Feck me! (Unexpected BPU)

[Gaz6002]

ok i think we need an expert to explain whats going on when i see 1.6 as a high reading on the boost controller is this just spiking for split second or are the turbos running that boost.i never knew a blown turbo could destroy your engine. maybe i should get 1.4 high setting lowered

 

If you see 1.6 bar on the boost gauge, that's what happened (unless the gauge is faulty or badly fitted, but that's unusual). Do you mean you have a peak boost setting? If you have, it's likely you made that boost for a short time but impossible to confirm. One thing is for sure, you don't want to do that on stock turbos or injectors.

 

Your 1.4 bar - is that on stock turbos? UK or J spec?

[Scott]

Hey I never said I knew anything!

 

OK, maybe I didn't answer your question, erm...... TBH I thought it was damp air that created more boost and it was just coincidence that it usually happened when it was cold.

 

Nothing should really create more boost as the boost controllers, along with restriction rings etc if required, are generally there to stop that, however I know that it does happen. Too many people over the years have said of spikes in the Winter. I have been one of the lucky ones.

 

I'm thinking it might be component related, the boost controller is too cold to work fast enough.... can't be arsed

Edited January 19, 2010 by Scott (see edit history)

[nigelboyne]

If you see 1.6 bar on the boost gauge, that's what happened (unless the gauge is faulty or badly fitted, but that's unusual). Do you mean you have a peak boost setting? If you have, it's likely you made that boost for a short time but impossible to confirm. One thing is for sure, you don't want to do that on stock turbos or injectors.

 

Your 1.4 bar - is that on stock turbos? UK or J spec?

 

uk turbos. yes it records or stores highest boost which was 1.6. i always taught it was just spiking for a fraction of second

[Gaz6002]

uk turbos. yes it records or stores highest boost which was 1.6. i always taught it was just spiking for a fraction of second

 

It may well be, but a fraction of a second is enough to damage things. 1.4 bar should be OK on UK turbos, but I wouldn't want my car to make any more boost than that...

[nigelboyne]

1.2 is plenty in my opinion but its nice to have another 30 hp ROUGHLY in reserve

[Guigsy]

my car has always been a little wierd. when i baught it (fully decatted uk spec bpu) no RR and no boost controller which i believe is limited by the wastegate somehow to arround 1.3?

 

When i got it it naturaly would boost to about 1 bar. Then i noticed it started boosting to 1.3 all the time. And i believe when i had it rolling roaded it did 1.35 (cold day).

But since it seems to have gone back to 1 or 1.1 bar again.

At suprapod last year i t was struggling to get above 0.8 which was frustrating.

Im asumeing i just need a boost controller wired in to get it boosting back to 1.3 properly and consistantly again. i miss that

 

 

Also when i swapped out and old defi guage for a new one the guage gave me all kinds of funny reading and even worked in reverse untill the controll box seemed to figure out what was going on. So if i pressed my peak button it said 2 bar. untill i reset it

[Soop Dogg]

If my car was suddenly boosting to that level above normal, I'd be checking the hoses on the wastegate vsv. Could be 5 second fix.

[Homer]

my car has always been a little wierd. when i baught it (fully decatted uk spec bpu) no RR and no boost controller which i believe is limited by the wastegate somehow to arround 1.3?

 

When i got it it naturaly would boost to about 1 bar. Then i noticed it started boosting to 1.3 all the time. And i believe when i had it rolling roaded it did 1.35 (cold day).

But since it seems to have gone back to 1 or 1.1 bar again.

At suprapod last year i t was struggling to get above 0.8 which was frustrating.

Im asumeing i just need a boost controller wired in to get it boosting back to 1.3 properly and consistantly again. i miss that

 

 

Also when i swapped out and old defi guage for a new one the guage gave me all kinds of funny reading and even worked in reverse untill the controll box seemed to figure out what was going on. So if i pressed my peak button it said 2 bar. untill i reset it

 

Uk's are a different matter, but the temp difference you mentioned is a normal effect. Doesn't sound like anything was wrong at all, it's exactly how it should work.

 

The 2 bar reading isn't right though, could be a few causes but most likely a duff reading as the stock turbo's can't reach those pressure levels. Drag racing will always see much lower pressure, again due to AIT's.

 

Scott M, I don't have time to give a full explaination, it's not so easy to type out everything in an easily understandable way. Will try tomorrow, time permitting.

[Ian C]

Any idea what to search for to find it? I'm very curious about this. The pressure sensing should remain the same regardless of the temperature. In fact it would be an increase in temperature that would cause more pressure. Colder air means denser air or less volume, not more pressure. If a valve is set to open at 1bar, it will open at 1bar regardless of what temperature it is at. If it is warmer there will be less density of air, if it is cooler there will be more density of air.... thats it though.

 

I think Homer is referring to post #4 on this:

http://www.mkivsupra.net/vbb/showthread.php?t=203838

 

I can't say I've read the whole thread but if this a question about why turbos can overboost in cold weather despite a bells-and-whistles boost controller being in charge, well:

 

The BC measures boost pressure. Cold air being compressed to 1.2bar gives a denser air charge than hot air being compressed to 1.2bar. Denser air = more power, hurrah! We all know that bit

 

More power due to more molecules getting jammed into the cylinders = more exhaust... More exhaust through the turbo = more oomph to spin them.

 

Suddenly the BC is going "eh? What's going on here then?" as the turbos get spun faster than they did on a hot day and the programmed wastegate solenoid duty cycle isn't enough to control the boost any more.

 

Normally this means boost goes up a couple of psi, but with the teeny wastegates on the Supra stock turbos, you can tip over into runaway boost and start hitting silly numbers.

 

To get around this, some boost controllers have a self learning feature which allows them to constantly trim the duty cycle in a feedback loop, by reading the current boost pressure. It works as long as the "self-learning" feature is set up correctly, but you may still record a high peak as it frantically scrabbles to control the situation.

 

-Ian

[Jellybean]

Can I ask a slighly off topic Q : Everybody is running either the IK 22/NGK 7 or the IK 24/NGK 8 Spark plugs for BPU @ 1.2?

 

I was goin to get the IK22/ NGK 7 tomorrow

[T2 MSW]

either of those 2 will be fine. i used to run the heat range 7 plug.

 

http://www.mkivsupra.net/vbb/showthread.php?t=41927

[Jellybean]

either of those 2 will be fine. i used to run the heat range 7 plug.

 

http://www.mkivsupra.net/vbb/showthread.php?t=41927

 

Thanks, seen that article alright but since IK 22/IK24 fall under the up to 1.3 bar just was wondering what they where like in reality (Peoples experiances)

[Guigsy]

Uk's are a different matter, but the temp difference you mentioned is a normal effect. Doesn't sound like anything was wrong at all, it's exactly how it should work.

 

The 2 bar reading isn't right though, could be a few causes but most likely a duff reading as the stock turbo's can't reach those pressure levels. Drag racing will always see much lower pressure, again due to AIT's.

 

Scott M, I don't have time to give a full explaination, it's not so easy to type out everything in an easily understandable way. Will try tomorrow, time permitting.

ok cheers. im sure i had it at 1.3 in the middle of summer though. lol good to know something isnt wrong though. the 2 bar on the boost guage was when the car was sat at idle so i think it was a bit of an electronic thing.

 

i plan on doing some more drag racing. would a boost controller get me back up to 1.3 properly and then something like removing the headlight be any good for the intake temps? I plan on making a little mod to the airbox so i can cut out a hole and then put in a stopper to keep it sealed when the headlight is in and then take the stopper/grommet out when the headlight is out.

[Scott]

I think Homer is referring to post #4 on this:

http://www.mkivsupra.net/vbb/showthread.php?t=203838

 

I can't say I've read the whole thread but if this a question about why turbos can overboost in cold weather despite a bells-and-whistles boost controller being in charge, well:

 

The BC measures boost pressure. Cold air being compressed to 1.2bar gives a denser air charge than hot air being compressed to 1.2bar. Denser air = more power, hurrah! We all know that bit

 

More power due to more molecules getting jammed into the cylinders = more exhaust... More exhaust through the turbo = more oomph to spin them.

 

Suddenly the BC is going "eh? What's going on here then?" as the turbos get spun faster than they did on a hot day and the programmed wastegate solenoid duty cycle isn't enough to control the boost any more.

 

Normally this means boost goes up a couple of psi, but with the teeny wastegates on the Supra stock turbos, you can tip over into runaway boost and start hitting silly numbers.

 

To get around this, some boost controllers have a self learning feature which allows them to constantly trim the duty cycle in a feedback loop, by reading the current boost pressure. It works as long as the "self-learning" feature is set up correctly, but you may still record a high peak as it frantically scrabbles to control the situation.

 

-Ian

 

Ok that makes a bit more sense. I don't understand why an Electronic Boost controller works that way as it would be far better just reading the pressure and adjusting it that way but thats fine.

 

Does that mean that, with regards to control, MBC's are actually superior to EBC's then? I've always had MBC's due to the cost of EBC's but always liked the idea of being able to increase the boost at the touch of a button.... even though I can do it quite comfortably with my right foot. Everyone goes on about how an EBC adjusts the boost a million times a second, it does but only by a %age it would appear. If the initial pressure changes the control is lost.

 

I've never had a winter spike from an MBC or from the restrictor ring I have in now (Runs around 1bar). I have had spikes due to the wastegate sticking a little but thats it.

[Scott]

ok cheers. im sure i had it at 1.3 in the middle of summer though. lol good to know something isnt wrong though. the 2 bar on the boost guage was when the car was sat at idle so i think it was a bit of an electronic thing.

 

i plan on doing some more drag racing. would a boost controller get me back up to 1.3 properly and then something like removing the headlight be any good for the intake temps? I plan on making a little mod to the airbox so i can cut out a hole and then put in a stopper to keep it sealed when the headlight is in and then take the stopper/grommet out when the headlight is out.

 

I would say something was wrong with it when it was running 1.3bar. Due to the UK wastegate being a decent size and being able to flow the boost properly you shouldn't see any more than stock boost without anything in to control it.

 

The fact that you have had 2bar spikes would tell me you might have a sticky wastegate or wastegate actuator.

[T2 MSW]

I would say something was wrong with it when it was running 1.3bar. Due to the UK wastegate being a decent size and being able to flow the boost properly you shouldn't see any more than stock boost without anything in to control it.

 

The fact that you have had 2bar spikes would tell me you might have a sticky wastegate or wastegate actuator.

 

2 bar boost was at idle!! so more likely a reading error than a serious issue. Turbos would have gone long before if they were hitting 2 bar

[Guigsy]

I would say something was wrong with it when it was running 1.3bar. Due to the UK wastegate being a decent size and being able to flow the boost properly you shouldn't see any more than stock boost without anything in to control it.

 

The fact that you have had 2bar spikes would tell me you might have a sticky wastegate or wastegate actuator.

 

the boost guage never spiked to 2 bar as the car was only idleing. i plugged the new guage in after replacing an old one of the same model. and the guage worked in reverse. car never moved or boosted

 

maybe i did have some issue with it while it was boosting to 1.3 then and now its back to being normal i thaught it was the other way arround.

[Terminator]

 

I've said it before, I'll say it again - I can't even imagine what a single is like!

 

 

Its different:d

 

Restrictor rings are can not be made to give a certain max boost figure. They can only be made to give a general ball park figure. The best way to protect against boost spikes and cold weather boost levels is to fit a RR small than you want, try it in cold weather and adjust it in cold weather to the max boost you want your turbo's to see.

 

A boost controller can not clamp boost down to a level lower then system will make on its own.

 

Just before I fitted a RR, my JDM tubbies made over 1.4 bar several times and did not self destruct, they continued to work well for another 8 years, before ditching them for a single.

[jevansio]

Ok that makes a bit more sense. I don't understand why an Electronic Boost controller works that way as it would be far better just reading the pressure and adjusting it that way but thats fine.

 

Does that mean that, with regards to control, MBC's are actually superior to EBC's then? I've always had MBC's due to the cost of EBC's but always liked the idea of being able to increase the boost at the touch of a button.... even though I can do it quite comfortably with my right foot. Everyone goes on about how an EBC adjusts the boost a million times a second, it does but only by a %age it would appear. If the initial pressure changes the control is lost.

 

I've never had a winter spike from an MBC or from the restrictor ring I have in now (Runs around 1bar). I have had spikes due to the wastegate sticking a little but thats it.

Scott, I dunno if this helps but I think you should look at open & closed loop feedbacks.

 

Pretty sure that most aftermraket boost control is open loop. This means that the controller does not have the output of the system (the boost that was created) fed back into itself so it can adjust. It basically means that the controller is setup to operate in a given scenario (a summers day for example), you enter a duty into the controller (the rate at which it opens the solenoid) and it will produce a given boost in those conditions. When the conditions change (cooler temps), the whole system is affected (as Phil says, denser air, gives more power etc), the main point being that changes to the input environment to the system effect the systems output since the controller is doing the same thing.

 

In a closed loop scenario the controller would have the output singal (the boost the turbo had created) fed back into it. That way, it can say "I wanted 14PSI, I only got 13PSI, hence I need to drive the solenoid harder" or "I wanted 14PSI, I got 15PSI, hence I need to drive the solenoid softer".

 

The AEM (& I guess other ECUs) which control boost operate in closed loop as you input a desired boost and the ECU is fed the boost singal, so it can determine if the boost is higher or lower than desired and adjust the solenoid accordingly. This way it doesn't matter if in cold weather it wanted to create more boost, it just wouldn't drive the solenoid as hard.

 

Most 3rd part boost controllers operate in operate in open loop mode (even though some take a boost feed it's just used for display on the controller).

 

Does this make any sense? It doesn't explain "why" cold weather creates more boost (as Phil covered that) but why plug in boost controllers/manual boost controllers/restrictor rings are affected by cold weather (as they aren't a closed loop system).

[T2 MSW]

[Scott]

Scott, I dunno if this helps but I think you should look at open & closed loop feedbacks.

 

Pretty sure that most aftermraket boost control is open loop. This means that the controller does not have the output of the system (the boost that was created) fed back into itself so it can adjust. It basically means that the controller is setup to operate in a given scenario (a summers day for example), you enter a duty into the controller (the rate at which it opens the solenoid) and it will produce a given boost in those conditions. When the conditions change (cooler temps), the whole system is affected (as Phil says, denser air, gives more power etc), the main point being that changes to the input environment to the system effect the systems output since the controller is doing the same thing.

 

In a closed loop scenario the controller would have the output singal (the boost the turbo had created) fed back into it. That way, it can say "I wanted 14PSI, I only got 13PSI, hence I need to drive the solenoid harder" or "I wanted 14PSI, I got 15PSI, hence I need to drive the solenoid softer".

 

The AEM (& I guess other ECUs) which control boost operate in closed loop as you input a desired boost and the ECU is fed the boost singal, so it can determine if the boost is higher or lower than desired and adjust the solenoid accordingly. This way it doesn't matter if in cold weather it wanted to create more boost, it just wouldn't drive the solenoid as hard.

 

Most 3rd part boost controllers operate in operate in open loop mode (even though some take a boost feed it's just used for display on the controller).

 

Does this make any sense? It doesn't explain "why" cold weather creates more boost (as Phil covered that) but why plug in boost controllers/manual boost controllers/restrictor rings are affected by cold weather (as they aren't a closed loop system).

 

Ahhh that explains a lot mate, thanks.

 

I think the key here is actually the restrictor ring and the difference between the intended pressure and the natural pressure produced with it in. In a freely flowing BPU car the boost will spike to 1.6 in most cases. Putting in a restrictor ring obviously solves this issue but the size of the ring is what will determin the "natural" boost created. If someone were to use a 1.2bar restrictor ring and get 1.2bar on their boost gauge then no boost controller would be required due to only being able to up the boost. In the winter the increase in exhaust gas will somewhat overrule the restriction slightly causing the boost to go above 1.2 (often 1.3 or 1.4). This in essence is due to the cold weather and more importantly the colder charge giving more power and spinning the turbo's harder. It would often be better to have a lower restrictor ring in place, the bigger the margin to play with (ie 1.0 ring with the car running at 1.2 gives a margin of 0.2) the better control will be had over the power. If that is the case then it won't make a difference what type of controller you have as they can only lower the pressure, if the natural boost pressure is increasing due to the restrictor ring becoming less effective then you could have a kazoo on there and it won't make a difference.... MBC for the win

 

Just realised i'm writing loads and rambling. I understand it all fully now lol. Thanks.

[TLicense]

There's only 2 things that kind of go against your thinking...

 

The first is that is the downside to fitting a much smaller restrictor ring and then using the boost controller to pull the boost up is that it will generate a whole chunk of heat. Maybe it won't be a problem, but maybe it will... will depend on your set-up.

 

The second is that the bad thing with mechanical boost controllers is that they're very progressive. What I mean by that is if you have a spring and put 1 lb of pressure on it, it'll open up a little. If you put another lb on it'll open up a bit more and so on and so on.

With an EBC you can hold the wastegate shut and open it only when the boost reaches (or approaches) the target. The result is much greater spool response.

[Scott]

There's only 2 things that kind of go against your thinking...

 

The first is that is the downside to fitting a much smaller restrictor ring and then using the boost controller to pull the boost up is that it will generate a whole chunk of heat. Maybe it won't be a problem, but maybe it will... will depend on your set-up.

 

The second is that the bad thing with mechanical boost controllers is that they're very progressive. What I mean by that is if you have a spring and put 1 lb of pressure on it, it'll open up a little. If you put another lb on it'll open up a bit more and so on and so on.

With an EBC you can hold the wastegate shut and open it only when the boost reaches (or approaches) the target. The result is much greater spool response.

 

Does it really go against my thinking though? I wasn't saying what the pro's and cons were, only the understanding of why the boost spikes. I totally agree with what you are saying, I'm going for 1.0bar and hiking it up from there. Hopefully that won't put TOO much back pressure on the system causing heat, while leaving enough headroom for any extra power in the winter

 

As for the 2nd point, surely if the EBC works the way it has been explained then it is progressive too? The solenoid lies about the pressure by x% as it is duty driven? At 1.0bar it tricks the system into thinking it is only at 0.6bar or something around that. This would mean that it would be allowing 0.6bar to the wastegate actuator. As the wastegate actuator actuates at 0.7 or thereabouts it would remain closed. Also, the stock system obviously uses a spring in the actuator (or a vacuum, not sure) so that would mean, if your thinking is correct, the EBC would give a faster spool at the same boost levels? Not heard of that one before. Would be interesting if it was the case though

[Homer]

Does it really go against my thinking though? I wasn't saying what the pro's and cons were, only the understanding of why the boost spikes. I totally agree with what you are saying, I'm going for 1.0bar and hiking it up from there. Hopefully that won't put TOO much back pressure on the system causing heat, while leaving enough headroom for any extra power in the winter

 

1.0 bar restrictor will be fine. It's best to set the restrictor ring size to your boost target during colder weather, if done in the summer you can get overboost when temps drop. Ideally if you want to run 1.2 bar peak it should be set to 1.2 bar during cold weather as this will help cause heat & back presure issues once it gets warmer.

 

As for the 2nd point, surely if the EBC works the way it has been explained then it is progressive too? The solenoid lies about the pressure by x% as it is duty driven? At 1.0bar it tricks the system into thinking it is only at 0.6bar or something around that. This would mean that it would be allowing 0.6bar to the wastegate actuator. As the wastegate actuator actuates at 0.7 or thereabouts it would remain closed. Also, the stock system obviously uses a spring in the actuator (or a vacuum, not sure) so that would mean, if your thinking is correct, the EBC would give a faster spool at the same boost levels? Not heard of that one before. Would be interesting if it was the case though

 

The EBC can work in several ways depending on model. The older ones use duty cycle control which works on a % value, this will result in more fluctuation due to charge density over the more modern boost controlled EBC's. However, as Tony mentions the design of the stock system will mean that wastegate controll deteriates as engine performance (boost AND charge density) increase.

 

The gain control is a really nice feature on modern EBC's, again as Tony mentions this allows the boost to build more quickly (quite considerably so), but has two downsides:

 

1) It can result in boost spikes if set too high due to the wasgate not being able to adjust itself fast enough. More boost, high gain = less control

 

2) Be VERY careful monitoring the AFR and EGT's when adjusting gain, the stock map doesn't compensate enough for the very fast spool you get with high gain on the 2nd turbo. This is the dreaded 'changeover' lean point on stock ECU cars and in my opinion one of the biggest risks when coverting to BPU.

 

Gain also needs to be checked when the temperature drops as the spool time will decrease.

[monsween]

I managed to boost at 1.3 on the way home today. I have a 1.0 bar RR :S