OBehave

Ake,
The company that makes my dyno also makes hub type dynos that use eddy brakes. The company is DynoCom industries and they are based out of Texas. They had hosted the dyno day for one of the OCIC conventions I think it was 2009.

http://www.dynocom.net/catalog/detai...o=113&iType=37

Strosek Ultra

Thank you OBehave. Will have a closer look later, have to run it is late. Over here in Sweden the only hub mounted dynos I have seen are the Rototest and the Dynapack. Think the tuning companies prefer the latter probably depending on the price.
Åke

OBehave

The DynoCom pods are more than half the price as Dynopac and the listed prices on DynoCom website are extremely negotiable. As for tuning,I have the 15000 series with the larger 750 power absorption unit and the tuning capabilities are awesome. Load control by rpm or mph or percentage of load whichever you prefere as well as instant torque display for spark hook test. Very easy to setup and use and so far the consistancy has been spot on. Louie Ott also has a DynoCom and it was after lots of discussion with him when I was getting the Hanson car running I decided to go with DynoCom.
Ed

ptuomov

A quick update: the compressor housings are welded back together. The welding was done fully fixtured, and both the hot side and cold side check out for almost no distortion in the housing inside. Had there been distortion out of spec, slight recutting would have been necessary that would have added to the cost a bit - so good news it's not necessary. There are two machining operations left, one for the turbo speed sensors and another for the compressor inlet depth and potentially the angle. As always, it's about the available real estate. The good news is that the compressed air pipes will now run further away from the exhaust manifold than with the earlier smaller turbos.

If this wouldn't be such an unpopular car, I'd think about casting a bunch of the hot side and cold side housings, but right now hand fabrication is the logical (although time consuming) way to remake the turbos to fit.

ptuomov

Although this is really not that related to my twin turbo car, there was some speculation earlier about John's dyno. In addition to posting a couple of pictures, just for the record, I'd like to clarify a couple of things:
- I don't own any part of the dyno and I was not in any way involved in buying it or financing it. (I think it does make financial sense from John's perspective to own a dyno at his shop, because the number of hours he spends on a dyno per year is high enough. However, that's just my opinion.)
- I expect to pay some for the use of the dyno, but the present value of those payments is likely going to be a trivial fraction of the present value of revenue from dyno. I also expect the cost to me to be lower than when renting dyno time from a third party, for obvious reasons including transport and setup time.

That all said, here are a couple of shots of the dyno units. Of course, what it says on the enclosure doesn't matter much. What does matter is (a) the control system, (b) the data acquisition system, and (c) the underlying retarder units inside these enclosures. But I figured I'll post the photos regardless.

Imo000

Nice but considering how much money you've dropped on this project so far, you ARE directly involved in buying these dynos.

BC

Tuomo -

ptuomov

Although space efficient, those turbos would not fit in 928 and wouldn't flow as much as what we need here.

As a bolt on part for the AMG turbo V8, I think that it looks like a good upgrade. I am guessing that they are taking the factory stock turbo, cutting the compressor housing to hold a larger compressor wheel, and installing a gtX wheel. The hot side is probably stock, except maybe a ported wastegate circuit for wider control range. All of which I like, if that's what they do, because it's a very, very efficient way to make the minimum modifications for a substantial power gain.

BC

http://weistec.com/turboupgradefaq.html

This is a 5.5L engine. They are nearing 1000hp. I am confused as to why you are suggesting the 5L engine we have would need larger turbos to do so. Efficiency is being realized in tuning and also the ability to capture more and more of the actual exhaust energy. If you have reviewed some of the turbo designs coming from F1 (at least the ones we see) it is showing up as having nearly no exhaust manifold at all. Or integral manifolds cast into the heads.

ptuomov

I know what engine they are for. They are currently in the process of making me one in Germany, for a station wagon.

My guess is that those turbos in the photo will not support 1000 rwhp on any displacement engine. If you want 700 rwhp, they are great -- but so were the gt3071r's that came off my 928 motor. 71mm compressor wheel in both of them, by the way.

The reason why I think (but do not know) they will not support 1000 rwhp on any displacement engine is that they will by tuner statement max out at corrected air flow of 53 lb/min, and this is when all the stars are aligned just right, which would maybe support 1000 crank hp, but not 1000 rear wheel hp.

The problem why the compressor maxes out is not "not enough exhaust energy." There will be enough exhaust energy to move mountains as long as more air (and fuel) goes into the engine. The problem is that the compressor wheel blade tip speed gets too close to the local speed of sound. This is the so called" sonic choke." After the compressor hits the sonic choke, driving the shaft with more energy will no longer meaningfully change the mass air flow. All it does is heat the compressed air more, but will not produce more mass flow.

We tested this sonic choke empirically with the gt3071r's. We got to the sonic choke on the compressor map. This is based on on tje MAF signal, manifold pressure, and the turbo speed sensor -- those locate you pretty well on the map. Furthermore, we forced the wastegates shut completely, and the car made about 20 rwhp less than with wastegate operational and asking for a lower pressure. This is because with wastegate operational and asking for lower boost, there was exactly the same intake mass air flow but less exhaust manifold back pressure.

BC

You are getting a W212 Station wagon with an M157 Bi-turbo? An E63 Wagon?

BC

Fair enough. They are working in very close confines as our systems are, and I was suggesting it on the grounds that the manifolds people build in the aftermarket seem to be moving away from what F1 and Manufacturers are doing with Turbo Manifolds.

We always seem to be going down and back. Mercedes is going mid-front and right at the port.

BMW has gone to reversing the heads and sticking the turbos in the V.

The smaller the manifold the more one will wish to isolate the heat of the exhaust from the heads.

ptuomov

I don't care whether they go front or rear. It's just that with a 928, you'd have to get rid of the accessories to go front. Either way, one pipe needs to loop back with an intercooler towards the front. From the performance perspective, front vs. rear is irrelevant. Outboard vs the block valley is not, the bmw's have an edge.

With any turbo exhaust manifold, if the exhaust manifold is hotter than the head then you want to insulate it from the head. If it's cooler than the head, then you don't want to insulate it and instead you want to have the head heat the exhaust manifold.

For a car with street car power band, the shortest exhaust manifold with straight flow paths is the best. By far. Header-like turbo exhaust manifolds are stupid if you are looking for a wide power band for a street motor without any artificial restrictions (like indy/irl manifold pressure rule).

Yes, I've got one of those 2014 e63s wagons on order, but that's off topic for this thread, this forum, and this site.

BC

We may not care, but there is something to be said about where OEMs are placing the turbos. I feel its good to learn from that. I am not talking about where the radiator is when I say "front".



I disagree. People talk about their *other* cars on here all the time. Many Porsche owners, of new and old P-cars, are also M-B owners (of new and old) I am one of those.

The fact that it has a turbo, and the fact that you are buying a 120k AMG wagon speaks to quite a bit, and is information I think is Germain to this thread and the way in which you participate. Its an important set of details.

Will you modify it? Were you aware of Weistec before?

How much more could you merge the hot housings with the manifolds on your 928 project?

ptuomov

Integrating the exhaust manifolds and the turbine housings more would create the following problems. First, there would really only be a benefit if the combined part could be cast together. This however would lock one to only one kind of turbine housing and at these production volumes flexibility is the key. Second, as long as one is using Garrett center housings, there are limits to the angle at which the units can be installed. The angle restriction and the steering staff together pin the turbo location down pretty precisely. Third, installing these things is a big enough jigsaw puzzle as is, and it would only get worse with integrated components.

If John is going to change the kit in a meaningful way, I predict he'll start having some components cast, but still as separate components. But that's pure speculation - I didn't and don't make any of these components you see here, they are all John.

Overall, for anyone outside the ****-nanny states who's interested in 600+ rwhp with high reliability in street driving, what you've seen in this thread until the spring 2013 is _by far_ the most cost effective and convenient way to get your 928 there. What has been done since theb is just a little bit of envelope pushing, in the name of a science project. If you just want to go fast, as fast as you can go with street tires, just stop with what I had in spring 2013 and let the rubber burn.