Andrew Posted November 15, 2001 Share Posted November 15, 2001 Think I have a mojor problem here. Normal driving the car runs fine, no problems. But when I accerlerate hard to 5000/6000 revs the car makes a banging noise, and jolts back (likened to going over a deep pot hole at speed). Now this only happens at high revs and usually in 3rd although it has happened in 4th and sometimes 5th. You can change up and the car continues again until you reach high revs. My main consern is that the engine light came on last night for a few seconds then went out. The thing is this doesn't happen all the time and for the life of me I cannot work this out. It is an import and still has it's jap limiter on, so I thought it could have something to do with that. The only mod is an exhaust and as far as I know no other mods. Any comments would be most appreciated. Cheers Andrew Quote Link to comment Share on other sites More sharing options...
Brian Jackett Posted November 15, 2001 Share Posted November 15, 2001 Do you know what boost pressure you are running. Do you still have cats in? I get that sometimes because my boost pressure is to high Quote Link to comment Share on other sites More sharing options...
Mark Ayling Posted November 15, 2001 Share Posted November 15, 2001 Sounds like you're hitting fuel-cut to me... Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 No all cats are out, and I do not have a boost gauge so no idea there I'm afraid. I forgot to mention but I had changed my fuel to Shell Optimax, then had to change back to regular fuel when I got caught short no where near a Shell garage. When it happen to you did the engine light come on? Another thought was that it still has the toyota bov(dump valve) maybe this needs upgrading? Also would I boost higher in cold weather? Quote Link to comment Share on other sites More sharing options...
Guest Ash Posted November 15, 2001 Share Posted November 15, 2001 Sounds to me like you are hitting fuel-cut. Going hell for leather then suddenly... BANG... feels like your engine just dropped out and the MIL illuminates for a few seconds. Just as you are wondering what the f*ck happened, everything continues as normal. Happens to cars that have had cats removed or boost controllers fitted. Yours, J Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 Ash you couldn't have explained it better Frightened to shite out of me. Is there anything I can do to get rid of it? Quote Link to comment Share on other sites More sharing options...
Adam W Posted November 15, 2001 Share Posted November 15, 2001 You can fit a "Fuel Cut Defender", available from TRL (aka Pete Betts) or HKS. This tricks the ECU into thinking that the boost rpessure is below the cut-off limit. Which is all well and good . .. BUT Ash has recently raised some issues regarding the safety of fitting this item. Plenty of members have one fitted with no problems, but you may want to research the issue by looking at old threads on the BBS. A search for FCD should find plenty of info. Also, getting a boost gauge woould be an EXCELLENT idea . . . fuel cut is at 14psi - you might be just hitting 15psi (OK) or boosting way up to 22psi or something (not OK) and you have no way of telling which at the moment. An FCD will allow your engine to boost to destruction if you let it! Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 Thanks I'll check this out. Just to easy my mind, If I leave things as they are will it damage the engine or is the ECU doing what it should by protecting my engine? Quote Link to comment Share on other sites More sharing options...
Doughie Posted November 15, 2001 Share Posted November 15, 2001 Andrew I agree with the other comments that most likely you are hitting fuel-cut. Happily there is a solution : fit a fuel-cut defencer. visit : www.trlperformance.com where you can find some info on it. Look for : VFCC (Voltage Fuel Cut Controller) only 60 or 70 quid. this should stop your car going "bang" but you need to make sure you're not boosting too high so get a boost guage fitted too to monitor the boost you're getting, otherwise your car may go "bang" in a rather bigger way than it currently is........ Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 Bloody hell this board moves quick , thanks again for the info. Quote Link to comment Share on other sites More sharing options...
Brian Jackett Posted November 15, 2001 Share Posted November 15, 2001 You must buy a boost gauge, you could be hitting excessive boost which is not good for your car. Quote Link to comment Share on other sites More sharing options...
Steve Cargill Posted November 15, 2001 Share Posted November 15, 2001 Andrew, I asked a similar question a little while ago - does hitting fuel cut do any harm. The general consensus is that it doesn't in itself as it is protecting the engine, bbut when it cuts it does put quite a large abount of stress on the engine and drivetrain, so is generally not good. I only hit it twice, both times under extreme conditions - WOT for 10 seconds and getting to 130ish. In the last couple of weeks I've hit it three times, once at 75MPH!!! I've swiched to Oprimax and the air is colder. I've got a boost gauge that I'm about to fit (50ish quid from SHOP!) to see what I'm actually running as I've no idea what electronics are secreted in the car..... Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 Yeah looks like a safe bet getting one fitted. My old MKIII had a boost gauge, just strange Toyota didn't continue putting them in the Supra, could be an aftermarket ploy I guess. Quote Link to comment Share on other sites More sharing options...
Adam W Posted November 15, 2001 Share Posted November 15, 2001 I guess for 90% of end users, it makes no difference whether they're hitting 8psi or 12psi. At least, they don't need to know the numbers as long as the car accelerates nicely! It's only when you want to start tuning the car that you need to know what's going on under the bonnet. The stock Mk3 gauge isn't renowned for it's accuracy, so many people who start tuning them fit an aftermarket gauge in the same way as MkIV owners do. Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 Yeah fair comment Adam, after I took my MKIII to BPU the boost gauge become redundant. But it was nice to see the needle shoot off the gauge Quote Link to comment Share on other sites More sharing options...
Guest Ash Posted November 15, 2001 Share Posted November 15, 2001 If you do fit some kind of fuel-cut getaround then please pay heed to the last line of Adam's last post. Fitting a fuel-cut defencer really does allow your engine to boost to destruction. If it were not for the fact that the MKIV motor has some really trick knock-sensing equipment then quite a number of engines would have gone bang many moons ago. Yours, J Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 That's the worring thing Ash, I use my Sup for work and wouldn't want to blow the thing to pieces. This my seem a little nieve but would an upgraded dump valve relieve some of the presure. Not sure how it works myself Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted November 15, 2001 Share Posted November 15, 2001 No an upgraded dump valve will not help at all. All that does is make a nice sound (if it dumps to atmosphere) and is more reliable under higher boost pressures, compared to stock. After fitting the FCD the best thing you can do is install something to control boost pressure :- Bleed Valve - Cheap (less than £10) and you will defenitely need a boost gauge to set accurately. EBC - Electronic Boost Controller, not so cheap but have more options and usually some sort of in built boost gauge. MBC - Mechanical Boost Controller, consists of a ball and spring arrangement, more accurate than the bleed valave. HTH Martin Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 Looks like I'm going to have to have a think about this, dump valves are easy to fit. When it comes to ECU electrical stuff I'm hopeless. Any suggested upgrade places I can take it to in the London area. Quote Link to comment Share on other sites More sharing options...
Guest Martin F Posted November 15, 2001 Share Posted November 15, 2001 Best to give Leon Green a call on 07956 285219, he is based in Watford and specialises in Supra's. Only thing is he is very popular and hence very busy. Quote Link to comment Share on other sites More sharing options...
Andrew Posted November 15, 2001 Author Share Posted November 15, 2001 Cheers Martin, I remember Leon from the uksupra smartgroups page. Quote Link to comment Share on other sites More sharing options...
Brian Jackett Posted November 16, 2001 Share Posted November 16, 2001 Bleed valves etc.. can only increase boost pressure you cannot reduce it. Thats why I am going to have to fit a restrictor in my exhuast. Thats what I have been told regards Quote Link to comment Share on other sites More sharing options...
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