auto-x guys opinions wanted.

[cobraetti]

have about 5 go auto-x's under my belt and wanted to ask for some opinions, since I plan to do this as much as possible. I am doing a gear swap (4:10) this week from the stock 3:27's, what degree will this enhance the performance and power to the wheels in second gear. I also would have though I would place better than others, I felt the IRS would be an advantage over a solid rear for this kind of driving?.........any tips for a auto-xer w/ a N/A cobra?

 

[Jmac72187]

I have autocrossed with 3.55's and 4.10's. I prefer the 4.10's for autocross. That being said, I probably won't change my gears because I am doing open track days and the 4.10's aren't right for me.

About your place, it is all experience. You could drive a car that is well enough equipped to beat most cars out there but without seat time and really learning from your mistakes, you won't beat most cars out there.. Just keep going out and get as much seat time as possible.

 

[cobraetti]

thanks 4 the reply

 

[TroyV]

Johnny Mac is right. With only five or so events of experience, you likely haven't found your car's absolute limit. It is very easy to get caught up in modifying or making changes to your car to enhance performance when what would be much more productive (and more cost effective) is to concentrate on you and your driving.

That said....

Years ago, I was in the same boat, although the car was a 99gt. After stagnating....reaching the limit of the car, I made changes which would allow me to be at the very top of 2nd gear a predominant amount of the time on course. I'm not exactly sure what 4:10's do to your second gear. I'm sure that there are many calculators online that will tell you the answer. If you look at the type and design of the courses you are running, you refer to your dyno chart, and use your gear selection to place the meat of your power in the range you'll use most in those conditions, then you can't go wrong. In the case of my old GT, the gear selection was for 3:73's. That combined with an extended rev limit (comp cams and springs) was able to push to 7k in 2nd with a decent amount of power.

Best of luck with whatever you decide.

 

[Jmac72187]

Johnny Mac is right. With only five or so events of experience, you likely haven't found your car's absolute limit. It is very easy to get caught up in modifying or making changes to your car to enhance performance when what would be much more productive (and more cost effective) is to concentrate on you and your driving.

That said....

Years ago, I was in the same boat, although the car was a 99gt. After stagnating....reaching the limit of the car, I made changes which would allow me to be at the very top of 2nd gear a predominant amount of the time on course. I'm not exactly sure what 4:10's do to your second gear. I'm sure that there are many calculators online that will tell you the answer. If you look at the type and design of the courses you are running, you refer to your dyno chart, and use your gear selection to place the meat of your power in the range you'll use most in those conditions, then you can't go wrong. In the case of my old GT, the gear selection was for 3:73's. That combined with an extended rev limit (comp cams and springs) was able to push to 7k in 2nd with a decent amount of power.

Best of luck with whatever you decide.

My father is running 4.10's in his 2V. I felt that with our courses, a 3.73 or 3.90 gear would perform better. The 4.10 would put the car at a great RPM to get up and go but the rev limit and power band just aren't there. The car cannot rev high enough and on some straights and some of the sweeping slaloms, the car would be pinging off rev limiter almost long enough to up shift. With cams, springs and a higher rev limiter the 4.10's would work very well.

If we ran this set up on race tires, I would definitely do a swap down to 3.73's for the extra MPH.

Depending on your course designs (likely tighter and slower than the ones we run on), the 4.10 gear may work very well. Also, the 4V in your car will allow for some extra RPM. I would do some playing around with a gear calculator like Troy said and figure out exactly what gear will work best for you.

John

 

[Conechaser]

What class are you building the car for? If it's SCCA and you are in an SN95, then for Street Touring classes (STX or STU) you are stuck with what was avail as a factory option to be legal as you can't update/backdate. ESP does allow update/backdate and will get you to a 3.55 from the Cobra R. CP,SM, or higher then you can run anything.

My concern with a 4.10 is that you could run out of gear in 2nd and need to to to 3rd on longer courses. That means a 2 shifts where you are not on the gas and also opportunities to mess up those shifts and create more issues. At Solo Nationals I found the rev limiter in 2nd with my 3.55's. It's also a great gear for the road courses I run as I can stay out of 5th.

 

[cobraetti]

good point, I have not been on any with the much straight away......... yet

can't wait to find out..............no more 3:27's

 

[MIKE PHILLIPS]

I ran my 01 cobra w/4:10s, shifter and a SCT tuner (for the gear change) and I was placed in the SSM class. The gearing is perfect for autox with the 4v ( higher rpm) I ran in 2nd gear and never hit the rev limiter (close in a few instances). The N/A cobra loves the 4:10s the gear changes keep you in the power band. I was very happy with them.. Change the shifter to a Tri-Ax ( my opinion) or some other aftermarket shifter that has adjustable stops, much faster shifts and very positive shifts.

 

[ESP Cobra]

I ran my 01 cobra w/4:10s, shifter and a SCT tuner (for the gear change) and I was placed in the SSM class. The gearing is perfect for autox with the 4v ( higher rpm) I ran in 2nd gear and never hit the rev limiter (close in a few instances). The N/A cobra loves the 4:10s the gear changes keep you in the power band.

As Jan said, it depends on the course. The other factor is your tire OD. Running a taller tire will somewhat diminish the effect of a lower gear ratio. While I do agree a N/A 4v loves to rev, I'm not sure 4.10's are the best well rounded option for every Cobra and every course. One of our local events last year would have pushed me into third on the long back straight with 4.10's. Not saying it's not a great gear for getting the car in the power band, just better for 1/4 mile than auto-x.