Ok here is my problem, I am hitting over boost fuel cut it is killng my fun, and the life of my motor. Now at first I thought hey get the FCD and the problem will go away, now I think that it will only make things worse....all I want is to stop fuel cut and run about 8 pounds of boost. how do I keep my ecu dumping in the right amount of gas if it is being told it only needs fuel for 5.5 pounds, I am lost with how the fcd will help, it only makes the leaning out of the rotors happen to both instead of only the rear one right? I want my car to stop jerking and run 8 pounds of boost, it make no sense to have to upgrade my injectors or my fuel pump for such low boost increase, or does it really need all that? all in all my question is how the hell do I stop rear rotor fuel cut and not lean out my motor???

thanks marty

 

you need to lose the giant downpipe or port your wastegate. your car naturally wants to run more than 8 pounds of boost, and unless you port your wastegate it will. the fuel cut is a safety feature that cuts fuel (slows down the engine) when it goes to 8 pounds, getting rid of it will only make you run even more boost, which is BAD.

 

Ok I am lost, so the turbo on FC's have no real factory boost levels then right, cause it seems like they just boost until rear fuel cut, then lose boost, then rear fuel cut again. I have a full cat back, and gutted cats so I guess this would make my turbo over boost right, the stock turbo gauge is reading at the 40+ mmgs or what ever the stock one read( it is maxing out). So I need to port my wastegate, then what it will on ly boost to 5.5, how do I controll my boost if the turbo does what it wants to do, my 3000GT vr-4 has its boost controlled by the ecu so with out a boost controller it never changes, why is that not the case with my FC, I guess I am just irritated with the whole problem. I have not been able to drive this car without this rear fuel cut the car is no fun when I can't really drive it. what I need to know is how do I fix my boost creep, yet retain the abilty to get a boost controller and boost to 8 psi? I imagine port the waste gate but is there more?

 

http://fc3spro.com/TECH/FAQ/fuelcut.html

is this article REted says that the FCD will fix my problem without hurting my fuel mixture, cause my fuel delivery is determined by my airflow meter, is this about right?

 

Port the wastegate, AND get a FCD. The FCD fools the computer into thinking you are running less boost than you actually are. In order to do it safely you will at least need to upgrade your fuel pump (walbro 255, they are all over ebay). As far as keeping it right at 8psi, im not sure what to tell you. It might depend on how much you port the wastegate, but im not sure. I have complete turbo-back exhaust and a street port, and i boost to 10psi on the ported wastgate, which is fine with me as long as i have the fuel mods to support it.

 

so is there no way to control the boost?
cause a boost controller never lowers boost it can only up it (in other words if your turbo is stock running at 5.5 psi you can't make the turbo go down to 2psi only make it go past 5.5 psi) I want to control my boost levels and it sounds like the factory turbo won't let you control its boost levels.

 

how much did you port your wastegate?
and what gaskets need to be replaced?

 

external wastegate setup would relieve the extra pressure.

You would have to cut the stock wastegate "hole" quite a bit depending on results you achieve, this woudl also include welding on a larger washer to make up for the larger "hole"

 

Ok well here's my setup, right now I have stock down pipe and stock cat (but all cats have been gutted, a full cat back that is 2.5 inch back dual exhaust, a ram air intake and thats it.

So what I want to know is, how do I get my car to boost at 8psi and never go above that unless I tell it to with a boost controller?

in a month I plan on getting this turbo upgrade http://www.rx7store.net/product_p/bn...-88%20stg1.htm
will this fix my boost creep problem with its 30mm wastegate?

 

hmm do you know what size the stock wastegate is?

the only options are external wastegate OR a more suitable wastegate.

I think a 30mm then ported nice and clean should give you the results you are after.

 

Well honestly im in over my head, but you are right on about the boost controller only increasing boost and not decreasing it. So if you could port your wastegate enough to make it naturally boost around stock boost levels and then add a boost controller to increase it to 8psi it seems like that would work.

Oh and i dont know how much my wastegate is ported-im not the one who did it.

 

the fcd will trick the ecu into running more boost by telling it that it is running less boost than it really is so i dont think its gonna help ur problem much, i dunno. i think a new fuel pump would help but other than that im pretty stumped. its not like ur hittin fuel cut because of ur downpipe so its probably ur wastegate. tial wastegates=mucho good

 

well just bought a new fuel pump ( walbro 255 ) and new injectors (720cc for my secondaries) plus the new FCD.....who wants to place bets on how long the stock turbo will hold up if I let it boost to its little hearts content?

and when I get my tax return I am getting the stage 1 turbo upgrade so this turbo can die!!!!!

 

^ i would be more worried about your motor than your turbo, but since you got the fuel mods it should be ok. Do you have any way to tune it?

 

lol it was more a joke than anything I am going to go about this very carefully cause my motor only has 15,000 miles on a factory motor (replaced with new factory motor by mazda dealership), so yeah what would you recomend for fuel tuning?

 

well everyone says that a standalone is much better, but i have a SAFC2 that i just installed, but i havent started tuning with it yet. A piggyback like the SAFC is cheaper and probably easier to use and it should work just fine.
Im new to this tuning thing so im learning along with you.

 

to understand the problem better, read this:
http://fc3spro.com/TECH/FAQ/bcreep.html

you cant put an aftermarket wastegate on the stock turbo/manifold. if you want to lower boost you have essentially TWO options: put the restrictive stock intake and exhaust back on or port the waste gate to bleed off enough air that the turbo doesnt overboost.

as far as how much boost a stock ecu/fuel system can handle, i have no idea. 8 psi is PROBABLY safe but i havent ever wasted my time with the stock ecu so i wouldnt know for sure. im not seeing how a fuel pump by itself will do anything, but a combination of 720's with a walbro is a step in the right direction. however, you need something to control these injectors. the stock ecu wont know you have 720cc injectors, and will continue to send the same signal to the injectors as it would if they were the stock 550cc injectors. this isnt tuned in anyway and will lead to super rich conditions which rob power. you have to use an SAFC or some other piggyback to alter fuel delivery, but even these have their limits. turning up the boost isnt cheap or easy on these cars, and its also very dangerous. do your research before you blow some **** up. good luck.

 

my final goal is 280 rwhp, now I understand that these cars are not easy to tune but I was told that with a turbo-back exhuast, cold air intake, FCD, 255 walbro fuelpump, 720cc scondaries, ported wastegate, and the stock turbo boosting at 10 psi should give me about 280 to the rear wheels that sound about right?

 

thats pretty much exactly what im running, AND i have a street port, and i seriously doubt im running 280 at the wheels. I have not been to a dyno though.

edit: oh wait, mine is more of a hot air intake than anything

 

yeah, no kidding. thats strange though, 280 is my goal also.
right now my ecu is being done by rtek. i put 750ccs in last night. i have full turbo back, intake, light weight flywheel, and rx7.com bosch fuel pump.
my next step is safc2, hallman boost controller, and then on to a bnr stage 2 or 3.
so, similar mods, im also hoping for the same power as you, but i also doubt im near 280 without the turbo upgrade.

 

so without the turbo up grade 280 doesn't sound right? well another thing I was wondering was does the BNR stage 1,2,and 3 bolt to the stock manifolds of do you need to need to order a new setup? also do you really need to go to stage 2 or 3 to reach 280 rwhp when RX7store says that stage 1 makes 300 - 310 rwhp at 15 psi?

thanks marty

 

also is a 30mm port for the wastegate a good size?

 

id go by whatever BNR @BNRturbos.com says....i dont know the limits of his turbos...BUT, if your just looking at 8LBS. of boost...install the fuel pump, 720's and buy my Rtek 1.7 (assuming its a S4).
port the hell outta your wastegate, and get a manual boost controller and a boost guage...then you can boost to 10 LBS. safely and have fun with NO fuel cut!


**edit**
when i ported my wastegate, i just ported it all the way to the very edge of the lip the flapper catches on...just enough room to keep a seal on it....then you wont have to worry!

 

Untill you get things sorted out, port the wastegate or make your exhaust more restrictive. Do you have an intake? If you do, put the stock one back on. Do a fuel pump rewire and put in a FCD. You need to know how much your boosting so you may be wise to buy some kind of boost gauge.

If you want a stand alone ECU, Megasquirts are inexpensive.

You are not going to make 280rwhp with the stock turbo. I've seen dynos of people making close to that range at the flywheel with S5 engines. Why did you decide on that specific number?

Keep in mind that typically when the stock turbo boost higher, it typically responds earlier in the rev range and it will respond more with less load. Many believe that the way that a lot of people blow their engines is by running lean before the secondaries kick in. The stock ECU doesn't drive the primary injectors very aggressively. Thus if you are making much more boost than stock before 3800rpm, there is not enough fuel. I've seen dynos where the A/F ratio goes very lean just before the secondaries kick in.

The above mentioned RTech lowers the transition point where the secondaries kick in by a few hundred RPMs, but it stands to reason that fuel economy will suffer on the highway (no closed loop with the secondaries).

 

thats how my previous project blew up