Best fuel cut prevention device which does not totally remove fuel cut

[The-Plethora]

Almost there now and hopefully be able to get a FCD device of some sort fitted soon and finally get the car rolling roaded.

Initially I was expecting to pickup a HKS FCD but read up on it and found these devices totally remove fuel cut. Someone posted a link to a similar device that prevented fuel cut but also allowed an upper limit still but the web site had long since died.

 

Ideally I want a low setting of 0.8, a high of 1.2 and fuel cut around 1.3/1.4. I won't be fitting it myself so not worried about how involved it is. Can anyone recommend the best current one that does not cost the earth if poss?

 

Cheers

Dave

[jimmenico]

When I was looking, the Thor unit seemed to come most recommended, and I have fitted two units without problems. They are harder to get hold of now though, since they stopped being produced, but sometimes pop-up on here or eBay. [Hint: people going single turbo often switch to piggy-back/standalone ECU - a previously fitted FCD may then become surplus etc.]

 

Apart from the HKS FCD, maybe try the traders on here to see what's available new?

[The Raven]

Buy an N/A

[monsween]

Buy an N/A

 

Such a happy-go-lucky response

[Nic]

The GReddy Boost Cut Controller has a screw inside the box to adjust the boost cut limit.

 

15510019 GReddy BCC

[edge]

I can help you fit it if you like dude to save a few pennies. Very straight forward.

[The-Plethora]

Cheers edge, might take you up on that. I will look a little longer but looks like I am going to be stuck with an FCD, nothing on ebay and a few sites that have the Greddy ones as discontinued.

[edge]

No worries dude. I have all the kit like soldering iron, heatshrink etc

[Ian C]

You are asking the impossible I shall now explain in a wordy fashion.

 

Fuel cut occurs at 1bar of boost. The stock ECU knows what the boost pressure is thanks to the MAP sensor, and this sends a signal to the ECU between 0volts and 5volts. 0.96bar is 4.40volts, which is what I set the E-Manage fuel cut clamp to, as it gives the maximum sensor range but avoids hitting fuel cut when minor fluctuations occur.

 

You may have spotted that 4.4v is rather close to the maximum reading of 5v for the sensor. It gets worse as well, because when near the maximum range, the sensor accuracy drops right off. The highest boost it will accurately read is 1.15bar @ 4.8v. So no matter what boost pressure you reach, the stock MAP will be spitting out 4.8v. If you enable fuel cut for this, it'll cut at 1.15bar, no higher.

[Ian C]

Moved to tech

[The-Plethora]

Cheers Ian, trying to get my head around it all. So what you are saying is if I want 1.2Bar I need to get a HKS FCD with no fuel cut? Slowly learning.

[Blackie]

I can help you fit it if you like dude to save a few pennies. Very straight forward.

 

You can do mine then J

[edge]

Cheers Ian, trying to get my head around it all. So what you are saying is if I want 1.2Bar I need to get a HKS FCD with no fuel cut? Slowly learning.

They are all designed to stop fuel cut. I think what ian is saying is that you need to get it 4.8v no more but this will only allow you to boost to 1.15 bar. Anything over that and you remove the fuel cut altogether out of safe boost range. Mine was only boosting to just over 1 bar as the difference seemed minor for the extra risk that's involved.

But if you want it at 1.15 bar you may get days when it's cooler etc that you still see some fuel cut but if know you how to use your boost controller you can adjust that to suit.

 

You can do mine then J

Bring it over and aslong as you wear a french maids outfit and make me tea.

Edited January 22, 2011 by edge (see edit history)

[Ian C]

They are all designed to stop fuel cut. I think what ian is saying is that you need to get it 4.8v no more but this will only allow you to boost to 1.15 bar. Anything over that and you remove the fuel cut altogether out of safe boost range. Mine was only boosting to just over 1 bar as the difference seemed minor for the extra risk that's involved.

But if you want it at 1.15 bar you may get days when it's cooler etc that you still see some fuel cut but if know you how to use your boost controller you can adjust that to suit.

 

 

That's not quite what I'm saying. Removing fuel cut is easy, just clamp it at 4.4v. Most FCDs do that, I think one crap one scales the whole signal instead of clamping it, which affects the entire operation of the engine.

 

Raising fuel cut isn't possible past 1.15bar, and even for that you'd need trick electronics that functions as a gate system, of which I think precisely none of the FCDs on the market do.

 

As soon as you send 4.5v or more to the stock ECU it'll trigger fuel cut. The trick FCD would watch the output from the MAP sensor and do one of three things:

1) voltage is less than 4.4v = send voltage signal on unchanged to ECU

2) voltage is more than 4.4v but less than 4.8v = send 4.4v on to ECU

3) voltage is at 4.8v or higher = send voltage signal on unchanged to ECU (thus initiating fuel cut)

 

Great, except 4.8v = 1.15bar so you're still below safe BPU levels, so what's the point. If you want a higher range you'd have to fit a different MAp sensor, and you can't run the stock ECU with that and it all gets a bit silly. Better to fit a boost gauge with a big flashing red light or something

[Shane]

That's not quite what I'm saying. Removing fuel cut is easy, just clamp it at 4.4v. Most FCDs do that, I think one crap one scales the whole signal instead of clamping it, which affects the entire operation of the engine.

 

Raising fuel cut isn't possible past 1.15bar, and even for that you'd need trick electronics that functions as a gate system, of which I think precisely none of the FCDs on the market do.

 

As soon as you send 4.5v or more to the stock ECU it'll trigger fuel cut. The trick FCD would watch the output from the MAP sensor and do one of three things:

1) voltage is less than 4.4v = send voltage signal on unchanged to ECU

2) voltage is more than 4.4v but less than 4.8v = send 4.4v on to ECU

3) voltage is at 4.8v or higher = send voltage signal on unchanged to ECU (thus initiating fuel cut)

 

Great, except 4.8v = 1.15bar so you're still below safe BPU levels, so what's the point. If you want a higher range you'd have to fit a different MAp sensor, and you can't run the stock ECU with that and it all gets a bit silly. Better to fit a boost gauge with a big flashing red light or something

 

This is something I have been playing with recently and can achieve the trick scenario easily with few components and some very basic circuitry. I have noticed though that without any fcd I hit cut at just over 1 bar and originally thought this was the lousy gauge I had, but comparing it with 2 others it seems that its slightly over, is this normal and is there a difference between individual ecus? Another question, is there a real difference in performance between 1.2 and 1.15? for my money I feel comfortable in the knowledge that the ecu is still doing what it should at 1.1 or so.

[Ian C]

This is something I have been playing with recently and can achieve the trick scenario easily with few components and some very basic circuitry. I have noticed though that without any fcd I hit cut at just over 1 bar and originally thought this was the lousy gauge I had, but comparing it with 2 others it seems that its slightly over, is this normal and is there a difference between individual ecus?

 

This is normal. It's not an exact science, pressures fluctuate by a small amount quite rapidly inside the plenum, even with a dampner in place. Fuel cut is a strategy rather than just a switch - you can sneak into the 1 bar region for a couple of seconds and get away with it, but the higher the pressure goes the fast it cuts in. Also, if boost is building up rapidly, then yes - by the time fuel cut has an effect, the boost pressure has had a bit longer to build boost anyway. you'll always see a peak of slightly higher than 1 bar.

 

Another question, is there a real difference in performance between 1.2 and 1.15? for my money I feel comfortable in the knowledge that the ecu is still doing what it should at 1.1 or so.

 

1.15 is the very highest you could go, but really you'd have to sit a bit under that to avoid any 'false positives' due to the previously mentioned fluctuations and the fuel cut strategy. So really 1.1bar would be the highest you could run without the constant threat of briefly triggering fuel cut. Stock to 1.2bar of boost is an increase of about 7psi, and a ballpark figure is 10 to 15bhp per psi. You'd probably be down 20 to 30bhp.

[Shane]

OK thanks. So if I was to clamp the max voltage to the ecu so it never exceeds what the ecu interprets is 1.1bar, and then the boost continues to rise to 1.2bar, does the ecu still try to increase fueling with the limited variable data it's still getting from the o2 sensor and others? Also, is this 'gap' between 1.1 and 1.2 bar where a SAFC would pay off? I do know that you are not a fan of these though

This is normal. It's not an exact science, pressures fluctuate by a small amount quite rapidly inside the plenum, even with a dampner in place. Fuel cut is a strategy rather than just a switch - you can sneak into the 1 bar region for a couple of seconds and get away with it, but the higher the pressure goes the fast it cuts in. Also, if boost is building up rapidly, then yes - by the time fuel cut has an effect, the boost pressure has had a bit longer to build boost anyway. you'll always see a peak of slightly higher than 1 bar.

 

 

 

1.15 is the very highest you could go, but really you'd have to sit a bit under that to avoid any 'false positives' due to the previously mentioned fluctuations and the fuel cut strategy. So really 1.1bar would be the highest you could run without the constant threat of briefly triggering fuel cut. Stock to 1.2bar of boost is an increase of about 7psi, and a ballpark figure is 10 to 15bhp per psi. You'd probably be down 20 to 30bhp.

Edited January 23, 2011 by Shane
addition (see edit history)

[Shane]

Sorry just realised what i asked was incorrect and cant edit it from tapatalk. Didnt mean 1.1 bar I meant 1bar or the point where the ecu performs fuel cut. Also, if the safc fudges the signal from the map i guess it is pointless anyhow. Does the emanage work in a different way?

[The-Plethora]

Pay day is here and it seems I have 2 choices...

 

http://www.futuremotorsports.com/images/P/GREDDY%20BOOST%20CUT%20CONTROLLER%20%28BCC%29.jpg

 

This unit prevents fuel cut at Wide Open Throttle when your turbo(s) wants to make more boost than your onboard computers wants them to. A must have for all pushing more PSI than stock

Our price: £99.50

 

or...

 

http://www.futuremotorsports.com/images/P/HKS%20FUEL%20CUT%20DEFENCER%20%28FCD%29.jpg

 

The HKS FCD is an electronic device developed to properly raise the factory fuel cut level on factory turbocharged vehicles. As modifications are made to optimize engine performance, the factory fuel cut is often triggered by higher boost levels which activate a fuel delivery cut-off as a failsafe procedure. Symptoms of fuel cut are hesitation, bogging, and/or illumination of diagnostic indicators.

The electronic signal from the FCD will raise the fuel cut level to accommodate for the additional boost without triggering fuel cut and/or an engine diagnostic light. The FCD installation is designed to be easily integrated with the VPC/F-CON or factory ECU harness.

Our price: £93.50

 

 

Both of these are on http://www.futuremotorsports.com

 

Would the Greddy one come with everthing I need? I have seen other units like the Turbosmart ones that need to connect to a Turbosmart controller.

The prices on both these units seem pretty good. I presume if the Greddy one works as is I should go for that one over the HKS?

 

Cheers

 

Dave

[Nic]

Both have everything you need. Both need splicing into the main wiring loom.

 

If you don't want to cut up the wiring loom you may want to buy a bridging harness (Field Harness), this fits between the ECU and the wiring loom, so rather than cutting into the main wiring loom you splice any electronics into the bridging harness instead. So you can splice any electronics onto the bridging harness in the comfort of your home, rather than upside down in the passenger footwell, it also keeps things a lot neater in the long run.

 

Fields Bridging Harness

Edited January 24, 2011 by Nic (see edit history)

[The-Plethora]

No luck on the Greddy, seems out of stock in most places so have ordered the HKS, I will be careful. Edge I might be giving you a nudge

[edge]

No luck on the Greddy, seems out of stock in most places so have ordered the HKS, I will be careful. Edge I might be giving you a nudge

 

No worries dude

[sams]

sorry to bring to the top, i have just purchased a turbosmart FCD, and you dont need a controller with it.

i got it from Paul Whiffin and he confirmed this as it wires in exactly same as a hks unit, and the advert for it is miss leading by say it to be used in conjuntion with there contoller.

 

i will be putting it in today so will let you know how it is

[sams]

well it all fitted and working perfect.

 

no more fuel cut

/vbb/images/smilies/bbcode_grin.gif

[The-Plethora]

Mine should be here next week, I ordered it back when I made the thread but had a bit of bother ordering so had to get it from somewhere else.

At the moment I have it on low boost and occasionally get the exclamation mark on WOT (no fuel cut) but hope to take it to AFR once its all in for a once over.