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Discussion Starter · #1 ·
Guys,

I want to purchase a Random Technology kit that come with Hi Flow CAT and downpipe. But I need to know a few things before I get it. I know that if the full downpipe is installed (no cats) than boost will rise up to 15 psi and BCC is required to avoid the boost cut. What I would like to know is if I install the Random Technology Hi Flow CAT with downpipe, will the boost still spike to 15 psi and I still need to get the BCC or it will be well under the boost cut level? Also do you guys recommend getting a boost gauge to monitor boost levels or I should be safe with out it? I just want to make sure that I do that correctly, because I don't have the money to fix/rebuild engine or turbos due to spikes in boost or over boosting. Any help or comments are appreciated.

Thanks,
Vitek

P.S. BTW the reason why I am looking at the Hi Flow CAT and not full downpipe is due to legal issues in CA.
 

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1) Of course you should install a boost gauge.

2) About the necessity of a BCC. You will need it with or without the Random Technology High Flow cat, assuming that you use a boost controller or run your car in cooler weather. You will undoubtedly hit 15psi.

Also, believe it or not, your turbos will be less likely to fail if you do not have any cats, because this allows them to operate with less stress. Of course this assumes that you are not overworking them at an obscene boost level.
 

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I had an RMM dp w/ no cats and a tanabe exhaust. With stock boost and I would hit ~11 lbs on the primary and ~14 lbs when the 2nd turbo kicked in. Never spiked, so Im sure you could get away w/o running a BCC if need be. With that said, 99% of Supra owners will eventually push their cars past stock fuel cut, so why not just get one anyways?

Asking if we recommend a boost gauge is like asking a doctor if he recommends using a stethescope to listen to your heartbeat. :doh:
 

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You may not need the BCC if you stick with stock (plus whatever extra boost de-cat gives you) wastegate control. It may depend on how healthy your stock seq. system and turbos are. Your question about whether or not to get a boost guage is funny- if you are going to spend $600 on the Random set-up you must be looking for perfromance. In that case, you do need to know boost pressure and possibly A/F info.
 

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I don't get enough boost long enough to hit the cut. I think with the newer cat you would have a better chance but it would still probably be top of 3rd or top of 4th.
 

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Discussion Starter · #6 ·
Alright, it looks like I will definitely need the boost gauge. Any recommendations on which one to get (Greddy, HKS, Stillen etc...)? Also with the BCC installed, is there any way to control the boost so it doesn't go past 14-15 psi? I know that the higher to boost you run to lower the life expectancy of the engine and/or turbos. So I am trying to balance the power and reliability. Sorry, if I am asking a dumb questions, I am still learning as I go with the upgrades.

Thanks.
 

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I just installed a Greddy 52mm electronic w/black face not too long ago. I like it b/c it looks very stock. i would rather have psi units (kg/cm^2 (pressure / g) are retarded pressure units in my opinion)

 

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97TT6SP said:
I just installed a Greddy 52mm electronic w/black face not too long ago. I like it b/c it looks very stock. i would rather have psi units (kg/cm^2 (pressure / g) are retarded pressure units in my opinion)

Retarded? USA being practically the only country in the world to still use imperial units, I'd disagree. Possibly you mean BAR would work better for you??
 

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97TT6SP said:
I just installed a Greddy 52mm electronic w/black face not too long ago. I like it b/c it looks very stock. i would rather have psi units (kg/cm^2 (pressure / g) are retarded pressure units in my opinion)
Im sure thats what the rest of the world thinks about our inches and feet :rolleyes:
 

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I love SI units, but pressure units divided by G (9.81 m/s^2) IS retartded. What, are we are going to compare our boost pressures to aliens on Jupiter?? No. I would have prefered kPa (or bar). Anyway, you do notice virtually everyone on this forum references their boost to psi units right? I just think 17 psi is just cleaner than 1.172 bar...etc.
 

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Stock ECU shuts down the gas when you hit ~14 psi. If you dont want that happens, you will need a BCC or FCD.
If you don't want to over boost, you need to use a boost controller to limit the max. boost. This is what a boost controller do.

Need a boost guage? Depends if your boost controller integrate one. How would you setup a boost controller if you don't have a guage to monitor?

BTW, removing the stock CATs (either one) is illegal unless you don't pass smog w/ the OE parts and the smog shop tells DMV that you need a replacement. Then, DMV will let you replace it with a new OE part or aftermarket that pass smog.

please bookmark mkiv.com. Its your friend.

BAR or PSI? It just a personal perference. Americans use PSI and Japanese car use BAR measurement.
 

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Discussion Starter · #13 ·
Supra JZA80 said:
If you don't want to over boost, you need to use a boost controller to limit the max. boost. This is what a boost controller do.
Correct me if I am wrong, but I heard the boost controllers can only control boost higher than what is automatically produced by turbos. What I mean by that is say you installed downpine and your boost will automatically rise to ~14-15psi compared to a boost with CAT's it will only be 11psi max. But again I could be wrong. If any body can clarify it, that would be great.
 

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Vitek said:
Guys,

I want to purchase a Random Technology kit that come with Hi Flow CAT and downpipe. But I need to know a few things before I get it. I know that if the full downpipe is installed (no cats) than boost will rise up to 15 psi and BCC is required to avoid the boost cut. What I would like to know is if I install the Random Technology Hi Flow CAT with downpipe, will the boost still spike to 15 psi and I still need to get the BCC or it will be well under the boost cut level?
I have the Random Tech cat and downpipe on my '98, with a Tannabe cat-back. No BCC and no boost-controller. I do NOT hit the boost-cut/fuel-cut. I was very pleased with the upgrade, with the turbos spooling faster and a quite noticable increase in power, while retaining a cat in the system (and not having to tear-into the car too much).
 

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What he said ^

BTW, to answer your question, you don't need a boost controller with the plan you have. And, yes, a BC cannot control pressure to lower than what is normally produced.
 

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i run a 3" downpipe with random technology high flow cat, and i can run 28 + PSI no problem,

it truly is an amazing part, works like a charm, my car doesn't smell anymore, installed 3 years ago, had it welded on.

-Brett
 

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actually the random technology high flow cat installed nearest the turbo's will allow you to pass the tailpipe test. as for a visual if the smog guy is a dick you will most likely be failed due to missing the other cat...i currently live in california and have a random tech highflow cat nearest turbo's with an rmm downpipe and the apexi n-1 exhaust....to pass visual i got an old oem cat...gutted it and welded ontop of the downpipe where the second cat was at..every time i get pulled over by the chippy's...they put the sniffer i pass..they look under i pass....they write me up for modified exhaust...and i'm on my way
 

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First off, why are you posting 28 psi? This guy just wants to go a few PSI higher than stock. He stands a chance of not needing a BCC. You, on the other hand will most certainly need a BCC.
Next, why does Mr. Joe think you can't pass smog with the second-gen RT cat? I did, TWICE! and the last time was test-only!
 

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MtFujiSupra said:
First off, why are you posting 28 psi? This guy just wants to go a few PSI higher than stock. He stands a chance of not needing a BCC. You, on the other hand will most certainly need a BCC.
Next, why does Mr. Joe think you can't pass smog with the second-gen RT cat? I did, TWICE! and the last time was test-only!

I also passed tailpipe with the high flow installed near the turbo.

I failed visual...
 
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