Is a twin scroll turbine housing sized the same as a single?

[float_6969]

OK, a little backround first.

My current setup is a CA18DET, 4 port head, 10.2:1 compression, E85, port matched, polished, un-shrouded valves, 5 angle grind on intake valves, radius cut on exhaust valves, KA TB, stock intake manifold, HKS 264 cams IN/EX, HKS turbo kit (twin scroll manifold, T04E compressor, "O" trim turbine in a .58 A/R twin scroll housing), 3" turbo back.

Here's the problem I have right now. My wideband is overheating and shutting down, basically making it impossible to tune. I didn't used to have this problem. What changed was, well, a lot. Shortly after installing the HKS turbo kit (the stock kit came with a single scroll .48 A/R turbine housing) I had an oil filter fail. That toasted the bearings and ruined the 8 port head with stock cams. I rebuilt the engine to the specs I gave above. During the rebuild, I decided I wanted a twin scroll turbine housing. I had a .48 single scroll, and the closest size they had in a twin scroll was the .58, so I went with that. I've recently gotten everything back up and running again, but if you do much more than idle, or tootle around, the wideband overheats (Innovate LC-1) and shuts down. It didn't do this before. I thought maybe the engine bay was getting too hot (the turbo melted the wiper fluid hose, wiper spray nozzle, and the brake fluid reservoir), so I bought a turbo blanket, manifold blanket, and downpipe wrap. I got it all back together today, and it's worse! Now I'm like

I don't have an EGT gauge, but the LC-1 shuts down if the EGT's exceed 1700°F. If this is the case, this is a REALLY high EGT. Tomorrow I'm going to try and make it REALLY rich to get the EGT's down and see if that helps. But I've also done some research and I've read mention in ONE place that you don't size a twin scroll housing the same as you do a single scroll. The post I read said to DOUBLE the A/R you would run on a single to get what you want for a twin. Is this true? If my A/R is too smal, does a small A/R cause the post turbo EGT's to climb?

As I was doing testing today, I realized that the wastegate was opening (5psi spring) before 3K rpm on the highway in 5th gear. That's REALLY low for a turbo that size on a motor that small.

Any input would be greatly appreciated. I'd really like to be able to datalog my AFR's so I can start turning up the boost.

[compactfean]

2 things cause high egt like that. Afr which I don't think that's what it is. And timing. I would check your fuel pressure and afr (quickly) to see if its an issue.if all is good than I would consider moving the wideband further downstream and maybe even install a heat sink.

[float_6969]

I can't check the AFR's right now because the sensor doesn't work. I could throw a narrow band in there and re-program my standalone, but this is the same tune as before I pulled the motor. The only difference being I went to bigger injectors and altered the fuel map to suit. Fuel pressure is dead on. I have a NISMO FPR and had to set it up before I started the car with the rebuilt motor. Timing is conservative right now, and I suppose I could have too much timing retard, which would drive the EGT's up. I didn't consider that before. I'll try throwing a few degree's of advance in there and see if it changes anything.