Fuel Cut Defence

[NewGen]

I was wondering what people were using to fix fuel cut.

thanks

[UberSupra]

550s / Lexus AFM
20 psi on my SP-61GT and no fuel cut

[Clip]

hks used to make a fuel cut defencer and a speed limit defencer, dont know if they still do.

[crisp]

hks used to make a fuel cut defencer and a speed limit defencer, dont know if they still do.

FCD is still listed... that's what I have by HKS. Has been working well for over a dozen years with this car. I'm pushing a modest 15psi through a CT-26 hybrid with H3 (T04b?) spool... pretty old style... but it works.

No problems here... but my stuff is pretty much all HKS matched. (VPC,EVC,PFC-FCON, etc...)

http://www.hksusa.com/products/more.asp?id=683

G/L.

-crisp

[NewGen]

thanks for the info. I'll try the HKS one they have them on ebay there universal. I dont no if they are all that way but its worth givin it a shot. I might upgrade to the lexus afm later.

thanks

[NewGen]

actually i just went threw that link and see they make one for the supra. I'll deffinately be getting one soon. Thanks

[crisp]

Newgen...

Be sure to discuss your mods with an HKS rep or tech person... or read alot (search) in here before you do it. From what I've read, there are those who say the FCD can add "risk" to "blowing up" your car...:icon_conf

(Personally, I don't know why or how... as my BALANCED setup has posed NO issues... so I suspect it's related to not understanding how it works and/or misuse...)


G/L!


-crisp

[starscream5000]

Misuse indeed. I you put one on, then go straight into cranking up the boost without knowing what your engine is doing, you'll run a huge risk of having a meltdown. Fuel cut is there for a reason, understand why before you think of bypassing it.

[hottscennessey]

Crisp is right, it has everything to do with balance and misuse.

A brief explanation of what the HKS FCD is doing:

Let's say you're boosting 1300hz (according to the airflow of the AFM) and hitting FC.
The FCD is going to cap the AFM signal just before boost cut (1250hz or so?) and going to make sure that the ECU continues to get the signal just below where fuel cut would be activated.
The problem with this- the ECU uses the AFM as a primary input for calculating how much fuel goes into the engine. If you're boosting 15PSI say thats 1600hz, the ECU is only putting in 1250hz worth of fuel due to the FCD capping the signal.. causing a lean condition. This is very dangerous.. I have a dyno sheet I need to dig up of what this looks like...

BTW I'm just making up the HZ numbers to illustrate a point, so if they're not accurate thats why.



The only safe way to run a HKS FCD is with a wideband and thats my honest opinion. The safest way to get around fuel cut is with a lexus AFM, walrbo, 550cc injectors, a AFPR and tuning. Let me explain. If you go with the lexus, 550's, and walbro you're balancing out the equation (25% more flow than stock w/ air AND fuel). If you're still hitting fuel cut (you probably have a boost leak) you can tune it out with the wideband by upping the fuel pressure, and leaning out the fuel map. This way you're richening the mixture while lowering the airflow signal (HZ). I wouldn't cut more than 25% fuel because it is rumored that it will mess with timing. Doing this has helped me hit over 26PSI without fuel cut.

If you do it like this you don't even need the FCD.. I think it's better that way.

[CampbellsChunkySoupra]

lol... cranking up the boost as soon as u get the car. probably not the best option. one way ticket to the machine shop.

edit* matt, have fun with that orange gt mustang that i hear u are going to run this weekend. it isnt stock.. and yes, he WILL eat you alive. dont give my car a bad name. considering u just baught an almost exact replica of mine and u live within a mile of me. man, its gonna suck seeing another white one around here...

[hellraiser456]

i don't like FCD...and for a reason. Feul cut..despite is "inconvenience" is very good...as it will save your engine...my roomamtes mr2 has one and it is currently out shopping for a new engine cause he has blown the crap out of his HG and his motor has seen 20psi (22peak) from a stock turbo (which is slightly smaller than ours) and all he has is a walbro for fuel. to me that is sketchy. the lex/550 combo to me is a FAR better mod simply because as far as i know fuel cut still exists...

[Aspec]

Are you asking about "MKIII" fuel cut or "MKII w/Metro 3 cylinder twin turbo" fuel cut? :biggrinbo

[kapkaniMD]

Doesnt a MAPECU solve the problem of fuel cut as well and is a lot better for proper tunning??

[NewGen]

I'm not trying to run stupied amounds of boost. I'm also not uping it right away. I'm trying to decide what the best way to keep the car from hitting fuel cut. I can just upgrade injector and the rest of the fuel system to keep it from hitting it that way right?

thanks for the info guys it really helps. please keep it comin


Side Note: Thanks for the encouragement tyler... I really appriciate it...

[crisp]

I'm not trying to run stupied amounds of boost. I'm also not uping it right away. I'm trying to decide what the best way to keep the car from hitting fuel cut. I can just upgrade injector and the rest of the fuel system to keep it from hitting it that way right?

thanks for the info guys it really helps. please keep it comin



Just another note... having used my HKS setup for over a DOZEN years now... with NO ISSUES WHATSOEVER related to air/fuel... my car starts, idles, and pulls cleanly thru the entire rev range, and has accommodated various "staged" (read: balanced) upgrades throughout it's life. Next week, my HKS 550cc injectors and GCCII will FINALLY be a new addition! WOOT!

I'll then be ready for an even BIGGER turbo...:evil2: But I'll probably stick with a CT hybrid for ONE more round before going T4 flange, etc...

Whatever route you go... be sure to consider BOTH what you want/need NOW as well as what you may EVENTUALLY do in the future. Not all setups are "conveniently" upgradable... and a little research up front should help you make good investments for the future of your car modding plans.

LASTLY, my PFC-FCON may not allow control much over 15psi, but there is something to be said for the "quality" of boost. At any given boost level, you can have a BROAD range of absolute HP output... in other words, all PSI's are not created EQUALLY! (You can be at 300hp or 400hp at the same 14-15psi level... something to be said for BALANCE and EFFICIENCY of your articular system.)

Ultimately, I suspect I can get CLOSE to my next goal of 500hp with around 15psi. (450-500 range is the target right now...)

G/L!

-crisp

[hottscennessey]

I'm not trying to run stupied amounds of boost. I'm also not uping it right away. I'm trying to decide what the best way to keep the car from hitting fuel cut. I can just upgrade injector and the rest of the fuel system to keep it from hitting it that way right?

thanks for the info guys it really helps. please keep it comin


Side Note: Thanks for the encouragement tyler... I really appriciate it...

You cannot just upgrade to 550cc injectors and magically not hit fuel cut. The ECU will still be reading the same ammount of air and you have not "told" the ECU that you're running 550cc injectors.. IF it ran, it would run terribly rich and still hit fuel cut at the same ammount of boost.

This is why we upgrade to the lexus AFM. It let's in ~25% more air to go with that 27% increase in fuel by the 550cc's. You'll also want to upgrade to a walbro because theres a good chance your fuel pump will let go with the 27% increase in fuel flow.

So in theory, ~25% more air and fuel will put you where you were before (as far as air/fuel ratio) but you'll have a lot more air moving through the engine (boost).

[crisp]

You cannot just upgrade to 550cc injectors and magically not hit fuel cut. The ECU will still be reading the same ammount of air and you have not "told" the ECU that you're running 550cc injectors.. IF it ran, it would run terribly rich and still hit fuel cut at the same ammount of boost.

This is why we upgrade to the lexus AFM. It let's in ~25% more air to go with that 27% increase in fuel by the 550cc's. You'll also want to upgrade to a walbro because theres a good chance your fuel pump will let go with the 27% increase in fuel flow.

hmmmm... good points. I ALSO have to upgrade a PROM along with the addition of my 550's. My PFC-FCON is already "chipped" to handle it, but the VPC (Vein Pressure Converter) that communicates with it is not "balanced" to the 550's without a chip change. Once again, "BALANCE"!

hottscennessey,

Do you really think I will have an issue with my setup with the stock fuel pump? I know HKS has said they tuned with the stock pressure regulator and pump for this setup. I DO have a BRAND NEW fuel pump in my car... but I MAY go to the Walbro if there is alot of concern...

I appreciate advice/experience with these things... thanks for the input.

-crisp

[CampbellsChunkySoupra]

silly kids...

[NewGen]

thanks guys. were could i eventually buy a lexus afm and how hard is it to install?

[CampbellsChunkySoupra]

check the for sale forums. buy one. open the box. and then just plug it in.

[NewGen]

Thanks. I found a few. But im deffinately not ready to buy one yet.

[hottscennessey]

hottscennessey,

Do you really think I will have an issue with my setup with the stock fuel pump? I know HKS has said they tuned with the stock pressure regulator and pump for this setup. I DO have a BRAND NEW fuel pump in my car... but I MAY go to the Walbro if there is alot of concern...

I appreciate advice/experience with these things... thanks for the input.

-crisp

Crisp,
If you have a brand new pump, you should be fine considering HKS tuned w/ it. If you do decide you want more power/larger injectors I'd suggest a walbro. Also, one thing to remember.. when you install the walbro it's a good idea to drill out the J-tube on the block for the fuel pressure regulator return. It has a restriction in it designed to give the fuel rail enough pressure to limp home in case of a FPR failure.. but if ran with a walbro you may have problems controlling fuel pressure at idle..

[crisp]

Crisp,
If you have a brand new pump, you should be fine considering HKS tuned w/ it. If you do decide you want more power/larger injectors I'd suggest a walbro. Also, one thing to remember.. when you install the walbro it's a good idea to drill out the J-tube on the block for the fuel pressure regulator return. It has a restriction in it designed to give the fuel rail enough pressure to limp home in case of a FPR failure.. but if ran with a walbro you may have problems controlling fuel pressure at idle..

Ahhhh... I have seen the comments about this "J-tube" often... but your explanation is the most clear so far.

Yes, I do believe sticking with the HKS theme over the years has helped me keep my car running well. (Except for the "short" that had me "down" for over five years!) I will continue to follow the advice from HKS on most matters of "system balance" on my car.

Thank you for your input.


-crisp

[supradoc]

is there any advantage to running 550s with the walbro fuel pump and tuned with an safc2 rather than using the lex afm?
i've been in talks with one of the local shops and this is the route they are recommending.
they said i wouldn't need the lex afm or the afpr?
anyone running this set-up

[CampbellsChunkySoupra]

obviously, u lose a certain amount of adjustibility with running the stock afm. think about it, add the extra air that the lex afm can offer stock.. then tune it with the safc2 :D

remember, you are trying to get the most air/fuel u can in there at a good ratio.

[supradoc]

so if running the safc2, 550's and lex afm, you wouldn't need the afpr anymore because the tuning with the safc2 will take care of that??

[CampbellsChunkySoupra]

as far as i know that is not correct. i believe the safc2 just controls the amount of fuel/air. you would also need to be able to adjust the fuel pressure to keep up with said increase of fuel delivery and increased injectors. forgive me if im wrong.

[supradoc]

weird...cause all they said i needed were the 550s, safc2, and walbro fuel pump (i already have the required preliminary modifications)
just kinda confused now on which route to go with...and what parts to get...

[foreverpsycotic]

why not just get a map ecu for the price of the AFC and the lex, and run in speed density?

[hottscennessey]

You could do it that way... but you'll have a restriction in front of the turbo, and it'll take a whole lot more tuning than just upgrading to the lexus. The FPR is not necessary, but really helps when tuning to avoid fuel cut, and getting a nice crisp idle.

Another concern is when you don't do the lexus AFM and install the 550's to tune with the stock AFM you'll be taking out (in theory) 27% of your fuel across the board.. which will realllly screw up your timing (according to rumor, it will advance it) and make you very likely to detonate and blow your motor. Don't listen to people/shops who don't know OUR cars and OUR ECU's and ASSUME that all of their car information/logic will carry over. While most of it will a lot won't. You know what they say.. when we assume it makes an ass out of u and me. ;)

In theory the reason you'd go with a lexus and 550s is because you wouldn't have to tune at all. Unfortunately this isn't always the case, as usual it makes you run on the rich side. By leaning it out it will put you even further away from fuel cut.

[starscream5000]

^Very well put.

[supradoc]

wow...that really clears things up...much appreciated. now i know which route to take.:thumbup:
thanks for the help.
cheers.