v01canic

iTrader: (1)

hey!!! thats the turbo i have, its a TB2522 nice to know someone on here has messed with it.

falcon

iTrader: (13)

The GT22 looks like it would actually do the job fairly well VS. the GT2554R.

I basically need a turbo that will make 10PSI as fast as possible without choking on the compressor side at 300+whp. I'm thinking a hybrid small turbine/large compressor is really the only answer. Since most of the exhaust gasses would be bypassing the turbine in the upper RPMs through a giant wastegate... a small turbine may not be a bad idea.

Any ideas?

Then there is the smaller GT2560R which seems to have a decent efficiency towards the right of the map.

I don't think I would be going over a 2.5PR ratio anyhow. The PR on the turbo will lower significantly at higher RPM with the blower pulling air through the compressor.

JasonC SBB

Dood the smallest fastest turbo for 300 hp is the GT2860RS with 0.48 hotside.

falcon

iTrader: (13)

That's not what I'm asking, but thanks anyways.



Looks like this guy is the only other person I can find who has twin charged a car with a Rotrex. However he is doing it different and has the Rotrex feeding a huge turbo.

falcon

iTrader: (13)

http://www.mr2forum.org/forum/index....-rotrex-power/

http://www.youtube.com/watch?v=96QbY...mbedded#t=106s

dstn2bdoa

iTrader: (18)

I know this may be missing the whole point, of compounding the two. But would this work?

Normal Rotrex setup and mount. A turbo tim bottom mount type set up. Both flowing into a collector with a flapper valve. At lower rpm the little turbo is spooled up and pushing more air than the rotrex, as the rotrex comes into it's prime it pushes the flapper valve down closing or mostly closing the turbo side of the collector. This then flows into the IC with the map sensor post IC.

Would this work?

Crappy paint drawing



If this is hyperish, flame away.

falcon

iTrader: (13)

I don't like that idea because you're basically throwing away boost. My idea is to make the most boost as fast as possible, without taxing either compressor at all. That will only work if you compound

Rara

falcon,

unfortunately, the way you're considering this has a bunch of practical roadblocks to making it work well. The most significant probably is you will have to bypass the turbo compressor at some point, as the amount of flow will completely choke it once you have the rotrex really going. At that point you will lose a lot of boost anyway because of the effective restriction through the turbo compressor and likely the excessive temp rise because you'll fall off the cliff on comp efficiency. Not to mention a good chance you'll be overspeeding the compressor wheel causing damage to it and probably the bearing.
Which aspect is likely to be worse would depend mostly on how you try to calibrate it. If you don't wastegate enough flow, overspeed and temp will be the main issues, along with high turbine inlet pressures, and if you do wastegate the flow enough so you don't overspeed the compressor, you will just choke the rotrex.
The only way it will function reasonably well sticking with the plan you describe, is to completely bypass the turbo on both ends once the rotrex is making good boost. Depending on the comp map for it, you might be able to re-pulley the rotrex for the higher boost and use the turbo to compensate for the soggy bottom end. Something very small would be best I think, in the GT15 range. One of the OEM turbos off the Ford 3.5L would probably be a good choice if you can find one cheap, they are GT1549.

njn63

iTrader: (4)

That article is pretty stupid in regards to what they're saying about F1 cars because they don't allow F1 cars to be timed at Goodwood anymore. Nick Heidfeld's 1999 record still stands at 41.6 with the MP4-13 as the fastest ever up the hill (officially). A modern F1 car would go much quicker than 48.07.

chicksdigmiatas

iTrader: (11)

Exactly like my first car, but mine had pop up headlights. Plus the turbo was a wee bit smaller..

falcon

iTrader: (13)

I am going to hook up a boost gauge to the rotrex intake and log how much vaccum it pulls through the whole rev range. I should be able to match a compressor on a turbo that will allow it to flow that much at a low 1.3-1.5 PR.

turbotyla

iTrader: (2)

why not just tune the rotrex for low and the turbo to take over when the rotrex runs out of steam

falcon

iTrader: (13)

Because if I gear it any lower it would be massivley overspinning it in the high RPM.

nitrodann

To prevent the turbo compressor from choking out the rotrex, how about a big *** one way valve between the two? this way the rotrex can pull from that air and not necessarily from the turbo?

Dann

Full_Tilt_Boogie

iTrader: (1)

I cant tell if you guys are joking or not...

falcon

iTrader: (13)

joking about what? twin charging? It's been done before with a Rotrex.

I think the best way to do it is like a compound turbo set up where the big turbo (in this case the rotrex) feeds the small turbo's inlet. Then when the big turbo (rotrex) takes over it blows through the little turbo. That's how must compound turbo set ups are made.

sixshooter

iTrader: (12)

I see two misconceptions in the arguments against this setup. The first is that the small turbo will be out of its efficiency range due to high pressure after the Rotrex starts moving air. The thing to remember about the compressor maps is that it is a pressure ratio and not an absolute pressure being portrayed on the maps. If you add, say, one BAR of pressure to the inlet of the turbo compressor, that will be 1 PR on your compressor map and not 2 PR as a starting point.

The second is that some of you are confusing mass of air on the compressor map with volume. When the Rotrex is making positive pressure the mass of pre-compressed air entering the turbo will be far greater than the mass if it was simply atmospheric air entering the turbo. I'm no engineer, but I believe this will effect the mass calculations when reading the compressor map as well. You are essentially moving the base calculations for atmospheric conditions of pressure and mass of air by changing the pressure and mass of the air by volume that enters the compressor inlet. The compressor "sees" different atmospheric conditions than ambient.

Have you ever seen a shop air compressor with a multi-cylinder compound design that uses a very large piston feeding a smaller one and then going to the tank? The smaller one is not choking the larger one's ability to feed the tank. The large volume entering the big cylinder is a much smaller volume when leaving it and can easily fit into the smaller cylinder to be compressed even further. This idea is nothing new.

falcon

iTrader: (13)

Thats what I was originally thinking...

vehicular

iTrader: (3)

After thinking about it for a while, I think you're on the right track, except that falcon keeps mentioning blowing the turbo into the Rotrex, making the small turbo compressor inlet the choke point in the system. If You were to blow from the Rotrex into the turbo, then you would get exactly the sort of system you want. Just like in the case of compound turbos, the small turbo will pull air through the restriction of the Rotrex compressor (less efficiently than it would from open atmosphere, but not too badly, as the Rotrex will be moving SOME air at low rpm, if not enough to force feed the turbo) until the blower spins up to an rpm where it can add to the mass flow rate, and multiplicative pressure ratios will begin to take over. You wouldn't have to use any sort of silly check valves/ bypass nonsense, or any boost control other than a well designed Hytech style wastegate biased exhaust manifold and a big gate. You'd also get most of the advantages of the compound turbos, without the complicated exhaust routing, multiple wastegates, complex boost control strategies, or most of the packaging tom foolery...

vehicular

iTrader: (3)

The question I can't answer for certain is what will happen when you try to move 33ish lbs/ min through that GT2252 compressor, even at a really low pressure ratio. That's still a ways right of the choke line.