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The mkiv Supra Owners Club

Surprising Decat results


AMG

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Finally found which pipe had popped off stopping the second turbo kicking in and took it out for a thrash.

I now have no cats and a restrictor ring but managed to achieve 1.34 bar with no fuel cut kicking in at all. When i had just my first cat in i was hitting fuel cut at 1.25 bar. Is this expected? Bit worried that i am getting over 1.3bar at the minute.

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I have uprated my plugs (HKS) and at the minute have no FCD wired in (did have one but took it out for a bit and when tried to wire it in again it is giving me trouble, so not in at the mo). The turbos were rebuild (to standard spec i presume) about 2 years ago.

 

No miss firing that i can tell and still with the standard pump (although i admit i have not checked to see if it has been upgraded before me).

 

I am planning to upgrade my pump and get a FPR at some point but want to make sure it is going to be ok first with regards to boosting, can't afford another blow up.

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yeah pretty sure it is right. Only been getting about 0.7 bar on first turbo only because a pipe blew off the EGCV last week. 0.7 lines up with what i should be getting when had the problem so presume the gauge is right.

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yeah pretty sure it is right. Only been getting about 0.7 bar on first turbo only because a pipe blew off the EGCV last week. 0.7 lines up with what i should be getting when had the problem so presume the gauge is right.

thats a fair point mate, might be worth double checking with another gauge if you get the chance, or it could be a genuine reading, mine is a j-spec full decat and hits a maximum when its feckin cold of 1.24 bar

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...and still with the standard pump (although i admit i have not checked to see if it has been upgraded before me)

 

You've got a 93 car there, so that fuel pump could be 12 years old. If it's performance has dropped to 90 or 80% with wear you might wanna check if it's been replaced to prevent running too lean (don't ask me anything technical about this comment as it's just what I've picked up from other threads and I know sod all about cars)

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You definetly have a funny sounding problem. Although looking at fuel pump won't hurt (for information purposes) it's not really the problem as I understand it.

 

If you car was hitting fuel cut previously, running lower boost, it should do exactly the same now. Something is wrong and I wouldn't drive it on high boost until you have sorted it out.

 

1.34 bar is way beyond the fuel cut limit and beyond the safe operating capablility of the standard turbos. You should:

 

1. Check your pressure gauge tubing for blockages.

2. Fit the FCD you have.

3. Get a new restrictor ring.

4. Not drive at 1.34 bar on a standard fuel pump.

 

:rtfm:

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Fuel cut doesn't kick in instantly at 1.0bar although that's the minimum threshold for it. If you are getting these boost figures off a peak hold, that's what it is - a peak. Your turbos could spike to 1.3+ bar due to the free exhaust and the cold weather, but then the boost could drop off again before fuel cut clobbers it all. With a cat in the boost wouldn't build so fast so you'd only get to say 1.2bar before fuel cut kicked in. It's kinda of time/load/delta related but no-one knows the exact profiles of overboosting that the ECU looks for.

 

Are these spikes or are they maintained pressure levels? If you are maintaining 1.3bar without an FCD I'd find that rather odd, unless you have an airflow tuning box like an AFC installed...?

 

-Ian

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I don't have a AFC mate. The 1.34 bar is the peak that has been recorded by the gauge as i tend to keep my eyes on the road on full boost :eek:

The spiking might explain it a bit better, i will try and keep my eyes on the gauge tomorrow morning on the way to work (traffic allowing). Thanks for your help Ian.

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Todays update is:

 

Just booted it onto the motorway, was watching the boost get higher and higher until it hit 1.4 bar, then i shit out and backed off.

 

On the way home, i THINK i was doin about a 110 accelerating quite hard when the fuel cut kicked in!!!!!! I was'nt watching the gauge at the time but dont think i was at 1.4 bar so maybe it is spiking and dropping but i am shitting it when i see 1.4 and back off.

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  • 3 weeks later...

I've just fitted a set of technics hybrids, my car is UK spec in top condition, IK24, FCD, Bleed valve, full decat 3'' pipe, TRD air filter. When I boot her she hits and holds (quite easily) 1.45 bar which is quite worrying (even with the bleed valve completely closed). I dont really understand this.

 

Another friend has exactly the same problem on his UK spec after fitting hybrids.

 

I'm taking her to C.W tomorrow to have his SMIC fitted and a closer look at the boosting, may need to have a restrictor ring fitted. I know this is standard practice on the Jspec after BPU, but is this normal on a UK?

 

Cheers

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Already checked that mate, it is a stock ECU. I am tempted to change to a mines if can get one but going to try sorting my fuel cut out first. I wouldn't need it if had mines though but might as well use what i have got.

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I've just fitted a set of technics hybrids, my car is UK spec in top condition, IK24, FCD, Bleed valve, full decat 3'' pipe, TRD air filter. When I boot her she hits and holds (quite easily) 1.45 bar which is quite worrying (even with the bleed valve completely closed). I dont really understand this.

 

Another friend has exactly the same problem on his UK spec after fitting hybrids.

 

I'm taking her to C.W tomorrow to have his SMIC fitted and a closer look at the boosting, may need to have a restrictor ring fitted. I know this is standard practice on the Jspec after BPU, but is this normal on a UK?

 

Cheers

 

Looks like our cars are pretty similar spec wise. I'll be getting a CW intercooler fitted in a few weeks too. Did it feel much different after having your (intercooler) fitted ?.

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