J Spec BPU

[wrenlea]

Please don't groan too much at yet another query re BPU

I really thought I "got" this till tonight when I saw my umpteenth post on the topic.

I have a TT RZ Auto

 

As I understand it I need the following:

1. decat pipes, with a restrictor ring

2. fuel cut defencer,

3. uprated fuel pump, probably a Walbro.

4. NGK Iridium spark plug set.

and lastly proabably a boost guage and maybe a new intercooler

 

HOWEVER, I saw a post tonight where somone has the above AND a boost controller

 

My question is this ...If a boost controller ONLY boosts and does not restrict in any way and a restrictor ring restricts the boost how can a boost controller have any purpose, as surely it cannot restrict the boost and equally it cannot boost beyond the restrictive properties of the ring??

 

I have seen sites saying that a boost controller gives an extra 20HP but does this refer only to UK spec as there is no reference to a ring.

 

Also any recommendations as to a good installer where I could get this done preferably including a service would be appreciated (a sensible distance from West London)

 

Thanks

 

Peter

[Angarak]

My understanding is this....

 

JDM Supra TT's

On a JSpec, when you double decat you generate too much boost due to the wastegate dimensions (There is a difference between UK and JDM wastegates).

 

This is why its recommended to install a Restrictor Ring (RR) on a JDM to limit boost to a max of 1.2 bar.

 

Some decatted JSpec TT's with a RR see 1.2 bar without a Boost Controller (ie: mine), whilst others need a boost controller to see 1.2 bar (ie: they may only make 1.0 bar without a boost controller).

 

Once you have decatted with a RR, go have a blast and see if you get 1.2 bar on WOT. If you do, you dont need to buy a boost controller and can spend your money on something else

 

UK TT Supra's

When you decat on a UK spec, you need a boost controller to see 1.2 bar.

 

 

Im sure someone more techinically minded will come along and correct me if Im wrong.

[Nic]

A restrictor ring causes a restriction in the exhaust, which causes a degree of back pressure to prevent the turbos from overspooling. A restrictor ring doesn't restrict boost as such, but just creates a restriction in the flow of exhaust gasses exiting the exhaust. ie. you could have a smaller diameter restrictor ring fitted which causes the turbos only spool to 1bar and then fit a boost controller to raise the boost to say 1.2bar.

 

A boost controller basically controls the wastegate, in the above example it would control the opening of the wastegate, so that more exhaust gasses go through the turbos and thus more boost is generated.

 

A boost controller gives NO hp increase as such, it just allows control of the wastegate so that the boost pressure can be increased. So in simple terms, a car with restrictor ring limiting boost to 1.2bar, will make the same power as a car with a boost controller raising the boost to 1.2bar.

 

Some boost controllers can increase spool time quite a bit on a BPU Supra, by holding the wastegate closed for longer, thus allowing boost to build up faster. Some of the better boost controller can also map the boost settings (wastegate control) against speed, throttle position, rpms, etc. so that boost can be maximised through each gear and at different speeds. In comparison a restrictor ring is sized to limit boost to a given amount usually in a higher gear (where there is more engine load), which mean it won't make that same max boost under less load in lower gears.

[Nic]

and lastly proabably a boost guage and maybe a new intercoole

 

You must fit a boost gauge, it is vitally important so that you can monitor boost levels, to make sure they do not go too high. I would also recommend fitting an exhaust gas temp gauge, again very important to monitor temp levels to make sure they don't go too high and risk damaging your engine.

 

If you need any help or recommendations, please feel free to pm me with any questions

[merckx]

. you could have a smaller diameter restrictor ring fitted which causes the turbos only spool to 1bar and then fit a boost controller to raise the boost to say 1.2bar.

Yes , definately the way to go if you want to reach 1.2 bar boost throughout the year.

 

You'll find that if you fit a restrictor ring to give you 1.2 bar in the freezing cold of winter , when the weather warms up to the higher temps on a summers day you'll be boosting to maybe just over 1 bar.

 

This is obviously because the density of the air will change as the ambient temp changes.

 

Like Nic says, raise it from 1.0 bar (with a restrictor ring fitted) to 1.2 bar with a boost controller to is the best way to go as it will give you this level of boost irrespective of the ambient temperature.

[letmeshowyou]

or like me have a ring set to about 0.8 bar (that way I can see 0.8 bar when it's raining with the BC turned off)

[wrenlea]

REALLY grateful for these posts, thanks.

I am back on the track I thought I was now and aim to get this done in the next few weeks.

Needless to say I am looking forward to it

[Guest MR 2JAY]

A good way to avoid this boost spiking or overboosting issue is to leave the stock down pipe in place.

 

This is commonly used in Australia with the JDM supras and is very effective. Stock DP into 3" all the way through will give you a good 1-1.1bar without a boost controller.