Joe Ricard

not Tom Cruise. Jack Nicholson

I know I can't handle the power so I will just stay on the porch with my 78.

pappy92651

Hello Rennlisters. I just joined Rennlist.

I've owned my 89 S4 since 2001 and I am still looking for ways to improve performance. The car has many components purchased from Devek and 928 Intl. Both of you are major contributors in a successful project. The car now has GT cams which are indexed for use with a re-programmed auto trans.

This thread is particularly interesting because it is about taking the next big step in HP. Let me qualify a few things; my car is driven on California highways, it passes smog, but it has performance engine components hidden within that are not CARB approved. If I were building a track car I good go nuts. This car has to remain smoggable.

I am not concerned about the cost of building a stealth motor but is has to be reliable. What would be the most reliable approach aside from leaving the engine alone (too late)?

I am also considering a torque converter up-grade. If I get too wild the back end of the car will walk. I have been told that the current stall speed is 1650 RPM. My transaxle gears are 2.54:1 with a 40% LSD. Bigger tires and wheels are an option. I was thinking about raising my stall speed to 2200 RPM. Any opinions on how this might affect drivability or reliability?

I should have purchased a 5 speed version but everything I found was in pretty sad shape. I had to resist the urge to kill the sellers. As it was the S4 also had it's share of bugs but at least the owner cared for the car.

bcdavis

If you want a big step in horsepower, but want it smoggable, go with a stroker.

NOS is an option, but you would have to hide the system.
But emissions would not change, unless you run the system...
Everything works as it did before, except when the gas is on...

A supercharger would be awesome, but it requires a weekend to get on,
and time to tune it, etc... And when it comes time to smog the car, the
supercharger has to come off, unless you want to risk getting caught.
Or you could find a smog place to look the other way.

NOS is a bit of a pain to refill.
And no one wants to be dealing with removing and reinstalling a supercharger every 2 years.
That's quite a bit of work, parts to be saved, re-tuning, etc... Then re-installing, etc...

A stroker is your best power option in CA, but it is also the most expensive option.

But you have to compare cost versus ease of use.
Once a stroker is set up, adjusted, and working properly,
it should not be a problem. A supercharger needs care and
attention to the state of tune. Any problem with a vaccuum
leak, or head gasket problem, and you could have detonation, etc...

A supercharger is good for people who like to work on their cars,
and keep them in tip-top tune...

A stroker is ideal for someone who does not want to do any
extra work on their car after the changes are made...

NOS is actually a pretty inexpensive option.
People just are leery of it, and the hassle of refills is a pain.
But you get to keep the stock power levels, fuel economy,
and reliability, except then you need the extra power.

pappy92651

Hello bcdavis,

Thanks for the reply. The stroker solution seems to make the most sense unless cost is an issue (which it is not for me). Taking the SC off and then putting it back on again sounds like a major pain but the initial cost is low. From past experience I have found that nothing ever goes back together as planned. Something to think about.

Are there any other negative impacts associated with supercharging like, additional heat, relocating components, AC operation, cutting holes?

What I know about NOS is very limited. I don't like the idea of having a gas filled tank in the car with me. If I get into an accident on the freeway this could be very bad. I'm sure the acceleration would be a thrill but short lived. If I were building the car as a dragster this might be an option.

No one has mentioned turbocharging. Room is extremely limited under the 928 bonnet. I would also be concerned about heat build up. Is this a possibility or a dream?

There are many ways to increase performance each presenting their own benefits and challenges.

Thank you for the input.

bcdavis

Supposedly no downsides to the supercharger kits.
Heat stays fairly normal. I think the crankcase breather system is usually updated,
but that would not affect things if you were to go back to stock for smogging...
If you had a mechanical fan, that would get swapped for electric fans.
But that also would not affect anything.
Better injectors, and a rising rate regulator are usually included,
but those would also not really need to be changed if you had
to get smogged. I do not think there are any *serious* permanant
modifications for the supercharger kits.

NOS is only an option for 2 reasons:
1. Cost
2. Reliability
The systems are cheap. Under 1000.
When not on the gas, no extra strain on the engine.

Turbocharging has been done for the 928, but just like the supercharger, if some
savy inspector spotted it, you would be in trouble. And also, there are no turbocharger
kits currently on the market. It has been done, but you would have to foot the bill
for designing and fabricating manifolds, getting the tuning set-up, etc...
I'd only do it if I was building a pretty extreme motor, and lived in another state...
If you are going to spend that kind of money, you might as well build a
"king of the hill" 928 motor... Turbos are not really a cheap and easy way to get
a little "boost" in the power area.

If budget is not a huge concern, I'd build a stroker.
There is a lot of info on these boards about people doing it themselves.
Many different tactics and techniques.
Or if you want someone else to do it, talk to Devek,
since they have a lot of experience with it...

Fastest928

BC,
Well stated!


Marc
DEVEK

Fastest928

You can acheive a minimum of about 400 rwhp with a basic no fuss, no muss smoggable stroker, all the way up to about 450 rwhp/570ish crank stroker with all the goodies.....and still totally streetable and again, a no fuss, no muss daily driver!

Durability and reliability is unmatched at this perfromance level.

Marc
DEVEK

Lagavulin

Yep, I agree too.

Tim's 8psi supercharger kit will get you 435 rwhp for $8,000 and can be installed in a weekend:

https://rennlist.com/forums/showthre...=supercharger/

The 400 rwhp stroker Marc is referring to costs $20,000, and will take two years to get the engine back (..I think that's how long it took Louie to get his engine back from Devek).

If cost is not a concern as you stated, and you wouldn't mind not driving your car for two years, I would definitely go with the stroker, especially since you live in California.

However, IF you would like more horsepower, the supercharger route is much more accomodating in that regard (..but there's the smog police to deal with). As BC stated though, it helps if you like tinkering on your car.

John..

And here I thought plan B would be for "Bastardize".

How about a $10,000 twin turbo kit, intercooled with about 8 lbs of boost on top of the stock S4 motor? Not ideal, but I'd bet it would work exceptionally well.

Turbos: $2000
Manifolds: $2000
Intercoolers $2000
Intake ducting: $1500
Fuel System Mods: $1000
Misc: $1500

Before you all go ranting about how much less power it would make, remember the mid range power would far surpass the centrifugals out there, but would not suck power off the crank like the positive displacement units. What good is 500 RWHP at the redline if you have to shift anyway? Why would I want a Porsche that doesn't easily hook up, but smokes the tires? There is a limit to what you can use on the street anyway (apparently Kibort agrees). My 370 rear wheel with the early gearing pulls super strong and is still enough to run by almost all of the new performance cars out there. I'm at the limit of adhesion of my tires and that is just where it needs to be. Porsche never saw fit to put more than about 450 crank HP on top of any street car. Their cars with 600+crank HP are track cars or cars like the Carrera GT. I suspect it has to do with balance.

I think this has become a contest in who can make the highest dynojet numbers, not about making a good and reliable fast street car. Don't get me wrong, the competition is great, but where the rubber meets the road is in reliable performance. I'd like to see some performance numbers on all the options in street trim. That would be really cool and is really what matters.

Fastest928

Actually, that is what it costs at the lowest level...of course you get a NEW engine, new 8 counterweight crank, new forged rods, new forged pistons, blueprinted to very high tolerences and less than .1gm balance. And with all new gaskets, seals, sensors, hoses, bearings, oil and water lines...basically, you get an engine that has zero time, and will last, with stock maintenance that can be perfromaed by any competent mechanic, for at least 130,000 miles!

Plus it comes smogged, dyno tuned, driven for up to 1000 miles to ensure quality of product and ready for fun!

And you never have to worry about the gas quality blowing up your engine, or running to hot and detonating/melting a piston, or what changes have to be made if you take a trip to death valley ona cool day, etc.

Hey, Superchargers are awesome, if done right. You guys have had some good luck using stock components......except for the head gasket thing...so far, so good...but face it, no formal testing has yet to be perfromed.

Marc
DEVEK

bcdavis

I'd like to see a supercharged 928 with a widebody kit, and huge rubber, and see if it hooks up any better...

How did Tilo's car with the supercharger on it hook up?
Quick Carl?

Is traction still a huge issue, or not?

pappy92651

I want to thank all of you for your responses. I read all of the posts thoroughly and went to the associated sites to get real data. I even found some information on a Devek turbo set-up that was once planned. Rennlist seems to have a very active 928 group and this makes it a pleasure to own the car.

Before I make a decision about performance modifications I calculate return on investment costs. Risk is large part of this equation. Factors such as reliability, emissions, maintenance cost, vehicle handling, fuel economy, oil consumption, and resale value are factors that should be weighed. Nothing is free and hidden costs can sometimes eclipse initial costs. Since a great deal of time has been put into all working approaches I think that it is fair to simulate total cost of ownership. One very important factor is impact of living in a particular region of the world. This is often over looked.

Don't get me wrong, the experiment to increase raw horsepower alone is valuable. The approach that works best is the approach that achieves each of our individual goals (the same reason that we have so many different types of cars).

I'm going to create a business case for a high power street 928 with the following criteria;

Located in California
Driven on the street
Driven in dry weather only
Meets CA emissions test levels
Appearance to be nearly stock
Larger brakes, tires, and wheels possible
>400 RWHP
Runs on 91 Octane pump gas
Can be maintained by local 928 mechanic*
Will achieve higher resale value than stock
Engine MTBF is demonstrated to be greater than 5 years*

*Assumes that vehicle will be driven and maintained under non track racing conditions most of the time, i.e: average maintenance.

Please keep the posts coming. I think that this discussion is valuable to determine the best solution for each of us. I will probably have separate questions for each of you later on.

Thank you

Lagavulin

There is really no need to post any further since a supercharger under the hood will never be considered 'Appearance to be nearly stock'.

I think Jim already covered the 'Will achieve higher resale value than stock too'. Sure you may get a higher resale value out of it, but in the end you'll lose out big-time with a stroker as you'll never recover what you put into it; go back and read the first post.

So throwing the last item out, it becomes an easy choice to go the stroker route.

As long as you can afford $20,000+, and don't mind not having your car to drive for two years, it's a no-brainer based upon your criteria. And I'm sure that you'll be very happy with the results when it's all done too.

pappy92651

Thank you for the recommendation!

Tim Murphy

If I were to do a stroker motor I would buy another motor, cheap, and build the stroker. When the motor is done, how ever long that takes, put it in the car and sell the one that came out. Simple. I often wondered why Devek doesn't just build a stroker motor on the premise that it would get sold and sell it on an exchange basis. Maybe the cost would scare people away? Doubt it, if people want it they will pay for it. If I knew up front how much I was going to sink into my car to get a supercharger working I would have saved myself the time and hastle, sold the 928, bought a Viper GTS and probably been even money. Would I be happier today, nope, today I look forward to the opportunity to spank a Viper GTS. So I guess not knowing up front has its rewards.