New Rules are up

#61

kregg wrote:

If you’re worried about your diff the first thing to do is check it yourself after a race. I know I’m going to check mine multiple times to see where I’m at and gather more data. I encourage all of you to do the same. The more data we have the better. You want to be proactive when trying to be compliant, don’t wait till impound to be your first compliance check. If you are consistently over the limit I would discuss it with your regional director. I know the next step I would try would be different fluids.

#62

Elephant4 wrote:

Since we have to use OEM-equivalent fluid in the diff (“substituted”), how does changing the fluid help? Seems like that is breaking one (harder to tech) rule to comply with another (easier to tech) rule.

Steve D.

#63

Elephant4 wrote:

If you’re worried about your diff the first thing to do is check it yourself after a race. I know I’m going to check mine multiple times to see where I’m at and gather more data. I encourage all of you to do the same. The more data we have the better. You want to be proactive when trying to be compliant, don’t wait till impound to be your first compliance check. If you are consistently over the limit I would discuss it with your regional director. I know the next step I would try would be different fluids.[/quote]

Simon, that is the problem with this rule that has stern implications(disqualification). As one that is looking over the rules you’se guys should already KNOW how temperatute effects the lock-up before making such a far reaching rule.

Discuss…again

Regards, Robert Patton

#64

Steve, I think (sorry, I really do not remember) that Red Line NS diff lube has more (or less) additive to the oil so that lock-up is greater. I know that I’m not going to use it(again?see post number 2, page 1) so I’ve not bothered to get the specifics.I know where my diff checks-in at cold temperatures.Like Simon suggests, I’ll,too, be checking it when it is hot. Although I can’t see what could be done to make a difference? I’ll stick with Mobil 1 which I believe to be a substitute that is an acceptable substitute.Yes this is a slippery subject.

Regards, Robert Patton

#65

So help me understand to what extent limited slip matters. If my diff breaks at 60ft-lbs and yours brakes at 30ft-lbs, under what conditions is mine better and under what conditions is yours better? Is 30ft-lbs worth of delta even noticeable?

#66

Scott, good question.

Laura’s car, last weekend at Roebling, would do nothing but spin the inside tire on the tight right turns.It was so bad that Jim Robinson could only coax a 127 out of it.We just left it parked for Sunday’s race.

The taxi was hooked up and was good for 124s all day long.Same newish R888s on the rear of both cars.

I’ll play (cold) torque tester this weekend and advise the numbers.

Regards, Robert Patton

PS, should the torques test similar I’ll have to find some other conspiracy theory about why the passenger rear tire was spinning so bad.

#67

If you did something that you knew to be illegal and got caught you’d have reason to be incredibly embarrassed. On the other hand, if you built a car that you truly believed to be legal and got caught out on something like the diff lockup value, only minor embarrassment is called for. The reaction from the group might (read probably) make it seem like it is greater than a minor offense, but it really is a minor thing that can be fixed if it happens.

I have to agree that this is a potential can of worms. As far as I know, the 65ft-lb number is for a differential at ambient temperature and was originally cited as a means of determining whether a rebuild of the LSD clutches was indicated. That doesn’t take into account the affects of wear, manufacturing tolerances, lube, etc., that might affect a hot diff just off the track.

#68

Patton wrote:

[quote]Scott, good question.

Laura’s car, last weekend at Roebling, would do nothing but spin the inside tire on the tight right turns.It was so bad that Jim Robinson could only coax a 127 out of it.We just left it parked for Sunday’s race.

The taxi was hooked up and was good for 124s all day long.Same newish R888s on the rear of both cars.

I’ll play (cold) torque tester this weekend and advise the numbers.

Regards, Robert Patton

PS, should the torques test similar I’ll have to find some other conspiracy theory about why the passenger rear tire was spinning so bad.[/quote]

Lets get into the subtlties tho. If my diff brakes 30ftlbs higher then yours, yet you do not experience wheel slip in a corner, do I have a performance advantage?

And when is a locked diff an advantage? Wouldn’t a locked diff be kinda uncooperative going around a turn?

I’m not trying to split hairs, I’m trying to understand if a tighter diff is generally better, or if it’s just a matter of “if no wheel slip in a corner, then you are 100% good to go”.

#69

Sorry if this is already buried in here somewhere but I’m interested to see the affect of temperature on dif. breakaway. Has anyone done a before/after test at a trackday?

Re: locked difs. I’ve been told that a locked dif can be a minor advantage in the dry but a very major disadvantage in the wet.

#70

Patton wrote:

Could be the rear swaybar setting

#71

Patton wrote:

I saw that on MyLaps and meant to congratulate you. That was you in the Taxi, correct? 1:24 is fast at Roebling. I’ve never done a 1:24 there, not even once. WTG.

#72

/quote]

Could be the rear swaybar setting[/quote]

Sean, it could very well be. The 911 car is just a bit softer in the rear.

Regards, Robert Patton

#73

allenr wrote:

[quote]Sorry if this is already buried in here somewhere but I’m interested to see the affect of temperature on dif. breakaway. Has anyone done a before/after test at a trackday?

Re: locked difs. I’ve been told that a locked dif can be a minor advantage in the dry but a very major disadvantage in the wet.[/quote]

No, it is not buried in this 8 pages.That is the reason for the 8 pages. The potentially DQed racers are looking for data.

Re: welded diff/locked diff…good discussions on this. Perhaps return this horse to the barn before it escapes. I know of no one that has a “welded” diff.

This topic seems to have run it useful course.Eight pages and we’ve covered alot of ground with clarifications and good discussion all along the way. Actually, for there to have been such little for us to complain about, speaks well for the volunteers that are involved with the rules for 2009.

On the outstanding topic of diff testing, I think it best to contact my regional Spec E30 represenative and voice my concerns.

My thanks to all of them for their consideration.

Regards, Robert Patton

#74

Elephant4 wrote:

leggwork wrote:

[quote]
And just because the rules say you can substitute diff lubricant (substituted means OEM equivalent, BTW), with the new rule specifying a breakaway value, you have to meet that spec.[/quote]

Simon, Bruce, et al.
What fluids are we allowed to run? Please clarify.
-Vic

#75

victorhall wrote:

[quote]
Simon, Bruce, et al.
What fluids are we allowed to run? Please clarify.
-Vic[/quote]

9.3.11.5. Differential lubricant may be substituted.

“Substituted” means that original OEM equivalent items may be used.

Good question, I’m not sure how you determine what oils are oem equivalents? Something for us to think about. The same rule applies to engine oil and I don’t think we are saying you have to run a specific weight for engine oil. Something else to consider or clarify.

#76

Thanks Simon.
-Vic

#77

Elephant4 wrote:

[quote]victorhall wrote:

[quote]
Simon, Bruce, et al.
What fluids are we allowed to run? Please clarify.
-Vic[/quote]

9.3.11.5. Differential lubricant may be substituted.

“Substituted” means that original OEM equivalent items may be used.

Good question, I’m not sure how you determine what oils are oem equivalents? Something for us to think about. The same rule applies to engine oil and I don’t think we are saying you have to run a specific weight for engine oil. Something else to consider or clarify.[/quote]

I would think that “equivalent” oils will not markedly change the action of the diff clutches in a con-compliant LSD so I’m still stuck with the question of how to make a diff that does not break at 65lb comply by using a different “equivalent” to the oil that makes it noncompliant… I think I have a headache…:huh:

#78

You can tune the Red Line fluid by buying the NS flavor and a bottle of friction modifier. The more you add, the more the diff’s clutches will slip. I don’t know how this works when hot, but they tell you to add the friction modifier until you can no longer hear the clutches chattering at low speeds.

I currently run straight Red Line NS in my tired old junkyard diff. It breaks away at 45ft lb hot (using the lug nut torque wrench method), and it makes bad noises in the paddock.

#79

laz wrote:

[quote]You can tune the Red Line fluid by buying the NS flavor and a bottle of friction modifier. The more you add, the more the diff’s clutches will slip. I don’t know how this works when hot, but they tell you to add the friction modifier until you can no longer hear the clutches chattering at low speeds.

I currently run straight Red Line NS in my tired old junkyard diff. It breaks away at 45ft lb hot (using the lug nut torque wrench method), and it makes bad noises in the paddock.[/quote]

Thanks. I have two diffs for my car -neither has been installed as I’m converting an eta car. Guess I’d better do some testing on my local test track (highway 132).