fuel cut controller question
 

A fuel cut controller fools the ECU into believeing there's less boost then there actually is...so, in turn, wouldn't the ECU supply less fuel to the motor?

Yep you need to have a fuel controller to add more fuel with an FCD.

that's what I figured...so an SAFC, A/F meter, and a FCC should be installed together...

There's a number of folk who say the issue is not a lack of fuel delivery with the fuel cut defender. The real issue they say is a timing isssue. The extra fuel is added , according to them , to prevent detonation due to the ECU not retarding the timing (FCD installed, rememeber) as the boost rises. I think that's what they are saying.

can you go into a bit more detail on that? I think I understand what you're saying but I could be mistaken...

The bottom line is that some people say that the fuel delivery is NOT effected by the pressure/boost sensor. They say that the fuel is controlled by the afm and not effected by the pressure/boost sensor.

They say the reason for adding fuel when you boost over the stock boost, is to prevent detonation. They say........

Trust me, you'll be getting some more replies to your question. Hang in there. This will get you back to the top of the list.

Try this site http://www.teamfc3s.org/forum/showth...threadid=21123

Now you can read the whole thing, but as regards your question, read the seventh post by Henrik. It seems to be relevant.

Here, I stole his words and pasted them:
The boost sensor. Its used for a couple of things, so far:
- timing control, but only stepwise. ie not x deg per psi.
- fuel cut on decel, fuel cut on boost (stocker anyways
- control of setting fuel pump on "high"; ie giving it the full +12v
- fuel enrichment. Its starts adding fuel around 0psi and tops out around 1.6psi. How much is also dependant on rpm.

Our experiments show no effect of the boost sensor on fuel delivery.



-Ted

An FCD will not affect fuel delivery. You may need larger injectors and hence a fuel controller depending on how much boost you want to run. General consensus seems to be that you can run 8-9psi on the stock system, beyond that its injectors/pump upgrade time. It all really depends on how close to the edge your comfortable in running. Check out www.pocketlogger.com for the RTek7 chip (built in FCD plus a couple of other features)

I think a lot of people are confusing our cars which have an AFM for airflow with cars that use a MAP sensor for airflow (like the 3rd gen). On those, an FCD will cause the engine to run lean.

RETed:
You need better experiments then. Granted its a narrow window but the stock ECU does add fuel from about 0psi to about 1.6psi. I've seen this in my datalogs as well (although there it extends out to about 3psi, a discrepancy for me to find). You should be able to see this by holding a steady rpm and apply a pressure signal to the boost sensor. It will add about 15% more fuel over the range (depending on what rpm band your in)

-Henrik

Pump yes, but not necessarily so for the injectors. Injectors only need to be upgraded if you reach max safe duty cycle of 80-85%. If you're running lean below that duty cycle, it's either insufficient fuel pressure or insufficient injector opening time.

First you need to ensure they get enough pressure (upgrade the fuel pump), then you need to make sure the ECU is telling them to open long enough for sufficient fuel (fuel controller or standalone).

If after those two items have been addressed you still can't get adequate mixtures without exceeding 80-85% injector duty cycle, then you need bigger injectors. :)

So you're saying this enrichment via the boost sensor does not happened after 1.6psi (or 3psi?)


-Ted

It tops out at 1.6 (or 3psi). Above that value its still applied but constant wrt the boost sensor.

Here's a log snippet with some real values:
fields are: time, rpm, AFM reading, boost sensor, AFM temp, elbow temp, injector ms, water temp, "boost" correction.
N332,L,0745,00:00:23.22,1860,198,1.1in,31.9,39.4,7 .0,81.2,14.8%
N332,L,0746,00:00:23.23,1882,197,0.2in,31.9,39.4,7 .1,81.2,14.8%
N332,L,0747,00:00:23.26,1870,194,0.0psi,31.9,39.4, 7.1,81.2,14.8%
N332,L,0748,00:00:23.27,1896,197,0.2psi,31.9,39.4, 7.0,81.2,14.8%
N332,L,0749,00:00:23.29,1884,187,0.4psi,31.9,38.8, 7.5,81.2,14.8%
N332,L,0750,00:00:23.30,1908,191,0.5psi,31.9,38.8, 7.1,81.2,14.8%
N332,L,0751,00:00:23.32,1912,184,0.7psi,31.9,38.8, 7.5,81.2,14.8%
N332,L,0752,00:00:23.33,1924,186,0.7psi,31.9,38.8, 7.3,81.2,14.8%
N332,L,0753,00:00:23.35,1950,183,1.0psi,31.9,38.8, 7.7,81.2,14.8%
N332,L,0754,00:00:23.36,1930,182,1.1psi,31.9,38.8, 7.6,81.2,14.8%
N332,L,0755,00:00:23.38,1946,180,1.3psi,31.9,38.8, 7.7,81.2,14.8%
N332,L,0756,00:00:23.39,1962,178,1.3psi,31.9,38.8, 8.0,81.2,19.9%
N332,L,0757,00:00:23.41,1966,179,1.7psi,31.9,38.8, 8.2,81.2,19.9%
N332,L,0758,00:00:23.43,1998,174,1.9psi,31.9,38.8, 8.4,81.2,19.9%
N332,L,0759,00:00:23.45,2000,176,1.9psi,31.9,38.8, 8.1,81.2,19.9%
N332,L,0760,00:00:23.47,2012,169,2.1psi,31.9,38.8, 8.8,81.2,19.9%
N332,L,0761,00:00:23.48,2008,170,2.3psi,31.9,38.8, 8.5,81.2,19.9%
N332,L,0762,00:00:23.50,2030,171,2.5psi,31.9,38.8, 8.5,81.2,19.9%
N332,L,0763,00:00:23.51,2030,166,2.6psi,31.9,38.8, 8.7,81.2,19.9%
N332,L,0764,00:00:23.54,2040,166,2.8psi,31.9,38.8, 8.9,81.2,19.9%
N332,L,0765,00:00:23.56,2058,166,2.9psi,31.9,38.8, 8.8,81.2,19.9%
N332,L,0766,00:00:23.57,2066,162,2.9psi,31.9,38.8, 9.2,81.2,19.9%
N332,L,0767,00:00:23.60,2090,161,3.3psi,31.9,39.4, 9.0,81.2,19.9%
N332,L,0768,00:00:23.61,2098,161,3.5psi,31.9,39.4, 9.1,81.2,19.9%
N332,L,0769,00:00:23.63,2124,158,3.6psi,31.9,39.4, 9.5,81.2,19.9%
N332,L,0770,00:00:23.65,2106,158,3.7psi,31.9,39.4, 9.4,81.2,19.9%
N332,L,0771,00:00:23.67,2116,158,3.9psi,31.9,39.4, 9.3,81.2,19.9%
N332,L,0772,00:00:23.70,2152,158,4.1psi,31.9,39.4, 9.3,81.2,19.9%
N332,L,0773,00:00:23.74,2174,157,4.2psi,31.9,39.4, 9.3,81.2,19.9%
N332,L,0774,00:00:23.77,2164,153,4.3psi,32.5,39.4, 10.0,81.2,19.9%
N332,L,0775,00:00:23.80,2188,152,4.4psi,32.5,39.4, 9.9,81.2,19.9%
N332,L,0776,00:00:23.82,2208,150,4.8psi,32.5,39.4, 10.0,81.2,19.9%
N332,L,0777,00:00:23.84,2228,150,4.8psi,32.5,39.4, 9.9,81.2,19.9%
N332,L,0778,00:00:23.86,2216,148,5.1psi,32.5,39.4, 9.9,81.2,19.9%
N332,L,0779,00:00:23.89,2238,149,5.1psi,32.5,39.4, 9.8,81.2,19.9%
N332,L,0780,00:00:23.91,2258,149,5.2psi,32.5,40.0, 9.9,81.2,19.9%
N332,L,0781,00:00:23.94,2252,153,4.8psi,32.5,40.0, 9.7,81.2,19.9%
N332,L,0782,00:00:23.95,2276,159,3.3psi,32.5,40.0, 8.8,81.2,19.9%
N332,L,0783,00:00:23.99,2278,176,1.2psi,32.5,40.0, 7.1,81.2,19.9%
N332,L,0784,00:00:24.03,2304,198,0.9in,32.5,40.0,5 .6,81.2,14.8%
N332,L,0785,00:00:24.06,2294,198,2.5in,32.5,40.6,5 .7,81.2,14.8%
N332,L,0786,00:00:24.09,2300,224,5.1in,32.5,40.6,4 .8,81.2,0.0%

-Henrik

OK, here's another FCD question. Which ones are clamp type and which ones are voltage divider type? What type does RB, HKS, GREDDY, and all them use?

Sampling rate about 75Hz?
Was the TPS input monitored at the same time?
What simulator system/program was this run on?


-Ted

Ah, sorry, time on that one is about 3x fast (its an early log where I had a bug in my timestamping). TPS was monitored as well, I stripped it out 'cause its not terribly interesting, 4.7v for the entire run except for the last three lines (4.4, 4.2, 3.6v respectively). I can log pretty much anything that the stock ECU sees/computes.

Simulator, bah, this was run on my TII - here's pic on what the inside of my ECU looks like, you'll note it has a few extra chips :)

https://www.rx7club.com//attachment....postid=2384109

-Henrik

I know you've had success cracking the code on the stock ECU (via another forum - or did you mention it here?).  Would you be willing to share the info? :)

I would love to get a peek at the disassembled code myself.


-Ted

I don't visit here every day - Email me and we can talk offline.

-Henrik

Does anyone know?????

All of them are clamp-types now.


-Ted

One more example of the inscrutible ECU. I blew my first engine immediately after installing an FCD so I have always associated that installation with lean running. Maybe it was just coincidence and cool temperatures.

So if fuel flow is not a function of boost, but only of volumetric air flow and perhaps manifold air temperature it is no wonder that the engine runs lean on cold days. To know the mass air flow, and thus the correct amount of fuel to add, the ecu really needs to know volume flow, pressure and temperature.

At what air flow (in terms of hp) does the air flow meter on the S5 reach full travel? Since the fuel flow map is not a function of boost, does the fuel map not extend to the full travel of the air flow meter?

The questions I ask about blown engines are:

Did your engine blow at night?
Did you do a fuel pump rewire?
Were you using an upgrade fuel pump?



Most engines blow at night, when the load on the electrical system is highest.  Our experiments with the voltage going to the fuel pump shows a serious drop in voltage - some as low under 10.0VDC!



-Ted

Yes!

At that time I had a stock pump with stock wiring. Subsequent to that I checked the fuel pressure per the service manual, and also installed a rising rate fuel pressure regulator that demonstrated that the pump could supply 60 psi at full throttle (although I never tried it at night, as the fuel pressure gauge was a temporary external unit.

I have since installed a Walbro and I will check the fuel pump voltage before I drive it again. The car is very clean and corrosion free so I don't anticipate a wiring problem.

Thanks for your very interesting insight.

does msd make some sort of ignition time'ing box that will help you with this problem? the digital-6 or something? if you are getting the correct amount of fuel.. the only other problem with building more boost is the time'ing right? how do you get around this?

Actually, with S4 MAF meters, there is a temp sensor right in front of the flapper valve. Also, since the air has to physically push/pull the flapper valve open, it measures pressure and volume at the same time, using the temperature to more accurately determine the volume/pressure. I'm not sure if the S5 MAF meters are set up similarlly.

The AFM does not measure pressure, as this has no bearing on determining airflow. The flaps deflection (which is what is actually measured) is proportional to volume flow, and the temp sensor is used to convert this to mass flow.

The S5 AFM works in exactly the same way, using a sliding cone instead of a swinging flap.