I have a J&S for my 2000 Honda Prelude. It is a 'version 2' with the MAP limiter, and unlike the ones featured on your website, this unit has 6 DIP switches on the back instead of 5. The car has a Jackson Racing Supercharger installed on it.
When the unit is hooked up, power below 5000 rpm suffers heavily. I've verified this on a dyno. The unit is not pulling timing for knock when this
happens. I know that knock control is working because on rare occassion I have seen the unit pull timing (I have the dual monitor). These instances were repeatable and corrected with timing adjustments (I have programmable management).
When the J&S is bypassed, this power problem below 5k rpm disappears.
I would like assistance troubleshooting the issue, and if it appears there is a need, I can send the unit to you for inspection. I am not the original owner of the unit, and have had it for several years, so I do understand that the unit would be out of warranty.
Looking forward to your response.
Here is John's response:
Quote:
David:
How do you have the boost retard knobs set? How much boost are you running?
The unit also has RPM retard to prevent tip-in detonation. The max amount is selected with switches 3 and 4. See table below:
3 4 Retard
up up 8°
up dn 6°
dn up 4°
dn dn 2°
The RPM based retard starts at 2500 RPM and ramps up to the selected max by 3500 RPM. At 4000 RPM, it starts to re-advance, reaching stock
timing by 5000 RPM.
Below 2psi, no RPM retard. The retard increases with boost, reaching the selected maximum above 5psi.
John
I've misunderstood the purpose of switches 3 and 4, thinking they set the retard range for when there was knock. I've been running 3 and 4 both UP.
Note to J&S users: this feature is INDEPENDENT of the boost retard start and rate knobs. If you have programmable management, you do not need this feature at all and should run both switches DOWN. Even with them both down there is still a midrange timing retard up to 2°. I am trying to find out from John if this feature can be disabled entirely, cause I don't need it!!!
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Last edited by sharkcohen : 02-02-2005 at 11:17 PM.
Well, I guess I'll just whore my own thread. I got another email back from John, the RPM retard can indeed be disabled easily:
Quote:
David:
> I really don't have a
> need for this feature, is there a way to disable it?
>
>> Below 2psi, no RPM retard.
Never let the unit see more than 2 psi. Disconnecting the hose at the back
of the unit will force it to see a constant 0psi.
The knock detector is turned off with more than 5 inches of vacuum, so
simply disconnecting the boost line from the unit may cause false detections
on decel and light loads, due to piston slap.
You could put a "missing link" check valve on the boost line to the unit, so it sees vacuum to turn the detector on and off, but never sees boost.
John
I'm going to get some sort of check valve for the vacuum line to the unit.
I went ahead and set switches 3 and 4 down for now, and it runs so much better. I have now both the J&S and the wideband back in the car. The wideband is semi permanently installed now, with the sensor in the stock primary O2 position and the stock ECU being fed the narrowband simulator from the wideband controller (Tech Edge v1.5). A/F looks great throughout the RPM and throttle ranges, and the J&S is not retarding timing for knock. I'm running 9 psi. Despite running the stock exhaust and header (along with Random Tech cat) and my latest intake setup (I'll post pics later), the car feels to me just as strong as it did with my ridiculously loud 2.5" custom exhaust.
So I took the OEM check valve that was used for the intake resonator butterfly and installed it on the line to the J&S. Low end is even better now. I think it's getting time to put this thing on a dyno again, just to see what it pulls. I've always been sure that I could have broke 200 whp at 6 psi if I didn't have that damned low end problem. Now I don't have the problem, and I'm at 9 psi.
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Last edited by sharkcohen : 02-04-2005 at 01:39 PM.
Ok, don't use a check valve on the line to the J&S. Don't run it without a vacuum line. I'm not sure why, but it is not behaving as John described. He is saying that the knock detection will remain intact. Today on the way home from work I experienced some low rpm detonation, and the unit was not doing ANYTHING about it. I pulled over, removed the check valve from the line to the J&S, and when I recreated the conditions under which I got detonation, the knock LEDs became a ****ing light show.
I always thought i had a version 2 because it has a map limiter, but i just pulled the unit from the car (stored for winter) and i relized i only have 5 switches w/map limiter. When i dyno'd last year i had a horrible drop in power around 6300- to redline. The J&S was pulling some serious timing about 4 to 5 led's on the dual monitor. So now with this new news i wonder if i can solve my problem cause my car too has a bit of hesitation down low. Well i wonder if this new info applys to me but heres my settings. Sensitivity around 1 o clock ( to high??) Switches-1 up, 2 down, 3 & 4 up, and 5 down. Boost start- all the way clockwise and retard rate- all the way couinter clockwise( so the function is disabled?). Last i have the map adj. all the way down off so 7 oclock. Does this sound correct and should 3&4 be down? Also my unit is identicle to the second pic on J&S's site! Thanks guys
I always thought i had a version 2 because it has a map limiter, but i just pulled the unit from the car (stored for winter) and i relized i only have 5 switches w/map limiter. When i dyno'd last year i had a horrible drop in power around 6300- to redline. The J&S was pulling some serious timing about 4 to 5 led's on the dual monitor. So now with this new news i wonder if i can solve my problem cause my car too has a bit of hesitation down low. Well i wonder if this new info applys to me but heres my settings. Sensitivity around 1 o clock ( to high??) Switches-1 up, 2 down, 3 & 4 up, and 5 down. Boost start- all the way clockwise and retard rate- all the way couinter clockwise( so the function is disabled?). Last i have the map adj. all the way down off so 7 oclock. Does this sound correct and should 3&4 be down? Also my unit is identicle to the second pic on J&S's site! Thanks guys
You've said quite a bit in only a few words, let me try to address each issue you brought up. 'Version 2' units include the MAP limiter. Some have come with 5 DIP switches, some 6.
If the J&S was pulling timing in the high end, and you know this because the knock LEDs were lit, then the J&S is doing its job, pulling timing for something that it hears. What I am addressing in this thread--the RPM retard function associated with switches 3 and 4 and their impact on timing between 2500-4000 RPM--does not apply to what you have described.
However, if you are having 'hesitation' in the low end, it could be related to how you have switches 3 and 4 set. It could also be related to your tuning. Do note taht if you have both these switches up, the unit is pulling up to 8 degrees of timing above 5 psi between 2500-4000 rpm.
Sensitivity at 1 o'clock could be too high. With it set that high, it may be causing the J&S to pull timing in the high end as you described. But, it could also be that you were indeed experiencing detonation. What I can tell you is that most people, including me, set the sensitivity around 10 o'clock. I leave it up to you to choose where to set it.
Do you have the MAP limiter wired up, and do you want to use its function? If yes and yes, then you need to calibrate it properly. There are instructions on the J&S site on how to do that.
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Last edited by sharkcohen : 02-16-2005 at 12:06 PM.
Thanks Shark! Yea i too have a hesitation down low so ill give 3 &4 a try in spring and as for my high rpm situation, i was making sure it wasnt related to any of the other switches being wrong. As for the Map limiter on the J&S, no its not wired up.
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