KD93

What do you all think about using a 21cm H1C as the low pressure turbo. I was thinking of something like an HX35 or HE351CW as the top. Yeah, I know an HT3B is what everyone wants, but not all of us can afford it! And I'm not looking for huge gains, just something mild that'll keep my egt's reasonable, and give me a bit more boost. Ideas/thoughts?

schamran

I was thinking about giving my lagmaster 21cm turbo to my buddy to put as a secondary on his 4 bt. I don't know how well it would work. If It would help my setup out, i would pair it with my hx35.

dzl_damon

I think the biggest thing you are looking for on the bottom turbo is in the compressor, not the turbine, correct? I think you're going a wide map with large air flow, I don't think the pressure aspect matters as much on your primary. I could be off though, and my nomenclature may be wrong as well!!

gman07

To put it simply, it won't work. The compressors are similarly sized, so the bottom turbo won't build any boost. Pressure is the result of restriction of flow, and with two identical compressors there won't be a restriction for the primary compressor to "push against" so to speak.

dzl_damon

very nice explaination gman. Makes lots of sense to me, and makes me see where the nomenclature is derived from more.

schamran

Ok, now how about on a VE powered 4bt? I don't know what they run for a stock turbo? but I am pretty sure it is smaller than an hx-35.

dzl_damon

hx 30 I think was one option...

KD93

Ahh, I see!!! When I asked the question this was kind of niggling in the back of my mind, but wasn't sure. Thanks gman!

So, the next question is, what sort of sized compressor wheel do we want as a secondary? I don't know what the dimensions of an S400 or HT3B are. Any ideas? Ballpark I'm talking, 'cause it really depends on how much boost I want to be making, right?

gman07

I think the H1C is even a little too small for a 4BT primary. An HX40 might work for a mild set of twins though.

I think most of the primary compressors used in twins are in the 70-75 mm range.

KD93

Great, that gives me a figure to work with. Thanks gman07!!

pwrtripls1

You can get am MP70 turbo for about $600. Its a 70mm and good up to about 25psi, which is just fine when you add the high pressure turbos 30psi. So you'll have around 55psi. Only reasone I know about those cheap turbos is I have a 4.3L v6 Blazer that makes a good 15psi with one. It spools slow on the little motor, but thats what N2O is for.