there's this local "rx7" racer dude that keeps bugging my brain about needing a "spark cut" rev limiter for a TII for drifting. i've heard it can become an issue, but i've talked to JTP, and some other dudes that are way better than me, and drive the **** out of their cars, and they said they ran stock ecu/rev limit for awhile, and nothing happened. i know everyone and their mom does not have a standalone/beeR setup, so what do i do?

my car is large street ported turbo motor, rtek 1.7 (may go 2.1) 720/550 injectors, s5 turbo, straightpipe, 2.5" full single exhaust, and it made 250whp at 8psi, and i premix. there's no O.M.P./M.O.P. (for the new guys/for the old hacks that will give me ****.)

with my NA i bounced that **** off rev limiter all day for events, and nothing happened. of course its NA, but i beat the hell out of it, and it lasted.

so is it a big deal to get a rev limiter for a TII? its my track/whenever i feel like it streetcar.

 

Stock rev cut is a fuel cut.......so are almost every other standalone ecu. Spark cut is not recommended for rotaries.

AEM and others offer both or a combination of the two. Spark cut limiters sound cool as crap and make large pops but even in SR engines I have seen cause problems by breaking rocker arms.

I would stay away from it.

 

i have 2 cuts setup on my car. a soft cut at 7800 and a hard cut at 8200. never really had a problem though but i also didnt stay with the stock compy for very long.

 

I was curious about rev limiters for drifting myself......well, not just drifting but scaring the living **** out of people and possible arson charges for accidentally lighting **** on fire with my car.

So what's with all the rx7 guys out there that ARE running spark cut limiters like bee*r, msd, etc?

What harm could that do? Really? Couldn't fuel cut give an accidental lean condition? Spark cut is safer.

 

I use a spark cut on my FD because i also run meth injection that a fuel cut would not hit. The last thing you want on a fuel cut rev limiter is for some fuel to keep going and have it lean way out. I have it set to 8100 RPM and I usually launch off of it unless i'm feeling sheepish. Its working just fine and will make the track guy duck for cover when it back fires.

 

I am just going by my experiences with tuning cars and using spark cut. I think it creates a huge pressure surge in the chambers that you can witness from the back fires. I have seen engine failures by using the spark cut as the first cut on AEM.
I am not sure exactly how the cuts work as far as spark control and fuel delivery but I know if I hit the rev limit I see my inj. duty cycle go way up or max out so I can only assume it is pulsing the injectors in some pattern.

Also Microtech and Power FC does not offer a spark cut option on Rotaries. I don't think Haltech does either but I am not sure on that I am sure other have much more information than me on it.

some people have luck with it but as many problems as I have just keeping my car running I don't want to play with it........and my PFC does not give me that option anyway. Between crappy Mazda water Jacket seals and a million year old wiring harness I have enough to deal with.

 

i know megasquirt has spark and fuel cut but i cant remember if haltech does or not and thats sad since im running haltech now. better start digging into it more

 

Haltech offers both.

 

my buddy davedge ran spark cut on his stock motor for a few years, the motor eventually blew but because of other reasons. and the thing backfired like a monster

fast forward to 3:30 and you can hear his cut twice during the section, then he spins and hits it again. awesome

 

Check out my second burnout in this video: http://vimeo.com/2095461

I hit the rev limiter right off the bat a couple times with some nice little flames.

 

If you want to limit your Rev's might as well pop a LS1 in your car. I like getting in my car and knowing I car rev it till it pops if i want

 

this has nothing to do about ls1's...
all i was asking, is because hitting rev limiter is a must in certain situations, and i just wanted to make damn sure that motor number 3 for me lasts more than 50 miles.

i know by the sound when to shift/let off, that was never the question...just certain corners are easier to link by hitting rev limit and staying at the top of a gear instead of shifting, just to downshift in another second. im coming from NA, to a turbo motor. that motor blew up in 50 miles the first night i took it out, now i have another one being built, and i just want to get my facts straight....i can't afford to go through motor after motor.

 

i don't understand why your injectors would go to max just because you used a spark cut. i'm not calling you a liar, i'm just not sure that makes much sense. if anything i would expect them to fire as usual or not fire at all depending on the system you used.

 

Same here.... I'm running the na rotary this season then going LS1.

 

same here. this is motor number 3. fresh rebuild. if it goes, then i'm switching over.

i'm not knocking the motor one bit. i'd actually prefer it over an LS1, but it just costs too much for me to get everything the way it's meant to be.
rotaries are the ****, but i have over 8k into my car, and it should be dialed, yet it's not. call it error on my part, but no ones perfect.

i finally picked up an Rtek, and all the supporting mods. the motor is done.
i'm just waiting on a wideband, SAFC, and the cash for the dyno sessions.

 

Safc? With rtek?

Might i ask why?

ALOT of tuners tell safc's worth their weight in crap.





Nobody really answered what the deal was with spark cut rev limiters on a rotary either......

I've seen videos of people with them on their 7's. That's about it. No faq, nothing.

 

Yeah im also kinda scratching my head about the rtek and safc conjuntion.

The stock rev-limiter on the rx7 should be a soft-cut ignition limiter to act more like a speed govener. When increasing the power in the car the ignition would also need to be upgraded in tandem with the other performance parts. This will also require you to use a aftermarket ignition limiter usually in the form of hard-ignition spark cut to limit your power and give you the option for launch control. Hard-spark is rough on any engine as it forces the engine to misfire in intervals, which may cause unwanted pre-ignition or detonation. Apex seals and piston rings have been known to blow because of this hard ignition cut as it also raises engine temps dramatically. Hard-spark cut finds its merits when your ignition system is upgraded to a point where soft-cut ignition limiters doesn't limit your power properly to prevent overrevolutions (which is far worse outcome all together).

Fuel cut rev-limiter to my knowledge isn't cutting the fuel 100% it forces the fuel to spray at a smaller rate forcing the engine to depower itself (limit its power). Although the chance of pre-ignition and detonation is still there, When properly tuned in conjunction with a good ECU, or if the aftermarket ECU has this feature you can lessen the chance of engine failure. The problem with this system in full for rotaries it usually leads to unwanted lean conditions and creates bad hotspots when improperly used. But very effectively useful when using very large injectors, meth/alchohol injection, Nitrous.

-WRC cars use Hard-spark ignition limiters to limit the amount of power being used but still stay in power band during cornering. (this is also known as misfire system)

-The Asparadrink RX7 built by RE-Amemiya uses a combination of both ignition and fuel rev-limiters controlled by their own EMS to maximize engine life, and keep power controlled for high-speed, high miles, endurance road racing.

To OP-
The stock rev-limiter (in working order) should be good until you see power at +400. If you do purchase a aftermarket rev-limiter do research on it and see if its a tunable limiter so you can adjust it based on your engine settings to further maximize engine life.

 

That sums it up well enough for me.

I want my motors to last a while. No thanks.

 

how would cutting all the spark cause pre-ignition? pre-ignition is caused when something else lights your A/F mixture before your spark plug. if you have pre-ignition problems it's do to something else like a lean condition or a hot spot. or using a fuel cut style rev-limiter as you have no fuel to cool the combustion chamber, only a hot spark and what is left over from the exhaust cycle.

detonation is when the A/F is lit but the flames propagation is faster then normal and max pressure in the chamber is reached before the intended time or angle of the crank/e-shaft. causing the enormous pressure inside the combustion chamber to push backwards.

this is why i think spark cut is the best. it may be a little harsh on the motor but nothing even close to the damage detonation or pre-ignition would do.

 

the reason i need an sGAYfc is because i have 1000cc secondary injectors and i need to tune them down to around 850. 720's leaned out at 5200 rpm.

 

in the Rtek you have 37% to play with....so if you set it up 720/720....put in the 1000CC injectors and tune them down below 0%....aka like -30%

that's gonna put you in the 800cc pulse range. or just get the safc

its your call. just my .02

 

i'd love to but i got the super shitty 1.7 un-tunable version. if i went 2.1 it would've been avoided. so it's either go 2.1 buy the pocketlogger pda thing, or just get the safc.
what's shitty is this is a street car, and vegas has the highest car theft rates of any city in the usa. so the less **** hanging in the cabin is less motive for people to steal. that's why i suffered with shittyy offset rota's for so long. so if i woke up to find my car on bricks, it's not as big of a deal because they're not super expensive.
luckily no FC's have been yanked for a really long time. just s13's and honda's.

 

****.....yeah...sorry upgrade to the 2.1 man! a palm m515 is like 30-50 bucks on ebay. i just got one in great condition with 80 nursing med/stuff for 99. it works great! i'm getting the 2.1 in april when i can get the ECU outta the 7.

don't need the palm in there all the time. its small enough to just put in your pocket anywayz.

DOIT!

 

Worried about getting car jacked?

Here's some ideas!

http://www.stickdeath.com/2004auto.html

http://www.stickdeath.com/2005auto.html



Personally, i like the shotgun in the air bag type deal. You go to start the car without finding the switch to cut power to a solenoid that fires a 12 ga slug and bye-bye car theif. A pressure sensor in the seat would negate them starting it from under the hood and ruining the surprise.

I'm a sadistic bastard and i hate theives. I swear to god if i cought someone stealing my car, i'd hold them at gunpoint and detain them with zip ties. Then i'd drag them in my basement, wrap some duct tape around their mouth and have my way with them for a few days before leaving them for dead in a field somewhere missing a few fingers with 2 broken legs and arms crushed from a bench vise. Trust me. Nobody would hear them scream.

I ******* dare somebody to try to **** with my baby like that. Yeah, insurance is great but teaching the bastard a life long lesson based upon pain and agony. That's gold.

 

sick!!
i'm just going to pick up a trunk monkey when i get paid. it would be sweet because since i have an FC, he won't waste anytime getting to the thief, since it's a hatchback. he'll just lurk on board, in the back.