Twin 16g setup - Theoretical Question
09-15-2011, 10:28 AM
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Twin 16g setup - Theoretical Question
I've seen alot of 18g and 20g kits on the VQ engines and I know that they are a fairly popular build. Just out of curiosity I search around quite a bit to see if anyone had tried a twin 16g setup and I was unsuccessful.
Naturally I understand if people rant "why would you be interested in smaller turbos!?" I am wondering about a twin 16g setup more in theory than in actually building one, but here was my line of (potentially flawed) thinking.
About a decade ago I started delving into forced induction with 4g63 engines, and through that I have had hands on experience with 16g, 18g, ect.. series of turbos. And while I have had a g35 for years and have spent inordinate amounts of time reading on forums, I do not claim to know all the intricacies of FI on the VQ engine.
It is my understanding that bigger turbos are more effective at producing even low psi numbers because they can compress the air more easily than a smaller turbo and therefore generate less heat. Yet in exchange the bigger turbo will take longer to spool up.
Now, in order to balance the trade off between lag and efficiency one would assume that the best turbo would be the smallest one available that was still efficient at the desired psi (i.e. not turned up too high causing it to become an awesome hairdryer).
I see lots of people making big numbers on twin 18g and 20g setups and others claiming that 20gs are good to 1000hp. While I see others running 13 & 16psi (still making great numbers). These larger turbos lend to future potential to vastly increase power and this adjustability is a major benefit, but..
On the 4g63 the 16g turbos are more than capable of handling boost in the 13-16psi range.
If someone was trying to make less than five or six hundred horsepower with minimal lag on the VQ engine, why wouldnt a couple 16gs be capable?
I understand that people have been working on these cars for a long time and that if 16gs were advisable someone would probably make a kit. But why are the 16gs not used? Is the spool up difference in a twin turbo setup negligible between the 16g and 18g? Or do these engines rev high enough naturally that noone is really worried about loosing a 500rpms on the very bottom end?
Naturally I understand if people rant "why would you be interested in smaller turbos!?" I am wondering about a twin 16g setup more in theory than in actually building one, but here was my line of (potentially flawed) thinking.
About a decade ago I started delving into forced induction with 4g63 engines, and through that I have had hands on experience with 16g, 18g, ect.. series of turbos. And while I have had a g35 for years and have spent inordinate amounts of time reading on forums, I do not claim to know all the intricacies of FI on the VQ engine.
It is my understanding that bigger turbos are more effective at producing even low psi numbers because they can compress the air more easily than a smaller turbo and therefore generate less heat. Yet in exchange the bigger turbo will take longer to spool up.
Now, in order to balance the trade off between lag and efficiency one would assume that the best turbo would be the smallest one available that was still efficient at the desired psi (i.e. not turned up too high causing it to become an awesome hairdryer).
I see lots of people making big numbers on twin 18g and 20g setups and others claiming that 20gs are good to 1000hp. While I see others running 13 & 16psi (still making great numbers). These larger turbos lend to future potential to vastly increase power and this adjustability is a major benefit, but..
On the 4g63 the 16g turbos are more than capable of handling boost in the 13-16psi range.
If someone was trying to make less than five or six hundred horsepower with minimal lag on the VQ engine, why wouldnt a couple 16gs be capable?
I understand that people have been working on these cars for a long time and that if 16gs were advisable someone would probably make a kit. But why are the 16gs not used? Is the spool up difference in a twin turbo setup negligible between the 16g and 18g? Or do these engines rev high enough naturally that noone is really worried about loosing a 500rpms on the very bottom end?
09-15-2011, 11:01 AM
#2
Sorry a little OT but thats a cool username. Wish I thought of it.
Anyway I owned a 2g DSM for a few years with a 16g running about 20psi or so. I see what your asking here and I would like to know as well. The only thing I can think of is running a 16g on a factory turbo 4 is way different than running twins on a higher compression 6. The size difference between a 2.0 4g63 and a 3.5 vq35 de/hr is pretty big. Maybe since the 4g63 can spool a 16g so well, even twins may be a waste on this motor. Maybe someone with twin 18g turbos can chime in on how their boost kicks in.
Anyway I owned a 2g DSM for a few years with a 16g running about 20psi or so. I see what your asking here and I would like to know as well. The only thing I can think of is running a 16g on a factory turbo 4 is way different than running twins on a higher compression 6. The size difference between a 2.0 4g63 and a 3.5 vq35 de/hr is pretty big. Maybe since the 4g63 can spool a 16g so well, even twins may be a waste on this motor. Maybe someone with twin 18g turbos can chime in on how their boost kicks in.
09-15-2011, 11:13 AM
#4
18G's hardly lag at all when properly setup.
Why limit yourself for future plans or limit room to grow to hit full boost at 2800rpm's instead of 3200rpm's? It makes no sense IMO.
My 18G's spool fast, make monstrous mid range and pull hard up top. Why change a proven recipe?
Why limit yourself for future plans or limit room to grow to hit full boost at 2800rpm's instead of 3200rpm's? It makes no sense IMO.
My 18G's spool fast, make monstrous mid range and pull hard up top. Why change a proven recipe?
09-15-2011, 12:04 PM
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^ word.
Wouldn't the smaller BB turbos like with the cheaper HKS and GTM kits compare to a 16g journal turbo? Also with a VQ you have a minimum of 3.5 liter displacement which is huge compared to a 4G, so any smaller wouldnt neccesarely be better.
I had a GST before the Z, but they are completely different cars. Maybe better compared with an SR20.
Wouldn't the smaller BB turbos like with the cheaper HKS and GTM kits compare to a 16g journal turbo? Also with a VQ you have a minimum of 3.5 liter displacement which is huge compared to a 4G, so any smaller wouldnt neccesarely be better.
I had a GST before the Z, but they are completely different cars. Maybe better compared with an SR20.
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09-15-2011, 02:05 PM
#8
It is an interesting observation, and deffinately has some merit to it. alot of guys running 18G's seem to be running power and boost levels that the 16's could probably provide. it would be an interesting experiment to see.
Oh and why fix it if it ain't broke you ask? why not, that's how you learn new things. what you accept as convention today, was a "crazy new idea" in it's time.
Oh and why fix it if it ain't broke you ask? why not, that's how you learn new things. what you accept as convention today, was a "crazy new idea" in it's time.
09-15-2011, 02:19 PM
#9
most TT Z owners are on stock blocks. doesnt matter how much power you can make. the rods are the physical limitations. Also, most people only run pump gas. Again you are bumping against the physical limitations.
16Gs could do about the same for sure. Would just have to run the pump gas tune more aggressive to make the same power as a 18G kit.
You'd def want the biggest A/R you could get for those 16G though.
16Gs could do about the same for sure. Would just have to run the pump gas tune more aggressive to make the same power as a 18G kit.
You'd def want the biggest A/R you could get for those 16G though.
09-16-2011, 09:05 AM
#12
ya this guy
https://my350z.com/forum/forced-indu...o-project.html
basically made a TT kit off the stock manifolds. pretty much same thing that boosted performance has been talking about doing, although with much nicer welds
https://my350z.com/forum/forced-indu...o-project.html
basically made a TT kit off the stock manifolds. pretty much same thing that boosted performance has been talking about doing, although with much nicer welds
09-16-2011, 04:53 PM
#14
IMO it would work and boost would hit real nice for such cheap/easy to obtain turbos (well that does depend on if you buy 2nd hand mitsu turbos or greeedy turbos obviously), but it would probably get kinda chokey up top. If you only want to stay on stock block and you can do the work/save a bunch doing it, it's worth trying. But, you are probably better off fitting larger turbos than that. I mean if you are going to do your own custom setup you might as well make it 'worth the time' with some bigger turbos. I'm actually trying to get rid of a set of turbos (precision 3431e) because I wanted to do a custom twin setup. Changed my mind and going bigger single for simplicity.
09-16-2011, 06:38 PM
#15
I don't see the need to fab a TT kit with 16G turbos to achieve marginally quicker spool when there are other more practical options available that would achieve the same goal.
However... if the 16G can be a direct drop-in swap with an 18G kit without need for further (or at least without signifcant PITA) modifications, then that option would be a no brainer. One could sell the 18G's, or hold on to them for when they want more power. Can anyone advise whether a drop-in swap is possible with the existing Greddy kit? Or would it require modifications to the kit?
