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Discussion Starter #1
... for the stock ceramic turbos on a R33 GTR?

I've got a custom set of down-pipes straight through to back box, no cat, standard elbows and turbos AFAIK. I've got a power FC controlling the apexi boost control kit. Now this is identical kit to the AVCR solenoid therefore should be able to control boost as well.

If I start from low rpm, and allow boost to build with rpm, no problem, solid boost held in any gear. But if you go WOT at say 4500 rpm (or following changing gear whilst making "good" progress ;) ) I get boost spikes followed by an undershoot then build back to stable boost. This can be as bad as 1.15bar on the 0.95 bar setting.

I've got the solenoid fitted with the shortest pipework the RB26DETT setup allows, and I've logged solenoid duties through datalogit, but the best I've got is a compromise, i.e. I run lower than optimum start duty, to control spikes (max 0.1bar overshoot) at the expense of spool-up plus sometimes not hitting target boost when accelerating from rpm below the boost threshold (around 2800rpm for 0.9bar in 5th).

I'm sure I've read that some tuners fit slightly undersized decat pipes to increase EGBP and control over-boost on a stage 1 setup, but has anyone else had experience of this, or any novel ideas to fix it (best I've come up with is refitting the standard cat to restrict the exhaust a little)?

Any help gratefully appreciated :)
 

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Knock up a sandwich plate with a smaller hole in it to restrict your exhaust a bit like Supras sometimes have. Should be a piece of proverbial, and if it don't work, it was only a couple of quid and a bit of time :)
 

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Discussion Starter #3
Nice idea

Sounds like a good idea tath, cheers.

But as I have the cat to hand I could always just fit that. I expect power will be down a bit though,

Any other smarty-pants have good ideas??
 

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SIHethers said:
Sounds like a good idea tath, cheers.

But as I have the cat to hand I could always just fit that. I expect power will be down a bit though,

Any other smarty-pants have good ideas??
The Cat gaskets are 75mm bore, the downpipe-elbow gaskets are 65mm bore. Fit a downpipe gasket in place of the cat front gasket, ala restriction....

Regards
 
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