Detonation on second turbo

[slick]

Hello, sorry in advance for the long post but gona try and answer some obvious questions in the post to begin with

 

I've had 4 dyno runs at Thor each time I progressed with the BPU mods, since having the car.

The 1st run was with everything stock apart from boost up via controller. The 2nd and 3rd times was 2nd decat with 1st cat still in.

The last time (4th) it was run was the addition of a Chris Wilson SMIC and 1st decat pipe (fully decatted).

 

Now at 1.2bar Nod said he could hear a 'little det' on the last lot of runs definately since the exhaust/decat.

I went for the CW SMIC as mine looked in a poor state so thought that might not be helping, but no after that was fitted along with the 1st decat pipe Nod @ Thor still said the same.

I had a chat with Chris about it and he was suprised a UK spec would be getting any det at all unless the fuel pump was 'tired' so now I've gone and replaced that with a brand new OE UK toyota pump.

 

The AFR's have varied as the mods have been done, but at the leanest under full (1.2 bar) boost they've never exceeded 12.5 so doesn't sppear to be a fuel issue as such.

 

No idea of EGT temps as not got a gauge.

The car has IK24's fitted 6months ago.

 

Bear in mind at this stage I'd never heard anything dodgy myself, I was just going on what the Thor chaps had said. I decided to try some BP Ultimate in case I was getting iffy Optimax or something crazy.

 

So I put some BP Ultimate in the other day and kept the boost on standard since, today I took it out for a spin and put it to my setting for 1.2bar and pulled away from an almost standstill.

 

As it was boosting on No2 straight away we could clearly hear 'det' (the first time I've heard it myself so far) and it was unmissable so I backed off straight away.

The peak on the controller read 1.15 so it hadn't completely hit 1.2 with me backing straight off.

So 100% posistively audible det on BP Ultimate, so I'm assuming that on Optimax its only detting a little so hence why only Nod has heard it with his head to the engine under boost.

 

 

Did the diagnostic error code check tonight. Just the one stored since I last reset the ECU which was when I fitted the fuel pump last month.... number 35 which according to the MKIV.com list is either the Turbo Pressure Sensor Circuit or Barometric Pressure Sensor Circuit with a ? mark as if they are unsure on the latter.

 

The only thing I can think of with the TPS is that the Greddy BCC intercepts this wire at the ECU doesn't it, how far fetched would trying to blame the BCC be at this stage? Could a dicky one cause such issues even or is it normal to get this error code with one fitted?

 

 

Now if you've read that lot you need a medal, if you've got a possible solution I will give you more than a medal!

 

Cheers for your patience

[Ian C]

Well, if the MAP sensor is faulty (be it sensor or circuit) then you would get a code 35. On a j-spec, the ECU wouldn't know how much air was going into the engine so it couldn't fuel properly for it... It should apparently light the check engine light when this fault is detected though - although the lookup table for these things has been wrong before. I'd have thought it would light the light though. However, you have a UK spec, and that has a MAF sensor, christ knows what the error code for that is as I've only got the J-Spec table...

 

Anyway, it should require much leaner AFRs than 12.5:1 to det A new CW SMIC should intercooler very well, so intake temps should be low enough, the only other things are crap fuel - you've got Optimax or BP Ultimate (interesting to note you got much less det on Optimax...), or too much ignition advance. Which you can't control... I'd suggest an ECU reset in case it's wound on the ignition advance too much even though I always think an ECU reset is a sign of not knowing the answer

 

Maybe the plugs are hot-spotting in the combustion chamber and causing preignition..? Odd one this. Does it run OK on stock boost levels?

 

-Ian

[slick]

Cheers Ian,

 

Re fuel: Over the months that this has been happening (only running 1.2 for the dyno due to this issue) I've had Optimax from 2 different stations up here and 1 lot from one near Thor, so dodgy batches seem unlikely although with only confirming det on the dyno its hard to be sure inbetween.

 

Thor guys never mentioned hearing anything on stock boost no, thank goodness.

 

I'm going to check the BCC connections and the setup on the adjustment voltage just to make sure thats sound with the TPS being mentioned as an error code and the BCC is wired into this circuit so could be related. Could a faulty BCC or loose connection on this cause det to happen in any way?

I might get some NGK's with them being cheap enough to swap out myself and see if it helps, but ofcourse that will need a dyno run as I havn't heard it on Optimax myself yet

 

 

The ECU has been reset at least three times since I first had the det issue brought to my attention, last time being when I did the pump last month.

 

I've not had it on the dyno since doing the pump, but surely the episode the other day with the BP Ultimate shows that its still not happy as I shouldn't be getting det on that regardless. So its more than likely still gona be detting on Optimax should I run it at 1.2 again, I just wouldn't hear it still.

 

Thanks.

[JohnA]

...The AFR's have varied as the mods have been done, but at the leanest under full (1.2 bar) boost they've never exceeded 12.5 so doesn't sppear to be a fuel issue as such..

12.5, I wish mine were like that, they're in the frikin 9s and 10s (also UK spec, but not red )

 

Shame you can't get Tesco 99RON fuel up there, it kicks ass (I would use 97RON-labelled fuel very reluctantly now )

 

Better play it safe and restrict boost to 1 bar until you find out where you stand, but also verify that what you think is detonation really is (find a RR with det cans)

[paul mac]

i used to get a bit of det at the change over point to the second turbo on my j-spec it lasted for about 2 seconds then the ecu sorted it as the revs climbed, however getting prolonged det at the top end is very bad and your in engine blowing up country, sorry cant offer any advice on your problem, good luck

[slick]

Cheers Paul, I guess going single solved yours then lol

 

 

Another update anyway:

 

This evening I redid the BCC connections with new crimps (didn't fancy soldering in the footwell and burning the carpet or something) to rule that bit out, the earth was the only one that I thought didn't look to clever so made sure that was sound. Recalibrated the BCC too as last time when I fitted it I set it to 4.29v which I thought may be too close to 4.3v, so now its at 4.1x volts instead just in case.

 

After I'd done that I removed the reset fuses for 5mins or so and then popped them back in and did the diagnostic thing again (not started the engine as of yet) and it was still showing 35 (which as previously said I think is the Turbo Pressure sensor) So doesn't seem to have been a connection issue on the BBC side.

 

Went for a run and I pretty sure its no different though, listened intently as I hit No2 turbo at 1.1bar and I'm pretty sure could make out a couple of 'tings' although nowhere as bad as when I had the BP fuel in.

So I'm still none the wiser really but at least I know the BCC is fine connections wise.

 

 

Could a faulty Turbo Pressure Sensor cause these symptoms does anyone know?

[paul mac]

Cheers Paul, I guess going single solved yours then lol

sorry mate i did'nt want to mention that, you say there was a slight bit of det, after owning 2 strokes many moons ago and seizing a couple the dredded noise became very familiar, now i'me going to be a bit contraversial here, when you hit the point where it does it are you at max revs and is the det constant or does it pass, all the stuff i have read on det generally regard a bit through the rev range as not being to serious it is prolonged det at high revs that will do the damage, if it is constant might it be worth looking at your knock sensors as modern engine ecu's push the advance till they get slight det then retard, i dont know if they bring up a fault code ! just a thought

[slick]

Not max revs no, on Optimax at the min it will give slight det at 1.1/1.2bar at around 4000rpm ish maybe a little later but only momentary. On BP ultimate it lasted a lot longer and certainly not something I want to repeat for test purposes!

The knock sensors seem to have a code assigned to them, but the only code I'm getting is this 35 that no one seems to know much about

 

Cheers for the interest

[Ian C]

Not max revs no, on Optimax at the min it will give slight det at 1.1/1.2bar at around 4000rpm ish maybe a little later but only momentary. On BP ultimate it lasted a lot longer and certainly not something I want to repeat for test purposes!

The knock sensors seem to have a code assigned to them, but the only code I'm getting is this 35 that no one seems to know much about

 

Cheers for the interest

 

Hmm - how do you get 1.2bar at 4000rpm on a sequential setup? Are you sure it's 4000rpm? Could be a bad boost spike if it is.

 

Also, your BCC should be set to 4.4v, which equals 0.98bar boost. The closer you can set it to 1bar (without reaching it) the better as the stock ECU will fuel closer to the boost you are running. 4.1v is 0.8bar, probably not ideal running 0.8bar of fuel for 1.2bar of boost...

 

-Ian

[Ian C]

Bugger bugger bugger I keep forgetting it's a UK spec car with a MAF. Discount what I said in the second paragraph. You know, you can stop fuel cut on a MAF based car by taking the hose off the MAP sensor and blocking it. A lot cheaper than a BCC and no wiring problems to potentially cause error 35

 

-Ian

[slick]

Hmm - how do you get 1.2bar at 4000rpm on a sequential setup? Are you sure it's 4000rpm? Could be a bad boost spike if it is.

 

I will double check next time I'm out but I'm pretty sure it makes 1.2 @ 4k ish. Just checked my Thor boost graphs and they show 1.2 at 4k since removing both cats, with the cats in it didn't make that boost till 4500 rpm.

 

Your second set of comments had me double checking the BCC guide hehe, till I saw your reply correcting it

 

Ian do you have a theory on the code 35 TPS error, now that I seem to have ruled out dodgy connections and calibration of the unit?

[Ian C]

 

Ian do you have a theory on the code 35 TPS error, now that I seem to have ruled out dodgy connections and calibration of the unit?

 

I haven't got a theory but I know what I'd do - take the BCC out and resolder the wires up and make sure it's a good job, then see if you get the error again (disconnecting the ECU will clear the old error quite nicely). It's wired into the MAP sensor (pin 62, right?) and the MAP sensor is flagging errors up, ergo it's the no1 suspect in my book.

 

Soldering in the footwell is an interesting job Pray you never have to do an RLTC install, the ABS ECU is worse to get at

 

-Ian

[paul mac]

Not max revs no, on Optimax at the min it will give slight det at 1.1/1.2bar at around 4000rpm ish maybe a little later but only momentary. On BP ultimate it lasted a lot longer and certainly not something I want to repeat for test purposes!

The knock sensors seem to have a code assigned to them, but the only code I'm getting is this 35 that no one seems to know much about

 

Cheers for the interest

slick this is EXACTLY what mine used to do at 4000 rpm on the second turbo change over point it is a fairly well known phenomenom, on one of the other forums (NZ i think) they talk about doing the 12v mod to the fuel pump as a cure, i tried it on mine and it made no difference i also fitted FMIC, walbro, new fuel filter, fluidyne, colder plugs, octane booster, optimax etc and it still allways did it to a lesser degree, it ran like that for 3 years with what seems no detrement

[JohnA]

....You know, you can stop fuel cut on a MAF based car by taking the hose off the MAP sensor and blocking it. A lot cheaper than a BCC and no wiring problems to potentially cause error 35

 

-Ian

say again?

 

Are we talking about reaching to the map sensor (on the inlet manifold side) and blocking it off?

 

What's the point of Toyota fitting the sensor if it is totally redundant then? (genuine question!)

 

Anybody done datalogging to see if fuelling/ignition/whatever are adversely affected?

[slick]

take the BCC out and resolder the wires up and make sure it's a good job, then see if you get the error again

 

I knew deep down that was coming really, I was just trying to ignore the voice inside telling me thats what I needed to do (hey we all get voices... right? )

 

Looks like that will be the only way of ruling it out 100%.

Does anyone think that the error code on the TPS circuit which includes the BCC could be related to my Det issue, or are these likely to be completely unrelated?

 

Oh and cheers Paul, you've filled me with hope No seriously, thanks for sharing the pain... just hope I solve this without going single (yet)

[Ian C]

I'd say you should fix this problem *before* going single anyway, what if you still get a lean spot at 4krpm, you'll never know if it was an artefact of the single conversion or some inherent problem that is now even more difficult to find

 

You can probe the TPS wire after the BCC to make sure the ECU is still getting a voltage from the throttle position sensor. Although removing the BCC will also stop it potentially intefering anyway. Are you experiencing problems with the throttle then? I've only read about the MAP sensor so far...

 

-Ian

[slick]

Good point Ian, theres enough to worry about with mapping etc than introducing an unknown issue on top... besides I think turbo swapping is a fair way off yet in my case.

 

Ian, I'm a little confused with what your saying about the TPS. I took the TPS to be the Turbo Pressure Sensor not Throttle Position. As in:

 

As the turbo pressure sensor (TPS) on the TT Supra sees increase boost, it sends an increased voltage (V) on to the ECU. When typical stock boost level is exceeded, the higher TPS V signal causes the ECU to invoke Fuel Cut; this prohibits excess boost. The BCC is simply placed in the middle of this wire from the TPS to the ECU.

 

Is the above information from mkiv.com wrong? Code 35 seems to relate to the Turbo Pressure Sensor too which ties in with the mkiv.com description, so if it is wrong its annoying to say the least.

[Ian C]

Ahhhh, I did wonder what the TPS had to do with it

 

Anyway - TPS = Throttle Position Sensor. Over here, anyway The pressure sensor is the MAP sensor = Manifold Absolute Pressure.

 

The MAP sensor is on Pin 62 of the ECU and is what the BCC will be wired into. Forget about the TPS

 

-Ian

[slick]

Now it becomes clearer

 

Must be just what the yanks call it then

 

Is there a simple way of testing the sensor itself to check its doing its job? I'm thinking ahead in case ruling the BCC still produces this error code....

[Ian C]

Well, you could switch the ignition on, probe the MAP wire, and blow into a hose connected to the MAP sensor, see if it registers a voltage

 

Thing is, I'm unconvinced it's affecting anything other than fuel cut, so you'd be better off concentfrating on the det issue...

 

-Ian

[JohnA]

The ECU needs to know the exact boost pressure of the intake, so it can pulse the exh bypass and the wastegate valves.

 

(I explain in great detail the workings of the sequential on my site)

[slick]

Reset the ECU again tonight to be sure, disconnected the battery for 15mins this time and its cleared the error code (just a regular flash from the light now). Obviously didn't leave the fuses out long enough the other day, I thought it only took a few mins.

So one down, one to go

 

Found this interesting on Supraforums (theres loads on the topic, but this one sums it up)

http://www.supraforums.com/forum/showthread.php?p=3066883#post3066883

 

Over the water they seem to know of a common problem with the OBD1 ECU not being able to always support higher boosts around 1.2bar, seems to be a little hit and miss who it affects but theres several who have had the problem.

Apparently this is how the 12v fuel pump mod was brought about trying to solve it, but it didn't help. The latest development is they say the only way round it is to swap to the later OBD2 ECU (which quite a few have), go aftermarket ECU or an Emanage... safc's and the like don't make a difference they say.

What's the cream of the UK's supra owners make of that issue?

[slick]

Just an update before I finally book it into somewhere like Thor to carry out some deeper investigation.

 

I heard at JAE from a chap who had this same issue on his UK supra, although his AFR's were reading a lot leaner. He eventually sorted this by doing the 12v fuel mod and it sorted it because it turned out to be an issue with the pump ECU not swapping to 12v correctly hence his lean AFR.

I decided (despite reading the 'it does nothing' reports) seeing as it was free and easy to do, that I'd try it too. It didn't help, but at least it ruled it out.

 

Next I've just tried it with a bottle of Millers CVL Turbo octane booster in (500ml bottle about £8) added as recommended to 20L (roughly) of Optimax, which I believe is Millers strongest available booster. I wacked the boost upto 1.2bar and not a sound - at last!

Damn it was good to feel 1.2bar again without the nagging worry. Ok It doesn't really tell me what the problem is exactly, but at least it shows (along with the BP Ultimate test) that I'm not imaganing it and that I do have a slight det problem at over 1bar that is helped by a small increase in Octane.

 

Is it feasible that at this boost level a 12 - 12.5 AFR (as the second turbo comes in) it could be considered too lean? Hence the extra Octane just helping to stop it detting, and that getting some more fuel in at those RPM's (emanage etc) would help the same way?

 

Any input apprieciated as always

[JohnA]

Slick, I've also got a UKSpec and have done several tests on it.

 

In a nutshell:

1. don't assume that UKSpec is the straight equivalent to US-Spec OBDI. I don't think it is.

 

2. Millers is not the strongest OB, out of the commercial offerings NOS is the best one (most expensive too). I've tried it in the past and the difference was feck all (judging from KnockLink activity)

It gave me nice orange spark plugs too.

 

3. You shouldn't be looking at 12-12.5 AFRs as the second turbo kicks in. On the UKSpec it should be a lot richer than that. I have to dial out 25-30% fuel at that stage to bring my AFRs down to that level (which is best for power, but you want to know that you have the headroom for more!)

[slick]

3. You shouldn't be looking at 12-12.5 AFRs as the second turbo kicks in. On the UKSpec it should be a lot richer than that. I have to dial out 25-30% fuel at that stage to bring my AFRs down to that level (which is best for power, but you want to know that you have the headroom for more!)

 

Hmmm this is my thinking too. When the car was completely stock the AFR's didn't go above 11, fair enough thats rich but hey I didn't Det lol Don't get me wrong this is hardly engine destroying within 2seconds det, but still....

Cheers for the input John, think I'm heading towards exploring some ecu options (oh joy).