Looks like there is a new EFR 8370. Would it be a good match for stock port REW?

https://turbosource.com/products/cop...5-650-hp-turbo

 

I’ve spoken out against it on a 13B, but there’s some disagreement. I see they have a 1.45 A/R housing listed on that link, but the largest one I’m aware of for the EFR 70mm turbine is 1.05A/R. It may be new release, but I was unable to locate it. A few people on here claim the compressor holds back the EFR7670, but my feeling is that the 1.05 A/R turbine housing is holding it back as well.

One way to look at it is this; the flow limit for the 70mm 1.05 A/R housing is about 23 lbs/min, but the flow limit of the 74mm 0.92 A/R housing is about 29 lbs/min. So on one hand that’s going to spool a lot faster down low, but then be limited on top end or high boost. So the place to start is by evaluating EFR8374 results using the 0.92 A/R turbine including emap if you can find them and then figure that an EFR8370 with the 1.05 A/R housing is going to be operating several steps smaller on turbine flow with more emap and less power/boost potential on the top.

Because even the BWMatchbot shows that the 70mm turbine needs a 1.22 A/R to roughly flow about the same exhaust gas as the 74mm 0.92 A/R housing. Without a larger A/R turbine housing my feeling is that the EFR8370 is going to be a bit limited on a 13B. However, with full E85 fuel, AI, and the full array of modifications you can possibly get away with higher emap to some degree. I’m just not sure it’s worth it over just going with the EFR8374 and it’s proven track record.

Because on a 13B I’d approximate the 8370 with 1.05 turbine housing to be equivalent to an EFR8374 with an A/R in the 0.75-0.80 range; faster spool, but then flow choking a lot earlier too. Haven’t seen one on a 13B yet though. With a 1.15 - 1.20 A/R housing it might be pretty wicked in the 400 - 450 whp range if they ever extend the EFR 70mm turbine housing choices.

They do offer 1.09, 1.15, 1.22, and 1.27 A/R for the SXE 70mm turbine, but I’m not aware of them being compatible or why the EFR range is so limited. Those housings are all twin scroll T3 with T4 flange, so they do require some grinding to transition properly from a twin scroll T4 flange
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I think EFR 8370 could work in an old school pump gas style big port, low boost build (12-14psi boost).

But it will probably be compressor surge city when you try to run more boost like you would on E85 or with aux injection.
The EFR 8374 already spools so hard ~3,300rpm it surges in medium boost (~20psi) so you have to use boost control strategies to slow the spool.

I dont see the point of trying to use the same compressor wheel and spooling it harder.
Probably exactly why we dont have the Turblown variable exhaust housing for the EFR 8374 after all these years.

You need compressor speed sensor and boost control strategy to keep it out of compressor surge with VGT and then its held back so much it doesnt spool any better than the standard EFR 8374. Or so I speculate.

 

Sorry, should have narrowed down the setup.
stock port on 93/94 pump only; no e85, no aux injection.

Around 400-450rwhp max.

sounds like it might fit the bill.

 

The other reply only reaffirmed my statement questioning doing that over an EFR8374; quick spool is not desirable on street gas especially without AI. So why place yourself in that position to start with?

There are examples of the 8374 on street gas only and all hit your target goal perfectly, but feel free to potentially shoot yourself in your own foot. this was reported to be 14.5 psig boost REW stock port.



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Bumping this back up to see if anyone ever tried anything with the 8370 that they can report on? I think TeamRX8 and Blue TII have the right reasoning, and it appears the .92 A/R housing is still the largest option for IWG. But it seemed worth asking if anyone had any experiences to share after some more time had passed.

 

not sure anybody could find/buy one since then until more recently

i ran a few road tests on the SXE Airwerks custom hybrid version (S362SX-E comp and 257 turb) with a 1.15 A/R EWG housing. Nothing formal, no data, just hoping the law didn’t showed up to see what all the open WG dump pipe ruckus was about

Coming off a larger turbo though, not quite as exciting, but also a worn BP engine with a single non-divided WG isn’t the best testing conditions compared to 30 psi on an S369SX-E with a large turbine housing.
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I have an IWG 8370 kit on order from turbosource and will share results when I have some. My objective is to have great boost response on pump gas and IWG to reduce sound because street car. I have a pineapple racing street port and 3.5" exhaust combination that will make an IWG 8374 boost creep and surge. The 70mm turbine used on 8370 is slightly higher trim, doesn't have the creep problems that I could find, and can drive a 7670 well over my boost targets. The downside has already been stated in the thread. The 70mm turbine flows less in the same size housing when compared to a 74mm turbine wheel. This increases emap.

This is replacing a Greddy T88 kit that is fun on highway rolls and too laggy everywhere else. I've mostly had experience with journal bearing turbos on rotaries but have owned multiple modern turbo cars. I love the near instant boost response and smaller turbo sizing on modern cars. I'm chasing the smallest EFR that doesn't fall off before stock redline. If this isn't it, then IWG 8374 with ported wastegate and associated spool penalty is the next step.

Can someone more familiar than me can explain if the turbine flow limit of the 70mm turbine is concern for low boost (running 16 psi today). I looked at it as the required restriction in the exhaust that can improve spool. The BW product materials and turbosource site indicate the pressure ratio on the 8370 will be favorable compared to the 7670 due to the larger compressor wheel lowering shaft speed. I do agree emap it will be higher than an IWG 8374 that cannot run low boost with a 3.5" exhaust.

 

danger Will Robinson, danger!!!

we all want to keep our cake while eating it too, that rarely is possible, especially on pump gas.

attempting to drive a higher flowing compressor with a smaller flowing turbine is generally going to up the knock resistance requirement of the fuel being used.

a more reasonable solution on pump gas would be a larger, properly biased WG on the 8374 EWG housing
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you would want to measure pressure pre turbo and post turbo to see, really. ive looked and very few people have done it, most just do pre turbo, which is ok if you're tuning.
you won't know what your emap or the p/r of the turbine without measuring it

 

I am still considering this kit, but its now $6000+ for the kit and much more options at this price point.

 

Thanks, j9fd3s. Observed data tells the truth, and data is lacking in all 8370 topics I can find. I found zero rotary installations with data shared. Matchbot doesn't have this turbo on it, and matchbot data has lacked integrity (leave known innacurate data) for years. I'll instrument pre-turbo emap and share the data.

Most of the EMAP discussions on the forum have a few loud voices that feel EMAP will be horrendous on anything BW IWG because of past experiences. Heck, I have had this experience and changed 3 different hot sides on an old T04R (1.0 divided FTW!) chasing the desired powerband 15 years ago. Here are the user logged data points I could find which have data regarding EMAP for .92 a/r turbine housing IWG EFRs. The data isn't a perfect comparison for my combination (differences like streetported, have a 3.5" exhaust, wheels). I should be a better starting point than feelings.

gxl90rx7
This user has posted the only data samples I see shared for 7670 IWG EMAP. This is a stock port REW in an FC that sees track duty. EMAP is lower than IMAP through redline. 3rd-5th gear pulls shared. Had undersized intake filter area.

https://www.rx7club.com/3rd-generati.../#post12461644
https://www.rx7club.com/single-turbo.../#post12433175
https://www.rx7club.com/single-turbo.../#post12456535

alexg13b
This is a thread where water injection was blowing out spark. This is 8374 IWG, stock port REW, 3" exhaust. EMAP lower than IMAP until after 6k RPM, then stays close to 1:1. He has lots of logs trying to figure out spark issues that could be good data points. Screenshots are in the thread. I don't see impending doom there.

https://www.rx7club.com/single-turbo...power-1157178/


Based on this data, I'm encouraged to test out the 8370 IWG with <20psi for a street car. I'm guessing due to the larger mass compressor, that there WILL be EMAP than a 7670. I'm comfortable with up to 1:1 EMAP all day if that is what it is around redline. At the same time, the turbo shouldn't be off the right side of the compressor map like a 7670 can be on this engine. Data will tell.

 

Matchbot does have it; you use the 8374 compressor map and align the turbine points on the 70mm 0.92 AR phi line map

which that turbine peaks around ~ 24 lb/hr, which is going to choke around 375 whp on a 13B, but you probably can’t get there on pump gas, below 350 whp is more likely

I know it’s not what you want to hear, but this idea is not well founded in general, especially so on pump gas. It will surpass 1:1 emap much sooner than you’re recognizing.

What examples using the 7670 with 0.92 A/R turbine are you looking at? Those are not running out of compressor. Even the 1.05 housing isn’t either despite a few claims otherwise. The EFR 70mm turbine housing A/R is the issue, more so with the 83 compressor. Without a larger A/R the EFR 8370 is more applicable to a piston engine setup.
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that is nice detective work. you also mention the other way to do it, which is just to try different ones. its more expensive and maybe it takes longer (you have to try it), but its a valid way to do it

 

it would be interesting to see, but i think you're probably right

 

it’s really simple, making a certain WHP requires a specific compressor intake flow, which then generates a specific exhaust turbine flow that has to pass through the turbine/WG.

Just review BlueII’s 7670 results with the 1.05 A/R EWG turbine. Except with this the intake flow comes on sooner, and then the turbine flow too, but with a tighter turbine housing and on pump gas.

The only EFR 7670 0.92 A/R results I recall were mediocre at best, but I better go back and refresh my memory. It’s easy enough to run the numbers on Matchbot. I did, but quite a while back. I know where the flow limit of the 0.92 IWG housing is relative to a 13B, and it’s low.

going back to the EFR 8374, the reason the low boost control issue exists is because the IWG isn’t big enough. So with a free flowing exhaust the turbine is the path of least resistance and goes that route rather than the IWG path. That’s why it’s not an issue on higher boost and also why porting the IWG helps a bit at low pressure. So the obvious solution is the EWG housing with a suitably sized/biased WG to provide a less resistant path around the turbine at low pressures.

the quicker response and higher emap of the smaller EFR 70mm turbine is in direct conflict with using pump gas. If it was E85 he could wind it up just like Blue did, but again is going to hit the turbine flow choke line sooner than on the 1.05 EWG Blue used. There’s no free lunch to be found here.

Who on here would run a Garrett GTX35 compressor with a GTX30 turbine and 0.82 A/R housing? That’s really what the equivalent flow ratings are. And the EFR7670 is really equivalent to what the Garrett GTX3076 was. But nobody was willing to do that back then, though they could have before the EFR came out.
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I'm expecting 1:1 to happen 5500-6000 RPM based on what I can glean from matchbot and where others see 1:1 with 7670 IWG. Maybe it is sooner given the turbine and wastegate flow and this wheel. This part isn't clear to me, and I'd appreciate input since you are sure its sooner. I expect to need to lower boost demand if EMAP is too high. Anything 12psi+ should provide enough flow for my goals.

I'm looking the 7670 compressor map and what is required to push 55 lbs/min at high RPM. The compressor will be over the choke line at the 16 psi spinning nearly 110k rpm. The 8370 would only be at 95k and 68% efficiency. Cludwig's thread on 7670 1.05 EWG measured compressor speed on stock port REW and showed the issue I'm modeling on matchbot.

Thread: https://www.rx7club.com/single-turbo...esuts-1088491/.


Now its time to wait and see what the compromises look like. Constraints that influenced decisions: BMS pod filter on the turbo will be undersized, 3.5" exhaust tends to boost creep (prepared to need to port wastegate given the compressor), will only consider IWG options. Maybe I'll be happy, maybe I'll be wrong and buying the next size up turbo. At least it will bolt on to the rest of the kit.

 

so as you might have seen as you read the thread they didn't measure the pressure drops of the IC and intake, so while the turbo RPM is right, the p/r was likely higher than that plot (0.5psi for the air filter and 2psi for the IC are the book values)
which makes the 16psi, 6000rpm at 2.3 pr, which makes it more like 48lbs/hour, remember we know turbo rpm, engine rpm and manifold boost, but we do not know pr!

and then B all of that needs to go out of the engine, with some fuel too, the heat in the exhaust matters, but if the EGT is normal, ~900c, then you need about 39lbs per minute of exhaust flow, and about 4lb of fuel mass, so 43lbs per minute on the exhaust side. i don't know about the BW turbos, but Garrett only shows us one efficiency island on the turbine, and its not very clear what happens outside of that. it does seem like it can flow more, but efficiency drops, although again nobody had ever measured that (you need temp in and out)

i'm not sure about how an internal WG is rated, but an external WG probably takes up the difference (if you need 40lbs of flow, but the turbo only does 20, the WG needs to do the other 20)

 

One thing to note, and I don't think Chris knew about it at the time, but the IC end tank had an opening about 3/4" to 1" long that was missed during welding. It was discovered later and fixed, and I'm not sure how much it affected the results, but I wanted to make note of that.

I'm interested to see how the 8370 performs. I swapped to an IWG 8374 after that 7670 had failed oil seals. I like that it pulls all the way to redline, unlike the 7670, but I miss the low end grunt of the 7670. The 8374 still spools pretty fast, but I'd still be interested in a mix of the two.

 

pump gas vs E85 though, that’s the thing and the only reason for erring on the conservative side. Quick boost at low rpm requires knock consideration.

Even I disputed the sticky turbo thread at the top of this forum area that pushes the 1:1 compressor vs. turbine dimensional sizing theory, because true turbine flow capacity, fuel type, porting type, etc. etc. all influence the end result. Which there is a dyno result on here for a EFR7670 1.05 EWG on a BP REW that made 430 whp @ 13 psi boost to help provide some context.

I think there’s some disconnect wrt how the larger comp housing is going to affect the loading from where those past results are. I also disagree with some of the assessments that were made. What he didn’t show in that thread were the turbine plots and turbine flow/pressure data. You can visualize the estimates in Matchbot though if you understand how to do the inputs.

but no sense flogging the horse … so best wishes.
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So I’m going to eat my words above by realizing my head wasn’t on straight and perhaps in a dark, moist, yet not so pleasant aroma place instead when they were written. The reality is that the exact same compressor will display entirely different map results when matched with different turbines. I had completely spaced out about this reality.

A good modern example of this is the Garrett G-series -900 compressor, which is available from Garrett on the G30, G35, and G40 frame sizes. If you were to lay those compressor maps down side by side by side with no other information, it’s easy to conclude they’re different compressors. Except they’re not, it’s the same compressor, and the turbine assembly it’s paired up with influences the flow output and efficiency.

Which is really what I was trying to communicate in my latest replies regarding the EFR 8370, but perhaps not so effectively. So no, until Borg Warner produces the actual 8370 compressor map data rather than copying over the 8374 map, we can’t really plot it out with certainty on Matchbot. That said, the difference between the G30-900 and G35-900 might provide some insight to the EFR 8370 vs 8473 in a general sense.

The difference being understanding what the flow rates relative to A/R on the EFR are, but also understanding the A/R options are more limited on the EFR than the Garrett G turbos. I hope that clarifies my position better. I also want to emphasize that if the goal was a responsive 450 whp autox application, I’ll give the nod to turning up the boost wick with the 8370 on E85 or C16 race gas. i might be on the conservative side advising against it on pump gas, but I suppose the only way to find out is to go there.
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I personally use water injection, and I plan to tune on E85 but I'm not sure how much I'll actually use it. I never used it the whole time I had the Syvecs lol.

All that said, when I first started asking about the EFR in 2011/2012, people scoffed at the idea and said to just stick with the tried and true GT35R. I'm glad I didn't listen. Although the 7670 is a bit small for the rotary, I was very impressed with its response. If only it would be capable of pulling to redline, but it's not crazy far off. It did die an early death with the oil seals failing, and it does have a weird harmonic ringing right between throttle and coasting (I verified this on my buddy's FC as well). The 8374 is really well suited for the rotary, I just wish the response was like the 7670. I don't have as much disposable income these days, but I'd still be willing to try it at some point. Looks like others will beat me there though.

 

Lucky 7 racing has one installed on a street port pump gas FD build. We should get real world results soon including 7670 comparison from the same dyno. Supposedly ready to dyno this week:
I’m buying sensors and such to instrument the install on mine. Shaft speed, egts, and emap. I’ve got just enough inputs left on the Adaptronic for those.

 

Going by butt dyno I understand what you are saying. You never dynoed your car, right?

We feel the torque drop off in the higher rpms with EFR 7670 and feel torque surge up again when you shift (weird feeling for a rotary).

To some degree I guess it depends on the rest of your engine/peripherals set-up and how high you set the rev limiter over stock redline.

My EFR 7670 maintained horsepower past FC's 7,000rpm redline to the 8,000rpm rev limit even as boost dropped from a peak of 26psi (4,000rpm) to 21psi (6,500rpm to 8,000rpm).

Boost dropped because of high priority dual 44mm external wastegates being pushed further open by exhaust flow at all boost pressures I tried. Would have had to run top WG ports to hold boost.












And here is a half bridge internal wastegate EFR 7670 at 13psi on E85

 

But I understand wanting to retain the rotary feel of horsepower INCREASING all the way to redline.

So, my next EFR set-up for my FD is going to be IWG 8374 on short manifold with low boost (plus boost creep) with big ports and 9,000rpm rev limit.

Torque at wheels from 5.8:1 differential ratio instead of high boost.

I will probably have to put a plenum on the LIM to shorten the runners and pitch the HP toward the high rpms.