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No question here, just information, I like to read about peoples weird setups so I assume other people do to.
I have an S369 with Borg 1.0 divided turbine housing on an LS3 with XER273 (224/230 114) cam. I installed a back pressure sensor and thought I would share my results here. I have an AGP 1.27 open housing I am going to put on soon and will post the differences.
My MAP sensor is the standard GM 3 bar. The back pressure sensor is a Zeitronix 50psi MAP sensor, it has the same scaling and costs the same as the Holley 3.5bar sensor so I have it set as that in my Holley HP.
With the engine off, the MAP sensor shows 94kpa and the bp sensor shows 87kpa. So I calculated pressure as anything above those numbers respectively with 6.4kpa as 1psi on the MAP and 5.9kpa as 1psi on the bp sensor.
MAT shows 73* outside temp with the engine off.
This is boost vs bp
5500 6.6--13.2
6000 6.5--15.1
6250 6.7--15.4
6500 7.0--16.4 2.3:1 ratio
The ending MAT is 153* with no intercooler so about 11* per psi of boost, the compressor seems to be plenty at this low boost at least, thats very acceptable temp rise non-intercooled. The bp isn't very good but not terrible either, I am hoping the 1.27 open housing will get it down to 2:1 or a hair under. Im sure as the boost goes up the bp ratio might change but maybe not much.
No question here, just information, I like to read about peoples weird setups so I assume other people do to.
I have an S369 with Borg 1.0 divided turbine housing on an LS3 with XER273 (224/230 114) cam. I installed a back pressure sensor and thought I would share my results here. I have an AGP 1.27 open housing I am going to put on soon and will post the differences.
My MAP sensor is the standard GM 3 bar. The back pressure sensor is a Zeitronix 50psi MAP sensor, it has the same scaling and costs the same as the Holley 3.5bar sensor so I have it set as that in my Holley HP.
With the engine off, the MAP sensor shows 94kpa and the bp sensor shows 87kpa. So I calculated pressure as anything above those numbers respectively with 6.4kpa as 1psi on the MAP and 5.9kpa as 1psi on the bp sensor.
MAT shows 73* outside temp with the engine off.
This is boost vs bp
5500 6.6--13.2
6000 6.5--15.1
6250 6.7--15.4
6500 7.0--16.4 2.3:1 ratio
The ending MAT is 153* with no intercooler so about 11* per psi of boost, the compressor seems to be plenty at this low boost at least, thats very acceptable temp rise non-intercooled. The bp isn't very good but not terrible either, I am hoping the 1.27 open housing will get it down to 2:1 or a hair under. Im sure as the boost goes up the bp ratio might change but maybe not much.
You can expect to lambasted and ridiculed here because your sensible street ride does not have a hotside you could drive a truck through, and your backpressure ratio is not less than 1/1.
No question here, just information, I like to read about peoples weird setups so I assume other people do to.
I have an S369 with Borg 1.0 divided turbine housing on an LS3 with XER273 (224/230 114) cam. I installed a back pressure sensor and thought I would share my results here. I have an AGP 1.27 open housing I am going to put on soon and will post the differences.
My MAP sensor is the standard GM 3 bar. The back pressure sensor is a Zeitronix 50psi MAP sensor, it has the same scaling and costs the same as the Holley 3.5bar sensor so I have it set as that in my Holley HP.
With the engine off, the MAP sensor shows 94kpa and the bp sensor shows 87kpa. So I calculated pressure as anything above those numbers respectively with 6.4kpa as 1psi on the MAP and 5.9kpa as 1psi on the bp sensor.
MAT shows 73* outside temp with the engine off.
This is boost vs bp
5500 6.6--13.2
6000 6.5--15.1
6250 6.7--15.4
6500 7.0--16.4 2.3:1 ratio
The ending MAT is 153* with no intercooler so about 11* per psi of boost, the compressor seems to be plenty at this low boost at least, thats very acceptable temp rise non-intercooled. The bp isn't very good but not terrible either, I am hoping the 1.27 open housing will get it down to 2:1 or a hair under. Im sure as the boost goes up the bp ratio might change but maybe not much.
Thank you for posting this information. The numbers you measured are very close to what the BW Matchbot comes up with. If I remember right, Work Turbo offers a stainless 1.30AR v-band turbine housing for this turbo. You can probably run 10psi without having worse BP issues.
I bet it is a blast to drive!
Andrew
Last edited by Project GatTagO; 01-19-2019 at 04:07 PM.
Well frig, the 1.27 open doesn't seem to be any different back pressure wise. Attach is a pic of some of the housings, doesn't really show much.
It does spool very fast. I had a billet PT7675 on an LS2 with these same heads, intake, cam, injectors, and this is noticeably more response but not a huge amount. In the logs cruising along anywhere around 2000rpm or lower and flooring it it shows 1psi at 0.4 seconds so it is fast. It is a th350 with a relatively tight PTC nitrous converter so rpm vs boost doesn't really make sense compared to a manual.
The thing that is a little odd is it doesn't seem to peter off all the way to 6500rpm. I had a TC78 on a 6.0 many years ago and it seemed to really struggle up there...I wish I knew what the bp was on that.
Can someone that speaks fluent "turbo compressor map charts" help me out and explain the data contained in that link?
There are links at the bottom of that page that have excellent tutorial videos.
Basically what it shows is that this turbo is about maxed out as Hank is using it. The far right dot is about falling off the compressor map. What is more interesting is that the predicted back pressure in the exhaust is about what Hank measured. It isn't exact, but pretty damn close.
It also shows that at 6500rpm he is making about 650hp at the crank, which sounds about right.
Well frig, the 1.27 open doesn't seem to be any different back pressure wise. Attach is a pic of some of the housings, doesn't really show much.
It does spool very fast. I had a billet PT7675 on an LS2 with these same heads, intake, cam, injectors, and this is noticeably more response but not a huge amount. In the logs cruising along anywhere around 2000rpm or lower and flooring it it shows 1psi at 0.4 seconds so it is fast. It is a th350 with a relatively tight PTC nitrous converter so rpm vs boost doesn't really make sense compared to a manual.
The thing that is a little odd is it doesn't seem to peter off all the way to 6500rpm. I had a TC78 on a 6.0 many years ago and it seemed to really struggle up there...I wish I knew what the bp was on that.
127
if no change when turbine housing was changed... next thing to check is post turbo exhaust?
I have the smaller S369 SX-E S300SX-E 9180 (66mm Ind. / 91mm Exd.)- (13009097049) with a 1.02 AR turbine housing. I wonder if it will have similar back pressure on a 5.3.
01-18-2019, 05:22 PM
Single S369 on an LS3 back pressure 
