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This is a comparison between friends 350z with built motor and Greddy 18g bi-turbo kit (red curve) and mine, big single twin scroll turbo (blue curve). Very little difference in low rpm area.
Both motors having 8.8:1 CR, a friends bi-turbo have stock cams, while mine having JW C8 cams, which are quite aggressive. I can bet, with stock cams my motor would outperform bi-turbo in lower rpm's too. And the turbo I'm using is a Precision 6766 with billet upgrade compressor wheel, exhaust housing A/R 1.32.
Yes and no. Originally it was single scroll Boosted Performance kit which I bought 2nd hand here on boards and convert it to a twin scroll.
This power is made with "low boost", 1.2 Bar or 17-18 PSI, couldn't crank it more because wastegate springs were too soft. Retune will be soon, expecting to make more power and peak boost at 1.5 Bar.
Here's a difference between standard PT 6766 (left on the pic) and upgrade billet compressor wheel (right)
Congrats on the power but there are too many variables to make this a valid comparison. That said, if I was doing it all again, it would be a single twin scroll. Mostly because of cost, simplicity, availability, and accessibility. Not for power (you can compare our power curves and two small twins is hard to beat - 500 whp at 4k rpms)... We are lucky to have BP developing high quality and affordable twinscroll kits for our platform!
Yeah like RC said, the differences between the greddy tt kit and a new billet cea wheel are huge. Twin scroll helps, but billet wheel probably did just as much if not more. It gives the vanes more aggressive angles, so it flows better.
Nice curve though, sure it's a great car to drive!
Yeah like RC said, the differences between the greddy tt kit and a new billet cea wheel are huge. Twin scroll helps, but billet wheel probably did just as much if not more. It gives the vanes more aggressive angles, so it flows better.
Nice curve though, sure it's a great car to drive!
An upgrade billet compressor wheel is heavier (not much but is) and while it flows more indeed, it negatively effects on the spool.
We will probably upgrade friends 18g twins later this year, I'll post results here.
Also, I'm not using Precision exhaust housing. Instead, went with Mamba P-trim housing which needed some machining to fit PT turbine shaft. And that might have much bigger impact on spool.
James, without you I couldn't get so far or at least not that quickly! Thank you for your patience with me and my countless requests for reshipping stuff overseas.
You were always be so kind, hopefully we will met some day and drink a couple of beers .
P.S.
Finally started dressing engine bay, not done much so far but hey, it's a progress
An upgrade billet compressor wheel is heavier (not much but is) and while it flows more indeed, it negatively effects on the spool.
We will probably upgrade friends 18g twins later this year, I'll post results here.
Also, I'm not using Precision exhaust housing. Instead, went with Mamba P-trim housing which needed some machining to fit PT turbine shaft. And that might have much bigger impact on spool.
Anyway, true, the car drives like a champ .
Thanks!
The reason cea's keep flowing at such high psi is because they're more efficient per revolution. I wasn't talking about impeller speed but, flow. If you have a turbo that flows more at lower turbine speed, you have one that should be more efficient at high turbine speed. Something we know is true for precisions.
Again the comparison between a billet single and old school mitsu twins is really hard to make, because they are inherently different.
The reason cea's keep flowing at such high psi is because they're more efficient per revolution. I wasn't talking about impeller speed but, flow. If you have a turbo that flows more at lower turbine speed, you have one that should be more efficient at high turbine speed. Something we know is true for precisions.
Again the comparison between a billet single and old school mitsu twins is really hard to make, because they are inherently different.
Understandable, but still, we are here talking about almost double power capable turbo system (PT6766 is 930HP rated, and with this billet compressor probably over 1000) with almost same efficiency at low rpm as smaller turbo's system.
Originally Posted by Boosted Performance
Congrats...those are some solid numbers.
That turbine is available in 1.52 a/r as well.
Sacha, thanks! Yes, I knew about 1.52 before purchasing A/R 1.32 exhaust housing but my biggest concern was will it fit without compromising turbo height position. I'm very happy how it performs and can't stop thinking why I didn't do it much sooner. This twin scroll design is much much efficient than your first, single scroll design. Difference is night and day!
Understandable, but still, we are here talking about almost double power capable turbo system (PT6766 is 930HP rated, and with this billet compressor probably over 1000) with almost same efficiency at low rpm as smaller turbo's system.
Single is absolutely the better choice. But we are comparing mitsu jb turbos on log manifolds, parts of a kit that is over 12 years old, to the latest billet single kit. And I think that's the crux of the comparison. It doesn't mean your kit is not great, because it's pretty much the best street single setup you can run give or take specific turbo specs.
think you have some things mixed up dude
1)the billet cea 6766 is rated at 935, the OLD cast 67's where like a 700 hp turbo, the billet 6765 was a huge jump and then when they went to the 66mm cea exhaust wheel it made another jump in power.
2) cast vs billet wheel the billet will always be lighter for the same size, billet is stronger allowing thinner everything, if a billet wheel is heavier its because its running a wheel with longer fins or more and even then its doubtful to be heavier at best match the weight. This is a big reason the billet turbos spool faster. In fact i know of a billet 76 that will spool about on par with the 6766 cea and make 1400 hp each...... however with the options to do it the turbo is about $5500....... i know as im going to be running two of them
3)as they said the twins use old school turbos, they are using cast everything and compressor and impeller designs that are ancient. the design of the wheels alone play a huge part. those turbos are 50mm and realistically the most your going to put out is about 400 per turbo, the closest you will look at comparatively in new design would be a precision 55, which is 500 hp for the MFS and 590 for the billet CEA turbos both of those turbos will outspool the 18g's from being both lighter in rotating assembly and more efficient designs. all things equal twins will outspool a single, a single is usually easier to package for a given power without moving twins to some location that kills the advantage of their spool being closer to the exhaust ports.
Cool. Now throw a pair of 14 blade ET billet KTS wheels and 9 blade 05h turbines into the MHI turbos, run the same boost and do the comparison. I can't believe no one ever upgrades the Greddy/MHI turbos to all the new aero that's available.
04-25-2016, 01:05 AM
Twin scroll or bi-turbo?
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