TomF

Yep, see Mike's excellent DIY about how to do the timing. It is not for the faint of heart, however. It is an 7/10 on the difficulty scale. See if you can locate a knowledgeable friend to help you out, that would be best. Otherwise, I would find a tuner to do it for you. Get it wrong and you grenade a very expensive motor....

Stealth 993

Nope, all pre-varioram cars will have this, it's our flaps moving. IT'S TOTALLY NORMAL!! You are looking a little to much into this!!!

Steve W

Mongrelcat (Jason) suggested that I look at and perhaps provide some input with regards to this thread.

First off, myself along with the various engine builders I work with have found that as these cars age, the following reason these engines are not outputting full power:

a) full throttle not being achieved at the throttle body and/or bad WOT or TPS sensor (-20 hp)

b) non-operating/stuck intake resonance valves (-20 to 30hp)

c) failure of one side the the twin plug ignition system, equivalent to a 7-8 degree overall ignition retard (-20 hp)

That said the output numbers from every type of dyno is subject to operator input settings which will skew the numbers +/- 30% any which way. This includes DynoDynamics, Dynapacs, Mustangs, Superflows, Maha, and Land&Sea. The only dyno that is impervious to any operator alteration are Dynojets, (because there are none) and are consistent enough in output numbers that a car dyno'd in New York can be used as a direct comparison to another Dynojet run in Los Angeles. This is why many racing bodies use Dynojets to classify cars. The gear that the car is tested in (3rd or 4th) doesn't seem to affect the final output numbers much - perhaps within 3-4 hp. You must also use SAE correction in adjusting the final output numbers as it takes the atmospheric conditions and equalizes to what the power would be under a fixed standard SAE condition of temperature, humidity, and barometric pressure. Without it the numbers can be +/- 10 hp either way. I would not take the numbers from this Dyno Dynamics dyno too seriously unless there is a database of several other 911s in there run under the same operator input settings to compare to.

Dyno cell setup and configuration are also important in obtaining accurate and consistent numbers. The best dyno I've ever worked in is a completely closed cell chamber with ~100,000 CFM blowers entering from the front wall of the camber, and another 100,000 CFM extraction system at the rear - it really is a wind tunnel in there. The worst setup is where the car is backed into a block wall with no where for the exhaust to exit - the car literally will ingest some of it's exhaust back into the intake, screwing up air/fuel reading and lowering power output. Ambient air temperature will also affect the output numbers. Bosch Motronic utilizes the air intake temperature sensor in the MAF to determine a overall trim down of the programmed ignition timing to prevent knock under high heat conditions. If the intake air temps are for example 120 degrees F, the system will adjust itself to run less ignition advance than if it were at 50 degrees, the resultant hp difference being anywhere from 10-15 hp.

Finally as haygeebaby noted, the car is a Tiptronic, so that in itself will account for a much lower output power on the dyno because of loss through the viscous type clutch.

Before dynoing a car, ensure that all of the above are in optimal condition, and the rear tires are inflated to at least 36 psi. Track cars with rear tires inflated at 25 psi will dyno 10 hp lower than when we inflate them up to 36. Hope this helps.

haygeebaby

Thanks for the input gents. I really appreciate it.

SW from LA - nice to get your input mate. Actually - I have no doubt that the 911chip I have in my car makes a big difference. I re-installed the stock chip and can tell with the butt dyno that the car is not as strong or responsive. Will get some more dyno results for others to use as reference for upgrading their cars - which is really why I am continuing to update this thread.

Steve - what can a dude like me do to check A, B, and C are all working good ? I've been accounting for a 20% loss in my calculations - what do you think is the best figure to use with tips ?

The garage room we where in for the dyno was pretty small, and the rear of the car was facing a closed garage door. I'll get the shop to open the garage door so the exhaust gets vents out of the room. Some good points.

Actually - I have a lot of confidence in my engine - it does pull well. So definetly not worried now after all the great input from you lot. If I do a conversion to dynojet numbers - I get a figure around 289bhp at the crank.

Like one of the first posts said - "ignorance is bliss !" How true ... spend some cash upgrading, spend some cash dyno'ing, get some white hairs, and spend some more cash becuase you spent cash dyno'ing.

Looking forward to the dyno on Saturday - will post my findings for your guys then.

Regards

Lorenfb

"I re-installed the stock chip and can tell with the butt dyno that the car is not as strong or responsive."

Which is the usual case when comparing to a performance chip that essentially
just "pushes" the timing, i.e. most noticeable in below WOT full load, and usually
results in lost power at WOT during a dyno run. The latter results from
the knock control system retarding (less for stock chip) the "pushed" timing
under full load at WOT on the dyno because of the excessive performance chip
timing.

Bottom line: So, one in most cases trades-off mid-range ("butt dyno") results
with a performance chip for WOT full load actual/real performance using
the stock chip as is the case for all late engine management systems with
knock control.

TomF

Hey Steve, I owe you an apology. I didn't realize that he had installed one of your chips. I have heard only 100% positive feedback about your chips. Sorry for the mistake!

Steve W

I use a PST2 to test and verify functions of A and B. I never really tried it otherwise, but as not everyone has access to this or a Bosch hammer, or PIWIS, you can try to verify what you can by the following information:

a) have someone press on the throttle pedal all the way down while you verify that the throttle opens all the way at the throttle body. As for the TPS, 993 use a variable potentiometer that the DME adapts to to determine full closed to fully open. A PST2 or PIWIS will tell you the opening angle in the menu to verify operation. When the DME has been disconnected from the car, the engine must be started with the throttle fully closed, as the self adaptive unit will select the smallest opening angle of the throttle as the engine idle position.

b) resonance valve operation is easily activated through the drive links menu of a PST2 or PIWIS. However you can try to check and verify the function of it with the following information. It is vacuum operated though a electronic solenoid, with vacuum leaks or partially stuck valves being a common problem.

"Checking Resonance Flap for Operation:

When the ignition is switched on, the resonance flap is closed by vacuum action. When the ignition is switched off, the resonance flap is opened (rest position). The opening and closing noise is audible in the engine compartment.

4. Resonance Flap

The DME control unit activates a vacuum-controlled diaphram valve which either opens or closes the resonance flap.
The resonance flap is closed between 3,000 prm and 5,000 rpm and at throttle opening angle of > 60 degrees.
Due to the ignition sequence, the intake system is alternatively supplied by both tanks. Due to the firing order, air is drawn in an alternating manner from both intake system tanks. If resonances occur, the intake frequency of one row of cylinders matches the natural frequency of the pressure vibrations in the respective tank. The natural frequency is determined by the geometry of the intake pipes, the resonance pipe and the tanks. A crucial factor, however, is the total length of the pipe from the actual intake cylinder to the next cylinder being supplied, the distribution in intake and the resonance pipe lengths as well as the depth of the tank in the direction of flow. In the no-current state, the resonance flap is open. As soon as the ignition is switched on, however, it is triggered and closed. If the DME control unit detects that the engine is being started, the resonance flap is opened again.

Pin 1 from the DME unit is used to control the resonance valve."

c) Disabling one side of the ignition at a time, starting the car and noting the character of the idle and rev activity is the easiest way to determine if one side or the other has a failure. With one side disabled, properly working, the engine should easily start and almost idle and rev just like stock. If car does not start, or runs very rough with one side disabled, it indicates a fault on the side that is still connected. On a 964, disabling one side is easiest by disconnecting one of the ignition modules at a time (located under the ignition coils). On a 993 this is not possible so it easiest to disable one side by disconnecting one of the power or ground leads to the ignition coils. Do not disable an ignition system by disconnecting the spark lead off a coil or distributor - the RFI leak will cause havoc with the car and/or possibly damage.

As for loss with Tips, my memory is not that clear as I don't see many dyno runs with such to provide a conclusive answer. Off the top of my head, it can be 20 hp, but then recently I was surprised with one that tested almost close to that of a manual, FWIW. I have not heard of a conversion from a Dyno Dynamics run to a Dynojet. I don't think that would be accurate because of operator variability on a D.D. machine. I've also seen many DD runs that seem to come inline numerically with a Dynojet so I don't have an answer for you on that.

While I heard that was one of the issues encountered with the chips you are/were selling, such is not the case when the software is properly developed. Fuel optimization is the primary factor in achieving torque, power and response gains. Ignition timing optimization for the fuel used is also important, and ideal ignition timing is achieved just right before the threshold of knock, so that the knock sensors never activate and reduce the effective overall ignition timing. Optimum fuel and ignition maps are determined extensively on both chassis and Superflow engine dynos, and extensively tested under both road and track racing conditions, while monitoring knock counts with a PST2 or hammer. When all is said and done, the reoptimized program registers no more knock counts than the stock chip. Thanks for your concerns though!!

Although Steve and I share similar names and initials, we are actually two separate individuals. We used to get confused for each other a lot on forums, though we look nothing alike. Steve Weiner of Rennsport is located in Oregon and I wish I had just a fraction of the engine building knowledge he has amassed. Myself, I am located in Los Angeles and am strictly specialized in the software tuning of these engines.

Lorenfb

"Fuel optimization is the primary factor in achieving torque, power and response gains. Ignition timing optimization for the fuel used is also important, and ideal ignition timing is achieved just right before the threshold of knock"

Hyperbole, and Porsche/Bosch weren't able to this initially, right? Please!

Note: Above quote basically as found in the course outline for a high school auto shop.

TheOtherEric

Great post by Steve Wong. The only thing I have to add about the Resonance Flap is my theory that they may operate correctly at standstill but might not actuate at speed if the vacuum system is weak or the flap is failing. You can test the vacuum system (see shop manual) to ensure it's strong. Or simply watch the flap while on the dyno if you don't mind sticking your head in there.

Collapsed lifters may also cause power loss. I believe that causes the valves to not open fully, which would hinder air flow and hence power. I have absolutely no idea how to check that, so I'd love to hear suggestions.

drmatera

Not to derail this post but are you enjoying your turbo kit TheOtherEric?

TheOtherEric

Yes, very much so! So far so good, but I only have a couple thousand miles and a few track days on it.

Sorry for the OT.