC yesterday, I took my car out on a test drive and got boost/fuel cut in 4th gear at a little over 5k rpm. I know people say it's boost cut but is it really boost cut or is it really fuel cut? Both probably happen about the same time, but what is the root cause? Boost or fuel cut? I know at higher RPMs, the car usually run rich at about ~12-13 AF... so it should be boost cut right? It seems like the injectors are OK with putting more than enough fuel in der...

If it's boost cut, will a boost controller take care of that? I don't really want an AP right now.

I just want to ask the experts out there and see what are the possible solutions are besides AP.

BTW, here's the list of mods... SRI, TIP, BPV, Test Pipe, TMIC...

I ran a map clamp for awhile and it worked awesome...you really have to monitor ur shit because ur removing the failsafe of overboosting.
The clamp allows u to trick the ecu so it doesn't see the actuall engine load. I never had any issues untill i added a MBC...then it was a little tricky.

[~Barn~]

It takes almost 24hrs to get the email...ive done it a few times!

WOO HOO! Got my link emailed to me. Time to start fiddling with shit I have no clue about!