(03-28-2013, 03:43 AM)Eric78 I already bought a Holset hx35 but this probably isn't enough for the power I'd like, would this & an hx40 work together in a compound set up? If not which turbo would you recomend to go with the hx35 in a compound set up on an OM605?

(03-28-2013, 05:54 AM)EDH_Performance

(03-28-2013, 03:43 AM)Eric78 I already bought a Holset hx35 but this probably isn't enough for the power I'd like, would this & an hx40 work together in a compound set up? If not which turbo would you recomend to go with the hx35 in a compound set up on an OM605?

hx35 and hx40 is to close to eachother...An hx35 and hx52 will be a good match!

(03-28-2013, 10:45 AM)willbhere4u I was thinking of using the stock turbo that comes with the om606 but compound it with a Holset hx35

(03-28-2013, 02:43 PM)EDH_Performance I am currently building a setup for my om606, compounding a hx40 with billetwheel and a big hx60 with custom ezhausthousing

(03-28-2013, 10:13 PM)MFSuper90

(03-28-2013, 02:43 PM)EDH_Performance I am currently building a setup for my om606, compounding a hx40 with billetwheel and a big hx60 with custom ezhausthousing

I am sure you have some major fuel modifications?

(03-28-2013, 05:54 AM)EDH_Performance [quote='Eric78' pid='50165' dateline='1364460182']
...An hx35 and hx52 will be a good match!

(03-30-2013, 05:08 AM)EDH_Performance An hx55 is good for over 800hp...how many hp do you aim for?

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An hx55 is good for over 800hp...how many hp do you aim for?

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An hx55 is good for over 800hp...how many hp do you aim for?

(02-12-2014, 04:15 PM)Hario I am compiling components to compound also. If you use a hx35 as the primary turbo will make for a very laggy and peaky power curved engine.
My plan is to use my factory manifold and turbo (om606), and machine a flat onto the factory manifold to allow me to mount a wastegate to bypass the factory turbo to allow the restrictive factory turbo and manifold to not restrict flow. The hx35 will then be the secondary being fed by the factory turbo exducer and the aditional wastegate. The hx35 will also be wastegated of course.

I realise I said the word factory far too many times in that paragraph..

Quote:Not a stupid question, and you're not overthinking things. First off, you're way ahead of most people who just say "set the secondary at twice the boost of the primary". However, as you know, boost ratios and PR are NOT the same.

I went through this about a year ago as well, with my 62/476 install. It's somewhat hard to find helpful, technically accurate information on tuning twins (at least from what I could find). Nonetheless, here's what I've found out on mine.

You're going about it right, in that you want each turbo to share half of the "work"...and this means running equal PRs. However, from what I've experienced, it's not possible for this to happen in reality. You can adjust the wastegate on the secondary so that PRs on the two turbos match at one condition, but they won't match at any of the other conditions.

Since the secondary begins to spool much faster, its boost climbs quickly to about 10 psi before the primary begins to make a pound or two. The secondary continues to build boost faster, up to the point that its wastegate cracks. When the wastegate opens on the secondary, the primary begins to pick up speed much quicker. This (obviously) is because the primary is now receiving a larger percentage of the exhaust flow, and it's "higher quality" exaust due to the higher temperature of the wastegated exhaust...it is also beginning to get into the mass flow rate of air where it was designed to operate.

Thus, when you reach this point, the primary now begins building boost much quicker than the secondary. As such, neither of the turbos spool linearly with respect to each other. The small one spools quicker at first, and tapers off as the wastegate cracks. The big one is slow at first, and gets a kick in the pants as the secondary's wastegate opens. Because of this non-linearity, I've not found a way to maintain a constant shared PR across the speed/load operating range of the engine.

The best I've been able to do, is to set the wastegate on the secondary such that you are at a 1:1 PR ratio with the two turbos at about 75 - 80% of full horsepower. This allows the small secondary to spool quickly and get you going. At full 100% hp, the primary will be doing more work than it should; however, for daily driving, this has worked better for me. It does make the primary have a higher PR than the secondary at WOT, but it allows the PRs to be more closely matched in the 40 - 75% throttle range where I normally tow/drive/need boost at.

For an all-out-best dyno number, it may be better to match PRs at 100% load, but I've found for a daily driver/work horse, a little lower does better. For what it's worth, with my ~650 hp worth of fueling, the 476 primary never sees much more than 25 psi on a WOT run. Thus, unless you are too heavily fueled for the set of twins you have, I don't think there is much tuning to be done with the wastegate setting on the primary...as long as you aren't letting it crack before 25 or 30 psi and "wasting" exhaust energy.

Again, the above info may or may not be accurate, and may not be the best way of doing things. It's just what I've found to be true with my limited knowledge and my setup.

--Eric

(02-13-2014, 01:03 PM)raysorenson Not mine, just grabbed from google image search. Yes, crazy- and looks like great work.

How about building one of those F.R.A.S.? :-)

(02-13-2014, 07:27 AM)F.R.A.S I'm a total newbe on compound installations but I have some experience of building fast cars When thinking about this compounding there are some issues that comes to mind.

Exhaust flow and exhaust gas velocity (if that's correct in English).

Normally you build a exhaust manifold the way that you can obtain the highest gas velocity possible (same length primary pipes is not always ideal if one is straight and one is bent 720-degrees). Now to the compound problem. Building a good manifold for a small turbo and then when boosting drive the big turbo via an external wastegate and the small turbos turbine flow... That's shit really!

And building a good exhaust manifold for the big turbo and propelling the small turbo via a wastegate actuator is also bad. Yes you can of course open the wastegate with the vacum pump and close it with boost. But the small turbo are to spool as fast as possible. And propelling that fast spooling turbo via a bad flowing wastegate solution is not really the way to go.

So how do you build a twin exhaust manifold that can get the most out of both turbos? The first problem is cutting of the manifold that is not in use... Solving that problem might be a couple of hours of sketching and some headache. Using the exhaust gas valves from a sports bike might be something, to big though and not 100% seal.

Now to the question. How is this done to be as efficient as possible? How does You guys make this work? And how is the setup made on stock cars like the BMW 123d?

I would love to understand this better.

(02-13-2014, 11:47 PM)shadowmaker Efficiency improvement comes from two (or more) turbos acting together. If calculated correctly, they'll stay at their best efficiency islands and still have very wide operating range, which isn't possible with single turbo setup. This efficiency improvement surpasses manifold efficiency at least ten times.

And no, I'm not the one, who thinks that frequency pulses don't matter in turbo engines.

Quote:folks are getting drive pressure down to 1:1 with boost

(02-13-2014, 05:01 PM)F.R.A.S This setup is no problem building. But the question is if you can make this more efficient.

(02-15-2014, 01:18 AM)shadowmaker Nope. Actually the big one will spool almost immediately after the small one. Now where did it get that extra exhaust gas velocity to do this?

(02-15-2014, 03:40 AM)Turbo ...aftercooler/intercoller would be a good choice and the HP turbo can be sized even smaller for mainly faster response...

(02-15-2014, 01:18 AM)shadowmaker Nope. Actually the big one will spool almost immediately after the small one. Now where did it get that extra exhaust gas velocity to do this?

(02-14-2014, 04:28 PM)F.R.A.S ...Will that big old turbo (the same turbo) still spool at 4000rpm?...

Quote:...So you mean that if I have a big old turbo that start boosting at 4000rpm will spool faster when driven by the remaining gases out of the LP-turbo and the escaping gases out of a wastegate? Does not make sense...

(02-15-2014, 04:37 AM)F.R.A.S Nope what?

We're all friends here and I'm not saying anyone is wrong. But I don't understand. In theory this kind of compound setup would work very bad.

So you mean that if I have a big old turbo that start boosting at 4000rpm will spool faster when driven by the remaining gases out of the LP-turbo and the escaping gases out of a wastegate? Does not make sense...

But I'm thinking about this and I can't find any good solution. Low-tech, high-tech, cheap or expensive... I just can't find the solution.

The best way I can think of is using a supercharger and boost through the compressor of the HP-turbo of your choice. That will give you everything you need. Simple, low-tech and fairly cheap.

But this is about compounding and we have a tough one to crack. Bare in mind that Porsche used compound turbos in the 959 and that's 30years ago.

(02-15-2014, 01:18 AM)shadowmaker Nope. Actually the big one will spool almost immediately after the small one. Now where did it get that extra exhaust gas velocity to do this?

(02-15-2014, 04:05 AM)shadowmaker

(02-15-2014, 03:40 AM)Turbo ...aftercooler/intercoller would be a good choice and the HP turbo can be sized even smaller for mainly faster response...

According to my calculations this intercooler is a bad thing to this current setup, but the team wanted to test it anyway. I've also learned that you can only calculate to a certain point and then you just have to let the real world bring you down...

Compounding is all about getting high boost, wide operating range and low EMP (=exhaust manifold pressure).

With single we needed 100-150m in certain gear to get to the power zone. Now HP lights up after 2-3m and LP around 20m. Smoke is mostly cleared so we must be doing more power than previously even that we are still using similar max boost.

(02-13-2014, 07:27 AM)F.R.A.S I'm a total newbe on compound installations but I have some experience of building fast cars When thinking about this compounding there are some issues that comes to mind.

Exhaust flow and exhaust gas velocity (if that's correct in English).

Normally you build a exhaust manifold the way that you can obtain the highest gas velocity possible (same length primary pipes is not always ideal if one is straight and one is bent 720-degrees). Now to the compound problem. Building a good manifold for a small turbo and then when boosting drive the big turbo via an external wastegate and the small turbos turbine flow... That's shit really!

And building a good exhaust manifold for the big turbo and propelling the small turbo via a wastegate actuator is also bad. Yes you can of course open the wastegate with the vacum pump and close it with boost. But the small turbo are to spool as fast as possible. And propelling that fast spooling turbo via a bad flowing wastegate solution is not really the way to go.

So how do you build a twin exhaust manifold that can get the most out of both turbos? The first problem is cutting of the manifold that is not in use... Solving that problem might be a couple of hours of sketching and some headache. Using the exhaust gas valves from a sports bike might be something, to big though and not 100% seal.

Now to the question. How is this done to be as efficient as possible? How does You guys make this work? And how is the setup made on stock cars like the BMW 123d?

I would love to understand this better.

(02-15-2014, 04:37 AM)F.R.A.S So you mean that if I have a big old turbo that start boosting at 4000rpm will spool faster when driven by the remaining gases out of the LP-turbo and the escaping gases out of a wastegate? Does not make sense...

(02-16-2014, 08:51 AM)Hario I may be being anal here but a 1:1 drive pressure on a turbo compound system with 60psig manifold pressure of course means 60psi in the exhaust manifold, so I'm not sure is that will be 'good' in terms of egt's and exhaust component temperatures..?

Also with regards to reasoning, a typical compound turbo system can be put together for £$3-400 and my shoddy welding skills and I can have 50-60psi at the manifold which I consider to be a massive win in my books!

(02-16-2014, 04:59 AM)erling66 F.R.A.S do you have any photos of the exhaust manifolds you have build? would be very interesting to see since I agree with your thoughts

(02-16-2014, 02:00 PM)F.R.A.S There are some around the forum

(02-16-2014, 04:59 AM)erling66 F.R.A.S do you have any photos of the exhaust manifolds you have build? would be very interesting to see since I agree with your thoughts

(02-16-2014, 02:13 PM)Turbo what about twin entry?

(02-16-2014, 03:00 PM)F.R.A.S We build twin entry also.

This was for a quite fast Audi A3 3.2 DSG quattro. So no diesel I'm afraid

(02-16-2014, 02:13 PM)Turbo what about twin entry?

(02-16-2014, 03:57 PM)Turbo so what are you waiting for we want to see some nice pictures on a twin entry system for a 6 cylinder cars, preferable for a om606.962 in all possible views

(02-16-2014, 05:03 PM)F.R.A.S Ha, ha, I'll post pictures from your manifold as soon as we start building it

Don't have much photos on the computer, but I'll see if I can find something.

You'll get a wheelie instead

(02-16-2014, 03:57 PM)Turbo so what are you waiting for we want to see some nice pictures on a twin entry system for a 6 cylinder cars, preferable for a om606.962 in all possible views