Crumpler

I never liked the diverter on the cross bar either. Didn't like the stock cross bar for that matter.
Pardon the black pipe organ, I'm waiting to that until my top end refresh.


Attachment 808543

davek9

I'll start a new Thread.

Short answer of what the Valve is for: the Diverter Valve is connected to the Fuel Tank Vent, and vents fuel vapors back into the Intake.

BIMMERMIKE

Thanks All

LEADASS

To me the single most critical difference is the exhaust. I've got an early '86 and want to do a true dual and it seems I'm SOL. I've got new headers/x pipe and hi-flo cats but I'm kinda stuck from there back. I think I need to go Y pipe to 3" single.

Vilhuer

You can do dual but it has to totally custom setup with two side by side all the way and some small silencers where ever they happen to fit. Friends '81 S street driven track car needs such setup as we want to use headers and X. Not much point in puting X in if right after it is Y.

James-man

Brakes is the most important difference. Exhaust (and aftermarket options) is second.

The third most important difference is that 86.0 owners have to lie on their applications for the supersecret 86.5 club and may not learn the entire handshake.

OTR18WHEELER

my '85 (us) has dual pipes all the way to the rear pumpkin. and duel outlets., has a crossover "H style", but dual pipes throughout outherwise.

PorKen

Unless you have a custom system, the factory S 'twin' pipes are necessarily smaller (and have some squishing at the rear crossmember) to fit down one side of the car.

'True' duals from '86.5-up go down both sides of the car, allowing larger pipes.

Vilhuer

And have single silencer where both pipes go in and mix gases. I think this makes X-over virtually useless or at least moves resulting powerband to totally different rpms.

OTR18WHEELER

thanks for the side by side exhaust pic!, the one on the right is what I have, (of course you know that), but I've seen 928 s4 with a single pipe.
as far as the '85 "duel", wouldn't it be possible to cut out the intermediate muffler and repace with straight pipes, or even glass packs?

PorKen

It's possible, of course, and I've seen it been done, but it doesn't gain anything. The center muffler is a resonator, IE straight through.

Only the 78-86.5 'pumpkin' is what I would call a muffler. The inlet pipes dead end inside, only breathing through holes.

All other 928 exhaust boxes are resonators (including S4-up rear).


Single pipe resonator (dual similar):


S dual inlet rear muffler:

Tim Noce

So just to clarify, you cannot buy a normal X pipe for an 85 or 86.0 but only 86.5 and up? I was thinking about doing this but have an 86.0 not an 86.5

James-man

Correct.

If you were local, I would let you borrow my X-pipe to see for yourself. It has been off my car for several years.

Tim Noce

Thanks for the clarification!

SMTCapeCod

I don't concur that you can't put an x pipe on an '85. the manifold to cats area is all dual-in, the 85 system sweeps off to the side after that. I would think any necessary accomodation would be minor.

Lead@ss- You can get an 86.5 rear muffler, or RMB, and that would give you a dual-in/factory exit. Just need to connec the mids with 86.5 or S4 type, or custom fabricated mids. The floor pan may not be modified, but the stock resonators are thin and I've had no clearance issues, or appearance issues, with such a setup on my '83 Euro.

Editorial-> 300HP...please say no to straight-pipes and/or glasspacks...unless your significantly modified with a stroker or forced induction or nitrous, it's just silly to say you need that last incremental reduction in B/p, and these cars sound lousy with open pipes unless they're spinning over 4K rpm, imho...