J&S Safeguard help on rb25

[robbie2883]

ok guys, i've had this j&S safeguard for years and no issues on either of my other two cars, but i can't for the life of me get it working right on my 98' 240 with rb25 swap. for those who don't know what it is check out http://www.jandssafeguard.com it's a knock retard system. I wired the unit up using a patch harness and setting it up in 3 channel mode converting to waste spark ignition. i tied coils coils together in parallel two per channel. cyl 1 and 6 on 1, 2 and 5 on 2 and 3 and 4 on 3. made sure to diode isolate the inputs as well. from there i hooked the two knock sensors up to the one knock input and diode isolated that as well. car starts fine, idles fine, but breaks up if i go over say 2-3k rpms or into any kind of boost. it's a pretty straight forward wiring setup so i'm a little confused. the only thing that i can think if is i'm wiring right off the ecu. my other cars had the igniter built into the coild where this car has the igniter seperate. i wouldn't think this would matter but as of now i'm stumped. i did try running without the knock sensors hooked to the j&s and it acted the same.

any input from the pros would be greatly appreciated.

here's the mods pertaining to the problem. 1998' 240sx with rb25 swap (runs great off factory ecu and pfc)pfcstock igniter chipsplitfire coils

[Darius]

Maybe this is a stupid question, but why do you need J&S if you have a halfway decent tune and PFC? Seems like a waste of money on a redundant system.

[240z4u]

Maybe this is a stupid question, but why do you need J&S if you have a halfway decent tune and PFC? Seems like a waste of money on a redundant system.

Darius, the pfc does not pull timing during knock if memory serves. It just gives you a headsup that your going to explode some pistons.

[robbie2883]

Maybe this is a stupid question, but why do you need J&S if you have a halfway decent tune and PFC? Seems like a waste of money on a redundant system.

it's not redundant at all (pfc has no form of knock control) and not expensive when i already had it! i've learned the hard way that you can NEVER be too safe when it comes to performance engines (this motor is built), especially in florida where the weather and humidity change every hour! LOL

anyway it's not a tuning device, it's purely a safety device to monitor the knock system and pull timing when if it detects knock. it also has an aux switch which can be hooked up to a nitrous system to automatically pull timing when you're spraying.

anyway back to the issue, could it possibly be that that igniter has problems firing 2 coils at once? or maybe i need to try to supply a stronger signal to the igniter in order for it to fire 2 coils at once?
Modified by robbie2883 at 5:46 PM 5/19/2009

[Darius]

I realize that the J&S Safeguard is only for retarding timing, but I look at the knock readings on the PFC hand controller enough to develop carpel tunnel in my neck. Past issues have made me paranoid enough to constantly look at the engine vitals while I drive. And if I fail to notice the rapidly blinking check engine light while my engine is knocking itself apart, I'm a moron and deserve to rebuild. And weather won't affect a MAF based system like it does a MAP system, so even less of a risk there.

Back on track here, I'm assuming that once it starts to build boost, the engine begins to buck and stutter. Does that sound accurate? From recent experience with the stock RB coils, I'd have to say that making them fire twice as much is not going to work well on initial settings.

The dwell is already short, at approximately 2-2.7 mS and halving that by running wasted spark could dramatically reduce the charge the coils develop during dwell. Less charge means less energy to light off the air/fuel mixture and a bucking bronco results.

The PFC input is "IGNdwell vs. RPM" in units of degrees so try multiplying the dwell degrees by 1.5 and see if that helps. Otherwise, installing better coils or removing the Safeguard are the alternative options.

Let us know what you find and hopefully we can get this ironed out!

[robbie2883]

darius, i COMPLETELY agree with you on what you're saying about the falshing light and so forth. i am coming from a haltech, map based background and learning as i go. what you are describing is exactly right, only problem being i'm already running splitfire coils. i will try adjusting the dwell time and see what happens. i am assuming i can adjust dwell time in the pfc? you cannot in the safeguard as it only modifies the stock signal.

even if i don't end up running the j&s i still want to figure it out, i'm not one to be beaten by something like this! LOL

*edit...just looked through and see that there is no dwell adjustment on the pfc that i see, so i'm a little confused.
Modified by robbie2883 at 8:22 PM 5/19/2009

[Carl H]

dwell is accessable thru the pfc software...HC has no provisions.check your wiring as well, you may find running a dedicated power wire via a switched relay may help aleviate some problems.you can modify your existing harness/efi relay setup to do this.

[robbie2883]

so you're saying wire the ignition relay beside the ecu with power direct from the battery instead of through the ecu? that's no problem i can try that.

would the datalogit software let me mess with dwell times?

[WhatsADSM]

The addition of the J&S is a great idea. Definitely a lot better at detecting real knock than the PFC.

First off, which side of the ignition are you wiring this? Before or after the ignitor?

The diode isolation is the right thing to do, just also make sure that all the diodes are installed with the correct polarity. On the output side you should not need any diodes you will just hard wire the correct coils together and it will be wastespark.

As for the knock sensor. DO NOT wire the 2 sensors together diode isolated or not. Pick one sensor and wire only that one to the J&S. I don't think this is the issue since you said you completely removed the knock sensors and still had the issue... but none-the-less use 1 knock sensor only.

Finally make sure all the settings with the switches are correct. I don't remember what they are off hand, and also have you tried to lower the sensitivity knob all the way down?

[robbie2883]

diodes are wired in correctly on the input side only. i wired the j&s on the output from the ecu between the ecu and igniter. i was wondering about wiring it in after the igniter. all settings on the j&s are dialed in at zero untill everything is running properly.

[Darius]

would the datalogit software let me mess with dwell times?

Yes, it is under the "Settings4" tab in the upper right hand corner.

[WhatsADSM]

diodes are wired in correctly on the input side only. i wired the j&s on the output from the ecu between the ecu and igniter. i was wondering about wiring it in after the igniter. all settings on the j&s are dialed in at zero untill everything is running properly.

Everything you said sounds correct then. It should be before the ignitor, unless you have one of the newer "Vampire" boxes which essentially Tees into the coil primary (i.e. after ignitor). However my bet is you have the normal 3 (or 4) channel.

If all that is correct not sure what else to tell ya. Just as others said you can check the dwell settings, make sure you have solid power ground to the coils and the J&S. However, if you remove the J&S and then everything works properly, that should mean you have good power/ground and dwell settings are okay. In that case I would triple check that wiring.