misfiring why????? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

zubaz91 · 08-22-2006, 08:38 AM

my car is zenki s14, i have a s15 motor/turbo, s14 ECU, z32 MAFs, 480cc injectors, walbro fuel pump, S-AFC 2, profec bspec2, 3inch turbo back, etc.

i had my car dyno tuned yesterday and the results were very poor. something is wrong. the fuel curve and boost curve are quite steady and not abnormal at all.
The timing is set and was double checked. The plugs are gapped correctly and were brand new. you can hear the misfiring. theres alot of hesitation when u first step on the throttle too.

at 13psi, the car put down 150hp and 140lbs of torque. thats way too low for my setup, the guys showed me charts for a red top with about the same modifications as me and it made 220hp at the wheel. so s15 motor should put down 250 theoretically... not 150, right?

we are baffled. anyone have any ideas?

slider2828 · 08-24-2006, 02:38 AM

Why dyno it when you know there is hesitation... kinda a waste of money bro.... Secondly, I wouldn't care about fuel curve and boost curve... that is useless... You are at a dyno center, look at the AFR and see what is going on... that will tell you a lot.... Secondly on the tune, is it running any timing advance? Thirdly, check your CAS and see if it is still good.... Fourthly, Put a timing light on it at 2000rpm and see if it is steady or jumpy.....

zubaz91 · 08-24-2006, 06:15 AM

AFR is 11 across the band according to the wideband. timing was 15 and we advanced it to 18 or 19 to see if made a difference.. idle get a bit steadier and smoother but under boost it was still missing and there was no power there. another note, i pulled the plugs out and they were all white.. the wideband says rich and the plugs say lean. how can that happen?

slider2828 · 08-24-2006, 01:25 PM

Hmmm that isn't good.... Did you ever check your compression, but if you have access.... do a leak down test which is better.... Secondly an S14 SR ECU or S14KA ecu, secondly you have a S15 motorset, I think there are differences in the ECU as well.....

zubaz91 · 08-24-2006, 01:56 PM

s14 SR ECU.... since i originally bought a s14 front clip but the motor had a bad head so i just put a s15 long block/turbo in basically. all the wiring is still from the s14. are the sensors on the motor different at all? i was under the impression that the s15 and s14 motors were identical and just the turbo was different.

slider2828 · 08-25-2006, 02:12 AM

I t6hyink there is difference in the vtc or whatever....

srs14 · 08-25-2006, 11:59 AM

what did you gap the plugs to ? i would gap them to .045 if it still persist, try.02.

srs14 · 08-25-2006, 11:59 AM

what heat range are the plugs ? 6 or 7

zubaz91 · 08-25-2006, 12:12 PM

plugs are gapped at .028 i tried 6s and 7s

slider2828 · 08-25-2006, 10:53 PM

By any chance did you mess with the ignitor? Did you rewire it or anything?

RedtopTech · 08-26-2006, 06:21 PM

the s15 motor uses 480cc injectors.
thats your problem

peterkim0121 · 08-26-2006, 06:36 PM

hopefuly its the sparkplug or... coil pack...

08-22-2006, 08:38 AM	#1
zubaz91 Join Date: Jun 2005 Location: boston Posts: 48 Trader Rating: (0) Feedback Score: 0 reviews	misfiring why????? my car is zenki s14, i have a s15 motor/turbo, s14 ECU, z32 MAFs, 480cc injectors, walbro fuel pump, S-AFC 2, profec bspec2, 3inch turbo back, etc. i had my car dyno tuned yesterday and the results were very poor. something is wrong. the fuel curve and boost curve are quite steady and not abnormal at all. The timing is set and was double checked. The plugs are gapped correctly and were brand new. you can hear the misfiring. theres alot of hesitation when u first step on the throttle too. at 13psi, the car put down 150hp and 140lbs of torque. thats way too low for my setup, the guys showed me charts for a red top with about the same modifications as me and it made 220hp at the wheel. so s15 motor should put down 250 theoretically... not 150, right? we are baffled. anyone have any ideas?

08-24-2006, 02:38 AM	#2
slider2828 Post Whore! Join Date: Oct 2004 Location: San Francisco, CA Posts: 5,998 Trader Rating: (13) Feedback Score: 13 reviews	Why dyno it when you know there is hesitation... kinda a waste of money bro.... Secondly, I wouldn't care about fuel curve and boost curve... that is useless... You are at a dyno center, look at the AFR and see what is going on... that will tell you a lot.... Secondly on the tune, is it running any timing advance? Thirdly, check your CAS and see if it is still good.... Fourthly, Put a timing light on it at 2000rpm and see if it is steady or jumpy.....

08-24-2006, 06:15 AM	#3
zubaz91 Join Date: Jun 2005 Location: boston Posts: 48 Trader Rating: (0) Feedback Score: 0 reviews	AFR is 11 across the band according to the wideband. timing was 15 and we advanced it to 18 or 19 to see if made a difference.. idle get a bit steadier and smoother but under boost it was still missing and there was no power there. another note, i pulled the plugs out and they were all white.. the wideband says rich and the plugs say lean. how can that happen?

08-24-2006, 01:25 PM	#4
slider2828 Post Whore! Join Date: Oct 2004 Location: San Francisco, CA Posts: 5,998 Trader Rating: (13) Feedback Score: 13 reviews	Hmmm that isn't good.... Did you ever check your compression, but if you have access.... do a leak down test which is better.... Secondly an S14 SR ECU or S14KA ecu, secondly you have a S15 motorset, I think there are differences in the ECU as well.....

08-24-2006, 01:56 PM	#5
zubaz91 Join Date: Jun 2005 Location: boston Posts: 48 Trader Rating: (0) Feedback Score: 0 reviews	s14 SR ECU.... since i originally bought a s14 front clip but the motor had a bad head so i just put a s15 long block/turbo in basically. all the wiring is still from the s14. are the sensors on the motor different at all? i was under the impression that the s15 and s14 motors were identical and just the turbo was different.

08-25-2006, 02:12 AM	#6
slider2828 Post Whore! Join Date: Oct 2004 Location: San Francisco, CA Posts: 5,998 Trader Rating: (13) Feedback Score: 13 reviews	I t6hyink there is difference in the vtc or whatever....

08-25-2006, 11:59 AM	#7
srs14 Leaky Injector Join Date: Aug 2005 Location: Hanover Park, IL Posts: 126 Trader Rating: (0) Feedback Score: 0 reviews	what did you gap the plugs to ? i would gap them to .045 if it still persist, try.02.

08-25-2006, 12:12 PM	#9
zubaz91 Join Date: Jun 2005 Location: boston Posts: 48 Trader Rating: (0) Feedback Score: 0 reviews	plugs are gapped at .028 i tried 6s and 7s

08-25-2006, 10:53 PM	#10
slider2828 Post Whore! Join Date: Oct 2004 Location: San Francisco, CA Posts: 5,998 Trader Rating: (13) Feedback Score: 13 reviews	By any chance did you mess with the ignitor? Did you rewire it or anything?

08-26-2006, 06:21 PM	#11
RedtopTech Zilvia Member Join Date: Dec 2005 Location: Virginia Beach, VA Age: 39 Posts: 293 Trader Rating: (0) Feedback Score: 0 reviews	the s15 motor uses 480cc injectors. thats your problem

08-26-2006, 06:36 PM	#12
peterkim0121 BANNED Join Date: Sep 2005 Location: tokyo shibuya shi / yuma az Age: 39 Posts: 376 Trader Rating: (0) Feedback Score: 0 reviews	hopefuly its the sparkplug or... coil pack...