bolarbag Posted July 13, 2007 Share Posted July 13, 2007 Was speaking to a mechanic friend the other day and we had a little dispute... Apparently all Evo's with the exception of the MR models have a Flat Spot at around 3200-3700rpm in every gear. Dont know much about evo's so fair enough, Then I asked what was meant by a flat spot and was told that its to do with the fueling; it cant cope at this certain point and that the lack of fueling creates a flat spot. What I cannot understand is why would a manufacturer produce a car that under fuels at any part of rev range...wouldnt it be highly dangerous? Then he tells me that when test driving, it is so significant that he can actually feel it in every evo? Even modified ones with uprated fueling ecu's like an apexi power fc, its a characteristic? In the MR models apparently it as been resolved. Any truth in this? And what are flat spots? posted in this section because I reckon it might get a few tech replies;) I suggested it would be something to do with ignition timing, absurd apparently:search: Quote Link to comment Share on other sites More sharing options...
penguin Posted July 13, 2007 Share Posted July 13, 2007 wrong forum .... dont think its going to have any truth tho. Quote Link to comment Share on other sites More sharing options...
bolarbag Posted July 13, 2007 Author Share Posted July 13, 2007 Thought the Main question that would relate to all combustion engines is: explain a 'flat spot' Quote Link to comment Share on other sites More sharing options...
Chris Wilson Posted July 13, 2007 Share Posted July 13, 2007 The one here is bog stock and hasn't any flat spots. Quote Link to comment Share on other sites More sharing options...
bolarbag Posted July 13, 2007 Author Share Posted July 13, 2007 What model...and could ya enlighten me on what a flat spot is... Or is it B.S? Quote Link to comment Share on other sites More sharing options...
Ian R Posted July 13, 2007 Share Posted July 13, 2007 AFAIK owners that have had flat spot problems after fitting walbro's. The cure was to fit an adjustable regulator and droped the fuel pressure down a tad. Quote Link to comment Share on other sites More sharing options...
Ian C Posted July 13, 2007 Share Posted July 13, 2007 Moved to non-supra Tech. A flat spot is a noticeable drop in power for no apparent reason. The easiest cause of this is overfuelling as the combustion process starts to get quenched. Run about 9:1afrs and if it doesn't simply misfire it'll feel awful I very much doubt that an OEM vehicle would go out the door with a 500rpm flat spot in exactly the rev range most owners use on the street. Especially not a performance OEM vehicle, and certainly not a turbocharged one which has different performance across most of the rev range depends on what gear it is in (higher gear = higher load = turbo comes on earlier in the range = different power output for the same load site), so that blows the "every gear" comment out the water. And on top of that they are up to what, version ten of the Evo? Many different ECUs, engines, turbos, cams, etc etc and this same clanger every time? C'mon Someone is trying to act like they know more than you. -Ian Quote Link to comment Share on other sites More sharing options...
bondango Posted July 13, 2007 Share Posted July 13, 2007 Had a few EVO's, currently a 6, never had any flats spots under every day driving load conditions. Quote Link to comment Share on other sites More sharing options...
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