Still no Real Boost Until 4K - Did I Buy The Wrong Turbo?
 

After I finally took the 930 (1980) plunge last fall I began compiling parts, as the stock turbo was tired and I wanted a bit more performance than stock. Unfortunately, I started buying things when I knew even less about the world of boosted cars than I know now - which is still precious little.

The K27 seemed (and seems) a very popular upgrade to the 3LDZ and, from what I've read anyway, should, in combination with the RarlyL8 headers and Borla muffler I installed at the same time, bring boost on noticeably earlier than the 4K that seems typical with the 3LDZ and stock euro exhaust I replaced.

It doesn't.

Anyway, I took snapped a shot of the riveted-on turbo tag to try to figure out exactly what I have (now that I've done more of what I should've before starting to buy parts ... read) and although it's a K27, I'm not seeing anything like the 7200 or 7006 that seems to normally appear on the tag.

Can anyone tell me what I have and whether I should be seeing the improved onset of boost I'd hoped for/expected?

edit: Sorry, the image came through much smaller than expected. Here's what the numbers say:

K27-3070 G 1311
82 829 0501
5327 999 0248

http://i50.photobucket.com/albums/f3...psb270114c.jpg

do you have a wide band gauge in the car? you may need to do some fuel and timing adjustments

oh, and most important question... which gear are you in when you make note of when the boost comes in?

Yes on the wide-band. I'll try to double check the timing soon. Do these cars like stock timing with upgrades? Other cars I've owned & built prefer a fair amount more advance (both initial and total) once they're very far removed from stock.

1st and 2nd both come on hard right about 4K, don't recall third but seems like it's about the same. Have yet to reach boost in 4th ...

The inducer or intake side of the compressor wheels looks similar on the 7200 and 7006 even though it isn't, but the hot side turbine wheel exducer looks different and is larger diameter on the 7006.
The entire turbine housing of the 7006 is bigger than the 7200 so pictures of both sides of the entire turbo would help figure out what you have.

There are also alot of different k27 hybrids around to confuse things even more. Some like the HFS have large Holset compressor wheels and some have the large K29 compressor wheel. There may be others too.

They respond alot better with advanced timing at idle and midrange rpms until boost happens and then it has to be pulled back close to stock timing under boost depending on the fuel octane you're using and how much boost you're running, enough to keep from killing pistons and rings with detonation.

Advancing the timing is risky though so don't experiment with it too much advanced unless you know what you're doing or running plenty of methanol injection if you're running low octane crappy E10 fuel. E10 octane levels are somewhat regional so that has to be considered too.

Todays lousy E10 fuel starts going bad in a month and if it's humid out the ethanol absorbs water right out of the air and the water combines with the ethanol and it sinks to the bottom of the tank and stays there rusting the bottom of the tank.
Thats called phase seperation and the E10 gasoline octane lowers as the ethanol and water mix, seperate from the gasoline, and collects in blobs on the bottom of the steel tank.

Todays E10 and soon to be E15 gasoline is lousy. Adding fuel stabilizer with no alcohol in it helps in old cars with mechanical injection or carburaters made for real gasoline.

Sorry to hear of your problems.

Eh?

My almost-stock 930/60 with a 3DLZ and RoW headers would be all-in (12.5 PSI) by 3300 RPM in 2nd (915), if it had load (throttle). 3000 RPM in 3rd or above.

You could even make boost in 1st with a 915. Usually unintentionally, in my case. Not nearly as much fun as it sounds... That might have been 4000RPM - little hard to tell/over too quickly/too darned busy to look at the gauges...

Are you going by the sound of the wastegate opening, or the stock gauge in the tach?

Sounds like you may have a boost leak.

930's love advance. They also love cams that have decent overlap/lift. SC cams are popular for much improved low and mid-range. Some use 964 cams, but these give up more at bottom end (which you can make back with EFI, just by having accurate fuel/spark control). Apparently, SC, 3.2 and 993TT cams are almost identical profiles (except for the quietening ramps on the 993TT, for the hydraulic tappets).

You should be careful with too much advance, although it significantly improves off-boost throttle response even on stock cars (930 static timing is very conservative). I personally have had excellent results with the J&S Safeguard, which provides adaptive per-cylinder knock control and programmable boost retard (which I use to bleed off my extra static timing under boost). Some seem to think knock control is voodoo - but the factory fitted a knock controller to the 1986 951, and every new motor they developed after that.

One of the most nightmarish threads I've read on this forum has some very nasty photos of damage to a motor fitted with methanol injection. There's nothing wrong with the theory - "latent heat" isn't a suggestion, it's a law of physics, and others have used it with success - but clearly things can go wrong translating that into practice.

Your mileage, as they say, may vary. Lot of great information here.

My money is on different "species" K27. Do you recall the description of the turbo when you bought it - like what the seller said it was off of?

That is NOT a 7200 or even a 7006; my guess is a large track-oriented turbo.

That does not show up on any of my lists. Maybe the numbers are wrong? Anyway, the 999 means it is a replacement compressor cover, and the 1311 means it has a 13cm2 turbine housing, or at least it came with one originally. Did you notice any number cast into the housing on the inside passage, where the exhaust comes in. A 13 is pretty big. A real 5327-988-7200 has an 11cm2 turbine housing, and 3072G compressor.

This is one of those times when I wish I'd left a little less of my short-term memory in the seventies!

I remember the seller telling me that it was set up to spool faster than the 3LDZ, but of course that could mean 3990 vs 4000 RPM. Unfortunately, I nuked all of our PM exchanges so I can't look back for info. And, of course, I can't remember his user name and can't find the original FS post where I found this turbo.

Drat!

Had you continued your sentence a bit farther, Brian, might you ave concluded by saying " ... and not suitable for a lightly modded, street-driven 930"?

'Cause that would just figure.

Doesn't show up on any of your lists. Perfect!

I did not check the inside passage for casting nos.

This may help:

http://forums.pelicanparts.com/911-930-turbo-super-charging-forum/586759-original-935-k27-turbo-value-info-wanted.html

Well, whattaya know!

Perhaps this ... "I removed mine from the car last weekend, It was not well suited for a stock car..." would've been useful information to provide to a prospective buyer when offering it for sale.

Caveat emptor, as they say ... or C'est la Vie. I guess it's just money.

So, anyone in need of such a turbo? Anyone have a good street use turbo available?

I have a brand new K27-7200 with headers, muffler and intake. I get to 1.0bar in 4th at 2300rpm. :-)

The compressor is probably OK and you may be able to find the proper (smaller)turbine housing.

Really?! That might be a new record.

pics or it didn't happen