Below 1700 RPM I have trouble with my turbo surging as pressure ratios climb outside the stable part of the compressor map at low engine speeds. I have an H1C with a 54m compressor and a 12cm exhaust housing. I am trying to decide how to solve this problem and it looks as though I can buy a 56, 58, or 60 H1C compressor with map width enhancement and put that on my old H1 cartridge, or buy an Hx35 cartridge and basically the same range of compressor wheels . . .

I can't seem to find maps for any of these compressors anywhere, though, so I am totally in the dark as to what to get. I am trying to keep the torque curve up at as low an engine speed as possible. Based on my rough calculations, I think I need a turbo that will support both .07 kg/sec @ a pressure ratio of 1.7 and .34 kg/sec @ a PR of 2.7 -- maybe .39 kg/sec @ 3.04 PR.

If anyone has maps for or practical experience with these combinations -- especially the cheap solution of slapping a new wheel and slotted housing on my H1 -- I would REALLY appreciate advice and suggestions.

Thanks,

Alec

 

Hi Alec,

Forget maps for the most part. A few guys have them and are not gonna show them easily. Those days are gone until you get a connection.

Your impeller is not the greatest for a wastegated housing. I can only find two wheels from Holset that should work better with a wastegate for the H1C. 3545437 and 3545436.

Like you said the 35 with the slotted housing is probably going to help your surge as well.

35's are cheap, durable and my favorite turbo from Holset for all around "works great" The newest wheel in the HX35W is the best little wheel I have seen in that flow range of nearly all the turbos out there.

Don~

 

OK, here's a question. WHY don't those who have the efficiency maps want to let anyone else know about them? What's the big deal? I'd think that would be a normal research area when shopping for a turbo. Not that I'd actually know how to read it, but still.....


Thanks,
Chris

 

Its always easier to say you have a very efficient turbo and never have to prove it. Many OEM's dont want the info available. Holset supplies to a ton of OEM's. I think they feel the less you know, the better.
Garrett is great for supplying maps, so is Mitsu, but the OEM style turbos are the hardest to get maps on.
Aftermarket turbos are the easiest, of course.

Wheels now are generated from a model and many impellers just dont have maps. No need to flow test a map design that is generated from a model where the code is validated already.

Don~

 

Thanks Don --

Just to make sure I understand you, however: You would recommend that I get an Hx35 with the smallest impeller available (I think that is 56mm) and the slotted "map width enhanced" compressor housing?

That makes sense to me as best I can figure the surge comes from pressure in the compressor housing being greater than the centripital force required to keep the air from flowing out of the impeller at the given turbine speed which would imply that I need to keep the turbine speed up at lower volumes to support the pressures I am looking for?

Also, can you explain a little about how the MWE slots actually work?

Thanks,

Alec

 

Yeah, the slots are to slow recirculation at low rotor speeds.
You nailed it Alec.

Surge is a loss of grip on the air. A tractive loss.

Yes the 55.8mm or the 56. Same, same.

Don~