VPC-SAFC Fuel Cut Issue

[supraguy31]

I have a Question for you all and Im hoping that someone can give me some Direction. I took the car out to the track tonight and decided to do a few runs with it. TF-07 Turbo Starts to Spool up really hard about 3000 rpm and the Boost jumps really fast up to 14PSI but Im hitting fuel cut in every Gear. 1st, 2nd and 3rd.

A/F ratio at full boost is 10.5, I had a friend watch my gauges for me while we went down the track

Dam turbo Pulls it fricken Ass off.

What can I do to stop Fuel Cut with the VPC-SAFC

Thanks for any Ideas or Advice
Robert

 

[robbo185]

what are your fuel mods???

was it cold out...if its super cold sometimes i hit fuel cut

do you have any boost leaks?

 

[supraguy31]

Fuel Mods......
MKIV TT Fuel Pump
RC 550s
AEM Fuel Pressure Regulator set at 38 PSI
VPC /SAFC to control it all
Wideband
etc
etc

It wasnt really cold out at all, Maybe in the Mid 40s, Ive never run a Setup like this before VPC anyways so Im not 100% Sure of how to Adjust things to correct this Problem. No Boost Leaks at all.

Robert

 

[supraguy31]

Any More Suggestions...... Anyone?????

 

[empera]

aim for ~11.5 a/r and see if that solves part of it.

 

[MKIIINA]

i know i have run my car out to 18 or so psi on my old sp61gt w/o fc. what do your settings look like on the vpc and the safc? iirc if the gain is too far off one way or the other on the vpc it will bring the fc threashold down by quite a bit.

 

[97TSiAWD]

Fuel cut is caused by a number of factors, but the main one is the ECU "seeing" too much airflow. With piggyback tuning devices (such as the SAFC), the way to work around fuel cut is to simply reduce the airflow signal the ECU sees by reducing the %-adjustment settings across the RPM range. Obviously, reducing the airflow signal will reduce the amount of fuel delivered, so it will lean things out.

So, as has been mentioned, aiming for a 11.5:1 air/fuel ratio should be a good start. If you want to keep it running rich at 10.5:1, you can also increase the fuel pressure a tad, and then decrease the SAFC settings.

 

[supraguy31]

Well, I ran it today on Interstate 10 with a few Friends of mine.... Now my Fuel Pressure is set at 38 PSI. Everything on the VPC is set to 12o'clock Position
When Im in either 1st or 2nd taking off, My A/F out lean completely and Im not getting boost for shit. (Sputters and Hesitation Big time) When I shift into 3rd Gear, Turbo Spools up and Its starts the Pull its ass Of, When my A/F reads 10.5, Ive even Adjusted the SAFC on High settings down to -20 and its still running Rich..... Im wondering if the ECU or the VPC is correcting the Settings that Im imputing into the SAFC.

I know this is a Strange Question but What should the Gain be Placed at. It Idles and starts up just fine set at the 12 o'clock Position. Just not for sure about the leaning out totally and Hesitation when I get on it in 1st or 2nd.

I was told Also dont mess with the Low Settings, Only Adjust the High settings one the SAFC. Use the VPC to Adjust the low settings.

This is what is happeneing at this Present time so Any help figuring this out would be greatly Appreciated.

Robert

 

[suprashy]

Fuel Mods......
AEM Fuel Pressure Regulator set at 38 PSI...

Robert

The 38psi is with vacuum on or off? IF its off, then that's not the issue:

http://www.cygnusx1.net/Supra/Library/TSRM/MK3/manual.aspx?Section=FI&Page=73.

If its with vacuum on, then that would explain your richness. HTH.

I suspect you have a 7MGTE.....

 

[supraguy31]

Yes, this is with Vacuum on. Im running a AEM FPR and It was suggested to me that I set it at 38 PSI so that is what I did. I was also told that Stock Fuel Pressure for a 7MGTE was like 35 PSI so that is why It should be set there. From looking at the Manual, Seens that stock Pressure is between 23-30 PSI Did I get some bad Information, If so then Im cutting the fuel Pressure down.

Yes, I have a 7MGTE in a MKII

Robert

 

[supraguy31]

Dam thank you for the Information of this. I went out and did a Check as the Manual Stated. I disconnected the Vacuum line and the Pressure Jumped up to 47PSI. I moved it back to where the Manual Stated it would be with the Line Disconnected (40PSI) and Plugged the line back in and the Pressure Dropped to 30PSI which is the Facory Settings Im talking it.

We will see what this Does also.

Now I need to figure out the Part with 1st and 2nd gear. Even if I bearly have my foot on the gas and I cruising down the road, The A/F pressure will start out at 14.4 and slowly drop to really lean. The only way I can correct it is to give it some gas then it will move back up to around 15.1 or so.

Robert

 

[suprashy]

Dam thank you for the Information of this....
Now I need to figure out the Part with 1st and 2nd gear. Even if I bearly have my foot on the gas and I cruising down the road, The A/F pressure will start out at 14.4 and slowly drop to really lean. The only way I can correct it is to give it some gas then it will move back up to around 15.1 or so.

Robert

Your most welcome! I've learned from the best, and I consider my sources to be of the utmost elite calibre. I'm trying to pass on a few things I've learned (and still am learning) on the way.

After re-setting your fp, did you re-adjust your S-AFC?

<<The A/F pressure will start out at 14.4 and slowly drop to really lean. The only way I can correct it is to give it some gas then it will move back up to around 15.1 or so.>>

If it DROPS, it becomes richer. Meaning from 14.4 to 13.4 means the ratio has become richer. Just wanna make sure we're on the same page here. Keep us posted.

 

[supraguy31]

SUPRASHY... You have PM

There are a few More Issues that I have to figure out. I dont trust myself enough yet to Mess with the Gain and the Response because Im not for sure which way I need to Adjust them and What the Purpose if them are completely.

When I mean that Im at 14.4 and it slowly goes to lean is that if Im driving down the Highway and I have the RPMs steady at 2500 or so, The A/F ratio will be at 14.4, within a few Seconds, It will start to Drop off and go completely lean and start to Sputter, Now Im still at 2500rpms. If I give it some gas It will jump back up but as soon as I get back to the Cruising Stage, It does it all over again. I had to Adjust the SAFC on the 2000 to 3000 Low throttle band to +16 and +20 to Keep it at or about the 14.5 area. Wouldnt you consider this a Little much?

Sorry you all for asking so many Questions. The MAF-T I had was 10 Times Easier to configure and setup. Im just not for sure that this VPC was a good Idea overall.

Oh, Last thing and this is the Stange one. In 2ND Gear, I punched it and It boosted up to 13 PSI without fuel cut. Go to a Light and do it again, I boosted up to 6PSI and it started Jerking back and forth and it seemed like I hit a Brick wall....

Robert

 

[X-man]

Robert, I have run as much as 32 psi when I had my 67 mm turbo on the car with a VPC,AFC, and 680 cc injector combo and never hit fuel cut. I have another car I built that runs the same basic setup I had with the exception that he is on a stock headgasket still and pump gas boost psi is 16 and is making 450 rhwp/440 rwtq and we have never hit the fuel cut. We have run as much as 20 psi on it with a 67 mm turbo and still no fuel cut in any gear.
Make sure that you afc is hooked between the vpc head unit and stock ecu and make sure your afc is set for karman vortex and all of your vpc knobs should be at 12:00. Also I always found that setting you low throttle settings the same as you high throttle settings always made the car respond alittle quicker. Most of the time you won't be much past 3000 rpm in daily driving anyways and depending on when your turbo starts to spool you shouldn't even have to start your corrections until about 3000 rpm. My afc settings were
0 - 1000 rpm
-7 - 3000 rpm
-10 - 3500 rpm
-13 - 4000 rpm
-16 - 4500 rpm
-15 - 5000 rpm
-15 - 5500 rpm
-15 - 6000 rpm
or thereabouts on my car at 19 psi with 31 psi of base fuel (line off) with the SP67 turbo and 680 cc injectors. This was a full T4 turbo set up and not a bolt on also. You also have nothing to worry about getting advice from Shyler as he has done a beautiful job tuning his car and will not steer you wrong.
Sean

 

[X-man]

You also don't have to worry about tuning anything under 65 to 70% throttle. As long as you have a good O2 sensor on your car, I used one for a 88 5.0 Mustang, the ecu will keep it where it needs to be as far as the a/f's go. Mine cruised anywhere 14.5 to 15.5, and sometimes would hit 14.2 but then would occasionally see 16.2. Most of the time in normal driving you won't be much over 15 to 20 % throttle, but you would have to ask Shyler what my throttle change over was as he bought my old afc.
Sean

 

[supraguy31]

im using a Wideband and Narrow Band O2 sensor on my car to make sure everything is correct. I have my SAFC wired into the VPC Main Harness. Now Im not for sure How the Head Unit is Placed, I was just told to wire in Directly into the Main Harness using the ECU wiring Diagram. Thats All I did

Robert

 

[X-man]

Here is a diagram of what I'm refering too.
Sean

 

[supraguy31]

Mr X-man,

As Promised here is the Harness that came with my VPC setup. I havent seen one like this before so Im not for sure if I made a Bad decision getting it. As you see, Completely white on one side, Completely green on the other

All of a Sudden the Fuel cut is gone. I drove home today and After setting everything back up the way we talked about I got it on the Highway and in 3rd and 4th Gear I hit 20 PSI. Now funny thing is that my Boost controller is set for 14PSI and the boost wanted to just keep going. Its an External Wastegate and I have the Setting on the back of it correct. Dont know why its not stoping at what I have it set on.

OH, Its an HKS EVCIV

Robert

 

[suprashy]

supraguy31:

U stated you hardwired the S-AFC to the VPC. If you want to verify your wiring, I'm attaching a pic. of how I did it using X-Man's diagram and help. The pic. shows the wire loom that comes out of the VPC (Right side of pic). The extreme right is the SAFC wiring. (I have an SAFC I).

Why u're boosting 20 psi instead of your EVC set to 14 could be a stuck WG? Are your vacuum hoses setup correctly?

Thanks X-man for the kind words noted above!

 

[suprashy]

Supraguy 31:

Also, most importantly, what is the WG spring pressure? Glad to hear u've resolved the fuel cut issue.