mtnickel

Damn. After checking the Dyno thread found your build! I too had done the maths and figured the TD05 and 18g would be a reasonable combo for the RB25 on a stock block looking for about high 200's or maybe just 300kw...especially for a street car. I went with the same turbo 3 years ago: Kinugawa td05 - 18g billet extended wheel. 10cm V-band housing. 44mm gate. Stock manifold. Greddy IM. RB25 S2. Never had it dyno'd, but the response is pretty good and I pushed it to about 12psi which I figured was around 220kw (on nistune). With a NEO head, another 6 psi, and better exhaust manifold, looks like your numbers are exactly what you could expect to max the turbo out at. I'd wager even if you added more boost, you'd only see more midrange torque, but the HP limit is probably about maxed based on the compressor map. Hats off to your for disregarding the internet experts and running what seems like a good fit. While I enjoy the turbo, I really want the sound of an equal length manifold, so I got a little bit of the "while I'm at it" syndrome and am going to swap to an EFR6758 or EFR7163. I'd like to crack 300kw (400whp), but would settle for mid high 200's too. Will see how the response of them compares to the TD05. Now looking at your graph, I'd probably have been fine to stick with same turbo. Hindsight is 20:20. Nice build.

Cool. I'll keep this turbo availability off topic chat to a minimum on this thread and get to the point. Some more digging led me to find this: So I think this is a little more indicative of what a 7163 .80 a/r v-band will do on a 2.5L with a more typical short/log style manifold. The compared turbo is a GTX3576r on .63 TiAL housing. Compression is 10:1, but closer comparison than was mentioned about the long manifold poor flowing Subaru EJ. 10psi by 3000rpm should be a decent threshold. What will be interesting though is how it responds in low gears...hopefully with the mixed flow turbine and light wheel and ball bearing it feels at least if not more lively than I have now.

Those ones stated "rebuild required". Were those The same Ones out got? Maybe they just said that for liability reasons.

I guess I wasn't looking hard enough. From the searches I did all over the forums, in the last year they wanted often $900+ for the 7163. You're right though, he did list a few under: " INDY RACE CAR DALLARA DW12 TURBO CHARGER BORG WARNER SVRA DRIFT OPEN WHEEL " Only 3 sold since July. went for $610, 715, and $695 US. So @ $760, I overpaid by $60-70 on average? Not all of use have the hookups you do. Where is the link to the 6758? @450 is that AUD? or USD? I'd be interested in picking another up for that price for a friend of mine.

I've seen some ancient threads where the guys initially asked that, but recently, they've been wise and we're getting between 600-1000usd. Well at least on the Subaru forums and Miata and such. Show me some recent links of such sales and places they pop up for that much. The 7163 is returnable and it yet shipped. A user on instagram made some flanges. In contact with him. Otherwise will Machine at friends shop. Really appreciate this feedback. Dynos must be different. If the Subaru guys are making mid 330-350whp at all wheels on the 6758, then with a rear drive car should be upper 300s. Will be bolted up by welding a t3 flange to the turbine housing, but now so that I can swap, I'll probably make a t3 to v-band adapter. Either that or make a jig and weld t3 flanges to both turbine housings. May have better resale so people don't need to mess with the unavailable flange. The 6758 should have a fair advantage on an 18g. Bigger better flowing turbine 51 vs 49mm exducer. And a massive compressor size difference (50mm vs 54mm) see dyno of a Subaru with just the turbo swapped between 18g and 6758. Big change in power band. but you raise a good point regarding the torque band and feel of the turbo above 5000. one other users comment resonated with me regarding traction: if I have too quick of spool and low end, it could be unusable power and hard to hook up. The somewhat slow response of the 10cm 18g I have now helps with putting power down in 1st

Well, it's done. Picked up another EFR 7163 for $760US. Not the best deal, but pretty solid. It's one of the indy car program ones. While I was originally going to just weld a T3 flange on the housing, I will now fab a T3 to V-band adapter so I can easily swap them in and out. We'll see if you guys are right on the response of the 7163. You are also Twin Scroll vs my SS. I wouldn't think fuel type would affect spool much, and I thought smaller log manifolds can often spool faster than full size ones but give up power up top?

Followup question: Everyone is pushing for bare minimum of a 7163. Now what sort of boost/power level would be the consensus to run on a completely stock S2 RB25. Stock cams, stock exhaust manifold, Greddy intake. External gate. full 3" exhaust off turbo, no cat, straight through mufflers. I'm pretty confident that 6758 could make a solid 260kw on the above with between 16-18psi. All while not over-reving. Peak power may be closer to high 5's than mid 6's. But should make for a FAT power band. Now, the 7163 with the .80 housing will spool slower but has more potential, but what do I stand to gain on the above setup with a mainly stock build. How high can we push the boost on it while maintaining a fairly reliable setup. I've found a reasonable deal on a 7163 with the same Indy car housings. They actually made them to swap right out for the 6758 on the indy cars when they changed the turbo spec. Maybe I need to get both and swap either one in. Would probably only take an hour or 2 for full turbo swap with all the v-bands I have.

Advice noted. It will be on a stock manifold yes. I would rather sacrifice my power goals for greater response. I know boost 'threshold' can be low on the bigger turbos, but 1st and 2nd gear pulls is where i do 95% of my acceleration, and those sometimes don't hit peak boost till much higher up the RPM band. It will only ever be an autocross car and daily driver. I don't rev out 3rd gear on the highway risking having my car impounded here. Nor do I take it to the track. To put it into perspective, I currently have an 18g td05h with a 10cm housing and it's far too laggy for me in those lower gears. Everyone said don't go 8cm as it'll choke. Well. I wish I did go smaller. I also only ever run between 10-14psi tops. Now that the 6758 fell in my lap for a song, I'm just hoping to have great response, 16-18psi (to be safe on a completely stock block) and hopefully make another 75hp than I'm making right now which I think is very plausible. I don't even mind if it only really wants to rev out to 6k as I hardly push it past there anyways (even though it does keep pulling up there). Maybe this was the wrong thread to suggest a small power goal turbo, as really these EFR can do so much more.

https://forums.nasioc.com/forums/showthread.php?t=2711435 some good supporting info on the efr6758 on a 2.5L. Ill take the 600rpm of spool for the 5-10hp up top. That 2.5 didn't overspeed at 22psi on the sti, but on the rb it may be closer. I probably won't go over 18psi. Cool real world data though. We should plot that turbo on the matchbot and see how the exhaust delta pressures compare to real world.

I'd prefer the housing you have, but as I said, I got this turbo for dirt cheap, so the compromises are worth it. The turbine won't overspeed any more with the smaller turbine, but backpressure will be higher and more flow goes through wastegate. If you adjust he volumetric efficiencies in the matchbot to better reflect where the stock cam rb25 will make peak power, then it would probably go up to about 23psi without hitting the choke wall. At those pressures though backpressure may be chocking where adding more psi isn't making more power. If it didn't fall in my lap for $675, I wouldn't run it. But 675 vs $2000 is a big difference. For moly power goals, I think it'll be great. I'm stock everything anyways. 240-270kw will be just perfect for me.

Touche! I agree. Thanks. I will be back here next year with results. Have to convert turbine inlet to T3 and get it all fitted and tuned. Plus it's my summer car here in North America and won't see driving over the snowy months. Thanks for input.

Here's my match RB25 - 18psi EFR6758 .60A/R I roll down Volumetric efficiency near 7000 since the stock cams will likely make peak power at 6000rpm http://www.turbos.borgwarner.com/go/E51DZB

Ya. It's a stretch to make that power at the pressure level the 2.5L would like to make it at. I did plot it all up in matchbot. I'm not sure what pressure delta's are "OK". I think they were around 11-13psi up at the top end. I plotted up the same turbo with the Focus ST engine and psi's (because they are known to make 400-420whp on this turbo) and they had similar Delta's because they were pushing turbo so hard. They were running like 30psi however to get the turbo into the maximum flow up at the top of the map. Anyone have any thoughts on this? The delta's certainly seem OK in the main RPM band I'll use daily (3k-5.5k). You're commenting on the turbo choice in the EFR thread without even knowing the specifics of the EFR turbo I mentioned...lol. Overall, I think it will work but certainly have it's tradeoffs. I know it will be way more responsive than the td05 18g I have now and it should make 75whp more as well. Time will tell, and I guess I can be the first guiney pig. The smoking deal I got on the turbo means I can't really pass it up.

I hate to be "that guy" who posts: "how much boost do i need for 400wkw", but i have a similarly annoying/unresearched question that I'm really just doing a sanity check on... I picked up an efr6758 in North america (I'm from Canada). it's one of the Indy Car turbos people were liquidating on subaru forums. 0.64 a/r turbine. Mint condition for a price I couldn't refuse ($675cdn=675AUD roughly). Anyways, i'm already externally gated on stock manifold on an RB25 and looking to run this for the ultimate "response" type turbo. Anyone think this is a good choice for the fastest possible spooling RB25 with hopefully around 275kw with aprox 1.2Bar? I haven't seen anyone with an efr6758 on an RB25, but I really just look at it as a good stock replacement that will make 100hp more. Will happily post dyno results when I get them next year. Thoughts? PS. chassis the rb25 is in is a datsun 240z. It's light and I'd really just like response to have it a little more lively in first and second. Current turbo is td05h-18g 10cm kinuagawa billet turbo. 10cm terrible choice. shouldn't go bigger than 8cm for any td05h turbine. My other option is to sell the EFR and get a kando/mamba/kinugawa gtx3071r.