BPU Boost Controllers

[Fulcrum2000]

If you want the feeling of parallel turbos, set it up as TTC (guides on here for that). You still only need one boost controller.

 

Hi

 

No I still want sequential rather than paralell but in my opinion the Supras 'feel nicest' when in stock but the BPU is a good safe level of power and I wanted the best of both worlds so for the sake of stumping up for another BC to make it perfectly set up for this was a great idea I frankly nicked off Scooter on here! I dont know if its an age thing but I always found the judder between two turbos at BPU to be unpleasant. I have driven big singles and its the same feeling for me on those too, great power but not smooth power which for me is important and in stock I feel the Supra has the smoothest power delivery of any car I've ever owned (I've had nearly 50 by the way!) so if I could emulate that but in the 400s for HP that would be about the most perfect option I thought. If anyone wants to know how it turns out I can keep them informed I hope to have it all keyed in in the next few days. After that its finishing off the active suspension project then I think it will all be hunting for cosmetic items to bring my old girl up to spec and a respray.

 

I appreciate I've probably annoyed a few people on here with my ignorance and also made some choices which more capable people feel are wrong but if you knew my back story with this car you would understand why I have done what I did to make this car finally BPU in this way. I've owned the car for just under 3 and a half years and due to unreliability (including a full rebuild and many thousands of pounds worth of other faults, full restoration underneath etc etc etc) I have managed to drive it for less than 2000 miles in this time. Enough was enough and it was time to make some choices to bring this car back to life even if it meant losing a bit more money on ditching the HKS VI etc and I just want to thank everyone for putting up with me. Now I just need to find someone with internal panels and plastics to replace all the faulty ones of those I have in my boot, that will be interesting. I havent had the rear suspension plastic covers in since I bought the car as they're so broken!

[Fulcrum2000]

I think he's getting there just using the phrase "boost controller" might be confusing us......

 

Pictures would help, but I think he has the little bleed setup to increase the first turbo's boost pressure, which does smooth the transition at bpu and then a second one controlling overall boost, that in mine is simply the restrictor ring, which could be called a boost controller too!?

 

BPU with 0.7bar and then 1.2 bar creates a big 'hit' but sub 3500 rpm it can feel a bit flat, 0.85 and 1.15bar acts like the stock sequential system on steroids, that's my experience at least. I've not touched the little bleed valve T piece or restrictor ring in years now.

 

What he said.

[Mike2JZ]

What he said.

 

Ok let's try this one more time. Last time I respond I promise.

 

First let's define a boost controller. A boost controller is a device that can creative a positive gain in manifold pressure by manipulating air pressure delivered to a turbo wastegate actuator.

 

A restrictor ring is not a boost controller. A restrictor ring increases exhaust back pressure, which will limit how much a turbo can flow. Imagine blowing through a small straw.

 

Read what he said again.

 

He isn't suggesting you use two boost controllers. He is suggesting that you use 1 boost controller. A manual bleed valve installed on the the wastegate actuator, creating enough of a leak that the first turbo will spool to 0.8 bar, then relying on the restrictor ring to keep his boost under 1.2 when his second turbo comes on. If he did not have the restrictor ring on the car, the second turbo will overboost quite a lot.

 

The amount of "bleed" or duty cycle required from a manual or electronic boost controller will change between first and second turbo. Whilst operating on the first turbo you will require signifcantly more bleed to achieve a higher boost level than when you are on song with both turbos. You need more on the first turbo as the first turbo has all 6 cylinders pumping into it and has quite a restrictive exhaust setup to fight against, whilst there is more breathing room when second turbo is active hence needing less duty.

 

Most electronics boost controllers aren't smart enough to make a distinction between first and second turbo operation and cannot vary their output to give you lots of boost on first and second turbo. Even scooter's example is a compromise, he chose to have more boost on the first turbo, then rely's on a restrictor ring to keep the system from overboosting on the second. As far as I'm aware the only electronics boost controller than can vary its output based on RPM & Speed is the HKS EV6 and EV7. The boost controller you just removed...

 

When going BPU the transition from 1st to 2nd turbo feels more pronounced as you are asking the second turbo to nearly double what it does from the factory. Furthermore, the factory system does not prespool the second turbo to a sufficient amount to mask the transition. The only way to get the transition to actually go away is to increase the second turbo's prespool (though there is a limit to this), or delay the activation of the IACV VSV, delaying when the second turbo's intake stream joins the rest of the air charge. Just increasing boost to the first turbo is not a solution, it might just feel a bit better to the uninitiated.

 

If you click the link in my signature, you can read about me prattling on about controlling the sequential system using standalone ECU's, and there you can see how I can get 1-1.1 bar of boost on the first turbo, followed by 1.2 and beyond on second. It has some information that you may like reading.

 

So I see what you are trying to do and what you are trying to achieve. Unlike most friendly local mechanics, I literally do this kind of setup stuff specifically on Supra's day in day out for a living. So I can tell you with confidence that you are going about this completely backwards.

 

Anyway, have fun.

[Burna]

Ok let's try this one more time. Last time I respond I promise.

 

First let's define a boost controller. A boost controller is a device that can creative a positive gain in manifold pressure by manipulating air pressure delivered to a turbo wastegate actuator.

 

A restrictor ring is not a boost controller. A restrictor ring increases exhaust back pressure, which will limit how much a turbo can flow. Imagine blowing through a small straw.

 

Read what he said again.

 

He isn't suggesting you use two boost controllers. He is suggesting that you use 1 boost controller. A manual bleed valve installed on the the wastegate actuator, creating enough of a leak that the first turbo will spool to 0.8 bar, then relying on the restrictor ring to keep his boost under 1.2 when his second turbo comes on. If he did not have the restrictor ring on the car, the second turbo will overboost quite a lot.

 

The amount of "bleed" or duty cycle required from a manual or electronic boost controller will change between first and second turbo. Whilst operating on the first turbo you will require signifcantly more bleed to achieve a higher boost level than when you are on song with both turbos. You need more on the first turbo as the first turbo has all 6 cylinders pumping into it and has quite a restrictive exhaust setup to fight against, whilst there is more breathing room when second turbo is active hence needing less duty.

 

Most electronics boost controllers aren't smart enough to make a distinction between first and second turbo operation and cannot vary their output to give you lots of boost on first and second turbo. Even scooter's example is a compromise, he chose to have more boost on the first turbo, then rely's on a restrictor ring to keep the system from overboosting on the second. As far as I'm aware the only electronics boost controller than can vary its output based on RPM & Speed is the HKS EV6 and EV7. The boost controller you just removed...

 

When going BPU the transition from 1st to 2nd turbo feels more pronounced as you are asking the second turbo to nearly double what it does from the factory. Furthermore, the factory system does not prespool the second turbo to a sufficient amount to mask the transition. The only way to get the transition to actually go away is to increase the second turbo's prespool (though there is a limit to this), or delay the activation of the IACV VSV, delaying when the second turbo's intake stream joins the rest of the air charge. Just increasing boost to the first turbo is not a solution, it might just feel a bit better to the uninitiated.

 

If you click the link in my signature, you can read about me prattling on about controlling the sequential system using standalone ECU's, and there you can see how I can get 1-1.1 bar of boost on the first turbo, followed by 1.2 and beyond on second. It has some information that you may like reading.

 

So I see what you are trying to do and what you are trying to achieve. Unlike most friendly local mechanics, I literally do this kind of setup stuff specifically on Supra's day in day out for a living. So I can tell you with confidence that you are going about this completely backwards.

 

Anyway, have fun.

 

Excellent post!

[Scooter]

I agree a very clear post, can I just ask something re the bit below

 

 

When going BPU the transition from 1st to 2nd turbo feels more pronounced as you are asking the second turbo to nearly double what it does from the factory. Furthermore, the factory system does not prespool the second turbo to a sufficient amount to mask the transition. The only way to get the transition to actually go away is to increase the second turbo's prespool (though there is a limit to this), or delay the activation of the IACV VSV, delaying when the second turbo's intake stream joins the rest of the air charge. Just increasing boost to the first turbo is not a solution, it might just feel a bit better to the uninitiated.

 

 

 

....I know my setup uses very basic items, but my understanding was that by having a higher boost pressure on the first turbo when the the prespool of number 2 happens it will also be 'more' ie more prespool than stock and so does smooth out the transition.

 

I get a surge on turbo 2 but not a crazy increase, I really like the way it drives but am always interested in info on the safety or what it is/isn't doing compared to normal. I spose thinking about it I still feel the transition and brief power drop (I'm not trying to eliminate it) but set up like this it definitely has a less of a power/torque leap between say 3,000 and 4,500rpm than a 0.7bar/1.2 bar car does?

 

In the old days, it was decat and cat back........with restrictor ring to limit boost, which is what I have just with the 1st turbo t piece added to increase that a bit, IMO it's a fit once and forget setup, and with a boost gauge with a limit alarm a pretty safe one?

[Mike2JZ]

I agree a very clear post, can I just ask something re the bit below

 

 

 

 

....I know my setup uses very basic items, but my understanding was that by having a higher boost pressure on the first turbo when the the prespool of number 2 happens it will also be 'more' ie more prespool than stock and so does smooth out the transition.

 

I get a surge on turbo 2 but not a crazy increase, I really like the way it drives but am always interested in info on the safety or what it is/isn't doing compared to normal. I spose thinking about it I still feel the transition and brief power drop (I'm not trying to eliminate it) but set up like this it definitely has a less of a power/torque leap between say 3,000 and 4,500rpm than a 0.7bar/1.2 bar car does?

 

In the old days, it was decat and cat back........with restrictor ring to limit boost, which is what I have just with the 1st turbo t piece added to increase that a bit, IMO it's a fit once and forget setup, and with a boost gauge with a limit alarm a pretty safe one?

 

Using basic items is not a bad thing, some of the quicker BPU cars I've ever seen don't even use a boost controller, but the choice of parts on the exhaust side is just right so get the boost in the sweet zone without the risk of severe overboost. I would agree the way you have it setup is pretty safe and no issue continuing like it is.

 

Your statement about higher boost on #1 will help the prespool of #2 is correct to a small degree. The prespool of #2 is mainly controlled by the EGBV (Bypass Valve), and once the valve is open there is a pressure differential + some exhaust gas which helps #2 come spin up.

 

By having more exhaust flow you will help the #2 come on a bit quicker. The issue is that the stock ecu turns the EGBV on quite late, basically just before the transition. So the time in which the prespool is allowed the happen is quite narrow.

 

Even if your #2 turbo spins a bit quicker when EGBV is open, there still isn't a large enough time for the #2 turbo to spool enough for there to be no dip in boost when the intake & exhaust gases are allowed to join during transition, especially if you are trying to hit 1.2 bar. The measureable difference that I've found is quite small.

 

Interestingly when I take control of the solenoids directly using a standalone, I usually opt to opening the EGBV valve really early, like 2000rpm. Doing this, actually allows me to produce more boost on the first turbo (usually max 1 bar) as there is less exhaust restriction with the valve open, wheras normally you are limited to around 0.7-0.8 bar.

 

Whilst having that benefit, the second turbo also gets pre spooled to it's absolute maximum potential (usually 0.5-0.7 bar). This figure makes sense as the stock turbo system is designed to run around 0.7 on the second turbo, so the pre spool valve sizing within the exhaust housing allows for about that much boost to be built, adding to why you dont really feel much of a transition on a completely stock car. I doubt I'll ever get round to it but it would be a good experiment to see if porting the EBV valve and some other parts of the sequential system would allow for more pre spool to occur, cause then you can have your cake and eat it.

 

If you are not using an electronic boost controller, the rate at which boost is built, especially during the transition will be more progressive than an EBC which will hold the wastegate shut for as long as possible up until it reaches it's target boost. Hence why the "dip" can feel a bit more noticable.

 

There is also something to be said about what FCD is being used. Hard to define what causes the differences, but usually HKS FCD causes a more aggressive transition then a Greddy/CW/SRD FCD. I haven't investigated in to much depth, but must be the way the HKS fudges the MAP signal which has a knock on effect on how the ECU decides when to operate the sequential VSV's.

Edited June 26, 2020 by Mike2JZ (see edit history)

[Scooter]

I get you and thanks for clarifying it's safe, if not exactly optimal!

 

I was happy with stock power for ages so this relatively mild bpu still makes me smile and is I think quite conservative.f

[Homer]

I came here to read about how to setup a boost controller and encountered this discussion. Wow.

Thanks Mike and others for the detailed responses, they were extremely helpful