Chud wrote: ↑Mon Oct 08, 2018 3:24 pm
Sweet, any reasoning behind the internal gate or just because?
Great question. I've been wanting to do this turbo conversion for 12 years, so let's just say I've had a lot of time to think about it and changed my mind a number of times. There's lots of pros vs cons for both style of wastegate. For this particular setup, there is a great summary here:
https://turbosource.com/blogs/news/choo ... bo-systems
This is what it boiled down to for me (in no particular order of priority):
1. Simplification and reduced packaging: no routing of external gate dumps etc. Where I am, you can't legally have these vent to atmosphere in a street car, so the external gate dump would need to plumb back into the main exhaust. Everything mounts nice and compactly, so I'll have a lot more room.
2. Cost: no fabrication for above. Save on cost of 2x external gates (I would definitely need two). The IWG setup allowed me to use the Turblown kit with the cast manifold. This ordinarily wouldn't fit a RHD car, but since I converted to FC front steering/suspension, I can use the FC bolt on kit. The kit cost a bit, but the cost savings elsewhere meant a saving overall.
3. Weight: the cast manifold is made of 347SS stainless and very light. Being a short runner design, there's not much of it. It feels lighter than a factory FC manifold but I intend to weigh it to see. The whole setup will be a few kg lighter than an external gate setup.
4. Response: short runner design with IWG will spool around 500rpm earlier. This particular setup should see 25psi under 3000rpm and start boosting from around 2000rpm. This is probably the number one reason.
5. Reliability: unlike external setups, IWGs are not directly attached to the exhaust and so are much less likely to fail due to rotary exhaust temps. EWG failure is very common.
6. I don't need to worry about running high boost pressures. 1 advantage EWG systems have is that they can reliably run lower boost pressures. This is great if running on pump fuel as you don't want boost creeping above 15psi. I'm running on LPG, which has a higher octane than E85, plus water/meth injection, so no problems there.
