View Single Post
spuggy spuggy is offline
Registered User
 
Join Date: Jul 2003
Location: Glorious Pac NW
Posts: 3,416
Quote:
Originally Posted by GroovieGhoulie View Post
I've noticed that the boost gauge stops around .6 Bar on the gauge no matter the RPM, and it seems to run out of "poop" around 5500-6000 RPM, whereas my dad's car will show .8 Bar (as it should), and pulls strong all the way to redline.
Trust me, if you've got a 3DLZ, the power is falling off a cliff after 5100 RPM. Yeh, I know it doesn't feel like it - I'd have bet big money it made power all the way to redline - but dyno charts don't lie...

Even a K27/HF makes peak power at 5700 RPM, with GHL, EVO airbox and a Kokeln.

The only reason to rev them higher is the glorious howl they make. But beware the horrible noise of a spun rod bearing if you have stock rod bolts. There's a reason the manual cites maximum sustained operating speed as 6000 RPM...

Quote:
Both cars are stock and unmolested, so where to start chasing it? Tired wastegate spring opening too early? Something else? Are the tacho-mounted gauges really THAT accurate? Even if not, my "butt dyno" is saying something is up.
First thing I'd say is to find out where you're at.

As others (and yourself) have said, the sensor might be reading low, gauge could be inaccurate, wastegate spring might be tired, boost leak from tired recirculation valve seals, intercooler O rings - or somewhere else entirely. Lots of things to check

If the spring is just tired or lower spec, I'd probably be very tempted to just fit a manual boost controller, dial in the desired boost, set/check ignition and AFR's - then leave it alone and drive the car.

BTW, "stock" boost is often said to be .7 bar - my VDO mech gauge has always read 12.5 PSI (.8 bar) boost, with stock H/Es or GHLs and two different factory wastegates... That said, I've never had it calibrated or checked, so, eh, guess I really don't know what the gauge is reading...

Quote:
And not to open a can of worms, after my research on the 930s, I prefer the Euro cars to the US models!
Yep, agree FWIW.

When I looked to replace the joke (you could roll a baseball through it) muffler I got on the car, I discovered that there are actually 2 factory RoW mufflers:

1) Dual tip outlet, wastegate feeds into muffler (PET says 930 111 037 00 for 930/60)

2) Dual tip outlet, separate wastegate muffler (PET says 930 111 038 02 for 930/66)

I have seen 930 mufflers that look identical to (1) except they have a large, single outlet. I think Borla made one, and probably others.

PET doesn't show a factory one that looks like that. Maybe it's aftermarket?

I run (2) with an open wastegate dump pipe, but I also have one of the earlier type (1) that I bought to gut some of the baffling out of and never quite got around to it. I bought both from different folks off Ebay when I was in the UK. One was $50 + shipping. RoW 930 mufflers tend to be much more spendy in the US.

Just for laughs, I priced up the little stubby wastegate muffler (930 123 063 01) from the Official Porsche Center in Reading. I think they quoted me 1800 GBP (about $3600 US at the time).
__________________
'77 S with '78 930 power and a few other things.
Old 01-15-2009, 10:41 PM
  Pelican Parts Catalog | Tech Articles | Promos & Specials    Reply With Quote #20 (permalink)