bitchM0VE

Being MS, there's more than one way to do it. I bought a "KnockSenseMS" from Boris. It reads the knocksensor directly and spits out a ground to MS if it see's a knock event. The KnockSense is of course adjustable to setup the sensitivty and is tuned by Boris to the bore of the engine. Works well when installed. A few miata folks have hooked up det-cans up and used them to adjust the sensitivity of the unit. I'm gonna do that probably. MS2E has a slew of settings I can play with when it sees knock. Like first knock, retard X, then every subsequent knock retard Y up to Z degrees. Then you can set it to remember the cells it changed till the unit is shut off, or you can set it to aggressive where it will slowly increase the spark back in those cells. Closed loop ignition tuning.

Tom-Guy

Sounds like an overly complex system that can cause trouble. I don't mind a KS that pulls a little timing, but in truth it shouldn't vary significantly from the timing figures derived from tuning. If it has to pull a little timing frequently, or a lot of timing at any point, I'd want to know so I could inspect/fix my ----.

Two thoughts. First is the KS must be designed for the bore as well, I know some people were hopping on the GM units for various reasons. In truth they (IIRC) were fairly broad spectrum units but there's still a good chance of putting the wrong one on the wrong engine. Second, a lot of Nissans and Mitsus die because they go into knock feedback loops where detonation yanks timing, overheats exhaust valves to the point they become hotspots and preignition starts. What the engine needs is to be shut down and cooled, but what happens is the driver continues to beat on the car until it comes apart because they don't know better.

Hey, I just recently got my laptop back from repair and don't have my bookmarks anymore (I deleted them to prevent identity theft), but doesn't boris do the low-Z injector driver boards for the MS, too? Those are freaking great for use in staged injection setups on most anything, instead of $150 plus ship and enthusiast can put together their own for $40.

bitchM0VE

User assigns authority, step size, RPM range unit is active, sensitivity, etc. It's all configurable. The knock sensor I'm using is the OEM mazda unit that came on the car, so I would imagine it's setup for the engine. It's new too. And I already said the KS was setup for the bore, 83mm.

If I set it up, it would only have say 5* of authority. That's not a ton, but it's some. If, say, my AIT sensor died so I lost AIT based retard and simultaneously something blocked my IC during boost, and I knocked, it pulling up to 5* to keep it from knocking will be beneficial. Though that will increase EGT's, it's still better than detonation. With the WI, EGT's will be in check anyways. I can also log knock events.

I think Boris does that board, but not 100% sure. Friend of mine bought a couple of them unassembled for 20 each. Not sure where he got them though. FWIW, I'm running low ohm 550's with my MS2. It supports low ohm injectors. Only thing was it did cause some noise (hence the need for a injector driver board), but I simply lifted the 12V+ feed wires on the TIP125's that drive the injectors and ran that back to the injectors. So that when Lens's law kicks in, it's got a loop that's outside of MS. Works very very well.

Tom-Guy

Five degrees retard is plenty. If the car is tuned correctly you have a 3-5 degree (on average) buffer between best power and detonation. Any more and there's something wrong. Can you flash a CEL or other warning for excessive knock count?

Also, don't expect WI to protect you from pre-ignition. The chamber is cooled so detonation, and some causes of preignition, are curbed but the temps across the exhaust valves remains constant until you get into the sort of water cooling where you can drain the cooling jacket as it isn't needed.

bitchM0VE

t
The KnockSenseMS comes with a super bright LED driven by the KSMS that lights when it sees knock. Of course this output could be adapted to light up whatever you want. I just use the LED it came with.

I've never used WI before. But from my research, it does lower EGT's. Depends how much you use, but say 10% by volume of water to fuel is gonna remove a lot of heat. It slows the combustion process, shifting PPP a few degrees. That's a safety cushion.

Tom-Guy

Lowering EGTs is different from the temp of the exhaust valve. Read some of Ricardo's work on water injection, the temp across the exhaust valve guide remains proportional to the engine's specific output until you inject massive amounts of water.

Smith-02

this thread has more tech than h-t does period

bitchM0VE

http://www.rbracing-rsr.com/waterinjection.html

That guy? I don't see how you can superheat a liquid, remove heat from the control volume and reduce heat going out of the control volume, and not reduce the temp of the exhaust valves. But I'll keep reading.

Hitchhikkr

You forgot about the uncontrolable knowledgeabilities. We has them.

Tom-Guy

It's either mentioned in the NACA papers they link to, or in Ricardo's High Speed Internal Combustion Engine which I have loaded here.

You might get the face of the exhaust valve a little cooler, but the simple fact of the matter is that the entirety of the exhaust's thermal mass passes right across the valve. There's a direct relationship between engine longevity and exhaust valve guide temps.