It's too bad that you sell some awesome upgrades yet you have no knowledge of the cars they go on. TT's gearbox is always getting 100% of the power and torque. All the torque is sent to the rear wheel with about 5% "robbed" from it with the Viscous Coupling. When there is more slip, up to 40% is sent to the front. So 9ff has the upgrade is to aid people in seriously increase the engine power without having to worry about the drive train. But for a normal TT, nothing is changed.

 

997TT has electronically actuated clutches that could sends up to all of the power to the front. During braking, unless you clutch in the whole time, there is an issue of engine braking. If you have engine braking at the front wheel, the handling is pretty erratic. On the 996TT with the Viscous Clutch, it won't matter as it's only 5% of the power is transmitted.

 

Nice inputs on this forum! Where have you been all this time?

 

Correct, not only has that but the car now anticipated the power curve and preslip to the front diff based on collective data on TPS, RPM etc. So basically the car knows it will slip before it does unlike the 996TT which would wait to correct through PSM only after slippage occurred. The 997TT watches and knows ahead time and will disburse power to the front wheels electronically to prevent PSM from tripping. Big improvement. This means that yu can leave PSM on most of the time and the car will not interfere with closing the TB 99% of the time.

 

what is the estimate crank and wheel hp with a stage2 kit (ECU, Exhaust, Intake, Diverter)?

 

Alex: I still disagree most of the time. When you are threshold braking in our cars, you should be jamming the pedal to the floor and in full ABS mode anyway. Again, no difference between the two, engine braking or not. If you are not at threshold braking, then P has to have things pretty screwed up if it would allow a significant change in the braking characteristics. I haven't driven a 997 at the track so I can't comment from experience.

Stephen, we were talking about under braking, but yes, I understand the 997 PSM is superior. I think I have a way to defeat the PSM on the 996 that leaves ABS. I will report when I test it.

 

[quote=ColorChange] When you are threshold braking in our cars, you should be jamming the pedal to the floor and in full ABS mode anyway. quote]

This is one way to look at things, I don't know many (any) pro drivers who ride the ABS while entering a corner, they do hit it now and then as an alarm bell. I like to use the ABS as well, but does not make me right, nor faster. "Should", I am not so sure, "can be jamming" is more appropriate.

As far as an earlier post about gearboxes and having to change 1st and 2nd gear when you do a 2WD conversion, I hope it is a joke. GT2 and TT gearbox strength is the same, except for the oil cooling bit, which you might need if you club race in an enduro. For most sprint races, you will not even HAVE to use cooling. A tilton pump and simple spray setup will be more than enough for most track avid drivers, let alone for any street driving.

 

Tim,

You don't have to agree or disagree with Alex on this FWD clutch system used on the 997 Turbo and the issues normally associated with permanent 4X4 and braking, Alex is just stating what Porsche says on the tin not something coming out of his head.

 

This is one way to look at things, I don't know many (any) pro drivers who ride the ABS while entering a corner, they do hit it now and then as an alarm bell. I like to use the ABS as well, but does not make me right, nor faster. "Should", I am not so sure, "can be jamming" is more appropriate.

First, a little bit of semantics but threshold braking means braking at the limit of traction. This then requires a straight line because otherwise, you would be using some traction for turning, and not threshold braking anymore (braking and turning is called trail braking – i.e. braking after turn in). Second, a good abs (ours included) is superior to all drivers, racers included, that is one of the reasons why it is eliminated from many series. The primary reason for this is each individual tire can be at the limit of traction. Non abs braking has to hope you have a perfectly changing brake bias (as your weight transfer varies) and that the track is perfectly smooth and uniform in grip. Let’s not even get into lap after lap consistency. No human can put all four tires on the limit like a 4-wheel abs system does. So, in fact, ABS does make you faster (all other things being equal).

Kiko - I don't follow your post?

 

I don't think anyone is debating whether ABS is better or worse than what a human can do via threshold braking/pumping the brake pedal. Rather, I think Jean was debating whether or not ABS really makes faster lap times in ideal situations with a good driver

A lot of amateur drivers tend to drive their cars like go karts. Even with the best brakes and fastest engine, most race drivers subscribe to the 'smoother is faster' ideology, which rarely includes stomping on the brakes and engaging ABS except in the most dire of situations.

In a perfect lap with a perfect pilot/driver, the driver won't need to threshold brake nor activate ABS because he/she won't be braking that intensely at any given moment. I know it is slightly counter-intuitive, but it makes sense when you realize how much excess momentum you scrub off.

 

I was replying to the disengaging of the front wheel power. Since I was a kid messing with 4WD RC cars, we had to use one-way bearing to disengage the front wheels from getting power under braking. If not, the engine could cause erratic behaviors in handling. I'm not an engineer so I can't explain why. I just know that the new 997TT elec clutch system varies the power delivery to the front and disengages during hard braking. If your doing threshold braking, I'm sure you don't want the the engine to increase or decrease your braking pressure as a fully connected front drive does. Another word, you can't really "threshold brake" if the engine is connected.

The 997 C4 and C4S still uses the less expensive viscous coupling as 996TT. It deliver power but does not deliver engine brake. This helps power out of corners.

To state a fact, under threshold braking, only the front tires are at the limit, the rear is only there for the ride. Changing brake bias could help turn in by having a tad too much brake force in the back to correct a "tight" car. By no means it's meant to put all 4 wheels at the limit in one single braking situation.

 

A lot of amateur drivers tend to drive their cars like go karts. Even with the best brakes and fastest engine, most race drivers subscribe to the 'smoother is faster' ideology, which rarely includes stomping on the brakes and engaging ABS except in the most dire of situations.

Chase: This is a common misconception and your interpretation is wrong. The later you brake, and the stronger you brake, the more you can “extend the straight” and the faster you will be. The best way to do this is to jam the ABS at the end of the straight (for normal turns). For every bit you don’t do this, I will be quicker.


In a perfect lap with a perfect pilot/driver, the driver won't need to threshold brake nor activate ABS because he/she won't be braking that intensely at any given moment. I know it is slightly counter-intuitive, but it makes sense when you realize how much excess momentum you scrub off.


Quite simply, this is BS. Let’s try a simple example where we reach the 300’ braking marker side by side at the same speed, 120 mph. When you start braking at the 300’ mark at ½ threshold to reach the maximum 70 mph corner entry speed, you are going 120 at the 300’ mark, 100 at the 200’ mark, 90 at the 100’ mark, and 70 at turn-in.

When I come in using threshold braking, I am going 120 mph at he 300’mark, I am doing 125 at the 200’ mark and then jam the brakes (abs of course), I am going 90 mph at the 100’ mark and get to the exact same 70 mph corner entry speed you did.

I just blew by you and every time you don’t use the maximum g capability of the car (in this example of threshold braking) you will be beaten by someone who does. This ignores any potential mechanical issues (overheating brakes, preserving tires, etc.) or other outside factors.

I think I’ve been quite clear here.



Moving on to Jean, it’s my pleasure to lecture you threshold braking, you’re welcome.

You should state your opinions as such, do not make them sound like the only truth, that is the only point I was trying to make, many people read these boards and you can be confusing more than one driver out here.

What I have expressed are not an opinions, they are facts. Those that are confused by them (it sounds like you are), are confused because they do not understand that they are wrong.



"Riding the ABS" is one technique that is good for less experienced drivers, such as myself, but it does not mean it is the right way to drive faster, far from it. I don't want to take this off topic as it is an interesting transmission discussion, I just thought I should pinpoint this statement in case anyone reading it was confused.

As I explained in the prior response, outside of mechanical or other issues, “riding the ABS” is right way to drive faster.

Jean, you will find it impossible to dispute my example for normal turns and normal conditions. Please try if you can.

 

Alex … Wrong again. J Please read.

I was replying to the disengaging of the front wheel power. Since I was a kid messing with 4WD RC cars, we had to use one-way bearing to disengage the front wheels from getting power under braking. If not, the engine could cause erratic behaviors in handling. I'm not an engineer so I can't explain why. I just know that the new 997TT elec clutch system varies the power delivery to the front and disengages during hard braking. If your doing threshold braking, I'm sure you don't want the the engine to increase or decrease your braking pressure as a fully connected front drive does. Another word, you can't really "threshold brake" if the engine is connected.



The ABS system doesn’t care where the braking force comes from (rotors, engine, air resistance, … anything). The ABS system simple tries to control the slip ratio of that particular tire (for braking usually 10-20%) and will maintain this. So, I don’t really care what the engine braking is doing, the abs will handle it.


The 997 C4 and C4S still uses the less expensive viscous coupling as 996TT. It deliver power but does not deliver engine brake. This helps power out of corners.

I think you are saying that the viscous coupling applies little engine braking and helps with putting power down … OK, I agree.


To state a fact, under threshold braking, only the front tires are at the limit, the rear is only there for the ride. Changing brake bias could help turn in by having a tad too much brake force in the back to correct a "tight" car. By no means it's meant to put all 4 wheels at the limit in one single braking situation.

You are wrong and in fact stated an ERROR … not a fact. As I have stated earlier, the abs simply maintaina a desired slip ratio and it does this at all four corners if you hit the brake pedal hard enough. If you don’t, you will not be maxing out your braking g’s and if you aren’t doing that, you are not driving the car as fast as possible.

 

Hey guys,
I'm reviving this thread... Not the threshold braking thread as that should probably be in a separate place (albeit very interesting and informative).

Has anyone completed this since? Any feedback or updates that can be shared? I know that there are lots of folks considering this mod...I personally am!

 

I did it a couple of months ago. No regrets at all. If you do much driving in very cold or wet climates though I wouldnt do it.