Suzuki 4WD Club of Victoria

There is also the twin turbo Subaru Liberty B4 which is a 2.0 and developed 190kW. The following info is taken from Autospeed.

"Despite being called twins, the B4's turbochargers are not identical. The primary turbocharger is an IHI VF33 unit, which uses a 46.5/35.4mm 9-blade turbine wheel and a 47.0mm/35.4mm 6 + 6 blade compressor. At idle, the turbo spins at around 20,000 rpm and it can go on to a maximum speed of 190,000 rpm. It has a 17mm diameter wastegate opening to bypass excess exhaust gas. The secondary turbocharger is an IHI VF32. On the exhaust side it uses a 46.5/35.4mm 9-blade turbine wheel, teamed with a 52.5/36.6mm 10-blade compressor wheel. It's rated at 180,000 rpm. Both the primary and secondary turbochargers use a floating metal centre bearing - not ball bearings."

"With low ambient temperature and barely any under-bonnet heat soak, we saw a 0.95 Bar peak boost figure in the mid-range, dropping to 0.75 Bar in the top-end. But once heat soak set in after a couple of runs, peak boost slipped to 0.8 Bar and top-end boost remained around 0.70-0.75 Bar. "

By all accounts there is a hole at 4000 to 4500rpm during transition where the primary turbo appears to be maxing out before the secondary turbo has fully kicked in. I had also read somewhere that changes were made later on to remedy this.

What specifically are you wanting to achieve cj! ?

What particular problem are you concerned about with the stock turbo ?
A bigger turbo is required to do what - control exhaust temp, more power, shift the boost curve up or to provide easy to source spares ?

Small engine/big turbo combination's off boost can be awful to drive, IMO its not absolute power that makes a drivable car it "flexible" power. If the engine relies on the turbo to make usable bottom end power then significant change may make things worse in the overall sense. Form what little i've seen of Steve's - the 660 is more akin to a diesel application, the turbo seems to be working to make normal driving power rather than as an addition.

That's where a few more CC's helps..... the engines got more off boost torque to tide you over till the turbo gets working.
With small engines the match is far more critical and involves more compromises.

The main issue is that the stock turbo just doesn't flow enough at the higher rpm and as it has an 8500rpm redline and pretty deep gearing I maybe needing more than it can deliver. It would also be nice to have a source of more readily available replacements if needed. As well, the manifold is such a poor design and the dump pipe is also nothing special that if I make a new ones then I could make them to suit any tuurbo.

I pulled the turbo yesterday to have a look and it has a RHB31 VZ21 turbo instead of the VZ24 that the Cappuccino runs, It appears to be basically the same apart from the exhaust wheel being a couple of mm smaller in dia,

Ok - that makes sense......

If your making a manifold and its done well then it will allow a slightly bigger A/R exhaust housing / wheel to be run - helping with exhaust housing temps and not hurting the bottom end too much.

However making a good manifold is a LOT of work and surprisingly costly. I normally use steam pipe fittings - thick wall, great range and generally friendly to work with, Exhaust pipe is NOT an option... it sags when it gets hot and doesn't last.

As you have limited exhaust energy at low RPM, I wouldn't be going over the top making exhaust housing /wheel changes - have you considered swapping compressor side components or grafting on a different compressor wheel ? I'm no Jap turbo expert but might be worth a look ?

Actually..... I wonder if a supercharger wouldn't be a better option ? SC12/14's are cheap and common.( SC12 = 1.2 ltr/rev, SC14 - 1.4 ltr/rev )

Work out the actual engine air consumption / rev ( not capacity.... ) decide on an approximate boost, you know the blower displacements at atmos... so you can derive a starting drive ratio. Won't be right but will be a start. SC drive is via a 4PK belt, so pulleys are no big deal. I made a concentric system that picked up the crank nose bolts and sat inside the existing pulley. That's where step down is good - you want small most people need step up which is harder.
Going to require step down drive to manage boost, but will be working very easily at the ratio's your going to need, which is going to be a big plus for discharge temperature and long life.

A design that allows some initial pulley changes, a bypass boost controller, some electronics an you could dial your own curve

Just a thought.....

If you look carefully you can see the crank nose blower drive pulley fitted ( bottom of pic ) and see how it drives the SC14 ( top middle ).

And a "bit" off topic but I was browsing my pics so.....

Chris, The 1JZ Turbo has a ceramic exhaust wheel - they are quite fragile in comparison to the "steel" wheel used in the Starlet- they will not tolerate high boost (15 psi being the absolute maximum)

Ross - some reflections on the 660 motors based on my road Cappucino, Greg's Cap conversion and my car -

Japanese Kei-Class rules limit power to 47Kw, but torque is unlimited. As such, superchargers and turbos are kind of "undersized" by normal standards to prevent these motors exceeding this figure and fatten up the midrange as much as possible.

The stock turbo is clearly intended for maximum torque production though the midrange. However, in twin cam engines that can spin, it is clear that even at stock power levels, the turbo is out of flow (actually visible as a reduction in boost) above about 7500rpm. Below that figure, there's also a general lack of fine throttle control at revs which can be a bit frustrating offroad when you are trying to modulate wheelspeed.

I don't see dropping boost at revs in my car, but my rev limiter is at 6500 rpm. Chris's K6A redlines at 8500 rpm and the Caps rev limit at 9200rpm- well past the revs boost falls away. As this happens, based on my experience of the cappucino, the car does really feel "choked" and won't spin freely though to the redline. Even with a free flowing dump pipe and exhaust the feeling is the same - you have to push the car hard to get it to the limiter.

I'd suggest that the suzuki sport turbo is probably sized the way you'd choose if the engine wasn't legislatively power limited, but having said that, it's working within the constraints of stock manifolding which was also designed around only having to flow 47Kw. The exhaust manifold, in particular, is very very tight to pull the turbo in close to the block.

However, the suzuki sport turbo isn't easy to find and is achingly expensive ex japan. If we add to this that there's no requirement for us to work with the stock manifolding for engine, inlet or exhaust, then looking outside of the suzuki sport bolt-in option becomes feasible.

The Suzuki Sport turbo runs to about 120-130Hp depending on tune. I don't think that much power is really necessary - I'd vote 100hp would be plenty, but additionally, I think having a turbo that delievers useful flow and throttle response at high revs (even with a minimal gain in HP) would be nice.

The real catch is finding a turbo from something more readily available that's going to do the job.

Obviously, alot of the tech about turbo sizing seems to all revolve around big HP, and I've experienced first hand what a 180hp 660 feels like - the boost threshold was 5500rpm, give or take. I'm more than aware that that's the last thing a 4WD wants - I have to drive mine around the boost threshold as it is and if I didn't have such low gearing it would not be drivable at all off boost.

AFAIK, the toyota twins run a split manifold - ie three cylinders feed one turbo and other three feed the other. That's where I get (some) of my confidence that the 1GGTE turbo would be a usable option.

The CT12A used on the 1JZ is not such a good option IMHO - each turbo has near enough twice the capacity spooling it and there's been some huge RWKW numbers supported with these turbos in stock configuration - I think Martin Donnon's soarer cracked 240Rear Wheel Kw with these turbos - so they're not all that restrictive to power production even on a 1J, even with a lowish boost threshold due to the ceramic wheels- They'd have to be MILES too big for the 660.

Chris, the tech you've read about these turbo's being used as an upgrade for starlet GT's might be with a hybrid build eliminating the ceramic wheels but using the other parts from the CT12A. The CT12 off the 1GGTE would have to be too small - Each turbo is handling less power than a starlet makes stock so there's no way it will be an "upgrade" for a starlet.

The IHI VF33, from what I recall when Martin Donnon installed one of these in the Cappucino in about 1998, produced about 85RWKw but the boost threshold was up at 4500rpm. I've thrown the issue of "blingy rice magazine" the article was in away but there were dyno sheets for this motor printed. (it was in Hot 4's magazine - maybe an email to Martin via Zoom magazine (or where ever he writes for currently - he pops up all over the place, even Street Machine- might bear fruit)

Just some ramblings.

Steve.

So it sounds like a very turbo dependent motor, with little N/A torque available its going to be a very critical application and when manifolds have to be made... not an quick/easy one either - especially with the scarcity of similar ( 4WD ) applications to base the choice on.

As others have noted whats OK on the street is unlikely to be satisfactory for a 4WD.

So...... why not supercharge - I know we have had initial discussions ?

i wouldn't think room was an issue, fueling is the same turbo or supercharger and will require work no matter what, intercooler can be still used.........

You're right - it is a VERY turbo dependent motor - mine requires 5-8psi of boost to hold road speed while cruising.

There's a similar amount of fabrication involved with either supercharging or turbocharging - we'd still have to build extractors for the 660, and an exhaust to keep it quiet, along with mounting the supercharger, ducting, throttle body positioning etc.

I guess part of the reason Chris (and myself) are still pursuing turbocharging is that there is at least some tech out there for turbo selection and outcomes on these motors and reasearch king Cj is always unearthing more tech from round the world.

I guess there's also some amusement gained from the "less than ideal" power delivery. With the gearing that we're running it's more of a "characteristic" than a major flaw. If we were looking for a more refined daily driver type of outcome then the characteristics of supercharging might be more desirable. Please don't think this is being dismissive, but if we were chasing the best outright outcome we might also be looking at baleno motors... or Mazda BPD's... but part of the nature of these motors is that they drive like a boosted small motor and that really dominates their character- in a good way. Adding a bit more top end without totally ruining midrange is what we're chasing, mostly to remove that "choked" top end feeling.

We're just at the crossroads at the moment as to whether we build a manifold for the stock turbo, look at spacing the exhaust housing etc, or step straight into something a little larger.


If Chris found a suzuki sport turbo at the right price, or a 1GGTE turbo at the right price, that might just make his mind up for him.

Steve.

Fair enough..... we all have our pet projects and sometimes they work and other times.........

Time to do some exhaust back pressure testing ?
Produces a similar feel at higher outputs and without compressor flow maps it could be confused for lack of compressor capacity.

Run it as is,make a measurement - space the exhaust housing ( mild steel welding wire bent into a ring worked on Garrets ) then drive/measure again. If it feels different and the back-pressure has fallen then worth experimenting some more.

That's an interesting idea MM - I assume you mean backpressure in the manifold between head and turbo?

Steve.