OK I have made the decision to get the Power FC, Now what's the situation with the knock sensor. Does it use the stock one? Does it have knock sensing abilities at all? Do you have to get the J&S knock sensor. Please advise the Mahtab...

Thank you

 

it uses the stock one, like the ECU, except it will nto retard timing in conjunction with knock sensor, it will just throw a error light. Not realy any need for the J&S, but it is safeguard if you are running on the edge.

 

Has anyone actually SEEN the light? I posted a while ago trying to figure out what a "high" knock number was, because according to the manual, I should have been seeing a warning.. but didn't.

 

The Power FC does not retard the timing so get the J&S Knock sensor, the Power FC only shows a warning.

 

The PFC is the state of the arts unit. But they couldn't add a retard feature? That really sucks.

Get the J&S unit. It's worth every penny.

 

When Eric Hsu of apexi was posting to the big-list about the power FC he stated that a properly tuned rx7 wouldn't need knock retartd. After all there are many rx7's with uprgraded ecu's and the stock sensor is crap. I personally will buy a J&S after I go single turbo.

eric

 

The Power FC doesn't actually trigger the light as it states in the manual. If you watch the temp sensor display on the commander, you can see it flash every second when the knock reading is high.

-Matt

 

Maybe a properly tuned car doesn't need a knock sensor.

But, before you're properly tuned, you have to get proper tuning, and that's why there's a knock sensor being installed on my car (PFC+T78) right now. I want every single safety option and piece of information I can get while tuning, and $700 for a J&S is cheaper than $2500+seals+port+labor+downtime for a new engine...

Sounds like Apex'i was making excuses for the lack of a little foresight into making a superior product (Don't get me wrong, I love my PowerFC, it's great. But it would completely rule the planet if it just had a few minor little features added to it, even if the costs were raised by a few hundred dollars.)

 

I get an error code 05 Knock sensor?! Where is the knock sensor located at? And how do I fix it? What could possible wrong?

Thanks!

 

(1) Locations for downloading the Mazda manuals is on this site under the FD section. Get them and read. Section F which covers the engine control systems is the best to learn.
(2) By replacing it.
(3)Any part can break or go bad, just like humans get sick and/or die!

 

My knock sensor wire broke off the unit, can I still operate and run the car without it being plugged in while I wait for my replacement sensor?

 

Since it does not do anything functional, YES!

 

Excellent, I knew after reading through the post it is off and doesn't use it to retard timing but wasn't to sure if it still needed some sort of working input. Thank you sir!

 

Apexi technically did the right thing. The OEM knock sensor is pretty unreliable as a means of detecting true knock. Sometimes they work, most of the time they pick up noise. Also, the common piston method of tuning where you tune the timing by advancing the timing until it knocks and then retard it a little will not work on a rotary as you'll end up with a blown engine like that quick. So your timing map has to be in the ball park already unless you want to blow your engine (most start conservative and then advance it to where they want it).

Also, the flashing light feature for the ECU knock alert only works on JDM's as far as I know and I have seen it work.

thewird

 

Sorry little of subject ... How well J&S systems work on rotaries?

 

I believe Chuck Westbrook (cewrx7r1) has used the J&S system. He may have some input.

 

To bring back an older thread...

Which light flashes if you have a PowerFC? What is the maximum knock number it can show? I've seen 90 on the peak hold, but that's 90 out of what? I didn't notice a light.

Which J&S are you guys using?

I bought a car that is tuned with a Power FC, but I don't have the manuals. I've read a few online guides to the Power FC, but I'm always looking for more info.

 

The J&S does work but requires the sensitivity to be set very sensitive. This can be done by repeated adjustments until it reduces timing around 40-60 knock if you can make the engine do it by noise.

The problem with the earliest version which I had, when it did this, the IGL was reduced so much that IGL ended up being less than IGT which is negative split under boost.
This then caused more knock. In other words, to have enough sensitivity to make it work and save your engine, it retards IGL too much.
Less sensitivity will not have this timing problem but most likely will not save the engine.

The first RX7 version only was a one channel unit so only IGL was retarded.
A later version still had this problem. Unless they fixed/changed it, get a 4 channel version and wire it for the RX7s three channels.

 

May I ask a question? I have a T78 with a street port, 1000cc/2200cc, Power FC, Datalogit, etc. STOCK knock sensor. Sometimes between 2400rpms-5500rpms during cruising AND when I let off throttle, The stock knock sensor reading on the Datalogit AND commander can get up towards 80. Usually without driving hard, it will get up to 60-70. This also happens in PIM range P02-P10, IN VAC. Any input?

 

Any thoughts?

 

Many do this. Caused by noise in either the drivetrain, suspension, or exhaust.

I recently had to replace my transmission which includes removing the DP, MP, and catback on my single turbo.

My exhaust always had a minor alignment problem such that the front cat back hanger was very tight. This time I decide to just not use it. Since then my off throttle knock levels dropped down to normal levels.

An exhaust system that does not align well or is under stress will cause bending and shock from the engine all the way to the back. Thus it is a major noise maker.

 

I am about to replace my transmission as well. Could noisy gearbox clatter result in high knock when I let off the throttle and cruise at 2-3000 rpms?