11 replies to this topic

[toyotatodd]

So i know that opening up the stock 1j twins can cause boost spikes. I have seen many people writing about putting a 2" restrictor in the exhaust to keep it from happening but no real info on it working or not. what would be the point of running 3" exhaust if ya need to run a restrictor? i would rather not run one. I was planning on running 3" pipe straight out to a 3" magnaflow. Anyone think i will have boost spike issues? thanks for the help

[redbullx83]

I haven't had any spike issues and I'm running 2.5 no cat straight I had it @ 12pounds no spike and stock boost.

[aphxero]

Ive seen it happen when it's cold out and at low elevations. Maybe 16psi hitting cut. just try open DP before you make a 3" exhaust. Anything increasing the VE of the engine will raise it. Big IC and piping or big intake would do it also.

[toyotatodd]

yeah i am running a front mount but its not very big. and im only running 2.5" piping and the intercooler ia 27-5.5-3 with 2.25 inlet and outlet. and i well run a DP first and see what it does. if it spikes would 2.5" exhaust help? boost controler?

[rayray]

i don't think you will need to worry too much about turbos fouling out with all the stock electronics and nanny's in place. with my stock 1JZ setup my twins lasted forever and a half and are still good. that included some track time, and a ton of pulls on the freeway. as annoying as it is, stock fuel cut does a pretty good job at keeping the ct12's from committing suicide. kicks in at just under 1kg of boost. i put nearly 40K miles on mine which is really good considering they were used to begin with. there is slight play, but don't burn a drop of oil.

i ran the stock downpipe coupled to a 3" high flow cat and exhaust. stock boost (always) no boost controller, just an intake and front mount (also 2.5" piping). still good for 280whp/tq

even "overboosting" to 16-17 psi for a moment isn't going to hurt the engine though, what's your concern?

[Guy Smiley]

A boost controller will not lower your boost buddy, only raise it. You will probably run into boost cut in 3rd, maybe 2nd gear. Just man up and get a SAFC II and a fuel cut defencer. 1JZ's can take 14-16 PSI all day long if you adjust your injector percentage with a piggy back.


Just try it out first and correct it from there. Most people run restictors as a temporary fix until they up management. Then when they get to the next level, they only have to remove the restriction instead of making a new exhaust system.

(I'm running 2JZGTE stock ct20a twins TTC with 3" cat-back, gutted cat, only making .83 bar, never hit cut)

[toyotatodd]

Im not concerned with what the engine can take at all. I just dont want to grenade the twins. I plan on getting an safc im just trying to get it driveable at this point. I will just have to beat on it a bit and see what it does i have a PLX wideband and boost gauge coming so I will just watch and see what it does. my problem right now is finding a damn downpipe flange.lol where i live it fucking either super cold of really fucking hot and im at damn low elevation so i was just curious as to what people were doing to keep the boost at a consistant range. I have a 255 walbro going in tonight so fuel doesnt bother me. guess i will wait and see what she does.

[JimmyHoffa]

You will grenade the twins, then you will replace them, then they will go again, and you'll learn that big single is the way to go. skip the learning curve, get a big single already

[mranlet]

I suppose you could jam one of these in the exhaust to keep the VE down and reduce cut, but I'd suggest wiring it in.

$120 woot

[rayray]

if you decide to keep the twins, keep a spare set handy or prepare to go single. it could be one week, it could be 2 yrs. when they go they just kinda go. my first set grenaded within 3 months (rear, then the front). then the second set lasted over 3 years

single is definitely the way to go. less things to go wrong, easier to spot and fix a problem should they occur. removing a set of the ct12's once was more than enough for me.

[toyotatodd]

yeah i plan to go single. i have already been buying parts here and there for the conversion. I just picked up the engine so im gonna have to run it with twins till i get everything running ok then i will swap it over to single. its not the daily so i dont worry about it sitting for a bit. only the exhaust side of the stock ct12's are ceramic right?

[iheartMX83]

im currently stock twins with stock dp to a stock 7m cat to a 3" catback. no problem. never hit cut.

i removed plently of twins. just go single when they blow. welll fucken worth it