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Initial EFR 7670 dyno results

Old 11-02-14, 07:43 PM
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Blue TII, what kind of fuel mileage are you getting on the street? My Holset VGT spools very easily under partial throttle and hurts economy but still doesn't spool as fast as your EFR.
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Old 11-02-14, 09:32 PM
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It was ~13-17mpg in regular street driving.

It is loud so on the street I am always driving around under 2,000rpm in 4th and 5th to keep the noise down.

On the one long road trip it did it was only 18mpg.

My old less responsive turbo set up got the same around town mileage, but in the low/mid 20s mpg on the same road trip, so I would say I am was having the same issue with a responsive turbo and cruising mpg.

I have the super short JDM 5th so @ 65-75 cruise it is at 3-4,000rpm and jumps into boost very easily.

Still cheaper than towing?

Have you tried putting in a switch for cruising that will open your VGT all the way up? That should really help EGTs and MPG.
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Old 11-03-14, 06:43 AM
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That's pretty similar to what I average. I get 15mpg +/-1 almost every tank, but my mileage is almost exclusively backroads and state highways with 45-55mph speed limits in the hills of Connecticut.

Best I've averaged was 17 with 50% interstate, but since I never drive on the interstate, my tune in that rpm/load is lousy and is usually no more than 8" vacuum on flat and 2-3psi up any kind of grade.

My cruise control actually work but will make WG boost if I let it lol. The VGT on my turbo is air actuated with a single port air cylinder. It's spring return and boost open. Vacuum assists spring in closing too.

It's very quiet under idle and cruise. A bit stock exhaust with a bit of drone from the 4" DP. Every rotary guy I've shown it to has made some kind of comment about how quiet it is. Only problem is the spring isn't strong enough to fight back pressure and opens prematurely, spool drags on a little longer than it should.

I see 12psi by around 3800 with a ebay undivided manifold and a $250 60mm used turbo. Adding a solenoid to isolate the air cylinder from below peak boost would help. It could be better and it likely will before I give up. Sorry for the thread hijack!
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Old 11-03-14, 08:00 AM
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If I baby mine, and we have thinner air, I can get 24MPG with my 14.7 to 15.2 AFR tune in the cruise cells. GT3574R on mine.
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Old 11-03-14, 08:51 PM
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Still think this turbo is not a good match for rotary, just too much left on the table for mid and high range.

I'd bet that a car with same mods except an EFR 8374 will be faster in all situations, auto-x, road race, and drag. Anywhere.

I'd love to hear Turblown, Howard, or Full-race Geoff's take.
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Old 11-04-14, 12:33 PM
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I don't know about that.
I hope these turbos become common enough on rotaries we get some direct comparisons though.

From what Borg Warner says themselves it is certainly possible the larger exhaust wheel on the 8374 makes up for the added compressor work required. BW says the Titanium Aluminide exhaust wheel shows the most improvement to spool in the larger sizes.

Still, it appears the 8374 is on the verge of surge at low rpm, and looking at the maps if you can get the 7670 close to the surgeline at low rpm as well- it will have a clear advantage in low rpm power over the 8474.

Even with the rotary this might require a quickspool valve. I propose the stock FD sequential manifold coupled with a divided turbo manifold to decrease runner volume and boost exhaust velocity on the low rpm.

Also, always be skeptical looking at dyno results.
If a DynoDynamics shows the car only revving to 7,000rpm it is possible they have the drivetrain ratio off (DD does not have a tach input) so results are skewed 1,000rpm off (showing a false early spool).

I could easily whip out a chart of the 7670 making its peak torque at 3,000rpm instead of 4,000rpm by accident or on purpose with the DD.
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Old 11-04-14, 12:34 PM
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The 7670 is quite responsive. In that kart track video I am rolling on the throttle out of corners and you can still hear how quickly it hits 26psi (when wastegate is open).

In the turns where I over rotate and have to countersteer and jump on the gas to correct instead or rolling on you can hear the wastegate open almost instantly.
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Old 11-04-14, 12:45 PM
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Wow, I just watched the kart track vid you post earlier Blue TII. That is exactly what you want for a track car/turbo. The only downside I think is how much boost is required to make that power.
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Old 11-04-14, 01:57 PM
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Originally Posted by rx7 SE View Post
Wow, I just watched the kart track vid you post earlier Blue TII. That is exactly what you want for a track car/turbo. The only downside I think is how much boost is required to make that power.
I have always wondered. Can this EFR turbo be run without water injection in the 20-25PSI range? The turbo is efficient in this range so air temps shouldn't be bad. I have always been confused by the rule of thumb. The unspoken about rule is not to run more than 14-15PSI boost at sea level. The reason to run a higher octane fuel is to resist detonation. Detation is a function of compressing a certain volume of air at X temp to whatever compression ratio, which increases the temperature during compression which could lead to detonation/knock. No where in this equation does it talk about boost pressure. Its volume of air, temperature of air, and compression ratio. So wouldn't larger turbos at less boost be at the same risk of smaller turbo's at higher boost level given the same air temps? If this EFR turbo is efficient at 20's PSI, shouldn't the air temps be fine?

Maybe I am using the wrong thought process, equation in my head?
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Old 11-04-14, 02:43 PM
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Originally Posted by lOOkatme View Post
I have always wondered. Can this EFR turbo be run without water injection in the 20-25PSI range? The turbo is efficient in this range so air temps shouldn't be bad. I have always been confused by the rule of thumb. The unspoken about rule is not to run more than 14-15PSI boost at sea level. The reason to run a higher octane fuel is to resist detonation. Detation is a function of compressing a certain volume of air at X temp to whatever compression ratio, which increases the temperature during compression which could lead to detonation/knock. No where in this equation does it talk about boost pressure. Its volume of air, temperature of air, and compression ratio. So wouldn't larger turbos at less boost be at the same risk of smaller turbo's at higher boost level given the same air temps? If this EFR turbo is efficient at 20's PSI, shouldn't the air temps be fine?

Maybe I am using the wrong thought process, equation in my head?
As always you need to be careful about trying to simplify this problem.

Air temperature does play a part in detonation, but probably more so does the mass of the air/fuel charge in the combustion chamber. Squeezing more and more in raises the combustion pressure and increases the chances for detonation. This can be offset in varying degrees by increasing the octane, reducing the timing, or reducing the charge air temperature.

Without running really high octane fuel, ie race gas or methanol, you need to find the best balance for any given setup.
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Old 11-04-14, 03:02 PM
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Originally Posted by Vicoor View Post
As always you need to be careful about trying to simplify this problem.

Air temperature does play a part in detonation, but probably more so does the mass of the air/fuel charge in the combustion chamber. Squeezing more and more in raises the combustion pressure and increases the chances for detonation. This can be offset in varying degrees by increasing the octane, reducing the timing, or reducing the charge air temperature.

Without running really high octane fuel, ie race gas or methanol, you need to find the best balance for any given setup.
Combustion pressure is directly related to WHP correct?

So Why are people focusing on the boost pressure and not the WHP?

doesn't larger turbo's move more CFM per given boost pressure, hence larger turbo's will have a higher chance of detonating at lower boost pressure and vice versa for smaller turbo's? As long as you are in an efficient range of the turbo which compresses the air efficiently and keeps the temperature manageable, wouldn't combustion pressure be your limiting factor and by no means directly related to boost pressure?
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Old 11-04-14, 03:09 PM
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I have always wondered. Can this EFR turbo be run without water injection in the 20-25PSI range? The turbo is efficient in this range so air temps shouldn't be bad.

I wouldn't try. Even if the compressor was 100% efficient (means it follows thermodynamic principals 100%, not that it doesn't heat the air) it would still be heating the air more with the increase in boost and as mentioned above you have a higher charge density and therefore higher effective compression ratio so the air/fuel charge is more volatile.

I tuned it on 104 octane and then raced on 110 or 116 octane depending on what was available.

I can tell you, running 26psi around that kart track during those short 3 minute sprints made everything in my engine bay hotter than it has ever been or that I have ever felt (even in a stock sequential FD).
My intake manifold was smoking from burning off years of incidental oil (finger prints, WD40 residue from cleaning it, etc) and my whole engine bay smelled of fiberglass resin (from the CF pieces in the engine bay).

Oil temps, coolant temps and the coldside of the intercooler were not overly affected by this heat, but the SS manifold/exhaust housing and turbo hot side charge pipes/IC were spewing heat.

That is exactly what you want for a track car/turbo. The only downside I think is how much boost is required to make that power.

I would say it is good for auto-x and sprints, but definitely not tracking. See the thermal management issues above when running high boost for extended periods of time.
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Old 11-04-14, 08:31 PM
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Originally Posted by BLUE TII View Post

Also, always be skeptical looking at dyno results.
If a DynoDynamics shows the car only revving to 7,000rpm it is possible they have the drivetrain ratio off (DD does not have a tach input) so results are skewed 1,000rpm off (showing a false early spool).

I could easily whip out a chart of the 7670 making its peak torque at 3,000rpm instead of 4,000rpm by accident or on purpose with the DD.
In case this is aimed at our results, I backed them up on 3 different dynos in town before I posted anything. I also double checked everything was setup correctly on all of them. Hell I didn't even post the 515rwhp dynojet graph.

I am excited to show you guys what this system makes this spring as I believe I have sorted out the high RPM misfire on that car, and we will get to see the true results of the 8374 at high boost. The top end power will be incredible...
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Old 11-04-14, 09:01 PM
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Also, always be skeptical looking at dyno results.
If a DynoDynamics shows the car only revving to 7,000rpm it is possible they have the drivetrain ratio off (DD does not have a tach input) so results are skewed 1,000rpm off (showing a false early spool).

I could easily whip out a chart of the 7670 making its peak torque at 3,000rpm instead of 4,000rpm by accident or on purpose with the DD.


This is directed toward you- your Dyno Dynamics chart only goes to 7,400rpm.

This is directed to me- my Dyno Dynamics chart only goes to 7,500rpm.

Additionally, my DynoJet chart is shown, but I used an Excel file to recreate it in order to show torque. That could easily be manipulated.

I used the Dyno Dynamics rpm as an example as that is the dyno I have the most experience on and have noted mode, air temp probe placement, ramp rate and rpm synch, and strapping are all factors that influence the graph.

What we are trying to measure (turbo spool) is most influenced by ramp rate and can also be manipulated as the rpm must be manually synched.

I also did my best to represent correct information, but I am warning people to be skeptical looking at dyno results and trying to compare turbos. There are too many variables.

What we need is more videos of the actual vehicle performance to make direct comparisons.
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Old 11-04-14, 09:20 PM
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Here is a 1,500rpm to 7,500rpm 4th gear pull.

Goes pretty well from 1,500-3,000rpm even in 4th compared to most single turbos.

You can see the acceleration is pretty flat form 6,000-7,500rpm though as it is done gaining HP.


https://www.youtube.com/watch?v=97LK...ature=youtu.be
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Old 11-05-14, 08:26 AM
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Originally Posted by BLUE TII View Post
Also, always be skeptical looking at dyno results.
If a DynoDynamics shows the car only revving to 7,000rpm it is possible they have the drivetrain ratio off (DD does not have a tach input) so results are skewed 1,000rpm off (showing a false early spool).

I could easily whip out a chart of the 7670 making its peak torque at 3,000rpm instead of 4,000rpm by accident or on purpose with the DD.

This is directed toward you- your Dyno Dynamics chart only goes to 7,400rpm.

This is directed to me- my Dyno Dynamics chart only goes to 7,500rpm.

Additionally, my DynoJet chart is shown, but I used an Excel file to recreate it in order to show torque. That could easily be manipulated.

I used the Dyno Dynamics rpm as an example as that is the dyno I have the most experience on and have noted mode, air temp probe placement, ramp rate and rpm synch, and strapping are all factors that influence the graph.

What we are trying to measure (turbo spool) is most influenced by ramp rate and can also be manipulated as the rpm must be manually synched.

I also did my best to represent correct information, but I am warning people to be skeptical looking at dyno results and trying to compare turbos. There are too many variables.

What we need is more videos of the actual vehicle performance to make direct comparisons.
I completely agree with this
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Old 11-05-14, 09:18 AM
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Originally Posted by lOOkatme View Post
Combustion pressure is directly related to WHP correct?
More precisely it is directly related to Torque output. Horsepower is the work that is done with the torque.

So Why are people focusing on the boost pressure and not the WHP?
The people who actually know what they are doing focus entirely on output.

doesn't larger turbo's move more CFM per given boost pressure, hence larger turbo's will have a higher chance of detonating at lower boost pressure and vice versa for smaller turbo's? As long as you are in an efficient range of the turbo which compresses the air efficiently and keeps the temperature manageable, wouldn't combustion pressure be your limiting factor and by no means directly related to boost pressure?
Me thinks your getting it!
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Old 01-29-15, 12:44 AM
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bump for vids
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Old 01-29-15, 02:06 AM
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Not really any more vids. Here are some from the only time I took it to 1/4 mile. As you will see, I am no drag racer, but the little auto-x turbo is pretty quick.

Completely bogged the launch, but the turbo recovers very well.

Sleeping at the light.

I will concentrate on my FD this coming season and part out the FC as it was too slow at the hillclimb and enduro events I like to do. Just too limited a chassis.

This FC drivetrain might find its way into my RX-8 though! I loved the powerband/driveability.
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Old 01-29-15, 08:07 AM
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Sad to hear that you're moving on from the FC chassis, as I'm just starting my FC track car build lol. I can understand though because despite the great weight distribution, the handling is poo in comparison to any modern car...especially the FD, miata, and rx8.

Hmm, makes me want to reconsider an s2k track car...
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Old 01-29-15, 11:56 AM
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Do you have any dyno results at 13-15 psi? Seems like this is a race gas only turbo based on the pressures needed to get power.
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Old 01-29-15, 12:30 PM
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Sad to hear that you're moving on from the FC chassis, as I'm just starting my FC track car build lol. I can understand though because despite the great weight distribution, the handling is poo in comparison to any modern car...especially the FD, miata, and rx8.

Hmm, makes me want to reconsider an s2k track car...


Actually, weight distribution is one of my complaints in the FCs handling. My TII is 2,5xxLbs with 52% rear weight distribution and a large chunk of that weight is right over the rear wheels. It makes it handle a lot like a mid engine car which I dislike. Vague steering feel/turn in and understeer on the throttle.

If I enter a turn I am not sure of the radius I have to slow down to plant the front end in case I have to decrease the radius of trajectory.
Perhaps a 1.5 or 2 way clutch type rear end instead of the Torsen would help in this regard as I could be sure of throttle lift oversteer at any speed (though with stock clutch type this certainly aggravated the throttle on understeer).

Conversely, if you can see your way through the turn its great as you can get on the throttle early and understeer your way off the apex full throttle.

My biggest complaint is the FCs strut front end though. You have to run lots of static negative camber and spring rate up front to work around its cornering limitations which leads to braking limitations.

I only have experience racing my friends AP1 S2000 and though I love how telepathic it is to corrections, I feel its a bit twitchy in needing them as well.

I prefer the RX-8 to the S2000 in my limited experience. The 8 has incredible maneuverability despite its settled feeling- and the 8 can actually fit wheel and tire width unlike S2000 that is as limited as the FC (my final major complaint of the FC chassis).
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Old 01-29-15, 12:47 PM
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Do you have any dyno results at 13-15 psi? Seems like this is a race gas only turbo based on the pressures needed to get power.

Yes, the EFR 7670 really shines on race gas boost levels- though it is a nice driver on pump gas- very comparable to the stock sequential twins on an FD above 2,000rpm and not too much worse below that.

I did dyno on wastegate (13psi) I will see if I can get that. The peak power was much lower than my old 60-1 since modern turbos are designed to flow at high boost and old turbos were designed to flow at low boost.

The EFR 7670 was only 275hp on the Dyno Dynamics @ 13psi (est. ~320hp Dynojet) whereas my 60-1 was 295hp @ 11psi Dyno Dynamics, but maxed its flow at 330hp @ 18psi Dyno Dynamics (confirmed 340hp Dynojet @12psi/380hp @14psi Dynojet).

Also @ 13psi the EFR 7670 low rpm torque is only like a sequential twin FD, it doesn't have that incredible torque 3-3,500rpm that comes from high boost.
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Old 01-29-15, 01:07 PM
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Originally Posted by BLUE TII View Post
Sad to hear that you're moving on from the FC chassis, as I'm just starting my FC track car build lol. I can understand though because despite the great weight distribution, the handling is poo in comparison to any modern car...especially the FD, miata, and rx8.

Hmm, makes me want to reconsider an s2k track car...


Actually, weight distribution is one of my complaints in the FCs handling. My TII is 2,5xxLbs with 52% rear weight distribution and a large chunk of that weight is right over the rear wheels. It makes it handle a lot like a mid engine car which I dislike. Vague steering feel/turn in and understeer on the throttle.

If I enter a turn I am not sure of the radius I have to slow down to plant the front end in case I have to decrease the radius of trajectory.
Perhaps a 1.5 or 2 way clutch type rear end instead of the Torsen would help in this regard as I could be sure of throttle lift oversteer at any speed (though with stock clutch type this certainly aggravated the throttle on understeer).

Conversely, if you can see your way through the turn its great as you can get on the throttle early and understeer your way off the apex full throttle.

My biggest complaint is the FCs strut front end though. You have to run lots of static negative camber and spring rate up front to work around its cornering limitations which leads to braking limitations.

I only have experience racing my friends AP1 S2000 and though I love how telepathic it is to corrections, I feel its a bit twitchy in needing them as well.

I prefer the RX-8 to the S2000 in my limited experience. The 8 has incredible maneuverability despite its settled feeling- and the 8 can actually fit wheel and tire width unlike S2000 that is as limited as the FC (my final major complaint of the FC chassis).
Would you choose the rx8 over a NB or NC miata? I would think they would probably run similar lap times given the same power to weight ratio?
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Old 01-29-15, 03:05 PM
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Would you choose the rx8 over a NB or NC miata? I would think they would probably run similar lap times given the same power to weight ratio?

I prefer the RX-8 over the NA/NB Miatas I have raced, but I don't have experience with the "mini RX-8" NC Miata.

The Miata are excellent at auto-x, but I still prefer the long wheelbase RX-8 dynamics- especially if future power increase is in the cards.

The RX-8 is a very stable chassis that happens to be amazingly nimble, able to maintain very high cornering speeds, fit lots of wheel/tire (I put my 18x11 +45 w/295s from my FD right on my stock stock RX-8), so I feel adding power will detract very little from its handling performance. Substantial roll/pull/camber should net you 18x12 +30 w/ 315.

In contrast the shorter wheelbase Miata suffers in braking as it pitches forward/over excessively. With stock power it is not a terrible problem (but something I notice) as you don't have to brake much, but as you increase power/speeds the shorter wheelbase chassis will pitch forward/back more taking more time to settle the chassis before you can turn in/get on the gas. You are more limited in finding/fitting big wheel/tire that will help with the added power/speeds as well. NB roll/pull/camber fan fit 15x10 w/ 275 slicks for the track, but 15x9 w/ 235 is biggest available for street. NC substantial roll/pull/camber can manage 17x10 w/ 255 for street/track.

Practicality, that is something I am really starting to fall in love with the RX-8.

You can fit all four of those 18x11 295s in the car with you (and have an empty trunk to pack) if you don't want to drive on them to the track. You can fit 4 adults in the car. With the pillarless 4 doors you can fit huge things in the car by reclining the passenger seat for parts/dump runs.

The only let down for me on the RX-8 is the 13B-MSP engine power/gas mileage, but 13B-REW swaps are becoming more common and easier- which ends up being a plus for me over the Miata as rotary Miata is a harder swap. Get a blown up RX-8 and REW swap it.

That sounds like some cheap fun right there!
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