hooked up apexi power fc, causes surging idle, common problem? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

mykem · 05-29-2004, 07:14 PM

i bought a used power fc, and it powers up just fine, i let it idle for 10 mins, turned on the defroster, let it idle another ten minutes, then i took it around the block, after the driving the idle surges in between 450 and 1000 rpm 'up down up down'..you know

is this a common problem? i initialized the unit, so it should be running at stock settings, i just am hoping it isn't a defective unit, just wondering if any of you had a similar problem, for now i just hooked the stock ecu back up, and the car runs perfect, this is for a redtop s13 motor in a 90 coupe, car was an automatic origionally

Jamesnutt · 06-30-2004, 05:46 PM

Hi, just wondering if you figured out the PowerFC?

MIke

silviaspeed14 · 09-17-2004, 07:24 PM

I have a 95 with 96 sr20det and my power fc has the same problem. Sometimes mine wont even keep an idle. It seems to be ok when i drive it. Let me know what you find out. i had to put back in the stock ecu also. My apexi was also bought used.

LOwrestling2k1 · 09-18-2004, 02:32 AM

hrm, check ur mafs settings, make sure it's on the right setting. also, boost control kit setting in the "etc" menu is default "on" (in japanese), make sure u have that off. (unless u are running hte pfc boost control kit of course).

ericherm1 · 10-07-2005, 08:35 PM

I have the exact same problem. I have a 91 coupe with a 94 Blacktop out of a 180sx, Power FC with the Boost control kit and commander. I also have 264 cams, Z32 MAF and 550cc injectors. My car will not idle correctly, it also surges between 450 and 1000rpms. I keep thinking its the damn timing but everytime I check it its fine. Oh and my Check engine light is on at idle but at mid to full boost it goes out. Anyone have any ideas?????????

NZO · 10-07-2005, 09:12 PM

Try adjusting mafs correction up and down ~50% and see what happens.

ericherm1 · 10-07-2005, 10:03 PM

Thanks man your site is GOD!!! anyhow I'll try adjusting the MAF settings tomorrow afternoon and let you know how it went...

ericherm1 · 10-07-2005, 10:07 PM

Oh yeah, I almost forgot. Where can I get a good datalogit or smililer program?

ericherm1 · 10-11-2005, 07:51 PM

Ok the problem with surging has little to do with the MAF when using the Power FC and the MAF setting set to VQ30DETT. The problem with my idle I believe is the injector latency.

Here is what I mean:

"Next we need to adjust the injector latency, 7F88. The injector latency is a certain constant of injector pulsewidth added to the calculated pulsewidth to compensate for the time delay in opening and closing of the injectors. Larger injectors open and close at a slower rate so this constant needs to be increased appropriately. Its biggest affect is on the idle, too high and the car will idle rich or not run at all; too lean and the idle will be lean or not run at all. The stock value is 4Bhex or 75dec. So playing with this formula 75dec / 370cc = X / 555cc, X equates to 112dec or 70hex. This formula for adjusting injector latency seems to give a bit too much fuel. Through some experimentation I have found that taking the equated value (112), subtracting it by the stock value (112 75 = 37), dividing that value in half (37 / 2 = 18.5), adding that value to the stock value (18.5 + 75 = 93), usually gives a more accurate Latency value. In this case it would be 93dec or 5Dhex. I used this equation for my SR20DET 180sx which is running 850cc main injectors, stock is 370cc. My idle is smooth at the stock 850rpms, and the car is getting very nearly stock gas mileage."

This is a write up for tuning a 300zx twin turbo but all the formulas work for our cars too.

here is his website: http://www.ztechz.net/id10.html

Hope this helps everyone.
I can't tell you if it worked yet because of an oil leak on the oil return line off the s15 turbo. Still waiting for the replacement from Phase2. When I get it done I'll let you guys know if it worked.

05-29-2004, 07:14 PM	#1
mykem Zilvia Member Join Date: Nov 2003 Location: Mundelein Posts: 175 Trader Rating: (9) Feedback Score: 9 reviews	hooked up apexi power fc, causes surging idle, common problem? i bought a used power fc, and it powers up just fine, i let it idle for 10 mins, turned on the defroster, let it idle another ten minutes, then i took it around the block, after the driving the idle surges in between 450 and 1000 rpm 'up down up down'..you know is this a common problem? i initialized the unit, so it should be running at stock settings, i just am hoping it isn't a defective unit, just wondering if any of you had a similar problem, for now i just hooked the stock ecu back up, and the car runs perfect, this is for a redtop s13 motor in a 90 coupe, car was an automatic origionally

10-07-2005, 08:35 PM	#5
ericherm1 Join Date: Jun 2005 Location: grandforks ND Posts: 18 Trader Rating: (0) Feedback Score: 0 reviews	I have the exact same problem. I have a 91 coupe with a 94 Blacktop out of a 180sx, Power FC with the Boost control kit and commander. I also have 264 cams, Z32 MAF and 550cc injectors. My car will not idle correctly, it also surges between 450 and 1000rpms. I keep thinking its the damn timing but everytime I check it its fine. Oh and my Check engine light is on at idle but at mid to full boost it goes out. Anyone have any ideas????????? Last edited by ericherm1; 10-07-2005 at 10:10 PM..

10-07-2005, 09:12 PM	#6
NZO Zilvia FREAK! Join Date: Mar 2002 Location: Reno, NV Age: 42 Posts: 1,424 Trader Rating: (0) Rides Gallery: NZO Feedback Score: 0 reviews	Try adjusting mafs correction up and down ~50% and see what happens. __________________ sentinelguild.com/nzo/PFCDB/

06-30-2004, 05:46 PM	#2
Jamesnutt Leaky Injector Join Date: Aug 2003 Location: Independence,MO Age: 44 Posts: 59 Trader Rating: (0) Feedback Score: 0 reviews	Hi, just wondering if you figured out the PowerFC? MIke

09-17-2004, 07:24 PM	#3
silviaspeed14 Join Date: Feb 2004 Location: chambersburg pa Posts: 16 Trader Rating: (0) Feedback Score: 0 reviews	I have a 95 with 96 sr20det and my power fc has the same problem. Sometimes mine wont even keep an idle. It seems to be ok when i drive it. Let me know what you find out. i had to put back in the stock ecu also. My apexi was also bought used.

09-18-2004, 02:32 AM	#4
LOwrestling2k1 Leaky Injector Join Date: Jan 2004 Location: Why? Posts: 55 Trader Rating: (0) Feedback Score: 0 reviews	hrm, check ur mafs settings, make sure it's on the right setting. also, boost control kit setting in the "etc" menu is default "on" (in japanese), make sure u have that off. (unless u are running hte pfc boost control kit of course).

10-07-2005, 10:03 PM	#7
ericherm1 Join Date: Jun 2005 Location: grandforks ND Posts: 18 Trader Rating: (0) Feedback Score: 0 reviews	Thanks man your site is GOD!!! anyhow I'll try adjusting the MAF settings tomorrow afternoon and let you know how it went...

10-07-2005, 10:07 PM	#8
ericherm1 Join Date: Jun 2005 Location: grandforks ND Posts: 18 Trader Rating: (0) Feedback Score: 0 reviews	Oh yeah, I almost forgot. Where can I get a good datalogit or smililer program?

10-11-2005, 07:51 PM	#9
ericherm1 Join Date: Jun 2005 Location: grandforks ND Posts: 18 Trader Rating: (0) Feedback Score: 0 reviews	Ok the problem with surging has little to do with the MAF when using the Power FC and the MAF setting set to VQ30DETT. The problem with my idle I believe is the injector latency. Here is what I mean: "Next we need to adjust the injector latency, 7F88. The injector latency is a certain constant of injector pulsewidth added to the calculated pulsewidth to compensate for the time delay in opening and closing of the injectors. Larger injectors open and close at a slower rate so this constant needs to be increased appropriately. Its biggest affect is on the idle, too high and the car will idle rich or not run at all; too lean and the idle will be lean or not run at all. The stock value is 4Bhex or 75dec. So playing with this formula 75dec / 370cc = X / 555cc, X equates to 112dec or 70hex. This formula for adjusting injector latency seems to give a bit too much fuel. Through some experimentation I have found that taking the equated value (112), subtracting it by the stock value (112 75 = 37), dividing that value in half (37 / 2 = 18.5), adding that value to the stock value (18.5 + 75 = 93), usually gives a more accurate Latency value. In this case it would be 93dec or 5Dhex. I used this equation for my SR20DET 180sx which is running 850cc main injectors, stock is 370cc. My idle is smooth at the stock 850rpms, and the car is getting very nearly stock gas mileage." This is a write up for tuning a 300zx twin turbo but all the formulas work for our cars too. here is his website: http://www.ztechz.net/id10.html Hope this helps everyone. I can't tell you if it worked yet because of an oil leak on the oil return line off the s15 turbo. Still waiting for the replacement from Phase2. When I get it done I'll let you guys know if it worked.