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The mkiv Supra Owners Club

Runnin 1Bar (restrictor ring difference)


Damz

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Fitted a fcd and pump this week. The car is now runnin at an indicated 1Bar exactly on gauge. Car has a full exhaust with 1st decat. Lookin at some old reciepts from previous owner the car had a 2.5inch restrictor ring fitted. I dont know what this size of rr would restrict boost to so im curious as to whether the boost could increase "slightly" if i removed it or is it simply the 2nd cat that is holding it at 1bar and not the rr. Still have 2nd cat in so i know it wouldnt increase much if any but i was just curious.

What on average would a 2.5 inch restrictor ring limit boost to????

 

Cheers

Dave

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So does it still have the second cat fitted? If it does, try removing the restrictor ring and testing (carefully) to see what it boosts to. Test in a higher gear (eg. 4th or 5th) and keep an eye on the boost gauge, be careful not push it past 1.2bar.

 

It it does over boost, then you will need to refit the restrictor ring, before fitting open the hole a couple of mm to allow slightly higher boost.

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I dont know what this size of rr would restrict boost to so im curious as to whether the boost could increase "slightly" if i removed it or is it simply the 2nd cat that is holding it at 1bar and not the rr. Still have 2nd cat in so i know it wouldnt increase much if any but i was just curious.

What on average would a 2.5 inch restrictor ring limit boost to????

 

Cheers

Dave

Dave its a crude method we all use to hold/increase boost what ever way you look at it.....some people are lucky and can get away with both cats out RR in and holding perfect at 1.2 bar, others like me did the same and was hitting 1.4 at times, the shear nature of what you are doing dictates hit and miss results, if you did away with your RR you might gain a little but the 2nd cat will keep things in check....hopefully ;)

 

 

can you safly run bpu levels with the second cat?

 

I wouldn't, mine is running at 1-1.1 with the first in and the EGT's are frankly scary....if you do decide on this I would go easy on the boost levels and get an EGT gauge and watch it like a hawk....as wel as your cat temp sensor warning

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Cheers for replies

 

Sadly dont know any supra specialists in Glasgow area so car is booked into "the garage" in wishaw tmoro to get fueling checked so ideally ill get rr removed in mornin before it goes in.(im guessin rr is on downpipe section but im no mechanic) Other people have said theyve got 2inch rr's so im guessin mine probably will be a 1.2bar at 2.5inch. I dont have a gauge for Egt and to be honest id not made it a prioroty to check since doin mods. Ill make a point of getin it checked.

 

Cheers

Dave

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Removed restrictor ring which was actually 2.25inch and the boost raised from 1bar to 1.2 with second cat still in but the fuellin above 5500rpm went ""dangerously lean"". So once the fuel pressure regulator is fitted should be able to run at a stable 1.2 with 2nd cat still in. Think that will do for now until i get bored again in a few weeks :banghead:

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