I built a very nice engine, small block 396ci, splayed 4 bolt mains, 4340 crank & h beam rods, jp pistons 8.7:1, holly stealth ram intake, brodix RT heads, 72# injectors. It has custom exhaust to hold a pair of T3/T04E .68 trimmed turbos and I had a few questions for anyone familiar with a twin turbo small block tuned port setup. The deck is 0 ringed for stainless steel wire, I am running the big thick copper gaskets for the monster arp head bolt studs. I got it hot a couple of times (stupid electronic fan relay, another story..), the most recent time, i shut it down just before it got to steaming, but my blowby increased significantly, and i get white smoke out of an exhaust leak on the passenger side, and out the pipes, AND is mysteriously eating coolant, so I suspect I blew a headgasket, at the very least, it is leaking. Anyway;

Question 1: I am running a boost line from the pipe connection on the turbo itself to the bottom fitting on the wastegate to 'help the spring out' under boost conditions, so it bypasses more exhaust as the boost goes up. My question is, should I run plenum boost source to the top fitting on the wastegate to 'inhibit' the wastegate opening due to TRUE boost source? Or should I just block it altogether.

Question 2: The T3/T04E combo has a 2" out. I put a 2" - 2 1/2" conversion rubber from the turbo to the coldpipe, and then run 2 1/2" coldpipe to the intercooler. Mainly I did this because the inlets on the nice intercooler I got were 2 1/2". Should I convert the intercooler over to 2" inlet, and run 2" coldpipe from turbo to intercooler, and will it give me more consistent boost?

Question 3: Basically where is the best place to put the bovs? I put mine in the intake snorkel from the intercooler to the throttle body of the intake system, as close as possible to the throttle body. Does this cause undue turbulence near the throttle body under boost because of the 90 degree holes in the snorkel for the bov mounts so close to the throttle body? I see guys putting them in the intercooler, but my thought was to put them as close to the throttle body so as not to lose boost during gearshifts, maintaining the highest boost in the 'system' once the bovs close for the next WOT.

also, another question. Is it possible I am losing 'intake' boost, as compared to turbo boost due to the venturi effect of the snorkel adapter from 3" coldpipe to the 4" throttle body opening? And should I run 4" coldpipe from the intercooler directly into the throttle body? I am re-engineering a new set of headers and downpipes so that I can move the turbos over about 2.25" and forward about 1.75". This is so the output of the turbo will have a direct shot at the hole I cut in the old battery pan to access coldpipes to the intercooler, and only have one 60degree and one 90degree bend to line up straight with the intercooler. It will also be shorter linear length from turbo output to intercooler intake. Just fyi, the intercooler is actually two cores with individual turbo tanks for the in-side, and one big tank to combine the two cores on top for the out-side. Now it has 2 1/2" inlets and one 3" outlet. I am going to change this to 2" inlets, and move the 3" outlet in the tank to give me a better angle to the throttle body.

in the picture, you can see the 90 degree rubber coming over the radiator mount. Needless to say, I have blown this elbow out about 8 times, so I think its a point of turbulence. The better angle from the intercooler will allow me to change the rubbers out with v-clamps

Thanks for any input anyone might have, I have built many high performance engines for various vehicles, but have never built a small block, fuel injected, twin turbo'ed street pounder like this one, and most of what I know is from research, research, and more research. And NEVER, I mean NEVER take advice on turbo systems from someone that hasn't either built one, or didn't show up with one in his ride

http://70.89.15.157/app/images/396ciTT.jpg

TIA

 

Wow! That's lots of info. Not a twin turbo guru but what i have to say applies to all FI.

As far as a bov location (question 3)... most guys put them in or around the ic to keep it from getting damaged (split weld, etc.) when you have high boost and let out. But i like the idea of keeping the system press up, should work as long as nothing is getting damaged. It looks like they are far enough away from TB as not to disturb incoming air.

I think if you are having piping blow out, to upgrade to the T-bolt clamps. Also make sure all of your pipes are flared with a ridge to help the clamps and pipes stay together. Any exhaust shop whould be able to do this. Or you can make your own flare with a cresent wrench... sounds bad but will work.

 

Kbracing trick is clean the rubber and pipe connection and spray a little hairspray couple and let dry.

 

@phasemaster1, not blow off as in slip the joint, but blow up as in stick your fist in the side of it where the hole is..

@04Silver Crew, thanks, I welded the bungs to the snorkel for the bovs, so no worries there.

 

that is so very true

I have gone through a few sets of gaskets,and while Im running with the leaking gaskets it always makes it run like crap and run hot like you would expect. I would run manifold boost to your wastegates b/c you are not seeing the same psi at the manifold you are at the turbo. i have my bov on my intake tube, works good, but have put them on the intercooler and works well there too...

 

so you are suggesting I run manifold boost to the bottom of the wastegate, and just block to the top fitting on the wastegate?

 

my top fittings are just to atmosphere.

 

thats kinda what I figured, thanks bansheerider44

 

Yeah don't block of the top ports. And sure as hell don't run manifold pressure striaght to the top of the gate.