All I read about is people having boost creep and needing a FCD. I have an S5 Turbo with a bonez dp, a bonez cat, and rb catback. I make 7 lbs of boost. I thought I was supposed to be hitting fuel cut with free-er flowing exhaust? Is something wrong with my car? I doubt the PO had the wits to port the wastegate.

 

You don't want boost creep nor do you want to hit fuel cut. And there's no guarantee of hitting boost high enough to cut fuel with basic exhaust upgrades, it's just very likely. Your environmental conditions may not be right and or your car may not be in the right shape to boost that high. Either way, port your wastegate and you should be safer from boosting too high. If you don't have a boost controller that's probably why you don't see past 7psi.

 

Fuel cut happens when you hit rev limiter. Im not sure what you are talking about, do you want something to shut off your engine when you boost too much?

There are plenty of writeups on s4 or s5 stock turbo porting. s5 t2 is a lot better design and requires less complicated port job

 

Yes, fuel cut occurs at the rev limiter, but also at about 8.6psi of boost (apparently cuts fuel to the rear rotor, absolutely horrible for your motor as it is already under boost. you can blow your motor this way).

 

No, it's not that I want it, but I was expecting it. I have full exhaust and saw no difference in boost levels. And this is using an Autometer gauge, not the stock cluster. I'm worried about what condition my car is in.

 

How do you know your not hitting the fuel cut? Are you sure your not running an FCD already? Do you still have the cat on there?

 

I still have a cat. I know how redlining a car feels. I don't even boost enough to hit fuel cut anyways. Fuel cut on s5 turbos is 8.5ish. I'm only boosting 7 on my gauge which is less than stock but I have freer flowing exhaust so what's the deal?

 

Its your cat. Remove and you'll see that its restricts the exhaust. I was able to reach fuel cut on my S4 with the cat on and its the worst sound you'd ever want to hear from your engine. So I installed the FCD and expected to have all this extra boost. No dice, not until I removed the cat.

 

If your scared, port your wastegate a little. The porting is mainly done to the small wastegate hole. I havea to4 hybrid and holds boost fine

 

Yeah, stupid cats.

 

I know I would definitely want my engine to shut down if it makes too much boost. Too much boost mixed with not enough fuel is the biggest killer of turbo rotaries!!

Fuel cuts can happen for various reasons. Over-rev and over-boost are two major ones. I think S5's may fuel cut if the ecu throws some codes for things like the omp. Fuel cuts are there to minimize dammage to the engine when something is not operating within OEM spec.

I have never heard of fuel cut blowing up an engine. Fuel cut means NO fuel is injected in, to detonate and blow up the engine you need some fuel to be injected in.

There could be many reasons why you are boosting lower than stock. The cat could have a an effect. As well the actual spring rate on a S5 turbo is about 5.5lbs (at least this is the case with my car), so whatever controls it to open later may not be working quite right. Your air filter might be your source of restriction too.

It sounds like on a whole the car is running pretty good so I wouldn't be too concerned about the lower boost. If you want to up the boost get a controller and a FCD (although your SAFC could have one or both of these built in, i'm not familiar with the spec's of SAFC's).

 

With the rear secondary injector firing at the same time as the primary, there could be fuel left in the mixture for the next combustion cycle. You could also get fuel from a leaky injector. A lot of things can happen at higher RPM under boost, too. Maybe you've never heard of it, but I've heard a lot of the more informed members here talk about how dangerous that system is.

 

SAFC only adds or removes fuel. I plan on getting an AEM Tru boost and a FCD and taking my car to a knowledgeable tuner to Boost 10psi out of the stock turbo on the stock tmic.

 

You will end up losing power with more boost with the stock tmic. You will jus be pushing hotter air into the engine. You will only see more power if you switch to a fmic at higher boost levels.

 

how do you think your tuner will be adding fuel? not with the stock ECU and an FCD... You up the boost, you need to up the fuel. END OF STORY.

You NEED some type of fuel controller. AEM truBoost will do NOTHING for you except help you blow your motor.

Also, the stock TMIC is more of a heater... You have lots of choices besides FMIC, they all have advatages and disadvantages over the other...

 

Correct me if im wrong here, but he has lower boost than stock because hes on the stock wastegate spring and when he changed his exhaust, that made less restriction, lowering the boost...?

And I thought fuel cut on the S5's was at 12 psi? not 8.5...

And the stock top mount is going to do nothing good for you, your just going to overheat your motor and blow something because of all the hot air.

Like stylEmon said, you need more fuel, not a boost controller. Your just going to blow something. Change to bigger injectors or upgrade your fuel pump. Something to upgrade the fuel system.

 

*fixed

Well said!!

I am pretty sure 8.5lbs is stock on the S5

 

Possibly the fuel lines and fuel filter as well.

A great investment for not very much money (except the injectors...)

 

Try using a wastegate restrictor on the wastegate can. This will allow you to build the boost faster, it will not increase your boost.

You don't want a restrictor bigger than .010".

 

THe s5 has a setup in which it is computer controlled to boost to 7lbs. The spring on the wastegate is set at 5.5lbs. So basically it has a factory boost controller.

The reason you are not hitting fuel cut off is cause your wastegate can handle the extra exhaust going out. Now if you were to remove the cat then you prob would hit fuel cut.

Fuel cut can happen at any (higher) rpms not just redline.
Sounds like your car is running fine and there is no need to worry.

 

I posted some pics the other day. They may help explain some things about the turbos.

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/twin-scroll-removal-746913/page2/