One word...

Legend.

Cheers Mate!!

Nick

Thats the one

Thats what the two 46mm wastegates are for, at higher engine speeds there opening up letting the pressure out of the exhaust manifold effectively by-passing the small turbine housing

Very interesting, well done! Which turbos are you using and what wastegate settings have you set? Are you compounding the boost at all?

Phil, correct me if this is wrong, but this is how I think you have your setup at the moment? I also think it will help others get their head around how you have set it up too.



I think I might have the wastegate off the small turbo exhaust housing wrong?

Square pistons Alexis

No, spark plug cover, duh!

HA

I was going to point out that your square pistons are different sizes, which would effect the engines running due to uneven displacement but I thought.... na

New thread required.........

Totally agree, new project build thread required here Sherlock

What do you expect from MSPaint

Love the square piston idea

While we're at it what would happen if you plugged in one of these gizmos from Lenny Henry country

(http://stores.ebay.co.uk/Brierley-Electric-Super-Chargers?_trksid=p2047675.l2563)

as the low boost small turbo

Do those things have ANY effect at all on an engines performance....
If not, How are they ALLOWED to sell these, stateing "more AIR + more FUEL = More Power"!

Nick

The induction part is right, the wastegates feed into the big turbo not into downpipe

Its the standard t28 and a T3/T04b H-Trim, there both set to run 18psi at there respective wastegates , and yeah its compounding. Its a bit difficult to explain how its working, there not running 18psi at the same time. If you feed 18psi into a turbo thats already boosting at 18psi it doesnt add to it the pressure ratios multiply, so as a PR of roughly 2.25:1(18psi) feeding into a turbo already running with a PR of 2.25:1(18psi) would give a final pressure ratio at the manifold of 4.5:1(54psi).
So the small turbo spools to give a manifold pressure of 18psi at 2700rpm, at about 3200rpm the big turbo starts making boost - not alot but enough to get the manifold pressure upto 26psi at around 3600rpm and it's holding 26psi up to 7200rpm as a high boost setting.
Its setup up so as the PR of the big turbo goes up the PR of the small turbo goes right down so I can keep the boost at sensible levels

This is what I understand

Small turbo at 18psi, big turbo at 26psi. When the big turbo starts producing more than 18psi the small turbo is effectively idling with wastegate wide open. It's not compounding the boost (appart from when the big turbo is spooling up). The big turbo just "takes over" from the small turbo once it's going. Both wastegages must be referenced to the manifold pressure hence it's not technically a compound design but a twin sequential series, similar to the twin charger design of the Lancia Delta S4.

Have you measured the pressure inbetween the compressor stages? I suspect in practice the small turbo will still be adding (compounding) some boost because it will still have a lot of exhaust going through the turbine.

Have you got another picture of how that 2nd wastegate is connected? I assume it just bypasses exhaust past the big turbine like the 1st wastegate bypasses exhaust past the 1st turbine.

Couldn't you use the 2nd wastegate off the manifold rather than having to weld something off the exhaust turbine?

So - the first wastegate off the manifold is enough to prevent the turbine housing on the small turbo becoming a restriction?

Are the two turbos in sequence? ie does the already-compressed air feed into the compressor housing of the second turbo, or is it that each turbo feeds the engine directly

Sherlock - what management system are you using??

Refer to my mickey mouse diagram

Air filter -> large turbo compressor -> intercooler -> small turbo compressor -> intercooler -> inlet manifold

In practice, in the configuration you are using, because all the air getting to the engine has to flow through the first turbo's compressor, isn't the potential power output of the engine limited, not by the theoretically possible pressure ratio attainable through compounding, but by the mass flow that the first turbo's compressor can handle? i.e. the limiting factor is the maximum mass flow of the T28.

This is a question - not a criticism of your impressive efforts!

No, not as you are suggesting anyway as the pressure ratio and CFM is very low, well under the limit for the turbo. Adding the big turbo does not change these parameters.

It would be like fitting a turbo to an N/A engine but leaving the wastegate open so it does not make any boost. So there is a minor restriction there but not in the usual sense. And since this turbo is then effectively turbocharged any restriction is easily overcome with boost.

Not sure what you mean, both of those wastegates are working together doing the same thing at the same time. Think of it as one big wastegate controlling the boost of the small turbo

No, I tried it with one wastegate and it didn't work the boost was creeping up under load

The short answer is - I dont know! I guess at some point it may become a restriction but I dont think i'll ever get it to the point where I need to think about changing anything

come on Lancia did this 20 years ago ...... the way forward is supercharged and turbo charged with a bypass .... always the simple ideas is always the best

i have looked into this for my brothers track day car and we are going big turbo as acceleration is not a priority .... keeping the car in the sweet spot is

yeah, did look into supercharger and turbo but I wanted the characteristics of standard car, the only way to do it is with err.. a standard turbo!