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The mkiv Supra Owners Club

Dilema!!


trinitom

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Hi people

need some help with my boost readings!

after found that my j-spec was over boosting to around 1.3/4 bar at full boost!:blink:

I decided to put the 1st cat in!

previously it was RR fitted on my 3" HKS silent hipower and manual BC.

installed my EBC today (Blitz dsbc spec s) and with the 1st cat in is showing stable 1.2 bar at full boost!

for what i know it should by boosting to around 0.8/9 full boost with 1st cat in.

now my question is: do i need to set the EBC to 0.8?

read somewhere that boost can only be raised, if so why it shows 1.2?

is the cat not so restrictive and let boost go to that levels?

thanks...

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The cat(s) restrict the boost level. That's how stock jspec TT's keep their boost levels as they are, the decat removes that restriction allowing boost levels to rise. With a fully decatted car, they WILL hit 1.7 bar without an alternative restrictor fitted.

 

When going bpu, you should remove the first cat at a minmum and ideally the 2nd one. A suitably sized restrictor ring is then required to add in back pressure to keep the boost level to the lowest level you want to see during cold exterior air temps.

 

If you want to raise this, then a boost controller is needed.

 

Fitting a first cat on a BPU car should not be done as it'll raise EGT's signicantly, get the restrictor ring sized out correctly first.

 

Edit - click the blue text above, particularly BPU and read, it should hopefully explain a lot.

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i know that, but why is the boost like that?

it should be at standard boost.

the cat was fitted for the mot by the way.

:yawn:

 

A suitably sized restrictor ring is then required to add in back pressure to keep the boost level to the lowest level you want to see during cold exterior air temps.

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my bc is set to:

i first started to set the warning level at 1.10 bar, and limiter setting to -8, gain set to 5, ratio setting to 0.

could by this the problem?

 

Turn the BC off and find your minimum level, you shouldn't go messing with boost levels with that 1st cat fitted.

 

Get the first cat swapped back to a decat and if you have to, refit the 2nd cat, then think about raising boost (while keeping the BC off). See what boost it's making then and start sorting out levels from there.

 

Have you already done all the other BPU mods? (doesn't hurt to ask!)

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i can’t remove the cat, need to be there for mot reasons.

i believe its bpu.

fully decated, colder plugs, 3" exhaust, uprated fuel pump, fuel cut defender.

are you familiarized with blitz dsbc?

 

If you need a cat for MOT reasons then fit the 2nd one, not the 1st. As mentioned, do that and work from there. Do not raise boost with the 1st one installed.

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It just sound as if you do not have a restrictor ring.

 

You really need to find out, otherwise you will have much more to worry about then next years MOT.

 

the RR was there 56mm. just need the cat to register the car here in jersey, then i can take it out forever!

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If you need a cat for MOT reasons then fit the 2nd one, not the 1st. As mentioned, do that and work from there. Do not raise boost with the 1st one installed.

 

i don't have the 2nd just 1st one.

the problem is that, i dont know how to set that s&*$i BC

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i don't have the 2nd just 1st one.

the problem is that, i dont know how to set that s&*$i BC

 

The problem is not your BC. You need to remove the first cat and replace with a decat. Then, if required by your MOT station, fit a 2nd cat. Get the basics done first, then come back to us :)

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Leave the first cat im, add a small ring and MOT / register it, whatever. Then fiddle about, trying not to blow it up. I fail to see why you can't just register it as it is, but don't drive it on boost. After registering, then experiment with no cats and different rings....?

 

You can sell the BC, you obviously don't need it.

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Why not just spend a few quid and get a second hand 2nd cat from someone on here.

 

I am sure a few people have them knocking around. Otherwise Keron might be able to help.

 

Remove the first cat, throw the 2nd on and get it thru DVS.

 

As soon as that is done, decat.

 

Problem solved.

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Hi people

need some help here, fitted my 1st cat to reduce boost to stock numbers, i thing my RR is to big! (56mm)

boost is going to around 1.2 bar with 1st cat fitted.:blink:

set my ebc limiter to 1.0 bar, but is still showing 1.2 at full boost!

could by any mechanical failure or something else?

thanks..

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Hi people

need some help here, fitted my 1st cat to reduce boost to stock numbers, i thing my RR is to big! (56mm)

boost is going to around 1.2 bar with 1st cat fitted.:blink:

set my ebc limiter to 1.0 bar, but is still showing 1.2 at full boost!

could by any mechanical failure or something else?

thanks..

 

I don't know how to say this without sounding rude, I've explained this numerous times already.

 

The boost controller cannot REDUCE boost. It can only INCREASE it.

 

1. you need to remove your 1st decat

2. If you need a cat, fit a 2ND decat.

3. Turn off the boost controller

4. Get a restrictor ring so that you MINIMUM boost level is met (e.g 0.9 bar, 1.0 bar, etc)

5. Turn you boost controller back on and start setting it up if you want to RAISE the boost level.

 

When you have done that, return here if there are further problems.

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