isnt the only thing a fcd does is say that less boost is coming in then there actually is. why not put a boost contoller inline with the vaccum line, wouldnt it be the same just mechanical instead of electrical?

 

i thought the fcd keeps the enigine from stoping fuel to the resr rotor, if you just do a boost controller youll get a fuel cut at 10psi i think, then pop goes your motor

 

Your stock ecu limits your boost aka a fuel cut preventing you boost over the safe limit. Putting a boost controller in will not prevent fuel cut, and you will hit the fuel cut thus you can not boost over 8psi +/-

 

The only way to NOT hit the fuel cut is to: A) install an FCD of some sort or B) not hit boost any higher than 8psi.

A boost controller controls the wastegate by, basically, telling the wastegate how much exhaust to bypass the turbo. Now once the wastegate is all the way open, bypasing as much exhaust as possible it's at its end. If you should by chance still be hitting over 8psi you'll get fuel cut.





P.S. your motor will NOT go "Pop!" if you hit the boost cut. Running lean is different then not having any fuel!

 

This is slightly confusing. does the ecu take the boost reading and use it to increase the amount of fuel due to increased boost? if so then wouldnt a FCD be very dangeous.

I have a FCD and run 11psi daily.

Or is the boost sensor only there to enable the fuel cut system? and hense by using a FCD all you are doing is tricking the system and the ECU gets all the air flow/boost info from the AFM.

 

Yes, the ecu will increase the amount of fuel depending on the boost that is read at the boost sensor. Now to you second thought, yes, a FCD is dangerous as the ecu believes the boost is a lot less than it actually might be. This is why guys will put in larger secondaries, more fuel even though the cycle time is the same as the 550's. Don't forget a larger pump.

 

Boy, there is so many things wrong with this reply...

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


-Ted

 

so how much more retarding of the ignition timing would/should happen after 6.5 psi ( i have a S4 ecu ). clearly if im running 11psi without any additonal ignition retarding im not running to the optimum.
how does this work if your running 12-14psi with a SAFC and you have tricked the ecu signal from the AFM into thinking your only running 5psi?

 

well suposidly the ecu retards the timing around 1 deg per psi.... so every psi past the fcd clame psi, ( ussually around 7-8) is one deg off.

well the rtek ecus eliminiates the code for fuel cut, and allows timing to keep retarding

 

i think the OP means running a boost controller in line to the boost sensor, if this is the case then 1) a boost controller is more expensive than a FCD and 2) a boost controller changes the airflow linearly, unlike a FCD which tapers off near the peak so the pattern is close to a normal boost level that the ECU sees until just before it would hit boost cut level the FCD holds the voltage level at a cieling before it does.

 

So the pressure sensor is there for timing retarding NOT fuel compensation?

So why not save a couple bucks and just unplug the sensor?!

 

The AFM measures airflow, not boost. Tricking the ECU into thinking there's less airflow results in less fuel injected and less ignition retard under boost, both of which lower resistance to detonation. This is the biggest disadvantage of interceptors, but like anything it's just a case of not pushing it far enough to cause detonation. CAI's and FMIC's lower temps which increases resistance to detonation, so you can get some extra safety there.

Of course If you're using an interceptor to increase fuel then the opposite occurs: greater ignition retard under boost and higher resistance to detonation.

Because then the ignition timing would be overly retarded when not in boost and not retaeded enough when on boost. That would be bad...

 

As I understand it, the fuel maps in the ECU only go up (WRT boost) so far,and as a countermeasure for running out of fuel maps the car hits fuel cut. Any tricking of the ECU (as far as boost) is only going to lean out the motor (unless you are running something to control fuel: IE SAFC). I don't like FCDs alone. If you are going to use an FCD you need more fuel. I suggest an SAFC. OR you could always get an EMS, or my preference: RTEK. I could be completely off the rocker, but I as well as many others, is learning, so I just run searches and post once in a blue moon.

Edit: Yes, I am dumb. So an FCD only blocks the signal from the boost sensor, and thus only limits the changes to timing? Wow I learned something tonight. Too bad I plan to run 4x720cc Inj, and an RTEK with a BNR stage 3 (plus others). I thought that in addition to timing, the boost sensor also added fuel with respect to PSI.

 

the ECU is mapped quite a ways beyond the stock limitations, the boost cut is incorporated for the sole purpose to tell the driver there is a problem. when a stock set up car hits fuel cut the only reason for it would be a failure within the wastegate actuation system in which case the factory fuel cut is there to save the engine from overboosting beyond what the factory fuel system can protect the engine to.

 

^^awesome post Karack.

 

well if they really were smart they would have put a code in the ECU for when the ECU does have to fuel cut then it would have a code stored but then again these ECUs don't store codes so that is irrelevant. i hate dealing with archaic electronics.

 

Quote:
Originally Posted by Turbonut
Yes, the ecu will increase the amount of fuel depending on the boost that is read at the boost sensor. Now to you second thought, yes, a FCD is dangerous as the ecu believes the boost is a lot less than it actually might be. This is why guys will put in larger secondaries, more fuel even though the cycle time is the same as the 550's. Don't forget a larger pump


Well Ted, I did read your information and still feel that the pressure sensor is utilized not only for timing, but fuel regulations during certain throttle operations as the ECU needs to calculate mixture accordingly. In your article it's stated that the AFM is primary, but no info as to what might be secondary. Certainly the timing is going to be incorrect at 11/12 lbs with an FCD so that's why I suggested larger injectors to ensure fuel supply as the timing isn't retarded significantly.

Jason also belives the MAP is instumental in controlling the mixture:
Many EFI systems that use an airflow meter as the primary load sensor also use the MAP sensor as a secondary load input. It reacts much faster than the AFM (or more correctly, the manifold pressure changes quicker than the airflow does), so it's useful for transient corrections, like rapid throttle movements

Hailers:
According to the 89fsms Relationship Chart, it effects: Lead and Trail timing, etc, and the fuel injection amount.

Not starting a war, but don't feel I was that far off base.

 

just FYI, the stock timing maps (as shown on rtek 2.0) show timing advance to ~35 degrees at max load (usually approx ~7psi). Which means the timing will be usually ~35 degrees advanced at boost above ~7psi.. (i know this isnt true under all circumstances, b/c load isnt directly connected to boost, so dont be this post). That is a lot of advance for the amount of boost people usually run with FCD's, especially with overheated turbo and IC. I think that maybe why 7's are notorious for blowing up when not properly modded

 

I really don't care what you feel.
Paul Ko proved this on the test bench, and it's been confirmed by Henrik (of the RTEK guys?) that this is so.
At about 2psi of positive boost, the boost sensor has NO BEARING ON FUEL DELIVERY.
You can go search for the reference, but it has been proven...regardless of how you feel, period.


I really don't care.
I run a Haltech E8 on my car, and information like that does not help me in any way.


What does changing the fuel delivery (adding more fuel?) have anything to do with incorrect ignition timing?


I really don't care what Jason says; he's wrong.
See above.

Reread what I just said above.

Reread what I just said above.
You need to do your research before making such claims, cause your reply isn't exactly true either.


-Ted

 

Um, are you sure you're translating the information correctly?
You're posting some very DANGEROUS information there.

From my experience, the Mazda ignition timing should've be going over 17 or 18 degrees total advance under load!


-Ted

 

Wouldn't 35 degrees retarded fire the plugs during the start of a compression stroke? That seems like some massive timing...........

 

~35 degrees is what the rtek 2.0 timing map defaults to at 100% load, <~5000rpm, about 15.5 degrees split. the rtek guys say this is the stock map, but you may want to confirm that with one of them (henrik?)

 

so if you ran a full standalone would you still get boost cut?

 

all these numbers are getting abit crazy.

the question i have, relates to how important is timing to boost level.
dont just say " its very important" coz we all know that

so far we have establised, c/- Ted that the boost senor is not used to increase fuel due to increased boost levels, but to monitor boost levels and advance/retard the timing acordingly.

Now there have been 2 claims here.

1: at 7psi ( max load ) timing is advanced by 35deg

2: under load the timing advanced to a max of 17-18degrees.
Ted, are you say what you think it should have been, or, should be/is?


now for my questions ( there was gona be one, but now theres more )

1: if the max load is at 7psi then, does the boost sensor only read to 7psi ( S4), at which point it would trigger a fuel cut?

2: does the timing advance or retard under boost? as the above states it advances, but even further up it says it retards. some clarification please.

3: if the timing stops advancing or retarding at 7psi ( due to the FCD ) how critical is the timing at 11psi?,

4: if the ecu retards 1 deg to 1psi then in advanced 4deg to much at 11psi, i take it 4 deg is not overly critical?

 

not to degrade the Rtek guys too much but i think they fucked up when they loaded the stock map, i already had to replace one motor that the Rtek 2.0 destroyed so i took a look at the timing map and it was SEVERELY advanced and would cause pre-ignition and is almost without a reasonable doubt why his motor popped after just a few full boost runs. so far things are getting ironed out but in my opinion you can't trust what was originally loaded into the Rtek because it was not ready for distribution yet and you are the test subjects for the product.

if it truly is the stock map then it should have been analyzed and refined prior to release, i found a similar issue with the microtech base maps where the total ignition timing was borderline unsafe at 18* of advance under HARD boosting situations, 18* is still too far advanced so you can just get an idea of how far 35* is of advance when you start pushing 13+PSI of boost..