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Discussion Starter · #1 ·
Does anyone know what boost the factory ECU activates the fuel cut defender in 1st and 2nd gear? Put on a EBC and while the top gear boosts are very well controlled, I get fuel cut-off in 1st and 2nd starting at around 4500 RPMs and around 9 or 10 psi. Am considering a fuel cut lifter to allow freer boosting in the lower gears- the EBC is rock solid for limiting boost- now set at 1.08 bar (15.9 psi). Anyone using a fuel cut lifter?
 

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Something is wrong here, you should not be hitting the boost cut at 15.9 psi. No way. The ECU doesn't know gear, so if you get it in first and second, you're definately going to get it in higher gears (where the load is greater, and the chances of spiking is higher). What other mods are you running? Might be missing, or the ecu might be pulling timing hard (knock?). Doesn't sound right, especially at 9-10 pounds. Sure your boost gauge is reading correctly? Are you using your EBC as a gauge?

jb
 

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I'm not positive, but I think you are referring to a boost cut, not fuel cut right? Fuel cut is at <7k rps, I believe boost cut is @ <17psi.
Regardless you should not be hitting boost cut @ 9psi. I'd take it to the stealership and have them check it out, it could be lots of things.
solenoid, boostgauge, ecu
 

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Discussion Starter · #4 ·
I'm getting the fuel cut in 1st and 2nd gear only. I thought that i had read somewhere that the factory ecu limits boost in 1st and 2nd gear at 7, 10 psi. Has anyone else heard of the factory ECU limiting the boost in 1,2 gear? A similar occurence happened when I installed a Greddy MBC- fuel cut in gears 1, 2 - which eventually went away. I'm wondering if the ECU "dapted" to the onslaught of boost in 1,2 gear.

I'm running a MRT TMS 1 and use a blitz DD timer which has a gauge. The TMS is rock solid at limiting the boost at 15.9, where I have it set. I can run to 15.9 and 16.5- a previous setting in 3, 4 ,5 gear with no boost spikes and no fuel cut. It is only in 1st and 2nd gear.

So, I don't think it is the boost gauge or the EBC. I've been running the boost gauge w/o a MBC, with a MBC and with the EBC. I believe the boost gauge is accurate because when I tuned the MBC in I did hit the fuel cut at 1.23 bar.


MODS: CAI, BOV, MRT TMIC and downpipe, pulleys, MRT TMS- I EBC, Blitz DD turbo timer (with gauge), Tanabe cat-back.
 

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Discussion Starter · #5 ·
One other note. In Turbo and High Tech performance (01/02 issue-the WRX issue!)a similar issue occurred as they modified a DSM 4GS3. Due to increased air flow the MAP sensor freaked and cut fuel. In the same issue the Sparco modified WRX uses an HKS fuel cut lifter to allow freer boosting, a risk without a competent EBC. But the MRT EBC I have is steady. So, I'm wondering if because of the down pipe, much larger intercooler, and lots of boost in 1, 2 gear that the MAP sensor reacts and the ECU cuts the fuel. If this is the case,is a fuel cut lifter- HKS and MRT, worthwhile? BTW, the Sparco WRX shown in the magazine had a front mount IC, HKS EBC , intake, up/down pipe and exhaust, fuel-cut lifter, and it dynoed at 230 torque and 225 hp all at 1.1 bar on the HKS EVC-EZ. Talk about fixing a breathing problem!
 

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Tough call. What are the last 5 digits of your VIN (serial number). This should let you know where you stand as far as ECUs go. You've got alot of mods that should be tuned to work properly, especially with the TMIC and intake. Do you have an obdii scanner? Try to check out your timing, the ecu could be thinking something is wrong and pulling back alot of timing. Maybe try throwing the stock airbox back in and trying it again.

jb
 

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Also, get a proper boost gauge, I've seen alot of people complain about TT boost gauges. You should be able to get an autometer for 40 bucks. Just hook it up quick, verify that everything looks right, if it is, return it or sell it off, if not, there ya go. I'm wondering if you might be spiking bad because of the increased flow the IC gives you.
 

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Discussion Starter · #8 ·
Thanks for the guidance- I will. May also try to reset the ECU. What gets me is that the same thing happened in 1,2 gear when I put the MBC on. What will the last 5 VINs tell me? BTW- if I "hang" at say 5,000 rpm in 1,2 gear the fuel cut continues. A little finessing with the throtle minimizes the hesitation.
 

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last 5 of the vin is the serial number of your car. hunt around on i-club, there was a thread about serial nums and build dates. chances are it'll tell you nothing though, I doubt the ecu has changed at all. Does the TMS have anything called Gain or Rate on it? Basically an adjustment that allows you to control how fast boost builds? If it does, you might try turning that down a bit.

jb
 

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veritas said:
I'm getting the fuel cut in 1st and 2nd gear only. I thought that i had read somewhere that the factory ecu limits boost in 1st and 2nd gear at 7, 10 psi. Has anyone else heard of the factory ECU limiting the boost in 1,2 gear?
I'm not sure what your problem might be - but I believe that the factory ECU limits boost when it is CONTROLLING it through the FBC.

If you override that factory control by installing an EBC and removing the FBC from the loop then I don't think the computer has anything but overboost protection (~17psi from most accounts) at that point.

BTW - it looks like what you're saying is that you had a MBC that eventually functionally set boost to what you wanted in all gears and that when you added the EBC you started running into a problem. Was there anything else done between the mods to look at, or should the obvious culprit be the EBC at this point?

All IMHO of course. Good luck with finding your trouble!

:D
 

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Discussion Starter · #11 ·
Thanks for the help. The MRT EBC has a control module under the hood where you set a min and max boost. Then there is a dial in the cabin which controls the rate the ammount of boost. It is a self-adjusting, closed loop mecahnism which reads MAP. This afternoon, I turned the dial all the way down so I could only get 0.68 boost. It still hesitated around 4800 rpm in 1, 2, and 3. So, it is definetely not an overboost problem or gauge problem as my "butt meter" knows what .7 bar is.

BTW, the Greddy manual BC did the same thing for a few days at approx the same rpm, but it "cured" itself. So, I'll relook at the EBC/solenoid install and keep the MAP air flow theory in my back pocket. Hopefully, which I doubt, the ECU will "learn" the new parameters and adjust accordingly. BTW, the MRT TMIC is a huge volumetric gain vs factory IC, and the AEM CAI is drawing from the wheel because I want a denser charge, so the notion of all these things working togethert has merit. This is my second day with the MRT EBC.
 

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Discussion Starter · #12 ·
BTW, no CELs come on, unlike the time I "dialed in" my MBC and hit 1.23 bar (18 psi) on the Greddy DDTT. When I did overboost and hit 18 psi, the exact feeling that I get now happened then. So, if it did overboost, one would expect a CEL (hopefully).
 

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Hmmm... Not sure about the hesitation ~4800rpm in the earlier gears. Are you WOT? Does the car pull cleanly until 4800rpm? How long does the hesitation last? Does it clear up instantly or stumble past 4800rpm to redline?

Interesting... :)
 

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Discussion Starter · #14 ·
Thanks for your help. I'm not WOT. The car pulls smoothly and then at around 4800 on a light throtle I get the hesitaion. I can push past it by pushing the throttle down, but that only lessens the hesitation time: it still happens. If I stick at 4800 rpm, it will hesitate until I either back off or push the throtle. Once past 5200 or so excellent acceleration to my boost limit- which today was 1.03/1.08 bar. The hesitation occurs at around .65 to.68 bar.The EBC and boost gauge are dead on.

So far, i think it is one of several things. 1.- an ECU quirk as the MAP sensor reacts to the onslaught of boost-this is my second day with the EBC and earlier this year a similar thing occured in the first several days of my MBC.
2.- Error is installing the solenoid/vacuum lines.
3. EBC MAP sensor or ECU MAP sensor is fauly post-installation.
 

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Just want to clarify something here.

There are fuel cuts, and there are fuel cuts. There is no such thing as a boost cut. There is a fuel cut that is triggered by overboosting, which the ECU reads as a wastegate malfunction. This can occur between 16 and 19psi depending upon ambient barometric pressure. You can also hit a fuel cut by raising the engine RPMs too far into the redline.

Sorry if this sounds as though I'm being pedantic, but when you use the term 'boost cut' around newbies they get the impression that the ECU somehow cuts the boost. It does not.

On topic; I do not think you are experiencing an overboost-induced fuel cut. I have in the past triggered this many times on my WRX, and as somebody else stated, it will be more likely to happen in the higher gears when you start to push around 16psi or so.

-Pace
 

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Discussion Starter · #16 ·
Thanks for the guidance Pace. I didn't think there was a boost cut, just a fuel cut...but too much a newbie to state a firm opinion. Anyway, I'll let folks know about the remedy for this. EBC install OK and Vacuum lines ok. Looking at the MRT fuel cut lifter if problem persists. Again, my thanks to all as I'm just learning this stuff.
 

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Veritas,

I'm relatively sure that if you're not getting a CEL then we're not talking about overboost-induced fuel cut at this point... Still don't know where to look though. Hmmm. Have you tried the grounding mod? <-- on a lark :)
 

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Discussion Starter · #18 ·
Thank you. Will do and I'll take the EBC back to the shop for a thorough go-over. I'll let folks know of the results. BTW has anyone read the 01/02 "Turbo and High-Tech performance articles, page 40 for the Sparco WRX which employs an HKS fuel cut lifter and page 52 for the DSM Galant troubles with fuel cut during mod upgrades?
 
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