Turbo 3.2, ms3 knock detection set up

FstTarga · 03-19-2018, 09:20 AM

I’m just wondering if any of the more adept and knowledgeable efi guys on these forums have suggestions for how to properly configure the knock sensor settings in ms3pro. I’m currently running 7psi through an intercooler and have a very conservative timing table, I’m hoping that with the knock sensor properly configured I’d be able to go more aggressive without too much risk to engine health. Thanks

Tippy · 03-19-2018, 09:47 AM

I have nothing, but I want to see your engine, turbo, and IC setup.

Are you stock compression ratio with the 7PSI?

FstTarga · 03-19-2018, 10:17 AM

Yea I’m stock compression. Made 284 at the wheels with a super restrictive air filter, I’ve removed it and made an intake with a much larger filter and my whole in boost VE table is now a full point leaner than it was lol

My set up is pretty basic I have a Precision turbo 5876 with a .82 AR, sitting on some crappy OBX headers that I’m gonna replace with rarelyl8 stuff soon and a cxracing intercooler that has had the end tanks severely modified, 600cc injectors, ms3pro running coil on plug. It’s working pretty well now and it’s pretty quick, I just want to make sure it’s quick and safe.

It has a set of 18s that I was test fitting on it in these pics but this is what it looks like now

dos531 · dos531's Garage

What settings are you looking for? The way I did it was to add a tank of 100 octane to make sure there was no knock, then monitor the knock sensor levels. Since I know it's not knocking I consider those normal noise levels and set the threshold a little above those levels. There is some trial and error involved so I err on the side of caution. Are you running sequential or batch fire? When using the knock control on batch fire it was extremely noticeable when it pulled timing. Now that i'm on sequential and have individual cylinder knock control, i cant even feel it because it only pulls timing on one cylinder at a time.

Garen · Garen's Garage

A Starion/Conquest!!! Awesome!!

I've been through 5 of them back in the day. Would modify the heck out of them, before they had any sort of serious aftermarket support. To me, it was like a more affordable 944 Turbo. Can't tell if yours is a Mitsu, hard to see the detail on the taillight from the photo.

Cool 911 by the way, and like Cory, I got nothing for the knock question. But at least the thread gets bumped up and maybe someone will chime in. Also, try posting in the turbo forum, lots of folks have had to deal with exactly what you are wanting to do.

FstTarga · 03-19-2018, 11:58 AM

I’m currently running batch injection and ignition, but it’s wired for sequential, I just don’t have a cam position sensor yet. I’ll just go ahead and datalog a bit with some 100 octane in the tank and set my threshold with that in the tank, that should work well enough for me.

FstTarga · 03-19-2018, 11:59 AM

It’s a conquest btw, it’s my friends project he’s gone through 2 of them, the first one he put multiport fuel injection on it and a 19c turbo and it was quick.

dos531 · dos531's Garage

Quote:

Originally Posted by FstTarga

I’m currently running batch injection and ignition, but it’s wired for sequential, I just don’t have a cam position sensor yet. I’ll just go ahead and datalog a bit with some 100 octane in the tank and set my threshold with that in the tank, that should work well enough for me.

Do it! Sequential made a big difference for me. Adding the cam sensor was actually really easy, let me know if you need any help with that. Also make sure you have the bandpass frequency and everything for the knock sensor set up correctly for your engine size.

dap930 · dap930's Garage

FstTarga,

Where is your knock sensor located? You will probably need to adjust the gain for each cylinder due to different distances to the sensor and the fact that some cylinders are noisier than others. Just take some easy driving datalogs of Knock #1 - #6 to see what the levels look like compared to each cylinder and adjust the gains so they are about equal. Then as dos531 suggested go out and do some hard pull datalogs with high octane to how high the levels go to set your threshold. You should be OK as long as you don't get carried away with advance in the high boost areas.

FstTarga · 03-20-2018, 01:10 PM

That’s what I figured. My knock sensor is bolted to where the stock crank and reference sensor bracket mounted. I’m planning on moving it to the mounting stud for the throttle bracket next time I have the engine out. I wasn’t I initially planning on running knock sensors due to hearing that air cooled engines are too noisy. I’ll spend some time adjusting the gain and see what happens. My timing is super conservative right now so no worries if knock as of yet, I want to run 10psi once I have it totally dialed in at 7, and that’s when I really want the knock sensor.

'76 911S 3.0 · '76 911S 3.0's Garage

You can use this site to find the approximation of your center frequency based on cylinder bore size:

https://www.phormula.com/KnockCalculator.aspx

Based on your 95mm bore, your center frequency starting point should be right around 6.0 kHz

Tippy · 03-20-2018, 01:26 PM

Very cool car. The 3.2 and 3.6 engines respond so well to boost.

Yeah, sounds like you're about 20-30hp down with the filter. I went EXACTLY through the same thing.

Had no idea how restrictive my filter until I put a larger turbo on, and it wouldn't make boost. Opened it up and it started making nice boost.

Tippy · 03-20-2018, 01:27 PM

Quote:

Originally Posted by dos531

Do it! Sequential made a big difference for me. Adding the cam sensor was actually really easy....

I so want MS3X and have my dizzy sitting on the shelf when the time comes.

FstTarga · 03-20-2018, 07:47 PM

I highly recommend going coil on plug, it was surprisingly easy to do. Just need to finish my sequential setup

Peter M · 03-21-2018, 01:34 AM

Quote:

Originally Posted by FstTarga

I highly recommend going coil on plug, it was surprisingly easy to do. Just need to finish my sequential setup

Targa,
What brand and part number for the CoP's you are using if you don't mind please? Are they smart or dumb?

Thanks
Peter

FstTarga · 03-21-2018, 07:33 AM

They are logic level coils off of a VW 1.8t they fit without having to do any extra work at all, no brackets no hold downs, nothing. Rasant products actually will sell you the coils and wiring for said coils if you just give him a call, Andrew was very helpful. Megasquirt can run them fine just set cranking dwell to around 4.0ms and set it to 3.0ms of dwell when running, I’m using 1.5ms of spark duration and am getting a good strong spark.

dap930 · dap930's Garage

MS3Pro spark outputs can handle more current than a MS3X board. So the VW coils will likely be OK with the Pro, but could be an issue with MS3X as reported on the Megasquirt forums in the past. Maybe newer VW coils have a higher logic circuit impedance now. Toyota/Denso COP's and LS2 coils are OK with MS3X, even in dual plug configuration. But other coils can overload the MS3X spark outputs, so a driver/interface board will be necessary. If I remember correctly, my LS2 logic circuit measured around 10K ohms. "xbmwguy" on the Turbo forum has run twin plug Toyota COP's with MS3X for several years with no issues.