BLUE TII

iTrader: (9)

Why does the bw make so much less hp than the hybrid at similar boost levels? Is the 7076 the right turbo for 300-350rwhp goals as a dd trying to stay under 15psi and away from spray?

It boils down to aerodynamics which haven't changed and application which has changed.

The old T04B 60-1 is descended from a '50s aerodynamics compressor wheel for large displacement diesels running low boost- so reaches peak flow at low boost.

The EFRs are modern 2011 race turbos engineered for low displacement gasoline engines that can run high boost- so it reaches peak flow at high boost.

The 60-1 and 7670 are similar sized turbos with the EFR being a little smaller and flowing a little more due to materials/manufacturing techniques (FMW comperssor, BB, TiAl exhaust wheel, fine cast aluminum and stainless housings, etc).

To me the whole advantage to the EFR is its ability to flow at high boost..

This is good for racing because it takes high boost at low rpm to make torque.

This is bad for a street rotary because its a late '50s engine design that cannot tolerate high boost on pump gas like a modern engine design.

I had already maxed the 60-1 out on boost to where it stopped making power, so I went with the 7670.

Going from the maxed out 60-1 to the 7670 I only gained ~45hp peak, but it gained 170ftlb torque by 3,000rpm and 220ftlb torque by 3,500rpm.

Yes, more than tripled the torque at 3,000rpm!

So, best 300-350hp turbo on a rotary?
Depends on what you want.

For max reliability you want the largest, lowest boost turbo you can just get to spool enough for your peak power goal, but for performance you want the smallest, highest boost turbo possible.

BLUE TII

iTrader: (9)

Is the 7076 the right turbo for 300-350rwhp goals as a dd trying to stay under 15psi and away from spray?

I haven't tried every turbo, but between my 60-1 that peaked around 380rwhp @ 15psi and the 7670 that peaked ~330rwhp @ 15psi I would take the 7670 for a daily driver.

You get power NOW with it.

If we lived in the future where we could cobble together hybrid EFR turbos, I would take the 9180 0.83 T3 IWG hotside and put an old 60-1 compressor wheel in the 7670 compressor housing.

Dizzy117

Going from the maxed out 60-1 to the 7670 I only gained ~45hp peak, but it gained 170ftlb torque by 3,000rpm and 220ftlb torque by 3,500rpm.

Yes, more than tripled the torque at 3,000rpm!

^^ does it still have that effect on low boost(13-15psi) your pump gas tune?? Thanks I'm starting to get it a bit better now.

Dizzy117

Better driving? More power through the lower and mid rpm range?

Why would you want that combo? What would changing those parts do?

BLUE TII

iTrader: (9)

^^ does it still have that effect on low boost(13-15psi) your pump gas tune?? Thanks I'm starting to get it a bit better now.

The EFR 7670 will have more boost/torque earlier in the rpm at the lower boost compared to the 60-1 as well. What I really like is that you have the torque much more linear with the gas pedal.

Better driving? More power through the lower and mid rpm range?

Why would you want that combo? What would changing those parts do?

Yes, PEAK power only shows you a little of the cars character- I prefer to have more power where I will use it 90% of the time.

That hybrid EFR combo would provide good flow at low boost from the old '50s aerodynamics compressor for our '50s motor and have great EFR spool with the hotside sizing matching a street rotary very well.

Turblown

iTrader: (12)

You are leaving out a few things, the GTX3076R turbine wheel is a 60mm unit. The 7670 EFR is a 70mm. GTX3076R is a terrible choice for any rotary engine. The engine will be choking on that turbine past 5200`ish rpm at anything above 12 psi.

I made 302rwhp/227rwtq @ 8 psi on a stock 13BRE ( pump gas)
440/450rwhp @ 22psi.
Airwerks 7670 1.0 EWG

The EFR 7670 should do even better.

The IWG EFRs allow a very short manifold as one does not need to allow for space for wastegates and wastegate runners. This combined with the turbine technology blows every other turbo out of the water by a MILE in terms of boost response.

Generally when someone says street driven they are looking for something with a wide powerband, and as little lag as possible. For the 300 to 350rwhp range the IWG 7670 beats everything else again by a mile.

The engine does not care what psi it takes to make the power, an engine only cares about how much load it is in under. There is no difference in stress to an engine between 300rwhp @ 5 psi, and 300rwhp @ 20psi.

t-von

iTrader: (8)

I like the way you think! Why a street car would be built purely for top end makes zero since to me.

BLUE TII

iTrader: (9)

The engine does not care what psi it takes to make the power, an engine only cares about how much load it is in under. There is no difference in stress to an engine between 300rwhp @ 5 psi, and 300rwhp @ 20psi.

This is an interesting statement to examine.

First-
from the point of view of intake temps alone leading to auto-ignition of low octane pump gas it seems to make some sense at first blush as the rotor/piston is very inefficient at compressing the intake charge.

If you ram enough air in there for a 300hp bang with compression ratio alone the air/fuel charge just before ignition should be hotter than if you make a 300hp bang with any turbo operating anywhere on the map and a lower compression rotor.

This is the whole concept of the Miller Cycle where a (lower efficiency than turbo) positive displacement supercharger takes the job of compressing the intake charge from the piston with late intake closing for a more efficient engine (even with parasitic supercharger drive loss).

Reality intrudes-
However, we have engines with just a couple of compression ratios to choose from and thus in our case we can conclude the difference between an NA 300hp bang and a small turbo 300hp bang is due to factors other than rotor/piston compression efficiency versus turbo compressor efficiency since indeed that 300hp bang has been done at the same compression ratio on NA and FI rotaries at various times.

So basically, we have found a way to get the same number of air molecules into the intake stroke for an NA 300hp bang as we did with heated air from a turbo for a 300hp bang and then they are compressed by the SAME compression ratio rotor.

Now the air/fuel charge temps are higher and closer to auto-ignition on low octane gas for the turbo car.

Regarding rotary compression ratios-
One big difference between a piston engine and the rotary is when you raise the compression ratio on the rotary you greatly increase pumping losses of the combustion gasses through the rotor tub across the minor axis of the rotor housing.

This is why MFR cast race rotors were 9.4:1 CR for naturally aspirated applications and 7.5:1 CR for higher hp/rotor forced induction applications.

Race gas could easily have staved off detonation with higher CR rotors, but the higher CR would have increased pumping losses more than offsetting the power gains from increased CR and so decreased peak power.

BLUE TII

iTrader: (9)

An additional difference with 300hp bang in an NA or big turbo rotary versus a small turbo rotary has to do with our '67-'02 rotaries' huge exhaust bias overlap (and very late opening intake) and the fact the peripheral exhaust port NEVER CLOSES- it just switches flow on rotor faces.

Because of this the rotary is very sensitive to exhaust manifold pressure. When exhaust manifold pressure rises more exhaust heat is transferred to the engine internals and cooling systems (coolant & oil) through the always open exhaust port at a higher rate- just like a pressure cooker.

So now you have higher intake air temperatures from the turbo compressor, higher engine material temperatures, higher coolant temperatures (which will lead to higher spark plug temperature) and higher oil temperatures even at the same 300hp bang.

BLUE TII

iTrader: (9)

Finally, in the case of the non turbo or a big turbo versus a smaller turbo making the same single 300hp bang there is the fact that the smaller turbo car will be making more power average over time (area under the curve vs peak) and thus will have already been operating with a higher engine power/thermal load when that peak 300hp bang event is measured.

---------------------
All this "theory" aside, I have witnessed first hand how much more heat is produced by my rotary operating at 420hp @ 26psi on the EFR 7670 versus the old 380hp @ 14psi 60-1 when racing.

Running high boost continuously (fast/early spool and low enough power to maintain full boost) is a whole other world of thermal management on the rotary.

BLUE TII

iTrader: (9)

Generally when someone says street driven they are looking for something with a wide powerband, and as little lag as possible. For the 300 to 350rwhp range the IWG 7670 beats everything else again by a mile.

I agree with this!

BLUE TII

iTrader: (9)

I like the way you think! Why a street car would be built purely for top end makes zero since to me.

I learned through experience.

I made a version of the peak power quest in a street car mistake on my first incarnation of the TII back in 2001.

I did everything I could think of for top end power with some expense to low end power trying to get 300hp out of a stock based turbo.

I ended up overshooting and getting 400hp out of a stock based turbo (which turned out was a lot for a noob in a 2,500lb FC) along with some pretty hairy driveability.

Going from 50-400hp abruptly as the engine revs shocks the tires into spinning pretty easily and with big ports/overlap the throttle input didn't really affect power output much once the engine was in the powerband. It was pretty all or nothing.

I revised my porting to a small street port and it tamed the beast tremendously without affecting peak power nearly as much as I had thought it would.

Next step was the smaller, better spooling EFR 7670 turbo which bumped the power back up (with higher boost), but again helped tremendously with driveability.

More power actually makes the car easier to drive when "more power" means more power under the curve.

My new 400hp/400tq set up is much easier to drive than my old 400hp/300tq set up and much faster as well.

Enigmatic

Well we shall have more results soon. Just got it back from thermal coating along with the rest of the v-mount set up.

BLUE TII

iTrader: (9)

That looks great!

Please put a link here to your thread when you start it so its easy for people to find all the EFR 7670 info they can (you can put your results here if you want as well ofc, but most people like there own thread.)

rx7 SE

iTrader: (5)

Good info Blue TII

Haraise

Any idea what kind of power the 7670 would get on 91 octane? Thanks for the informative thread.

BLUE TII

iTrader: (9)

Haraise Any idea what kind of power the 7670 would get on 91 octane? Thanks for the informative thread.

My EFR 7670 only made ~315rwhp dynojet on 12psi creeping to 13psi (wastegate spring) if that helps answer your question. That is how I ran it on 91 octane.

Of course it had full boost (13psi) at 2,500rpm!

Even on low boost the EFR 7670 had a BROAD power band and I bet it was still faster than my old 60-1 (340@12psi, 380@14psi) at the same boost.

Now if we could get an EFR 7670 made with the old 60-1 compressor section for pump gas only rotaries we would have a real winner.

But then the bigger EFR 8374 is a nice choice for low boost pump gas rotaries.

Haraise

Wow, you're really not making the choice easy for BNR Stage 3 in sequential vs 7670! Have a dyno at 91?

lOOkatme

iTrader: (19)

I so need to buy this turbo. Run it at around 16-18PSI with water injection. Pressure ratio of 2.53 for up here going as high as 2.8-3.0 in the mountains at 18PSI.

Monkman33

iTrader: (28)

I had originally gone with bnrs but sold them when i needed money. Had intended to get them again.

However, the EFR7670 was too tempting and my main justification was this:

No transition or associated complexity of twins.

Haraise

Both very good reasons, not to mention weight and thermal mass. What header did you go with?

Monkman33

iTrader: (28)

Turblown. Short runner.

.92 a/r efr 7670 Internal Wastegate.

Haraise

I love how low and back the Turblown mounts, but have you seen that you're giving up much power to the Full Race?

Monkman33

iTrader: (28)

I dont. Please fill me in.

Haraise

I'm sorry, that was a question. Poorly worded. I meant 'have you seen any indication you're giving much up to the seemingly more power optimized full race header?'