Let’s talk about Turbine Size theory and manipulation. 83mm on 6.0
11-06-2018, 08:29 AM
#11
Staging Lane
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Think im going to start with 4 in down pipe exiting somewhere shortly after firewall with a 4 in bullet style muffler and measure back pressure and go from there. Also going to measure back pressure pre turbine to see where the baby wheel is limited. Been reading a little about using map sensors to data log back pressure. This sounds like a fun experiment as well instead of just having a check ball for max.
Heads are box stock 317 and motor is just a little 05 lq4.
Thank you Atomic for the Clarification on the loss from A/C
Heads are box stock 317 and motor is just a little 05 lq4.
Thank you Atomic for the Clarification on the loss from A/C
11-06-2018, 05:04 PM
#12
Ok so trying to understand this and need some pros to weigh in. It is understandable that much more exhaust can move through a hot side with a larger turbine wheel but is it not close to the same manipulation with different a/r housing on a given turbine wheel?
Working problem....... so LQ4, mild cam (triple 12) single billet 80mm compressor wheel with t4 83mm turbine with 1.1 A/R. Sounds like exhaust side will find too much back pressure around xxx hp or boost. What would be the result in changing the AR housing to 1.25 vs getting 87 or 92mm turbine? Is the change in housing like adding 3% capacity vs 15% with the wheel? Any math that can help me or any working knowledge?
Working problem....... so LQ4, mild cam (triple 12) single billet 80mm compressor wheel with t4 83mm turbine with 1.1 A/R. Sounds like exhaust side will find too much back pressure around xxx hp or boost. What would be the result in changing the AR housing to 1.25 vs getting 87 or 92mm turbine? Is the change in housing like adding 3% capacity vs 15% with the wheel? Any math that can help me or any working knowledge?
usually no one will mess with just swapping an AR around, unless you just happen to have to laying around. You are correct at XXX power that baby wheel will cause a bunch of back pressure and will hurt top end power. BUT will be a blast to drive off the line. The larger wheels + large AR will allow much higher top end power at the cost of bottom end fun off the line grunt. Dont bother with the 87wheel. get the 92 or the 96 or the 100 t6 . 100 for max effort stuff. Several customers have the 92wheel and are having a blast with balance of response and top end power.
4" down pipe will flow a huge amount and being as short as it seems your rolling with will not show much in the BP world. And you do not want it to.
The only down fall to NO bp in the final exhaust in some cases requires a larger gate or a 2nd gate, since that BP also backs up in to the pre -urbo exhaust helping to open the gate.
The system is more efficient and requires more BYPASS to keep boost in check.
Had customers go from a full exhaust to a fender bump and ran into boost control issues.
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