| I recently read some posts about someone thinking of doing an external wastegate on a turbo upgrade.. I have seen a few different options of converting a normally internally wastegated turbo to externally. The ones I have normally found is where the internal wastegate is either welded shut and an adapter is used AFTER the turbine housing with an external wastegate and V-Band clamp to connect the new exhaust downpipe and wastegate. The one thing I did not like about this setup is all the exhaust gases still had to flow through the small internally wastegated turbine housing. Now I have noticed a new style of external wastegate option. This style looks a little more effective.. since the external wastegate is located directly on the turbine housing "swirl". Although it still looks as if the turbine housing is blocked and not as bad as the older options I have seen similar to this setup. Its hard to beat the boost response of an externally wastegated turbo. Although we have the Forge actuator as an option for our internal wastegate options which give very sharp boost response and help greatly against boost creep/spikes etc. I however do not like using any type of tubular exhaust manifold, whether that be 304, 400, 409 series or even better/ more durable different grades of SS, Inconel or Titanium. Even I know that 409SS should be used on the really hot sections but its more $$, And when it reaches the collector a cheaper 304 etc can be used. Usually a lazer cut, CNC machined manifold--> cylinder head flange is made of 304SS or even cheaper, (good quality) mild steel since the expansion rates are so similar. However; Even when designed very well, it will EVENTUALLY crack. If very meticulously engineered, Proper bracing, heat cylced/treated, and even Cyro-treated.. It can last years of high abuse.. but eventually end up with cracks, that will throw off your tune and need to be repaired. This option that ATP turbo offers (T-25EWG-44). Will allow us to use VERY reliable MS exhaust manifolds and have the option of having the boost response of an externally wastegated setup. I am not sure if this option would be possible due to how the turbos are setup, due to the turbine housings being so close the the manifold and engine block itself. The turbine housing itself is sold for about $300. Supposedly it flows just like a full T3 true external wastegate and it only offered with a .72 a/r turbine housing, Which is just a tad smaller than being in the middle of the .64 a/r and .86 a/r. Which are the Z32 common sizes. So not only should the boost response be better than a regular internally wastegated turbo, but the increase in flow from the exhaust having a more direct flow by having a big fat true 3" downpipe. So the slightly larger .72 a/r, rather than the very commonly and preferred .64 a/r exhaust turbine housing should produce slightly more power in the top end and not have any more lag because of the other benefits that the external wastegate and true 3" downpipe will offer, I would think that it would balance itself out. This is what ATP says..
"Special turbine housing, T25-EWG-44, T25 inlet flanged, GT28 style 5-bolt outlet. External gated (44mm flanged), flows like a full T3. Available for GT28RS/71R/76R, full size 60mm GT3071R/GT3076R/GT3082R turbine wheel and Stage III (76 trim) turbine wheel. Allows full T3 flow but on T25 flanged manifold. Only available in .72 A/R. .72 A/R is built to GT30 geometry so this A/R is comparable to one that is right in between a .63 and .82 A/R GT30R housing. " Here is a picture.. 
I am wondering if it would be possible to machine the collector area by adding some material to the ductile iron (MS used to add material to the stock manifold and then port the collector area to increase the flow to the turbo which was very effective.) If material was added to the new MS cast manifolds and a 44mm external wastegate flange was fabricated to fit. We would be able to use a true external wastegate turbine housing.
Unlike a true external wastegate, where the wastegate is located on the exhaust manifold itself to very efficiently control boost, since the exhaust gases will take the path of least resistance, when the wastegate opens, It will almost instantly cause *almost* all exhaust gases to escape through the wastegate, causing the turbine wheel to have less force, thus causing the turbo to immediately stop building boost. Most of us Z'ers (unless purchasing a either custom SS tubular manifold or use a Pentroof (NLA if I recall correctly), or possibly a Greddy manifold etc.. Interested in some thoughts on this... or possibly some quiet projects that are utilizing this type. If some things work out for me better I may try to purchase one of these turbine housings and see if I can get them to be possible to use with MS manifolds and look into if I can modify my MS for an external wastegate setup. I have a Mill and Lathe comming soon, so I am sure I will begin to fabricate all kinds of stuff!
NO, This picture is not photoshopped. It took many times to take this picture. Setting up the timer, shutter speed etc, then jumping on my bike and getting the tire to spin.
AIM:Shawn300zxTT "-Any closeups on the nuts? - zboost(tx) 19:17:53 08/08/05
-Not really something you want to ask another man about... (n/m) - LordZ 19:24:00 08/08/05" "I just took 45 min and scrubbed the heck out of my rear"
teambushido(San Diego, CA) 19:24:51 12/11/04 -1991 Stage _ TT 5spd (Upgraded to hell and back)
-1990 Super White 2+2 Na Stage 3 Auto (Daily Driver, contemplating selling.. )
-1990 Cherry Red Pearl ,Auto Coupe (Parts car)
-1990 11 Sec Eagle Talon Tsi AWD, (SOLD!)
-1996 Hyundai Sonata (Given to me for FREE , due to broken timing belt,bent valves.. fixed it myself and its my new DD that gets over 25 mpg!
-2004 Honda CBR 600RR (Candy blue, FOR SALE) |
Possible external wastegate setup with MS manifolds.. - 
