View Poll Results: Best compressor wheel choice for GT30 turbine?
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Best compressor wheel choice for GT30 turbine?
Nov 13, 2011, 05:32 AM
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Best compressor wheel choice for GT30 turbine?
Hello Everybody,
I know this isn't an SR20-specific forum, but owing to the general similarity of both engines and the fact that the evo community is one of the most knowledgeable ones on the internet I figured I might as well ask here, so for the purpose of this discussion lets assume I'm talking about a stock evo 9 engine (with mivec) engine running no more than 23psi of boost on pump + meth...
I'm building an S14 SR20, with a forged internals and a 1mm overbore for 2048cc, along with HKS 264 Step cams, a short-runner Greddy intake manifold, and a ported head. I also have a blown HKS 3037 with a .87 A/R T2 flanged turbine housing, hence the requirement for a GT30 turbine. I want a well-rounded setup that does everything reasonably well, running 93oct pump gas +meth and no more than 23psi. i.e. I'd like to end up making 480-500bhp at the crank while making 300lb-ft of torque as early as possible in the rev range, hopefully not much later than 4000rpm... Here are my options below, from smallest to biggest:
- FP HTA73 compressor wheel upgrade + brand new GT30 CHRA in a disco potato 3" inlet 0.60A/R comp cover. 52.5mm inducer, 73.0mm exducer
- GTX3071 purchased brand new outright, 54.1mm inducer, 71.4mm exducer
- FP HTA76 compressor wheel upgrade + brand new GT30 CHRA in a T04S 0.70A/R cover. 54.8mm inducer, 76.2mm exducer
- Or I could stick with either a plain-jane GT3071 or GT3076 and call it a day
What do you think of the above choices, and what would your pick(s) be? Is the difference in spool & transient response worth it to merit going with the smallest compressor wheel, or would I be holding back power unnecessarily?
I've seen several dyno comparisons that indicate that an HTA76 upgrade is worth 300-400rpm faster spool with an extra 10-15bhp or so up top compared to a regular 3076, all else being equal. I wonder how much faster the HTA73 would spool compared to its bigger brother, and how much less power it would make... It is worth mentioning that the HTA turbos come with a 1-year warranty whereas the Garrett GTX doesn't... Keep in mind we're using the 0.87 A/R T2 HKS housing, which works out having the same cross sectional area as a 0.74 A/R T3 housing and thus should be good for ~22lb/min of corrected turbine flow.
Let me know what you think, and I'd really appreciate hearing your thoughts on my setup.... Thanks!
I know this isn't an SR20-specific forum, but owing to the general similarity of both engines and the fact that the evo community is one of the most knowledgeable ones on the internet I figured I might as well ask here, so for the purpose of this discussion lets assume I'm talking about a stock evo 9 engine (with mivec) engine running no more than 23psi of boost on pump + meth...
I'm building an S14 SR20, with a forged internals and a 1mm overbore for 2048cc, along with HKS 264 Step cams, a short-runner Greddy intake manifold, and a ported head. I also have a blown HKS 3037 with a .87 A/R T2 flanged turbine housing, hence the requirement for a GT30 turbine. I want a well-rounded setup that does everything reasonably well, running 93oct pump gas +meth and no more than 23psi. i.e. I'd like to end up making 480-500bhp at the crank while making 300lb-ft of torque as early as possible in the rev range, hopefully not much later than 4000rpm... Here are my options below, from smallest to biggest:
- FP HTA73 compressor wheel upgrade + brand new GT30 CHRA in a disco potato 3" inlet 0.60A/R comp cover. 52.5mm inducer, 73.0mm exducer
- GTX3071 purchased brand new outright, 54.1mm inducer, 71.4mm exducer
- FP HTA76 compressor wheel upgrade + brand new GT30 CHRA in a T04S 0.70A/R cover. 54.8mm inducer, 76.2mm exducer
- Or I could stick with either a plain-jane GT3071 or GT3076 and call it a day
What do you think of the above choices, and what would your pick(s) be? Is the difference in spool & transient response worth it to merit going with the smallest compressor wheel, or would I be holding back power unnecessarily?
I've seen several dyno comparisons that indicate that an HTA76 upgrade is worth 300-400rpm faster spool with an extra 10-15bhp or so up top compared to a regular 3076, all else being equal. I wonder how much faster the HTA73 would spool compared to its bigger brother, and how much less power it would make... It is worth mentioning that the HTA turbos come with a 1-year warranty whereas the Garrett GTX doesn't... Keep in mind we're using the 0.87 A/R T2 HKS housing, which works out having the same cross sectional area as a 0.74 A/R T3 housing and thus should be good for ~22lb/min of corrected turbine flow.
Let me know what you think, and I'd really appreciate hearing your thoughts on my setup.... Thanks!
Nov 13, 2011, 10:38 AM
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I guess another way of looking at this would be as follows, there are two schools of thought on this subject;
- Theory states that going for the smaller of two compressor wheel options for a given turbine wheel would shift the powerband to the left, much like advancing intake cam gear timing, as well as improving transient response and respool, on account of the smaller wheel's lower rotational inertia, but this is probably a minor effect. Turbine efficiency should also benefit a small amount due to better tip speed matching between the compressor and turbine...
- On the other hand I've seen experimental evidence that suggests little to no spool loss (and a substantial power gain) in going with the larger of two compressor choices, for instance PTE 5857 vs 5557, Perrin's GTX3076 vs GT3076 testing, even a certain HTA82 vs HTA86 test on evom, where the latter only lost 70rpm of spool on the dyno compared to the former, and made a bunch more whp... Granted dyno's can't/don't measure transient response, but its still food for thought. I've seen this to be true both at high boost (when pushing the limits of the smaller compressor), and at more moderate boost settings, where you would think the smaller compressor is close to its sweet spot, and I can't figure out why that is...
Discuss...
- Theory states that going for the smaller of two compressor wheel options for a given turbine wheel would shift the powerband to the left, much like advancing intake cam gear timing, as well as improving transient response and respool, on account of the smaller wheel's lower rotational inertia, but this is probably a minor effect. Turbine efficiency should also benefit a small amount due to better tip speed matching between the compressor and turbine...
- On the other hand I've seen experimental evidence that suggests little to no spool loss (and a substantial power gain) in going with the larger of two compressor choices, for instance PTE 5857 vs 5557, Perrin's GTX3076 vs GT3076 testing, even a certain HTA82 vs HTA86 test on evom, where the latter only lost 70rpm of spool on the dyno compared to the former, and made a bunch more whp... Granted dyno's can't/don't measure transient response, but its still food for thought. I've seen this to be true both at high boost (when pushing the limits of the smaller compressor), and at more moderate boost settings, where you would think the smaller compressor is close to its sweet spot, and I can't figure out why that is...
Discuss...
Nov 13, 2011, 12:18 PM
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I'm aware that the hta76 is a great choice, but what if you're not running typical evo levels of boost or taking full advantage of the HTA76 compressor, might it not be prudent to go with something a little bit smaller, or are the spool/transient benefits not worth it?
Nov 13, 2011, 12:34 PM
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Just to put things into perspective, there's only a 2.3mm difference in inducer diameter and a ~3lb/min difference in flow rate between the smallest and biggest of the billet compressor wheels listed above...
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Nov 13, 2011, 12:38 PM
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Because you have the smaller turbine housing you will need to run more boost to hit your power goals. I would suggest either the GTX or HTA76; they both flow just short of 60lb/min and will maintain compressor efficiency at the higher boost levels. The standard cast compressor wheels wont cut it, so skip either of those options.
Nov 13, 2011, 12:44 PM
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I would nix the gt series from the list. I guess it boils down to whether that single 11 blade wheel can out perform the split 7 blade on the low side of the comp map. the hta 73 and 76 are heavy hitters down low without having to battle surge. not a lot of results in on the gtx
Nov 13, 2011, 12:53 PM
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I only included the gt3071r and gt3076r for the sake of completeness, I'm well aware that the billet turbos are better in every respect bar cost. Another advantage of the HTA turbos is that they come with a 1-year warranty whereas the GTX doesn't... All that's left is to figure out which one of the three billet wheels will give us the most area under the curve/be the most fun to drive given the application above...
Nov 13, 2011, 12:59 PM
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I've been playing around with BW's Matchbot app, and here is a guesstimate of my setup using the HTA73 comp wheel and ballpark estimates/best guesses of everything else:
http://www.turbodriven.com/performan...6_wrsin=92044&
HTA73 yields a -7psi pressure balance (backpressure > boost pressure) at 7500rpm, which I think is very reasonable... The Larger GTX3071 ends up with roughly 2psi less backpressure all else being equal... Wonder how much power this translates to...
http://www.turbodriven.com/performan...6_wrsin=92044&
HTA73 yields a -7psi pressure balance (backpressure > boost pressure) at 7500rpm, which I think is very reasonable... The Larger GTX3071 ends up with roughly 2psi less backpressure all else being equal... Wonder how much power this translates to...
Last edited by hydra; Nov 18, 2011 at 11:44 PM.
Nov 13, 2011, 03:55 PM
#12
Based on your power goals, the GTX3071R seems to be the logical choice. You'll fork out $1100 for a new GT3071R CHRA and then spend another $600 + shipping to get the HTA73 upgrade. As an FYI, they also do an HTA71 upgrade that is like 54 pounds/min.
Compare that to $1400 for the GTX3071R CHRA with Garrett reliability and off-the-shelf ordering. I'm sure you can get them for less as well if you have a friend with a Garrett hookup, or even just shopping around. That was just ATP Turbo's price.
They are going to perform very similarly at the power level you are looking for with the GTX just saving you money. You aren't going to push it hard enough to even see an airflow or spool difference. If FP can do a new HTA71/73/76 CHRA for $1400, then you would be on to something. Hell, they probably can match the GTX prices, I have to assume they can or their HTA stuff doesn't seem that great any more as far as Garrett upgrades go.
As far as dyno testing to show the difference in spool between a GT3071R and a GT3076R, it's a waste of time. Wheel size mismatches will not show up on dyno charts IMO. I've driven and tuned a badly mismatched turbo setup with WAY too much compressor for the turbine. If you rolled into the throttle at 2000 RPM in 3rd, it would hit full boost by like 3000 RPM. Mash the throttle in 1st or 2nd gear though and it was more laggy then a GT35R. Transient response WILL NOT show up on a dyno chart. Just my experience, but GT30 vs GT35, the difference on a dyno is only about 200-300 RPM. The difference on the street is massive with the GT30 easily pulling a couple cars on the hit (all else being equal). The GT35 quickly gets it back and then bus-lengths more on top, but on actual response, the GT30 is noticeably more responsive despite the minor difference in dyno charts.
Compare that to $1400 for the GTX3071R CHRA with Garrett reliability and off-the-shelf ordering. I'm sure you can get them for less as well if you have a friend with a Garrett hookup, or even just shopping around. That was just ATP Turbo's price.
They are going to perform very similarly at the power level you are looking for with the GTX just saving you money. You aren't going to push it hard enough to even see an airflow or spool difference. If FP can do a new HTA71/73/76 CHRA for $1400, then you would be on to something. Hell, they probably can match the GTX prices, I have to assume they can or their HTA stuff doesn't seem that great any more as far as Garrett upgrades go.
As far as dyno testing to show the difference in spool between a GT3071R and a GT3076R, it's a waste of time. Wheel size mismatches will not show up on dyno charts IMO. I've driven and tuned a badly mismatched turbo setup with WAY too much compressor for the turbine. If you rolled into the throttle at 2000 RPM in 3rd, it would hit full boost by like 3000 RPM. Mash the throttle in 1st or 2nd gear though and it was more laggy then a GT35R. Transient response WILL NOT show up on a dyno chart. Just my experience, but GT30 vs GT35, the difference on a dyno is only about 200-300 RPM. The difference on the street is massive with the GT30 easily pulling a couple cars on the hit (all else being equal). The GT35 quickly gets it back and then bus-lengths more on top, but on actual response, the GT30 is noticeably more responsive despite the minor difference in dyno charts.
Last edited by 03whitegsr; Nov 13, 2011 at 04:04 PM.
Nov 13, 2011, 10:59 PM
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I only included the gt3071r and gt3076r for the sake of completeness, I'm well aware that the billet turbos are better in every respect bar cost. Another advantage of the HTA turbos is that they come with a 1-year warranty whereas the GTX doesn't... All that's left is to figure out which one of the three billet wheels will give us the most area under the curve/be the most fun to drive given the application above...
Nov 14, 2011, 03:34 AM
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Based on your power goals, the GTX3071R seems to be the logical choice. You'll fork out $1100 for a new GT3071R CHRA and then spend another $600 + shipping to get the HTA73 upgrade. As an FYI, they also do an HTA71 upgrade that is like 54 pounds/min.
Compare that to $1400 for the GTX3071R CHRA with Garrett reliability and off-the-shelf ordering. I'm sure you can get them for less as well if you have a friend with a Garrett hookup, or even just shopping around. That was just ATP Turbo's price.
They are going to perform very similarly at the power level you are looking for with the GTX just saving you money. You aren't going to push it hard enough to even see an airflow or spool difference. If FP can do a new HTA71/73/76 CHRA for $1400, then you would be on to something. Hell, they probably can match the GTX prices, I have to assume they can or their HTA stuff doesn't seem that great any more as far as Garrett upgrades go.
As far as dyno testing to show the difference in spool between a GT3071R and a GT3076R, it's a waste of time. Wheel size mismatches will not show up on dyno charts IMO. I've driven and tuned a badly mismatched turbo setup with WAY too much compressor for the turbine. If you rolled into the throttle at 2000 RPM in 3rd, it would hit full boost by like 3000 RPM. Mash the throttle in 1st or 2nd gear though and it was more laggy then a GT35R. Transient response WILL NOT show up on a dyno chart. Just my experience, but GT30 vs GT35, the difference on a dyno is only about 200-300 RPM. The difference on the street is massive with the GT30 easily pulling a couple cars on the hit (all else being equal). The GT35 quickly gets it back and then bus-lengths more on top, but on actual response, the GT30 is noticeably more responsive despite the minor difference in dyno charts.
Compare that to $1400 for the GTX3071R CHRA with Garrett reliability and off-the-shelf ordering. I'm sure you can get them for less as well if you have a friend with a Garrett hookup, or even just shopping around. That was just ATP Turbo's price.
They are going to perform very similarly at the power level you are looking for with the GTX just saving you money. You aren't going to push it hard enough to even see an airflow or spool difference. If FP can do a new HTA71/73/76 CHRA for $1400, then you would be on to something. Hell, they probably can match the GTX prices, I have to assume they can or their HTA stuff doesn't seem that great any more as far as Garrett upgrades go.
As far as dyno testing to show the difference in spool between a GT3071R and a GT3076R, it's a waste of time. Wheel size mismatches will not show up on dyno charts IMO. I've driven and tuned a badly mismatched turbo setup with WAY too much compressor for the turbine. If you rolled into the throttle at 2000 RPM in 3rd, it would hit full boost by like 3000 RPM. Mash the throttle in 1st or 2nd gear though and it was more laggy then a GT35R. Transient response WILL NOT show up on a dyno chart. Just my experience, but GT30 vs GT35, the difference on a dyno is only about 200-300 RPM. The difference on the street is massive with the GT30 easily pulling a couple cars on the hit (all else being equal). The GT35 quickly gets it back and then bus-lengths more on top, but on actual response, the GT30 is noticeably more responsive despite the minor difference in dyno charts.
It just so happens that in my case, the cost difference is only $40ish, and so isn't really a consideration here, hence the difficulty in picking a compressor... Having the GTX available off the shelf is definitely a plus though. I also noticed that FWIW the GTX is noticeably less efficient than the 3071 and 3076 (and probably either of the HTA turbos) at sub 30lb/min flow rates at the boost pressure I'd be running...
Last edited by hydra; Nov 14, 2011 at 03:58 AM.
Nov 14, 2011, 04:25 AM
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It just so happens that in my case, the cost difference is only $40ish, and so isn't really a consideration here, hence the difficulty in picking a compressor... Having the GTX available off the shelf is definitely a plus though. I also noticed that FWIW the GTX is noticeably less efficient than the 3071 and 3076 (and probably either of the HTA turbos) at sub 30lb/min flow rates at the boost pressure I'd be running...
If you went with the GTX 3076R which turbine housing would you choose for your application?
