Centrifugal To TT (A&A to TTix)...My Build
05-09-2012, 07:14 PM
#301
Melting Slicks
Member Since: Apr 2005
Location: Chicagoland Area IL
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I think I follow what you are saying, but all I really did was open it up to the size of the flanges/wastegates. I really don't see how the initial shape of that port of efficient, and well, it wasn't...lol. These housings are really meant for am internal wastegate the way I understand it. Far from ideal, and I think it depends on the backpressure to push anything out of that port. That is why I dropped 4psi by adding mufflers. Now it will have a hole that can flow as much air as the wastegate.
As for venting the wastegates, I think it would hurt boost control with open or very high flowing exhaust. With some backpressure there I expect it to just make things easier for the wastegates. It's an experiment though. As for the noise, I liked the straight 3" pipes. I doubt some loud exhaust only when in boost will bother me.
It's too bad wastegates couldn't be mounted on the manifold flange at the proper angle. No room on these cars.
As for venting the wastegates, I think it would hurt boost control with open or very high flowing exhaust. With some backpressure there I expect it to just make things easier for the wastegates. It's an experiment though. As for the noise, I liked the straight 3" pipes. I doubt some loud exhaust only when in boost will bother me.
It's too bad wastegates couldn't be mounted on the manifold flange at the proper angle. No room on these cars.
My comment did pertain to initial shape with it’s divergent angles while turning flow.
As general rule it’s not a good idea to turn and expand flow at the same time. I think manufacturer favored turbine flow vs. wastegate flow. It is a compromise in that what works best for turbine hurts wastegate and vise versa. Since your looking to get more boost control, then opening up port is the way to go along with optimizing for less losses. This will however hurt your turbine flow a bit – no free ride.
When I said keep your divergent angles shallow (less than 8 degrees), that is to keep flow laminar and attached (less losses). By incurring losses (pressure drop) it’s just like downsizing wastegate. Expanding/decelerating flow (pressure recovery) has some limits that may surprise people… a 45 degree divergent angle is worse than a abrupt step change…
The picture of your reworked port is fine. My suggestion was to blend entry into port (leading and trailing edges), this will favor wastegate performance over turbine (it’s a compromise). Also if you don’t have the room it’s ok to oval it. Your after area here.
05-22-2012, 02:49 PM
#302
Melting Slicks
Thread Starter
I got it back together over the weekend. It seems to have dropped maybe .5-1psi. Hardly worth the effort. I don't think much else can be done. IMO it comes back the fact that these internal wastegate exhaust housings just don't/can't direct enough air simply because of the design. 3" downpipes and these larger turbos require a larger amount of air to be bled off. The wastegates can do more. The air just does not get diverted that way.
I replaced the s-shaped dipstick with a lokar wrapped in fire sleeve, stuck my o2's back in, and added a bung on the driver's side(closer to #7) for the wideband. Drivability is better and checking my oil is no longer a pain.
I really wanted the ability to adjust boost so I could have fun with the car on radials, dial it up for races, and to be able to do a boost by gear/mph setup. This was part of the appeal of TT on this car. For 950rwhp I would not do it again, and I would not recommend it. However, I think I will end up cranking the car up over 1k rwhp, and it will make the power effortlessly compared to a ysi with less headaches. I want to set this car on fire when I have to get in there and deal with the turbo and piping, but I love driving it, and I haven't had any reliability issues to speak of. The added ground clearance vs the blower is really nice as well. Driving around in 95* heat with some stop and go, I never saw coolant temps over 200*.
I replaced the s-shaped dipstick with a lokar wrapped in fire sleeve, stuck my o2's back in, and added a bung on the driver's side(closer to #7) for the wideband. Drivability is better and checking my oil is no longer a pain.
I really wanted the ability to adjust boost so I could have fun with the car on radials, dial it up for races, and to be able to do a boost by gear/mph setup. This was part of the appeal of TT on this car. For 950rwhp I would not do it again, and I would not recommend it. However, I think I will end up cranking the car up over 1k rwhp, and it will make the power effortlessly compared to a ysi with less headaches. I want to set this car on fire when I have to get in there and deal with the turbo and piping, but I love driving it, and I haven't had any reliability issues to speak of. The added ground clearance vs the blower is really nice as well. Driving around in 95* heat with some stop and go, I never saw coolant temps over 200*.
05-22-2012, 05:03 PM
#303
05-22-2012, 05:39 PM
#304
Melting Slicks
Thread Starter
This setup actually adds a little more to the front end than the blower. Well, a lot more I would say. My radiator cradle is no longer lowered. Places on the TTIX kit where you do give up ground clearance are not really critical spots. I don't scrape coming out of the driveway anymore, and I can take inclines at a more direct angle when needed. The downside is not being able to lock the wheel to the left. I no longer forget, and I know how far to go though. Not huge deal really.
