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The Fixer's Avatar
 
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thoughts on supercharging

I am considering supercharging my low mile 1983 928S (US model)

Cat delete, deleted the air pump and the car is in very good tune.

I was only considering a mild charge adding another 30-40 bhp.

Any advice is appreciated.
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Old 09-07-2012, 08:06 PM
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For me, I had 2 issues:

The year of my 928, and cost factor....When I first got my 928, I had seriously thought about installing a SC, (I really wanted to do it!) but, for the $5K or 6K it would cost to do it, I could buy another car. LOL Instead of going the SC route, I bought a complete hi-flow exhaust from 928MS, which made a nice increase in power....Very noticeable gain, too.

And if you add a set of headers (along with the new exhaust) you probably have your 30-40HP total.... And you'll probably have spent less than 2K for everything.

I think if I had a newer model (maybe an S4?) I may have done it...I just couldn't see spending that much on my 1984 model.

Just my 2c, and personal preference, I guess...

Although, a SC is certainly the way to go if you're looking for a serious boost in power!

If memory serves me correctly, I think the Stage 1 SC will give you approximately a 30-40% gain in overall HP. (Maybe 70 - 80 HP gain) or thereabouts...And I think the Stage 2 SC should yield around 80 - 100HP gain...

Not too shabby!!!
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Old 09-07-2012, 09:12 PM
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A little boost can work in an early car, but it won't be enough to get into the range of 85+ or Euro power, and a minor mess up in air fuel ratio and the engine is toast. More than a little boost and you need better brains like 85+ that can be sharktuned.

If you really aren't happy with the power of an 84 the cheapest by far is to buy one with what you want. Next up would be a better motor, Euro, Euro hybrid, or a US 85+.

My own choice is to keep my US 83 stock or at least stock looking, and build a Euro hybrid with a hot cam for my 85 Euro.

*** Euro hybrid is a US 85/86 5.0 short block with a Euro S top end.
Old 09-08-2012, 02:13 AM
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For not a lot more than what the supercharger would cost you by the time it's on the car & sorted, you can get an S4- more power, better brakes etc. Then you have 2 cars.
Old 09-10-2012, 09:02 PM
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This sounds like the other list with guys supercharging their S4's and writing how they "took on Vipers" etc. etc.

The car is now a 33 year old design. Aerodynamically, chassis dynamics, etc. If you want more performance.. why not save and buy a car that starts with the benefits of 30 years of R+D?

Add a cam, free flow exhaust, renew the suspension...
Old 09-11-2012, 04:37 AM
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You can get half that gain by just adding a good Y pipe exhaust. Not sure I would SC a motor without knock sensors. Maybe NOS would be a better route? Euro heads?
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Old 09-11-2012, 06:03 AM
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S4 brains include a good knock sensor, and the brains can be fully tuned via the Sharktuner to use different size injectors etc to make a supercharger work.

Early cars lack all of those features, and have restrictive flow through everything, air meter, intake, throttle, heads, and exhaust. They are a POOR choice for supercharging.
Old 09-11-2012, 12:19 PM
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Thank you for the great advise, new to 928s.

I already removed the cat and the y pipe did add some power.

Trying to lighten it.

Compared to a '86 911 Carrera motor it feels like there is a flat spot in power curve in my '83 US models


I think cams and headers are the way to go.

Thanks
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Options: The delete package
Loud pipes save lives.
Old 09-11-2012, 12:21 PM
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If you live in California, then forget about it. Not sure about other states, but there are no CARB Superchargers for our 928. Thus, it will have to be removed every 2 years for the Smog Inspections here in Cali.
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Old 09-11-2012, 01:34 PM
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Quote:
Originally Posted by The Fixer View Post
Thank you for the great advise, new to 928s.

I already removed the cat and the y pipe did add some power.

Trying to lighten it.

Compared to a '86 911 Carrera motor it feels like there is a flat spot in power curve in my '83 US models


I think cams and headers are the way to go.

Thanks
Where is the flat spot? Range?
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Old 09-11-2012, 03:34 PM
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Many who look for a power boost have never gotten their cars to run at full factory potential, and no matter what direction you go with adding power, getting it running close to perfectly in stock condition is the best way to start.
Old 09-12-2012, 10:32 PM
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stock

Simple answer...NO.

I concur with my esteemed colleague that getting the vehicle to run as well as possible is the best route. So many people look for a quick fix bolt on when the correct path is to fix the underlying problems to begin with. The stock mill delivers plenty of power if running correctly. Simply put...if it isn't fast enough for you, it isn't running well. You might THINK that it is in good tune, but, these things take a lot to get to perfection.

Pull both banks of injectors and send em to Witch hunter, you can replace the fuel lines WYAIT. They also run better on new timing belts.
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Old 09-13-2012, 01:37 PM
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AHHH... Witchhunter for a car that he says runs great? Really? What does Witchhunter do besides run some solvent through the injectors and test them. I guess they rebuild them if they're broke right? You can run B12 chemtool in your fuel and it will break up carbon, varnish, and even in some cases melt rubber. I don't see the need for removing the injectors when you can run solvent through the fuel to perform much of the same effect. Plus if you don't clean your fuel tank, it doesn't really matter anyway because you're going to dump more trash into your injectors.
This goes to show you that too many people on here have too much money to fix s*** that isn't broke. I have too many Porsches to do that.
As for super charging, many will tell you to just upgrade to an S4, but I like the styling of the early 928 much more and pre 85 U.S. cars are non interference engines. So at least you wouldn't have to think about destroying your engine with something as simple as a timing belt on an '83. If I was going to super charge a 928 it would be a 4.7 liter. However, as others have said this isn't cost effective, but neither is 928 ownership in general. Build the car that you want, not what others tell you that you should build for cost effective power output. It makes a hell of a lot more sense than sending your injectors that aren't broke to be "fixed".
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Old 09-13-2012, 03:13 PM
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Thumbs up Busy Painting

I have been so busy prepping and removing parts for painting, i wanted to thank you all for the advice.

My car runs well, when you work on cars as you all seem to, you know. I don't think S.C.ing is the way to go. I want this car to last.

I want to check fuel pressure and do the T.B. first.

Flat spot seems to be after 4500, i think it is simply LH Jetronics..

Love the car, nerve racking painting, i have not painted much in 17 years but it's coming back alright.

Took front facia off yesterday, man this car is so well thought out and the 30 year old facia material is soft and as new.

What a wonderfully made automobile.

I am backdating the front end too, rubber air dam off and in the trash, love the pure look of original design.

The rear wing, wiper and antennae delete body work is un detectable


I will post photos when done.

Thanks
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Built the 1983 928 RS Porsche didn't2690 lbs.w/ full interior
Gulf blue, 5-Speed, 65k original miles
Options: The delete package
Loud pipes save lives.
Old 09-13-2012, 07:09 PM
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Has anyone tried or installed one of the "cheap" super chargers from superchargertuning? They are only $180 and claim a mild 5 psi boost (and that only when at full throttle). There's an installation video on their site, but no dyno info. Thoughts? Insight?
Old 09-14-2012, 06:41 PM
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Mark Kibort on Rennlist has them as a sponsor or something, nobody rational I know thinks they do anything, certainly not even half a psi at high rpm, and they take considerable amps to run.
Old 09-15-2012, 01:10 AM
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Thanks Danglerb. Do you have any info to support this? I'm just curious since they claim 5 psi boost (and @ 20,000 rpm from their motor). They concede that it is only good for short (1-2 minutes) due to electric motor overheating concerns. I just would like to know of any actual experiences.
Old 09-15-2012, 11:19 AM
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You can do a Google search and read all day long on what a scam electric superchargers are.

I've yet to hear of one that doesn't restrict a 4 cylinder engine let alone a V8.

Also amperage isn't free. Ever hear a car with worn belts squeal like a pig when the headlights are turned on? That's how much horse power robbing drag an alternator creates just from lights.

So you have a housing and fan blades restricting air flow along with a cheap Chinese motor drawing a large amount current. I'd say you'd be lucky to lose only 20 HP.

There's a reason most of them are sold to Ritalin fed kids born in the 90s who drive Honda Civics with giant spoilers, fart cans and "intakes"...aka dryer vent hose bought from Lowes.
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Old 09-15-2012, 02:55 PM
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Thanks, maybe that's why they didn't post dyno info.
Old 09-15-2012, 05:34 PM
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i had a similar idea to th electric supercharger, i was thinking of using 2 electric ducted fan engines from a radio controled jet, from what iv read they should move a lot more air than th cheap electric kits iv seen for sale,
Old 09-17-2012, 03:56 AM
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Old 09-17-2012, 03:56 AM
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