Volcom86 Posted February 10 Report Share Posted February 10 I got a built closed deck EJ257 Cosworth engine - 2.6 stroker 81mm crank Cosworth 99.75mm pistons / rods 14mm head studs Cosworth ported heads and Cosworth everything else cams (268 ex & 277 in) springs, etc. Stock location FP Red turbo with an upgraded GTX35 compressor wheel Internal gate with a 15psi spring Invidia Exhaust Q300 exhaust Trying to run 27-28psi however, WGDC% I get a peak of 28psi at 5,000RPM then falls to 24psi by 7,000RPM I don't think I would be running out of turbo creasing on the WOT pull as IAT's are decreasing on the run, is the internal gate struggling and do I need to go with an EWG? I have always noticed this boost trend even when it was tuned for 21psi - I would get 23psi then drop down to 21psi by 7,000RPM #rd gear log attached which is the Virtual dyno picture attached Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 11 Report Share Posted February 11 Try feeding it slightly more wastegate duty in the areas it drops below what you want, wouldn't be surprising if it is trying to push the gate open a bit more up top. If adding more wastegate duty doesn't provide more boost then either the turbo is out of flow or the wastegate needs to be held shut better. Volcom86 1 Quote Link to comment Share on other sites More sharing options...
Volcom86 Posted February 12 Author Report Share Posted February 12 2 hours ago, Vaughan said: Try feeding it slightly more wastegate duty in the areas it drops below what you want, wouldn't be surprising if it is trying to push the gate open a bit more up top. If adding more wastegate duty doesn't provide more boost then either the turbo is out of flow or the wastegate needs to be held shut better. Thank you, I been thinking also that perhaps my wastegate actuator pre load on the arm might be a bit high. Could this cause the spike in psi as the gate isn't opening soon enough? Thank you Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 12 Report Share Posted February 12 the actuator preload will affect your minimum pressure (like the wastegate spring rate will) where a higher preload or stiffer spring will hold the gate shut for longer. In terms of the spike and reduce the high point is because of the increase in wgate duty and the drop of will probably be the gate being pushed open more by the higher exhaust pressure by the wastegate Volcom86 1 Quote Link to comment Share on other sites More sharing options...
Volcom86 Posted February 12 Author Report Share Posted February 12 Thanks, so in hindsight putting more preloaded on the actuator arm could potentially help me, correct? Or changing from a 15psi spring to a 20psi spring 21 minutes ago, Vaughan said: the actuator preload will affect your minimum pressure (like the wastegate spring rate will) where a higher preload or stiffer spring will hold the gate shut for longer. In terms of the spike and reduce the high point is because of the increase in wgate duty and the drop of will probably be the gate being pushed open more by the higher exhaust pressure by the wastegate Quote Link to comment Share on other sites More sharing options...
Vaughan Posted February 12 Report Share Posted February 12 I would start by increasing the wastegate duty in the table as adjusting the mechanical system will affect all of the values in both of your boost tables whereas adjusting the setting in the ECU can be easily reversed and is much quicker to do. Volcom86 1 Quote Link to comment Share on other sites More sharing options...
Volcom86 Posted February 12 Author Report Share Posted February 12 44 minutes ago, Vaughan said: I would start by increasing the wastegate duty in the table as adjusting the mechanical system will affect all of the values in both of your boost tables whereas adjusting the setting in the ECU can be easily reversed and is much quicker to do. Thank you, I lowered the WGDC% at 5,000RPM so I see 26PSI, and from 6,000RPM i have increased he WGDC to 63% from 60% it is a warmer day on this run so the boost is lower So 3rd gear WOT is from 2,500RPM to 7,000RPM Peak of 26psi at 5,000RPM then tappers to shy of 24psi at 7,000RPM Now my other question is if I am going WOT in 2nd gear to 3rd gear I see higher boost in 3rd close to 26PSi at 7,000RPM - why would this be My concern is if I want 28PSi at 5000RPM in 3rd gear - that it will overboost on colder days Thank you Quote Link to comment Share on other sites More sharing options...
dx4picco Posted February 12 Report Share Posted February 12 from my experience, shortening the WG arm/ more preload is detrimental to what you are trying to solve. boost control will be even harder down low but little improvement up top more spring would help (if duty doesn't) provided the turbo isn't maxed out like Vaughan said. Volcom86 1 Quote Link to comment Share on other sites More sharing options...
Adamw Posted February 14 Report Share Posted February 14 On 2/12/2024 at 4:50 PM, Volcom86 said: Now my other question is if I am going WOT in 2nd gear to 3rd gear I see higher boost in 3rd close to 26PSi at 7,000RPM - why would this be My concern is if I want 28PSi at 5000RPM in 3rd gear - that it will overboost on colder days This is pretty common due to more load creating more EGT. Subaru's are especially bad as the long primaries exaggerate the affect. There are gear trim tables to compensate for the difference between gears. I also noticed a related effect on our Subaru test car - if you had done a little gentle driving around a built up area for example and the manifold cooled down a little, the first "WOT pull" you did after that would never reach boost target. Volcom86 1 Quote Link to comment Share on other sites More sharing options...
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