Brettus

iTrader: (2)

Turbo looks like a great option .... pricing very similar to Garrett but some great features! That size looks near perfect !
Some minor exhaust porting only .nothing on the intakes.
BTW I don't really agree that the 660 compressor is equivalent to a 7670 ..... It's actually closer to an 8374 (in efficiency) in the Pr ranges suitable for a Renesis. With that xona comp wheel .... It has a low trim value which means it will be more suitable for a smaller engine running high boost ...same as the 7670.

Brettus

iTrader: (2)

Did a bit more wrapping and heat shielding of manifold.
Result : Gain up top from more boost creep.
Bigger (44mm) WG is on the way.

TeamRX8

iTrader: (25)

my reference to it being similar to the 7670 is wrt flow potential which was the context at that part of the discussion

because context matters

in a broader context, it’s better than a 7670 in several key ways, the noted efficiency difference being one of them. Which is clearly demonstrated by the smaller impeller and resulting lower MOI of it (another plus) providing a very similar flow potential.
.

Staf00

Sorry, I didn't mean to take things out of context. But the 660, 7670, & 6465S do seem to flow about the same/similarly (60-65 lbs/min) on the cold side. The G30-660 apparently flows more than its wheel size indicates, which is an impressive feat! Tho I'm also curious how the 6465S would compare, especially with that "UHF" split-blade design on the hot side. Seems like the best of both worlds: lower MOI & backpressure while retaining the greater momentum capture of a high blade count. The turbine size is definitely closer to that of an 8374 tho. Correct me if I'm wrong but I always thought rotaries favored larger turbines (compared to an equivalent piston engine's requirements).

Brettus

iTrader: (2)

It would be good to see some actual results ..... often manufacturers promote something like this that sounds good in theory ..... but doesn't actually do much at all . They don't show turbine maps so without proper testing and comparisons ...who knows.

Bit of a generalisation. Rotaries do require bigger turbos for same power .. and large turbines work particularly well when there is a lot of overlap present , which is often the case with rotaries.

Staf00

Mostly from the results of your build. An older generation turbo of a similar size (i.e. GT3071R) would have less flow and efficiency, thus resulting in less power. It's impressive how far Garrett has come wrt their blade designs. I bet one day we'll have compressors that can exceed 80% efficiency. ^.^

GT3071R: 53mm/71mm


G30-660: 54mm/67mm

Edit: Yikes! Those images are huge...is there a way to make them smaller?

Btw, what are your thoughts on trim size? I was comparing compressor maps of the EFR8374 vs EFR8474 which both have an exducer of 84mm but different inducer sizes (62mm vs 68mm), thus a trim of 55 (EFR8374) vs 65 (EFR8474). If we compare compressor maps of the two turbos, it seems to be trading efficiency for flow along with an increase in mass/MOI, of course. I bring this up because I noticed the XR6465S has a very low trim of 53.9 which makes me wonder how efficient it may be, in lieu of actual compressor maps. The low trim should at least aid in responsiveness though. But like you said, we simply won't know without actual results/testing.

Which WG are you going to use exactly? TiAl MV-R 44mm?

Lastly, back onto the topic of the G30-660... You went with the 1.01 turbine housing, but in hindsight would rather have gone with the 0.83? Is that conclusion simply due to availability or would you perhaps go with something along the lines of a 0.92 a/r if such a housing existed?

Brettus

iTrader: (2)

I misinterpreted your comment so deleted my response. Yes........ they have come a long way.

As I mentioned above ..low trim tends to give a map useful for a smaller engine running high boost so if you want the same flow more efficiently at lower boost (ie larger engine) you increase the trim. that is evident in the 8374vs8474 chart you posted. This is why I like the 660. Same is true for most of the G series.

I'm actually warming more and more to the 1.01 .... spoolup still very good and knowing that emap is well under control gives me the confidence to 'turn it up'.
Yeah ...if they made the 0.92 available for the G30 ... I think that would be my preference. The 0.83 is dropping a little too far IMO but it would certainly make spoolup exciting.

Brettus

iTrader: (2)

Thinking about Trim some more.
Two compressors of same design and same out put with different trim would suggest ...lower trim= higher Prs (small engine) ...higher trim =lower Prs (larger engine) . In this scenario the trim is different because of the different exducer diameter. Inducer would be the same.
But..................... if the trim is altered by increasing the inducer size rather than by decreasing the exducer ...... what we see is both more flow and at lower Pr. Per the 8374 vs 8474 chart above.

Staf00

So in other words, a lower trim compressor would yield a more vertical map while a higher trim's map would be more horizontal? All else being equal of course...

But what I'm wondering is... what would be better for a Renesis that's aiming for a high redline? Say 8k+, even though most turbo builds tend to fall on their face by that point. This would suggest a high trim being preferable, yet the Renny is by no means a "large" engine. Would you consider 1 Bar to be high or low PR?

Brettus

iTrader: (2)

Yeah ..... that sounds like a good way to think about it .

Staf00

Hey @Brettus, do you have a shaft speed sensor installed on your turbo by any chance?

Brettus

iTrader: (2)

No .... maybe one day I'll look at that . On a maf tuned setup you would only look at it a few times when setting max. power. After that you wouldn't need it as maf will tell you if you are leaking air to the point of overspeeding it .

Brettus

iTrader: (2)

So........... I find this really interesting (sad I know) :
Compare the Turbine housings :
G 30 vs GT 35
1.21 G30 is near to 1.06 GT35
1.01 G30 is near to 1.01 GT 35
0.83 G30 flows less than 0.83 GT 35
0.61 G30 flows less than 0.61 GT 35

The 1.01 is pretty much the same but all others flow less than the equivalent GT 35 ..... kinda weird.

TeamRX8

iTrader: (25)

it wan’t directed at you and imo you didn’t. Because as stated in a later post, there aren’t maps for that turbo that you can compare anything to.

the way it was challenged is what was being addressed.

if you want to get down into the details they aren’t “identical”, but the compressor/turbine pairing reference is still valid which is what you were referring to.
.

TeamRX8

iTrader: (25)

because it’s not just the housing, the wheel design influences it as well

imo this has been overlooked a lot and I never had that full understanding until studying the new G-series line. The turbo comparison thread over on RX7Club is a good example. All it takes into account is the average are of turbine inducer and exducer. If we did that with your G30-660 it’d look ridiculously undersized. Obviously it’s not.
.

TeamRX8

iTrader: (25)

which as previously proposed, the G25-660 0.92 appears to offer a better flow profile than the G30-660 0.83 with a number of other advantages for the ultimate spool-up


G25-660



G30-660


.

Brettus

iTrader: (2)

The Renesis (6 port) for turbo selection purposes should be considered as a 3.0L engine (approx.) ...so yeah ...pretty big. Small low trim wheels like the 7670 suit 1.8 -2.5 engines (or a 4 port Renesis). You should have a play around with the matchbot software as it helps understand all the factors that go into a system.

Staf00

So what's stopping you from going for an 8k+ redline, if any? Is it just cuz you're falling off in the efficiency island (thus power as a result)? Fear of detonation perhaps? Or do you think you've hit the flow limits of the Renesis?

Brettus

iTrader: (2)

This: https://www.rx8club.com/series-i-maj...theory-268776/

Some will argue it's not relevant .......... I still think it is (on a stock Renesis anyway) until someone else wants to risk their engine to prove otherwise.

TeamRX8

iTrader: (25)

A rough overlay of the two maps; no doubt that the Garret compressor is a slightly better fit for either a 4P or 6P 1.3L rotary operating at the higher HP limit (efficiency centerline skewed toward the right compared to the 7670), but the turbine has to be factored into it as well. Which if the intention is to hold to that Renesis rpm limit theory, then again imo the G25 0.92 turbine combo needs to be seriously considered for most applications.







Also stressing again that (1); Matchbot cannot accurately model the dynamics of a rotary engine. Moreover, (2); manipulating input parameters to force the results to match a known output is not accurate. As you can see in the more recent posts, even the Garrett turbine housings don’t flow the same between various models/generations. So right off the bat you have no idea how much different your non-BW turbine is from where the points are being placed on their turbine map or whether the emap and host of other features is an accurate presentation.

The design of the housings, impellers, and so on all matter. If you don’t have a BW turbo then you’re flying completely blind using that program. The differences between the G-series and BW as being discussed in this thread should make it obvious on just how different they are. That all matters if you don’t have a BW turbo, because the program isn’t accounting for those differences. It only accounts for their known turbo parameters.

.

Brettus

iTrader: (2)

Except, it's not too hard to take the flow numbers off the Garrett map and put them in a position that matches the flow on Matchbot (wasn't it you that pointed that out ?). So ................... totally doable.
Nice work on the comp. map BTW .

Staf00

So with your current setup, what kind of flow rate would u say you're pushing by 7500rpm? And forgive my ignorance, but what's the flow rate of a 6-port N/A Renesis at 9k rpm? Also, you're in NZ... so your driver's side is on the right, correct?
Edit: I guess the answer is ~56 lbs/min?

Btw, I was trying to play around w/ BW's MatchBot thingy and was wondering what values you guys use to compensate for a rotary setup? Thx
Also, I noticed in your 2nd post that you had the 18psi line end at ~22psi (@7500rpm). Is that because you are expecting ~4psi of boost creep or something?
Edit: Nvm, I see that's probably what MatchBot outputted lol

TeamRX8

iTrader: (25)

Quote:

Originally Posted by Brettus

Except, it's not too hard to take the flow numbers off the Garrett map and put them in a position that matches the flow on Matchbot (wasn't it you that pointed that out ?). So ................... totally doable

I understand why you think it should be that simple, but perhaps it only signifies that the message about Matchbot being specifically programmed around the parameters of the BW turbo characteristics is still not registering. Because the statement quoted above is based on multiple assumptions ignoring the fact the G-series is setting a new standard in turbocharger performance. In addition to also ignoring that a program designed around reciprocating engine parameters is not going to accurately model the characteristics of a rotary engine. Therefore any and all outputs are highly suspect, if not entirely inaccurate.
.

Brettus

iTrader: (2)

What you don't seem to understand is that almost half of the values inputted are guesses anyway. So the accuracy of the outputs are only as good as that of the inputs. By actually measuring a lot of it and through experience you can eliminate most of the inaccuracy and get some good data. That is the same whether it's a piston engine or a rotary. You seem to have it in your head that there is some kind of majic sauce that skews the result for a rotary.
You have differences in BSFC, exhaust temp,Ve, and with a two rotor twin scroll , turbine efficiency, . Those parameters can be quite a bit different on a rotary ...but if you can get a handle on them ...it's just maths.

Brettus

iTrader: (2)

Here is one I did for my setup. The specific things you need to watch for on a rotary are :
BSFC
Exhaust gas inlet temp
Volumetric efficiency
Turbine efficiency (twin scroll PP engines can have great efficiency early in rpm range)



And yes stg is on the right here in NZ ...why do you ask?