Which turbos for a TT setup on a stock VH45?

[Stinky]

Lets say I were creating an intercooled twin turbo vh45. The motor would be stock compression so boost would be limited to probably no more than 10psi and might run closer to 6psi the majority of the time. (assuming detonation is not an issue) I'm looking for something cost effective and preferably internally gated. Used or new is fine. My main concern is that the turbos spool relatively quickly (before 2500 rpm) and they dont run out of puff at high rpms. At this point I'm thinking about using stock t3s from the early model z31s (200hp@6psi on a 3.0l V6). Other suggestions, comments?

[SuperHatch]

Lets say I were creating an intercooled twin turbo vh45. The motor would be stock compression so boost would be limited to probably no more than 10psi and might run closer to 6psi the majority of the time. (assuming detonation is not an issue) I'm looking for something cost effective and preferably internally gated. Used or new is fine. My main concern is that the turbos spool relatively quickly (before 2500 rpm) and they dont run out of puff at high rpms. At this point I'm thinking about using stock t3s from the early model z31s (200hp@6psi on a 3.0l V6). Other suggestions, comments?

The most responsive low boost internally gated turbo I can think of would be a T28. Think about it, you've got two 2.25L engines that each need some boost. A T28 on a 2.0L SR is fairly responsive and will easily hold 6-10psi until redline.

[elwesso]

the budget money turbo would probably be a T28 from a SR or RB...

[Guishnu]

My vote would be two S14 SR20DET T28 turbo's. I would tend to avoid RB20 or 25 det units due to the ceramic exhaust wheel.

[mtcookson]

Some that come to mind... the Mitsubishi "small" 16G, 16G6, and 20G should fit pretty well... but I'll go very, very in depth below and find out exactly...

(Note: When I say "surge @ x RPM" that means that is slightly to the right of the "surge line" where the turbo would surge on the VH45 basing off of VE's of 70%, 80%, and 90% at that exact RPM. The numbers are just to give an idea of what it could be if you were able to spool the particular turbo that fast and if the VE was at that point.)

16G "small" @ 1.4 PR/5.88 PSI will surge at:60% VE - ~2,400 RPM70% VE - ~2,100 RPM80% VE - ~1,800 RPM90% VE - ~1,600 RPM

16G "small" @ 1.68 PR/10 PSI will surge at:60% VE - ~2,800 RPM70% VE - ~2,400 RPM80% VE - ~2,100 RPM90% VE - ~1,900 RPM

So... looking at this compressor we see that it is small enough that it will easily handle your boost by 2,500 RPM goal, next we have to see if the compressor will choke at higher RPM.

16G "small" @ 1.4 PR/5.88 PSI choke point: ~350 - 360 CFM

VH45DE CFM at 1.4 PR/5.88 PSI at 7,200 RPM:60% VE - 239.75 CFM70% VE - 279.71 CFM80% VE - 319.67 CFM90% VE - 359.63 CFM

16G "small" @ 1.68 PR/10 PSI choke point: ~450 - ~460 CFM

VH45DE CFM at 1.6 PR/10 PSI at 7,200 RPM:60% VE - 287.75 CFM70% VE - 335.71 CFM80% VE - 383.67 CFM90% VE - 431.63 CFM

(Note: these CFM ratings are for half of the VH45, double them for total CFM or for a single turbo setup comparison)

What we see here is that the compressor should be large enough to at least not choke... though it is a bit on the small side as far as running very near the limit and will be hot/inefficient in those upper ranges (as low as 60% VE in the upper range). This all depends on how high you want to rev... this turbo is at least within range of working decently.

Note: Simply based on flow numbers and say our HP peak is still at 6,000 you could see numbers between 320 - 410 bhp at 1.4 PR (depending on VE, I'd lean towards the middle to high side simply because the VE should be higher than 70% at this point). At 10 PSI you could see numbers between 385 - 500 bhp. (This is all speculation and of course won't likely be exact but is simply to give an idea of what you could see. These numbers will remain relatively constant no matter what turbo you use, its simply the air flow of the VH45 with that particular amount of boost.)

Just to throw in some other info... its also good to note where the engine normally makes peak power and where the peak efficiency point is of the compressor (this efficiency is adiabatic efficiency, you can also call it heat efficiency. It is essentially how much heat is put out because of compression). The VH45's standard peak is at 6,000 RPM. At this point you would see these compressor efficiencies:

16G "small" 1.4 PR:60% VE - ~77% AE (adiabatic efficiency)70% VE - ~74% AE80% VE - ~72% AE90% VE - ~68% AE

16G "small" 1.68 PR:60% VE - ~77% AE (this compressor's max efficiency)70% VE - 76% - 77% AE80% VE - ~74% AE90% VE - ~72% AE

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Moving on... the 16G6. A little larger than the 16G "small" but still retains a wide map. A little less efficient peaking at 74%.

16G6 @ 1.4 PR/5.88 PSI will surge at:60% - ~3,000 RPM70% - ~2,600 RPM80% - ~2,300 RPM90% - ~2,000 RPM

16G6 @ 1.68 PR/10 PSI will surge at:60% - ~3,300 RPM70% - ~2,800 RPM80% - ~2,500 RPM90% - ~2,200 RPM

Could be a little on the large side for quick spool... just depends on the exact VE of course. Lets see the peaks:

16G6 @ 1.4 PR/5.88 PSI choke point: ~400 CFM

VH45DE CFM at 1.4 PR/5.88 PSI at 7,200 RPM (these are a constant):60% VE - 239.75 CFM70% VE - 279.71 CFM80% VE - 319.67 CFM90% VE - 359.63 CFM

16G6 @ 1.68 PR/10 PSI choke point: ~510 CFM

VH45DE CFM at 1.6 PR/10 PSI at 7,200 RPM (these are a constant):60% VE - 287.75 CFM70% VE - 335.71 CFM80% VE - 383.67 CFM90% VE - 431.63 CFM

We see here that we get a pretty decent margin up top. Compressor efficiencies are pretty good at these points too making this choice pretty decent as far as the top end.

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Next, the 20G. This is supposed to be the Mitsubishi big-mama. Pretty common on high power vehicles. Great efficiency like the small 16G, hitting a peak of 77%.

20G @ 1.4 PR (pressure ratio) or 5.88 PSI will surge at:60% - ~3,000 RPM70% - ~2,600 RPM80% - ~2,300 RPM90% - ~2,000 RPM

(Just like the 16G6... looks like a better choice than the 16G6 so far)

20G @ 1.68 PR or 10 PSI will surge at:60% - ~3,300 RPM70% - ~2,800 RPM80% - ~2,500 RPM90% - ~2,200 RPM

Also the same as the 16G6, this should definitely be a better choice than the 16G6 now. Its more efficient and can handle just as quick spooling.

20G @ 1.4 PR/5.88 PSI choke point: ~420 CFM

VH45DE CFM at 1.4 PR/5.88 PSI at 7,200 RPM (these are a constant):60% VE - 239.75 CFM70% VE - 279.71 CFM80% VE - 319.67 CFM90% VE - 359.63 CFM

20G @ 1.68 PR/10 PSI choke point: ~560 CFM

VH45DE CFM at 1.6 PR/10 PSI at 7,200 RPM (these are a constant):60% VE - 287.75 CFM70% VE - 335.71 CFM80% VE - 383.67 CFM90% VE - 431.63 CFM

Definitely a larger turbo than the 16G6 but it still has a nice, wide map making our upper limits even better and is more efficient. This should be a great choice if you can spool it fast enough.

20G efficiency at 1.4 PR at peak RPM:60% - 76% AE70% - 76%80% - 74% - 75%90% - 70% - 72%

20G efficiency at 10 PSI at peak RPM:60% - 76% AE70% - 76%80% - 74% - 75%90% - 70% - 72%

I really, really, really need to get back to work so I'll finish the below choices and thoughts later tonight possibly.

Z31 T3 would likely choke in the upper RPM's.

Garrett GT2876 and GT2871 should fit pretty well, the smaller ones would likely choke in the upper RPM. GT3071 and GT3076 are also good choices.

From what I can find on the T28... it appears to be a T25 turbine with a T3 compressor, similar if not exactly like what the Z31 T3 compressor is... which, like I said above, would choke in the higher RPM so probably wouldn't be a good choice. (maps I've found state both as being a T3 "60 trim" compressor).

[tmorgan4]

[Mettler]

IHI VJ23 turbos off the Mazda Familia GTR. Ballbearing center, nice big turbo capable of delivering like 400HP's worth of boost, still fairly responsive.

Look them up, they're decent.

[qsiguy]

Wow mtcookson, that's going the extra mile for a helpful post!

I always like posting my little turbo calculator when someone asks since I worked so hard on it

http://c4caraudio.com/tech/for...2.xls

[Stinky]

Thanks for the replys guys. Especially mtcookson. I'm gonna look into the t28s and 16g turbos some more. Looks like they will be easier to get, smaller, and a better match than the t3s.

[mtcookson]

Added 60% to the calculations to broaden the spectrum a bit.

Alright, other turbos.

GT2871:

GT2871 @ 1.4 PR/5.88 PSI will surge at:60% - ~3,300 RPM70% - ~2,800 RPM80% - ~2,500 RPM90% - ~2,200 RPM

GT2871 @ 1.68 PR/10 PSI will surge at:60% - ~3,300 RPM70% - ~2,800 RPM80% - ~2,450 RPM90% - ~2,200 RPM

GT2871 @ 1.4 PR/5.88 PSI choke point: ~29 lb/min

VH45DE lb/min at 1.4 PR/5.88 PSI at 7,200 RPM (these are a constant):60% VE - 16.57 lb/min70% VE - 19.33 lb/min80% VE - 22.09 lb/min90% VE - 24.85 lb/min

GT2871 @ 1.68 PR/10 PSI choke point: ~38 lb/min

VH45DE lb/min at 1.68 PR/10 PSI at 7,200 RPM (these are a constant):60% VE - 19.89 lb/min70% VE - 23.20 lb/min80% VE - 26.51 lb/min90% VE - 29.83 lb/min

Looking at the maps for the GT2876 and GT3071, they are very similar to the GT2871 just shifted slightly to the right. This will give you more room up top but will make your surge RPM a little higher meaning slower spool but not by much. One interesting thing to note is the GT30 series... they are quite a bit more efficient than the GT28's. The GT3071 uses the T25 style turbine housing while the GT3076 has quite a few different housings available including a dual scroll housing that, with a certain valve, could make for very quick spooling (going by surge numbers though, you won't really be able to spool it all that fast without surge issues on this engine, with more displacement it could be quicker).

Also, I was wrong about the GT2860RS (aka the "Disco Potato"). It will support what you want and can be spooled pretty quickly. It might put out a bit of heat near the limits but shouldn't choke. I believe it would also be a good choice. Now the GT2860R and GT2854R on the other hand... those will definitely run out of steam before redline. They're definitely too small.

I have some new info on the T28. One place I saw said it was a T25 turbine with a T3 compressor, being the T3 "60 trim" like on the Z31 T3 which I know is a bit too small. Another T28 map I found shows a slightly better map... though still ever so slightly too small. I believe the turbo of the second map I found would work... but you'd probably be pushing quite a bit of heat by 7,200 rpm. If you aren't planning on revving that high and want mostly mid-range power then it should work pretty well as it should handle pretty quick spooling.

Being that the T28 is a T25/T3 there should actually be quite a few different compressor options out there but I'm having a hard time finding specific T28's so it may not be that good of a choice for optimum performance from the standpoint of potentially getting one that is a bad match.

One might think that a turbo from a 2 liter would still work pretty good on a 2.25 liter... but surprisingly that tiny bit of difference can actually make a big difference for the turbo. For instance, check out our peaks between the two:

VH45DE half "2.25 liters" at 14.7 PSI at 7,200 RPM:60% VE - 23.67 lb/min / 342.5 CFM70% VE - 27.61 lb/min / 399.59 CFM80% VE - 31.56 lb/min / 456.67 CFM90% VE - 35.5 lb/min / 513.75 CFM

"2 liters" at 14 PSI at 7,200 RPM:60% VE - 20.9 lb/min / 302.5 CFM70% VE - 24.39 lb/min / 352.92 CFM80% VE - 27.87 lb/min / 403.33 CFM90% VE - 31.35 lb/min / 453.75 CFM

Doesn't seem like much but at our peak VE that's nearly a 50 hp difference.

Take our T3 "60 trim" for example... the 2 liter is right above the edge at peak VE while the 2.25 liters is well over the limit.

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Just for fun... I want to show you guys what a dyno would look like if our volumetric efficiency stayed at a constant (in case you didn't know, your peak torque is where your peak VE occurs.) This is based on if you had a constant 90% VE and based on the "rule of thumb" that 1 lb/min of air = 10 horsepower. Basically VE is the amount of air taken into the cylinder relative to the displacement of the cylinder. If the VE is 90%, only 90% of the cylinder's displacement was filled. A constant VE like this simply means the cylinder is being filled with the same amount of air per cycle.

[SSDwellah]

Very detailed as usual. Thanks for sharing! Do you have any feedback on the GT30R (other than it being a bit pricier ball-bearing turbo)? What about other Ball bearing turbos? Those will give you the early spool while still having room to grow power-wise and still run effecient.

[SuperHatch]

Very detailed as usual. Thanks for sharing! Do you have any feedback on the GT30R (other than it being a bit pricier ball-bearing turbo)? What about other Ball bearing turbos? Those will give you the early spool while still having room to grow power-wise and still run effecient.

In my experience with BB vrs. Std. Bearing turbos (which is quite substantial), the BB turbos aid very little in spool up. Where they really shine is in the transient areas.

Example...

Standard bearing GT30 might get full boost at 3600RPM in third gear on a 2.0L Mitsu. A GT30R might get full boost at 3500-3550 under the same conditions.

However, the driving impressions recieved between the two are substantially different, the transient response of BB turbo is fantastic. When shifting under full throttle acceleration, the return to full boost after a shift is much faster with a BB turbo. Also, when above 3500RPM (in the same scenario as above) matting the throttle will result in much quicker spoolup with a BB turbo.

Are they worth the money? It depends on the use IMO. In my case... my drag 240 with a built automatic could spool at the line and then stay full throttle the whole run. Transient doesn't matter much. On a boosted street or road course car? Heck yes it's worth the extra cash!

[mtcookson]

In my experience with BB vrs. Std. Bearing turbos (which is quite substantial), the BB turbos aid very little in spool up. Where they really shine is in the transient areas.

Example...

Standard bearing GT30 might get full boost at 3600RPM in third gear on a 2.0L Mitsu. A GT30R might get full boost at 3500-3550 under the same conditions.

Is that with the same turbine housing though? I think generally people tend to run larger turbine housings with the BB unit as they can get the same spool with better top end capability. I haven't personally got to mess with BB turbos but that was the impression I was under.

Quote »Do you have any feedback on the GT30R (other than it being a bit pricier ball-bearing turbo)?[/quote]GT3071R:

@ 1.4 PR/5.88 PSI will surge at:60% - ~3,300 RPM70% - ~2,800 RPM80% - ~2,500 RPM90% - ~2,200 RPM

Choke point: ~31.5 lb/min

@ 1.68 PR/10 PSI will surge at:60% - ~3,800 RPM70% - ~3,300 RPM80% - ~2,900 RPM90% - ~2,550 RPM

Choke point: ~38 lb/min

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GT3076R:

@ 1.4 PR/5.88 PSI will surge at:60% - ~3,900 RPM70% - ~3,350 RPM80% - ~2,900 RPM90% - ~2,600 RPM

Choke point: ~36.5 lb/min

@ 1.68 PR/10 PSI will surge at:60% - ~4,350 RPM70% - ~3,700 RPM80% - ~3,300 RPM90% - ~2,900 RPM

Choke point: ~44 lb/min

VH45DE lb/min at 1.4 PR/5.88 PSI at 7,200 RPM:60% VE - 16.57 lb/min70% VE - 19.33 lb/min80% VE - 22.09 lb/min90% VE - 24.85 lb/min

VH45DE lb/min at 1.68 PR/10 PSI at 7,200 RPM:60% VE - 19.89 lb/min70% VE - 23.20 lb/min80% VE - 26.51 lb/min90% VE - 29.83 lb/min

The GT3076R used to be my preferred turbo for the VH45... but looking at it now I think it would be a bad choice for me since I'm wanting more low end power than high end essentially. The 3076 could potentially support over 1000 bhp... if that's what you're looking for they should be excellent for that. (though... at that point it might not be a bad idea to step up to the GT3582 for a little better efficiency in the higher range).

(Note: Just in case anyone is curious... when I say "choke" I'm basically talking about the end of the compressor map, the furthest point to the right. The turbo is still technically providing boost... its just so inefficient that they don't plot any further (usually 60% is the cutoff point. For instance, the 20G's cutoff is actually 65% so technically you could actually push it a bit further for lower efficiencies... though I wouldn't personally recommend it as it would be putting out a lot of heat).

Correction to my info above - I don't know why... but for some reason I put VE (volumetric efficiency) when I was talking about turbo efficiency when it should be adiabatic efficiency (heat efficiency). I'll correct that asap.

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More on the VE stuff... just figured I'd throw this thought out too.

All you're essentially doing with boost is increasing the VE (of course, we're cramming more air into the cylinder). Say for instance you're pushing 12 PSI or a 1.82 PR at 6,000 RPM and our airflow is 345.6 CFM at a standard engine VE of 80%. To get the same airflow NA would take a VE of 231%

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Now, I have to again stress that all of these numbers are to give you a simple idea of what the turbo could potentially do. The likelihood of it performing by these numbers is slim since there are so many other variables like air temp, pressure (altitude), etc. etc. etc. Even the volumetric efficiency calculation is a bit difficult to do considering the ports are likely to act completely different under boost than they are NA among other things. The best thing to do is to find the turbo that meets the majority of your needs basing off of this info and going from there. Luckily it will at least perform correctly unlikely blindly throwing on a huge turbo or a small turbo where one takes forever to spool and the other chokes quickly... this info just gets you in the right area.

[T45]

All in favor of banning mtcookson for not contributing to the forum say I...

[tmorgan4]

Has anyone ever modeled a VH45 in a program like Dyno2000? It allows you to play with different turbo setups and might be fun to play around with. I just didn't have all the specs to accurately model the heads and intake portion.

[SuperHatch]

Is that with the same turbine housing though? I think generally people tend to run larger turbine housings with the BB unit as they can get the same spool with better top end capability. I haven't personally got to mess with BB turbos but that was the impression I was under.

Yes, same turbine housing.

The tricky thing to remember is transient response versus engine RPM. In low gears, when you mash the throttle the engine will naturally accelerate faster making a journal bearing turbo seem laggier. The time for the JB to spool as the revs come up is longer, so it essentially hits full boost at a higher RPM even though it would have started spooling at the same RPM as a BB turbo.

A JB turbo and a BB turbo of the same size wheels and housings sill start spooling at the same RPM. That's the physics of the exhaust flow. What helps in the transients is rolling resistance in the bearings and the weight of the wheels.