Twins vs single vs 2 x singles lol

[khezz]

On 1/5/2022 at 10:04 PM, Butters said:

I can't remember exactly what ant man had on his skyline it may have been twin t04z , made big power numbers, near 1000 in the days before that was a thing. Didn't boost until near 7000rpm though.   Cool as hell to see.  

Are you talking about Anthony Scally’s silver R32 gtr? 
 

he had a hks 2.8 stroker. I was there at Xspeed during one of the tuning sessions. That thing was mental on boost. Hanson did the first lot of work on my gtr before he closed shop. 

[Lithium]

On 01/05/2022 at 11:33 PM, khezz said:

You are so negative. Yes, it will spool up later then a 7685 but you don’t run an 8.7 in a full bodied R32 with turbos that don’t spool. 
 

if I get disappointed, I can always go back. It’s not like there is a lack of choice when it comes to big modern singles. But old school big twins in good nick do not come up very often at all. 

I wasn't trying to talk you out of them, just making sure you did appreciate that it would be super laggy (I never said they won't spool either) - not just a bit lazy.  I'd call that realistic, not negative.    Fwiw, something measured using no-lift-shifting and generally being used at full throttle/max possible rpm isn't the best metric for what it's going to drive like but yeah.   

Anyway, you sound like you are pretty happy with the compromises - as I said at the start, I love the old school JDM drag "style" and look forward to seeing results (you don't ACTUALLY get to see what this kind of combo dynos like etc very often at all) and videos... miss this kind of build, and keen to hear it.

 

[khezz]

On 2/5/2022 at 5:15 AM, Lithium said:

I wasn't trying to talk you out of them, just making sure you did appreciate that it would be super laggy (I never said they won't spool either) - not just a bit lazy.  I'd call that realistic, not negative.    Fwiw, something measured using no-lift-shifting and generally being used at full throttle/max possible rpm isn't the best metric for what it's going to drive like but yeah.   

Anyway, you sound like you are pretty happy with the compromises - as I said at the start, I love the old school JDM drag "style" and look forward to seeing results (you don't ACTUALLY get to see what this kind of combo dynos like etc very often at all) and videos... miss this kind of build, and keen to hear it.

 

I didn’t mean any offence. Just being a smart arse. I apologise. You have given me great advice in the past and a value your knowledge and opinion very much. 
 

got to talk allot more with the owner. Turbos had full boost at 5500rpm and made just over 1100hp at rear wheels on a 2630 combo. I am hoping that I will see full boost around 1000-1500 rpm earlier with the advancements made to my engine, the turbos and tuning. Final call is with my mechanic to see if he wants to take on the challenge. If this goes ahead, I promise to post lots of run in, tuning, driving and racing videos. If I end up going back to a big modern single, it will make for a very good comparison. 

[Dose Pipe Sutututu]

On 02/05/2022 at 11:12 AM, khezz said:

If I end up going back to a big modern single

This will inevitably happen  

Especially if street driven, if it's a dedicated drag car on nitrous, meth, and big stally auto then probably no.

[Lithium]

On 02/05/2022 at 1:12 PM, khezz said:

I didn’t mean any offence. Just being a smart arse. I apologise. You have given me great advice in the past and a value your knowledge and opinion very much. 
 

got to talk allot more with the owner. Turbos had full boost at 5500rpm and made just over 1100hp at rear wheels on a 2630 combo. I am hoping that I will see full boost around 1000-1500 rpm earlier with the advancements made to my engine, the turbos and tuning. Final call is with my mechanic to see if he wants to take on the challenge. If this goes ahead, I promise to post lots of run in, tuning, driving and racing videos. If I end up going back to a big modern single, it will make for a very good comparison. 

Ahh, yeah sometimes hard to tell with tone

Meaningful boost by 5500rpm isn't inconceivable, though full boost at 4000-4500rpm - I'll have something to learn if your setup manages that, unless you've missed out mention of nitrous or that the turbo tweaks include changing to much smaller wheels etc 😮

In saying that, I've been involved in brain storming for a twin setup for >1000hp @ hubs hoping for full boost around 4000rpm on a 3litre and we have hopes that it's achievable but that's getting pretty cunning with the overall setup - from what you've said you're not getting up to the kind of mischief we're planning 

[khezz]

On 2/5/2022 at 9:37 AM, Lithium said:

Ahh, yeah sometimes hard to tell with tone

Meaningful boost by 5500rpm isn't inconceivable, though full boost at 4000-4500rpm - I'll have something to learn if your setup manages that, unless you've missed out mention of nitrous or that the turbo tweaks include changing to much smaller wheels etc 😮

In saying that, I've been involved in brain storming for a twin setup for >1000hp @ hubs hoping for full boost around 4000rpm on a 3litre and we have hopes that it's achievable but that's getting pretty cunning with the overall setup - from what you've said you're not getting up to the kind of mischief we're planning 

I’m hoping for full boost by 4500-5000 on a 3.2. I still think that’s realistic. 

[Lithium]

On 02/05/2022 at 3:37 PM, khezz said:

I’m hoping for full boost by 4500-5000 on a 3.2. I still think that’s realistic. 

Very interested to see where it ends up That'd be a good result!

[BK]

Keir Wilson's 1000kw + R35 I mentioned above makes meaningful boost at 4500rpm, full boost is around 6000rpm and revs to 7500rpm.

This is also 4.0 litre VR38 , so realistically a 3.2 RB is never going to be anywhere near what that will achieve. FYI and comparison his R32 with the smaller twin T67 Trust turbos made around 850hp / 630kw at wheels on an OS giken 3.0 litre and was still not a full boost by 6000rpm, but did rev over 9000rpm.

For a genuine 1000whp RB twin high mount setup, I think a pair of gen2 5558 650hp turbos would yield superior results in spool and power compared to the Trust items.

[GTSBoy]

I still say that a supercharger + turbo is the answer to all this bullshit. Put 500HP worth of screw compressor on board and have it hand over responsibility to the 1000HP worth of turbo(s) at some point where the turbo(s) can and will make all the boost you need, without needing to worry about their boost threshold, etc etc, wah wah. Torque multiplier from idle on up from the blower = more gas to the turbine anyway. You get to use an open housing for reduced EMAP at full noise. Win win win win win.

And that's just as a sequential setup. Extra brownie points for doing it in series. Low blower pressure ratio multiplied by low turbo pressure ratio = high pressure ratio with none of the stress that typically results from trying to get it all from one place.

[Lithium]

On 02/05/2022 at 4:09 PM, BK said:

FYI and comparison his R32 with the smaller twin T67 Trust turbos made around 850hp / 630kw at wheels on an OS giken 3.0 litre and was still not a full boost by 6000rpm, but did rev over 9000rpm.

That's more like I would have expected

On 02/05/2022 at 6:09 PM, GTSBoy said:

I still say that a supercharger + turbo is the answer to all this bullshit. Put 500HP worth of screw compressor on board and have it hand over responsibility to the 1000HP worth of turbo(s) at some point where the turbo(s) can and will make all the boost you need, without needing to worry about their boost threshold, etc etc, wah wah. Torque multiplier from idle on up from the blower = more gas to the turbine anyway. You get to use an open housing for reduced EMAP at full noise. Win win win win win

It is a pretty cool idea but you do really need to intercool between each stage otherwise the air density becomes rubbish and as such the second stage becomes a lot less efficient and you don't necessarily end up with the results you could while also having mechanical drag added to it... But the general concept is awesome

[GTSBoy]

On 5/2/2022 at 3:50 PM, Lithium said:

you do really need to intercool between each stage otherwise the air density becomes rubbish

Not really - depends on sequential or series, and if doing it series, then depends on the boost target.

For sequential, then it's really only ever blower or turbo, delivering either, say 10 psi or 30 psi (or blending between them at the changeover. The requirement for intercooling there is the same as if you were only running one or the other.

For serial, let's say that you want 30 psi total boost. You might run the blower at 8 psi. That's a PR of ~1.5. Not terrible for efficiency from a good screw compressor, so the temperature rise is not bad. Now the inlet pressure to the turbo is 22.5 psi (absolute) or thereabouts. The PR from the turbo's compressor is (30 psi + 14.7 psi) / 22.5 psi. That's only a PR of 2 - which is like running a turbo alone at only 14.7 psi of boost. That's well within the ability of very many turbos with good efficiency. If you intercool (and in this case it truly is intercooling)  between stages, then you only gain even better results - plumbing complexity nothwithstanding. But in reality, it is no worse than running 30 psi from a single stage and it is actually possible to obtain a total compressor efficiency that is better than any single turbo compressor can achieve at 30 psi (which is an outright PR of 3).

If you were to push the limits of what's possible with each stage, say going to 12+ psi from the blower and then trying to run a PR of 2.5 or 3 from the turbo, for a total boost of 60 or 80 psi, then yeah, sure, intercooling as well as post cooling would be essential. But that's not what we're talking about here. We're talking about ~1000HP ~3L engines, which are doable in the 30 psi of total boost range - especially when a free flowing turbine section is part of the mix.

[Butters]

On 5/1/2022 at 10:42 PM, khezz said:

Are you talking about Anthony Scally’s silver R32 gtr? 
 

he had a hks 2.8 stroker. I was there at Xspeed during one of the tuning sessions. That thing was mental on boost. Hanson did the first lot of work on my gtr before he closed shop. 

Yep. One of his many combos. The Dyno graph was like nothing I have seen before nor likely to see again. 

[khezz]

On 2/5/2022 at 12:09 PM, BK said:

Keir Wilson's 1000kw + R35 I mentioned above makes meaningful boost at 4500rpm, full boost is around 6000rpm and revs to 7500rpm.

This is also 4.0 litre VR38 , so realistically a 3.2 RB is never going to be anywhere near what that will achieve. FYI and comparison his R32 with the smaller twin T67 Trust turbos made around 850hp / 630kw at wheels on an OS giken 3.0 litre and was still not a full boost by 6000rpm, but did rev over 9000rpm.

For a genuine 1000whp RB twin high mount setup, I think a pair of gen2 5558 650hp turbos would yield superior results in spool and power compared to the Trust items.

That makes his 1/4 time even more incredible. Did he run nitrous?

[Lithium]

On 02/05/2022 at 7:38 PM, GTSBoy said:

Not really - depends on sequential or series, and if doing it series, then depends on the boost target.

For serial, let's say that you want 30 psi total boost. You might run the blower at 8 psi. That's a PR of ~1.5. Not terrible for efficiency from a good screw compressor, so the temperature rise is not bad. Now the inlet pressure to the turbo is 22.5 psi (absolute) or thereabouts. The PR from the turbo's compressor is (30 psi + 14.7 psi) / 22.5 psi. That's only a PR of 2 - which is like running a turbo alone at only 14.7 psi of boost. That's well within the ability of very many turbos with good efficiency. If you intercool (and in this case it truly is intercooling)  between stages, then you only gain even better results - plumbing complexity nothwithstanding. But in reality, it is no worse than running 30 psi from a single stage and it is actually possible to obtain a total compressor efficiency that is better than any single turbo compressor can achieve at 30 psi (which is an outright PR of 3).

If you were to push the limits of what's possible with each stage, say going to 12+ psi from the blower and then trying to run a PR of 2.5 or 3 from the turbo, for a total boost of 60 or 80 psi, then yeah, sure, intercooling as well as post cooling would be essential. But that's not what we're talking about here. We're talking about ~1000HP ~3L engines, which are doable in the 30 psi of total boost range - especially when a free flowing turbine section is part of the mix.

Firstly, I was responding to your conclusion "extra brownie points for doing it in series", I had no issue with the concept in sequential.

Second, you wouldn't run a Lysholm as the first stage - unless I'm missing something  you cannot move more through the compressor than it can flow by itself.   You'd need a significant bypass to allow a 90+lb/min turbo to be able to move all the airmass it needs to achieve ~1000hp, and if you're doing that kind of bypass then it's a sequential setup.  With a multi-stage compressor setup you run the biggest compressor first and use the smaller ones as pressure ratio multiplier, you've increased the density of the air going into them so they don't need to move a larger volume of air than they are able to.   If the Lysholm was able to support 90+lb/min then there is no point running the turbo at this point.

Now for my other comment, I have to admit I stuffed up my math - more because of rushing it and mis-juggling the numbers than anything else.    To give an idea of why I thought that... I assumed 65% adiabatic efficiency for a twin-screw (I think this is VERY fair) at pressure ratio 1.5 with 24c pre-compressed air temp then you end up with 84c outlet air temperature.   If you WERE going to compress this by a PR of 2.0 using a typical centrifugal compressor without intercooling it first then you'd end up with a second stage temperature of over 200c.   Where I messed up my calculations was that I had a brain fart with the "final density" calculation and ended up effectively treating it like you needed to cool 207c using 84c ambient temperature - not 24c, so that ended up with a MUCH lower air density in the intake manifold... 88lb/min mass flow "conventionally turbocharged at 30psi" became 73lb/min at the same "boost level" and made it look like a fail, but actually it's not that bad at all.   It would actually "only" fall down to 85lb/min.... so still less dense than single stage but you're right, non-intercooled between the two stages wouldn't be a game changer.  

That aside, I prefer the idea of a regulated 2-stage turbo setup for spark ignited small displacement/"moderate boost level" engine than a compound supercharger/turbocharger setup.

 

Edited May 2, 2022 by Lithium

[Ben C34]

Huh?

2 massive high mounted turbos from ages ago and revving to the moon is the topic of this thread. ( or trying to draw a vertical line on a dyno plot close to the right hand side, sort of fhe same.)

 

[Lithium]

On 03/05/2022 at 10:47 AM, Ben C34 said:

Huh?

2 massive high mounted turbos from ages ago and revving to the moon is the topic of this thread. ( or trying to draw a vertical line on a dyno plot close to the right hand side, sort of fhe same.)

 

Oops!  Sorry.  Yes, that.   Though I do like the idea of two solid sized turbos, a huge meaty power delivery AND revving to the moon which is how I got sucked into the off topic bit.

Would love to know more detail on what @Butterswas talking about re: dyno plot, I know the exact detail / plot itself may not be available... I'm guessing it epitomises the description you gave there?

@khezz, when you're "keeping it on the boil" etc it can be surprising how shit a power delivery can be used to make a car go fairly quick.   One of the cars I tune runs an over-cammed (imho) 4EFTE head in a Toyota Starlet running a stock Toyota W58 gearbox.  The engine doesn't start to really trap useful air until around 4500rpm, but the block/bottom end setup is not safe to really run much over 8000rpm so basically ANY turbo you put on it is going to be laggy as f**k but you don;t even get to rev it to the moon to make up for it.

When I first got involved with it the thing was running a Turbonetics turbo which wasn't full boost (~23psi) until around 6000rpm (later after gearshifts on the strip) and still managed to run a 10.7 @ 130mph, driving the absolute shit out of it - but that's basically not making full boost until somewhere between 6000 and 7000rpm on the strip and only revving to 8k with a 1.5litre engine.   He ended up putting a G25 550 in there to make it a bit easier, and we ended up with full boost at 5300rpm (remember the engine doesn't really start even driving the turbo until after 4000rpm, so that is a VERTICAL dyno plot lol) and way better transient response... brought it down to 10.5 @ 133mph at the same boost/similar power, and most of the improvement is just because of response, and that's him being less brutal on the gearbox.  

Seems off topic, but the moral of it is you can go surprisingly quick at the strip with a rubbish power delivery even without flatshift or a sequential transmission - that Starlet has a woeful power delivery and still does solid 10s without a huge amount of power.  Clearly improving the delivery helps, and it would go much quicker with a better transmission, but still be a dog for anything else.  The point is 1/4 mile times are pretty much the worst measure for how nice a car is to drive.

 

Edited May 2, 2022 by Lithium

[GTSBoy]

On 5/3/2022 at 7:58 AM, Lithium said:

Second, you wouldn't run a Lysholm as the first stage - unless I'm missing something  you cannot move more through the compressor than it can flow by itself.

Yeah yeah. Turbo first, then screw. But the maths still holds, as you came around to.

The simple fact is that the blower gives boost where no turbo ever can, and that's something worth wanting.

[Butters]

On 5/3/2022 at 7:04 AM, Lithium said:

Would love to know more detail on what @Butterswas talking about re: dyno plot, I know the exact detail / plot itself may not be available... I'm guessing it epitomises the description you gave there?

 

You are correct, it was very flat until about 6000ish, then went straight up, horizontal for a couple of thousand rpm.  I did take a picture, i'll see if i can did it out. It was "one of" the most powerful gtr in australia at the time. 

[khezz]

Well the T67s have fallen over. Shame. I am however exploring another idea of. Twin 700hp high mount kit. This time going all modern. Roller bearing, billet wheels. Looking at staying around .65 rear housing. Do I go twin T51 mod?  
 

any suggestions are welcome.

[BK]

On 02/05/2022 at 1:39 PM, BK said:

For a genuine 1000whp RB twin high mount setup, I think a pair of gen2 5558 650hp turbos would yield superior results in spool and power compared to the Trust items.

Told you already, possibly Precision 5858.