Graham1984 Posted November 12, 2011 Share Posted November 12, 2011 I had my Na 1st and 2nd decat the other day but for some reason when you punch the throttle it has a little lag moment almost like the power cuts off then back on again. I was wondering if that's due to where the backbox had all the silencing removed and I put the bung back in (although I made the exit hole slightly wider by removing the pipe) if it was just a build up of back pressure where it cannot escape through the hole causing the small lag? I would remove the bung but it is too loud so will have to put up with it until I either buy a new back box (with silencing) or the whiffbitzs cat back exhaust for people that have decatted their Na's although I was somewhat worried it may be another problem as well. It is probably nothing but seeing as you are the people to ask here I am. Quote Link to comment Share on other sites More sharing options...
AGB Posted November 12, 2011 Share Posted November 12, 2011 My car behaves the same with just one of the cats removed. I have to have the bung in because its just too loud otherwise (Nur spec exhaust). Im going to try a smaller 2.5" system with a couple of silencers to see if that makes any difference. Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 12, 2011 Author Share Posted November 12, 2011 It is just annoying as pre decat I don't think it ever did that unless it is just where it picks up better now which makes it more noticeable with the slight pause. I wondered if it may be blowing somewhere but doubtful but hoping the whifbitzs 2.5 cat back exhaust will cure it as the system is made for the high flow from the decats. Any suggestions to what it might be would be great no matter how dumb they sound as I hate when things do not run right! Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 12, 2011 Author Share Posted November 12, 2011 Memo to self do not start a thread I really want an answer to on a Saturday night! Quote Link to comment Share on other sites More sharing options...
AGB Posted November 12, 2011 Share Posted November 12, 2011 Ive heard that the NA's run too rich after removing the cats. That would explain the bogging down lower in the rev range. Im fairly new to this engine so im probably not the best person to ask but one thing I will say, In all honesty, every NA supra I have driven with their cats in place have run better and felt faster and more responsive than mine which is de-catted. I have not experienced the "Smoother and quicker response" that every man and his dog claims to have acheived after ditching the cats... Good luck finding the issue though! Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 12, 2011 Author Share Posted November 12, 2011 That is bad news for me then...... I am new to it all too but like you said everyone claims it is a tad better but I am yet to see it like you. At this rate I will be selling my decats and getting a standard 1st cat again which sucks after spending enough! Quote Link to comment Share on other sites More sharing options...
AGB Posted November 12, 2011 Share Posted November 12, 2011 Well don't take what I say as gospel either mate... Im just relaying my experience. I have read so many claims that the NA runs too rich lower down after removing the cats. If this is the case then the only way to reap benefits of a Decat is to have the car remapped or atleast adjust the fueling with an SAFC or something similar... Im not going to bother because im changing to FI when I can afford it.... Good luck mate! Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 12, 2011 Author Share Posted November 12, 2011 I thought most the problems were for the TT's not Na. Hopefully it is a simple fix though. Anyone else reading got any ideas?? Quote Link to comment Share on other sites More sharing options...
heckler Posted November 12, 2011 Share Posted November 12, 2011 Have you tried re-setting the ECU? Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 12, 2011 Author Share Posted November 12, 2011 No I have not tried that but might be a good call though Quote Link to comment Share on other sites More sharing options...
Neil-NA Posted November 13, 2011 Share Posted November 13, 2011 (edited) At what RPM does it feel like its lagging? don't forget if its below 4-4.5k the valve in the inlet mani wont have had chance to open yet, check any dyno sheet for an NA and their's always a dip in power and torque at this point, maybe this is what you are feeling, ikt is normally very noticable. TBH mine drives alot better with the cats in but only low down the revs Edited November 13, 2011 by Neil-NA (see edit history) Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 13, 2011 Author Share Posted November 13, 2011 Yeah I think that is what it must be then I vaguely remember it having a moment in 3rd or 4th around 80 or 90mph (on a track obviously). If I get pulled over I will just say Neil-NA said it is the only way to sort out the problem so I had too blast off from the lights in the town. Quote Link to comment Share on other sites More sharing options...
Neil-NA Posted November 13, 2011 Share Posted November 13, 2011 Yeah I think that is what it must be then I vaguely remember it having a moment in 3rd or 4th around 80 or 90mph (on a track obviously). If I get pulled over I will just say Neil-NA said it is the only way to sort out the problem so I had too blast off from the lights in the town. Just tell them its an NA, its impossible to break the speed limit Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 13, 2011 Author Share Posted November 13, 2011 Hahahaha hopefully that is a viable court defence. I took the fuse out and took it for a spin and it seams ok now and didn't lag but a lot more pokey higher in the rev range like you said which is a result. The only other thing I need to do is sort the raspy noise out which annoys me....... and add a turbo as well! Quote Link to comment Share on other sites More sharing options...
Neil-NA Posted November 13, 2011 Share Posted November 13, 2011 Not too sure what you can do with the rasp TBH, most seem to do it, some worse than others, mine sounds like a bloody Honda Quote Link to comment Share on other sites More sharing options...
AGB Posted November 13, 2011 Share Posted November 13, 2011 The raspyness Is what im trying to sort on mine.. At the moment I have a Nurspec with the bung in and it is horrible. I have a full 2.5" Stainless system with two silencers im going to butcher and fab up to fit the supra. Hopefully that will solve the raspyness. Quote Link to comment Share on other sites More sharing options...
Neil-NA Posted November 13, 2011 Share Posted November 13, 2011 Mine is a NUR spec R too and is just crazy loud and raspy but thats with an OBX manifold. Quote Link to comment Share on other sites More sharing options...
AGB Posted November 13, 2011 Share Posted November 13, 2011 Ahh yeah Stainless manifolds always do that. Have you thought about swapping/ cutting into your Decat pipe for a big Silencers box if there is room? Saves having to cut up the nurspec to quieten it down.. Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 13, 2011 Author Share Posted November 13, 2011 Think how I feel kakimoto back box with no silencing and a bung with a bigger hole in it which makes the worst sound of all. Hopefully the whiffbitzs kit for the decat folk sorts it out if not I am **** out of ideas. Quote Link to comment Share on other sites More sharing options...
AGB Posted November 13, 2011 Share Posted November 13, 2011 The best way to quieten down the raspyness is to fit a nice big turbo Quote Link to comment Share on other sites More sharing options...
Graham1984 Posted November 18, 2011 Author Share Posted November 18, 2011 Feel free to pay for it! Quote Link to comment Share on other sites More sharing options...
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