Cobra IRS clarification?

[oz98cobra]

I have a 98 Mustang Cobra with an 01 independant rear suspension fitted.

 

I'm guessing that for the purpose of calculating points to determine which class this car should be in, that I should treat it as if it was a 99-01 Cobra, instead of a 98 - that is Class C (with 5 point handicap) - and then add points for other mods as necessary.

 

Can anyone confirm that I am on the right track here?

[Greg G.]

Sounds reasonable to me. Mitch and Glenn will be the ones to make the final decision in the Texas Region.

[jp99gt]

Daron,

 

Have your region directors look at the horsepower levels between the 98 mod motors and the 99/01 mod motors. Classing yours strictly as a 99/01 may not be accurate. I don't have the numbers with me now, or I'd give you an opinion, but that's where to look at it.

[Greg G.]

Jim there is a 15 hp difference--320 hp vs 305 hp for the '98.

[oz98cobra]

Thanks for the info guys - I will talk to Mitch about it.

 

While we are on the subject of Cobras, it seems to me (and a couple of the other local Ford guys) that the Mustang Cobras and Mach 1 are not fairly classified in the first place - in our opinion they should be in base Class D (with a 5 point - or maybe 10 point handicap)?

 

There is no way a stock 96-98 Cobra is equivalent to 2005 Pontiac GTO on a race track - or a stock 99-01 Cobra a match for a Lotus Elise! And the 05 Mustang GT, with similar HP to the 96-98 Cobra and Mach 1 but with light years better handling, is catagorized as class D with one star? That doesn't seem to make a lot of sense?

 

When we extrapolate the numbers with standard Mustang mods and R compound rubber, there is still no way the old Cobra or Mach 1 is going to be competitive when bumped into Class B or A.

 

I realize that it is an impossible task to devise a class system like this that works for all cars and all mods, but in this case, it seems to be a fairly obvious mismatch? I wonder if other Mustang drivers have noticed the same thing?

[oz98cobra]

And please forgive this newbie if this has been covered and answered before - I know there was some discussion regarding Mustangs during the 05 rule change discussion before I came along, but I couldn't find anything specifically addressing the classification of of 96-98 Cobras and Mach 1s.

[mitchntx]

Help me understand ...

 

Is the IRS a direct bolt in?

Is the gearing the same? LSD the same?

Does it use the same shock and spring package?

 

I see a potential of 14 modification points ...

ring and pinion change +2

Change LSD +2

Change/Added sway bars +2

Relocated suspension mount points +8

 

Notice I said POTENTIAL ... I don't know what all is involved with this change, so obviously the number might change.

 

The way I see it, if a change is made from OEM, it has the potential to add significant points simply because it was a change. Whether the change is an actual enhancement or not isn't part of the equation.

 

Daron, I see your points about classification. I have similar questions about the F-Body classification. But realize, you know the Mustang platform inside and out and I know the F-Car platform inside out. The folks that made up these classification guidelines might not have.

 

If there are some glaring issues, then lobbying for classification changes before the 2006 season is appropriate. But, the 2005 season has begun. Changing the rules now isn't fair.

[oz98cobra]

The ring and pinion and differential is the same - identical - no difference - not changed!

 

In theory, you might be able to argue that the suspension mount points have changed, and you could also say that the sway bar has "changed" - which would result in 10 points - however, ending up with any points assessment that results in a worse situation than a 99-01 Cobra is just plain madness and very infair - and in my case, with my other mods, would result in me being bumped two classes - all the way to Group A - which is more madness!

 

Remember has been done here - the complete stock suspension system has been taken from one model Mustang Cobra, and retro fitted to the previous year model. I am also not the only one to do this - it is a reasonably common update to non-irs Mustangs. Using items already listed under the rules such as "relocated suspension mount points" or "add/change sway bar" are not realistic ways of assessing the points for this situation. Worse case is that it should not result in more than 5 points (or it would effectively rank it higher than than the 2001 Cobra that the rear suspension came out of, even though I have less power and more weight).

[mitchntx]

Like I said ... potential ...

 

You are correct, you can't be the first to do this.

 

Based upon what you've posted, the potential of 4 modification points might be in order.

 

Work with me here. I realize you want to know. Trust me ... so do I. Not being familiar with what you have done means I have ask questions myself.

 

You certainly wouldn't want me to make an un-informed decision for a competitor of yours that would give an advantage, would you?

[Mason]

Mitch,

 

Just to give you a little background on the cars we are talking about, '94-'04 Mustangs were built on a common chassis called the SN-95. Sheetmetal changes were made, so the '99 and up cars are cosmetically different, but the mechanical parts stayed mostly the same. Of the V8 cars, ’94-’95 GT’s used the 5.0L pushrod V-8, the Cobra version was a slightly massaged version and the ’95 Cobra R used a 351ci. ‘96+ cars went to SOHC and DOHC motors. The ’96-’98 GT’s used the SOHC 4.6L while the Cobra used a DOHC version. Up to this point, the front and rear suspensions for all were similar with minor differences in spring / sway bar rates – live axle four-link rear, strut front. Along with the sheet metal changes in ’99, the GT’s received a much improved version of the SOHC 4.6L, while the Cobra’s received a slightly improved version of the DOHC AND an IRS. Assembly lines being what they are, the IRS was built to bolt-up to the existing chassis. Ring & pinion gear for all cars up to this point is 3.27:1. In ’00, the R model was introduced, 5.4L DOHC with IRS and 3.55 gearing. ’03-’04 Cobras got a supercharged version of the 4.6L DOHC, the cars were IRS. All GT’s ’99 plus, including the Mach1 and Bullitt versions, had the 4.6L SOHC and live axle. All had 3:27’s with the exception of the Mach1 (and possibly Bullitt?), which had 3:55’s. The Mach1 and Bullitt were more desirable performance wise of the GT's with slightly more horsepower and lower / stiffer springs / shocks.

 

As you can see, there are a whole mess of model variations within the years on this platform (of course this is true of many cars, not just SN95 Mustangs!). With the exception of the sheet metal, parts can be interchanged between the models without any welding / fabrication required. This makes sense, of course, it would not be profitable to do it any other way.

[Greg G.]

I'm handling issues like this as if they are updating/backdating of a model (even if we're talking about a Cobra vs a GT, etc.) If someone makes a big change to a vehicle (engine swap, entire rear end, etc.), then I have no problem increasing their car to the donor car's class as long as the parts are identical--even if they would have actually had more points/higher class if we break down the mods point for point. I agree with Mitch that potentially this could be considered a 12 point move; however, it wouldn't be fair to allow the donor car to have the exact same parts (and even a higher hp engine in this case), and end up with less pts/lower class. However, if any of those parts are not EXACTLY the same as the potential donor car's (for example, the sway bars are different, or the shocks are different), then I would assess points as usual (either before or after moving the base class to the donor class). I hope that made sense (it's been a long night at work here).

[Glenn]

i agree w/ Greg here. the rear axle swap alone should not cause the car to bump higher in class than the doner car. once the swap is done w/ OEM parts, then asses points for any shocks, springs and sway bars changed that are other than stock from the doner. so far it looks like we need to bump you to the same class as a 99 and up Cobra and use that as a starting point even though you may be down on power. 10-15 hp plays almost no role @ our level.

anyone here not agree?

[oz98cobra]

This works for me.

 

Although we could argue that the end result of a stock 96-98 Cobra with an IRS fitted is not quite equivalent to a stock 99-01 Cobra (more weight with less HP), in the interests of keeping the rules easy to interpret and apply for cases like this, I think bumping the car up to the donor car class is probably the best option to take.

 

So in my case, for calculating points, I would start as a base at the same level as a 99-01 Cobra (Class C plus 5 points) - and then add points for additional mods such as springs, shocks, bushings, etc. in the normal way.

[oz98cobra]

While this subject is being discussed, there is a reverse scenario that, while not directly related to my case, is likely to come up in future.

 

What about the 99-04 Cobra guys who have ditched the IRS in favor of a live axle setup? In this case, I would suggest that it should be considered a zero point modification to install a stock OEM Mustang live axle setup, but of course they would have to take points for additions over and above the OEM live axle parts, such as panhard bar, springs, shocks, etc.

[jp99gt]

Daron,

 

There's no way you could consider the IRS comparable to a standard 4 link solid axle for handling on road courses.

 

I would look at allowing the TA/PHB setup with no additional points if someone did that swap.

[oz98cobra]

Daron,

 

There's no way you could consider the IRS comparable to a standard 4 link solid axle for handling on road courses.

 

I would look at allowing the TA/PHB setup with no additional points if someone did that swap.

 

I agree - it is not comparable, and I didn't mean to suggest it was - I only meant that if someone did this that it would not be something that would incur any penalty points.

 

I think you are suggesting that you would let them add a TA/panhard without penalty to compensate? I'm not sure too many would concur as you would giving away too much - a TA/phb live axle would be faster AND provide a significant weight saving over the IRS!

 

I only mentioned it because there is at least one 99 Cobra - with a live axle and Steeda 5 link - that we are likely to see in the NASA TX TT this year, so we might as well have the situation addressed while Cobra IRS is being discussed.

[mitchntx]

And I want to make sure we are fair and consistent ...

[jp99gt]

Daron,

 

There's no way you could consider the IRS comparable to a standard 4 link solid axle for handling on road courses.

 

I would look at allowing the TA/PHB setup with no additional points if someone did that swap.

 

I agree - it is not comparable, and I didn't mean to suggest it was - I only meant that if someone did this that it would not be something that would incur any penalty points.

 

I think you are suggesting that you would let them add a TA/panhard without penalty to compensate? I'm not sure too many would concur as you would giving away too much - a TA/phb live axle would be faster AND provide a significant weight saving over the IRS!

 

I only mentioned it because there is at least one 99 Cobra - with a live axle and Steeda 5 link - that we are likely to see in the NASA TX TT this year, so we might as well have the situation addressed while Cobra IRS is being discussed.

 

My point was that the IRS is much more comparable to the TA/PHB setup than the IRS is to an OEM live axle setup. Whether you add/subtract some points for the former is one thing, but it's not a straight swap for the OEM setup. It would be a significant penalty to drop in an OEM 4 link live axle setup and then add all the points to bring it up to the stock IRS handling ability - those are points you then lose for other modifications compared to the stock IRS Cobra. Somehow we have to figure out some point swap value for this to make them equal.

 

As to whether the live axle or IRS is faster, it depends on the course. Some road courses are so rough the IRS offers a significant advantage (the local Nelson Ledges comes to mind here). The ability to tune (align) the rear suspension is an advantage for the IRS as well, though most may not take advantage of that.