boost cut

[bountykilla0118]

Really they are the samething just people say boost cut or fuel.... what people call boost cut isn't really a "boost cut" its really spark cut. The ecu see's a danger area and pulls the timing which cuts your spark while the same amount of fuel that was/is being dumped at the time is still present so the engine runs rich instead lean for a momment to keep the engine from detonating

 

[tissimo]

iirc it actually cuts the fuel injectors rather then spark, thats why the dual term of fuel cut or boost cut..

Best way to raise fuel cut is to get a AFC. The cheapest route is to get the Greddy BCC or HKS FCD. But watch your boost. Dont over boost too much. I wouldn't run more then 15 psi without having the air/fuel ratio checked.

 

[The Reaper]

thank you for proving my 1st post justin

 

[drewgo]

just grab a boost cut defense device and wire it to you ecu. its about 50 used.

I got 2 of them.... I am getting ready to post up for sale...
Send me a PM if interested.

 

[AZN MK3]

iirc it actually cuts the fuel injectors rather then spark, thats why the dual term of fuel cut or boost cut..

Best way to raise fuel cut is to get a AFC. The cheapest route is to get the Greddy BCC or HKS FCD. But watch your boost. Dont over boost too much. I wouldn't run more then 15 psi without having the air/fuel ratio checked.

but i do have a afc and i dont really get how or to what i have to set to prevent the boost/fuel cut... so i was wondering if you could tell me how im suppose to do that, that'll be great... again i have an afc neo... and i've read the damn thing like about a dozen times and still dont get how its suppose to adjust my boost/fuel cut...

ok so your saying my afc neo can adjust my boost/fuel cut higher than why too should i but a
FCD if it already controls it???

 

[bountykilla0118]

iirc it actually cuts the fuel injectors rather then spark, thats why the dual term of fuel cut or boost cut..

Best way to raise fuel cut is to get a AFC. The cheapest route is to get the Greddy BCC or HKS FCD. But watch your boost. Dont over boost too much. I wouldn't run more then 15 psi without having the air/fuel ratio checked.

I disagree ...... If it cuts the injectors then you would run leaner and that would defeats the purpose of it. Since "boost cut" is to keep your motor from detonating ie running too lean. Every time that I have hit boost cut or fuel cut I spat out a small cloud of black smoke meaning I went very rich.

 

[tissimo]

but i do have a afc and i dont really get how or to what i have to set to prevent the boost/fuel cut... so i was wondering if you could tell me how im suppose to do that, that'll be great... again i have an afc neo... and i've read the damn thing like about a dozen times and still dont get how its suppose to adjust my boost/fuel cut...

You need a wideband or to dyno your car to give you the air/fuel ratio. Once you have that ratio adjust the AFC so the ratio is ~ 11.5 in boost.

Honestly though, take it to a local tuner and have it tuned for you.

I disagree ...... If it cuts the injectors then you would run leaner and that would defeats the purpose of it. Since "boost cut" is to keep your motor from detonating ie running too lean. Every time that I have hit boost cut or fuel cut I spat out a small cloud of black smoke meaning I went very rich.

If the injector doesn't spray fuel, then there is no Lean condition. There is just pure air in the cylinder.. nothing to detonate.

The ignitor output for the tach is directly affected by the coil triggers by the ecu. If the ecu doesn't fire the coils your tach will have a false reading and will jump around. With aem and an ignition cut revlimiter, when you kiss it the tach will fall to ~ 1/2 the rpms. Same goes with a 2step with ignition cut.

Not to mention the dumping raw unburnt fuel into the exhaust is a bad thing for the catalytic converter. I'm sure the Toyota engineers wouldn't do something like that

 

[supraracer49]

Yep, If it cut spark then the engine would flood and stall rather than just cut out for a sec. I am BPU running 11 psi stock with a SAFC Neo and 255 walbro as well. They really don't do any good if you don't have the car tuned. I just ordered a Innovate Motorsports LM-1 for my car. With that u can tune ur AF's to be around 14:1 out of boost and between 11.5-12.5:1 in boost. Once I get mine tuned I might try to up the boost to 15 psi for the track and tune the fuel to those specs. you would be suprised how much you can raise the boost with injectors, AFPR, AFC, and a wideband tune.

 

[Bri-Guy]

Guys, I am having a tough time believing that this discussion has gone this far without anyone really mentioning the simplest way to increase the boost level where you encounter fuel cut. Lexus V8 AFM & 550cc injectors. This is easily the most popular, well documented method that keeps all of the benefits that the car comes with stock. Fuel cut is a good thing after all, it keeps you from melting expensive things when running too lean. This is the most bullet proof way to go for anyone without running the risk of damaging anything unless choosing to go with a standalone unit, but that may be more technical, and expensive route to go for some. Here are 2 good links. The first describing the way one guy did it, and a bit of the theory behind it, the second is by Reg Reimer, the guy who came up with the idea in the first place (some sections are a bit technical, but is a very good reference). I have heard of many people using the Lexus AFM w/o the Sonic special screw, but there may be some minor issues here (stalling, backfiring, etc). Then, of course the have a good base to add on additional mods/controllers in the future.

http://rob.carlile.home.mchsi.com/lexus/lexus1.htm
http://suprasonic.org/lexusriemer/lexusnotes.html

Definitely check these out. Will be definitely able to move up to higher levels of boost with NO negative effects. And keeping fuel cut protection for your engine.

 

[bountykilla0118]

I think you are missing the point of thread....... Tuning to the stock 440's with a SAFC to increase the boost cut limit.

Most people are fully aware of the Lex AFM and 550's but that’s not what’s being aimed at. The stock 440's have been proven to flow enough to support the mid 400rwhp range. If something isn’t broken don’t fix it and I understand what preventive maintenance is but it is simply over kill to use the Lex AFM and 550 injectors with a CT26 period.

 

[Dylan JZ]

WTF is up with the 7M BS above?? ^^^ GTFO

 

[Bri-Guy]

My bad, Yup U R right, I missed the point. Got lost using the new posts button. Did't notice the section I was in.

Also, agree that my comments about AFM/injectors are probably overkill and more than required as far as increasing fuel cut point.

Carry on.

 

[Ric]

Whats with all this mis-information?

First off, you don't "tune" boost cut away with an SAFC. The SAFC fools the ECU thinking it's getting more air or less air, making the fuel injectors put out more fuel, or less fuel. When you install 550's on a stock 1jzgte ecu with SAFC, you tune out 33% fuel at idle, and with stock twins, almost 33% minus fuel at WOT.

What does that all mean in the long run? Using the SAFC you just fooled the ECU to think it's getting less air then it really is getting. You are not raising the boost cut, you just fooled the ECU to think it's only at 14psi when it's really at 16.

SOOO What does that all mean? It means you just retarded you engine timing and any gains with the extra 2psi just went out the muffler as unburnt fuel.

You are not going to blow the engine up running more then 14.7 PSI on a BPU 1JZ-GTE. It will handle over 20psi just fine on stock 370's.

 

[tissimo]

Whats with all this mis-information?

First off, you don't "tune" boost cut away with an SAFC. The SAFC fools the ECU thinking it's getting more air or less air, making the fuel injectors put out more fuel, or less fuel. When you install 550's on a stock 1jzgte ecu with SAFC, you tune out 33% fuel at idle, and with stock twins, almost 33% minus fuel at WOT.

What does that all mean in the long run? Using the SAFC you just fooled the ECU to think it's getting less air then it really is getting. You are not raising the boost cut, you just fooled the ECU to think it's only at 14psi when it's really at 16.

SOOO What does that all mean? It means you just retarded you engine timing and any gains with the extra 2psi just went out the muffler as unburnt fuel.

You are not going to blow the engine up running more then 14.7 PSI on a BPU 1JZ-GTE. It will handle over 20psi just fine on stock 370's.

ohh the irony in your post :rofl:

 

[bountykilla0118]

WTF is up with the 7M BS above?? ^^^ GTFO

Que? Lol honest mistake?

Whats with all this mis-information?

First off, you don't "tune" boost cut away with an SAFC. The SAFC fools the ECU thinking it's getting more air or less air, making the fuel injectors put out more fuel, or less fuel. When you install 550's on a stock 1jzgte ecu with SAFC, you tune out 33% fuel at idle, and with stock twins, almost 33% minus fuel at WOT.

What does that all mean in the long run? Using the SAFC you just fooled the ECU to think it's getting less air then it really is getting. You are not raising the boost cut, you just fooled the ECU to think it's only at 14psi when it's really at 16.

SOOO What does that all mean? It means you just retarded you engine timing and any gains with the extra 2psi just went out the muffler as unburnt fuel.

You are not going to blow the engine up running more then 14.7 PSI on a BPU 1JZ-GTE. It will handle over 20psi just fine on stock 370's.

Ric you can argue about the "play on words" all day but the bottom line is you are now able to boost past 10-12psi boost cut while being on the stock system..... I took out 17% percent fuel at 4400rpm and my a/f ration is 11.4. Isn't the 25%(+/-) mark is the point where the SAFC starts to affect your timing. Raising boost cut is raising boost cut. I understand that that Karman send out hz's and I think its some where around 1600hz range where the actual boost cut comes in. So yes you did raises the boost cut. When my car was tuned my timing was not affected and that was at 14-15psi and I put down a little shy of 300rwhp (290 something) and 321lbs on my 7m that is hence the tq numbers ....

 

[beatle]

Whats with all this mis-information?

First off, you don't "tune" boost cut away with an SAFC. The SAFC fools the ECU thinking it's getting more air or less air, making the fuel injectors put out more fuel, or less fuel. When you install 550's on a stock 1jzgte ecu with SAFC, you tune out 33% fuel at idle, and with stock twins, almost 33% minus fuel at WOT.

What does that all mean in the long run? Using the SAFC you just fooled the ECU to think it's getting less air then it really is getting. You are not raising the boost cut, you just fooled the ECU to think it's only at 14psi when it's really at 16.

SOOO What does that all mean? It means you just retarded you engine timing and any gains with the extra 2psi just went out the muffler as unburnt fuel.

You are not going to blow the engine up running more then 14.7 PSI on a BPU 1JZ-GTE. It will handle over 20psi just fine on stock 370's.

the man speaks the truth

ive found that boost cut is actualy 14psi, not 1 bar (14.7psi)

also FCD and the like "clamp" the voltage from the MAP sensor at a certain voltage just before cut kicks in so the ecu never thinks it is boosting over 14psi.

 

[bountykilla0118]

Really..... I thought that was the obvious ....... All piggy backs scale back information to alter boost/fuel cut.

 

[annoyingrob]

The ignitor output for the tach is directly affected by the coil triggers by the ecu. If the ecu doesn't fire the coils your tach will have a false reading and will jump around.

You are 100% correct.

And my standalone cuts spark instead of fuel . Every time I hit the rev limiter, the tach drops a thousand rpm.....