z-ya Posted September 3, 2009 Share Posted September 3, 2009 OK, hear is a good one for you. Lets see who can figure it out. I'll post the symptom, and info about the setup that is relevant. I've been trying to figure it out for weeks now, and had no idea what to try next. A friend made a suggestion that fixed it. So after a lap or two on a road course the engine falls flat on it's face when under full load. Probably down 50% on power, and the wide band gauge goes way rich (10:1 AFR). Setup: L28 NA Speed density based EFI (no MAF) EFI, ignition and fuel system tested and 100% functional No issues with engine mechanically 6:1 header, 2.5" exhaust, Supertrapp muffler Dual SU intakes with throttle bodies Let's see who can figure it out... Pete Quote Link to comment Share on other sites More sharing options...
FlatBlack Posted September 3, 2009 Share Posted September 3, 2009 Loose distributor shaft? Quote Link to comment Share on other sites More sharing options...
rags Posted September 3, 2009 Share Posted September 3, 2009 Pete, Are you running air filters? Joe Quote Link to comment Share on other sites More sharing options...
Administrators BRAAP Posted September 3, 2009 Administrators Share Posted September 3, 2009 Sparkplug heat range? Quote Link to comment Share on other sites More sharing options...
stravi757 Posted September 3, 2009 Share Posted September 3, 2009 loose battery connection? for some reason this is already driving me crazy, can u just PM me the answer...i swear i wont tell anyone haha Quote Link to comment Share on other sites More sharing options...
jeffer949 Posted September 3, 2009 Share Posted September 3, 2009 Clogged exhaust. very easy to do on the supertrap muffler Quote Link to comment Share on other sites More sharing options...
1 tuff z Posted September 3, 2009 Share Posted September 3, 2009 driver? sorry pete, i just couldn't resist! Quote Link to comment Share on other sites More sharing options...
JSM Posted September 3, 2009 Share Posted September 3, 2009 Your not running a PCV valve in anyway are you? Quote Link to comment Share on other sites More sharing options...
rags Posted September 3, 2009 Share Posted September 3, 2009 clogged exhaust. Very easy to do on the supertrap muffler +1 Map sensor going vacuum would pull fuel if the air filter was clogged or collapsing. Since the fuel is still being pumped into the motor because the EFI "senses" it needs it, I'm also going with a restriction in the exhaust. Joe Quote Link to comment Share on other sites More sharing options...
Guest Rolling Parts Posted September 3, 2009 Share Posted September 3, 2009 What kind of ECU do you have? What kind of ignition module do you have? What is the voltage on the systems when the WB reads full rich? Quote Link to comment Share on other sites More sharing options...
z-ya Posted September 3, 2009 Author Share Posted September 3, 2009 And the winner is..... Clogged exhaust. very easy to do on the supertrap muffler Yup, clogged Supertrapp. Now how would a Supertrapp all of a sudden get clogged? The car ran great at one event, and horrible at the next a few weeks later. More thought on this: - Speed density EFI does not look at air flowing through the engine like a MAF based system, only manifold pressure. So at full throttle (atmospheric pressure), the ECU injects the same fuel regardless of how much air is moving through the engine. Thus a clog in the intake or exhaust will show a rich condidtion. With a carburetor or MAF based EFI system you will not see a rich condiditon, just a loss in power. Quote Link to comment Share on other sites More sharing options...
z-ya Posted September 3, 2009 Author Share Posted September 3, 2009 driver? sorry pete, i just couldn't resist! Mmmm, this coming from someone I beat in the same car at an autocross..... Quote Link to comment Share on other sites More sharing options...
EvilC Posted September 3, 2009 Share Posted September 3, 2009 Mmmm, this coming from someone I beat in the same car at an autocross..... WOW I saw that one coming! Quote Link to comment Share on other sites More sharing options...
srgunz Posted September 4, 2009 Share Posted September 4, 2009 I ran a supertrapp on mine. I did not like the setup after I noticed the carbon build up around the stack of plates. I took the end cap off and ran it that way with 2 stacks of plates only. Sounded great! I also had an early 2-1/2in. MSA exhaust that had at the time a cheap no name turbo muffler as part of the kit. That plugged up on me just like yours. I think it was a combination of rust and carbon. (tripple mikunis) How did I test it you ask? I took it off and stuck the garden hose in the inlet and it filled up and only dripped out the exit!! Now when I see a supertrapp being used, I suggest removal ASAP!! Or remove the end cap. Quote Link to comment Share on other sites More sharing options...
z-ya Posted September 4, 2009 Author Share Posted September 4, 2009 Yes, it was rust (or scale) that had vibrated loose from the inner metal mesh that holds the packing in. So enough of it loosened up, and when the engine is running, it only has one place to go, into the diffusers. My suggestion is to remove the discs on a regular basis to check for rust buildup inside the muffler. While your at it clean the discs. Pete Quote Link to comment Share on other sites More sharing options...
JessZ Posted September 4, 2009 Share Posted September 4, 2009 My car fell flat while driving to Texas form California. The screw that holds my distributor to the spinning cam came loose. I put it back and kept driving. Hope this helps. Quote Link to comment Share on other sites More sharing options...
z-ya Posted September 4, 2009 Author Share Posted September 4, 2009 My car fell flat while driving to Texas form California. The screw that holds my distributor to the spinning cam came loose. I put it back and kept driving. Hope this helps. I guess you didn't actually read any or my posts.... Pete Quote Link to comment Share on other sites More sharing options...
HowlerMonkey Posted September 5, 2009 Share Posted September 5, 2009 I'll guess you aren't running this on the street in extended running? If you are, does this happen about 5 to 10 minutes into the run cycle regardless of loading? Many sensors can "fail" either at a certain temperature. As the car warms up through that range, the sensor fails to send the proper signal and the ecu ignores it and dumps fuel. When I supported the ecus my company manufacturers, I got 5 calls a week from people that had a car that would run great and suddenly dump fuel just at the end of the warm-up cycle. So I've seen it about 700 times. Quote Link to comment Share on other sites More sharing options...
woldson Posted September 5, 2009 Share Posted September 5, 2009 Ummmmm, teehee... Quote Link to comment Share on other sites More sharing options...
z-ya Posted September 5, 2009 Author Share Posted September 5, 2009 I'll guess you aren't running this on the street in extended running? If you are, does this happen about 5 to 10 minutes into the run cycle regardless of loading? Many sensors can "fail" either at a certain temperature. As the car warms up through that range, the sensor fails to send the proper signal and the ecu ignores it and dumps fuel. When I supported the ecus my company manufacturers, I got 5 calls a week from people that had a car that would run great and suddenly dump fuel just at the end of the warm-up cycle. So I've seen it about 700 times. Dude, it was the muffler...... Quote Link to comment Share on other sites More sharing options...
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