Borg Warner EFR Series Turbo's V 2.0

[Full-Race Geoff]

@Lithium The max turbo speed rating is determined based on tip speed of 560 m/s maximum.  The smaller diameter wheel must spin at a higher RPM to cover 560 meters per second compared to a larger diameter wheel.  Tip speeds above this 560m/s level are where any turbo is likely to fail

Edited September 20, 2017 by Full-Race Geoff

[Lithium]

OK, I went through all of the wheels converting the 560m/s max to rpm and it seems that the numbers closely correlate compressor tip speed to the comp maps with rpm instead of tip speed.   The trick here is that completely backs up what I had being saying that I suspect that the compressor maps don't give any information about the turbine wheel max speed.   In fact, the full race site actually gives the 9174 a higher max rpm than the 9180 despite having the same size compressor.   

It's VERY easy to see what I mean here...  please hold...

[Lithium]

On 9/8/2017 at 4:45 PM, MaximuSmurf said:

Just grabbed these off the GCG website.

EFR 6258 - 166,300 RPM

EFR 6758 - 153,900 RPM

EFR 7163 - 150,600 RPM

EFR 7670 - 139,200 RPM

EFR 8374 - 127,000 RPM

EFR 9174 - 125,000 RPM (taken from Full-Race website)

EFR 9180 - 116,000 RPM

 

Using 560/(comp.exducer / 1000 * pi)*60 I get the following numbers.  I am using the truncated exducer sizes from the turbo names because lazy so that will add a bit of error, but overall should be close enough.

EFR 6258 - 172,503 RPM 

EFR 6758 - 159,630 RPM

EFR 7163 - 150,636 RPM 

EFR 7670 - 140,726 RPM

EFR 8374 - 128,857 RPM

EFR 9174 - 117,529 RPM 

EFR 9180 - 117,529 RPM

 

Clearly the EFR6258 and EFR6758 are both the same turbine wheel, so this is nothing directly to do with the turbine's ability to handle those given rpm.  Also worth noting, based on that data the Full-Race site is suggesting you can spin the 91mm compessor off the map with the EFR9174.

I trust this explains my concern?

Edited September 20, 2017 by Lithium

[GTSBoy]

I think it would be fairly logical, unless you are Nissan/Hitachi, to make your turbine's speed limit higher than your compressor's speed limit.  This is particularly true if you can match your compressor's speed limit to its efficiency and capacity limits.

Then you only need to say that the speed limit on X turbo is Y rpm, because after that it's compressor is not going to work nicely and you stand a chance of breaking the comp wheel.  Meanwhile, the turbine has some higher limit that you should not approach because you can't get there anyway.  And all the emphasis on speed limits and speed sensors and stuff is completely sensible, because it stops people from simply overdriving their compressors.

I also suspect that the operating conditions on the turbine are a hell of a lot more variable than the compressor.  So whilst it might be possible to put a reasonably solid speed limit on the comp wheel based purely on mechanical strength and tip speed, the turbine will be running at different temperatures depending on the engine/fuel/tune etc etc.  If your published speed limits were to be imposed by your turbine, then you would have to use an arbitrarily low limit to handle the worst case of those conditions.  But if the turbine's limit is handily above that of the compressor, even at the worst case conditions, then you're all good.

Note that I am perfectly aware that people have managed to destroy EFR turbines.  I haven't paid enough attention to know whether they usually just kill the turbine or if they kill the comp wheel more or as well as the turbine.  There's probably also deaths attributable to bad tuning and high exhaust gas temps and all that other jazz. I don't think any of those deaths would necessarily invalidate what I said above though.

[Lithium]

Yeah agreed GTSBoy, but it feels like there are mixed messages regarding avoiding failures and I am just trying to get the best info I can for the good of everyone.   I don't want people to have failures, and neither do anyone who are selling them - but also I don't want people to be using them well below potential for fear of overspinning them when the failures could just be to do with people trying to push past their speed limit and everything going out of control.  

It is the turbine wheels which are failing, and there have been noises that the 9174 is good because the turbine can be spun faster - it clearly has the same compressor though, so maybe you can see why raise the question of if the compressor rpm limit may not necessarily be an overruling safe limit for that turbo?   Not saying I think that's the case, but would love to know if I should be telling people "ACTUALLY, stay below 105,000rpm to be safe" or "so long as you keep under 116,000rpm you should be ok".

Make sense?

Either way, anecdotally (at least so long as the safe limit for turbine speed is safely past the compressor stonewall rpm) it seems any argument about worrying about overspeeding these turbos being a sign they are too fragile to push hard is completely invalid - if the overspeed failures are because of exceeding the choke flow then they really aren't making any more power because of that speed anyway... its just trying to beat a dead horse to death at the risk of causing a turbine failure.

[GTSBoy]

Yuh, I'd suspect yahoo ignorance* as the primary cause of death.

*others may call it enthusiasm.

[minesskyline]

@Full-Race Geoff Do you think an upgrade from 6758's to 7163's would be worth it power-wise on a RB26 platform? Are there any other twin-EFR options that can do 1000+ HP? I might be looking at chasing more power and I like the EFR lineup so far, so am trying to see if there's something that makes sense for this platform. 

[Full-Race Geoff]

if you want responsive 1000+hp on any twin turbo application my opinion is EFR7163 can not be beat.  This is literally off-the-shelf indycar turbo setup.  Spool difference between 6758 and 7163 is about 300-400rpm depending on gear, but for this power level its an easy decision

 

[minesskyline]

@Full-Race Geoff Is it just a matter of swapping turbos from 6758 to 7163? Is anything else needed?

[Full-Race Geoff]

^^correct -  swap turbos, retune.  No other changes to the hardware, it is 100% plug and play for each other.  we have the turbos in stock with t2 IWG if you want to pull the trigger.  the powerband is pretty terrifying if thats what you are looking for

[minesskyline]

10 hours ago, Full-Race Geoff said:

^^correct -  swap turbos, retune.  No other changes to the hardware, it is 100% plug and play for each other.  we have the turbos in stock with t2 IWG if you want to pull the trigger.  the powerband is pretty terrifying if thats what you are looking for

Do you have any results from 7163's from Mustang dyno's? Everything I see is from DynoJets.

[Full-Race Geoff]

Not that I am aware of. 

[Piggaz]

RB28

8374/1.05

122k turbine speed.

Tapered back the boost top end.

 

[Dale FZ1]

Pretty strong result there

Boost taper to control turbine speed?

Would you put up the torque curve too please?

[Piggaz]

1 hour ago, Dale FZ1 said:

Pretty strong result there

Boost taper to control turbine speed?

Would you put up the torque curve too please?

I'll have to try and get one. The 486 kw run looks less flattering through the middle. Scott had to speed up the sweep because it was trying to pull itself up and out of the rollers.

Yeah, boost taper was just to leave some in the tank. 122,000 out of 127,000 turbine speed for the 8374.

Peaks around 26-26.5 psi falling back to 23 psi up top.

Had a bit of a play last night. On well before 4000 in second. You think you're ready to change, look down and you're still at 6000 rpm. Very seamless, no "whack", just builds and builds. The -5's felt way more aggressive and "snap onto boost". It would be a much easier car to drive quick. No surprises. At half throttle it makes 240 kw, exactly half of WOT throttle.

[SimonR32]

Would be interesting to see power difference between 122 and 127k. I assume that Borg Warner would have a decent percentage or error in those speeds (say 30-60%) so 127k should exactly be on the ragged edge.

 

[burn4005]

Said like a true precision user!

 

On a serious notw it's great to see the power just flatten and not nose over, even with the boost tapering. Gives me confidence the 1.05 is the right choice for a safe 450-480awwk

Edited October 1, 2017 by burn4005

[Kinkstaah]

Folks who have EFR

Are you (also) having issues with these things overboosting/spiking when coming onto boost? Nearly no matter what, if I try and apply throttle after feathering in 3rd/4th (or giving throttle up a hill) this thing will overboost. Revving it out from a steady pull it is fine and will sort of behave. But stabbing the throttle results in wild overboosting, the more load, the more overboosting.

Happens on gate pressure too (my gate pressure is 12, if I load it up suddenly on a hill I will hit 20+ psi), and making ridiculously conservative boost control settings results in making the thing laggier than it needs to be, kind of negating the point of the EFR if you can't quickly stab at the throttle for dat transient.

I am only trying to run 18psi, but pretty much any setting will result in this behaviour.

Anyone else?

[sneakey pete]

mines been rock solid but not sure i would have stabbed throttle enough to see. For those playing at home what boost control setup do you have?

[Kinkstaah]

I have a 50mm gate with a Haltech 5 port solenoid, with a 12psi gate spring in it. (i.e, it'll hold 12psi when directly connected, boost control is off). I am running a PS2000 ECU.

I can sort of run this in Open loop mode, but again with only very very conservative settings, which amount to basically having the gate fully open (i.e running 12psi) and ever so slowly adding duty cycle to avoid overboosting.

Some of this may be my setup which is why I am asking, I have an EFR7670 (1.05 rear) on a RB28Neo - And I am only trying to run 6psi over the baseline boost, i.e 18psi. The duty required to do that is only about ~15-20% duty cycle. I would assume if I was trying to run 25psi or 30psi it would be 'easier' as the duty cycle wouldn't be going from FULL CLOSED (to aid spool) to 15% (almost fully open), it may be going from 100% to 70% duty cycle, or whatever duty cycle is required to run 25-30psi in that example.

Given this, I am only getting full boost about 3700rpm, which most people would assume is kind of 'laggy' for a 2.8 with a 7670. I don't really mind the lag so much, but I do mind the overboosting as it's not consistent and it's severe. 

Now, a lot of people in this thread are 450-500rwkw and running 25-30psi so this issue may not be this present, or it could be a 'problem' with these turbos or these setup. Just asking around to see if anyone's got some insight here!