Fuel cut at 26 PSI. enjoy
 

quick video of my tuning/logging my new 3 bar setup.

This is for anyone who wonders what it looks like to hit fuel cut at critical moments. I had my ecu set to 1.3 bar and the wastegate wanted to run more than that. (tuning first run)

stock reman 40k miles on it
gt35r 1.06 aspec

I had that feeling once when my map sensor line popped off in the upper end of 4th . Scared me shitless

Here's a little secret.

Fuel cut saves engines. It is the last line of protection. I've hit it gazillion times on multiple engines.

^ But is it not much better to have an ignition cut rather than a fuel cut?

Fuel cut vs. ignition cut:
Fuel cut is suspected as harmful as we all know leaning out the mixture will lead to a lean burn instant failure so wouldn’t it be better to cut to spark and not have any combustion.
However the facts are fuel cut instantly drops the mixture below the combustion point, (residual fuel on the runner and chamber walls is not enough to produce a combustible mixture) where-as ignition cut does not prevent the present combustible mixture from igniting from self ignition “dieseling”.

hmmm thats interesting .. so But still seems like neither of them seem truly safe to abuse

what makes bouncing off the Rev limiter , say on my miata safe vs not safe on the Rotary , is it because of boost . or just engine design

Well i learned something today. Thanks for taking the time to clarify that. Especially at the critical boost levels, im sure thats a considerable difference.

Are you sure that gauge is accurate?

What does it read when the car is off?

Yep.... Hit mine at 25psi while dynoing. It was a little scary.

Not trusting the gauge ;-) it just looks cool for video

PIM hit 28000 in my logs so im trusting my 3 bar sensor on that one.

I watched some of your other vids about the Lambo and making money. Cool vids. Kudos man.

LOL. That slow motion part was funny.

I see it didn't take you long to figure out the PIM scale.

haha on a forum like rx7club i read and search alot before posting. I feel pretty comfortable with PIM now.

but i wouldn't suggest setting it so high, running pump gas i assume that is still well into engine breaking territory. the stout FD block is likely the only thing that saved the irons, if it was an FC or earlier it probably would have left a trail of oil behind as soon as it hit 20-21psi and be pissing out about a quart every 30 seconds from a cracked rear iron.

FD irons with the thick castings will help keep the block straight but they still can fail if you push them.

I think he has pre turbo water injection, but, you make a valid point. Anything past 20 on pump alone is really pushing your luck.

Then I need to evaluate my wastegate situation because its hellbent on 26 psi and only lowering the duty cycle to performance detrimental number seems to wrangle my boost in.

I do have pre turbo water injection.

I'm starting to feel lucky that my car is working so well at those peak boost moments throughout tuning

just lower the boost figures in the PFC, it will hit the cut sooner. even with straight water injection i have never pushed an engine that high on pump gas, if it's injecting enough, say 800cc or more it should be ok, but that's still a big if everything is tuned to handle it.

You're also benefitting from the natural progressive system of your preturbo setup. I have Brent's nozzle as well.

Are you running a 44mm WG?

yes Tial 44mm. 15 PSI spring in it. Its the powerfc boost controller kit ive had a tough time with. i cut the stock wastegate controller line from my wiring harness and didnt realize i would need it. adventures from there.

been doing EFI on turbo rotaries longer than most ... and i can tell you the rotary engine is far from a perfect world scenario.. a few points to clear up and for others to take note of and consider as it may apply to their hardware........


1... DO NOT USE THE REVlim SOFTCUT on older microtechs
it is designed for a 4cyl with non sequential fuel injection
///// it will cut half the injectors,, dropping a 4cyl to 2 cyl.. acting as a softcut
... on a sequentially injected rotary.. this is instant death

2... on a rotary engine,, the stock injector locations are considered as semi direct for primary, but not for the secondary.. on a decent,, very well set up ecu.. you will have injection dwell angle control

this is intended ( on a rotary engine ) to time the release of fuel from a far away injector to coincide its delay in making to the engine port for the window of time in which the port is open
.. on a piston engine it may be timed to instead stall for an engine cycle to cool the valve

however.. its a black art ,, and changing rpms.. changing injector type and pattern,, or position has implication on this working as well as it should...

and to make it worse.. early ecus often totally lack this feature.. combined with changed or moved injectors on a rotary engine ,, its a problem waiting to rear its head at the moment you do a fuel cut

you cut the fuel........... but this far away injectors last gasp of fuel is still potentially ( depends on how your black art math lucked in ) in transit to the engine port for the next engine cycle..........................


...........now at less than the required safe AFR,, but almost certainly still within a combustable mixture zone




3.. on a 25 + year old injector.. do you really think it shuts off nice and clean.. all day everyday...........?




4.. is your tune that good you can guarentee you dont have a wet walled manifold right up to fuel shut off point?


food for thought................ive seen what happens in real life when the dice doesnt roll your way on an old,, or not thoroughly setup ecu ... and or in conjunction with a tired injector


as for IG cuts,, they work well.. cats hate them........
but can ,, especially in a wasted spark scenario , add for an afterburn preturbo when you get the relite... have seen it sheer the to4b type shafts clean in two... .......but save the engine ...

faster ECUs with better ignition soft cuts help eliminate the issue of breaking the turbos to save the motor.

Interesting point, It really does'nt seem that cracking plates are so much of an issue with high boost/hp FD's. There are so many FD's at or arround the 500hp level,including my car, but I don't see much mention of dowelling or pinning on these engines. I run about 25psi presently on pump gas and 500cc of water preturbo. I will often get spikes to 26psi .My engine (REW) is not pinned and I run conservative ig timing (3* at 25psi). Should I be worried?

How many 500hp unpinned REW's are there out there anyway?

that statement was made before hearing it had a water injection setup. if the water ever kicks off though, you will see the weakness. if the block doesn't spit a plate, it will eat a seal or dent the rotor faces.

thats some funny shit. in slow motion