BPU tech article - for review

[Homer]

Name:

BPU

 

Also known as:

Basic Performance Upgrade

Full decat

 

What is it?

BPU stands for “Basic Performance Upgrade”, a term coined by US firm Suprastore for a basic upgrade package for the TT Supra. BPU is essentially what other marques refer to as "Stage 1” engine modification.

 

The BPU upgrades allow the engine to produce more power by raising the boost pressure the turbos produce.

 

In stock form, the TT produces 0.76bar (11psi), however this can be raised its is generraly acceptd that the stock ceramic Jspec turbos will handle 1.2bar (17.4psi). The Export spec (UK/Euro/US) has steel blades so will, in general, survive at higher boost pressures. 1.4bar (20.3psi) is not unheard of.

 

1.2bar is the "accepted" safe limit with regards to a) detonation, b) actually getting more power, and c) some level of longevity. It is also accepted that you are spinning the cylinder and pulling the trigger each time you use them, but 1.2bar you have one loaded chamber, 1.4bar you've got three

There are limitations with pressures above 1.2bar, the turbos are already outside of their efficiency range and the additional heat generated will raise the intake air temperature considerably – thus negating the effect of increased boost pressure.

 

In both Jspec and export spec, BPU will raise engine power to around 400bhp. Not only will it release more power but it allows much quicker turbo spool-up, which vastly increases drivability.

 

How it works

In stock form, the boost pressure the turbos produce is controlled by back pressure in the exhaust system (I.e. highly restrictive catalytic converters and exhaust system). There are two approaches to BPU dependant on the model of car; as such the next section is split between Jspec and Export spec:

 

 

Fundamentals of BPU

 

Jspec:

To raise boost beyond the stock level the restrictive catalytic converters are removed, thus allowing the turbos to spin faster and produce more boost pressure.

 

There is a down side to this. With both cats removed the turbos will in fact over speed far past their safe limit and reach over 1.6bar (23.2psi). This is due to the small size of the jspec wastegate which cannot cope with the increase in exhaust gasses.

At these pressures the ceramic blades in the turbo can become detached from the shaft and therefore cause catastrophic failure of the turbo.

 

In order to add some restriction back in to the exhaust a restrictor ring is added to the exhaust system. A restrictor ring is simply a metal plate that fits normally between either between the 1st and 2nd decat pipes, or the 2nd decat and cat-back. The centre of the restrictor is drilled out to a smaller diameter than the exhaust itself (normally around 2inches). A properly sized restrictor should bring the maximum boost pressure down to 1.2 bar or less.

 

UK/Euro/US (Export) spec:

To raise boost beyond the stock level the restrictive catalytic converters are removed, thus allowing the turbos to spin faster and produce more boost pressure. Different to the jspec, the export spec has a larger wastegate which can handle the increase in exhaust gasses.

Therefore boost pressure will be maintained at only slightly above stock levels, typically 0.85bar (12.3psi). In order to raise this further it is necessary to install a Boost controller to change the way in which the wastegate opens.

A restrictor ring is not required on the export spec

 

Note: On both models it’s possible to raise the boost with simply adding a Boost controller or Bleed valve; however this is not recommended since the huge resistance of the cats is still in place. This will result in significant extra heat being generated in the manifold and could cause serious engine damage due to raised exhaust gas temperatures.

 

 

Parts required:

 

Obviously all that’s needed to raise the boost pressure is a double decat & restrictor ring (Jspec) or double decat & boost controller (export spec). However, it will not work without further modifications. The following will be required in both models:

 

1) Aftermarket cat-back exhaust

The stock cat back (the pipe after the 2nd decat pipe) is extremely restrictive. In order to allow a good free flowing system this needs to be replaced with an aftermarket system. There are a huge amount of systems available, but any good quality aftermarket system will be suitable for a BPU level of modification.

 

2) Fuel cut defender

The stock ecu will initiate fuel cut when boost pressure reaches 1 bar for a 3 second period. In order to stop this, a device is needed in order to trick the ecu into thinking the boost pressure is lower.

(See quick link for further details)

 

3) Updated fuel pump

The stock fuel pump in the jspecs is not considered suitable for BPU level power, the one in the export spec is higher specification and will be suitable. However as many of these cars are approaching 13 years old it should be standard practice to replace the fuel pump.

The Walbro pump is commonly used, however the Bosch 044 which comes with the export spec is a better specification and has quieter operation (though considerably more costly).

 

4) Colder grade spark plug

With an increase in boost, a ‘colder’ grade plug is required with a closer gap. There are two basic options:

- Iridium IK22 plugs

- NGK BCPR7ES

The iridium’s will last longer (most people get >10k miles) but typically cost £60 a set

The NGK’s need replacing around 3k miles, but cost £14 a set

 

 

Recommended, but non-essential parts:

 

That’s it for the required parts, though there are two items which are highly recommended to ensure you can monitor the health of your engine:

 

1) Boost gauge

A simple electronic or mechanical boost gauge can be mounted in the dash to view the boost pressure. An electronic boost gauge is recommend as most will come with a peak hold or even playback function, thus allowing easier monitoring of maximum pressures

 

2) AFR gauge

Also known as Air/Fuel ratio. This has a wideband O2 sensor mounted in the 2nd decat which measures the air/fuel mixture of the exhaust gases. This is very important to monitor, otherwise you won't know if the air/fuel ratio runs lean under high boost (and therefore result in piston meltdown). Though it won’t allow adjustment, it will warn you that something is not right if it does go lean.

 

3) EGT gauge (optional to AFR gauge)

Also known as Exhaust Gas Temperature. This has a temperature probe fitted into one of the exhaust runners (as close to the cylinder as possible). It performs basically the same function as the AFR gauge by monitoring the condition of the exhaust gases. High temps (sensor mounted post turbo 950degrees is dodgy, >1000degrees is a very bad thing!) will likely result in engine damage due to lean mixture. However there are some cons when comparing this to the afr gauge:

 

- It is much slower to react

- Failure of the temp probe (i.e disintegration) will result in the particles entering the turbos potentially causing failure

- The exhaust runner requires drilling and tapping which can result in swarf entering the manifold before the turbo. This could result in damage to the turbo blades.

 

A safer place to tap the probe is in the exhaust or downpipe after the turbo. It will stop the risk of swarf ending up in the turbo and turbo damage in the event of probe failure. There is a downside - Installing it post-turbo introduces such a big and variable heatsink into the equation it's pretty much useless. People take anything from 100 to 250degC off the aforementioned maximum, meaning that your gauge could read 800degC and mean anything from imminent meltdown to running nicely. No-one has put an EGT sensor before and after the turbo and datalogged the variance so it's 100% guesswork, and that's the last thing you want on the ragged edge.

 

4) Intercooler

An replacement or aftermarket intecooler isn't required, however you need to ensure your current intercooler is in good condition and allows smooth airflow though the core. Many of the stock IC's on older cars are now in very poor condition and suffer from correded fins, if yours is like this it should be replaced prior to going bpu.

[Homer]

Please submit any feedback on the above article, i.e. if anything is wrong or bits I've forgotten (sure there's going to be a few!)

 

It'll be added to the tech section and a quick link for "BPU" once its finalised

 

Thanks

[Pig]

There are however there is limitation in pressures above 1.2bar, the turbos are already outside of their efficiency range and the additional heat generated will raise the intake air temperature considerably – thus negating the effect of increased boost pressure.

 

Needs re-wording

 

Edit: Also i ran 1.4 bar on my UK with Full decat, BL4" exhaust and no bleed valve or boost controller

[jamesmark]

I thought it was IK24's for BPU and IK22 for normal running?

[Homer]

I thought it was IK24's for BPU and IK22 for normal running?

 

Its IK20 for stock, IK22 for Bpu, IK24 for single. Alex wrote a detailed tech article on this. Good point though, I'll add a quick link for that in it.

[Homer]

There are however there is limitation in pressures above 1.2bar, the turbos are already outside of their efficiency range and the additional heat generated will raise the intake air temperature considerably – thus negating the effect of increased boost pressure.

 

Needs re-wording

 

 

Oh, you're right. Proof read this a couple of times and still missed it!

 

Edit: Also i ran 1.4 bar on my UK with Full decat, BL4" exhaust and no bleed valve or boost controller

 

Then you had a problem with one or more actuators, pipework or the wastegate itself! A properly working UK spec will not be able to reach those pressures without something stopping the wasteage from opening.

[Pig]

Then you had a problem with one or more actuators, pipework or the wastegate itself! A properly working UK spec will not be able to reach those pressures without something stopping the wasteage from opening.

 

Well that pissed on my bonfire

[Mas]

excellent mate, good work there, you mentioned the AFR sensor, may I sugest the EGT gauge as its usually cheaper than those kits i.e AFR wideband ... although I know AFR gives much more accurate figures than EGT.

Hope Im not wrong again

[Homer]

Well that pissed on my bonfire

 

lol, sorry forgot to say thanks for the input

 

Anyway, its not like it matters now

[Homer]

excellent mate, good work there, you mentioned the AFR sensor, may I sugest the EGT gauge as its usually cheaper than those kits i.e AFR wideband ... although I know AFR gives much more accurate figures than EGT.

Hope Im not wrong again

 

Thanks mate. The reason I didn't mention EGT is because its an inferior way of measuring engine conditions than an AFR gauge. Its also more expensive when you look at the costs of drilling and tapping a manifold runner (also its risky doing that because swarf can get into the runner pre-turbo).

 

But you're right that it should be mentioned in the aritcle if only for the reasons above

[jamesmark]

So could in recent threads by me the cause of my problems be i am using ik24's for bpu.

 

Please feel free to delete this post to keep on topic as tried a search before i posted but could not find anything.

[Mas]

So could in recent threads by me the cause of my problems be i am using ik24's for bpu.

 

Please feel free to delete this post to keep on topic as tried a search before i posted but could not find anything.

 

Name:

 

- NGK BCPR7ES

The NGK’s need replacing around 3k miles, but cost £14 a set

 

 

.

 

NGK is what Im using and as Homer said it cost £14 and so far every thing excellent

 

PLUS: thanks Homer, I totaly agree with what you just said about the AFR v EGT.

[Homer]

So could in recent threads by me the cause of my problems be i am using ik24's for bpu.

 

Please feel free to delete this post to keep on topic as tried a search before i posted but could not find anything.

 

Thats highly unlikely, colder plugs in a BPU car will (in my experience) only result in a couple of extra cranks to fire up. It won't cause any problems as such.

[Pabs]

again, delete this to tidy up the thread, but i'd just like to say it's excellent for newbies like me, it really helps to explain and clear things up And keep all answers in one place! Good stuff

[jamesmark]

Cheers Homer.

[Tricky-Ricky]

I have always used 950 C EGT as the limit for a pre turbo temp 8-850c after turbo.

[Homer]

I have always used 950 C EGT as the limit for a pre turbo temp 8-850c after turbo.

 

Thanks, I'll have a search. The 850 figure was from memory. Perhaps I'm getting pre/post turbo mixed up...

 

Anyone else have opinions on these figures?

[Pixelfill]

Homer, Alex's spark plug faq lists IK24s as suitable option for BPU (up to 1.3bar) and it also suggests that you *could* leave the spark plug change for 30000 miles, if using iridiums.

 

I wouldn't feel comfortable leaving them that long myself, but it's significantly longer than the 8000 you have listed in the faq.

 

MIke

[Jake]

BPU is essentially what other marquees refer to as "Stage 1” engine modification.

D,

Marquees are large tents.

[Homer]

D,

Marquees are large tents.

 

 

Oops, damn my spellchecking

[Jake]

Nice work Darryl mate.

 

 

I noticed a couple of typos:

"In stock form, the TT produces a 0.76bar (11psi),"

and

"This is due the small size of the jspec wastegate"

 

 

 

Maybe doesn't read right?:

"This is very important to monitor to ensure"

 

"Also known as Exhaust Gas Temperature. This has a temperature probe fitted into one of the exhaust runners" - might be worth saying that you can put the probe after the turbos and explain the Pros and Cons of each position.

[Homer]

Many thanks Jake, it's updated

 

Will have to read it again tomorrow when I'm not on the 2nd bottle of Pinot Grigio

[TrickTT]

.

 

 

In order to add some restriction back in to the exhaust a restrictor ring is added to the exhaust system. A restrictor ring is simply a metal plate that fits normally between the 1st and 2nd decat pipes, the centre of which is drilled out to a smaller diameter than the exhaust itself (normally around 2inches). A properly sized restrictor should bring the maximum boost pressure down to 1.2 bar or less.

 

Chris Wilson advises that the restrictor ring is fitted between the second decat and the exhaust.

[Thorin]

Chris Wilson advises that the restrictor ring is fitted between the second decat and the exhaust.

 

I don't believe it really matters... but it's a bit easier to access there.

[Jake]

Chris Wilson advises that the restrictor ring is fitted between the second decat and the exhaust.

 

http://www.mkivsupra.net/vbb/showthread.php?p=149110