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I have some folks looking to pick up a Mustang to road race in either CMC or AI. They are fixated on the 99/01 Cobra due to the motor, and more so the IRS.
Cost/benefit analysis for running the IRS - or has everyone here converted theirs to stick axle? Issues with the IRS?
Problems with this era Mustang?
Competitive chassis or not?
Input appreciated, thanks.
here we go....
www.corner-carvers.com
bring nomex.
For CMC, I believe the answer is clear, no IRS allowed. Quote below from the CMC eligible vehicles.
ChuckQuote:
1996-04 Ford Mustang 4.6 DOHC N/A V8*(2000 Cobra R and 2003-2004 Cobra models excluded; 4.6
DOHC may run CMC2 only)
* IRS cars must replace the IRS with standard Mustang live axle
CMC#14[/quote]
Thanks Chuck, if they continue to pursue this car I'll let them know to convert for CMC or its AI.
Ut oh, I didn't do a proper search.Quote:
Originally Posted by cjlmlml
LOL - I'm just looking for the simple answer to say either don't bother with this car, or just find a regular GT shell and drop XX motor in it.
Also, what's a good DFW mustang forum with used cars?
Mike,
I think the consensus would be:
1. Smooth track would favor the stick axle
2. Rough track would favor the IRS
3. Standing starts would suck with an IRS
4. Alignments are critical for the IRS to work properly
5. AI power levels might prove too much for the half-shafts
6. Diff cooler is a MUST for IRS to live
Ditto what Marshall said except the half shafts are stout. I have an 03 cobra rag top with delrin bushings etc. About the same p/w as my AI car but obviously heavier. The AI car with MM setup has a ton more grip. Not an apple to apple comparision, but if I were building from scratch I would favor the solid axle. Also the IRS is a pain to work on unless you drop the whole unit, which is not hard to do. FWIW FMR
Quote:
Originally Posted by MikeP99Z
As is typical with people thinking that they might like to try something, they are focused on the wrong thing. They need to decide what class they want to run in first and then build to that. Beyond both being V8 pony cars, CMC and AI are diametrically opposed in concept.
Beyond that, a "good" IRS is theoretically an advantage in road racing. The Mustang IRS is not "good" and can't be made "good" under the AI rules. There are certainly plenty of band aids that make it serviceable for AI but most people trying it in AI eventually give up and go solid.
I would recommend CMC. If they go AI, I would recommend going with something other than the Cobra motor and the IRS.
Richard P.
AI power levels themselves should be fine with IRS - legend abounds with crack cases but I think a lot of those are in the 500+hp range and many are just plain abused. Still the duration of use in road racing vs drag might be something to consider as Marshall is suggesting with the cooler.Quote:
Originally Posted by MikeP99Z
I'd think the car would be competitive out of the box but not necessarily a front-runner. The 4V is pretty stout and puts out the HP though lower torque numbers. I'd consider upping the gears to 3.55 or 3.73. We are actually including that era in consideration for our next car as a chassis but looking at a different package (engine/trans/diff) and it probably will be a solid rear.Quote:
Originally Posted by MikeP99Z
IIRC, the '99-01 cobra's also had 28 spline halfshafts, where the '03-04's upgraded to 31 splines to handle the supercharged motor. Personally, with all the pros and cons of the IRS vs. a solid axle, I'd skip the cobra and the large 4v altogether and go with a GT.
A 3 valve dropped into an SN-95 would be really nice...
Take what I say with a grain of salt though, I'm still a rookie :roll:
They eventually want to end up in AI. They figured - street car-ish play in DE/TT, add cage for TT/CMC2, collect parts to upgrade to AI.
They've read the AI rules, and would probably end up adding things to the car that would bump them out of CMC pretty quickly.
I am pretty sure the diffs in the 04 are 31 spline just like the other 3V's (like the S197) so that makes sense.Quote:
Originally Posted by edrock96GT
Same path I took but good for them finding a less expensive starting point! :oops:Quote:
They eventually want to end up in AI. They figured - street car-ish play in DE/TT, add cage for TT/CMC2, collect parts to upgrade to AI.
They've read the AI rules, and would probably end up adding things to the car that would bump them out of CMC pretty quickly.
Depending on the cost of the snake they may want to consider buying an existing car unless they are in fact looking to run it as a street car (as I did). Factor in cost of cage and other safety equip and you might be able to find a cheaper ready-to-go with spare parts (my achiles heel right now - S197 parts are all high priced). Look at me ...maybe I am learning something....
I tried to convince them that pre-built something was better than scratch.
But, they want to go down this road to do things themselves, learn the ins and outs of the rules, and the chassis/parts development.
They understand that they will likely spend quite a bit more doing it this way.
Although, if some smoking deal came down the road before they purchase a street car, they might reconsider.
That really is something you can't put a price on...not really. It may have taken me longer and cost more but I learned so much more about car dynamics than I would have if I just got a car and started racing it...probably would not have listened to advice nearly as well either.Quote:
Originally Posted by MikeP99Z
Well good for them - are they Texas folks <crossing fingers>?
Yep, Texas.
Work harder to convince them....to buy MY car.Quote:
Originally Posted by MikeP99Z
4V isn't great at this low power level. No torque and getting compression costs money and it's heavy.
Why people decide to build when they can buy cars for $0.25 on the dollar is beyond me....especially when it's a nationally competitive car. :?
for a street car, the 4V and IRS combo is fantastic...for AI...not even close to ideal.
Mike
The 99 was the first year of the 4.6 Cobra and IRS. I recall from my Mustang mags, there were some real problems with wheel hop on launch through 00. Most of those issues were minimized in later models; however, the problem will come back as more HP is applied and traction control is removed. The 4 valve motor had some further tuning by Ford to maximize HP in 01 and later models. Obviously, the 03 and 04 models are monsters but are far too expensive. I personally would not go with the IRS due to maintenance and wheel hop and stay away from 99. That said, I would love to have that high reving, 4-valve 4.6 pulling my ass around the track! So, I'd go with a 01 or 02 Cobra on a great deal and lose the IRS. Just a rookie's opinion.