i was looking into support mods for my setup and stumbled across this:



its the j&s knock sensor. its purpose is to prevent lean conditions and detonation, which...we all know will destroy apex seals. ive dont extensive research on this and just about every source says that is can be used on stock or heavily moded setups...? does the pfc, microtech or any other ecu upgrade/engine management system already have knock retardnt built in....or something that would make this knock sensor unecessary or useless?

its around $600-$700, and everyone says its well worth the money. any one have any experience with this product or even recommend it?

any info is much appreciated,
adam

link to there site:
http://www.jandssafeguard.com/safeguard.html

thread that discusses it (there is very minimal info here, i wanted more info and opinions):
https://www.rx7club.com/power-fc-forum-47/power-fc-knock-sensor-question-18094/

 

Get a wideband and a PFC and call it a day.

 

Stand alones don't retard timing for knock that I know of. It definitely can't hurt to have this. Preturbo EGT sensors and a dual digital gauge is even better though IMO.

 

A J&S is an old-school mod. It will probably not do any harm (unless you retard timing too much and get negative split) but a proper tune is a better 'mod'. The money would be better spent on a professional tune.

 

would a dyno tune by dave at kdr count as a professional tune?

 

Could you recommend a wideband? I have a PowerFC with datalogit which needs to be a tuned.

thewird

 

This mod doesn't replace a good tune, widebands, egt's; rather, it augments them, providing safety net, especially if you use an agressive tune. Properly used they are worth the money (I picked up a $200 used one for the FD.) and I have used them with success on piston engines.

The advantage of a system like this is that it can detect pings and retard the timing much faster than you can. According to Rob at Pineapple, the rotary is a noisy engine and you need to set the J&S threshold accordingly for best results. Also use the lower (10deg, I think) retard range to prevent negative split issues (under most circumstances--If you run 0 split, then you will need to re think this).

 

would you recommend it for a setup such as full bolt on's, piggy back ecu, and 12lbs(no port-work)

 

KDR tuning has mixed reviews on the board so I suggest that you read up on them since it's the most important investment in your entire build up. I've heard that the J&S listens for possible pre det pinging, but by the time it hears it a seal is pretty much toast. Works well on a more resistant piston engine though. I would recommend the PFC, wideband, and professional tune as a better place to put my money first.
good luck man.

 

PLX M-300
http://www.plxdevices.com/products/m300/

I am extremly impressed with this wideband.... cheap, very acurate and reliable. I love it and its mounted on my stearing column.

 

I had to set my J&S to almost the lowest sensitivity to avoid picking up noise. It sometimes picks up some light knock when it's very cold out, and I can definitely feel it backing off timing.

I told my tuner that I was concerned with negative split with the J&S, so he made sure split was always at least 12 degrees. And I keep mine set to 10 degrees max retard. I don't know about the split range with the stock ECU.

The ideal setup is a 4-channel J&S which can independently retard timing on both leading and trailing coils without effecting timing split.

 

That's odd that the engine is so noisy when monitoring it like this... compared to any piston engine rotaries are audibly quieter w/ no valve train noise.

 

The combustion event is much more violent and energetic in a rotary, by the same token that an open exhausted rotary is much hotter and louder than an open exhaust piston engine.

I've always been told that the usefulness of these was very limited in rotaries due to this. The normal combustion events are so noisy that the safeguard has a hard time distinguishing it from knock, and when you desensitize it far enough, it becomes of no real value anyway.

Also from what I am told, the stock knock detection system in the turbo rx7 ecu's is pretty much ignored by the ecu above 4-5krpm because again, it can't distinguish normal combustion from knock due to the noise and violence.

 

Ordered one off eBay Thanks.

thewird