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The plastic grill is more restrictive than it looks .... I'd say the mesh is better but not sure that it makes much difference TBH.
I like it. If nothing else ...as you say it's less restrictive than the plastic OEM jobbie, and still provides some protection for the IC and rad. That's actually my next minor upgrade. I already have the sheet mesh I'm going to use.
In an earlier comment you mentioned that 9 psi of boost was as about as high as you would go on pump gas, is that on 91 or 94? (some stations here have a 94 option)
This is on 98 octane (equivalent to 93-94 in US) . The particular gas (Gull) is actually 95 octane with 10% ethanol added to get it to 98 vs say BP98 which has no ethanol . Have talked to several tuners here and they agree it's the best pump gas we have here in NZ.
We actually have one station selling 100 octane here which gets that rating through the use of olefins . It's utter crap for high performance use ....don't ask how I know !
Sorry catching up on the thread this morning, MOI, what does this stand for? Trying to follow the g25 vs g30 debate but not understanding.
G30 AR 0.83 vs G25 AR 0.92
Spoolup
MOI - G25 wins due to smaller turbine
Turbine efficiency - G30 wins........... probably , although no figure given for G25 .... generally turbines get more efficient as they get bigger
Turbine flow - G30 wins being slightly tighter in PR range we will operate in
End result ... bugger all difference but probably slightly favoring the G25
EMAP
Turbine efficiency - G30 wins
Turbine flow- G25 wins
End result ... bugger all difference but probably slightly favoring the G25
That's how I see it ... but with the G30 we will also have the AR1.01 option that blows the 25 out of the water for EMAP. Plus ...I've already tried the G30 and daym that G25 turbine looks soooooo small it scares me ! lol
not quite, what will ultimately matter wrt efficiency is corrected mass flow rate
so the G30 may have more efficiency as it approaches the peak flow rate at higher Pr values, but it's flow rate with the 0.83 housing is lower than the 0.92 G25 housing as demonstrated in the graph above. At question is what the efficiency difference is and where and how close do they become to each other once mass flow is corrected.
That’s what my post is referring to, because there’s an 8 - 10% flow difference in favor of the G25, so the efficiency difference of the G30 housing has to be quite large to overcome that. Which it can’t do at the very low end and will be slower to hit peak boost as the G25, but likely will at the high rpm with less emap and/or more peak rpm range, etc..
Because that efficiency difference is greater and more in the G30 housings favor at high Pr than low, but we’re likely only going to see around 2.3 Pr peak or so on a Renesis unless you intend to really cram it in early with high boost at low rpm and then taper that off at high rpm. That seems unlikely since nobody here is that sophisticated and/or willing to spend the money to bring it into play with the means to have full-on boost x rpm x gear strategy, electronic wastegate, etc. … or at least not yet.
So imo this shows itself on a reciprocating piston engine application, because if you’ve been following the G25-660 results it comes up a bit shorter than expected because they’re up in the 3.0+ Pr range. So the turbine not only becomes less efficient there, the peak compressor flow is also lowering due to how the map tapers back. Whereas peak -660 compressor flow is at approx 2.55 Pr. So imo this plays out more in favor to a 2-rotor. More so with an earlier 13B with the divided 0.92 T4 housing piped in from each exhaust port separately.
Not everyone will agree, but I think that T4 housing also has an advantage on a Renesis too, but am willing to let it play out rather than banter on for or against it.
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just like when somebody was trying to put a G30 0.83 housing in your lap.
but I also agree that peak power is in the G30’s favor. With a 7000-7500 rpm limit in the sub-400 whp range on a street car I’m not so afraid of the little guy … but then I’m also thinking E85 fuel etc as well. Otherwise I see it being what everyone had wished the Greddy to be if shooting for the 300-350 whp range. The smaller packaging always helps on a Renesis too.
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spdracerUT : Putting the 900 compressor (76mm exducer) on the G30 turbine (60mm inducer) will result in lower turbine efficiency due to a poor blade speed ratio. Yes, the compressor can flow well, but it's paired with a turbine that is too small for optimum performance of the total package. So even though the G35 turbine flows more in the same A/R housing, it'll have much better efficiency resulting in similar spool-up with less back pressure,
A G25 with 0.92 A/R flows about the same as a G30 in 0.83 A/R which flows about the same as a G35 in 0.61 A/R. Do you believe a G25-900 would be a good pairing? That seems to be what you're implying based on looking strictly at turbine flow. I can tell you right now that a G25-900 pairing would result in a really poor blade speed ratio and therefore abysmal turbine efficiency making for a really poor performing turbo. So yes, the compressor and turbine wheel diameter matching does matter.
I actually think a G30-660 in the 0.83 A/R could spool faster AND make more power than the G25-660 in the 0.92 A/R.
Found this in a convo Team was having over on the 7 forum . Don't know who the guy is but he seemed quite experienced .
except you didn’t include my counter reply, which the debate ended at. It being also what was discussed here in the more recent comments above when we were having more or less the same conversation.
I strongly disagree with some of that, but the one good point he made was that we don’t have turbine efficiency maps. So in the end all that matters is the corrected turbine flow once efficiency is factored in. Which again was already discussed further above here as well as on that thread. The G25 0.92 turbine has more flow to counter against the efficiency difference, but I already conceded that the G30 0.83 is closing in and going to have less emap the far right extreme of the compressor map. It’s never been my assertion to operate the G25 there, but more in the 300 - 400 whp range.
I’m not discounting his experience as was stated in that other thread as well, but by his own admission it was based on earlier Garrett turbos and not the G series. Below a graphic demonstration of why I disagree with him with the following illustrations below. As I stated somewhere on the forum not too long ago, imo the G30-900 makes more sense to me than either the G30-660/770. The 900 will spool a bit slower and the turbine is going to start choking up some to the far right of the map on a rotary engine, at which point the G35-900 makes more sense, but it’s going to be very strong in the 400ish - 525ish rotary whp range rather than running either the 660 or 770 out to the far right of their maps.
I didn’t bother doing this with the G30-600 because it doesn’t interest me over the G25-660; which is a comparison of efficiency island width/range between the 70% efficient points:
except you didn’t include my counter reply, which the debate ended at. It being also what was discussed here in the more recent comments above when we were having more or less the same conversation. .
No need to include your answers as it's just the same argument we were having. His point about blade speed ratios and the effect that has on turbine efficiency ,on the other hand, was something I had neglected to mention. You seem to think it doesn't matter, whereas I've actually seen that effect in some of my experimentation and do think it matters.
Also : you seem to have this notion that the efficiency of the turbine is somehow accounted for in the flow rate. It isn't ......... and that's why it's listed separately on turbine maps. Just play with flow and efficiency on the matchbot software and you will see what effect both have on the outcome.
no, it matters, but again all that ultimately matters is the corrected flow where all that comes together. Which also again, the 0.92 has the indicated map flow advantage that will serve to offset that. And it will mostly come into play on the top end as the 0.83 starts to close the gap.
Not sure why it needs to keep being repeated? When the turbo is running out to the far right of the map that’s generally going to be where that always happens. G25 vs G30 with the 660 compressor or G30 vs G35 with the 900 compressor.
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Ok ...it's just some of your comments led me to believe you thought that corrected flow was the end all parameter for the turbine side.
The thing is we actually don't know what the efficiency number is for any of these combinations. That's because they only ever give a maximum number . To try and give the numbers for all combinations of exhaust housing, Pr and flow rate would be a ridiculously complex exercise and 99% of those looking at that info wouldn't have any idea how to interpret it anyway.
That's where spdracers comments are valuable as it sounds like he has seen and understood the nuances that exist in this area.
Edit : for interest , I had a play in matchbot to try and get a sense of how turbine efficiency vs turbine flow affected emap.
So (and this is just approximate) the g25 0.92 outflows the g30 0.83 by 1 lb/min in the range I'm operating the turbo. To get the same difference in EMAP via turbine efficiency would take a 4-5% difference in efficiency.
except you didn’t include my counter reply, which the debate ended at. It being also what was discussed here in the more recent comments above when we were having more or less the same conversation.
I strongly disagree with some of that, but the one good point he made was that we don’t have turbine efficiency maps. So in the end all that matters is the corrected turbine flow once efficiency is factored in. Which again was already discussed further above here as well as on that thread. The G25 0.92 turbine has more flow to counter against the efficiency difference, but I already conceded that the G30 0.83 is closing in and going to have less emap the far right extreme of the compressor map. It’s never been my assertion to operate the G25 there, but more in the 300 - 400 whp range.
I’m not discounting his experience as was stated in that other thread as well, but by his own admission it was based on earlier Garrett turbos and not the G series. Below a graphic demonstration of why I disagree with him with the following illustrations below. As I stated somewhere on the forum not too long ago, imo the G30-900 makes more sense to me than either the G30-660/770. The 900 will spool a bit slower and the turbine is going to start choking up some to the far right of the map on a rotary engine, at which point the G35-900 makes more sense, but it’s going to be very strong in the 400ish - 525ish rotary whp range rather than running either the 660 or 770 out to the far right of their maps.
I didn’t bother doing this with the G30-600 because it doesn’t interest me over the G25-660; which is a comparison of efficiency island width/range between the 70% efficient points:
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Team, The map you’re showing for G30-900 has 1.06 A/R were you referring to that A/R for 525’ish range hp turbine efficiency/flow?
it’s bad enough I have to keep repeating my words, but now Brettus repeats my words like he’s making a point against me.
You don’t have a race car where you’re hammering it at max rpm for 20 or 30 minutes continuously. Running out there for a bit is what a street car typically does. That’s not what would generally be called “where it operates”. Where most street cars operate is in the range of where the G25 has an 8-10% flow advantage that’s being glossed over. I’d argue that the G30-770 is the better choice for 400+ over the 660, because then both compressor and turbine efficiency are coming into play. That’s why I see the G30-660 as sort of the most odd man out of the three G30 compressors.
Yet if you actually compare the maps above you can see the 900 is almost right on top of the 770 on the right, but has a 10+% compressor efficiency advantage on the right. Seems like you’re kind of mixed up or confused B, which is why I don’t think you’re seeing the overall points where that guy is off. Because I’m not discounting his experience, but his experience wrt the 900 compressor is not correct imo due to be based on the previous less efficient versions. It’s just what the marked up map above indicates and I already conceded the G30 is closing in and passing the G25 at the very top end as Pr increases, at least 4 or 5 times now.
The thing is you haven’t been operating much over 2.1 Pr or so. When you go higher you’ll be ramming it over all the way to the far right which I wouldn’t want to do with either the G25 0.92 or G30 0.83 and a 660 compressor. The bottom line is the 660 with either the G25 0.92 or G30 0.83 is too small for 400+ on a 2 rotor imo. Not saying you won’t get there, and I agree the G30 is better for that, but the G30 having 3 different compressor options allows for a pretty good analysis that to me indicates the 660 and 770 could just be eliminated. The only reason to have them is for tight fitment applications where the 900 compressor won’t fit. The compressor efficiency suffers on both compared to the 900, but for a competition car and/or 550+ whp then I’d move to the G35-900 instead.
So on those maps above, the 1.06 housing is just my preference that was listed in the text description, having formulated those for an REW application. The lines only indicate where 70% starts on the left and then ends on the right for the two boost pressures and what the lbs/min width or range is between those two points. Which helps define how efficient overall a compressor is. Which again at 20 psig, the the efficiency/flow is really close between the 770 and 900 on the left, but on the right the 900 compressor leaves it in the dust @ 70 lbs/min as the 770 is on it’s last dying breath. Since the turbine is the same, then that compressor efficiency difference is what separates them and is why I’m saying the 660 and 770 aren’t that interesting to me.
So now Brettus, rather than a 660 with 0.83, think about a 900 with the 0.83 instead. It will spool a bit slower due to the larger 900 compressor and a bit less compressor efficiency initially, then the compressor will be coming on hard pumping more corrected airflow for the same turbine load. So if that’s where you “operate”, then you really need the 900 and the much higher compressor efficiency from 50 - 60 lbs/min. Which illustrates my point. Both compressor and turbine efficiency matter. So then if you’re experience is from a generation or two prior, and that’s the basis for trying to make assessment on the new G-series using those old efficiency references, then you might possibly be missing why they moved to a new generation turbo design in the first place. .
Again, study the 900 compressor map compared to the other two.
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Interesting discussion, I've been trying to figure out where all this fits for a Renesis with under 400whp and track use, looking for reliability and low EMAP, which means keeping it below 14 psi.
Sounds like there would be different turbo options depending on what application you have, street car with a G25 for quick spool, G30 for a track car for more reliability under continuous high loads.
Reason for asking this is that i'm using the MM GT3071R kit which currently has been pretty reliable albeit at a somewhat reasonably low boost of 10 to 12 psi. Looking to optimise my setup for track use while keeping it a low mount.
Because you aren't getting it .................... that's why!
That 8% you talk about as the difference in flow is not going to matter ... the G30 0.83 will perform just as well as the G25 0.92 because better turbine efficiency of the 30 will largely make up for more turbine flow of the 25 and EMAP will be so close it wont matter. It pains me to even discuss this because we are just nit picking about a tiny differences.
Also , I have no interest in the 770 or the 900 because...........................not only will they not fit in my configuration, but they will have slower spoolup and the added flow they provide isn't necessary on a Renesis. Your analysis would be useful over on the rx7 forum but here ...not so much.
Sounds like there would be different turbo options depending on what application you have, street car with a G25 for quick spool, G30 for a track car for more reliability under continuous high loads.
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That's why the 30 is the much better choice. The 0.83 can be for street cars wanting quickest spool and the 1.01 for track cars wanting lower emap. You don't have to change out the whole turbo to achieve either.
08-01-2021, 07:30 PM
