MS on NA 90-97 Miata: Knock sensor/correction?
 

Hello there!

I picked up a 1990 Miata not too long ago, that I eventually plan on boosting. I have a bit of a tuning background (mostly piggybacks & flash-based tuning, mainly on turbo Subaru's, with a few other platforms here and there), but am new to this platform and EM solution (Megasquirt). I haven't picked one up yet, but from what I gather, the MS seems like a fairly intuitive interface that seems like it will work just fine for boosting my Miata eventually.

To be clear, I would plan on running the Miata N/A for a while, and likely building a 1.8L block in the meantime, but from what I understand the NA chassis Miata's don't have knock sensors stock.... so, my question is, will the MSPnP accept a knock sensor? If so, does it have the ability to apply knock correction (i.e. timing retard under knock)?

From what I understand, the NB Miata's have factory knock sensors, and I was considering picking up a 1999-2000 1.8L block to start with (might as well pickup the higher flowing head while I'm at it). However, I'm not sure what, if any modifications would be necessary to the MSPnP's wiring harness in order to accommodate the newer 1.8L longblock.

Is it common for most people to add a knock sensor when tuning the 90-97 Miata's, or do most people just tune them on a dyno with a set of det cans or something to that effect? If so, where are people mounting knock sensors on the older blocks?

Please excuse my ignorance, I'm new to this platform, but very eager to learn. :)

Either way, thanks in advance!

-Brandon

Looks like I found a knock sensor that will allegedly interface with the MS:
http://www.viatrack.ca/

^^^I'm assuming running that bugger through the MS, I should be able to log knock count? Or am I mistaken?

From what I understand, on these cars, apparently most of them seem to hit MBT prior to reaching the knock threshold (someone correct me if I'm mistaken), but I'm just a bit wary, as I'm as 5200 ft elevation running on 91 octane piss water (i.e. turbo's have to spin harder/higher IAT's up here than sea level + 91 octane = more likely to det than at sea level on 93).

Actually, long-term I would be considering running E85 (ran it for ~1.5 years on my old STI, approx. 105 octane & latent heat of 310 BTU's/LB FTW!), so det likely wouldn't be an issue (couldn't get my STI to knock on E85 no matter how much boost/timing advance I threw at it, MBT was well below the knock threshold), but just curious about what people are doing with these cars as far as knock/knock correction are concerned.

Yep, we designed the MSPNP to work with the KnockSenesMS. Its output doesn't allow for specific knock counts like Subaru flash tuning does, but it will let the MS pull timing.

We don't use a knock sensor on our own project cars, though - we just tune them with a set of det cans on the dyno (had a homemade set at first, but ended up buying a really nice Phormula setup a couple years ago) to make sure the map isn't close to knocking.

Nice!

Fair enough, thanks for the reply, it's appreciated. :)

In the past, I've done a good amount of my tuning on the road, and cleaned it up a bit on a load bearing dyno, which is why I was wondering about logging knock (for road tuning where it's harder to utilize a set of det cans while making a pull, although I have seen some interesting solutions running through in-car stereo systems haha, but it doesn't help much if I'm looking at CSV logs).

Thanks for the clarification. :)

I recently installed a 1.8 in my 91 and am running it NA till I get the MS details worked out. I installed a Knocksense MS with the Bosch sensor two weeks ago. I tuned it using a detcan to accurately identify knock. I know most people tune with the Detcans and I will too, but I have the Knocksense to take care of the off normal situations that could kill the engine. A bad tank of gas, high temps or other issues that can cause knock, even on a great tune. The knock sense is rediculously easy to set up as well. Make sure you mount the sensor in the right location or you will end up picking up noise.

I made these electric det cans:

http://www.d-series.org/forums/diy-f...5-dollars.html

I wired up a harness and left the clip permanently installed right next to the bosch knock sensor. This way I can just unplug them and throw the unit in the glove box when not in use and I don't have to worry about doing anything under the hood when I want to have a listen.

They helped a ton when tuning the knocksense as well.

Thanks for the insight guys, I appreciate it!

Where are you guys mounting them at?

Get this mount

http://www.flyinmiata.com/index.php?...umber=07-36901

It bolts into the existing engine mount hole (on the passenger side) and you can screw the knock sensor into it.

Will do :)

You won't need to change the MSPnP harness, but you'll need to wire in some of the 1.8L sensors into the 1.6 harness.

Note: I've mounted a knock sensor on a 93 to the suggested engine mount, and used the sensor with my Knock Analyzer Pro. Results were awful. Definitely not recommended.

I believe the factory sensor is mounted right at the cyl. 2&3 wall below the head, I don't know if this location will work for NA's though, I havent checked to see if there was a threaded hole there.

My biggest problem with knocksense is that it's relatively "narrowband" IMO. If I tune it for high RPM knock there could easily be lower (and quieter) RPM knock that's below the threshold. If I tune it for knock between 1 and 4K then it's just a glowing light after 5K. Without something that factors in RPM noise it's not really possible to have it cover the whole range.

Interesting to hear. I suppose I might tune it with a set of detcans on the dyno and skip the knock sensor...

Actually I've been toying around with the idea of picking up a set of DW 800cc injectors on a mild turbo setup, and just tuning the car on E85, which would alleviate a large majority of my fear of knock.

Thanks for all the feedback. :)

Anybody have experience using a TurboXS knocklite on a Miata with a Megasquirt setup? It's relatively cheap and I've heard good things about their knock detection sensitivity on other cars. I've been thinking of picking up one of the FM sensor mounts and putting it on when I get around to replacing my engine mounts. I haven't been enthused by anything I've heard about the KnocksenseMS, though.