i was just reading some old post. and was wondering what was the better investment a j&s or water injection? i was also reading that if you have a power fc that you dont really need a J&s that the power fc is better is this true? i guess what i am wondering is what to buy next. that will be an extra safeguard. also looking for around 350-375 hp on stock twins is this possiable with all my mods and the turbos at 14 or 15 lbs. of boost? thanks for any help

nate

my mods: freshly built motor by rick at rotary performance, 3mm apex seals, street port, greddy smic with pettit air duct, 1300 injectors, apexi intakes, apexi exhaust, mid-pipe, hks downpipe, efini y pipe, pettit power pulley kit, power fc, koyo radiator, that is it for performance upgrades. all safety mods have been done.

 

i'd probably go with the water injection.
the knock unit will retard your timing if it "hears" detonation, but be careful--too much timing retard will make the trailing fire before the leading and BOOM. in order to prevent this, you should probably run a trailing split greater than the max retard of the unit... but you lose a bit of power that way. and since you're trying to milk the stock twins for all they're worth, you'll need every bit of power you can get.

 

anyone else

 

The PFC doesn't do anything with the Knock Reading other than display it. It doesn't retard the timing like the stock ECU does based on the knock reading.

 

so then should i get the water injection or the j&s?

 

personally, i wouldn't boost more than 13psi, and would do water injection (using winshield washer fluid).

i would tune for around 11.4 - 11.5, then add the water inj., and set the water inj. to come on at around 8 psi and up. basically, i would use the water for insurance, and not to increase performance.

also, with the water inj. - should a boost controller fail, or a wastegate fail, the water will keep injecting - which will give you time to note the overboost, and let off the gas.

 

Are you insane? Blue washer fluid injection into your engine?

 

the one thing i like about water injection--other than the immediate detonation thing, is it keeps the combustion chamber clean! carbon builds up over time and creates hot spots--which lead to detonation.

you've seen a car with a blown headgasket, right? which cylinder was suckin' the coolant? the clean one!!

 

are you tuning it?
what kind of ems?

 

The washer fluid is actually a pretty good premix of methanol and water. As long as you have a filter inline, you can run it. A lot of people do.

The J&S is safe to use as long as the max retard is set to 10 deg instead of 20 deg. If you have it set to 20, the J&S can theoretically pull enough timing from the leading plug to cause negative split (trailing fires before leading). I've had a J&S in my car since I got it and in several boosted cars before this one. It's a good unit.

Sonny

 

Too different applications.

J&S is to monitor knock readings and retard the car if the knock goes too high. Water injection is to lower intake temps. Neither does the same thing so you can't really compare them.

IMO, if you have a decent IC, there really isn't a need for Water Injection.

 

You are comparing apples to oranges. I have both water injection and the J$S knock sensor. They are there to do different tasks, and comparing them is not really fair.

 

i think it's a fine comparison. they're both there to prevent detonation--he was just wondering which one would be more appropriate for him.

**** it, get 'em both!! just keep your split larger than the max retard.

 

I don't think that's entirely correct... how can the J&S prevent detonation when it is only activated when detonation occurs?

 

It's a fine comparison if your bored, and have nothing better to do. Otherwise, you should figure out what you are tyring to accomplish and go from there.

 

so then which one should i get as my next mod?

 

I love my J&S...it gives me some piece of mind and it lets me know when I'm pushing the envelope. It will detect detonation looooong before you have any chance of hearing it...something that is notoriously hard to do with a rotary engine...especially if you've got a loud exhaust or intake. Every now and then when it gets really hot or if things are really heatsoaked, the J&S will pick up a small amount of detonation. I either back off or turn the boost down. I don't feel as scared to push the engine knowing that I have the J&S.

In a piston motor, detonation is very easy to hear and in general, they are far more tolerant of it than a rotary.

Sonny

 

ok, prevent boom... blah

 

i thought the point was preventing boom. why doesn't anyone get it?