Tom Posted February 9, 2005 Share Posted February 9, 2005 On my way back from the bluewater meet last night I had a chance to check my boost levels on the M25, I did about 8 runs from 3k in 6th gear, I always hit 0.7 on the first turbo and at about 3600-3800(once 3400) I hit 0.9 and then once at 4k and above the boost would drop down to 0.7 till my limiter! I still feel the 2nd coming on but shouldn't I hit 0.9 and for it to stay there till I let off? I've even noticed that the first time I push the car after starting up(from cold) that I'll hit 0.9 in 3rd or 4th and any time after that it it'll be 0.8 or lower. Any idea's? I've recently replaced a lot of my hoses and they seem fine. Link to comment Share on other sites More sharing options...
LeeT Posted February 9, 2005 Share Posted February 9, 2005 you should look over on supraforums and search 'spring mod' . that sounds like your problem. basically means fitting a spring to your wastegate and the other end to your water pump. this will let you hold boost till red line Link to comment Share on other sites More sharing options...
Ian C Posted February 9, 2005 Share Posted February 9, 2005 Or you could diagnose and then fix the problem? Have you got any decats or a boost controller or anything? -Ian Link to comment Share on other sites More sharing options...
Tom Posted February 10, 2005 Author Share Posted February 10, 2005 Or you could diagnose and then fix the problem? Have you got any decats or a boost controller or anything? -Ian Nope cats in and no boost controller, does that narrow it down at all? Link to comment Share on other sites More sharing options...
Tom Posted February 10, 2005 Author Share Posted February 10, 2005 I've been reading the spring mod on sf and it does look promising, but surely it should just hold boost till redline anyway? Link to comment Share on other sites More sharing options...
LeeT Posted February 10, 2005 Share Posted February 10, 2005 I've been reading the spring mod on sf and it does look promising, but surely it should just hold boost till redline anyway? not if you've got a weak wastegate spring. im no expert but it certainly sounds like your problem to me Link to comment Share on other sites More sharing options...
Tom Posted February 12, 2005 Author Share Posted February 12, 2005 I checked a lot of the IC pipes and a couple of them were quite loose and I was hoping that once tightned it would solve my problem, but it hasen't! I was on the m25 last night and did some more runs, this time I dropped down to 3rd from about 70/80 it was about 5k, I floored it from here and it stayed at 0.6. It's really bugging me now! Regarding the spring, is there one there already which I would just replace? and has anyone else done it on here? Link to comment Share on other sites More sharing options...
Tom Posted February 12, 2005 Author Share Posted February 12, 2005 Right I might be getting somewhere now! I tried the TTC mod and I believe I'm hitting fuel cut, I hit 1.2bar! remember that I'm stock bar catback exhaust, surely that's way too high for stock?????? the boost was holding till that point too. what does this mean??? I'll have to do more testing as it was too wet really and it went up to 1.2 then dropped to 1.0 Please help!!! Link to comment Share on other sites More sharing options...
Tom Posted February 12, 2005 Author Share Posted February 12, 2005 Ok car seems to be pulling real well! it still spikes at 1.2 in 3rd then drops to .8 which it stays till redline which is nice! I found that I've even hit 1 bar in 1st!, the exhuast note is nice and I think I love TTC! this fuel cut thing though, I haven't notice it really slow me down the car just keeps pulling hard all that happens is a sort of fluttering sound in the exhaust when I hit over 1 bar. How bad is it for the car to hit fuel cut? Link to comment Share on other sites More sharing options...
addi Posted February 14, 2005 Share Posted February 14, 2005 ud know about it if you was hiting fuel cut mate, it feels like ur engine has just given up the ghost lol Link to comment Share on other sites More sharing options...
Ian C Posted February 14, 2005 Share Posted February 14, 2005 Sounds more like your spark plugs aren't a cold enough grade for the level of boost and are misfiring intermittently. FAQ Boost drops off as the rpms get higher anyway, but it shouldn't be to 0.6bar, you should be seeing 0.8bar on a stock setup if your boost gauge is plumbed into a feed from the intake plenum. Perhaps you have a slight leak in an air hose that only manifests under boost? Could be something to do with the sequential system if you get a dropoff in boost once #2 comes online, especially if it's spiking to 0.9+bar on transition, sounds like something is slightly awry. -Ian Link to comment Share on other sites More sharing options...
Tom Posted February 14, 2005 Author Share Posted February 14, 2005 Hmmm... I had the plugs changed about a month ago with the standard toyota one's ie ones from factory(maybe there not cold enough?), the way it's going at the moment in ttc is the boost gauge will fly round to 1.2 then bounce back down to .8(very quickly but forced by something stopping it staying there), It does feel like the car slows down but the warning triangle light doesn't come on when this happens which I believe people have mentioned happens when hitting fuel cut? Link to comment Share on other sites More sharing options...
Tom Posted February 14, 2005 Author Share Posted February 14, 2005 What would be the noise through the exhaust I hear? I feel a sort of vibrating bass sound! this only happens when I think I'm hitting FC. Link to comment Share on other sites More sharing options...
Justin Posted February 14, 2005 Share Posted February 14, 2005 I'd listen to Ian C mate. It is plugs that you need to look at. I had the same symptoms. Get to high boost at WOT then a rasberry sound from zorst and spluttery acceleration. I got colder plugs and everything was great after that. Fuel cut - you'd notice this much more. It's like driving off a cliff with a long rope attached to your rear axle. The fuel cut sensation hits when the rope goes tight! (PS - I shat myself on my first fuel cut as I thought I'd blown my engine ;-) Link to comment Share on other sites More sharing options...
Tom Posted February 15, 2005 Author Share Posted February 15, 2005 Yeah I believe Ian is totally correct! Thanks Ian! I'm going to be changing back to Seq today as I don't want to ruin the new plugs! bit gutted though as they were about £60. So the conlcusion is that the car boost's great in TTC but not as good in Seq(not holding boost till redline) but If I had a boost leak surely it would not hold till redline in TTC either? so maybe there's something wrong with what the temporary ttc mod bypasses? Link to comment Share on other sites More sharing options...
Tom Posted February 15, 2005 Author Share Posted February 15, 2005 Ok I'm back to sequential, and well it's still playing up, sometimes it'll go up to 0.8 but only briefly and sometimes when no 2 comes on no added boost. I'm sure it's something really silly and simple to fix! like I said it's perfectly fine in ttc, well more than perfect as there's a lot of boost being made, say I had colder plugs and running in ttc It would probably then go to fuel cut as it would be round the boost gauge just that little bit further! but it's sequential I want to run in. I think if everything else is ok it must be on of the vsv's? Link to comment Share on other sites More sharing options...
normore1 Posted February 16, 2005 Share Posted February 16, 2005 If you are getting higher max boost in TTC then you have a problem with your sequential control system, most likely with your IACV actuator or VSV. Another likely area is the vacume hoses. The problem you are seeing at high boost (1.2 bar) is ignition miss. Contrary to what ha s been said previously this will not be cured by going to colder plugs. Colder plugs fix pre-ignition problems associated with higher boost not a miss. The miss is caused by too much spark plug gap which is unable to ignite the denser fuel mixture. Stock is 1.1mm and you need to go down to at least 0.9 mm to stop the missing. Since you need a smaller gap you might as well get a colder plug at the same time. Denso Iridium IK22 are a little expensive but have the right gap (0.9 mm) and are one heat range colder than the stock NGK BKR6EP-11. The upside is they will likely last 50K+ miles. Good luck with tracking down your sequential boost problem. Link to comment Share on other sites More sharing options...
Tom Posted February 16, 2005 Author Share Posted February 16, 2005 Thanks for that, some more things to look into, cheers. Link to comment Share on other sites More sharing options...
Tom Posted February 16, 2005 Author Share Posted February 16, 2005 This morning while running in seq the car boosted fine to 0.9 and held it there, but I know that a few runs after that it probably woon't boost that high or stay there all the way to redline, tbh it's not a massive drop, it may go from 0.8 to 0.75 but I find it strange that it will work perfectly the first time and not after that. Any idea's how much are actuators and vsv's are? Link to comment Share on other sites More sharing options...
Tom Posted February 17, 2005 Author Share Posted February 17, 2005 From looking at the faq, to me there's a lot more hoses that I need to replace(the ones at the back) I'm thinking though that it could still be a split hose, as if in the morning its fine and on the way home from work, during the day the hose has had time to seal up, but once I've started boosting it's opening the split and allowing air to escape, does that sound plausable? Link to comment Share on other sites More sharing options...
Ian C Posted February 17, 2005 Share Posted February 17, 2005 If you are getting higher max boost in TTC then you have a problem with your sequential control system, most likely with your IACV actuator or VSV. Another likely area is the vacume hoses. The problem you are seeing at high boost (1.2 bar) is ignition miss. Contrary to what ha s been said previously this will not be cured by going to colder plugs. Colder plugs fix pre-ignition problems associated with higher boost not a miss. The miss is caused by too much spark plug gap which is unable to ignite the denser fuel mixture. Stock is 1.1mm and you need to go down to at least 0.9 mm to stop the missing. Since you need a smaller gap you might as well get a colder plug at the same time. Denso Iridium IK22 are a little expensive but have the right gap (0.9 mm) and are one heat range colder than the stock NGK BKR6EP-11. The upside is they will likely last 50K+ miles. Good luck with tracking down your sequential boost problem. Well, the colder grade of plugs suggestion was to cure the misfire at 1.0bar+ because boost levels that high overheat a warmer grade plug and causes it to stop sparking now and again. It wasn't to cure the sequential problems at all, I *know* the plugs aren't the issue there Colder plugs fix preignition that is caused by warm grade plugs creating hot spots on the cathode (or is it anode, I never can remember) but that's a more advanced and extreme manifestation of the problem. They don't fix preignition or det caused by too high a boost level, that's the octane of your fuel, compression ratio, ignition timing to some (haha) degree, and charge temps which cause that. Pretty much all plugs came pregapped to 0.8mm I thought, which is what I'd recommend running the colder grade at. Tony - try homing in on the IACV hoses to start with. -Ian Link to comment Share on other sites More sharing options...
Tom Posted February 18, 2005 Author Share Posted February 18, 2005 Tom - try homing in on the IACV hoses to start with. -Ian I've edited that for you:p Actually I'm going to change my name to Tony, well guessed Link to comment Share on other sites More sharing options...
normore1 Posted February 18, 2005 Share Posted February 18, 2005 Ian, the high speed miss that is experienced by Supra's at higher boost levels with stock plugs is due to too big a gap and not due to elevated plug temperatures. Stock plugs are definitely 1.1mm. The problem with the stock plug is that the energy generated across the large gap is not high enough to ignite the denser mixture provided at high boost. Gapping down the stock plug will fix the miss but then you could have some pre-ignition at high boost levels. A colder plug may be required but is not necessary for BPU mild increases of ~1.2 BAR. Singles and even BPU in hot climates may need a colder plug (NGK range 7 or Denso 22). However, changing plug heat range only will not fix the miss unless the lower heat range plug also has a smaller gap. Typically 0.8 - 0.9mm is OK for up to 1.3 BAR to stop miss. The rule of thumb is to lower gap by ~0.2mm from stock for each 75 additional HP. If HP is increased by more than 150 above stock (>500 HP) you may also need to increase spark energy to stop a miss. Your explaination of the relationship between plug temperature and pre-ignition has a number of misconceptions. Here is some info from NGK: The temperature of the spark plug's firing end must be kept low enough to prevent pre-ignition, but high enough to prevent fouling. This is called "Thermal Performance", and is determined by the heat range selected. It is important to remember that spark plugs do not create heat, they can only remove heat. The spark plug works as a heat exchanger by pulling unwanted thermal energy away from the combustion chamber, and transferring the heat to the engine's cooling system. The heat range is defined as a plug's ability to dissipate heat. The rate of heat transfer is determined by: The insulator nose length Gas volume around the insulator nose The materials/construction of the center electrode and porcelain insulator A spark plug's heat range has no relationship to the actual voltage transferred though the spark plug. Rather, the heat range is a measure of the spark plug's ability to remove heat from the combustion chamber. The heat range measurement is determined by several factors; the length of the ceramic center insulator nose and its' ability to absorb and transfer combustion heat, the material composition of the insulator and center electrode material. Higher octane fuel reduces pre-ignition (and associated detonation) as will improved charge cooling and or lower boost pressures. Link to comment Share on other sites More sharing options...
Ian C Posted February 18, 2005 Share Posted February 18, 2005 I never knew the stockers were at 1.1mm. Never had a stock Supra Going one grade colder on BPU is a good insurance policy as it's not really going to affect the cold start or fouling. My MkIII deffo liked a colder grade plug after I would the boost up, as it was stuttering and it heat heat tracking marks on the plugs From experience the MkIV ignition system is VERY powerful and it needs no boosting when pushing 600+bhp. It'll run near 500bhp on 5v -Ian Link to comment Share on other sites More sharing options...
Tom Posted February 19, 2005 Author Share Posted February 19, 2005 Still trying to narrow things down, today 80mph in 6th, drop to 4th @ 4kish then 0.3 bar till 5.5k then second turbo up to 0.8! Damn annoying! Link to comment Share on other sites More sharing options...
Recommended Posts
Please sign in to comment
You will be able to leave a comment after signing in
Sign In Now