D-Rob

As some of you know the twin scroll EFR 8374's have finally begun shipping, and a customer of mine was one of the first to receive one of these puppy's.

Yesterday, he made the long trip from Boston (7 hours each way) for some welding, engine break-in, and finally pump gas and C16 tuning.

His previous mid-pipe was constructed by what looked to be a blind baby with a MIG welder, and was thrashed up pretty well by the road. Below is the old versus new, because there's no use trying to make a bunch of power with a fancy new turbo through a crushed exhaust.



The turbo sitting nice and comfy in the engine bay of the RSX. It's strange to see a Full-Race divided sidewinder without gates on it!



Finally, the car on the dyno.



The engine was fresh (we assembled the engine over the summer, Benson-sleeved 87mm/Wiseco 9.8:1, Manley rods, etc...), so we did a small engine break-in on the dyno, changed the oil, and went for the lowest boost pressure setting available with the actuator on the turbo.

I was amazing to find that the internal gate was able to hold boost wonderfully at low pressures, with nothing but a small increase in boost over engine speed.



Next was to turn the boost up with the integrated solenoid. Upon applying duty cycle, I found that boost did not significantly move up until about the 50% or so range with this actuator. We also saw that while the internal gate does a great job bypassing exhaust flow to keep boost down, it still carries the same characteristics as most internally-gated turbos, in the way that once pressure goes up, it has a tendency to spike, then level, and ultimately fall off. That being said, I was able to make about 20psi in the middle, and 17.5psi up top with the first actuator, with controller duty cycle at 90% or so from 7,000 RPM and higher.

Below is a plot of the boost pressures on pump fuel. It is a comparison of the "high" setting, and the "low" setting after some preload adjustment.



With that said, the final 93 octane numbers were 508whp / 410wtq @ 20psi falling to 17.5psi up top. Because of this boost taper, the torque curve is a tad wavey up top. The engine's torque curve holds on, while boost drops. The dotted line shows wastegate pressure with a slight 1-2psi creep, so the curve looks normal.



After learning of the gate's tendency to drop boost pressure, a slightly stiffer actuator was installed while the 93 octane was pumped out, and C16 filled in its place.

The new actuator's lowest setting was around 14-15psi, and with that we were able to make about 25psi up top with 90% solenoid duty. In the middle, there was enough to make 28psi or so, but for the sake of consistency, we tuned to a flattened out 25psi.

At 25psi, we ended with 640whp / 480wtq.


As with the other gate, we saw a spike in pressure on spool-up, a slight drop, and then stabilize. The spike in torque on spool up can be seen on the pressure plot below.



Here is a comparison of the final C16 plots versus the final 93 octane.



Over-all, the turbo seemed to make similar power to a 6262, but spooled much like a GT3076R on this engine.

Here are a couple comparisons versus similar turbochargers:

EFR 8374 versus GT3582R


EFR 8374 versus T3/T67 H.O. (car with T67 is 11:1, on E85 even)


The EFR 8374 is hands-down one of the most responsive turbochargers of this size that I have dealt with.

Thanks for taking a look, just thought I would share the results. :thumbsup:

- Derek

Muckman

iTrader: (2)

Very impressive turbo. I had two comments - The 90% duty cycle required for 2x spring boost is disapointing. I guess I shouldn't expect much more from an internal gate? The 25psi spike is ridiculous. Any thoughts on how that could be smoothed out?

92TypeR

Is this the 0.83 or 0.95 A/R IWG TS Turbine Housing?

It looks like power is still climbing, was there any pulls performed to a higher engine speed?

Did you do any street drives after the tune? If so, how did the turbo perform on the street? Transients, tip-in, etc?

LightningTeg

Looks great. Very impressive.

I had the same issues with my internal gate on my GT28r. Spiking initially (hump) then loosing boost up top.

.RTErnie

Great results. Thanks for sharing.

Did you try running a restrictor on the inlet side of the EBC solenoid? It will linearize the boost change to WGDC relationship... and allow higher PRs.

Gunmetal_B20_Hatch

iTrader: (9)

great testing... Would have like to see a few more comparisons of boost levels from similar turbochargers(namely a billet 6262).

Also, is the EFR series BB or journal bearing?

TheShodan

iTrader: (14)

THe exhaust wheel alone from the 8374 would have made it more similar to a 6265, not the 6262 due to the difference in exhaust wheel.

D-Rob

The spike was only really prominent when we used the solenoid over 50-60% or so.

This has the .96 AR housing on it.

We did not perform any pulls to a higher engine speed. Customer didn't want to take it any higher last night. He will be returning in a month or two with a new wastegate actuator to see 30-32psi, and I will rev it more then.

The customer took the car out last evening (at 1:30 AM after driving back to MA), and reports that it is absolutely a dream in the tip-in response department, and transient response on gear changes.

Didn't even think of it. I will tell you that I don't have a lot of customer's using internal gate turbos over a large range of pressures like this one was operating under, so I will be honest when I say I don't know that trick!

It is a ball bearing turbocharger.

- Derek

area522010

Bump for nicely tuned honda from Mass. alot of cars i see next year at NED

92TypeR

That was going to be my next question - Any plans on running this compressor into the sweet spot of the efficiency map? I'd say 33-35psi is just about where you want to be with this turbo.

Glad to hear! It would be great to see some logs of street driving. K-pro?

TheShodan

iTrader: (14)

Specifically ceramic ball-bearings in their cartridge. (As does Precision and Turbonetics). Garrett uses steel ball-bearings in their cartridges

Tony the Tiger

There is almost no replacement for diaphragm size when it comes to wastegates. The larger the diaphragm with larger surface area, then the same amount of boost can now provide a stronger "push" onto the wastegate. More push means it can control boost properly with a very stiff spring, and the spring ultimately is what determines how much boost it can hold.

With the internal WG units, the size is what limits on what they can do. They can only prevent it from spiking by enlarging the flapper size and so forth, or change the actuator arm / swing radius and length of travel.

I know the internal WG built onto the turbo is a nice convenient feature, but I would go with an external for sure IMO with these new EFR turbos.

TheShodan

iTrader: (14)

Yeah, even Full-Race uses a twin external gate system for their EFR S2000 kits.