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Old 01-02-2005, 04:12 PM   #1
Hitokiri
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Default J&S Sensitivity Anyone

Ok well back to the age old question of what to run for J&S sensitivity.

Anyone have a good det can design such that I can listen for det other than my J&S monitor?

I have always had my unit set to max sensitivity since I got it, and its time to get to the bottom of where exactly is the best setting. Most places I have read say that they had to set it extremely low to get good results. I recall reading a bit by John Banks in UK saying that he found the middle to be about right with his 257 based engine.

So everyone that is using J&S please share what you have found to work best for you. I definitely think its better not to rely on the J&S and simply tune to prevent det whatsoever, but for us stock ECU RS guys without full control we need the blanket that the J&S provides.

Where do you guys have your sensitivity set?

I am going out to look deeper into the pot. that sets the sensitivity. Id really like to see how variable the pot. is and how linear the sensitivity knob on my UltraSafeguard unit really is.

If anyone has done any det can or knock link work please comment.

Todd
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Old 01-02-2005, 04:38 PM   #2
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When I had mine, I had the knob at 1 o-clock. Ran well there on individual cyl retard. (This was on a 2.5RS-T)
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Old 01-02-2005, 05:18 PM   #3
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Run the car on the lowest boost possible, and keep backing off the J&S until it barely doesn't do anything. Then run normal boost. That's what I've had the best luck with.
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Old 01-02-2005, 10:59 PM   #4
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Like no-coast says, the basic way to tune it is to have it on while the car is NA (or 0psi boost), not EXACTLY the same thing, but close enough.

The theory would be that when the car is NA it's not detonating at all.

So, you then start the sensitivity at max and back down until the J&S isn't showing any activity.
That should be a really good starting point.

That said, I had been running mine at what I call 50%, or 12 o'clock position.
This seemed to work great, but on quick throttle transitions I would get J&S monitor activity.
I've since taken it down to 10 o'clock position.

I don't hear any pinging, so it seems pretty good.


Another, more risky method I've used is to take it to full boost (4psi in my case) in 4th or 5th gear where I can hear some pinging, then adjust the sensitivity up to where it's hearing the ping too and pulling 4-6 degrees of timing.

EDIT: Oh, and max setting is WAY too sensitive, at least from what I've seen.
That would be safe, except as the J&S retards you may see an artificial rise in EGT's, caused by too much timing retard.
At the max setting the J&S is hearing normal engine noise and thinking it's knock or ping.
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Old 01-03-2005, 12:02 AM   #5
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You want the J&S to pull timing on quick tip in conditions. Without an ECU that has tip in enrichment totally dialed in you will always see some VERY minor detonation. I would really bring the sensitivity up again to where it was pulling minor timing on tip in only. It's not catastrophic... but enough to take a good chunk of life out of your rings and possibly valves.
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Old 01-03-2005, 12:36 AM   #6
Hitokiri
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I mostly see it pulling on tip in even at max sensitivity. I run 6psi with a EBC and spool up on my t3 is lightning fast, I will definitely keep it retarding on tip in. I have alot of timing retard on boost. about 1 deg per psi and up to 2 deg per psi in some areas. I basically taper up to about 9 degrees retarded at 3800-4200 and then back out to about 5 degrees retarded by redline. I have never hearded pinging but I am new enough at tuning that I don't trust my ear. Not to mentiontion preignition that we wouldn't hear.

I tried to set it tonight by turning the EBC off (4psi) and running huge timing retard out to -12 degrees (low 10's afr on WB). Seems like somewhere around 11 oclock is what I want. I then went back to my old maps and it still didn't pull timing under high load... It was sort of a nice assurance seeing it pull timing, I don't know. I want to build a det can and really start hearing it.

Todd
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Old 01-07-2005, 06:07 PM   #7
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So, you WANT it to pull timing?

That isn't really the way it's supposed to work, IMHO.

Ideally the J&S stays silent, never a peep out of the monitor.

That would mean that your tune is good.

Having the J&S retard timing based on noises that aren't det or knock will not only cost power, but could raise EGT's.


A little off topic, but you mentioned your AFR's in the low 10's.
Is that where you typically run? and don't see much J&S activity?

I wish I had the ability to tune timing based on rpm.
But I'm just using the J&S boost based timing retard.
Interesting that you pull 2 degrees/psi in some areas. That's the max the J&S will do with it's current programming.
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Old 01-09-2005, 11:09 AM   #8
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I agree with IowaRS the J&S is not supposed to be used to tune the car. Its a safeguard, meaing it is there to protect your engine from knock, If the J&S is retarding timing, you need to go back and tune your car so it doesnt knock.

Another question, for those with a j&s (purple case) is there suppose to be a knob on the box to adust sensitivity, blue maybe? it looks like mine is broken off. My car never knocks though, cept some activity when I revmatch. I cant tell where it is set.

Jay
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Old 01-09-2005, 07:52 PM   #9
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The knobs come off easily. But there still should be a small screw with like a phillips head on it. You can just use a tiny screwdriver to adjust
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Old 01-09-2005, 07:54 PM   #10
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The knobs come off easily. But there still should be a small screw with like a phillips head on it. You can just use a tiny screwdriver to adjust.
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Old 01-09-2005, 08:26 PM   #11
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I figured that, but the botton half of the knob broken off in there, I havent tried real hard to get it out but so far no luck.



Jay
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Old 01-10-2005, 01:41 AM   #12
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You can pick it out with a needle.
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Old 01-10-2005, 10:12 AM   #13
munkis
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Quote:
Originally Posted by John at J&S
You can pick it out with a needle.
cool, ill have to try that, technical support sweet! ahha

thanks

Jay
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Old 01-15-2005, 06:45 PM   #14
Hitokiri
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lol. Well I am back from vacation.

IowaRS: I recently set up timing control with respect to boost via Emanage. I noted that I would keep the J&S retarding on tip in mainly because I have seen it retard on tip in in the past under certain conditions (with 100% sensitivity). Without full control of tip in enrichment - you cannot "go back and tune your car so it doesn't knock" effectively. You are going to have to compromise your tune in some way in order to achieve control over that tip in situation. Like you moving to 2 degree increments on your J&S even though you know that you only need that kind of retard in certain situations. I fully agree with eliminating all knock in tuning and if I had the control would always tune under the knock threshold don't get me wrong, what I meant was I am nervious about lowering J&S sensitivity as you suggested and NOT seeing it retard on tip in where I had seen it retard previouly at 100% sensitivity. Without a det can to listen to or some other assurance that I am not knocking, its hard to even turn down the sensitivity even a little bit, you know?

So whether its actually knocking or not we still need control over it, where can we find control of tip in situations where currently it will always go lean for a split second as the turbo comes to life?

It's interesting compairing datalogs from my previous tune based on MAF voltage, and looking at how MAF voltage and Boost sensor voltage compare with respect to tip in conditions. Its a good example of compromises we have to make in piggyback tuning.

Highway loads have the fastest response, and produce the worst lean spikes on tip in that I have seen so that is what I have been looking at in trying to tune around it. The boost sensor voltage obviously tracks similarly to the MAF voltage on boost, but boost based mapping is much better for highway as on the highway at moderate speeds you can see equal MAF voltage during off boost highway cruising and 2-3psi boost airflow in low gear during on boost street driving. Moving to boost based control lowered my EGTs about 15 degrees on the highway mainly because I was before pulling timing under light highway cruising under MAF based control in order to be sure that it pulled timing acordingly on boost during off highway conditions where the emanage looks at the same cell in the timing map.

Without direct control to add fuel on tip in (which is actually included in the next generation Emanage now availible in Japan - lol: they realized there is a serious tuning bottleneck there) we have to compromise somewhere in order to prevent the lean spike we see there, or the slight knock that results. Boost based fuel control on the emanage is an idea, but AFRs start going lean before the car starts into boost as my small t3 has an effect on off boost (tapped at Intake manifold) throttle response as well (I can achieve 0 vac at very light throttle).

I can add fuel based on MAF voltage on the emanage. I have datalogged the maf voltage on my car enough that I pretty much know where on my maps I need fuel in response to tip in and have concluded that there is no way to account for tip in under all conditions givin the control I have via the current function of the emanage.


So what it really boils down to is: If we want to tune our cars under the threshold of knock, and push the limits of our setup, we either need to compromise many areas of our tune to take into account situations and road conditions which we only see a small percentage of the time (tip in / decel / highway VS 1st:2nd gear / etc.)

or drop the training wheels and buy a standalone (or reflash)

For me currently, sensitivity is down to about 2 o'clock after some work with 4psi and lots of timing retard for assurance that it is not knocking. I rarely see any J&S activity save 1 or 2 bars sometimes on my monitor and the car runs much smoother overall. I have quite a bit of padding via more timing retard than I actually need on boost as a compromise for not having full control. I have a Aquamist setup ready to go in and will be playing with it next semester with the secondary injection control on the emanage. We'll see where it takes me, but I will undoubtably be back to the subject of J&S sensitivity till I can either reflash my car, or buy a standalone.

Todd
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