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Initial EFR 7670 dyno results

Old 10-12-16, 05:02 PM
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Originally Posted by BLUE TII View Post
The smaller 7670 compressor is spinning faster to produce 53lbs/hr at 64% efficiency (~20psi) and the larger 8374 compressor is spinning slower to produce 53lbs/hr at 75% efficiency (~20psi).
11% denser air charge on the larger compressor at the same CFM and same boost pressure, so it makes more power.

Then you also have total system heat soak.

The smaller turbo spools quicker and sooner and at lower vehicle mph and in addition has lower efficiency at high CFM output.
Great, but this all leads to much more heat into the intercooler, radiator, oil cooler, engine block, etc over time which lowers peak output in actual use over a laggier turbo that puts less heat into the system.
But basically you're saying is that the air temps are going to be higher due to the friction of the compressor against the air spinning faster to produce a given amount of airflow?
Sure but, the air cools when it expands more greatly out from the smaller outlet, and an efficient a2w intercooler should make that not matter, shouldn't it?

I don't see how it adds more heat to the engine block UNLESS you don't have large enough of a wastegate.

And another thing you're saying is that a smaller turbo is less efficient, so for every 1hp it drains from the engine due to back pressure, it will output less CFM. Or more intuitively, to produce 500 CFM at a given RPM will drain more horsepower from the engine and appear as less gains, even assume optimal wastegating since the compressor is simply less efficient.

Also, when I plug in and look at the 7163 and 8374, I don't see a 64% to 75% efficiency difference. I see like 68-73% for the 7163 EXCEPT at the very very low end where it's 60%.
That's really about the same on average! Discounting 2000RPM where the 8374 doesn't make any power.
Maybe the numbers I put in aren't that great: http://tinyurl.com/hpb63p4

Last edited by zaque; 10-12-16 at 05:15 PM.
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Old 10-12-16, 06:11 PM
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VE is volumetric efficiency.

Volumetric efficiency (VE) in an internal combustion engine design refers to the efficiency with which the engine can move the charge of fuel and air into and out of the cylinders.

In our case rotary chamber.

What you will see in real life is lower boost pressures of a smaller turbo will produce close to the same results of a larger turbo in terms of WHP, (your turbine wheel difference doesn't matter at lower flow rates) means you haven't hit the threshold level where the larger turbo becomes more valuable so to speak. So you run the smaller turbo to get more area under the curve since it will boost quicker. At some boost pressure the VE of the larger turbo and perhaps the compressor efficiency make more power at a certain boost level and on up. so the larger turbo might be more favorable to run since more oxygen makes it into the engine because of higher VE and colder temperatures due to compressor design and size given a certain size engine (the backpressure of the larger turbine wheel matters over says 15PSI, where the smaller turbine wheel and smaller compressor become an issue due to efficiency).

The smaller turbo runs hotter as it has more boost at lower rpms since it makes more power down low, it also has less VE which retains heat more. As boost pressure increases and the turbo runs at a less efficient region on its compressor map it will emit hotter air. You then need to rely on heat exchangers to suck out the heat.


Power is heat. the more power the more heat.

A very robust design would be to get as low as ambient temp into the turbo as efficiently as possible to keep the lowest pressure ratio drop. you don't need to rely on the heat exchanger to lower the air as much, but it will suck out heat as well, the lower the intake temps the lower the chance for detonation which means you can also push it harder. so large air filters, velocity stack, big exhaust, straight piping, high # of rows with small width and small volume of piping for the best design, smooth transitions where possible everywhere you can.
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Old 10-13-16, 12:37 PM
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Right, but that's in regards to how much air is crammed into the engine and the effective compression ratio you have.

If you're measuring the psi of the air leaving the turbo, that's a fairly useless number when it comes to tuning the engine, no...? The pressure and temps are going to be different after they leave the intercooler and are at a more comparable spot between set ups.

But the engine doesn't care at what pressure and temp air left the compressor. It cares what temperature it is and with how much it's flowing into the engine after a lot of piping later.

Yes, 50lb/min of air at 20psi is going to be hotter than 50lb/min at 15psi, but the 20psi air is going to expand more in the same given amount of piping down from it and cool down and roughly reach the same pressure and temp while the flow rate is the same... Then they'll compress back down into the intake headers to the same psi, whatever that is given the flow rate into that volume.
Other than that, well yeah we all know you want air temps going into the engine that are barely above ambient, but I'm still not seeing how a smaller compressor necessarily means hotter temps there?

Last edited by zaque; 10-13-16 at 12:47 PM.
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Old 10-14-16, 02:52 AM
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Originally Posted by zaque View Post
Right, but that's in regards to how much air is crammed into the engine and the effective compression ratio you have.

If you're measuring the psi of the air leaving the turbo, that's a fairly useless number when it comes to tuning the engine, no...? The pressure and temps are going to be different after they leave the intercooler and are at a more comparable spot between set ups.

But the engine doesn't care at what pressure and temp air left the compressor. It cares what temperature it is and with how much it's flowing into the engine after a lot of piping later.

Yes, 50lb/min of air at 20psi is going to be hotter than 50lb/min at 15psi, but the 20psi air is going to expand more in the same given amount of piping down from it and cool down and roughly reach the same pressure and temp while the flow rate is the same... Then they'll compress back down into the intake headers to the same psi, whatever that is given the flow rate into that volume.
Other than that, well yeah we all know you want air temps going into the engine that are barely above ambient, but I'm still not seeing how a smaller compressor necessarily means hotter temps there?
Some people think it don't be like it is. But it do.
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Old 10-14-16, 02:00 PM
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Originally Posted by zaque View Post
Right, but that's in regards to how much air is crammed into the engine and the effective compression ratio you have.

If you're measuring the psi of the air leaving the turbo, that's a fairly useless number when it comes to tuning the engine, no...? The pressure and temps are going to be different after they leave the intercooler and are at a more comparable spot between set ups.

But the engine doesn't care at what pressure and temp air left the compressor. It cares what temperature it is and with how much it's flowing into the engine after a lot of piping later.

Yes, 50lb/min of air at 20psi is going to be hotter than 50lb/min at 15psi, but the 20psi air is going to expand more in the same given amount of piping down from it and cool down and roughly reach the same pressure and temp while the flow rate is the same... Then they'll compress back down into the intake headers to the same psi, whatever that is given the flow rate into that volume.
Other than that, well yeah we all know you want air temps going into the engine that are barely above ambient, but I'm still not seeing how a smaller compressor necessarily means hotter temps there?


When I tune cars with the powerFC I have noticed that the largest difference in air temps comes from running the turbo's in their efficiency range with the intake filter sucking in ambient air.


The ambient air intake is more important than an intercooler as the intercooler is a really inefficient way to suck out heat, it's better to never get the heat into the system. ducting also does wonders for heat exchangers.


The worst set ups I have tuned have been stock twins being pushed to 13-15PSI at altitude with big FMIC and intakes that suck in hot engine air. Their air temps are always 50-60C. My single EFR has air temps measuring at 0-2C over ambient with ducted V-mount, 3.5" downpipe to 3" midpipe/CB, 4" intake with huge filter sucking in ambient air.


We have run small 7"x9" intercoolers that is 3.5" thick and a large intake on a garret T3 turbo (T60/61 or something) and funneled cold air into the intake of that and ran 0-5C over ambient temps. it was a side mount intercooler set up.


Before this he had the stock twins with a stock intercooler and was running 50-60C air temps.




What I make of all this is you need to run the turbo in its efficiency range with ambient air getting sucked into the intake. the intercooler really doesn't need to be big or that well ducted. The system has trouble sucking heat out of it by means of only an intercooler, the intake sucking in ambient air is better two fold. It is compressing already cold air, and the turbo works at a lower pressure ratio doing so.


so 15PSI with a turbo sucking in cold air running in its efficiency range doesn't rely all that much on the intercooler.


15PSI on the stock twins sucking in hot air from the engine bay relies heavily on the intercooler, but the intercooler is a super inefficient way to get back those CFM from cooling the air.


I would say the difference is about 30-50WHP easy. Hell, I picked up about 30-50WHP at the same boost pressure switching from a FMIC and hot air intake to going V-mount ducted and putting a large velocity stack and filter in ambient air.
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Old 10-14-16, 02:53 PM
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Ok. I see, you guys are talking about the intake manifold pressure, and are merely talking about the losses from higher air heat from the smaller compressor, and greater exhaust manifold pressure.
Those are losses of HP that aren't going to be nearly what you guys are saying with the proper tune, everything else equal.

Any greater losses will be due to an improperly sized and flowing exhaust, intake, inefficient intercooler, and improper tune.

The losses from compressor outlet temps alone shouldn't be THAT high and points to an inefficient combination of intake and intercooler, as you said pretty much.

The difference shouldn't be remotely close to 30-50hp from that alone, assuming the same exhaust manifold pressure. Just more intake heat shouldn't make you lose that much power unless your intercooler is only like 50%-60% efficient.
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Old 10-14-16, 05:47 PM
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Originally Posted by zaque View Post
Ok. I see, you guys are talking about the intake manifold pressure, and are merely talking about the losses from higher air heat from the smaller compressor, and greater exhaust manifold pressure.
Those are losses of HP that aren't going to be nearly what you guys are saying with the proper tune, everything else equal.

Any greater losses will be due to an improperly sized and flowing exhaust, intake, inefficient intercooler, and improper tune.

The losses from compressor outlet temps alone shouldn't be THAT high and points to an inefficient combination of intake and intercooler, as you said pretty much.

The difference shouldn't be remotely close to 30-50hp from that alone, assuming the same exhaust manifold pressure. Just more intake heat shouldn't make you lose that much power unless your intercooler is only like 50%-60% efficient.

When the pressure gets above 18PSI ish from a 7670 to 8374 the difference between the two turbo's could be 30-50WHP on the top end (same PSI between the two turbos, same manifold pressure). same set up every where else (I/intercooler/manifold/exhaust/etc)
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Old 10-14-16, 07:02 PM
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The EMP should only be like 20% higher (22.7 to 26.5psi) and the compressor outlet temp 10% higher in that example.

All things considered equal (intercooler efficiency, exhaust backpressure, resistance of the air intake filter, etc), it should be a 2hp difference.

Now, for example, if it's the same exact intercooler, it's not going to cool the hotter charge from the 7670 as much and you'll lose a bit more power. But it shouldn't be 50hp.
You said same set up everywhere else, but you need a more efficient intercooler for the 7670, so that's simply not a fair comparison.

And I guess HP losses from going from 22.7psi to 26.5psi EMP are probably going to be higher than just 2. But I'm not sure, there. Higher EMP is going to mean higher overlap, but higher overlap also means you can cram in more fuel and air, no?
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Old 10-14-16, 08:11 PM
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If they are not significantly different, then why do the two exist distinctly?

There's plenty enough dynos lying around this section to see without a lot of armchair physics that bigger turbos make substantially more power at the same boost with worse response, all else similar.

It's like, facts. Bruce Hornsby wrote a song about it.

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Old 10-15-16, 04:15 AM
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I'm not saying the dynos are fake. I'm just saying it's likely the intercoolers were too inefficient for the greater air temps out from the more worked compressors that are inefficient at that range rather than those losses all being attributed to the higher EMP.

Without knowing the air intake temps for both set ups, you have less of an idea of where the losses are from.

I'd like to see a comparison like that, same car, but put a Mercedes W220 intercooler there for each. It'd give a much better idea of how much of the losses are due to EMP. But something like that isn't going to happen, so it's mostly conjecture.

I know EMP certainly affects a rotary more than other engines, but 50hp is still seems like a huge loss to contribute to it alone.
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Old 11-13-16, 08:36 AM
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rough theoretical estimate would be 2% power per 10F change in intake temps. so 400hp on a 7670 at 130F would maybe be reduced to 100-110F on an 8374 at the same boost pressure, pulling those numbers out of my ***, but maybe close. probably make a difference of about +20HP due to temps alone, the rest would be due to less backpressure
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Old 11-14-16, 12:53 PM
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BW calculator does account for intake temp changes.
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Old 09-13-18, 06:44 AM
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Hello everyone,

So my plan was to get an EFR 8374 0.92 IWG from Turblown BUT I got a very good deal on a almost new EFR 7670 IWG 0.92 (w/ turbosmart BOV and actuators) for less than half of the price of a new one so I couldn't resist the tempation.

My FD has:
  • a freshly built motor with large street port,
  • Custom Vmount
  • Adaptronic Select ECU
  • I'm buying Turblown's short cast IWG manifold.
  • A friend is probably going to sell me his id1000 primaries and id2000 secondaries and
  • I plan to use these with the AEM fuel pressure regulator,
  • aftermarket fuel lines
  • a bosch 044 on a surge tank feeding my current AEM fuel pump.
  • Also upgrading Ignition probably using the Crane hi 6.
  • 3" downpipe with full 3" inch custom decat exhaust.
  • Tuned at 17-18 psi with European 100 octane pump gas
The friendly guys at Turblown said I should be looking at 400whp.
What do you guys think?
Any opinions?
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Old 09-13-18, 11:17 AM
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While I think 400rwhp Dynojet is possible on EFR 7670 at 18psi boost on a street port 13B-REW with good peripherals-

I wouldn't fixate on a certain dyno number, you will be love the power and response of the turbo if it is set-up and tuned well.

If you only make 390whp Dynojet and are disappointed by that you definitely should have held out for an EFR 8374.
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Old 09-13-18, 11:23 AM
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We actually use Maha dynos here which are known to produce very conservative (low) readings and that is at the crank. So if I see 440-470hp at the crank then i'm okay.

I want to learn the car with the 7670 and enjoy it. I don't care that much about a number. I just don't know how the car is gonna behave with this setup and what other newer cars can it beat in a drag race. Lol.
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Old 09-13-18, 12:49 PM
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Your Euro gas is about the same as US93 and you're going to need AI to run more than 14psi/1bar safely.

400rwhp is the high water mark for this turbo, so it's a good thing you don't care about the numbers...

The 7670 is effectively a replacement for the stock twins in a smaller, more efficient, and durable package.
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Old 09-13-18, 01:07 PM
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All our single turbo cars here run 1.2 bar safely with 100 octane pump gas without any octane boosters.

What is Al?

Also, Turblown said the turbosmart wastegate actuators make a huge difference over stock Borg Warner actuators in terms of top end power.

I think my car can make 400whp with all these mentioned above but we'll see.
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Old 09-13-18, 01:12 PM
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Auxiliary Injection, as in water/alcohol.
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Old 09-13-18, 02:08 PM
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I just don't know how the car is gonna behave with this setup and what other newer cars can it beat in a drag race. Lol.
The FD with EFR 7670 at 400rwhp will run high 10s to high 11s depending on set-up and driver.

I'm no drag racer, but first time at the track my EFR 7670 ran consistent mid 11s granny shifting. I took out modded AMG63 and modded Camaro (not ZL1) among others.
Everyone commented on how fast the car was off the line compared to my old 380rwhp T04B 60-1 set-up (same size turbo) that ran low 12s flat shifting.
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Old 09-13-18, 02:57 PM
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It'll be plenty fast with 350-400 whp. BLUETII is right. Somewhere around 12 flat for a decent driver in the 400m.
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Old 09-22-18, 07:28 PM
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Here is another one of our older welded 7670 iwg turbo kits we tuned last week. This is some unknown engine with what we are told is just a stock port. Stock location large intercooler. Full 3 inch exhaust, flex fuel with an Adaptronic modular. Tuned very conservatively. 19 psi down low and up top.
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Old 09-23-18, 01:00 AM
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^^
On stock FD 13B-REW ports I presume?

Very nice torque.
That E85 helps power everywhere!

That car at 19psi is making 35FtLbs more torque than I did at 2,500rpm and about 20FtLbs more torque at 3,000rpm even though I was peaking at 26psi boost and it looks to be peaking at 20-21psi if it is settling at 19psi as Turblown has said.

DAMN...must drive awesome.
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Old 09-23-18, 11:22 AM
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Originally Posted by BLUE TII View Post
^^
On stock FD 13B-REW ports I presume?

Very nice torque.
That E85 helps power everywhere!

That car at 19psi is making 35FtLbs more torque than I did at 2,500rpm and about 20FtLbs more torque at 3,000rpm even though I was peaking at 26psi boost and it looks to be peaking at 20-21psi if it is settling at 19psi as Turblown has said.

DAMN...must drive awesome.
This power output is very similar to what you see from an stock LS1, or LS2 swap in our experience. Now its not crazy straight line power, might be to some, but I can say you will be hard pressed to keep the gas floored in the twisty turns. Its got TOO much power for that, unless you are running full slicks on a track.
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