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What it all comes down to is tuning. And stock ecu is of course harder to fine-tune then a stand-alone. Of course you can twin-charge stock cars. Run the blower at 8 psi and turbo at 8psi. As all should know, 8psi + 8psi is still only 8psi but you'd see generally twice the volume of air with two compressors (sc and turbo) making boost. Same thing with a twin-turbo setup run in parallel. A lot of times when a turbo runs into the blower sequentially, the boost will increase on it's own so good tuning and careful tuning will be important. Blower and Turbo selection are extremely important, even more important when twin-charging a car.

 

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Originally posted by lo bux racer@Dec 23 2004, 05:08 PM
It's not only 8 psi. Compressors work with pressure ratios. If I feed a turbocharger air at 8 psi and it has a 3:1 compression ratio, I'll get 24 psi out. It's pretty obvious if you look at the compressor maps.

Did you ever see a tractor pull with triple charged diesel? They push 200+ psi because each of the three sections multiplies the output of the last. Even with a moderate 2:1 ratio, you end up with 8 times atmospheric (117 psi at STP) without accounting for pressure rise from compression heating.

The trick with twin-charging is to set it up for the supercharger to work at low rpm and the turbocharger to work at high rpm with a switchover strategy. That's how HKS does it to provide the best of both worlds.

I am talking about compound twin-charging. You are talking about something different. If I were to use a screw-type whipple, then your point would be correct. The 200psi example you supplied was because each turbo fed into the next one to force air into it, spinning it from the compressor side as well. (This diesel engines are badass turbocharged.) This is called running "In Series." My compound twin-charge example was using a Roots blower, you should know why this is different then your example. Roots superchargers are not compressors. DING. They work great for compound charging, hence the reason I used one. You don't need a clutch on your blower, but this obviously would be the way to go if you want life to be easier. Too bad the only ones around with a clutch are really small. Toyota makes a couple for the 1st gen mr2, one for 1800cc and the other for 2000cc and mercedes used a few clutch'd eatons as well. The whole idea of twin-charging is to have low down torque from the blower and top end horses from the turbo.

 

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Originally posted by lo bux racer@Dec 30 2004, 03:25 PM
I must be stupid. I had a AW11 with the 4A-GZE, and I'd swear it was a 1.6 liter. Wait, that's what everyone else on the web says too. Hmmm. Great info.

You just have no idea who I am or what I know, but you keep trying...

I know what a 4a-ge and 4a-gze is, I have worked on a both of them. I was refering to the ammount of air the toyota supercharger is supposed to be able to flow before being useless. After reading it, I see where you would think I was saying the 4a was 1800cc, I know it's a 1.6L. I don't double-check my forum posts, looks like I should. My point is that there was two different toyota superchargers made with clutches, one was on the 4a-gze and the other on a 2.0L v6 1G-GZE, found in Japan. The stock ratings for the two Toyota blowers is lower then with the HKS pulley, or any other aftermarket one, but stock they put out 1200cc (SC-12) and the SC-14 puts out 1420cc (.7 bar.) And yes, with the smaller pulley they will put out quite a bit more air but they are small and become less efficient if you push them too far. The mercedes one also uses a cluctch and I am pretty sure it was offered on a 2.2L engine, so it should flow a bit more then the toyota ones as it is, stock. Sorry for not being specific. And no, I do not know you and you don't know me so try to read what I type before commenting and I will do the same. I am not here to be a dick, but I am not an idiot as you are making me out to be. I am actually a well respected member of the All-Trac community, so I do know quite a bit of usable information and have people that will vouche for my knowledge. But did you see what I meant about the compound setup I was refering to and how boost does not increase how you thought it did when you aren't using a true compressor? Roots blowers aren't true compressors, that is why I said the boost won't go to insane levels when used in a compound setup. Only a true compressor will increase the boost on a ratio, like you explained. Do you or do you not agree with that?

 

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Originally posted by lo bux racer@Jan 3 2005, 03:38 PM
I am actually a well respected member of the Supra community at www.mkiv.com. I am also familiar with the ST185, and have a few friends in that community as well.

Calling a Roots blower "not a compressor" is semantics. It is a compressor or it could not build pressure. It just happens to be the least efficient of all compressors at about 60% (with new rotor seals). If you feed it pressurized air, it will put out more air than it would at atmospheric, just like any other good compressor. I completely agree it is the least desireable of all the supercharger types available. I'd take a Lysholm or Whipple over a Roots in a second.

Insane boost is a relative term. It's hard to find insane on a 2JZ, however, the 2AZ is not cut of the same cloth. It won't matter much how you pressurize the air with a 2AZ, the block just isn't up to much boost without major modification. Here is where I take strong exception to your statement "it all comes down to tuning". The block will not support high boost without major mods. Why are there no 1000 hp NSX's? Their blocks don't support boost without cracking very shortly after they are boosted. The tC will suffer the same fate. I'd be surprised if the stock unmodified block will tolerate even 8 psi for any significant length of time before it cracks.

AFA compound boost, twincharging isn't compound boost (semantics again). Compound boost is putting multiple compressors in series. Twincharging is using one method at low rpm, and another at high rpm to make a small engine perform like a big one (for the most part: BSFC says little engines with forced induction still need more fuel to make the same power). I understand the concept just fine, and I followed Toysport's MR2 Twincharging project many years ago. I have also seen one in the flesh at a shop near my house. They go really well with good fuel in them.

In any case, they make power down low with the supercharger and switch over to the turbocharger once the combination of rpm and load supports the turbo moving more air than the supercharger can move efficiently. The turbocharger is also inherently more efficient than any supercharger (except a Vortech, because a Vortech is just a gear driver turbo compressor section). I understand all this just fine.

A roots blower is considered to be a positive displacement pump, it is not a true compressor. I have a few books and if you would like, I can provide some links to this info. A whipple is a lysholm, they are sold to us as Whipples when Lysholm manufactures them.

Of course the engine can be weak from the factory, I am saying if it is tuned correctly, a tC will take a decent ammount of boost before failing. Even honda engines do great with boost when tuned right. Your headgasket is likely to go before you put a piston out the side of your block. I have some pretty high faith in toyota, seeing the insides of many engines, you can tell they do #### right the first time around.

I think I told you already how it is considered compound charging; when the turbo is ran into the blower and the blower is ran into the intake manifold. This is only one example of the many ways one can compound-charge a car. The whipple supercharger is as efficient if not more efficient then most turbos out today. They really are amazing. I am talking 80-85% efficient, when most turbos max out at 70%. Whipple's own website can confirm this for you, look around for dynos with whipples, you will see what I mean when I say they are badass. The Vortech is actually rated to be 70-75% efficient, plus or minus of course.

-Steve