a couple of years ago it was pretty simple... the 8374 or the 9180.

we now have 6 turbos heading upwards powerwise from the 8374 and i am getting lots of head scratching and in some case regretful decisions.

here are the turbos and rotary rear wheel power estimates*

8374 529
8474 693
9174 648
9180 655
9274 791
9280 828

notice the 8474 is nowhere near the 8374 as to output. while it is close to the 9180 as to output, it shares the same turbine wheel as the 8374!

8374 72 pounds per minute of air and a 5.91 average square inch turbine wheel. 12.18 pounds air per square inch wheel area
8474 92 pounds P M of air and a 5.91 aver Sq In turbine wheel. 15.56 pounds air per sq in
9174 86 pounds P M and a 5.91 aver Sq inch turbine wheel 14.55 pounds air/ sq inch
9180 87 pounds P M and 7.15 av sq in turbine wheel 12.17 pounds air/ sq in

if you look at what BW did with the SX-E line as to mating hotside area to output it underscores my observation:

SX-E 62 76 pounds of air output 6.31 aver sq inch turbine wheel 12.04 pounds of air per sq inch hotwheel area (similar to the 8373 and 9180 but not the 8474)
SX-E 63 78 pounds/air 6.31 hotside 12.36 ratio
SX-E 64 81 pounds/air 6.13 hotside 12.83 ratio

SX-E 66 87 pounds of air.

if BW had continued to use the 6.31 area wheel the ratio would have been 13.78. They elected to use (only) the 7.15 wheel making the ratio 12.16 which is similar to the 8374 and 9180.

general best power (on gas) EGT for a piston engine is 1322 F. rotaries are about 300 higher. i find 100 F lower EGTs and 20% less back pressure with the larger hotside wheel.

if you are going for the higher end of the dual purpose scale (around 600) i prefer the 9180 over the 8474 or 9174.

* power calculation using max flow efficiency post as per BW suggestion... rather than max rpm.

 

It is a reasonable range now however I feel they are missing a compressor inducer between 67 and 74 that would be a better compromise between response and outright power on the larger turbine, you could probably argue similar on the smaller 74 too.

Should provide a better choice and extend potential power for packaging of each anyway.

 

thought it might be helpful to post the SX-E rotary rwhp

62 572
63 587
64 610
66 655
69 738
72 836

 

Don't forget the 76er that outflows the SX80

 

Interesting info, I'm considering updating my setup from my gen2 6766. At first I was thinking the 9180, but the idea of quicker spool with more power under the curve is very enticing.

In theory, the 8474 seems perfect for my needs/wants. My current setup was street tuned to 32psi (somewhere in 600+whp). The last Dyno I had was at 20psi where it made 489whp with a slipping clutch on a mustang dyno. Unfortunately I don't have any data logging equipment to verify spool time or back pressure, but it is very fun and seems responsive and doesn't seem to be an issue.

The 8474 sounds like it would provide the same power, but more of it everywhere due to the lighter wheels (turbine of the 8474 seems to be the same size as my 6766 if I'm understanding properly with a compressor that has the same size inducer and smaller exducer compared to a 6766) .

If I went this route, I wanted to do the iwg set up to simplify everything and lower maintenance items (I've already had to replace wastegate diaphragms twice is about 7 years, absolute pain on a rerouted wastegate to exhaust system).

Would the 8474 not be suitable or cause too much back pressure to be ran in the 30psi range and still keep quicker spool than the 9180?

 

The 8474 looks like a real winner. I would also like to know how spool/back-pressure would be on a 9180 vs 8474 as it relates to a rotary.....

 

Does the 8474 really outflow the 9180 by that much? How is this possible? Its a smaller wheel is it not?

 

as you can see the 8474 makes 92 pounds per minute. as far as i am concerned the question is what's with driving this monster cold side w a small turbine wheel.

i will call my BW guy tomorrow and get some answers.

 

What do you think about the 9280 on a 3 rotor

 

"updating my setup from my gen2 6766. At first I was thinking the 9180, but the idea of quicker spool with more power under the curve is very enticing.

In theory, the 8474 seems perfect for my needs/wants. My current setup was street tuned to 32psi (somewhere in 600+whp). The last Dyno I had was at 20psi where it made 489whp with a slipping clutch on a mustang dyno. Unfortunately I don't have any data logging equipment to verify spool time or back pressure, but it is very fun and seems responsive and doesn't seem to be an issue.

The 8474 sounds like it would provide the same power, but more of it everywhere due to the lighter wheels (turbine of the 8474 seems to be the same size as my 6766 if I'm understanding properly with a compressor that has the same size inducer and smaller exducer compared to a 6766) .

If I went this route, I wanted to do the iwg set up to simplify everything and lower maintenance items (I've already had to replace wastegate diaphragms twice is about 7 years, absolute pain on a rerouted wastegate to exhaust system).

Would the 8474 not be suitable or cause too much back pressure to be ran in the 30psi range and still keep quicker spool than the 9180?"

"I would also like to know how spool/back-pressure would be on a 9180 vs 8474 as it relates to a rotary....."

"Does the 8474 really outflow the 9180 by that much? How is this possible? Its a smaller wheel is it not?"





i have been a fan of the more recent clean sheet of paper Precision turbos....

your 6766 GEN 2 will make 700 rotary rwhp.
compressor is 7.51 sq inches and hotside wheel is 6.0

93.5 PPM / 6 = 15.58 so the turbine wheel is on the small side for the output similar to the 8474 (15.56).

dissimilar to the 9180 at 12.17

the compressor output of your Precision is virtually the same as the 8474 (92 PPM)

compressor area is 7.1 on the 8474 and 7.51 on the Precision so the BW is more efficient as to output V wheel size.

worth noting is the Trim on the 8474 is very large at 65... meaning the compressor inducer area is 65% of the exducer. this is on the far edge of the scale and favors top end at the expense of midrange.

your Precision is 58 Trim. the 9180 is 56 Trim both delivering more midrange than the 8474

one of my favorites, the SX-E 66 is 52 Trim... combined w 87 PPM output/ 655 rotary rwhp, the Trim makes it a midrange killer with great top end... but i digress

comparing your Precision w the 8474...

in theory the 40% lighter turbine wheel should give it a spool advantage... Dan Barlog, the key engineer at Precision told me that they tested the titanium aluminide and found they could not shape it into their ultimate configuration so they "picked flow over weight." you may choose to believe this or not but Dan is a serious engineer and Precision is on the cutting edge of design as they do not have to jump through the OE design constraints.

a key question as you contemplate midrange or dynamic spool is how the lighter hot wheel nets out against a very clearly biased to top end Trim number.

the large Trim is probably the reason for the high max flow V the 8373 (55 Trim)

my primary concern is EGTs... while i compare turbos using wheel areas this, as any other metric, is only part of the story. if you had two identical dimensioned wheels and one flowed more than the other it would require more effort to drive. according to BW it takes approximately 100 hp to drive the compressor wheel... this is resistance against the turbine wheel. the more resistance the more backpressure and EGT. so with the 8474 you have, probably because of the high Trim, a very high resistance wheel driven by a small hotwheel. all of this puts additional stress on the pre-turbine flow...

i would not dismiss this dynamic as you may not be happy with 2000 F EGTs as a tradeoff for more (maybe) midrange.

all this is speculation on my part but if true, and i think it is most probable, you will have no fix.

the plus on the 9180 is the free-er flowing 7.15 hotside and the 56 mid range compressor Trim

i had a discussion w one of the top BW engineers as to the 9180 and 8474 re my October Texas Mile run. he was very clear that the 9180 would be the better turbo as the motor needs to get the exhaust out to keep EGTs and backpressure as low as possible as after the first quarter mile i shift into 5th gear and am in 5th for 17 seconds just under the 600 rwhp area. he was very clear on his advice.

as to wastegating...

first off, if you are losing diaphragms the fix is not an internal wastegate. as turbos climb in output and especially midrange delivery wastegates become waay more important as to efficacy. i remain skeptical that any internal wastegate will offer the control of a Tial external. other factors as wastegate performance are of course manifold design. it simply depends on where your diaphragm locates in relationship to heat.

see my system design section

SYSTEM DESIGN

 

"What do you think about the 9280 on a 3 rotor"

the 9280 is a 829 rotary rwhp turbo... maxxed out you would be at 552 2 rotor which is a reasonable rotary power level for longevity.

since the compressor is pretty large (8.36 sq inches) and is powered by the same 80 mm (7.15) wheel as the smaller 9180 the hot cold relationship is on the wrong side of the relationship at 15.38.

the compressor Trim is 66 not favoring midrange but because you have 50% more motor driving the turbo that is not a problem.

so powerwise, pretty nice, just a concern as to hotsize V coldsize and EGTs.

 

I got a 9180 on 3 rotor and it is dumb, blows tires out into 4th. But then again I do run a greddy red spring. Still want to try a 9280 at some point.

 

So at what rpm you start making boost?

 

on paper the 8474 seems to be the winner for a balanced setup for response and power. Seems to be a major upgrade from the 8374 which i am currently running (and loving at 30psi)
I am willing to try it as some point as long as my tuner is ready to do the transatlantic flight again !

 

Wow, this is a lot of info. So in theory the 8474 would be good, but at the cost of higher back pressure and egts compared to a 9180 (thus canceling out any benefits at the cost of more stress). I wish the technology on the wheels didn't limit things. A theoretical 8480 sounds like it would be a monster.

 

Any idea of a back pressure estimate comparison between 9180 and the new 9280?

 

Will entirely depend on manifold specs, primarily runner size and length, and the size of the hot side housing. Volume and pressure are directly related. I believe the hot side wheels are the same between the two so turbo to turbo there shouldnt be any difference on the same manifold and housing, and even if they're different the wheel size effects of backpressure are minimal compared to the effects of volume.

Skeese

 

^ , surely will affect backpressure to some extent if you are putting the bigger compressor to good use

 

Yeah it seems these new sizes, (in my completely unprofessional opinion ) Arent really that well suited to a rotary as they are all going up a size on the compressor or down a size on the exhaust. Seems the two theoretical winners would be an 8480 as you say and, say a 7774 or an 8274 or something for the guys that want more than a 7670 and less than an 8374

 

If you have a manifold and hot side that's sized correctly for your port and power level it will stay under a 1:1 ratio with intake pressure regardless of the increase in mass flow from a slightly larger compressor, which is why backpresure matters in a high overlap engine in the first place.

Skeese

 

I'm at full boost the second I put full load on the engine on the engine dyno, though I'm sitting at a mild 21 psi. I don't bother loading it up below 3000 rpm either.