Dual (Non-Twin) Turbo setup?

[MarkSanne]

While reading lots of topics about turbo setups on the forum I started fantasizing, not hindered by too much technical knowledge, about a dual Turbo setup on my VR-4. As I read, the boost on the stock twin turbo's can be set quite 'safely' to about 1.0bar. Now I was thinking, why not change one of these 'lightweight' turbo's for a bigger one? The small one will get things going and when it loses it's power, the bigger one takes over.

Sounds right to me, but probably has it's downsides which a lot of you experts can tell me about!

[Beastlee]

I think the problem is that dual turbos are sequential not one per side of the V. You would end up with some odd problems from one side of the V being at a different level of boost to the other.

Maybe dual twin turbos ;) Just watch out for VOD.

[Kieran]

Problem would also be that with a bigger turbo, you'd probably struggle to get it on boost if you're just using the exhaust gas out of one side of the V to spin the turbo up.

[MarkSanne]

Problem would also be that with a bigger turbo, you'd probably struggle to get it on boost if you're just using the exhaust gas out of one side of the V to spin the turbo up.

Yeah, but how about all those theads here talking about upgrading to bigger turbo's? TD04's or even bigger?

[Beastlee]

They also do a number of other mods to get more off-boost power, lag is there but compensated for by the greater power and longer power band.

Saab 9K Aero uses a TD04 and it has no lag at all, peak torque at 1800RPM! I think they would have been OK on the VR-4 but the peak is higher in the rev range.

[Kieran]

Yeah, but how about all those theads here talking about upgrading to bigger turbo's? TD04's or even bigger?

Yeah, but if you think for a minute, to get a big jump in power you'd need to go for a rather big compressor, if you had one standard TD03 and a 'Bigger' one... Let me illustrate (These are aproximate figures)...

2 x TD03-7Gs are rated at 275 CFM @ 2PR each - total 550CFM.

2 x TD04-13Gs are rated at 360 CFM @ 2PR each - total 720CFM.

1 x TD03(275) and another turbo, well you'd need something in excess of 445CFM to make it worth while going for it over two TD04s - pushing you into TD05 territory. Of course it's possible - but with effectively only 3 cylinders and 1250cc to supply exhaust gas to that turbo you'd have to have quite a wild engine to get it on boost properly.

As Beastlee says, you'd fall right into the 'Valley of death' where the single little TD03 is spinning it's nuts off and can't keep up as the rpm climbs, and the 'big' turbo is still not on boost.

[Beastlee]

Right twice in one day, I'm on a roll...

has anyone tried TD04-13Gs on a VR-4? Would be interested to know the results, a little more lag may be worth it.

[Gowf]

Right twice in one day, I'm on a roll...

has anyone tried TD04-13Gs on a VR-4? Would be interested to know the results, a little more lag may be worth it.

I know that Valmes has, and im in the process of it. So all things going well... come to Japshow and the results shall be seen!

[Beastlee]

I know that Valmes has, and im in the process of it. So all things going well... come to Japshow and the results shall be seen!

Are you doing anything else to fit them?

[Gowf]

Are you doing anything else to fit them?

Yep.
Firstly they dont just bolt on. The ones i have are off of the uk GTO. you can just modify the original manifolds to get them to fit, but then you have bulkhead, engine mount and oil filter issues, so i've gone down the custom manifold route. The turbos also need clocked so as the oil feed and return are in correct orintation. And custom oil and water feed and return pipes made, although i believe you can modify the standards.

There's been a bit of discussion on the topic regarding fueling, but ive decided to use a sard 265 pump and the rj pressure regulator. Injectors i havent got around to getting yet, but if i keep the boost low to start with, i can then see how the standards cope before uprating.

complete turbo hard pipe kit, along with greddy spec R intercooler. Battery will be located in the boot, and maybe run 2 air filters.

The dump valve has been changed to a Forge recirc.

Fueling and boost is controlled by MAP2.

Keeping an eye on boost, knock, afr, oil temp and pressure on guages.

I cant think of anything more off the top of my head, as the hangover is still in full swing.... But its certainly not just a nice bolt on mod.

[Goku]

While reading lots of topics about turbo setups on the forum I started fantasizing, not hindered by too much technical knowledge, about a dual Turbo setup on my VR-4. As I read, the boost on the stock twin turbo's can be set quite 'safely' to about 1.0bar. Now I was thinking, why not change one of these 'lightweight' turbo's for a bigger one? The small one will get things going and when it loses it's power, the bigger one takes over.

Sounds right to me, but probably has it's downsides which a lot of you experts can tell me about!

There are realy only 2 cars that use that setup effectively

the Series 6 -> RX7 (Batman) and the Subaru Legacy.

There's not really much point in doing this on the VR-4, as space it limited as it is, you'd be better going to 2 larger turbo's and work the engine that way.

Though I am waiting to see a Twin charger setup on a VR-4.... Super charger + twin turbo :D

[bradc]

Putting two differently sized turbos in a VR-4 is a bad idea, for the reasons outlined above. The only way I would see it working is a triple setup where you have the TD03's running of each bank of cylinders as they are now, and at a certain point switching over to a big turbo like a GT35R mounted above the transmission.

Gowf, keen to see some pics and results of your car, when are you dynoing it?

[Gowf]

Got to get everything fitted first... But i'l prob take pics when doing so. Just waiting on manifolds at the moment, but as soon as they are with me, then it'l all be done.
Well.... thats the plan anyway.

It was dyno'd in its current condition, and made 211 at the wheels under standard boost with no fuel mods. so will be very interesting to see what we end up with

[bradc]

211kw or hp?

[Gowf]

HP, equated to 270ish at the fly.

Was quite happy with that though, for a standard car( other than intercooler, and air filter)

[bradc]

/yawn, wake me up when you get past 225kw atw, cause thats what I'm running at on my TD03's.

Just kidding, I'm very excited that this year there are 3 or 4 projects coming together with turbo upgrades, MAD props to you.

[Gowf]

what boost pressure are you running for the 225kw?

[bradc]

somewhere between 15psi and 20 :)

[Kenneth]

running 2 turbos of different sizes, one off each bank will have a bigger issue than the valley of death, or lag or whatever.

The O2 sensor monitors the AVERAGE O2 reading over all 6 cylinders.

If you have a bigger turbo one side, you will alter the breathing of those 3 cylinders. At higher rpm/load that side will breath more easily.

As the engine management averages out across all 6 cylinders, 3 will run lean and 3 will run rich. The result of which will probably be a blown engine.

[valmes]

13Gs and 13Ts are somewhat different turbos... 360 CFM vs. 405 CFM

[Gowf]

13Gs and 13Ts are somewhat different turbos... 360 CFM vs. 405 CFM

Yes they certainly are. Didnt mean to offend, my point was that you have succesfully fitted and are running TD04's.

What is the lag like with the 13T's?

[valmes]

Yes they certainly are. Didnt mean to offend, my point was that you have succesfully fitted and are running TD04's.

What is the lag like with the 13T's?

Acceptable.

[Beastlee]

LOL, I've seen those vids on Youtube ;)

[valmes]

Here is my initial setup:

Stock MAF
--------
GTO intake pipes
13Ts (on stock exhaust manifolds)
turbo exhaust outlet plates
--------
Stock downpipes

Most of the other stuff is either "minor mods" (like clocking the turbos for example) or "supporting mods" (like injectors, clutch etc)...

[bradc]

I went for a ride in 'allbeitmine's car a few months ago, he has a similar td04 setup and I couldn't notice any additional lag over stock.

[Beastlee]

Do you know if he had to make any other changes to get them on?

[MarkSanne]

I went for a ride in 'allbeitmine's car a few months ago, he has a similar td04 setup and I couldn't notice any additional lag over stock.

But did you notice an actual (worthwhile) performance boost? (Did he put it on a dyno?)

[bradc]

he hasn't got an ecu in there to do the tune yet, so at this stage power isn't known. My car in it's current tune is way faster than what his was though.

[zentac]

sorry if this has already been said as Ive not read all the replies but if your going to run 2 different size turbos, you would need to run 2 seperate exhaust systems with lambda sensors in each for tuning, and for good measure and after market ECU. Could be an interesting.

[Turbo_Steve]

I think you'd find lopsided turbos would result in bent rods: significantly different backpressures on the exhaust side, and sudden pressurisation of a second turbo biased towards one bank? crunch!

If you were to do a sequential setup, the best way would be to create new manifolds. You could then mount your sequential turbos on the output with a pair of 'lock off' wastegates for the high pressure unit. Best suggestion would be a closely matched pair: example TD04 13T and then a TD05-18G or possibly 20G.

As with the RX7 and the legacy, each turbo will need several 'gates'
One wastegate to bypass both turbos, one 'boost' gate to control flow to the larger unit, and another on the output side of the larger unit to stop boost flowing through it backwards to the atmosphere (imagine what the MAF would make of that!)

Much cheaper just to stick on a bottle of NOS, or pair of dedicated hybrids.
Which raises the question, has anybody tried one of the many hybrids out there?

Something like TD03 housings ported out, with a TD04 compressor wheel and a decent ball bearing cartridge. After all, sleeve bearings are hardly the best way of avoiding lag: Compare any Garett with it's cheaper Mitsubishi equivalent!

[djb160]

Don't the supras run sequentials as well?

[Kieran]

Don't the supras run sequentials as well?

Yep.

[I-S]

BMW are in the sequential turbo game now as well, with the 3.0 petrol and diesel twin turbos (sold as 335i and 335d/535d). Mercedes were looking at (I don't know if they still are) a tri-turbo setup for their V6 diesel, with one small turbo per bank (like the VR4) as the first stage and then a single large turbo as the second. And of course, VW have their related TSI system, which is a sequential charging system, but where the initial charge is from a supercharger and then there's a turbocharger in addition.

[bradc]

yeah merc did that tri setup on a diesel, kind of a cool idea :)

[djb160]

would the twins cause the single to prespool or would they just conveniently overlap a sensible amount? I prefer the dual charged concept, unless it suffers from the hole in the power thing while they switch over.

[Turbo_Steve]

Dual charged (i.e. SuperCharger & Turbo) generally doesn't pull like a twin turbo setup, unless it's a big old V8 or similar....might work on a smaller V6 but I doubt 2.5L is enough to really get the max out of a supercharger and big turbo combo.

Triple turbo sounds interesting.....two GT27s and a GT40? :D

[Gowf]

Duel charged did work well, all you have to do is look at the lancia integrale S4, they were quite the GpB car!

[bradc]

nahh, stick with the stock TD03's until 4000rpm then switch over to a GT35R or a similar large turbo.

[Turbo_Steve]

I'd argue that the TD03's are actually too small: everything I've heard indicates that they're on boost by 1800rpms, which is frankly ridiculous: wanting to eliminate lag is one thing, but to put things in perspective I've run a pair of GT27s on a VG30DETT and with a good map and boost control they were into their stride by 2200rpms. Admittedly the smaller 2.5 of the legnum would probably bring this up to 2500rpms (which I would suggest is the upper limit for a tractable road car: a bad map on a single turbo 2.0 has taught me that for sensible overtaking you need to be on chat by this point) but as there's another wall of torque coming in as the engine spools up the even bigger unit, this could be mapped as a continual smooth mounting of power up to a (say) 9000rpm redline, rather than a sudden thump at 3800rpms.

I do take your point that for ultimate driveability the TD03s are perfect, however even then I'd suggest they need to be marginally larger.


The real question, I suppose, is "Does anybody hybridise the TD03s?"
I've not had the chance to handle a TD03: Presumably a larger compressor wheel could be crammed into the current housing (larger TD03?).
Alternatively, GT25R's with a good ball bearing catridge is going to spool better than the TD03 anyway, and can also accept a GT27 sized compressor. A pair of these is going to see you well into 500bhp, and should maintain almost identical daily driving charecteristics......what would the third turbo be for? Past 500bhp I'd imagine we're well into engine rebuild territory anyway, in which case we should be looking at stroking possibly boring, which completely changes our turbo requirements regardless: Pair of TD04s easily, possibly a pair of carefully setup GTR30s if you want to be really silly, or perhaps a pair of GT27s and a GT60 or something ridiculous like that, which would take you to silly bhp.

Anyone done comparisons of the 13T compressor? Or perhaps a TD04 wheel?
just wondering as it would strike me as perfact.

[Kieran]

Steve - You speak very knowledgeably about turbochargers - Do you work for a rebuilder or something?

As for hybridising the TD03s... Well, I don't know of any 'typical' hybrid, that is to say a larger compressor in the same housing. What I have seen is this.... Nick Mann's car originally had 'Hybrid' TD03s, but we don't know what exactly was done. These units have since failed and are currently in EuroSpec's hands (I think?) for further research. Having seen them myself, the only immediately obvious difference was that the inlet nozzle had been machined to a larger diameter than the original.

Also, if you look on the T'internet (via Google.co.jp) you can find some Japanese enthusiast websites and some Japanese people have had their turbines 'clipped' - I presume you know that this entails, and if you do, would you mind explaining for me?! /help :embarasse

[bradc]

K - compared to a normal garrett GTxxR series turbo, our turbines are undersized for our compressors. Clipping the turbine blades is as simple as you would think, you just chop a bit off the blades so there is less back pressure and the blades each do a bit less work. So lag goes up, but restriction goes down.

I bought a pair of modified td03's with clipped turbines and slightly modified compressor inlets, but they hasn't been loctite'd and blew up. I may get them rebuilt and fitted at some point.

[MarkSanne]

<keeping quiet mode interrupt>

never thought this topic to last this long...
interesting stuff people!

<resume to keeping quiet mode>

[rees]

<keeping quiet mode interrupt>

never thought this topic to last this long...
interesting stuff people!

<resume to keeping quiet mode>


yeah i know what ya mean ! i am SO out my depths in this thread :stars:
but still interesting to follow as i've been mulling over the idea of a rotrex supercharger install
but anyway great thread i think ill be following closely/notworthy

[Turbo_Steve]

Unfortuately I can't claim to be any kind of expert - I've just had a fair bit of experience with modified cars over the years! Efficiency maps still leave me blinking, and engine internals remain something of a dark art. Ah how I wish I'd gone for that engineering degree after all! So I'm afraid I'm another bumbling amateur.

Turbine clipping is as above, however it must be added that it's only applicable innarrow circumstances, i.e.when the restriction of the turbine slows you getting on boost (which is almost never with good design) or when the turbine simply flows less than the compressor. This is fairly common, and (I believe) is for two reasons.

The restrictive turbine, if correctly specified, is reducing lag by turning a larger compressor by slowing the exhaust gases. You improving net gain efficiency at the cost of total flow.

The second reason is that a smaller turbine is less likely to overspin the compressor, melting the blade tips.



So assuming there's some agressive remapping to thicken up the gas flow off boost (which can be tricky - experience has taught me that 'overfuelling' with lots of retard can actually achieve this better than advance and good AFRs...long story to do with flame front speed vs gas density vs gas velocity)
then the clip doesn't affect lag much, but allows the compressors to spin faster, flowing more, and potentially creating more power. It must be noted, though, that as you spin the turbo faster, the net benefit is going to decrease as the charge temperatures go up: which is why we need a bigger intercooler!

The trick with a hybrid is going to be to find a larger compressor that will mate up to a TD03 exhust housing, either by changing the turbine wheel (and thus probably the shaft & cartridge and potentially compressor LOL) or by fitting the larger turbine wheel into a modified housing. Dremmels at the ready, boys!

[Turbo_Steve]

Oh, worth adding that historically it seems the people who 'discover' good hybrid combos seem to either have a bunch of old turbos lying around for no apparent reason and get creative, e.g own a scrapyard / garage / modifying shop that makes a mess of a conversion and needs to rescue it OR it's a nice chap with an e-bay account and very deep pockets who buys all sorts until he's found a fit. (Equally could be a she!).

Anyone got deep pockets? :)

[Kenneth]

Anyone got deep pockets? :)

:inquisiti er, does cutting the lining out count?

[Nutter_John]

hmmm i think not unfortunately

[Turbo_Steve]

Hybrid pockets? :)

[Kenneth]

I didn't think so either... but at least it gives something to do while dreaming about turbo upgrades.


From what I understand, the standard turbo is too small to do anything much with. The limit of modification seems to be clipping the turbine blade and then putting in a bigger compressor wheel.

It seems that the result of doing this causes the nut holding the compressor wheel to come loose and destroy the compressor wheel. (this happened to bradc, and then one of the guys doing a single turbo conversion said this was happening to his, which is why he went single.)

I recall that more than one person has taken his standard turbos to an "expert" and been told that there isn't a lot you can do with them due to their size and you are better off just getting something bigger.

[bradc]

yep, that seems to be the problem.

TD04's, TD05's, GT2554R's or similar seem to be the best options

[Turbo_Steve]

centre nut unspins? That sounds...well like a weird fault....in fact it mainly sounds like the tensioning was wrong.

Unless the compressor is overspinning, but I would have thought that it would physically break something? Just seems an odd failure. Loctite? LOL!

To be honest the more I look at it, the more a pair of TD04s looks like the answer for cheapness vs benefit. Not sure how much room there is, though.

[bradc]

Yeah I thought that too, but it seems strange that multiple people have had the same thing happen.

TD04's will fit, there have been at least 4 people do that now

[Turbo_Steve]

Interesting. A pair of TD04s should take just into 400bhp atw terrirory. Tempting. I wonder what would break first assuming decent fuelling.....

[bradc]

the rods without a doubt

[Turbo_Steve]

Same as the early 4g63s, then? Hmm...shame: won't be taking my engine out. Will have to live with TD03s, then.
Shame it won't be as quick as the car it's replacing, but then it HAS got a lot more load space. LOL