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Explored this S2/S4 question last year with ned ritchie... Actually the S2
was not yet a IA option so more specifically, I talked to him at length about
the S4 vs Stock (Extrude Honed) turbos... If I remember the discussion
correctly, we figured that Extrude Honing the S4 might be the hot ticket,
becuz the 258ft/lbs of torque at 1950rpm meant that the smaller S4 was at
full output at that rpm (couldn't get any "better" after that), and that
making the S4 more "flow efficient" with EH, would give you the best of both
worlds, hi output at low rpm and hi output at hi rpm, neither one of us went
further on this, as I went to the EH with the stock turbo and found more
torque and hp... An EH S4 would be a very interesting project, you guys that
have them... I know when I had my stock turbo done last year it was only
50.00 for the impellor and 50.00 for the housing (+ the rebuild kit extra)...
Figured with the existing mods, gave me about 15-20 hp on the stock unit...
Unfortunately, I got the itch to put the S2 in b4 I got a call back from EH
last week... I have lots of experiennce with the EH process and with a FI
car, esp a turbo, there is no downside to the process, well maybe the labor
You are talking about Extrude Honing the turbocharger itself?
Is this just the housing body (inlet side only, I assume), or the impellor
wheel too? Exhaust side?
You gained 15-20hp on this alone? I find that amazing (yea verily, even
hard to believe...) -- is this "seat of the pants", or are there corres-
ponding 0-60 (or whatever) hard numbers to back this up? (Does/did Ned
have any dyno results?)
For $100 (plus ??), this sounds like a true MustDo! Given that, on my
'83 UrQ, a "stock" S4 turbo / Schrick seems to have no trouble maintain-
ing 11psi all the way to rev-limiter territory, would this only be advan-
tageous with Stage-II+ mods? (i.e., at what boost levels does the stock
S4 flow start to drop off [on the high end, say 6500rpm]?). How long did
yours take (what's the turnaround time)?
Drooling in anticipation of yet another way to pump $$ into my $ink . . .