As many of you have seen I have a 12a blowthrough set up. Many have given me advice on this build and i really appreciate it. Some of it was a little after the fact but anyways it was good advice. The boost box/carb hat I made previously was too small and the boosted air entered facing straight into the carb (i designed it this way not knowing that it should be at a 90 degree angle or that the volume should be 1.3 X or so of the combustion chamber. That being said I never was able to get my car tuned fully. This year I will be building a new one. Does anyone have any advice tips or plan ideas?

This is my setup...

-12a Streetported (rebiult, RA super seals)
-1 piece intake manifold
-OER 47 racing carb(side draft) 2 barrel
-custom Turblown short runner exhaust mani and down pipe (3.5 in)
-Turblown stage V gt35r
-external wastegate(TiAL 44mm)
-3.5 in exhuast(straight through all the way)
-2.5 in intercooler inlet outlet and all boost tube piping
-HKS ssqv blow off valve.
-3.5 psi fuel pressure at zero boost with 1 to 1 rising rate FPR.
-MSD ignition (dual 6ALs)
-Locked dizzy 10 deg advanced
-planning 15-20 psi boost
-OMP blocked off (planning 1.5-2 oz premix per gal)

Thanks

 

as of right now im thinking of using a piece of plate and making an L shape and then using a 3.5 in tub cutting it length wise and attaching it to the L.. Here is a quick sketch? Any pros or cons?

 

The biggest problem I see is that with timing locked at 10BTDC its going to be a lazy.

If you do any highway driving or cruising you will ruin your turbo and exhaust manifold due to having timing about 25 degrees retarded. They will glow red and put heavy loading on these parts, and the associated heat soak will also cause BIG problems not to mention poor efficiency and being ugly to drive. Cracked fuel lines, burnt wiring, discoloured paint.

I've been in a single turbo 12AT locked at 20BTDC and its still a bitch. They don't idle if you have timing in them to make power and cruise, they don't cruise right anyway because cruise wants 30+ BTDC and peak power wants 10-20BTDC. You are always going to be fighting a loosing battle. Heaven forbid the engine over boost. Your distributor is locked at so many degrees timing, you have no level of protection at all.

Next problem is going to be where you are metering your fuel in. You have a lot area to wet when you meter the fuel in at that location at very low airspeed compared to the factory FC/FD 3 barrel with the secondaries blocked off. I have tuned a throttle body injected rotary before as well as the same motor port injected. I am telling you the difference in behavior between a port injected rotary is night and day. On each throttle change you will be building up a stack of fuel on the manifold walls and you have probably 20 times the area you could have if you designed the intake and fuel injection points smartly.

You stab the throttle and that massive throttle shot wets the walls, fuel falls/ gets drawn off the stack so that the engine is happy on a throttle stab. Then on the next deceleration event you pull in all the fuel that wet the walls. I've seen it on the wb02 and felt all the annoying peculiarities tuning the motor. You get the motor running nice sure. But look at the big picture of a small acceleration event followed by cruising results in your mixture being around 10:1 for 10 seconds after you have backed off.

The year is 2011 and the technology is cheap FC parts are worth nothing. There is no need to be building a car that is going to be a **** to drive. I can see the equipment you have is good for a low 10 ET once sorted but you are possibly going about it in the least refined way possible.

 

I had it at 10 deg last summer and it was not slow at all with 7-8 psi...
it drove ok and accelerated pretty hard.

i know what you are saying about effeciency.. i know im in a losing battle there...

others have told me that 10deg locked at idle is good some say up to 15. i have checked the timing the way that i have it locked idling at 10 deg... at say 4000 rpm or 5000 rpm it advances to about 20 deg.. i welded the two pieces in the dizzy together and then bolted the outside one down.... they are locked together.. however they is a slight flex in there somewhere... not sure how or why or if it is play in the dist gear? but it is working in my favor i feel.

last summer i set the 4-5000 rpm advance at about 10-12. maybe i should go a little more from what you are saying? i just dont want too much advance... the only thing i have to go off of is others advice and trial and error