Pump 93 on the street. efr iwg 8374 or 7670?
 

Assuming stock ports, stock seals, 93 octane w/water injection, 375-425 whp for reliable fun on the street. Which do you choose?

I feel like for that whp goal, you could go with either one. The 7670 seems like the slightly obvious choice, but with reliability in thought, does running the 7670 at higher boost pressures add significantly more heat to the engine bay than the 8374 at lower boost? Is the 8374 turned down too low at 375-425?

8374

the 7670 is a little small for your HP goal on pump fuel.

Wow, it looks like the 8374 wins by a landslide. I figured the 7670 would be preferred on a street car. I've just been reading Blue TII's 7670 thread and Turblown's 8374 thread for the past few weeks and I'd have my mind set, then change it when I read the other thread. It's just hard to figure out with all the different variables and with my power goals seemingly falling in between the two turbos.

The 8374 makes sense though. Lower temps. Max reliability. Easier to add power later on if I get the itch (this could possibly be bad for the wallet). To those who voted, thanks for the guidance.

Much more power under the curve with 8374.. The smallest for any Efr fans imho

This is just an opinion from compiling others results:

Autocross and street (less highway more city): 7670
Peak power may be more around 350-375 with water injection, but your broad low and mid range power will be great. With it falling off a bit in the higher rpm range.

Larger open tracks, and street (more highway less city), and drag racing: 8374
Being better on temps for higher rpm operation while still spooling quickly. (Not as quick as the 7670, but not slow either) Won't fall off towards redline.

If anyone disagrees based on their experience with both turbos, I will not argue. This is just my composite opinion from other's results.

I voted, I am also torn between the two. you put a power goal of 375-425WHP, and at that power level I would think the EFR 8374 is the better turbo, definitely if you are located at higher altitudes.

The EFR 7670 will be a better low rpm turbo, now one must think about this.

If your goal is say 350WHP, I would want an EFR 7670, because its going to require higher PSI, typically higher PSI will shift your power in the lower RPMS better. So a 16PSI EFR 7670 turbo at sea level running 350WHP will have a super wide power band and easy to drive. a 350WHP EFR 8374 probably boosting 14 PSI will probably not be nearly as wide, and harder to drive. it won't be as responsive as well.

If you run the EFR 8374 closer to 16-18 PSI it will probably be a 375-430WHP turbo and be more responsive down low than running it lower PSI, and the EFR 7670 can't get that much power down unless you really wind it out. so I would shift to the larger turbo.

For my type of driving I would probably drive faster on an EFR 7670 and perfer it. I have been in an EFR 7670, but I have never ridden in an EFR 8374. so perhaps my assessment is wrong.

I voted EFR 8374 for the street.

At pump gas boost levels on the street the 8374 is the turbo to get the power you want.

You want power to burn on the street and response doesn't matter as much. Everybody expects a turbo to be laggy so they will let you brake boost anyways or count honks, etc. If you miss shift or get a late start you just make excuses and redo the race like everyone else.

If your just hooning you want power!

Its not like actual timed racing where you want the response of the 7670 to be consistently .05th second faster at every corner exit so it adds up to something at the end of the race. Or you want the response to capitalize on an opening/mistake to pass.

Besides, gas mileage really sucks with the 7670 as it is always spooling. Always.

Is it possible to get the 8374 turbine with the 7670 compressor?

The better flow through the 8374 turbine helps a lot with temps, but its compressor is excessively powerful for a street car and the smaller compressor of the 7670 would still allow it to spool more quickly even though there'd be lower exhaust pressure at lower RPM.

This seems like the common problem with all aftermarket turbos simply not being made for rotaries. The smaller turbos that spool quickly, which can provide well enough boost at 7000 RPM simply have too restrictive of turbines. While the ones that aren't restrictive have too large of compressors that add to the boost creep.

If I could get the 8374 turbine with the 7670 compressor, I think that's definitely what I'd go for.

That, or a 7670(or 7064) with an exhaust bypass to get around the restrictive turbo at higher RPMs is actually the ideal. But then you'd have to keep taking it out and cleaning it since carbon will probably build up on the valve.

You cannot get this combo. This is basically what our TDX57 is FYI.

Hm yeah. That's a more stock like compressor to turbine ratio that seems more suited for a rotary.

But it's no EFR, and it reaches peak boost later 400rpm later than an 8374 despite having the same 74mm turbine wheel size and 61mm compressor wheel size that's between it and the 7670.
So one would just be better going with the 8374 or 7670 even though the compressor/turbine sizes are mismatched for our engines.

Actually, it seems like the 7163 compressor would be ideal for street applications. It outperforms the stock twins from the 1800rpm the first one comes on all the way up until redline, in a single little turbo! Pretty much double the airflow across that range.
... except it chokes the crap out of the engine and creates more heat due to that.
7163 compressor with the 7670 turbine and a much, much larger wastegate seems like what we need.. Or just the 8374 turbine and housing for that matter.

Guess I'll have to dream that BW will give more options that fit us, or someone else figures out how to fit the 7163 without it choking and making too much heat. Sure, the 8473 is still better than previous options, but there is lots of room for improvement. Seeing the unrealized potential there sucks.

There's also the option of something like a S200 SXE which has more housing options..

TDX57 uses a 57mm compressor wheel, I think you are referring to our TDX61. Which yes is roughly 600rpms slower compared to an IWG 8374 on our shorty configuration.

Honestly you are overthinking this. There is no real reason to try to get a better powerband. You simply will not be able to put the power down anyhow. I ask a lot of customer if they want to up the boost, and most of them cannot stop spinning their new 285s in 1-3rd gear regardless of RPM, even when rolling into it( also regardless of pavement temperature).

Oh, I know. I'm not looking for more power.

I'm looking for something that's uncompromisingly better than stock on a single turbo, which is what the 7163 is except that it's too restrictive on the exhaust. Big wastegates would deal with that, but eh.

If a 7163 will put down like 200lb-ft at 2000rpm, and 300lb-ft at 4500rpm, I don't see the point in going bigger and would simply like to have it be as responsive as possible.

I get that the 8374 is popular because most people want more power. I want a set up that's like the stock twins, but without the dip, lighter, less vacuum lines, and so on.

Sequential twins were largely something that was does done just because they didn't have the computer modeling back then to do what the 7163 does. Modern cars have just as much response and good power bands with single turbos.

I don't think I'm overthinking things. It's long been known that rotaries pair best with a smaller compressor than turbine comparatively to a piston engine. The compressors sized relative to our exhaust flow are too large for what our engines reliably handle. That's pretty straight forward.
It's the same reason why you offer the TDX61/TDX57 and basically what I want but with the EFR design and tech.
And that doesn't make the 8374 bad. No, it's great. It's way better than the single turbos people were putting on their cars. It's the straight forward option if you don't want to choke the engine since it can handle the rotary's exhaust flow.

@zaque So which did you end up going for and why? Happy with it? I'm basically in the exact position that you're in, except 4 years down the line... I was kind of hoping there would be an even better solution by now; I wonder if it isn't @Turblown 's variable A/R housing??? Speaking of which, is that out yet, and are there any dynos for it yet?

Cheers

Could you elaborate on this? sorry, I'm still wrapping my head around tuning. Why is the 7670 always spooling and why would gas mileage be worse? Or am I misunderstanding -- spooling = boosting (since it spools so quickly), hence running richer? On an 8374, for example, you'd be in boost less (i.e. in low rpms) therefore not as much gas being pumped at low RPMs?

On a side note, what injectors and fuel pump are everyone running for these two turbos? Is there a big difference in required injectors for these two turbos?

Cheers guys!

Anytime a car is in boost, it will be run much richer, so yes worse gas mileage.

The 7670 can make 30 psi by 3k RPMS, its like what people think of when they want a supercharger.

On pump gas most people are using ID1050X x 4 with a 400 series walbro pump on the 7670, and ID1750X on the secondaries for the 8374( for most headroom down the line).

If the engine is ported you want to pick the 8374 over the 7670. If you NEED to have the option for low boost, you want to choose the 7670. If your goals are over 400rwhp, best to choose the 8374.

I'll try to answer some of your questions since I've had the turblown 8374 kit for a few years now. This is the only turbo I've ever ran except for the twins, so I don't have much to compare it against. That being said, I really can't imagine a better set up for the street.

My setup: 8374 iwg on the turblown cast manifold. Stock ports, oem seals, ID 1050 primaries and ID 1700 secondaries, 525 lph fuel pump on e85. I'm seeing 405 ft-lbs torque at 3800 rpm and 393 hp at 6000 rpm.

I went with this set up because I was looking for the most simple and reliable car possible with the option of more power later if I wanted. The 8374 can make the same power as a 7670 but at less psi which means less heat and stress. Yeah, the 7670 can spool up a couple hundred rpm faster, but the efr's spool so fast any way I don't see the benefit of limiting your future power potential in exchange for a couple hundred rpm in a street application.

It has been rock solid and well worth the money. The only problem I've been having that I don't hear a lot about is fuel slosh. The car rips so hard that if I have less than a 1/2 tank I'll get cut if I go full throttle 1-3 gear. I would recommend some type of sump even at my lowish power levels.
https://cimg4.ibsrv.net/gimg/www.rx7...1c6d7898a9.jpg
This is my fuel system maxed out on e85.

Fantastic -- thank you, @Turblown and @needspartsnow ! Very useful write up, needsparts -- your goals sound similar to mine, although we have a lot less open road here and lots of twisties.

I'm looking for somewhere in the region of ~320-350whp, but more importantly, reliability and daily streetability, which is why I'm leaning toward the 7670. (I'm installing it myself too, and so the simplicity of plumbing/wiring helps.)

When you say maxed out on e85, what do you mean? I'll be running straight 98 octane pump gas as that's the only realistic option on this side of the lake.

I'm planning on picking up the Xcessive lower intake manifold with 4 secondary injector ports. Does that mean I will need 4*500 (or 525) cc secondary injectors (instead of 2*1050cc)?

Love the tip about the fuel sump. I hope I don't run into those issues, but will keep an eye out for them when the turbo goes on!

@needspartsnow what other supporting mods did you go with?

Your power goals are in the region of the 7670. This kit will make that power around 10-14 psi( 325-350rwhp).

His fuel system is maxed out on the E85 ( needpartsnow).

Adey you will always want to run the primary injector ports + secondaries. So I would just run 4 x 1050X injectors( 2 primary/2 secondary). No real reason you need the Excessive LIM BTW, unless you just want a " cleaner " look.

Thanks @Turblown .
Yes, I'm just looking for the cleaner look at this point, and if I'm taking the oem LIM off to install the turbo kit, I figure why not?

After some more reading, I realize now you can block off the 2 additional secondary ports and just run 2 secondaries as normal.

Thanks for the input!

When I say my fuel system is maxed, I just mean my injectors are spraying the maximum amount of fuel they possibly can. That and the fuel pump is near it's limits. That's why it looks like my dyno sheet tapers off in the upper rpm. If I want to make more power I'll just simply have to put in bigger injectors and pump. Using e85 requires quite a bit more fuel than 93/98.

As far as supporting mods, I'm using an adaptronic
modular ecu, custom v-mount, dual 25 row oil coolers, oil catch/breather that I copied from a write up by user Damian on this forum, and ign1a coils in direct fire. I have some pictures on Instagram of the journey from stock to where I'm at now. IG: large_burnout

You might want to consider rethinking that some. The manifold has an injector port in each P/S port runner, plus the P injectors in the center iron. If your goal is to balance injector fuel flow to port air flow; and it should be, then if anything blocking the two primary ports and running larger injectors on the secondary ports is the effective strategy to consider.
.

@needspartsnow Thanks -- followed you!
What fuel pump and injectors are you running?

Anyone have the diameter of the compressor intake/outlet for the 7670 and the 8374? I'm going to have to make up some custom piping and may as well start getting my measurements...

ID 1050x and ID 1700x. Aem 525 lph pump. You won't need as much pump or injector running regular gas.

Good stuff - I'll be following Turblown's suggestions above on injectors and pump!
Cheers!

I made 320rwhp at 15psi on 98 ‘that’s Australia dyno power and fuel’ with my 7670 with incorrect injector times.