87 tii with 3"dp and cone filter and stock WG and stock catback.

under WOT in first gear it makes 4-5lbs by 3kRPM and hits fuel cut at 5k rpms or so.

is that normal? i just got the car and people keep telling me that is making boost faster than normal. Could the turbo be upgraded? would that make it go slower or faster?


I keep hitting fuel cut even with my FCD! its a hks FCD and no one knows what to set it to.

 

Well first thing is first. YOU DONT WANT TO BE HITTING FUEL CUT. I mean thats the point the engine goes caa-boom. Get that thing tuned right. You should be gradually continuing to boost not hitting fuel cut, thats really dangerous. As far as boost, one of the main reasons its creating boost so fast is 1. a 3" dp and 2. you have a stock wastegate. Once you get that FCD tuned you should boost to 12 or 14 psi or so but you need to get that under controll very quickly.
Turbo's must be modded in sequence so that you dont risk blowing up your engine.

 

i have a s4 turbo on the way with "grosely" ported WG as he put it and ported exhaust runners. im going to send mine in to get upgraded.

so no one knows what setting to put this thing on? the hks fcd that is.

 

When does fuel cut go kaboom? It's not much different then ignition cut. I use it as my rev limiter and have hit it multiple times.

 

That is not a very good idea.

 

Explain please???

 

The ENGINE can go KABOOM. When you think about what's happening in the engine it kinda makes sense. He says hes losing all power after 5k so basically his fuel is being cut at this high rpm with about 4-5 psi worth of boost in his rotor chamber with no fuel. Sounds like it'd be kinda dangerous to me. I mean its better to have more fuel there than less and risk detonation.
An ignition cut wouldent be as bad as a fuel cut, in my opinion. But why cut anything at all is my point.
As far as tunning that HKS, i have no clue i dident even know they made a FCD...

 

Well it goes from "aaaaaaaaarrrrrrrrrrrrgggghhhh" when it's under power, instantly to "yoink" no power.. that's one way (I think), and another is I think it cuts fuel but it might still be able to fire something, and it runs super lean, and *blam*..

don't quote me on either, but I just know fuel cut has killed a few engines.

 

But there is no fuel. Fuel is what goes kaboom. So your lean actually your only running air. Dunno, I'm not worried. THe reason to cut something is 1st, 2nd gear, lightweight flywheel, and T4=9k before you can think about shifting.

 

there is still fuel in the intake runners for a rotation or two after it cuts. That means it's extremely lean for a second.
And I don't know about the RX-7 turbo, but my MR2's turbo will produce 13-14 psi in just first gear.

 

Goog thing I am extremely rich. Back to the question your turbo will spool quit fast with those mods. Sounds right to me. I am a moron when it comes to these wacky rotary engines though!

 

Yeah but where talking about 2 diffrent kinds of KABOOM's. One is the kind that happens naturally during combustion which is totally normal. The other is the kind of detonation that im talking about which is the uncontrolled kind that is a lot more powerfull and can creat pressure 10 times that of during normal combuston, which can blow out seals. This is what he should be afriad of. It sounds to me like that HKS FCD is a pos. I would throw it out and get one that is more common and we would know how to tune

 

When fuel is cut to one of the rotors you will run lean and risk an incredible chance of blowing your engine. If you don't have an FCD then you should not be breaching 8 or 9 psi otherwise you will risk destroying your engine.

 

yea thats why im asking for help tuning this thing.... i dont want anymore runs to "test" it.

im waiting to hear back from the guy on here that makes them... so i guess ill take it easy till then.

 

When the injectors are cut, no fuel at all is injected into the rear rotor. No fuel = no combustion. You can't have a lean condition if there's no combustion.

Based on people's shared experiences with FC's, there does seem to be some risk of engine damage when repeatedly and frequently hitting fuel cut, but this is not due to lean condition.

 

You think there's no puddling of fuel in the intake runners when you're running under boost? Hmmm?

Do you honestly believe my being stronger or faster has anything to do with how strong or fast I am in this place? Do you think that's air you're breathing? hm...

ANYHOW.. there's going to be some fuel left over somewhere in the system when it cuts fuel at full throttle.. that's why it can run lean.

 

If you have fuel puddling in your intake runners under any running conditions, you have some serious problems with your engine.

Is everyone forgetting that the injectors do not flow all the time? Their pulse corresponds to eccentric shaft rotation, and thus to airflow. The injectors are not on all the time.

The injector pulse is cut, so their is no flow of fuel for that specific combustion chamber. There is no fuel, and thus no combustion.

 

Hey its Scathcart!!!