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This is a discussion on Engine cutting out at full throttle within the Engine Modifications forums, part of the Tech & Modifying & General Repairs category; can we stop with the MBC are the devil ideas. MBC is the devil if you dont understand your car ...

  1. #16
    Registered User AwdTurboWrx's Avatar
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    can we stop with the MBC are the devil ideas. MBC is the devil if you dont understand your car and you cant use it. I had a mbc on my 03 wrx for 18 months with up/dp/catback and i would make sure it only hit 17psi in 5th gear. I would beat cobb stage 2 wrx's off a roll and off a stop too. I would even trap higher then they would at a drag strip. Best 60 dollars i ever spent for that car. If you have an 02/03 bugeye its a perfect mod if you just know how to use it. I even dynoed my car and a/f was fine. Nothing even close to dangerous. As long as your catless and you have an 02/03 its perfectly fine. JUst dont overboost, all your doing from the sounds of it is hitting limp cause your overboosting witht he mbc. Just get a boost gauge and make it so 4th gear it only hits 16 psi which means it will hit like 16.5-17 in 5th and you'll be fine.
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  3. #17
    Registered User cheeseybacon's Avatar
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    Quote Originally Posted by AwdTurboWrx
    can we stop with the MBC are the devil ideas. MBC is the devil if you dont understand your car and you cant use it. I had a mbc on my 03 wrx for 18 months with up/dp/catback and i would make sure it only hit 17psi in 5th gear. I would beat cobb stage 2 wrx's off a roll and off a stop too. I would even trap higher then they would at a drag strip. Best 60 dollars i ever spent for that car. If you have an 02/03 bugeye its a perfect mod if you just know how to use it. I even dynoed my car and a/f was fine. Nothing even close to dangerous. As long as your catless and you have an 02/03 its perfectly fine. JUst dont overboost, all your doing from the sounds of it is hitting limp cause your overboosting witht he mbc. Just get a boost gauge and make it so 4th gear it only hits 16 psi which means it will hit like 16.5-17 in 5th and you'll be fine.
    Look, just because you personally did not observe problems with an MBC on your car doesn't mean it won't cause problems for others, and it DEFINATELY doesn't mean that it wasn't causing unnecessary engine stress, simply because you didn't observe any. The 02-03 isn't magical, and special and all that different from the later model WRXs. The only major difference with the 02-03s is there isn't a dangerous delay between the switch from closed loop and open loop. They still run lean when you increase the boost without providing additional fuel, just like any other car and they still experience part-throttle full boost with a MBC as well.
    Last edited by cheeseybacon; 03-07-2006 at 04:40 PM.
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  4. #18
    Registered User AwdTurboWrx's Avatar
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    Quote Originally Posted by cheeseybacon
    Look, just because you personally did not observe problems with an MBC on your car doesn't mean it won't cause problems for others, and it DEFINATELY doesn't mean that it wasn't causing unnecessary engine stress, simply because you didn't observe any. The 02-03 isn't magical, and special and all that different from the later model WRXs. The only major difference with the 02-03s is there isn't a dangerous delay between the switch from closed loop and open loop. They still run lean when you increase the boost without providing additional fuel, just like any other car, and they still experience part-throttle full boost with a MBC as well.

    i put it on a dyno and was still running RICH at 17 psi. Dyno was at ESX. Like i said, its a great mod if you know how to use it.
    The Ghosts of Zooph and Sarcasmo Will haunt CLUBWRX forever!!!

  5. #19
    Registered User cheeseybacon's Avatar
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    Quote Originally Posted by AwdTurboWrx
    i put it on a dyno and was still running RICH at 17 psi. Dyno was at ESX. Like i said, its a great mod if you know how to use it.
    Define rich, please.

    And if what you're saying is true, and the WRX runs hog rich at 17 psi with the stock programming then why has Cobb and all these other engine management companies even bothered making stage 2 maps for 02-03? Is it all a total sham? Are all the 02-03 people running Stage 2 being ripped off? Have we been fooled all this time? Somehow I doubt that. Furthermore, if things are so rich at 17 psi as you claim, then why have the EM powers that be even bothered making different fuel maps for the 04-05 as well? If everything is safely running as rich as you claim it is, couldn't they have just make a reflash that shortens the CL/OL delay on the 04-05s and then called it a day?
    Last edited by cheeseybacon; 03-07-2006 at 04:36 PM.
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  6. #20
    Registered User Fox05's Avatar
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    Quote Originally Posted by AwdTurboWrx
    can we stop with the MBC are the devil ideas. MBC is the devil if you dont understand your car and you cant use it. I had a mbc on my 03 wrx for 18 months with up/dp/catback and i would make sure it only hit 17psi in 5th gear. I would beat cobb stage 2 wrx's off a roll and off a stop too. I would even trap higher then they would at a drag strip. Best 60 dollars i ever spent for that car. If you have an 02/03 bugeye its a perfect mod if you just know how to use it. I even dynoed my car and a/f was fine. Nothing even close to dangerous. As long as your catless and you have an 02/03 its perfectly fine. JUst dont overboost, all your doing from the sounds of it is hitting limp cause your overboosting witht he mbc. Just get a boost gauge and make it so 4th gear it only hits 16 psi which means it will hit like 16.5-17 in 5th and you'll be fine.
    Why buyeye models only?
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  7. #21
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    Quote Originally Posted by Fox05
    Why buyeye models only?
    because 04 and after have a different ECU, and there is a lag b/w open and closed loop fueling that will cause the car to run dangerously lean for a short period.

    in an 02/03, MBC/EBCs are okay, if you understand what's happeneing, and watch your guages. After a couple weeks, you just learn to drive differently to keep yourself out of the danger zones.

    i could never get comfortable with mbcs, b/c in boston, the temp changes so rapidly, you'll have to adjust the mbc under the hood twice a day!. at least with an ebc you can adjust from the cabin.

    it's a great way to get power (on the 02/03), but like everything else, you need to understand the metrics of the mod, and need to understand there is risk involved.

  8. #22
    Registered User cheeseybacon's Avatar
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    Quote Originally Posted by Fox05
    Why buyeye models only?
    Bugeye models (02-03s) do not have a long delay when they switch from closed-loop to open loop like the 04+ models do. During this long delay while the ECU switches modes, the 04+ models can run crazy lean with a MBC. This means that bugeys are LESS dangerous to use with a MBC at least from the standpoint of the CL/OL delay. Notice I said, LESS dangerous with MBCs, not completely safe. Part-throttle/full boost issues, and running lean due to higher boost with no fueling compensation from ECU still apply to the 02-03s just like any other year.
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  9. #23
    Registered User Kush's Avatar
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    Quote Originally Posted by 04.SPT.WRX
    Welcome Kush!
    Thanks!

    Quote Originally Posted by cheeseybacon
    I think we've got everything well on it's way to being straightened out though, right Kush?
    Absolutely, I can't thank you enough for all the great advice. I've learned more in the last 5 hours than I have since I've owned the car. I'll be hanging out here for a long time, thats for damn sure.

    Quote Originally Posted by 04.SPT.WRX
    Hi hew guy ... 70's Camaro? How old are you? I am old enough to clearly remember 70's Camaros when new.
    I'm 21. Sadly not old enough to remember them when they were new, though in high school I had a decent '70 1/2 split bumper camaro. Loved it, though the reliability was a factor when I had to drive back and forth to college, which is why I bought the WRX.
    Last edited by Kush; 03-07-2006 at 05:22 PM.

  10. #24
    Registered User Kush's Avatar
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    Quote Originally Posted by cheeseybacon
    Yepper, that looks exactly like you have a cold air intake! Get rid of that sucker and put the stock airbox back in place, but don't worry you don't need a conical air filter on the end of the intake like the picture that I posted, just the original stock airbox will do nicely.
    I'll put that on the list, that's an easy change-out


    You might need a bigger/different MAF if you have a huge watermellon sized turbo that couldn't utilize the stock turbo inlet tube, but other than that the stock MAF sensor is fine, and more than adequate for most aftermarket turbos as well. Actually, after a certain a boost level/rpm is reached, the ECU stops making fueling decisions based on it's sensors (closed-loop) anyway. At that point, the sensors that the ECU has been using to adjust the A/F can't react fast enough to provide accurate data, so the ECU switches over to open-loop operation, where it provides fueling based on a table of preset fueling values called a map. That's why engine management and new mappings are so important. The boost controller you have might be forcing your turbo to provide 17 psi of boost without any problem, but your ECU is still only mapped out to provide enough fuel to keep things safe for 13.5 psi of boost.
    Thats what I though was happening, though I didn't know enough about this system to know exactly why. So when the ECU switches to open-loop, the maps that it accesses, when an EM is set up, are stored in the EM unit and not on the Subaru ECM? And I'm assuming that this has nothing to do with the o2 sensor open/closed loop.

    Thanks again, have you thought about a career in engineering?
    Last edited by Kush; 03-07-2006 at 05:27 PM.

  11. #25
    Registered User cheeseybacon's Avatar
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    Quote Originally Posted by Kush
    Thats what I though was happening, though I didn't know enough about this system to know exactly why. So when the ECU switches to open-loop, the maps that it accesses, when an EM is set up, are stored in the EM unit and not on the Subaru ECM?
    The Cobb AccessPort reflashes your stock Subaru ECU/ECM with the new mappings via the OBDII port underneath the dash. Once the reflash is finished, you can put the AccessPort away somewhere and drive without it until the next time you need to change the mapping. If you get a bigger turbo (that isn't a VF30 or VF34) or do modifications for which there isn't a pre-made AccessPort map, or just plain want more power than the generic "one-size-fits-all" maps that the AccessPort comes with, you can always take your car to a tuner that has the Cobb's Tuner software. They will dyno tune your car and develop a customized map that is tailored to your specific car and setup.

    Alternatively, you can go to a tuner and get a custom dyno tune/reflash via Ecutek. The Ecutek reflash works much the same way the AccessPort does in the sense that your stock ECU's map is replaced with a new one. The only difference is, you skip the middleman completely, which is the AccessPort. With an Ecutek tune/reflash you do not have to buy any engine management hardware at all. The tuner reflashes your ECU with his own equipment and then off you go. All you pay for is the cost of the tuning labor, no hardware or anything extra to buy. The only downside to this is if you get some new mods or step up to a bigger turbo or something, then you have to return to the tuner for another map/tune, you don't have the option of just switching to a different map like with some other EM solutions.

    Other types of EM, such as the TurboXS UTEC, are piggyback units. They do things a little different. Under light load/low RPM (closed loop conditions) the stock ECU adjusts the A/F mixture, but when open loop is engauged, the UTEC takes control of the fueling duties based off whatever map is loaded into the UTEC. Again, you can go to a tuner and have a custom map made just for your particular setup or utilize generic off the shelf maps that are provided with the unit.


    Quote Originally Posted by Kush
    Thanks again, have you thought about a career in engineering?
    Funny you mention that. That's exactly the field I'm in.
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  12. #26
    Registered User Kush's Avatar
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    ok, let me make sure I have this right:

    Option 1: Use AccessPort to reflash my ECM mapping.
    Pros: I can re-flash at any point if I make any future mods. If I do a mod that has no pre-set map, a tuner can make one for me and store it in my AccessPort for future use.

    Option 2: Dont buy the AP, but get the ECM dynoed and reflashed by a tuner.
    Pros: I dont need to spend money on the AP.
    Cons: I have to go back to a tuner to reflash the ECM every time I make a mod.

    Option 3: Piggyback Unit

    What is the average cost of having a tuner dyno and reflash the ECM? If its a few hundred bucks, I might as well get the AP so that I can switch between maps and have them all stored with me. If its much cheaper, is there a reason I'd want to get the AP if I can just take a trip to a tuner?

    Aaron
    Last edited by Kush; 03-07-2006 at 06:13 PM.

  13. #27
    Registered User cheeseybacon's Avatar
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    If you don't ever plan on getting a custom dyno tune and just want to safely increase your boost with the stock turbo and don't want to take the modifications any farther than that, just get an AccessPort and be done with it, it's by far the easiest, most conveinient solution available.

    Otherwise, if custom tunes and bigger turbos and all that fun evil stuff are something you're interested in, what you need to do first is seek out the tuners in your area and see what kind of engine management they are most comfortable with using. Most tuners have only one type of engine management that they prefer using.

    It would be kinda pointless to drive 3 hours away to get a custom tuned map for your AccessPort when a tuner 15 miles away works with UTEC, know what I mean?
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  14. #28
    Registered User Kush's Avatar
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    I think for now, for this particular car, I won't make any mods past the stage 2. Mostly because I can't afford the thousands it would take to do it, and also...well just because I dont have the cash So my best option then would be to get the AP.

    Just did that now actually, just purchased the AccessPoint and an uppipe with OEM gaskets which should both be here in a couple of days ($6 for next day shipping!), and I'll try to find a stock intake system on Ebay, remove the MBC (maybe drive it around to see what the car feels like stock), then mess with the AP for a while and install the uppipe. I'm sure I'll have another 2 pages of questions once I get the delivery, but until then, thank you for everything, you've definately opened my eyes to this stuff. Now I can't wait to set it all up!

    What kind of engineering do you do?

  15. #29
    Registered User cheeseybacon's Avatar
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    Quote Originally Posted by Kush
    I think for now, for this particular car, I won't make any mods past the stage 2. Mostly because I can't afford the thousands it would take to do it, and also...well just because I dont have the cash So my best option then would be to get the AP.

    Just did that now actually, just purchased the AccessPoint and an uppipe with OEM gaskets which should both be here in a couple of days ($6 for next day shipping!), and I'll try to find a stock intake system on Ebay, remove the MBC (maybe drive it around to see what the car feels like stock), then mess with the AP for a while and install the uppipe. I'm sure I'll have another 2 pages of questions once I get the delivery, but until then, thank you for everything, you've definately opened my eyes to this stuff. Now I can't wait to set it all up!

    What kind of engineering do you do?
    Research and development for large displacement (11+ liters) diesel powertrains
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  16. #30
    Registered User Kush's Avatar
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    nice, sounds like a fun job

    parts won't be here until next friday, so I guess I gotta wait it out
    In the meanwhile I turned down the MBC so it seems to be running alot better now, though substantially slower

    Oh well, all in good time
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