Quote:
Originally Posted by LuckyX2
If you look at the first picture in the thread, you'll see where BW says it spools almost identically to a 6758 and makes 50hp more. That was back in 2012 and they've since done more R&D and upped the rating by 50hp. So that's where I'm getting the 6758 response with 100hp more thing from; I just hope BW delivers on that.
Also, how much of a difference are we talking here? 5-10hp if the gate cracks a bit? If I were to get one, I'd go twin scroll and at $200+ x2 for external wastegates, the internal option looks really good to me so long as there is not a significant impact.
I didn't find any comparisons in power between IWG and EWG EFRs but I did find an example showing that the IWG of an EFR flows better than an EWG on a Garrett.
GT3582R vs EFR-8374 - Undivided T3's - Back-to-Back Dyno K20 - Honda-Tech
The Garrett crept while the EFR did not. I realize creep is not the issue you were discussing here but this is all I found that compared internal and external. |
Poor EWG boost control at high boost levels is 100% related to poor WG port placement. Blame the manifold builder putting a sharp 90 degree corner to the WG entrance, not the concept.
EWGs offer superior control to IWGs due to the mechanical advantage I mentioned before. It's a limitation of the design with a reasonably sized canister.
As for "losing power" if you drop from 25 psi to 21 psi because you're blowing the WG open, you'll probably lose an easy 40-50 rwhp on an engine like ours. People have constantly been fighting with really high IWG spring rates on the EFRs to keep the boost consistent, which means you're locked into running "kill mode" boost all the time without much adjustment down if you want a solid boost curve. It's the same problems we face on our GT2871Rs and whatnot to a similar extent. If you've got a base WG spring pressure below 14-15 psi, no way you're going to run above 17 psi to redline with any sort of control.
As far as power goes while under boost due to recirculating the IWG, even assuming it's putting zero turbulence in the turbine exit stream (which is not the case), an EWG increases the effective flow area of the exhaust as you get to your target boost. It's like an instant jump from a 3" to maybe 3.5" exhaust. Tell me that won't make some more power at 500 rwhp...
So the EFR IWGs work just fine within a window, but there are downsides just like any IWG when it comes to boost control. Lots of the Perrin blogs mention the trouble holding boost up top, and once they finally went to really high spring rate canisters or expensive billet push/pull actuators to control it, they don't mention the negatives of how you're almost "stuck" with a high level of boost due to the design compromises.