compound charging/twin charging

[Yowzer]

TBH I'd go for it, not every car has to be built to the highest efficiency / driveability / performance etc whatever, especially when it's just for a bit of fun.

Just do it for the wank factor, experience, knowledge and so on.

Fully keen to try this on my diesel, so I may just do so....

There's a lot of cats here dishing out contradictory information on the subject, yet none (including me) have ever had any 1st hand experience with this sort of setup. It's all just repeating other peoples opinions that they have heard from.

[Simon]

I looked into it ages ago when I got my MR2,

Then thought about it again since then.

Asked about it on a couple of forums and talked to a few people - Dad's turbo technician and fuel injection specialists etc.

They said if you are trying to do it after market it's a waste of time and you will spend heaps of time and money trying to get it to work and it will never get finished / blow it up.

Steve (turbo tech) said it is pretty much only worth it for a gymkhana type car that has lots of on and off bursts at 100% throttle.

He reckons a properly built turbo system will be over 9000 times better for a car that is going to be on a normal track and lols at the thought of a road driven one compared to a nice turbo setup.

So with that knowledge I bought a higher displacement motor and will run slightly upped factory boost through and it will go for ever while making heaps of power.

thanks mate a appreciate that.

but i still want to give it ago and i have pretty much all i need to

put it together .

and like i've said before if it doesn't work i really don't have a problem

changing it for a different setup.i just like to try things for myself.

and saying that there's nothing stopping me trying both ways out.

Yeah go for it, while I am telling you there are better ways I understand you probably already done that and you just want to give it a shot.

Prove us all wrong and it will be awesome.

Hell I want to strap an SC under my Alto carb. Probably never will because everyone says don't bother.

[RUNAMUCK]

Sorry Dan, I must have had brain fade.

If you have the turbo and blower you mentioned above, Id use the blower to spool the turbo and then have it cut out. reason being once your nice big turbo is spooled the blower clutch disengaged and the power being generated at the crank isn't being wasted by turning a pump that you don't need.

Have you ever seen John Van beeks old supercharged CA18DET (Minus T) 1200 coupe? That went pretty hard on "I think" 9psi. (Matt who owns it now has sqeezed a 13.7et out of it) So running your two pumps in a non (true) compound charged fashion could give you 9-10psi from idle, and your big dirty turbo kicking in far sooner than it outherwise would have. Then when you're doing a max speed run you wont be wasting horsepower turning a blower that is doing nothing.

[Yowzer]

Question that I expect another huge debate over; would this work?

Supercharger feeds into turbo, feeds into IC into engine. There is a bypass pipe past the SC with a one way flap / valve thing in it. When flap opens, switch is toggled to deactivate SC clutch.

Charger runs at low revs, at low boost (~5psi). Turbo then spools up to ~10psi.

Here is where I get a tad uncertain as to what will happen...

Will the turbo start to draw enough air in to bypass the SC and shut it off, or will it end up having the same compound effect as discussed before?

[H05TYL]

I've been keen to try a compound setup on my 4G63 for a while now, but I've not been able to get hold of an SC14 yet. Once I manage to find one I'll prove it's awesome (or not).

[Yowzer]

They are all over trademe for $200-$300 usually

[Testament]

Sorry Dan, I must have had brain fade.

If you have the turbo and blower you mentioned above, Id use the blower to spool the turbo and then have it cut out. reason being once your nice big turbo is spooled the blower clutch disengaged and the power being generated at the crank isn't being wasted by turning a pump that you don't need.

Have you ever seen John Van beeks old supercharged CA18DET (Minus T) 1200 coupe? That went pretty hard on "I think" 9psi. (Matt who owns it now has sqeezed a 13.7et out of it) So running your two pumps in a non (true) compound charged fashion could give you 9-10psi from idle, and your big dirty turbo kicking in far sooner than it outherwise would have. Then when you're doing a max speed run you wont be wasting horsepower turning a blower that is doing nothing.

You don't even "have" to have the clutch on the supercharger - When the bypass opens the supercharger stops doing any "work" in the thermodynamic sense and so doesn't really draw sfa power to turn (similar to revving your engine in neutral).

[Truenotch]

Good to see this is starting to get back on track.

Need an engine bay shot of this thing I think

[Brock-Lee]

My god, get back on topic. This nitpicking has nothing to do with twin charging.

Rookie is new to the forums, he isnt hiding behind a fake account.

[Spencer]

Yup just state your facts with no name calling or we can this thread and send out some warnings

[nismo.capri]

From: http://en.wikipedia.org/wiki/Twincharger

A twincharging system combines a supercharger and turbocharger in a complementary arrangement, with the intent of one component's advantage compensating for the other component's disadvantage. There are two common types of twincharger systems: series and parallel.

[edit] Series

Series arrangement, the more common of the two, is plumbed such that one compressor's output feeds the inlet of another. A sequentially-organized Roots type supercharger is connected to a medium- to large-sized turbocharger. The supercharger provides near-instant manifold pressure (eliminating turbo lag, which would otherwise result when the turbocharger is not up to its operating speed). Once the turbocharger has reached operating speed, the supercharger can either continue contributing pressurized air to the turbocharger inlet (yielding elevated intake pressures), or it can be bypassed and mechanically decoupled from the drivetrain via an electromagnetic clutch and bypass valve or one-way valve (increasing efficiency of the induction system).

Other series configurations exist where no bypass system is employed and both compressors are in continuous duty. As a result, compounded boost is always produced as the pressure ratios of the two compressors are multiplied, not added. In other words, if a supercharger which produced 10 psi (0.7 bar) (pressure ratio = 1.7) alone blew into a turbocharger which also produced 10psi alone, the resultant manifold pressure would be 27 psi (1.9 bar) (PR=2. rather than 20 psi (1.4 bar) (PR=2.3) This form of series twincharging allows for the production of boost pressures that would otherwise be unachievable with other compressor arrangements.

However, the efficiencies of the turbo and supercharger are also multiplied, and since the efficiency of the supercharger is often much lower than that of large turbochargers, this can lead to extremely high manifold temperatures unless very powerful charge cooling is employed. For example, if a Roots blower with an efficiency of 60% blew into a turbocharger with an efficiency of 70%, the overall compression efficiency would be only 42% -- at 2.8 pressure ratio as shown above and 20 °C (68 °F) ambient temperature, this would mean air exiting the turbocharger would be 263 °C (505 °F), which is enough to melt most rubber couplers and nearly enough to melt expensive silicone couplers. A large turbocharger producing 27 psi (1.9 bar) by itself, with an adiabatic efficiency around 70%, would only produce 166 °C (331 °F). Additionally, the energy cost to drive a supercharger is usually several horsepower, thus if it can either be disconnected electrically (using an electromagnetic clutch such as those used on the VW 1.4TSI or Toyota's 4A-GZE) or allowed to freewheel and vent to the atmosphere, several horsepower can be gained independent of the efficiency gain by switching to one compressor.

Thus, switching the supercharger off at a certain boost or RPM threshold is most desirable, since a large, inexpensive journal bearing turbocharger can be used which will provide more than enough pressure and flow at any RPM for most twincharged motors. However, a smooth switchover can be very difficult to accomplish for non-OEM twincharging applications.

[edit] Parallel

Parallel arrangements typically always require the use of a bypass or diverter valve to allow one or both compressors to feed the engine. If no valve were employed and both compressors were merely routed directly to the intake manifold, the supercharger would blow backwards through the turbocharger compressor rather than pressurize the intake manifold, as that would be the path of least resistance. Thus a diverter valve must be employed to vent turbocharger air until it has reached the pressure in the intake manifold. Complex or expensive electronic controls are usually necessary to ensure smooth power delivery.

[nismo.capri]

As the wiki says "this can lead to extremely high manifold temperatures unless very powerful charge cooling is employed. For example, if a Roots blower with an efficiency of 60% blew into a turbocharger with an efficiency of 70%, the overall compression efficiency would be only 42% -- at 2.8 pressure ratio as shown above and 20 °C (68 °F) ambient temperature, this would mean air exiting the turbocharger would be 263 °C (505 °F), which is enough to melt most rubber couplers and nearly enough to melt expensive silicone couplers."

Heat and dealing with a PR's over 2 is why I think Dan should be going for a parallel or series not compounding setup. If there's going to be a by pass it would be best to do it after the turbo before the flapper valve. VW disagrees as they went for series with a clutch on the blower and a by pass valve (as per Sisu's post on page 2) the big issue for either is how to you control the vent or crossover valve. I think the best point to monitor would be the exhaust manifold before the turbo as you'd be able to have a set point where at X pressure the turbo would switch in, this would guarantee that the turbo was spooled. The problem is that the manifold will end up glowing red hot and cooking an electrical sensor or melting a pressure diaphram.

The other option I can see is using a Mass Air Flow sensor and an electrically controlled valve this way the set point would be set to a certain flow point, this flow point would be ideally when the turbo is matching the flow from the blower. If you wanted to get really wanky may be run 2 MAF's 1 on the intake and 1 after the blower, when the MAF after the blower is measuring half the intake MAF it would mean that the turbo is by passing the same mass of air as the blower and because it's measuring mass it would be adjusted for air temp and altitude.

All the info I can find says valve or electronically activated valve but not it's set points.

[nismo.capri]

For you compound boost guys

"The test car is a bone stock 04 Cobra (other than fuel system mods of course). With the Turbos at 26 PSI the engine saw 44 PSI and made 1200 RWHP and 1000 RWTQ! They made a pull at 65 PSI but the heads lifted... This kit is 100% legit and will definitely make the #'s that are claimed."

[nismo.capri]

[bubblegoose]

what about a big reed block/box after the sc, then the sc can be left on or turned off. when turned off the turbo can draw though the reeds without any need for fancy mechanical valves

or am i dreaming?

[RUNAMUCK]

For the shutoff valve, just plumb a throttle body into the line which prevents the air compressed by the blower going back out the turbo charger. Then run a hobbs switch to cut out the blower clutch/actuate (like with a subaru leone central locking solenoid) the thottle body open once the turbo has spooled up. Then the boost from the turbo is flowing freely past the supercharger, which just lies dormant .

Just like this but using a mechanical valve rather than a flapper valve.

(And having the blower before the intercooler as I mentioned a few posts back)

That'll give you nil lag (even with the sweet sweet four port head) and sledhammer like acceleration in the mid range to top end.

[nismo.capri]

Just like this but using a mechanical valve rather than a flapper valve.

(And having the blower before the intercooler as I mentioned a few posts back)

That'll give you nil lag (even with the sweet sweet four port head) and sledhammer like acceleration in the mid range to top end.

Too simple! I was thinking that was electrical duh!

[Brock-Lee]

Thread is now cleaned up. Keep it on topic or I will hulk smash you.

[nick_m]

Apart from rookie not playing nice. Why was his post removed, it had good info in it

[Honda Ass Dragger]

Good to see this is starting to get back on track.

Need an engine bay shot of this thing I think

Hey Marku how does that prelude actually go?

Seen it on trade me for ages was always intrested in finding out more about it