[Closed] Borg Warner Efr Series Turbos

[bradsm87]

Mine should be going soon. Just waiting a few bits now...

[Lithium]

Nice, I forget - is that a 7064?

[bradsm87]

Yep

[GTScotT]

Oh MAN. So jelly!

I've been considering one of these as stage 2 of my build. Will be watching this thread like a hawk for results now.

Whats your goal for power?

[bradsm87]

Not a huge amount as I want to keep the weak 6 speed box. Hoping for around 240rwkw @ 16psi with full boost by around 3000 and awesome response from off throttle to on. That's with poncams, 9.5:1 cr, 89.5mm bore (2.16L) and home mixed E50 fuel.

[GTScotT]

Really.. maybe I wrongly estimated that turbo as I was think more 100kw above those figures when on ethanol.

time will tell I guess! Fingers crossed for a good result.

[scandyflick]

It's a big turbo for the build.

My 6258 is making ~260 with a standard SR bottom end, step 2 cams and E85.

[Lithium]

Really.. maybe I wrongly estimated that turbo as I was think more 100kw above those figures when on ethanol.

time will tell I guess! Fingers crossed for a good result.

Yeah I'd expect quite a bit more power than that on an ethanol blend, though 16psi is a strangely low boost level to choose to run on such a decent build. May as well run an EFR6258 or EFR6758 imho and get similar power and better response, and would be more likely to reach that boost by 3000rpm as I honestly can't see an EFR7064 spooling that soon.

[bradsm87]

Remember we're talking 16psi. Yes I could make 300 on 23 odd psi and yes I could make the same power on a smaller turbo with more boost but that's not what this build is about. I'm after a flat na-like power delivery where the motor is making most of the power all by itself with the turbo giving it a bit extra. It's a daily for my wife and that type or torque curve is way better on fuel, tyres and gearboxes.

My old S14 made 286rwkw with a GT2871R on 24psi of boost but this car should be completely different to drive to that. Better torque off boost and while building boost, able to run leaner and more aggressive timing due to lower overall boost and much better torque curve for a daily.

Edited February 12, 2013 by bradsm87

[Lithium]

I get that - but you could make that power on that boost with a smaller EFR, if you are never going over 16psi then the extra flow potential of the larger turbo is pointless. I never said run the smaller turbo on more boost, you won't need to... you aren't going to be stressing an EFR6758 at that kind of boost level with that kind of setup imho. All you've done there is matched a turbo which will provide you with a bit more lag.

I am sure it will be a nice setup regardless, but just interesting logic. I've tended to find the less laggy turbos (which make similar power) to have a more NA power delivery. In terms of leaner or more aggressive timing, those fuel/ignition curves will always be the same at those boost levels. You have the option of tuning for 24psi with the same turbo, but running 16psi and a good tuner will have the more aggressive ignition and leaner mix at those zones.

Looking forward to seeing the results, all the same

[bradsm87]

That's not entirely true. If you want to stay in the efficiency range of a turbo at a given power level at lower boost, you generally need to upsize the turbo. You'll notice compressor map efficiency islands lean over to the right. Sorta hard to explain. Also I wouldn't be able to tune the engine the way I want it to unless it has a very high flowing turbine side with very low back pressure. Also because you're asking less boost of the turbo, the required speed to spin it up to is lower so response isn't too bad.

Edited February 12, 2013 by bradsm87

[Lithium]

That's not entirely true. If you want to stay in the efficiency range of a turbo at a given power level at lower boost, you generally need to upsize the turbo. You'll notice compressor map efficiency islands lean over to the right. Sorta hard to explain.

No stress with explaining, I have a pretty decent idea of how compressor maps look and what it all means. I don't have the time to do a bunch of specific calcs but as a bunch of thumbsucks, I figure you don't need more than 40lb/min (arbitrary number I picked easy to find on a compressor map) of airflow to make the power you are talking about using E50. If you look at the compressor map then at pressure ratio 2.2 the EFR6758 has a slightly higher compressor efficiency at that 40lb/min area than the EFR7064.

Also I wouldn't be able to tune the engine the way I want it to unless it has a very high flowing turbine side with very low back pressure.

The EFR6758 turbine is spec'd to go with a compressor which will choke at 49lb/min you won't be going near that on 16psi - if you had any issues regarding pressure differential to the level it will tangibly affect what you can do with your tune it is not going to be the turbine flow you'd have with an EFR6758 which would be responsible for it. I'm not saying the EFR7064 will be bad at all, it's nice having headroom - but as far as I am concerned that is the only advantage you've got in this case.

[scandyflick]

It's a big turbo for the build.

My 6258 is making ~260 with a standard SR bottom end, step 2 cams and E85.

Remember we're talking 16psi. Yes I could make 300 on 23 odd psi and yes I could make the same power on a smaller turbo with more boost but that's not what this build is about. I'm after a flat na-like power delivery where the motor is making most of the power all by itself with the turbo giving it a bit extra. It's a daily for my wife and that type or torque curve is way better on fuel, tyres and gearboxes.

My old S14 made 286rwkw with a GT2871R on 24psi of boost but this car should be completely different to drive to that. Better torque off boost and while building boost, able to run leaner and more aggressive timing due to lower overall boost and much better torque curve for a daily.

I guess I should have mentioned that power is made at a nice and boring (partner friendly) 15psi...

[GTScotT]

lol Dave is your 260 at only 15psi?!

Turn up the whick man, what the faaaark.

[bradsm87]

I could be in for a big surprise with the power it makes then. The plan is to run 14psi from as soon as it can make it up to 4000rpm then taper up to 18 at about 6800 to hold the torque flat. It'll make whatever it makes at that boost. Could be 250. Could be 300. Don't really know.

[Lithium]

Can I suggest getting it tuned to follow that boost curve, but also set it up to have a nice flat one too and try both out on the road to see how youfind them... Just in case?

[SimonR32]

So you have forked out on pretty much the most expensive and hardest to source turbo that's too big for the application so compromises response and then use a boost controller to further decrease response?

I want the drugs you are having!

Edited February 12, 2013 by SimonR32

[bradsm87]

No it will hit 14psi as soon as possible (est. around 2800rpm) and hold flat until the torque starts to drop off (est. around 4200rpm) and boost will slowly increase to counteract the drop-off of torque and hold the torque flat. The turbo is not too big for the application at all. Upsize engine and plan to run low boost and make efficient power = bigger turbo required.

On match-bot, with NOTHING changed but going from 6758 to 7064, efficiency is higher across the board because the 7064 has a lower trim compressor wheel and anti-surge housing. Also the exhaust manifold pressure is considerably lower with the 7064. The twin scroll setup helps response as well.

Lithium, I won't be doing a flat boost curve because the clutch or gearbox can not handle any more torque through the midrange. Instead, less peak torque will be made but higher average torque across the RPM range because torque will not drop off at all until about 6800rpm so it will be a very fast car.

Edited February 12, 2013 by bradsm87

[scandyflick]

lol Dave is your 260 at only 15psi?!

Turn up the whick man, what the faaaark.

Haha, yeah mate, on a Mainline too. It's a fairly entetaining thing. Thinking about 18lb when I get it all back together.

[SimonR32]

No it will hit 14psi as soon as possible (est. around 2800rpm)

Is it an RB34?