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A little info on the Morris internal volute mods. Not sure if any before/after details though, although I'm sure they want to keep some details to themselves.
Do the maps really look that great at the common pressure ratios used on LS engine in a twin config?
Yes actually... considering to my knowledge compressor maps are in absolute pressure. It would be easy to get an LS in the 70-80 lb/min range. Which should be good enough for ~1400hp, granted for some people that may not be enough from a small twin setup.
Here is the reason why I didn't bother turning it up anymore past 28psi. Both data logs start from a dig and just flat footing it. When tps reaches 100% the log starts. The solid lines are the Borg SXE369s and the dashed lines are the Precision CEA 6766s. The 369s take 5.3 seconds to reach 14psi. This is with basically pinning the gate shut on the dome. The 6766s are at 17psi around 1.7 seconds. I had to lift cause it started to spin at that point. The 6766s even caused the converter to flash 600rpm higher. I will never use any of the Borg SXE turbos again.
Here is a pull from 60mph-176mph with the precisions. I use boost by mph off a front wheel speed sensor. 31psi by the top of 1st gear and ramping up to 34psi. I short shifted at 7400rpm and that causes the dip in boost. Converter is tight.
None of the above seems surprising, considering the CEA turbos have a significantly smaller turbine wheel compared to the s369sxe...
Andrew
x2 66/74 vs 73/80, Looks like his 5.3 is not realizing a benefit from the turbine increase and spooling slower. I've seen 369's on a big cam 376ci spool twice as fast as what his chart shows. I think on a 400+ ci they would shine even more.
Wonder if you could tweak the 5.3 into liking the bigger turbines a bit more via cam choice, or just leave off the two step at 10+lbs and let them eat.
Even on my 383 at 28/29psi boost with the smaller 68mm wheel, MAP vs EMAP is still pretty much 1:1 ( 0.88 housing )
So the standard 369 with the large turbine is perhaps a bad choice for the smaller engine.
Too big as twins, but as a single for a street car, I think it is darn near perfect.
There are some posts on the truck forum that claim exhaust back pressure issues past 12psi, but I don't see that happening. Sure, it will "only" make about 600rwhp at 13psi at about 5500 rpm, but the torque curve would be amazing. The boost can be turned up between 2500-4500 RPM and that puts it right in the middle island for efficiency. The S366sxe is actually even better suited for that.
Here is a comparison between the S369s and a pair of Turbonetics billet 7575s BB with .96AR housings. Both had very similar spool characteristics. Solid lines are S369s and dotted are 7575s
Here is a comparison between the S369s and a pair of Turbonetics billet 7575s BB with .96AR housings. Both had very similar spool characteristics. Solid lines are S369s and dotted are 7575s
That's good data and expected results, heavier 75 compressor wheel with similar sized hotside spooled even slower. From that graph it looks like the 369's spooled a good bit faster then the 7575, around 4-5k RPM it was almost double the boost.
Did you try leaving at ~4k RPM on a two step? Seems like they would come on pretty good from that point.
Yes actually... considering to my knowledge compressor maps are in absolute pressure. It would be easy to get an LS in the 70-80 lb/min range. Which should be good enough for ~1400hp, granted for some people that may not be enough from a small twin setup.
I mean when compared to other turbos that flow more at lower pressure ratios. Which is kinda what you want with a twin setup on a V8 that's not pushing say 30-50lbs of boost.
That's good data and expected results, heavier 75 compressor wheel with similar sized hotside spooled even slower. From that graph it looks like the 369's spooled a good bit faster then the 7575, around 4-5k RPM it was almost double the boost.
Did you try leaving at ~4k RPM on a two step? Seems like they would come on pretty good from that point.
All the testing I kept the start points exactly the same. With the Holley 2 step it swings the rpm too much to get the exact same starting rpm. I do alot of racing from 60mph and both the 369 and 7575 where slugs from 60mph even with brake boosting. They still took too long to come into boost. I haven't been a precision fan since 2008. I dealt with a lot of failures back then and refused to use them until this year. I couldn't make more than 1285whp with the 7568s and the reason for change is I wanted more. So far the Precisions are far superior on my setup than the other turbos tested.
Well we got two SX369's going on a 400+CI LSX motor in the next few weeks. I'll report back.
Do you have some good results/logs on that setup now? They seem to work really well on my smaller engine setup.
Originally Posted by DBRODS
Here is the reason why I didn't bother turning it up anymore past 28psi. Both data logs start from a dig and just flat footing it. When tps reaches 100% the log starts. The solid lines are the Borg SXE369s and the dashed lines are the Precision CEA 6766s. The 369s take 5.3 seconds to reach 14psi. This is with basically pinning the gate shut on the dome. The 6766s are at 17psi around 1.7 seconds. I had to lift cause it started to spin at that point. The 6766s even caused the converter to flash 600rpm higher. I will never use any of the Borg SXE turbos again.
Looking at my logs from a 5.3L with twin S369's I'm having drastically different results. My S369's spool more like your 6766's, I have no problem getting into boost very quickly. Honestly shocked me how fast these got into boost as I was expecting them to be laggy compared to single setups but really not much different at all.
I used what I think to be a free flowing setup with a larger (for a 5.3) 231/239 113 cam, 1 3/4" up and forward headers, 3.5" downpipes, Precision 46 WG's, S369's with T4 .88 housing, Edelbrock Pro-Flo XT, running on E85 controlled by Holley EFI with Holley 160 injectors and Magnafuel 4703 pump.
Any more experience with the 369sxe in a twin config?
These things are killer on a 3.0 2jz, not sure why they wouldnt be with 2 on a 6.0???
As mentioned the smaller engnes run at a much higher pressure ratio on the map where the s369 really shines. Most arent going to run 40-80+ lbs of boost like the small engine guys do. Not thT u cant make great power w them, but they arent going to perform like they do on small engines
Seems Nathan Shaw bolted a set (S369SXE) on his Nova. Hasn't posted results but says they feel great. This should provide some insight and valuable data as compared to his TC 72 cast wheel/68 turbine combo....car went something like 7.9x @ 172.
With a combo that sorted out...the results of the new turbos should validate the findings.
12-15-2016, 08:22 AM
