Rx8 Knock sensor connector and placement
 

Hi guys. Im upgrading to the Adaptronic Modular and would like to implement the knock sensor. I bought 2 Rx8 knock sensors and bolts, I still need the connectors for them, where can I find the connector? Also what housing are you guys monitoring knock on? This is a 13b-re motor with a bw efr9180 ewg turbo.

Jose Nieves

i have run two of them for a few years, one on front and the other on the rear housing.

i don't think it makes much diff as to which rotor if your ECU has a good knock system.

as to mounting... i took a long bolt that fit into the housing, reduced the diameter (bench grinder) where it fits thru the knock sensor hole (which is smaller) and tapped it for a nut.

someone else apparently enlarged the hole in the sensor w a Dremel.

Howard

Where did you purchase the connector?

I would caution a little more understanding of the sensor you're using and the control system implemented by the ECU before putting much faith in what you're trying to do.

https://www.rx7club.com/haltech-foru...elite-1096695/

Are you staying that the rx8 knock sensor is no bueno?

I'm saying if the sensor has built in filtering that you're unaware of, you'll have issues.

In that case, what is your advice on experience?

I have no experience with the RX-8 sensor. So my advice is to proceed with caution. We use a broadband sensor with the systems we use because they have proven to have capable filtering of their own. This ensures we're not fighting a sensor that has built in filtering centered around an alternate frequency. At the root of my advice is to purchase your EMS and parts from someone that has been there and done that.

I may be able to get the connectors for the 8 sensor. Seems like we ordered one for an OE replacement harness we did a while back. I'll check into it today and get back with you.

I believe the RX8 knock sensor uses the standard Denso connector. I have a sensor and some new Denso style connectors. I'll try to double check this weekend that it fits.
The RX8 sensor has a bore for an M8 bolt.
The S5/FD housings use an M10x1.25 bolt. You can either turn down and die an M10 bolt like HC suggested or drill out the sensor.
I've personally seen an LS1 car using LS2 wiring and knock sensors drill out the OEM sensors and have no ill effect. I'm not saying the sensors would necessarily overlay 100% with an undrilled sensor, but on a piston engine we were able to see were the car had too much timing and retarding it a degree or two lowered the measured knock reading substantially.

I bought 2 LS2 knock sensors to use on my car for $8 each on RockAuto. OEM Denso sensors almost identical to the RX8 sensors. The problem I see with tuning a rotary with a knock sensor is finding out what is a safe threshold for your sensors and engine. The knock values are pretty relative and not something you can say “keep it under 50” ect. A knock count of 50 on your engine may be 100 on another ECU and knock setup or 20 on a third setup. I would just stick with conservative timing, rich AFRs, good spark, and ethanol or AI.

I found connectors for the rx8 sensors. Volvos happen to use the same knock sensors. I got them in this morning to the shop. The part number for the connector, thru Volvo, is #8676256.

So, now I'm questioning the use of the rx8 sensors. Seems like I should use something else.

You'll have trouble finding a M10 wideband knock sensor.

I'm talking more about the frequency of the sensor......

my guess is the ECU knock system specifics may have a lot to do w whether the RX8 knock sensor will deliver the data needed.

i run a ViPEC V88 and it works very well. i specified the CPS range on my ECU. around 3500/4500. i could also specify all ranges and haven't as yet.

Howard

Thank you Howard! That makes me feel better! BTW, how is your car running?

So you know for a fact that the RX-8 sensor has no in-built filtering and that Mazda speced the sensor and ECU to monitor the first order frequency? Because if you're incorrect you're monitoring a frequency that the sensor is actively filtering out.

Both the modular and the 1280 do knock windowing by engine angle, which is MUCH more useful than filtering by frequency.

The thing is that knock just excites the engine so what you hear is the natural frequency of the engine. You can make pretty much make the same sound by hitting the side of the engine with a hammer. Some workshop manuals says to do this to test the knock sensor. So everything that makes noise like valve noise on pistons etc makes noise in the same frequency band. The trick is that knock usually happens between a certain range of crank angles, and if you know that window for knock during that angle you can eliminate a lot of background rubbish. Engine-synchronous windowing is what you need to do.

Modular does also have variable filters (you set the high / low frequencies).

A spectrum analyzer has not been added yet, but can be.

You'll need both, and more, to compete with the best in the business.

care to elaborate on the more? im in the market for a new ecu platform. im thinking an adaptronic e1280s for myself... or the haltech... it's hard to get sound adivce on which way to go.
knock control is a big factor, as well as being able to tune to the speed sensor on the turbine.

Knock will produce a noise within a given frequency for any engine. That part is predictable. So the knock control system will first listen to that frequency and filter out everything else as noise. This is a simple band pass filter. A better system adds crank windowing. This looks for that given frequency only during a specific window, in degrees of crank rotation, where knock may occur. Such that, if noise is detected outside of the crank window on the same frequency as knock occurs in your engine, the knock control will discount this noise as spurious and ignore. Can't be knock if it occurs at BDC.

Those are the two basic filters. Where it gets fun is when you have an exhaust system that resonates on the knock frequency through a 1000 rpm band and you'll have that noise available through the crank knock window. So how do you filter that out? Some do it well, others not so much. Syvecs/Life Racing, for one, has a proprietary background algorithm they're not eager to talk about. Buy their system has proven to be incredibly capable. Haltech has a front end programmable solution.

Lastly, at 6000 rpm, each cycle in a rotary occurs every 10ms. So 100 times per second you have an ignition event. If it takes your system a half second to process the knock signal and initiate ignition retard as a counter measure, you've enjoyed 50 more ignition events in the mean time and have likely already scattered your engine. A knock control function worth a mention on the spec sheet needs to be FAST. This is the primary reason Haltech never offered knock control on the older ECUs. They knew they were hardware limited. The best systems have a dedicated processor just for knock control.

In short, it's like a lot of ECU functions. It's easy to put a check box on the front end and a line on the spec sheet. It's another entirely to make it work correctly.

You get good advice from guys that have been offering engine management support for over a decade. ;)

Rgarding turbine speed; Syvecs and Haltech both offer that option. Syvecs has some great options, developed for compressor limited race applications, that allow you to optimize performance of small compressors based around shaft speed, inlet and outlet pressure without overspending the turbo.

the idea is to use two EFR7670 sequentialy but tune to use the first one to the point it's just leaving 75 percent efficiency, and then add on the second one. i could manage do it it by rpm, but it would NEAT? to have the ecu doing it with the speed sensor. it would be even neater to just upload a compressor map to the ecu and it be able to use it.. which is what i would be doing more or less. the speed sensor/map/emap would be the efficient map would it not...

sorry for starting to derail this thread.

"So you know for a fact that the RX-8 sensor has no in-built filtering and that Mazda speced the sensor and ECU to monitor the first order frequency?"

a fair question.

i rolled the dice and find that my Bosch/RX8 sensors work very well.

lots of good info here on a very important topic. i especially appreciate the fact that there is really only one response to knock and it is ignition.

John @ J&S Safeguard (knock systems) suggested that action may need to take place "on the next rotor face."

since it has been noted that at 6000 you have about 100 rotor faces per second cutting boost or fuel is not the answer.

electricity/ignition, however, functions at the speed of light. John's tech papers seem to indicate his system works on the next compression stroke.

given the large combustion chamber pressure the rotary can generate, the identification and response to detonation is very important. fortunately the newer generation of ECUs can be of great help.

i suggest anyone buying a new ECU understand what a proper knock system is and place it near the top rung on the preference ladder.

Dont know if this helps any one understand.

very good video by the way.

highly recommend watching the excellent video linked in post 23. it certainly shows well for Haltech and is a comprehensive treatment of the modern knock system which is necessary, IMO, for our turbo rotaries.