Project Thread The 2JZ-GZTE Project

[cribbj]

Shawn, I have an existing HKS type S FMIC on my Supra that I'll probably just leave in place initially, although it's really too small for the kind of output this motor should produce twincharged.

Then I'll use meth/water injection after the superchargers, and will probably mount a small meth/water nozzle just before the SC's also, just to keep them cooled down. The meth/water setup has worked really well on my supercharged 1UZ during past dyno runs, and we've been able to cool the charge air down over 90 degrees, when injecting straight methanol.

 

[JustenGT8]

Cheers Justen, my memory is playing tricks on me again - I didn't remember that you'd lost power with the twincharge setup. And that, in spite of quite a bit more boost pressure? What was going on there?

Did you have any interstage cooling or were you just injecting M/W at the manifold?

Yeah once i got it on the dyno i was more than a little surprised top end was down that much A total animal to drive though so if it weren't for the 25psi you proabably wouldn't care

Like i said i'm guessing the power loss was a combo of intake charge heat (should have theoretically been up over 100 deg C), the smaller M90 struggling a bit and possibly the massive increase in exhaust gas flow choking things in the smallish turbine housings?

From turbos intake went thru my normal 600x300x100 FMIC, the TB with WI then SC....no post SC WI which is something i would do in future.

Compound boost also means compound inefficiences and they are also multiplications so you will reach a point of dimishing returns. I think my less than optimal setup was simply past that point.

Going to an M112, bigger turbine housings and WI post SC would have done the job nicely i'm sure.

 

[cribbj]

Hmmm, I'd like to believe it was the little turbine housings choking the exhaust flow, and backing everything else up, but they were there when you were running on turbos alone.....

But maybe they weren't so restrictive for a 4.0l "turbo only" motor, but for a 7.25l "pseudo" motor already being boosted to 12 psi by the superchargers, perhaps they were in fact the restriction.

Also, you were probably losing at least 30-40kW driving the supercharger, so in fact you were probably making well more than your turbocharged runs.

Do you remember if your ECU pulled a ton of timing due to the intake air temps?

Probably a combination of all the above, as you say.

 

[JustenGT8]

I didn't do a log of the runs as was on the video camera...teh dyno guy was freaking as it kept climbing out of the rollers so he wasn't thinking straight at the time either

I did stick my head in quickly and the intake was at 40 deg C but could have just come down that quick with the water injection still running.

Just doing the math had the intake temps up over 100deg C in which case the ECU would have pulled a fair bit of timing.

As a quick and dirty exercise it definitely showed the potential of twincharging....just needed refining....will give you something to do on the engine dyno for a few days ;-)

 

[stevechumo]

With the single FI system, it's easier to resolve the heating issue. I believe if twin charge such as the system as Justen's, the power will be gained more along with less heat if the turbo's air can go into the intake chamber but after the supercharger. I think the M90 was complained by many users due to its heat. The intake temp on my setup on the dyno was only around 100 Farenheit, which is 37 Celsius.

 

[Zuffen]

I'm lost!

What has a dry sump to do with intercooling?

Maybe I need to study cars/engines some more, as I must be a total idiot.

 

[JustenGT8]

I'm lost!

What has a dry sump to do with intercooling?

Maybe I need to study cars/engines some more, as I must be a total idiot.

I think he means the dry sump would allow you to lower the engine and hence have more room for the 'sandwich' style IC below the SC....as still clear the bonnet ;-)

 

[cribbj]

I've been studying the "MR6 Compound Boost" project that Jeff Hartman, Corky Bell, Bob Norwood, and others did back in 2003 and 2004. This project was done with a 3.0l V6 Toyota engine, an M62 based TRD supercharger, and a range of turbos from a T61 up to a T76.

It appears they experienced compound boost levels being too high, and not generating the corresponding level of power. Other compound boost projects (Hellion kits, etc.) seem to have the same issues, so Justen's experience of losing top end power with the compound setup having 1.5 times more boost pressure than a turbo-only setup wasn't an anomaly after all.

What I haven't found as yet, is a good overall reason why this occurs.

What I'll try to do to minimise this, is to not get into the compound boost situation at all, hopefully by modulating the superchargers' bypass (recycle) valve(s), once the turbocharger is up on boost. In other words, swapping 15 psi of supercharger boost for 15 psi of turbo boost, and simply blowing through the superchargers and their recycle valves.

Once the boost is being produced solely by the turbocharger (perhaps with some residual boost coming from the superchargers), it'll then be controlled by the wastegate in the usual way.

Here's a schematic of the system as I envision it:



And a table showing the dangerous levels of compound boost that will result if there is no control over the supercharger boost (the upper table is without control, the lower table shows what happens when the superchargers are running in bypass or recirculation). Note these tables don't take into account the drop in density ratio - they're simply a quick calculation of compound boost.



And a graph showing the runaway compound boost pressure if the supercharger recycle valve isn't used:



And running the superchargers in recycle from 3500 RPM onward (or whenever the turbo starts making boost):



Hopefully, another very important side benefit of running the superchargers in recycle at the top end, will be the regaining of their parasitic losses, which I've calculated to be close to 50 HP gross, of which we should gain around 40 back (we'll still have all the frictional losses of driving the jackshaft, belts and superchargers, but as they won't be moving any air, no compression work will be done.)

Unknowns at this point are:

1) What size turbo to use? I'm envisioning one with a large turbine, and big A/R ratio, but only a small to medium size compressor, like a T61 or T66. The goal is very late spool, and only modest boost pressure, so I'll need to find a switched on turbo vendor who can think outside the normal box for this setup, as it's nearly the inverse of what most people want in a turbo.

2) What happens to the system during transitions, ie will it switch from superchargers to turbo and back again smoothly? This will probably take some fine tuning of the controllers.

3) Turbine inlet pressure (exhaust backpressure). We'll monitor this with an eye to changing out turbine housings to keep it under 2:1, to avoid excessive "backup" of the system as Justen suspects happened with his twincharge setup.

 

[JustenGT8]

Pretty sure we had talked about using the bypass valve this exact way John when i was setting up mine. Should be doable with either a dual port wastegate or solenoid controlled vac circuit.

It'll need to be big valve though and even then i reckon you will still get some compound effect as you won't equalise pressures across the SC completely....if your turbo is making boost then straight up there's a differential across the SC eh.

As for turbo, check some compressor maps...i think you want a big compressor that'll make good flow at low boost...with an equally monster turbine a/r.

I'd start by just living with the compound effect, size the turbine for you new 'virtual engine', throw a heap of water/meth post SC and see what you get.

As i said, the inefficiencies are compound as well so it'll never be perfect but an optimised setup should give you pretty near the best of both worlds (bottom and top end grunt)

 

[Arnout]

That GTZE project I built was a celica 4wd (ST205) with a built 2 liter 3s-gte. I used the SLK230 supercharger (with clutch) and the GT40 turbo with a huge hotside of 1.01 or something (which is big in T4 housing).
That car is awesome. I put the supercharger before the turbo, so the supercharger blows through the turbo. In that way I didn't get any compounding effect.
That Supra I'm building (the 2jz picture) I will try the supercharger after the turbo and I will expect some compounding there. I don't know how I will deal with the compounding or how I will overcome it or something, but we'll see once it's in the car and we can play with it. Or on the engine dyno that I'm buying.

 

[hungryforinfo]

Can the pressurised air running into the low pressure intake of the supercharger do damage? Do the chargers need to be modified?

Wouldn't the boost from a charger create much more exhaust from idle, thereby decreasing turbo lag (good thing) but its confusing for me.

Would it be possible that the boost could be higher without you wanting it? (i.e. above the 1 bar from each item?)

I know there was a stock Volvo that was supercharged and turbocharged, but it had a VERY complex engine management system from memory.

 

[cribbj]

Q1: I can't envision this happening, however there's really no difference between this condition and the one where we have high manifold pressure at the discharge, and low inlet pressure at the suction. And if you look at the inlet and discharge ports of these little two rotor Roots blowers, they're identical.

Q2: Yes, but I actually want turbo lag in this application because I really do not want to be in a compound boost situation.

I don't want the turbocharger spooling up and coming on boost at all in the low to mid RPM range. I only want the superchargers producing boost in the low-mid RPM's. That's why I'm looking for as large a turbine section as possible. If by sizing the turbine as large as possible doesn't do the trick, then I'll use the wastegate as a secondary means of discouraging the turbine from spooling.

Q3: Accidentally? Or purpose built? Accidentally, certainly but there will be overpressure protective devices in place in case the boost controllers fail; that's just good design practice. For a purpose built system, it would be very easy to generate 50-75 psi of boost in a multistage compound compression situation, but that's not my goal, nor do I even want to think what it would cost to build a motor to withstand that boost level. I understand the semi-professional tractor pulling boys are running 2x to 3x those levels, and they occasionally have overboost issues: Tractor Pull Overboost :yikes:

I believe the boost control system will probably be the most complex and interesting part of this project. Getting the superchargers in & out of recycle mode, smoothly and seamlessly will be the key, and this will be down to getting their recycle valves sized right and operating smoothly.

 

[hungryforinfo]

Q3: Accidentally? Or purpose built? Accidentally, certainly but there will be overpressure protective devices in place in case the boost controllers fail; that's just good design practice. For a purpose built system, it would be very easy to generate 50-75 psi of boost in a multistage compound compression situation, but that's not my goal, nor do I even want to think what it would cost to build a motor to withstand that boost level. I understand the semi-professional tractor pulling boys are running 2x to 3x those levels, and they occasionally have overboost issues: Tractor Pull Overboost :yikes:

I believe the boost control system will probably be the most complex and interesting part of this project. Getting the superchargers in & out of recycle mode, smoothly and seamlessly will be the key, and this will be down to getting their recycle valves sized right and operating smoothly.

Yeah, the Volvo had the computer management monitoring and reducing fuel input and variable turbo to control the boost.

For most of us controlling the boost in that situation is next to impossible. Good luck its a MAD project and you look to have the skills and knowledge to get it done. I seriously considered it on a 1UZ but wrote it off as being beyond my current level of knowledge.

 

[cribbj]

The throttle linkages are now fabbed up, and I installed the extended spacers between the TB's to keep them fixed and in the same plane at all times (they're softmounted to the SC's, using the OEM rubber spigot flanges).

The throttle linkages work, but they're pretty flimsy, and I'm thinking they'll get out of sync very easily. Good thing this isn't a permanent solution, but it's a lesson for the future. I think the best way to do this in the future will probably be extending the throttle shafts themselves, and putting anti-backlash couplings between them.

Thought I had the extensions for the little fuel rails between the Suzuki injecters sorted out. They're an odd size of heavy wall ally tubing and I tried to pass a larger OD ally tubing over them, and TIG it, but that plan failed miserably.

I now have some 10mm stainless heavy wall tubing that I'm going to try to get o-ring grooves cut in. Hopefully that'll work, because I intend to use the little Suzuki injectors to spray methanol straight into the SC intakes to keep them cool. These are only 215cc/min injectors, and I figure if I PWM them down to 20% duty cycle, or thereabouts, that should be sufficient.

I'm trying to get the little fuel rails sorted out so I can deliver the whole assembly to that black hole known as "The Engine Builder" so he can do the drive system. That should take anywhere from a month to a year or two.....

 

[JustenGT8]

Even with just the SCs it'll be a hoot to drive and a real eye opener for anyone who gets the priviledge of a look under the bonnet