jakeoster Posted March 3, 2011 Share Posted March 3, 2011 I'm having a manifold made and its come time to choose the flange. Now for the RB25 i was looking at running a T4 flanged Precision 5857 with either .68 a/r or .58. How would that compare with say a T3 .76 a/r on the same turbo? Would the T4 housing in this case make any sort of noticeable difference? The reason I want a T4 flange is because if my RB25 ever goes boom or I get the itch lol, Id essentially be a long block and harness away from swapping in an RB26 (among other minor things). This manifold will work with all RB engines and is a big investment so I'm just trying to future proof it as I would be interested in making very significant power with a 26 with a large single turbo. Thanks. Quote Link to comment Share on other sites More sharing options...
synthtk Posted March 3, 2011 Share Posted March 3, 2011 I run a ForcedPerformance HTA GT3582R w/ 1.0 T4 Divided housing and have no problems with spool on my 2.6... I think .68 and .58 would be too small personally. I'm having a manifold made and its come time to choose the flange. Now for the RB25 i was looking at running a T4 flanged Precision 5857 with either .68 a/r or .58. How would that compare with say a T3 .76 a/r on the same turbo? Would the T4 housing in this case make any sort of noticeable difference? The reason I want a T4 flange is because if my RB25 ever goes boom or I get the itch lol, Id essentially be a long block and harness away from swapping in an RB26 (among other minor things). This manifold will work with all RB engines and is a big investment so I'm just trying to future proof it as I would be interested in making very significant power with a 26 with a large single turbo. Thanks. Quote Link to comment Share on other sites More sharing options...
Canadianz Posted March 4, 2011 Share Posted March 4, 2011 Is the manifold your buying designed with both bolt patterns in it ? If so thats pretty cool, I know that the Rb20/25 both share the same pattern but the 26 is different. For simplicity I would try to go for which ever flange suits your turbo and goals best. I know that alot of guys are getting tons of power of t3 framed turbos such as the gt3170R or similar without sacrificing spool. A T3 holset might be worth a look too(hybrid). If you ever switch to a T4, it is literally a 10 minute cut and weld to change up the turbo flange, decent flanges are about 40 or 50 bucks. Read as many turbo charts as you can and figure out what would fit best for your goals and go with it. Just double check that they are indeed drilling two sets of holes so as to suit both the 20/25 and 26 heads if you want to use the manifold on both in the future. Quote Link to comment Share on other sites More sharing options...
piston Posted March 4, 2011 Share Posted March 4, 2011 Housing t3 or t4 makes no difference as long as you match it with the flange you have. Twin scroll or single! I would prefer a t4 flange just because more options for bigger hp turbo's comes with a t4 flange. Same a/r specs on either housing would do the same on damage. t3 t67 .82 exhaust .70 intake. t4 with same a/r specs makes same performance. Quote Link to comment Share on other sites More sharing options...
jakeoster Posted March 6, 2011 Author Share Posted March 6, 2011 Sweet, thanks for the guidance really made things more clear. And yeah, it's got a bolt pattern to suit either the 20/25/26. Quote Link to comment Share on other sites More sharing options...
Sig_Fiend Posted April 12, 2011 Share Posted April 12, 2011 I'd ask yourself how much power you're looking for. Under 600whp, T3 flange is fine. Over 600whp, definitely go T4 as it's just easier, more options, etc. T4 divided is even better and can result in better transient response. Something like a Tial v-band housing would be another excellent choice, making install and adjustment considerably easier. One thing to watch out for is coming up with a turbo combination that is a severe mismatch, or basically a configuration on the extreme end of things. People sometimes fall into the method of thinking that if choosing one thing improves a certain aspect, going to the extreme in that direction is going to make it that much better. One way I see this a lot is people tend to size housings on turbos too small for the task at hand, thinking it's going to gain them a huge improvement in response. In reality, I've actually seen a few situations where smaller housings have actually increased lag. Synthtk's recommendation would make for an excellent setup. Quote Link to comment Share on other sites More sharing options...
Snailed Posted April 13, 2011 Share Posted April 13, 2011 t3 t67 .82 exhaust .70 intake. t4 with same a/r specs makes same performance. That's sort a missleading way to say that (I think I know what you mean though) Just to clarify. The same A/R turbine housing on different frame turbos does not equal the same performance in any measure, spool, response, restriction etc. A smaller A/R in a T4 can flow better than bigger T3 A/R. I would only bother with a divided housing if you have a divided manifold with the proper cylinders feeding each volute. Otherwise, you are adding unneeded turbulance from the divider. The gains from a properly designed pulse manifold are better on other engine designs rather than the I6 but there are still gains in low to midrange RPM response, just not as prevelant as they would be with an I4. Divided housings do not help high rpm power. Quote Link to comment Share on other sites More sharing options...
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