Cosmo Kramer

Plugs are NGK BKR6EK. From what I can gather they are the same heat range as the stock Bosch WR7DC. I was thinking of throwing in some Bosch WR5DC.

When I am done I want it to be almost 100% not FAST LOL!

WallyP

"I checked the valve on the ezf and it will let air bleed back through. I took it off and went for another short run to see and it was the same."

If it lets air bleed back thru, what good is it? It won't hold the blower pressure out of the vacuum advance...

Too bad that wasn't the cause of the detonation!

Cosmo Kramer

It doesnt let the boost pressure through but it allows vacuum to the EZF but doesn't hold it.

I know what you were saying and I was a really good thought I actually hadn't thought of it but sadly it wasn't the issue

jeff spahn

So here's a question. Say I want to put a supercharger on my 90 S4. Can't I just set the boost to a limit of 4psi and have plenty of power and forget about the detonation issues without doing upgraded O2 sensor(s). I don't need to spin the tires at 60, I just want about 100 more horses max.

Is this a simple question. I am just beginning to explore the super charger idea and haven't found an answer in the search function.

Imo000

Ted,

NGK copper core (the cheap ones), 2 heat ranges colder than stock, is what you should be looking into. From the pic and it's a bit hard to tell but the right plug, if it's white, it looks lean.
What's the consesus on using the Authority chip for boosting?
I have it in mine (Paxton SC ~6-6.5psi) and it appears to be working fine. My NB O2, at wide open throttle is always (even on the warmest/most humid day) on the border of Stoich. and Rich. Ted's gauge is slightly into the rich but I have a feeling the gauge might be faulty.

It was too cold to have the windows all the way down durign some of the test runs with Ted on Sunday, so I couldn't really listen to the tone of the engine. I can usually tell from the exhaust pitch if the engine is running really lean or really ritch (has a higher or lower overall pitch). It's hard for me to explain but there is a certain tone that a good running engine puts out at WOT.

Imo000

In average each psi is 20-25hp. At only 4psi, the car will be quicker but I'm not sure you'll be happy with what it costs to get there. Might as well go with something a little higher and get a better return on the investment.
Don't worry about lighting them up at 60mph. The only way you'll spin the tires with 8psi is, if you don't have an LSD, the pavements is cold and have very hard tires. And that's what's going on with Ted right now. The car gets squerly very easily because of the summer only tires in a blelow freezing weather. Once the weather warms up the car will be more controlable and less dangerous.

Cosmo Kramer

I have only the Autothority fuel chip in right now, stock EZF chip. If anything the Autothority LH chip will give it more fuel. As far as the gauge goes I am not convinced yet that it is bad. The cycles it makes on closed loop are look very accurate, otherwise it would be swinging into rich when it was oscillating and it is not. Before we tightened the S/C belt and I was only getting it to 5 - 6 psi I had no audible detonation at all. Only started when I crossed over 7 psi at high rpm.

dprantl

NGK BCPR7ES-11 (NGK1095). My car loves them.

http://www.napaautoparts.com/Search/...095_0066627636

Dan
'91 928GT S/C 475hp/460lb.ft

jeff spahn

From what I can see were talking about $11K for a supercharger kit. Not too bad really for an extra 100-125 hp. Perhaps I am misunderstanding the ease of installation of a complete system. What, about 20 hours or so based on what I have read? Doesn't seem too bad. Later if I want more power I can refine things can't I?

I mean where can I get a car that looks this good, comes stock with 300hp for $10K add, $10-$12K and get a 25% hp increase for a total investment of let's call it $25k. Or, I could go buy a Honda Accord, well maybe a Honda Civic.

dprantl

C32 AMG with pulley upgrade... $10k cheaper

Dan
'91 928GT S/C 475hp/460lb.ft

Cosmo Kramer

For those low boost levels the Murf or 928 MS system can get you rolling with one of their stage 1 systems for less then 6 K.

I bought mine used and I have less then 3 K into it but as you can see, not a turnkey system!

jeff spahn

We have a C63 AMG at work that I get to drive around (like Iowa to Florida kind of around). That's a fun car. Would like to get my 928 to that power level eventually, but maybe not all at once.

jeff spahn

Really? I must have totally skipped over that part of the search. I'll look at that right now. Thanks!

hacker-pschorr

As of February 8, 2010 the cost of a Murf928 Kit:

Stage-1 kit - $4995 + actual shipping cost
Stage-3 kit - $7995 + actual shipping cost

The murf928.com web site does not have prices listed at this time, which will be changing shortly.

Z

There's more to it than just the boost pressure. There are internally stock engined 928s that are normally aspirated and have "blown up" due to detonation. Then there are internally stock engined 928s that are still running, and haven't blown up with up to 17psi of boost. The upgraded O2 sensors that have been mentioned are for tuning and keeping an eye on things, and aren't really an absolute requirement if you're adding boost. People were sucessfully tuning boosted engines long before wide band O2 sensors were invented, but you have to know a lot more about what you're doing if you're tuning without one.
I don't know the specifics of the Authority chips, but performance chips for normally aspirated cars often lean out the mixture and increase the timing compared to the stock chips. Probably not what you want.

The narrow band O2 sensors are really more like a rich/lean switch that switches back and forth at an air/fuel ratio of 14.7:1, corresponding to about .5v. As they get further away from that point, their ability to show different air/fuel ratios gets smaller and smaller. Bigger AFR changes result in smaller voltage changes. On top of that, the readings that they give will vary with the temperature of the sensor. That's one reason that the wide band O2 sensors require a controller, rather than just a heater. It's to maintain consistent and accurate sensor temperature and accuracy. Here's a diagram of the typical narrow band O2 sensor's output signal to different air/fuel ratios and temperatures.
http://www.metrotec.de/Regelung/Kennlinie_e.pdf

There are a bunch of different narrow band O2 sensor based air/fuel gauges out there, but most are basically 0-1v meters with a linerar scale. If your narrow band based air/fuel gauge is showing anything less than 90% of full scale while you're at full throttle and under boost, there's a really good chance that you're too lean. The cost of a good wide band air/fuel meter is going to seem really cheap if you're relying on a narrow band one for tuning, and it results in you having a problem due it not being accurate. I haven't looked at prices on any of the wide band air/fuel devices in a while, but the last that I saw, you could get one of the Innovate LC-1 units with the sensor for $150.

If you'd be happy with only the 100hp or so increase that you mentioned earlier, you'd get more than that already with one of the Murf Stage-1 kits. Those are $4,995. They can be installed in a afternoon if somebody's familiar with working on these cars, but a full day or weekend might be more typical for a lot of people. If you wanted more power in the future, you could then upgrade to the Stage-3 kit. It's set up so that you can upgrade from the Stage-1 kit without really having to junk a lot of what you paid for when you bought the Stage-1 kit initially. If you go straight to the Stage-3 kit right from the start, it's $7,995.