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I am looking at a trying to build in some more N/A style responsiveness in the max torque to max power band mainly to make the little 7 a bit more fun on the track. It is currently running a K26 which is rather sluggish. I'll be moving the BOV from atmosphere to intake and adding some boost by throttle maps but am wondering if a twin scroll EFR 6258 with its low MOI wheel and integrated BOV would be the biggest help? It is running an NA 1.6L currently and I'll be swapping this with an OEM + rods + light port and polish, NB 1.6 with NB throttle body and intake manifold (MAP only) shortly.
Looking at Matchbot https://www.borgwarner.com/go/3ZMTJF it would appear I might run into surge issues with a divided manifold and the twin scroll 0.80 A/R turbine / housing. Does anyone have any experience with this on an NB 1.6L?
Very few here have any experience with the NB 1.6. It wasn't offered in the states at all and the one race team that tested one found no real benefits over the NA6.
I understand the size constraints with the Lotus 7 chassis are keeping you limited to the 1.6. The 6258 EFR spools more quickly than any other turbo of the same size but still may be larger than you need.
I'm using the mobile app so I can't see some of what you posted.
Cheers Six, yes I am just into the surge zone at 2000 rpm at 85% VE. Even at 100% VE I am still on the line. I guess I can waste a bit at these low RPMs to protect the turbo or would I be better to look at a 2560?
N/A style throttle responsiveness in the 3700 to 7000 RPM range is the goal. So I would be happy to sacrifice performance below that range if that make sense. That said I am also only just kissing the compressor map sweet spot at 7000 85% VE 18PSI. So maybe I would be better to find a turbo the had me out the other side of the island at 7000 essentially to provide greater efficiency between 4000 - 6000? Again responsiveness is the goal rather than outright area under the power curve so if the EFR is still the responsiveness king vs a 2560 even when it is a bit over matched and still coming on song in its 70% - 72% vs 75% - 76% efficiency range then it would still be the pick for what I am trying to achieve.
A bit depends on how well I have guessed the VE numbers for a MAP only, well intercooled, OEM 1.6L NB, with solid lifters, slightly higher valve lift, bigger throttle body, supposedly better flowing intake manifold, stage 1 head, custom divided exhaust manifold and twin scroll turbo with rods. I went with 2000 85% 3000 90% 4000 95% 5000 95% 6000 90% 7000 85% but this was just a guess. Does it look in the ball park?
Wide open throttle at 2000 RPM you should have downshifted. Same thing with 2500 and even 3000. If you aren't willing to downshift then you aren't truly worried about maximum acceleration and are just looking for a gradual rise.
If you want it very responsive, then you will want a turbo sized so that at peak airflow, it's on the upper right hand area of the map.
Indeed...rather than it only just making it to the island.. Just to be super clear, the kind of responsiveness I am after is throttle feathering in the ~3700 - 7000 range. So I am not worried about early scroll or below 3500 performance at all really. This primarily to create a driving experience that is dialed in to the smiles per mile super responsive go-kart like style of the 7s. I also prefer a linear power curve that feels free revving in these cars even if it is not faster if that makes sense. So it is the power delivery characteristics that I am after at the expense of low end and potentially area under the power curve.
Currently it handles crisp and snappy but the power delivery from the k26 is bit like a communist bureaucracy.
Essentially I am just trying to make it feel like a snappy free revving N/A car with a hard power band between ~3700 and 7000 that doesn't snuff out up top.
Is the EFR 6258 twin scroll going to do this job best from what is available currently with its integrated BOV and low MOI wheel and good lungs up top or is there a better option that I am missing?
Now if I have got the VE at 7000 for a 1.6L with a stage 1 head wrong by 10% that would make things fit better. I have guessed 85%. Could it be more like 95%?
Indeed...rather than it only just making it to the island.. Just to be super clear, the kind of responsiveness I am after is throttle feathering in the ~3700 - 7000 range. So I am not worried about early scroll or below 3500 performance at all really. This primarily to create a driving experience that is dialed in to the smiles per mile super responsive go-kart like style of the 7s. I also prefer a linear power curve that feels free revving in these cars even if it is not faster if that makes sense. So it is the power delivery characteristics that I am after at the expense of low end and potentially area under the power curve.
Currently it handles crisp and snappy but the power delivery from the k26 is bit like a communist bureaucracy.
Essentially I am just trying to make it feel like a snappy free revving N/A car with a hard power band between ~3700 and 7000 that doesn't snuff out up top.
Is the EFR 6258 twin scroll going to do this job best from what is available currently with its integrated BOV and low MOI wheel and good lungs up top or is there a better option that I am missing?
Now if I have got the VE at 7000 for a 1.6L with a stage 1 head wrong by 10% that would make things fit better. I have guessed 85%. Could it be more like 95%?
A big supercharger would be more like what you want it seems. Instant response and and basically feel NA but faster.
Figure out what you want, then build it. The first part is the hard part for me. I've been through so many build threads it's insane. Lost count of how many turbos have been spooled on my car, and how many setups have been tried and then modified or replaced to "improve" it.
You ramble about wanting responsiveness in every post, and then post a graph of a compressor map where you show that "if I run this turbo, I should be using half it's capacity at 7k RPM, less everywhere else, would this be the most responsive option?"
Obviously it would not be.
Go watch some of my SC vids on my channel if you want, there are more of the car with a SC than with it turbo. To me the big reason a turbo is more fun than a SC is for the power, but lots of people compared custom awesome turbo setups to small blower kit superchargers. There weren't any/many fast SC cars. So I made my own SC setup and it was boss, it ran mid 7's in the 1/8 mile with a manual trans. Super Super fun on the street. The ability to go from 20 to 60mph in about 2 seconds was really fun. To the point I've considered doing a SC V2.0 build next, even though the car has more power now turbo than it ever did SC.
Friend of mine recorded this, from 1st at about 3k RPM, to top of 3rd gear. More response than any turbo car you can build.
An S/C set up would be hilarious by the looks. I will definitely investigate further. This thread has certainly helped me crystalise around and find the language to describe what I want to achieve with this car.
It looks like this:
Idle - 3700: Happy for it to be a complete dog. It weights less than 600kg and I like a hard hitting powerband, mostly a track car, never driven for any practical purpose.
3700 - 7000: Linear, free revving power band and very responsive / sensitive to throttle feathering for N/A style throttle steering. Understood a fair bit can be done with boost by throttle position and other boost preserving tuning tools + good re-circulation.
6000 - 7000: Want it to pull clean and hard here. Really don't want it to be snuffing out at all.
Can this be achieved with a turbo on a 1.6L with a stage 1 head, if so which one?
Does this requirement "3700 - 7000...and very responsive / sensitive to throttle feathering for N/A style throttle steering" basically mean I have to go N/A or S/C and any turbo that comes close is going to snuff out up top?
08-28-2019, 05:55 PM
Volumetic Efficiency Matchbot numbers for NB 1.6
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Just to be super clear, the kind of responsiveness I am after is throttle feathering in the ~3700 - 7000 range. So I am not worried about early scroll or below 3500 performance at all really. This primarily to create a driving experience that is dialed in to the smiles per mile super responsive go-kart like style of the 7s. I also prefer a linear power curve that feels free revving in these cars even if it is not faster if that makes sense. So it is the power delivery characteristics that I am after at the expense of low end and potentially area under the power curve. 
