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Discussion Starter #1
Things are happening regarding legal importation of Skylines into the United States - R32 Nismos are now cleared for import.

In any event, 2014 is the magic year when '89 R32s can enter without meeting any crash or emissions standards. And you know me...I've been plotting my second R32, built from lessons learned from my deceased Moby Dick.

Much is known - suspension, ancillary systems (oil, water, fueling), how to properly build a longblock, what components work and which will break...

I'm just undecided on the forced induction part. Twin 2860-5s make plenty of power if you've got the balls to push them. But I'd like to try something different.

And so my thoughts have gone again towards the Group B solution - compound charging. And it does make me wonder why it hasn't been done (or done more often). I want to run a bigger single, one in the 800bhp range, but remembering how much 2860-5s can lag, I'd like to see if something can be done about that.

So the straightforward idea is to stick a Rotrex supercharger where the power steering pump is, and feed that directly into the intake of a T04z, T88, or whatever the latest and greatest single turbo is these days (never did keep track of the single turbo model numbers). An Eaton blower would develop boost quicker, but a Rotrex would be easier to plumb.

So for the experts here, why wouldn't that work (or be far too difficult to be practical)?


I have to admit, driving a 4.2l V8 with twin turbos the size of N1s, maybe even smaller, turbo lag is something I vaguely recall as something I had to drive around and be quick with the throttle. We Americans are quite lazy, and prefer to simply depress the throttle and let everything happen from there.

Speaking of lazy (on a tangent), I drove a NASCAR short-track stock car for a driver experience day. The cars only have four gears, and once you reach 4th, you never shift. You steer (left only), brake with the left foot, gas it with the right, and brace yourself against the surprisingly heavy Gs with your right leg. The torque of the V8 takes care of everything. If that isn't the most American form of motorsport, I don't know what is :p
 

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I would look at what power enterprise in japan did for their R35 GTR and work from there.
More details on Power Enterprise?s quad-charged Nissan GT-R

I remember an aussie car (VL or R31, cant remember) twin charged RB30, went extremely well.
Keep in mind your cooling & fueling needs would need to be pretty high priority if you want it to last.
If you have e85 at the pump, or a WMI setup it will help a lot.

You should also consider compound charging with two turbos i.e. one turbo feeding into another... fairly common aftermarket (and some OEM) on big diesels these days.
 

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Discussion Starter #3
I plan to use water injection, and E85 has become fairly commonplace in the US; the price of it is subsidized by the government, so it's literally like race fuel for 2/3rds the price of regular petrol!!

Fuel flow becomes an issue with E85 however; I used RC Racing 1000cc injectors on my last car (twin 2860-5) and that was right on the money (Sard 700cc injectors kept maxing out, but I was really pushing the boost). With the crap fuel economy of E85, I'll need to flow more fuel...aren't there 1600cc injectors? Or maybe I'll have to rig a second fuel rail and secondary injectors...?
 

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Injector dynamics 2000cc injectors and you're good to go ;)

Other alternatives are stroker kits, rb30 and vcam. Or all three together lol!
 

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Go ID2000s.
If your running 50/50 (or higher Meth) WMI, it should also supplement fueling needs.
Yup, for what you want to do, ID2000's would by far be the best.

As much as twin charging would be awesome, it will be hard to set up correctly, start with a new age turbo (T88 and 2530's are getting long in the tooth as far as tech goes) and go big with a 3.2lt stroker from Nitto.
 

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I'll echo the above guys.

ID 2000's. Idle and drive SO MUCH BETTER than my old Sard 800's could ever dream of. Don't be scared of the size Toby.
 

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Time to start stock piling some quality GTRs before the guys stateside buy them all lol, im VERY VERY curious how this will effect the aftermarket on the older GTRs now that more people will want to buy them in the US, will be awesome to see some fresh eyes and minds on these cars.
 

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With most 'big turbos' now able to start spooling by 2500rpm, surely there is no need for this.

Correct cams, mapping etc are more important in my opinion and as for lag........... I just change down a gear ;)
 

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I was always under the impression that compound charging was done for creating big torque figures in commercial diesel applications? You will need an engine that can handle big boost pressure as well. The new Land Rover 3.0TD V6 has sequential charging with one of the turbos being variable vane. The concept is old technology recycled and refined but would probably cost big bucks to achieve for a one off application.
 

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I come from twincharging an MR2 which has taken me many years and thousands of pounds (related to useless people letting me down but that's another story!)

But it is a FANTASTIC way of getting low end torque and top end power. Recently my little 1.6 (bored out to nearly 1.7) managed (HUB DYNO):

273bhp
230lbft
19psi boost
18 deg advance
Normal fuel.

...from just over 1000 revs the torque was instantly there. Those results are with a bit of incorrect pipework as well, now its fixed I am expecting to do quite a bit better. It'll be an exciting little MK1 MR2.:p
 

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Found this usefull information when i looked into this very system, i will post some diagrammes when i get a chance.

1. This engine is a combination of a roots type blower couple with exhaust gas driven turbocharger ensuring a quick throttle response and power at all engine speeds.

The roots blower on this engine cuts in at approx. 1500rpm and in most situations cuts back out again at 2400rpms and is quite a large size for high efficiency.
At the latest 3500rpm the turbocharger then takes over with sufficient exhaust gases being sent through the manifold. This set up enables a higher compression ratio of 10.0:1 for increased efficiency and better fuel consumption.

THE TWINCHARGER SYSTEM:
Fresh air is drawn in through the air filter. The position of the control flap determines whether or not the air is drawn in through the supercharger and/or directly to the turbocharger. The air from the turbocharger then flows through a charge air cooler and throttle valve control unit and into the inlet maniold.

OPERATING RANGES:
This diagramme shows the operational ranges of the roots type supercharger, turbocharger and cross over points incorporating the two. Depending on torque requirements, the ECU decides whether, and if so how the required charge pressure is to be produced.
The turbo operates throughout the green range and note how the turbocharger alone cannot produce the desired charge at low engine speeds. The supercharger operates in the lower area (dark grey) and a combination thereof in-between.


DARK GREY: Continuous charging via roots blower activated from the minimum torque range (approx 1500rpm) to change over point at 2500rpm.Pressure is regulated from the control flap unit.
LIGHT GREY: The supercharger is activated in response to demand up to a maximum speed of 3500rpm. This is needed, as an example; if the vehicle is driven at a constant speed and then a sudden burst of acceleration is added via throttle input. This also overcomes the lag associated via low inertia at low exhaust gas speeds with solely turbochargers.
GREEN: The exhaust gas is now up to speed and flow so the supercharger is disengaged and the turbo takes over. Charge presure is regulated by charge pressure limitation solenoid valve N75.


IMPLEMENTATION OF OPERATING RANGES:
The engine load and speed range allows the ECU to determine how the air flows into the cylinders for the desired torque. The ECU also decides whether or not the turbo alone can generate what is required or the supercharger is needed.


NATURALLY ASPIRATED OPERATION AT LOW ENGINE LOAD:
In NA mode the control flap is fully open and flows directly to the turbo. Although the turbo is driven by exhaust gas the energy of the exhaust gas is so low that only a small charge pressure is produced. The throttle valve is opened in accordance with the drivers input and a vacuum is produced inside the inlet manifold.


SUPERCHARGER AND TURBO OPERATION AT HIGH ENGINE LOAD AND SPEEDS UP TO 2400RPM
During this period the control flap is closed or partially open to regulate the charge pressure. The supercharger is operated by a solenoid coupling and driven by the superchargers belt drive. The supercharger induces the air and compresses it before pumping it to the turbocharger. The air is then compressed further within the turbocharger. The charge pressure of the supercharger is measured by the inlet manifold pressure sender G583 and regulated by the control flap unit J808. The total charge pressure is measured by charge pressure sender G31. The throttle valve fully open an absolute charge pressure of 2.5bar is present in the inlet manifold.


As it approches 3500rpm for the change-over


EXHAUST GAS TURBOCHARGER OPERATION:
Above approximately 3500rpm the turbo alone can produce the required gas pressure at any point. The control flap is fully open and the air is induced directly to the turbocharger and the turbo can produce enough energy required for the charge pressure. The throttle valve is fully open and an absolute pressure of 2.0 bar can be found in the inlet manifold. Charge pressure sender G31 measures the charge pressure and is regulated via the N75 valve.



ROOTS TYPE SUPERCHARGER
Advantages: Quick charge pressure build up, high torque at low engine speeds, no external oil and lubrication necessary, activated on demand only.
Disadvantages: Consumes engine power due to pulley system, charge pressure is generated depending on engine speed and then regulated, with the result that some of the energy is again then lost.
EXHAUST GAS TURBOCHARGER
Advantages: Very high efficiency through the use of exhaust gas energy.
Disadvantages: In a small engine like the 1.4 the charge pressure generated at low engine speeds may not be enough to produce a decent amount of torque. High thermal load.


________________________________________

DRIVE SYSTEM:
The supercharger is activated when required and driven via the coolant pump via an auxiliary drive. This drive is activated by a maintenance free solenoid coupling on the coolant pump module. If the solenoid coupling is deactivated, three lead springs pull the friction plate back into it***8217;s initial position and due to the high forces involved ***8220;clicking ***8220;is normal. Due to the ratios from thecrankshaft pulley to the roots supercharger pulley, as well as the internal ratio of the supercharger, the supercharger rotates at five times the crank speed. Maximum speed of the supercharger is 17500rpm.
 

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The key in my system was to disengage the supercharger once there was enough pressure to operate the turbo, which is done via a magnetic clutch (standard 4agze supercharger with pulley). So the SC never runs at more than 10psi and my HKS kit is designed so that a change-over valve that connects the turbo-to-supercharging pipe to the intercooler-to-engine pipe opens to allow extra turbo boost to enter directly into the engine and then it bypasses the SC.

It's a tricky system to get right IMHO, and although it is a unique and fantastic way to get low end torque, be prepared to spend a lot of money getting it right, or just go modern turbo.:thumbsup:
 

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Tommygtr: that sounds like a vw 1.4 tsi .... they run great and makes instant boost!

All this week has been spent learning about that and the fiat multiair system along with fsi/gdi systems.
 

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Best leave this to GpB Delta S4's IMHO.

Modern single turbos seem to have address a lot of the issues of old regarding response.....

I get your trying to be innovative but why go through the pain of development when cheaper, proven off the shelf methods of forced induction already exist??

TT
 

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Discussion Starter #17
I had no idea big singles had gotten easier to spool...2500rpm??

anyone care to give me a little primer on the latest singles that can crank an easy 800bhp and spool quicker than 2530s?
 
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