Jim_H

Carl, hotter plugs? This is a new one on me but I don't make the rules, just kinda folllow them... when they are handy Please explain.

Oil analysis, great one.

Hack, If you start out with clean underwear it can be a dead give away after the ride of the umm joy you had.

Topdown +/- 1

Carl Fausett

Hotter only means the center elctrode is a little deeper up tinto the spark plug housing, so it retains a little more heat to burn off oil deposits.

If detonation was a problem you may be forced to go to a cooler plug as to avoid a hot-spot in the combustion chamber that may ignite the air-fuel mix sooner than you want (detontation).

But, on our 16v kits the engine is usually a lower comp motor (8.5:1) and we are not very detonation-sensitive, plus the early motors throw a lot of oil around. The little hotter plug stays cleaner.

Thaddeus

All good insights, and actually far less than I expected.

Can supercharging be done to a car with an automatic transmission? It's what I have... run what you brung, as they say...

Bill51sdr

Just ask Bill Ball

Thaddeus

Bill's is an automatic? Cooooooooooooool.

hacker-pschorr

One of Tim's supercharged 928's is an auto.

Tim Murphy

The AT cars do very well with boost. There are a lot of the AT cars that have the kick down cables out of adjustment causing early shifts (takes a lot of the fun out of it) and also many have a broken or leaking vacuum line to the trans.

You want to verify that the full throttle switch is working properly. This is a big factor in how the LH fuels the car at WOT. The 85-86 cars also have a vacuum line that goes to the LH which determines the load on the engine. Make sure that it is functioning properly. I do not know what boost in this line will do to the LH on the 85-86 cars so you might want to ask some of the guys that have sc'd these cars for what they did. I would guess that the boost in that line would be okay to do.

Even though this may be obvious; make sure the entire vacuum system is operating properly on the car before boosting.

A known good MAF is very important (I suggest sending it to john Speak for recalibrating). I have had some customers where the car runs perfect without the SC but when they get into the upper boost range (higher MAF voltage) the power would fall way off. A new or rebuilt MAF has fixed this every time.

Once you have the car boosted, monitoring fuel pressure will tell you if you have a weak/strong fuel pump. If the fuel pressure falls off at higher rpm you know you are running out of fuel thus running lean. If you plan to replace the fuel pump go with the Bosch -044 pump. Any 928 vendor can get that for you (don't call me for that because that's not what I do).

I'm sure I will think of more but I hope this helps for now.

Good luck!!

Rick Carter

[QUOTE=Tim Murphy] The 85-86 cars also have a vacuum line that goes to the LH which determines the load on the engine. Make sure that it is functioning properly. I do not know what boost in this line will do to the LH on the 85-86 cars so you might want to ask some of the guys that have sc'd these cars for what they did. I would guess that the boost in that line would be okay to do.
QUOTE]

Based on my limited experience, boost (or maybe lack of vacuum) in the 85/86 LH vacuum line may retard timing.

Bill Ball

Yessirreee. In fact, I think the AT is great for a for SC or turbo application as there can be less fall in RPM during shifting since you keep your foot in the pedal unlike a MT car. Also, although I can't in any way verify this, the AT is regarded as more durable for high HP applications. I'm not sure that statement included the torque converter. Some concerns have been raised about frying the TC with all the low end torque the Eaton and twinscrew blowers provide, but I don't fry the TC for much more than a block at a time before I give it a rest. So far, so good. I've had my SC in for a week short of a year and about 15,000 miles. It's been tested at sustained high speed at desert temperatures and everyday driving and I have yet to even adjust the SC belt.

I may have been flippant in my earlier response, but frankly, that's what I did. I had some oddball idle issues after the install, and subsequent to that I did all the things people mentioned (compression check, new plugs, new plug wires) none of which made any difference and ultimately I found that the way the bypass valve vacuum was routed was the problem, not my car. I had about 145K miles on the car when I did the install and it was mechanically sound, although I did none of the pre-checks others have suggested. Would seem prudent, however. Pre dyno is a good idea.

bd0nalds0n

Check out the different kinds of superchargers. Each has plusses and minuses. There seems to be a bit of a gravitation to one particular style vs. another depending on whether its going on a 5sp or an AT, although this is a generalization rather than a hard and fast rule. I know of centrifugals on ATs and TS/Roots on 5speeds...but I think there are more examples where the reverse is true. Not my intention to open a can of worms or slight or favor one over the other....

Thaddeus

My MAF was brand new last year and my vacuum hoses are all good, AFAIK. The engine runs very well... not perfect by any means, has character, shows some wear, been around the block a few times, but very solid. Kind of like its owner.

My mind is nearly made up.

Bill Ball

Thad:

My engine did run perfect, so make sure none of these rough edges you have are significant. Compression and leakdown, tune up (plugs, cap wires, if not recent), any defered maintenance. BTW, Tony's twinscrew is an AT and George Suennen's Murph (which I helped install) is an AT. So, go for it.

Carl Fausett

The automatic transmission in the 928 was made for Porsche by Mercedes Benz and mounted into a Porsche case. It is the MB P8 trans (if I remember correctly) and is good to 650 HP. The automatics are doing very well supercharged, I'd say about 1/3 of our 16v and 32v installs are automatics.

The CW on the manual transmission is that it is good to 550 HP, but we know folks like Jim Page, Mark Anderson, and others who are driving it above that.

MarkRobinson

Replace the rubber fuel lines at the motor: all 3: supply to the damper, damper to the pass. fuel rail, and the "u" line between the damper & the regulator.

Re-vacuum line the engine with "good stuff", figure out your breather situation before adding a blower/turbo, ensure vacuum is strong, MAF is good, regulator is good or is replaced, and a recent fuel filter is not a bad idea either.

All factory-turbocharged cars come with colder heat-range spark plugs. I see no reason why you wouldn't want that extra protection. For medium-low boost, I like the BKR6EK (what I run in my 911 turbo & the NGK recommended plug for the '94 3.6 turbo 911's) or the BKR7E spark plugs for higher boost (what I run in the turbo 928). I've noticed no driveability issues or cleanliness issues with the colder plugs.

Cameron

I think that the AT cars would be a great Supercharger candidate. I loved my '90 S4 but the two complaints were the lack of initial jump off the line and the chasm between 2nd and 3rd gear where the RPMs would drop a bit too much and it would fall out of the sweet spot of the power curve. Both of these issues would be addressed by a blower, and with all of that torque, the auto would be a pleasure to drive daily in all traffic situations.