Firstly, me and raamo both were running the S360SX which has an old pretty average flowing 60mm cast wheel - so yes, we did hit choke at around 19psi but that's not due to the a/r of the exhaust housing - it's due to the compressor wheel running out of flow so you do start seeing symptoms of high exhaust manifold pressure as well, but that's more to do with the turbine having to try and work harder due to the compressor becoming seriously inefficient and needing to be spun harder to move any more air. The fact that the S360SX turbine wheel is also not great for flow relatively speaking is going to be a compounding factor (more on that shortly), but the main issue is the compressor flow imho.Interesting, that's the first I've heard of someone choking git out on that big of an AR. Other 362 SXEs I've seen have made 700+ on E85 or with meth with a nice flat power curve on the top end, no significant drop off the tI would call choking. Do you have a dyno plot showing that choke at ~19psi? I
When we were choosing options for the RB30 we considered the S364.5SX-E but we wanted as much response as possible, seeing as it looks like people may not have analysed stuff as much as I did I might add some data which could prove helpful.Reached out to real street, they recommended the S364.5 sxe as a good option for the price with 500-600whp goals. Makes sense, use the same turbine wheel as the 360 and 362 to get the best response, but maximize the compressor side for pump gas goals. From the dyno plots I've seen with the 362, it doesn't choke up top ~620whp. Will be going with the 364.5 in either 0.68 open or 0.83 divided for a pump gas setup.
- The S364SX-E looks at a glance to flow a lot better than the S362SX-E but the real flow gains are mostly had at over pressure ratio 3.0, which doesn't seem helpful for an pump gas 3litre engine. If you look at the 2.2-2.6 pressure ratio range you're likely to operate in then the S364 may still at a glance look like it has big advantages but actually Borg Warner have mapped the S364SXE compressor map down to 54% compressor efficiency, which is pretty much useless. Anything under 60% efficiency is going to be generating a fair bit of heat and even if your intercooler is up to it - you're going to be needing increasing turbine energy to drive that compressor, which is going to drive up EMAP. For this reason I try and compare compressor maps "efficiency for efficiency", at which point the 64.5mm inducer/87mm exducer compressor has only 5lb/min more effectively flow most of the useful map than the 61.4mm/83mm compressor wheel. Maybe 6% more flow for a significantly larger compressor wheel, definitely larger by enough that you will loose spool and also at reasonable cost to transient response
- The "Use the same turbine wheel as the S360 and S362 to get the same response", going by this comment and other comments in here - thought I'd add that the S360SX and the S362SX-E use different turbine wheels. With our testing so far we've found basically no difference in spool between the two, but just to avoid any anecdotal evidence of how the S360SX turbine performed being used to determine a possible restriction on the SX-Es - it is NOT the same turbine and both looking at the designs, and also the results we've had so far... the SX-E turbine wheel happily flows significantly more than the S360SX one. The wheels are EXACTLY the same size, fit the same turbine housing etc but the aero is very clearly different and adds something to consider in regards to your postulating on the Borg Warner turbine sizes compared to Precision etc. The aero etc mean two different identical sized wheels can behave fairly differently.
- We actually hit the dyno yesterday with the RB30 after upgrading from the .91 S360SX to the .91 (literally the same exhaust housing from the S360SX put onto the S362SX-E) yesterday and unfortunately I can't share as much data as I would like to on the performance of the turbo as we ran into fuel delivery issues when we started turning it up on E85. We stopped at 20psi (just decided that was a good place to stop as we planned to push it harder on E85 as the car is flex) on pump gas (98RON) and saw 439kw @ hubs/588whp with power climbing happily to redline with zero difference to spool, followed the exact same boost curve of the old S360SX.
On E85 we got to about 22-23psi before running into fuel delivery issues so I never optimised the boost control, ignition timing or fuel curve because we didn't want to risk hurting the engine but with a soft tune on the first pull at that level it put down 489kw/655hp @ hubs and was showing no signs at all of hitting any flow limitations at that point. Power was carrying to redline at this boost level, as opposed to the S360SX (again, running the exact same exhaust housing) flat lined from 5500rpm to 7000rpm when targetting the same boost, it basically rolled back to 19/20psi at redline because it just didn't really have any more to give.
Gutted we didn't get to turn it up all the way, but it seemed on track to get to 700whp or more- we're very happy with the results so far - even if this was the finishing point it was a very worthwhile upgrade over the S360SX. Buying a turbo this cheap and gaining this much flow with no cost to response was great, again we had discussed the S364.5SXE but the response and delivery of the 61.4mm compressor would be a hard thing to want to give up for what probably wouldn't turn out to be a hugely rewarding increase in power.
Fun fact - we were hitting 300kw/400hp @ hubs at 3800rpm.