993RS

Often one forgets that specific performance modifications can not be considered singly, but need do be done in conjunction with other modifications.

For example: Chip tuning should be combined with additional modifications to improve the breathing capabilities (sport mufflers, sport cats, etc) of the engine to achieve any appreciable gains.

This means you can not singly add up the mods: sport mufflers results in x-hp more, chip tuning results in y-hp more, resuling in z-hp. Chip tuning without the sport muffler will not result in so much an hp gain.

One of the biggest barriers to increasing hp on a 993 engine is the restrictive exhaust system. Making it less restrictive means increasing noise and air pollution.

Martin S.

You wrote, "One of the biggest barriers to increasing hp on a 993 engine is the restrictive exhaust system. Making it less restrictive means increasing noise and air pollution."

Ypur hypothesis could be readily checked on a dyno...run the stock set up and note the torque and HP. Next, take off the cats and the muffler, crank it up and see what you get. You may have a little trouble since the Oxygen sensors would be disconnected. I am curioius if this has been done, but not that curious to do the experiment myself. Allow me to digress.

Assuming we all have to live with state imposed noise restrictions, I see your point. However, have you ever heard a 993 running without catalytic converters, would it be significantly louder? If it wouldn't be that much louder, then the cats are not the source of excess noise, howver they may be inducing a restriction that is affecting HP. We need the experiment performed to find out.

I have Robin Sun's RSR mufflers...they seem to flow freely...perhaps they are not contributing
to any significant loss in HP. We know it can't be the headers, because 993 headers are about as good as they get...I have read that the 993 headers are near perfect, and as potential evidence, we see very few aftermarket headers for 993 cars...not true with the 996. Also, in most cases as with earliest 911 cars, headers on a 993 will cuase one to lose their cabin heat.

Also note, if there were HP to be gained out of the header system, don't you think the 993RS CS would have different headers than a 993? I say RS CS because this was the track orientated car according to the 993RS spec manual I have been reading.

I do agree that the biggest HP increases will come about a a result of a systems approach....this is based upon my reading: I don't claim to be an expert, but just how much N/A power is there for the taking? Not much I submit.

Im my humble opinion, perhaps the root cause of the difficulty of readily finding extra HP from a 993 motor is not the "restrictive exhaust system". The 993 motor may have just about been maxed out in terms of the technology present on the engine, specifically, only 2 valves per cylinder, normally aspirated, fixed valve timing, cams that must produce good mileage and allow the engine to run clean, a physical displacement limit of about 3.8 liters, and air cooling. Perhaps OBD II is also a bit of a culprit, AND the fact that most of us are in a position where our 993 cars have to pass emissions tests.

I have 282 HP in my little 97 coupe, enough to get me to 170 mph, so the spec sheet says. I will invest my money in the suspension and the aerodynamics, example, the 993RS aero kit. After I max out the handling of the car and I have taken it to its limits (This will never happen!), then I'll worry about adding extra HP, much cheaper yet, sheding weight.

By the length of this post you can see that wifey is out of town and I have absolutely nothing to do, pardon the rant! And thanks to Philip (993RS) for stimulating me to post. His posts are always well crafted and interesting <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" />

993RS

Martin,
Discussing hp increase with Bill in another thread, it seems that we have a pretty similar engine, yet he gets about 15 hp more, and I suspect it is due to exhaust system which is geared to racing.

Macca

Hi,

I too have the RSRs. Im running Steves Chip and a Powerflow cone. I have a 272 hp unit OBD1 and run on 98 RON (NZ - probably 93-5 RON US). My car is ROW with the according ride height/suspension and gearing.

I don not have 1000s to spend on this car. I love it bits, but you never know when something like a 993TT may come into your life......hence I cannot justify overspending on this vehicle.

I like the pure 993 form so no kits for me. I even find the 17" Cup rims visually acceptable, light and at 205 front/ 265 rear they give excellent feedback on the track.

The last modification Im looking to justify are CAT bypass pipes. I know these will be louder (how much?), and I believe they will free up brathing and increase power a little in combination with the other mods. I think the hp difference will be small but mid range torque may further improve.

Before I buy and dyno these mods working together I was wondering if anyone here has run the cat bypass pipes?

Cheers

Macca the kiwi

993RS

What can be done to make the N/A 993 develop more power?

1. increase displacement - larger cylinders
2. increase compression ratio (not so easy without other mods I guess...)
3. let air come in more easily (larger intake, special air filters, polished intake system)
4. let exhaust go out more easily (sport cat, sport muffler)
5. make engine parts lighter (titanium, etc.)
6. chip tuning

Did I forget anything?

Robert Linton

Ladies and Gentlemen:

Without getting into a very long discussion, in looking for gains from a 993/964 engine, one might look more to induction than exhaust -- and by induction, I do not mean the bigger, better air filter system. Also, for significant improvement one must compromise certain things such as driveability (e.g., different camshafts). Remember that Porsche obtained in excess of 400 HP from sprint (as opposed to long distance) versions of 993/964 engine -- and this was without Variowhatever! However, should you be interested in obtaining this type of horsepower (together with approximately 380 nm to 400 nm of torque), certain things must immediately and permanently go:

1. your A/C;

2. your street driveability;

3. your compliance with regulations;

4. $40,000 to $60,000 from your bank account.

In other words, if you are this serious about racing, you should buy a Cup Car with a proper welded in roll cage, fire supression system, etc., etc. -- and this would be far better, far safer and less expensive than some of the packages of mods put into street cars.

E. J. - 993 Alumni

Robert,

Doesn't a cup car only make 315 hp?

E. J.

Jim Richards

Neophyte question(s) - Is reducing weight a more viable option than increasing power? Can this be done without sacrificing too much for street driving (with wifey)?

Regards,

Jim
1995 Black 993 Coupe

Robert Linton

E.J.:

Published figure for a Type 996 Cup Car is 380 BHP at 7000 RPM -- without further modificaton (which could increase HP over 400). But this is only part of the story, i.e., weight of approximately 2580 pounds, better aerodynamics, better balance, better braking, etc., etc., etc. -- it is a different world.

Bob

Robert Linton

Jim:

Certainly reducing weight as opposed to putting in a real race engine would be better for comfort -- and, if done properly, could increase suspension and braking performance not simply because of the weight but also through technical improvements. On the other hand, meaningful reduction, i.e., 200 pounds or more, is not inexpensive either -- one would have to look carefully at your car to determine how much weight for how much money.

Bob

993RS

Paul Frere in his book writes that "...the Porsche RSR 3.8, the unrestricted engine of which develops approximately 375 PS. With the 48mm intake air restrictor required by the 1993 Le Mans regulation, the power drops to 360 PS. Withe the 45.3 mm restrictor required in 1994, this drops to 355 PS, and with the 39 mm restrictor imposed for races under FIA regulations, only 315 PS is left..."

Hank Cohn

Great discussion guys.

The stock headers are far from perfect on the 993 as they are net even equal length headers. Packaging and the need for cabin heating preclude the “perfect” header. I have run my car with open headers, no cats or mufflers and it is incredibly loud. You could even call it painful. Porsche can get 410-420 HP out of a sprint engine, Robert, but the power band is very narrow, would not be even close to livable on the street and while it doesn’t use Varioram, it does use slide valve induction, which I can tell you from experience is kind of like a light switch in that it is either on or off.

Weight reduction is an excellent approach to improved performance, but the cost of weight reduction can’t be safety if you are driving the car on the street. There just isn’t that much that can be taken off of a street 993. If you have a dedicated race car, then 2600 lbs is easily obtainable with a cage included. I know that lower weight is possible by substituting some very expensive and exotic materials for body work and other structural pieces.

There are several things you could do to your stock 3.6 to get more power out of it. In fact they have all been mentioned in this thread: Cams, induction, headers/exhaust, chips, compression, increased RPMs (with proper rods, bolts, etc.) and displacement. It’s just not inexpensive. It probably won’t pass an emissions test and it probably will be less drivable on the street. I think guys like Greg and Bill have the right idea. Get a dedicated track car and you can experiment until your heat is content or your wallet is empty. Don’t get me wrong, modifying a street car is a ton of fun and I am just as guilty as the next guy, but if you go to far you’ll never get any money out of the car and finding someone to buy it when you’re done will be a real challenge.

Robert Linton

Last comments of the day.

RS:

1. If you bought a Cup Car, I presume you would not put restrictors on it.

2. The 3.8 RSR was an air cooled engine -- comparing it with the Type 996 engine is a flawed comparison in a variety of areas.

3. Subsequent to Mr. Frere's writing, Porsche found a number of ways to increase HP even more.

Hank:

1. I agree with all of paragraph 1 -- I did not get into certain details but tried to say that this type of engine throws driveability and legality out the window (for multiple reasons).

2. As to paragraph 2, considerable weight reduction can be achieved without sacrificing safety but this requires very sophisticated and expensive engineering that Porsche currently does not offer.

3. I agree with paragraph 3 and would go even further by suggesting that one might be better, safer and cheaper off by buying a dedicated race car such as a Type 996 Cup Car than modifying a street car.

Bob

993RS

Bob,
I did not make the comparison with a 996, some else did. Maybe I should have restricted the discussion to "modifications for street usage". This is really what I meant.

Also, I wanted to start a general discussion on this topic, since very often only one particular issue is discussed (chips, or mufflers, etc.).

Robin 993DX

Phil,

I have heard you mention this several times in your past posts about a "sports" muffler.

Can you shed more information on that? Is it a Porsche part? What's the part number?

Thanks