Extenal Wastegates Options

[elvasoshexai]

ok.. so the wastegate actuator on my ct20b is fubared.. i get boost creep like crazi...

i was going to get an external wastegate to replace it and weld the internal one shut.

i just hv a question about size.

i was planning on getting a tial 38mm w/ either .5(7.252psi) or .6(8.702psi) bar... i hv an mbc and plan to run probably 10psi neway tho...

however, the shop my car is at, a customer has a 48mm wastegate but wants a 38mm and he said that customer is asking if i want the 48mm turbosmart wastegate in exchange for a tial 38mm...

i'm assuming 38mm is a good size for a 5sfte...

would i b better off w/ the tial 38mm or the turbosmart 48mm?
the 48mm seems kinda big... i'd possibly get a lot of lag?
not sure what other pros/cons there would be between the 2?

any help? thnx

This post has been edited by elvasoshexai: Nov 28, 2007 - 12:59 PM

[OOBE]

Dude, a 48mm wastegate hole is huge. You'll probably get boost problems. You don't need it. It's overkill. There are Mirage 4G93 engines in the island pumping over 400 WHP on 35mm wastegates like mine. Why spend more money and risk getting in trouble, when you can go for the tried and tested route? Get a 38mm and be done.

[Tony_the_Tiger]

Dude, a 48mm wastegate hole is huge. You'll probably get boost problems. You don't need it. It's overkill. There are Mirage 4G93 engines in the island pumping over 400 WHP on 35mm wastegates like mine. Why spend more money and risk getting in trouble, when you can go for the tried and tested route? Get a 38mm and be done.

Stop spreading misinformation. You can't get "boost problems" with a larger wastegate. You can never "overwastegate" a turbo setup. The larger the wastegate valve, the lesser it has to move to evacuate exhaust flow. This also means faster control of boost since the valve only has to crack ever so slightly to maintain boost.

The only downside is cost and finding room to install a larger wastegate. Other than that, there are no downside in the performance aspect.

Also, no one rates wastegate with "WHP". It goes with manifold design and exhaust pressures. The lower the exhaust pressures, the more wastegate it needs. Every engine is different in terms of exhaust pressures. Anyhow. larger turbos always use large turbines which greatly reduce exhaust pressures, thus, we commonly read about the need for larger wastegates for larger turbos. Lastly, manifold design, such as the wastegate placement has the largest impact on wastegate sizing. A wastegate placement that is opposing the direction of exhaust flow will have a hard time redirecting exhaust out of the wastegate. A manifold such as that, would need more wastegate.

Example of a poor wastegate design that requires a larger wastegate... Notice how exhaust needs to turn the opposite direction to exit the wastegate:



Example of a good wastegate placement that requires a smaller wastegate:


This post has been edited by Tony_the_Tiger: Dec 2, 2007 - 9:25 AM