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Discussion Starter · #1 ·
I may be talking rubbish here, but would like to understand something so bear with me and point me in the right direction if I'm wrong please.

After reading loads of posts on the subject of fuel cuts i have read quotes such as...

On fitting an APEX induction kit I have suffered fuel cut recently ......and
My friend has fitted both an after market exhaust system and HKS induction system and has started noticing what seems like fuel cuts under heavy acceleration at 5000 -6000 rpm!.....

I also noticed this interesting post:

You can adjust the calibration on the airflow meter yourself. There is a little screw on the bottom that is covered by silicone.Dig out the silicone and back it out some and the air flow meter registers less air and therefore you postpone fuel cut (you allow more air to bypass the part of the air flow meter that counts the air). The adverse effect is that you also lean out the a/f ratio. Shouldn't be a problem because Evos run rich antway, but it would be a good idea to monitor your EGTs to make sure. This is no less dangerous than the fuel cut defencer and costs you nothing.

It seems that 90% of fuel cuts occur after an induction kit is fitted. The induction kits allow more air to pass thru the Air flow meter housing and the info sent to the ECU is therefore scaled up due to the higher vol of air.
In a naturally aspirated engine, more air into the airflow meter may encourage the ECU to increase the amount of mixture. However, it seems that in a forced induction engine such as our 4G63 turbo units, it seems that the extra air passing thru the airflow meter serves to increase the likelyhood of fuel cuts more than anything. The main increase in air flow comes from the turbo charger as it rams air into the engine.

So why bother with an induction kit ?

If the ECU parameters are not adjusted to acknowledge the extra air flow then all we are doing is unbalancing the system ?

It seems that an after market exhaust makes a nicer tone and reduces back pressure. An induction kit allows more air into the air flow meter but do we really want more air and less back pressure ?

When I replaced the CAT on my car after 1 year of driving without it, I noticed that the low down torque was improved.
I guess that this was due to an increase in back pressure. The reduction in back pressure when the CAT was removed seemed to give a little more pwr up the rev range but less at the bottom end. The addition of the Air induction kit made the car sound better but I experienced fuel cuts. when i remove the rear silencer baffle in my 5ZIGEN exhaust, I experience a shift in pwr to further up the rev range.

Are we not just going round in circles here ?

I drove a friends stock E4 and found that it was much quicker than my modified E4. This E4 may have had the grommet removed in the boost control solenoid and i will be checking to see what the situation is here. But the point is that i have a boost controller|PLS| Exhaust system |PLS| Apex induction kit and run on Super UL. If I pull 1.22 bar I get a stumbling fuel cut during full throttle acceleration, whereas the standard car just pulls and pulls and all on STANDARD Unleaded !!! I am rather confused to say the least.

Mitsubishi has designed an ECU to run our engines at 280bhp approx. They designed the exhaust system and incorporated a CAT. They have mapped the fuel,pwr and torque curves based on a pre-determined airflow reading and carefully calculated the actual exhaust backpressure found in the standard system. The ECU expects all the values to be within a certain predetermined tolerance and then we go and change the balance in a search for more pwr !

Are we improving the car or just buggering things up ?

Comments please !


Discussion Starter · #2 ·
i understand that the ecu has the ability to map correctly past the point of fuel cut
hence you need to get rid of this problem,then you could safely run 1.3 or 1.4 bar...and then your other improvements come into play
hopefully then you will leave your mate in the dust

just a theory,i got fuel cut usually the first time i put the car under boost after warming it up,and i do drive a long time/way before using the power,after this initial cut,it would rarely do it again that Session
its as if it has woken up and accepted whats going thru once the temp etc has stabilised ????????????????

Discussion Starter · #3 ·
I never have any fuel cut problem ... even I am running 1.3 bar in my Evo with SARD blow off valve and ARC Induction Box

Discussion Starter · #4 ·
We can only effect limited mods to the standard car before the factory map is exceeded , the fuel cut is protecting the engine. My VI fuel cut like a bsatard when I installed the Nurspec and filter with the grommet removed , I had to reinstall it.
This is because the engine can process more air with less restrictive intake and exhaust , ok if the grommet is left in , but remove it and the ecu will stop play.
The ECU must be remapped to correctly set higher boost ,fuel and ignition curves.
Trust me , u do not want subject yr car to fuel cuts on a regular schedule , it is mechanically very stressful

Discussion Starter · #5 ·
I have an rs 2 with the same problem

i don t have a aftermarket induction kit i only have a ralliart air filter
full hayward and scott exhaust plus cat replacement pipe

if the weather is cold i dont punt my pedal to the metal i got many fuel cuts but in the summer i have no prob

solve prob from september to april standard filter and exhaust

is there not some kind of bypass so we can get 0.2 higher in boost

at what pressure does the fuel cut come in (in bar please)

Discussion Starter · #6 ·
I only get fuel cuts when I push the car with a peak boost of 1.2 bar as registered by my Blitz DSBC.

If stick to a constant boost of just over 1 bar and a peak of 1.15 bar then I am fine what ever I do.
With a standard boost solenoid and grommet removed the Evo can peak at 1.4 bar i have been told.

By restricting the air flow a little at the filter end (eg:using standard air box)would it be possible to increase the boost levels with less chance of a fuel cut ?

The 2 main sensors responsible for instructing the ECU to fuel cut are the airflow sensor and the knock sensor.

By having a slightly lower velocity of air flow into the MAF sensor, then the likely hood of fuel cut due to too much air passing across the sensor will be lessened surely ?

I am gonna try my car with the stock air box and performance panel filter and then again with the stock filter and see how much more constant boost i can pull.......

I'll keep you all posted


Discussion Starter · #7 ·
It is very strange... my one is HKS EVC 4 ...running 1.3 bar with Apexi - S - AFC, never ever have any problem for fuel cuts....even I was racing with FERRARI 288 GTO few weeks ago ...doing but 150 mph... and then beated him

Discussion Starter · #8 ·
I'd have to agree with Evoboy

I have an HKS induction and Magnex/Blitz full decat exhaust. I have had no fuel cuts with the solenoid grommet in place, but as soon as I removed it, the fuel cuts occurred when flooring it form low down the rev range.

Ralliart are now installing the sports ECU and I hoping that this will solve the problem.



Discussion Starter · #9 ·
Evoboy and amp; Naunt,

I have Blitz filter and since Thursday, de-cat and Nur-spec exhaust.

Drove ok, but was now noticibly 'slower' than my mates GSR.

He removed the gromet for me, tried it again and now I have overboost and cutouts.

I think I will try the standard air box again, as I don't want to loose the exhaust.

Discussion Starter · #10 ·
Why you guy's Evo got that kind of problem..??

I have my Evo 4 for nearly 2 and half years now

What I got in my evo is -

ARC Induction Box
Sard Racing Blow off Valve
HKS EVC 4 - 1.3 bar
Apexi S - AFC
Hyper Muffler ( Still got my cat with - meooooo ... border|EQU| 0 align|EQU| absmiddle >)

Every else are standard....

Rolling Road tested 318 BHP - never have any problems with fuel cuts or overboost.

Discussion Starter · #11 ·
No fuel cuts for me, most of you have seen my set up, Mongoose decat, HKS panel filter, modded air box, grommet removed, R/Roaded several times at 318bhp/ 286lbsft. I reckon your right toooo much air with those induction kits.

Rgds Kevin

Discussion Starter · #12 ·
If the ECU cuts off the fuel when you fit a direct induction kit, then why don't you change the ECU?
Maxi changed his' and it's not cutting him off anymore. (he fitted the Ralliart Sports ECU for Rally)

Discussion Starter · #13 ·
I went out in my Evo4 on Sunday as a passenger to read what continuos boost was actually being produced and was surprised with what I saw……

During acceleration the peak boost reading recorded on the Blitz DSBC was 1.12 bar. During this acceleration period I noticed that the analogue boost gauge showed a slight fluctuation upto 1.1 bar and then it stabilized at 1.0bar for the duration of the acceleration. This process was the same or similar for all gears.

I increased the ratio setting on my DSBC and this effectively keeps the waste gate closed for a touch longer to get a higher overall boost. The results were that the registered peak reading was 1.18bar but when I was staring at the analogue gauge, I noticed an initial jump past the 1.1bar number and then the boost settled back to 1.0 bar for the duration of acceleration.

If I were to increase the ratio even more then I don’t seem to go any faster but the peak boost goes over 1.2 bar and I experience a stumble during acceleration which I rekon is a fuel cut.

On the Blitz DSBC I have a “boost limiter” and a feature called “scramble boost” . I tried setting the limiter to beep at 1.0bar but not to reduce the boost. The beep triggers the scramble boost feature which will either reduce the ratio or increase the ratio when triggered. I set the Scramble boost setting to increase the boost(ratio) when 1.0 bar was hit and all I can say is WOW !!!

The car took off like lightening and the peak boost was only 1.11bar. I was driving at the time so couldn’t read what the analogue gauge was reading but the seat-of-my-pants feeling was that the constant boost was higher with less overboost.

What does this mean then ?


Discussion Starter · #14 ·
fuel cut is a major abrupt cut out,like you have blown it up
it then takes a few seconds to recover
it is not a stutter
i suspect you have the same problem i had with plugs,if you have standard plugs they can blow out with extra boost
also if you are using racing plugs,and either doing too much town work before you clear it out,or on constant long steady throttle runs,they will foul a few times when you boost it again
ive got hks plus at the moment,which seems to have cured this so far

also,fuel cut ,i belive,is only caused by air flow,not by knock .

Discussion Starter · #15 ·
This is all very confusing! I have the grommet removed, Blitz filter and full Magnex de-cat and get no fuel cut (yet). My analogue boost guage never shows more than 1.0 bar either. Perhaps it has something to do with the calibration of the air flow meter being slightly different from car to car?

Discussion Starter · #16 ·
My story;

Full exhaust inc. front pipe and standard airbox |EQU| no fuel cuts.

Full exhaust inc. front pipe, standard air box and grommet removed |EQU| regular fuel cuts on full acceleration in 2nd and 3rd gears at around 5000rpm. (I think I was the one that opened this can of worms originally) border|EQU| 0 align|EQU| absmiddle >

I think the temperature as a lot to do with the fuel cuts.

As above |PLS| Blitz induction kit |EQU| no better no worse as far as fuel cuts are concerned.

I don't think the induction kit as much to do with the problem.

Discussion Starter · #17 ·
i would agree,i have had cut on occasion,but not regularly
it seems to be more humidity critical than anything.
but they do also have a barometric sensor and outside temp sensor
we need to know exactly what and only what can cause fuel cut.
anyone cured it by backing off the sensor in the afm
by how much ???

Discussion Starter · #18 ·
I've tryed to fit the ralliart ecu with more boost and there's no fuel cuts at all,and the acceleration is improved!!!

Now I have the standard ecu fitted and again fuel cuts.

I don't know if I'm going to spend £850 for the ralliart ecu,to fit an hks fuel cut defencer,or maybe to fit the BLITZ ecu,costs around £750.


Anyway a possible cause for the fuel cuts,can be the malfunction of the wastegate actuator.

My car have 1.2bars with the solenoid restrictor at his place and the metal wastegate restrictor removed.normally it would be around 1.0.

Discussion Starter · #19 ·

When you say that the metal wastegate restrictor has been removed....

Is that the one which sits next/attached to the turbo unit ?


Discussion Starter · #20 ·
The metal restrictor is in the vacuum hose near the wastegate. you have a T composed of 3 different hoses and the restrictor is in the vertical hose going down.

The overboost is higher when the restrictor is small.
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