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The mkiv Supra Owners Club

Double Decat upgrade


flyin_scouseman

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Hi all, I have not long bought a almost standard mkIV J-Spec TT Supra with BPU such as the exhaust and filter :D . I am now looking to upgrade my exhaust system via double/full decat pipe. Can anybody give any advice as to what other parts i need to upgrade such as fuelling etc so that i get the best possible performance from my decat install. Also what are the best "buyers brands" you guys have purchased in the past when undertaking this forementioned upgrade. All advice is extremely welcome ;)

Cheers, Andy.

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LOL I thought air filter and full exhaust replacement were a basic power upgrade :search: maybe i've worded my subject wrong..... if not can you help me out here as im not quite with da lingo..... Do you have to decat your uprated zorst to be BPU? Have you carried out this mod to your system on your car RedM? If so can you give us a bit more info on what you have done. Thanks..... Andy.

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Cheers, I have also read that i may need a boost controller. Any recommendations as i am making a shopping list :D

 

Not if you have a pre VVTI import you wont..

 

Very quickly if I remember:

 

 

Decent Exhaust

Both decat pipes

FCD

Boost gauge

restrictor ring

new fuel pump

fueling check on RR

 

:)

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Thankyou very much Darren you are a bloody star :D Yes my car is a non vvti model and is a 94 reg. I guess it's now just a case of me choosing my own brands then m8 ;) have you carried out these mods and did you come across any problems or setbacks? What is the best FCD to go for matey as i've read there are some dodgy ones out there? Sorry for being so inquisitive but any little snippet of info can/will help me out.

Cheers, Andy. :thumbs:

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Decent Exhaust - What have you got?

Both decat pipes - 2.5 inch or 3 inch up to you.

FCD - TRL

Boost gauge - Cheap and cheerful for now. You do not want to be running over 1.2bar.

restrictor ring - Its a big washer (Not needed on UK or VVTI cars)

new fuel pump - Uprated flow would be good.

fueling check on RR - Just to check its not running lean

 

 

 

Oh yes colder spark plugs aswell. - Cheaper NGKs fine

 

Yes I have all this on mine and more. This is the best gain £ for £ you can do and will transform the car. It gets expensive after this IMHO.

 

HTH :)

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Hi Darren, not too sure what exhaust it is but it's a biggun and sounds sweeeet. As to what diameter decat pipe to get....... Not too sure the difference between the 3" or the 2.5". The one i've got my eye on is on whiffbitz for a sale price of 136 quid or something like that :) The spark plugs? what are the major differences and do they show these details on the traders websites? Cheers for the feedback matey ;) I'll have a look round for fuel pump. Not too sure if they are pricey tho :blink: guess ya get what ya pay for in this game........

Cheers, Andy :thumbs:

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Hi Darren, not too sure what exhaust it is but it's a biggun and sounds sweeeet. As to what diameter decat pipe to get....... Not too sure the difference between the 3" or the 2.5". The one i've got my eye on is on whiffbitz for a sale price of 136 quid or something like that :) The spark plugs? what are the major differences and do they show these details on the traders websites? Cheers for the feedback matey ;) I'll have a look round for fuel pump. Not too sure if they are pricey tho :blink: guess ya get what ya pay for in this game........

Cheers, Andy :thumbs:

All you have to do is ask.... :)

 

go 3" mate, altho 2.5" will be fine, but obviously flow less, your exhaust is 3" --- make sure you get one with a lamba sensor hole in ;).

With spark plugs, if your running over 1bar, its a good idea to buy plugs that will handle running higher boost(called 'colder plugs'), id go with Denso iridium IK24's, (£8each max).

A trl Fcd is Perfect for what you want, as instead've gettin rid of your fuel cut altogether (like the hks does) the thor just up's it, to what you specify (i wouldnt boost above 1.2bar on jspecs) not just because of the blades, but of egt's (exhaust gas temperatures).

 

You dont need a fuel pump IMO and 90 % of guys on here running bpu jspecs dont have better fuel pumps

 

Boost controller.... you'll find alot of jspecs dont have these, as the restrictor ring kinda controls it to a max boost pressure, but if you didnt want to spend the money for a electronic boost controller, such as a apexi, hks, which are £200+, you could stick with a manual boost controller, which are crude, but work, and im sure alot of ppl on here are using them.

 

But, once you have all these, and are looking for higher brake, 400+ then its time for a FMIC, Electronic boost controller, and Uk fuel pump (or walbro), to be on the safe side.

im sure if ive said anything wrong there will be a few people who will take great pride in correcting me :p

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Regarding Spark plugs I have run NGKs that cost about £10 for 10 in my car for 3 years at 1.2/1.3 and have suffered no missfires so you can save a couple of quid safely there without causing any problems..Not that theres anything wrong with Densos they are excellent just more expensive.....

 

Personally I think theres two golden rules to running a BPU Supra.

 

Dont run it ABOVE 1.2 bar (So you should have a boost gauge)

 

Make sure it is not under fuelling at full throttle under full load.

 

Unless you want to buy new turbos or rebuild the engine.

 

all just MHO.

 

Go BPU it transforms the car.... :cool:

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ahh, hello mr Pryde :) how are you sir? Glad to see you today. Cheers for your insight matey and all you guys too. What are the decent brands and best prices around then for a 3" full decat and where can i buy them? I've looked on whiffbitz but a bit pricey and i think they're all 2.5" Cheers once again.........

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Hi fellas, where can i find me a TRL fcd as all i can seem to find are HKS or Greddy brands. Also what are your opinions on the Greddy electronic boost controller are they any good? And how hard are they to fit? :search:

 

LOL whats the fascination with a boost controller? If you decat your car it will boost to god knows what if you dont run a restrictor ring!! Then you want to boost it further?? :rolleyes: :rolleyes:

 

Boost controller UPS the boost. Are you going to run a really really small restrictor ring so that you can then buy a boost controller too??? :eyebrows:

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All you have to do is ask.... :)

 

go 3" mate, altho 2.5" will be fine, but obviously flow less, your exhaust is 3" --- make sure you get one with a lamba sensor hole in ;).

With spark plugs, if your running over 1bar, its a good idea to buy plugs that will handle running higher boost(called 'colder plugs'), id go with Denso iridium IK24's, (£8each max).

A trl Fcd is Perfect for what you want, as instead've gettin rid of your fuel cut altogether (like the hks does) the thor just up's it, to what you specify (i wouldnt boost above 1.2bar on jspecs) not just because of the blades, but of egt's (exhaust gas temperatures).

 

You dont need a fuel pump IMO and 90 % of guys on here running bpu jspecs dont have better fuel pumps

 

Boost controller.... you'll find alot of jspecs dont have these, as the restrictor ring kinda controls it to a max boost pressure, but if you didnt want to spend the money for a electronic boost controller, such as a apexi, hks, which are £200+, you could stick with a manual boost controller, which are crude, but work, and im sure alot of ppl on here are using them.

 

But, once you have all these, and are looking for higher brake, 400+ then its time for a FMIC, Electronic boost controller, and Uk fuel pump (or walbro), to be on the safe side.

im sure if ive said anything wrong there will be a few people who will take great pride in correcting me :p

 

No point in 3" decats on a JDM car. You just encourage more overboost and will need a restrictor ring with an even smaller inner diameter. 2.5" decats are fine scouseman but personally I'd only buy them if the one nearest the engine had a wideband o2 bung on it for accurate fuelling checks.

 

Iridium plugs are an unecessary expense and I personally have seen and read of many failures where the Denso brand are concerned. NGK BKR7E's at £1.50 a plug tops from your local motor factors are the hot ticket here. Gap to 0.9mm :)

 

TRL VFCC (fuel cut defencer) is still considered the best one on here.

 

I'd say fuel pump was pretty damned essential. For the sake of £75 it gives the safety margin and reassurance needed if you buy a Walbro. The JDM car's pump really is pretty marginal for increased boost. I notice you have a UK spec Mr.Pryde so you already have a better pump which is less of a worry.

 

Boost controller is a waste of money on the JDM car (as boost will already be too high with exhaust and decats, and will necessitate fitment of a restrictor ring) until such times as you go single turbo and then need a way of increasing boost.

 

Cheers,

 

Brian.

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No point in 3" decats on a JDM car. You just encourage more overboost and will need a restrictor ring with an even smaller inner diameter. 2.5" decats are fine scouseman but personally I'd only buy them if the one nearest the engine had a wideband o2 bung on it for accurate fuelling checks.

 

Iridium plugs are an unecessary expense and I personally have seen and read of many failures where the Denso brand are concerned. NGK BKR7E's at £1.50 a plug tops from your local motor factors are the hot ticket here. Gap to 0.9mm :)

 

TRL VFCC (fuel cut defencer) is still considered the best one on here.

 

I'd say fuel pump was pretty damned essential. For the sake of £75 it gives the safety margin and reassurance needed if you buy a Walbro. The JDM car's pump really is pretty marginal for increased boost. I notice you have a UK spec Mr.Pryde so you already have a better pump which is less of a worry.

 

Boost controller is a waste of money on the JDM car (as boost will already be too high with exhaust and decats, and will necessitate fitment of a restrictor ring) until such times as you go single turbo and then need a way of increasing boost.

 

Cheers,

 

Brian.

 

Cheers, That's cleared that one up then.... I thought by way of installing a boost controller i could limit the boost for definate as a safe guard(although thats the reason for installing an FCD is), but also have a play in future if i want to up the ponies as i am also going to be installing a better intercooler soon.

I hear that i would have to upgrade the turbos if i wanted to do that as the stock items are only good for 1.1 - 1.2 bar. But if installing the decats takes me upto my max boost that my standard turbos can cope with(Maximum) anyway, then i guess i'll be waiting 'til i ever get the dosh to upgrade the turbos and everything else that then requires a boost controller.

Cheers for the info fellas ;) it's been very educational, but if "I" do it then it's gotta be right first time round as i hate doing the same thing more than once :eyebrows:

I best go and do ma shopping :thumbs:

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Not quite scouseman. You can't lower boost from its 'natural' level - If decats means your boost is now a very dodgy 1.4bar then a boost controller cannot lower it to 1.2 bar, only raise it higher than 1.4bar.

 

FCD doesn't lower your boost either. It is only the restrictor ring which has the ability to lower your boost through adding a 'bottleneck' to the exhaust system. This bottleneck creates enough back pressure for the turbo's wastegate to regulate boost enough such that pressure stays below 1.2bar. All the FCD does is fool the ECU into not cutting fuel (via stopping the fuel injectors) until later than it would normally, allowing you to run that higher than standard boost pressure. The confusion here is because the Thor version (VFCC) still allows you to have fuel cut at whatever level you desire through means of adjusting 2x rotary switches on it - the good thing about this is your car will just all of a sudden feel like it's hit a brick wall (fuel cut) when accelerating. This serves as warning to you that your boost level is too high and protects the engine through not allowing it to continue to operate until boost falls below this set level again.

 

Hope this clears it up?

 

Cheers,

 

Brian.

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