Ignition system?: Anyone chime in on this problem ? - Zilvia.net Forums | Nissan 240SX (Silvia) and Z (Fairlady) Car Forum

Tom Ngan · 10-03-2007, 10:58 PM

Setup:
SR20DET
Gt2871R .86 @ 1 bar
256 HKS St1 cams / otherwise stock head
1.6mm Greddy headgasket
Greddy IM / Greddy FMIC / Greddy BOV
550cc w/ FPR / stock fuel rail / Z32 filter / 255 Walbaro
Stock bottom end / freshly rebuilt / new bearings / seals / gaskets
NGK 7 spark plugs / gapped down
Megasquirt V2 Standalone using crank trigger pulley system running COP

Car dyno'd 258rwhp/238lbs misfiring a bit uptop @ 1 bar on a mustang dyno. We stopped the dyno, and pulled the car off to see what the problem was.

Ok so the deal here is some times the tach signal gets very wonky. It can be idling and all of a sudden 'spike' up and 'jump' around. You can imagine how this affects your driving. Big backfires are common when this happens when I'm driving.

Also sometimes it spikes DOWN, its like the car just shuts off, but it bounces back up.

Anyway, we tested the coil packs on another SR20 and it was misfiring the same way on the dyno and it had the same tach 'jumping' problem. Swapped back his original coil packs and the problem was completely gone.

I know it might be hard to diagnose since I'm running a megasquirt, and it's pretty unique, but could bad coil packs be the problem with the misfiring/jumping tach signal? The coils are setup running waste spark as well. The megasquirt isn't usually setup to run on a car with individual coil on plug setups, so we think this is the problem.

We concluded that were going to try to run dual coil packs from MSD off a SRt-4 to try to get rid of the problem, anyone see any problems with this?

Any help will be great. Thanks.

10-03-2007, 10:58 PM	#1
Tom Ngan Leaky Injector Join Date: Nov 2006 Location: x Posts: 102 Trader Rating: (0) Feedback Score: 0 reviews	Ignition system?: Anyone chime in on this problem ? Setup: SR20DET Gt2871R .86 @ 1 bar 256 HKS St1 cams / otherwise stock head 1.6mm Greddy headgasket Greddy IM / Greddy FMIC / Greddy BOV 550cc w/ FPR / stock fuel rail / Z32 filter / 255 Walbaro Stock bottom end / freshly rebuilt / new bearings / seals / gaskets NGK 7 spark plugs / gapped down Megasquirt V2 Standalone using crank trigger pulley system running COP Car dyno'd 258rwhp/238lbs misfiring a bit uptop @ 1 bar on a mustang dyno. We stopped the dyno, and pulled the car off to see what the problem was. Ok so the deal here is some times the tach signal gets very wonky. It can be idling and all of a sudden 'spike' up and 'jump' around. You can imagine how this affects your driving. Big backfires are common when this happens when I'm driving. Also sometimes it spikes DOWN, its like the car just shuts off, but it bounces back up. Anyway, we tested the coil packs on another SR20 and it was misfiring the same way on the dyno and it had the same tach 'jumping' problem. Swapped back his original coil packs and the problem was completely gone. I know it might be hard to diagnose since I'm running a megasquirt, and it's pretty unique, but could bad coil packs be the problem with the misfiring/jumping tach signal? The coils are setup running waste spark as well. The megasquirt isn't usually setup to run on a car with individual coil on plug setups, so we think this is the problem. We concluded that were going to try to run dual coil packs from MSD off a SRt-4 to try to get rid of the problem, anyone see any problems with this? Any help will be great. Thanks.