Cambered Rear Vs. Weight Reduction Vs. Power Mods - Help Me Decide!

[Don Lariviere]

Thanks all for the feedback. After reading through these, weight reduction has become high on my priority list!

Some good news, my desire to make this car as fast as possible and a great opportunity thanks to Cortex means I will be doing 3 things, two of them at once:

1.) Weight reduction (targeting about 100-150lbs of weight loss)
2.) New front and rear aero (my current aero setup is definitely on the weaker end)

The above items will be happening at the same time thanks to my fantastic friend and fellow racer Tri-bar. I should have very good back to back data.

3.) And the cherry on top will be a Cortex cambered rear end along w/4:10 gears. It's on order, but I am not expecting to get the cambered rear anytime soon, so I should be able to provide good before and after data on if the 1.5s-2s claims I have seen are true. I sure hope they are.

I agree with the weight loss, I usually see about 1/2 sec a lap per 100lb minimum.
Front aero is also very important with the mustangs so that is also a good choice.

However I would deviate and get rid of the 3V before I put the cambered rear in (but since you ordered it run it!!) The 3V just has no torque, and without putting in large bores and sleeves it never will. I would change to an LS engine (or Coyote to stay Ford), even with moderately more horsepower the difference in torque will give you a bigger drop in lap times than the rear end. Also running 4.10s with the 3V is asking to blow it up if you are still using the TR3650. You will be well out of useable RPM at Willow Springs and the fast Buttonwillow configurations unless you have the 0.81 fifth gear (or a T-56.) I have settled on 3.73s with my car, seems to work best for all the SoCal tracks (with TR3650 and 0.81 5th,) when I didn't have the Cortex suspension or the 0.81 5th the car was actually slightly faster with the 3.55s then 3.73s.

I'm currently hunting for an LS3 to put in my Cortexed S197.

Don

 

[SMGDHG]

I agree with the weight loss, I usually see about 1/2 sec a lap per 100lb minimum.
Front aero is also very important with the mustangs so that is also a good choice.

However I would deviate and get rid of the 3V before I put the cambered rear in (but since you ordered it run it!!) The 3V just has no torque, and without putting in large bores and sleeves it never will. I would change to an LS engine (or Coyote to stay Ford), even with moderately more horsepower the difference in torque will give you a bigger drop in lap times than the rear end. Also running 4.10s with the 3V is asking to blow it up if you are still using the TR3650. You will be well out of useable RPM at Willow Springs and the fast Buttonwillow configurations unless you have the 0.81 fifth gear (or a T-56.) I have settled on 3.73s with my car, seems to work best for all the SoCal tracks (with TR3650 and 0.81 5th,) when I didn't have the Cortex suspension or the 0.81 5th the car was actually slightly faster with the 3.55s then 3.73s.

I'm currently hunting for an LS3 to put in my Cortexed S197.

Don

Thanks for the feedback Don...What do you rev your 3v to? Check out the following screenshot below.

I used tremec's website to determine my max speed at 7000RPM. I can say with absolute certainty that I will never get near 130mph at Buttonwillow, and I don't do Big Willow. Norcal tracks are all on the slower end, maybe 125mph max. So from what I can tell, the 4:10's would be a benefit for me due to the extra torque to the ground. I believe my tuner set my RPM limiter to 7200 RPM, as he does with all spec mustang race cars. I have the short runner ford racing intake manifold, electric water pump and longtube headers, so the car breathes decent up to 7k. If I install cams, even more so. But I agree that the torque at the upper RPM range is a huge limiting factor. So far no issues revving that high, but I run thicker oil, an oil cooler and am a time attacker.....Usually 3 hot laps per session and then I bring the car in.

 

[mwjscn]

-

 

[SMGDHG]

You may already be aware, but just wanted to mention that these calculators are presenting theoretical mechanical speeds achievable only in a vacuum or sitting on jack stands and don't take into account other real-life external variables like air drag and rolling resistance, especially when in the triple digits.

Hmmh, external forces would only impact the amount of horsepower needed to achieve this from my understanding, so I'm struggling to see how a strictly mechanical equation would not be accurate in real world. Have you experienced calculators like these to not be accurate?

My car is lacking in power, but I'd at least like to think it could get itself to 130mph if the need arose

 

[67GTA]

Hmmh, external forces would only impact the amount of horsepower needed to achieve this from my understanding, so I'm struggling to see how a strictly mechanical equation would not be accurate in real world. Have you experienced calculators like these to not be accurate?

My car is lacking in power, but I'd at least like to think it could get itself to 130mph if the need arose

Agreed, I’ve worked the equation backwards from real world data, using RPM, gearing, tire size and MPH to validate the table.

 

[mwjscn]

external forces would only impact the amount of horsepower needed

That's what I was trying to get at, just wasn't phrased well (hence the unloaded engine only trying to spin a gearset - in that the equation didn't take into consideration the engine's characteristics and ability to tow a certain ratio). Apologies for the confusion.

Since I messed that up, let me try to contribute something of hopefully some value:
This is my favorite transmission gear calculator, since not only does it plot each gear ratio visually on a graph (can see closer or wider gear ratio separations on potential offerings) but you can also add a shift rpm data point to see what your RPM will fall to in the next gear: https://legacypic.uk/transmission/graph.php?

 

[SMGDHG]

That's what I was trying to get at, just wasn't phrased well (hence the unloaded engine only trying to spin a gearset - in that the equation didn't take into consideration the engine's characteristics and ability to tow a certain ratio). Apologies for the confusion.

Since I messed that up, let me try to contribute something of hopefully some value:
This is my favorite transmission gear calculator, since not only does it plot each gear ratio visually on a graph (can see closer or wider gear ratio separations on potential offerings) but you can also add a shift rpm data point to see what your RPM will fall to in the next gear: https://legacypic.uk/transmission/graph.php?

Ok, all is forgiven, because this calculator is AWESOME!!!

Thanks for sending this.

As is, my car is like this:







With 4:10's, it would be like this:




Considering I never get above ~120mph at the tracks I go to, the 4:10's seem to be a no brainer, no? I use 4th gear very frequently, and getting up to 146mph is an absolute joke, won't ever happen on a road course LOL.

 

[Fabman]

Ok, all is forgiven, because this calculator is AWESOME!!!

Thanks for sending this.

As is, my car is like this:

View attachment 91925





With 4:10's, it would be like this:

View attachment 91924


Considering I never get above ~120mph at the tracks I go to, the 4:10's seem to be a no brainer, no? I use 4th gear very frequently, and getting up to 146mph is an absolute joke, won't ever happen on a road course LOL.

The 3v spec mustangs hit 5th gear at Thunderhill with 3:73 gears.

 

[SMGDHG]

The 3v spec mustangs hit 5th gear at Thunderhill with 3:73 gears.

Who’s the goon that you know who shifts into 5th? Speeds are nowhere near 5th gear range even with 4:10’s

 

[67GTA]

Ok, all is forgiven, because this calculator is AWESOME!!!

Thanks for sending this.

As is, my car is like this:

View attachment 91925





With 4:10's, it would be like this:

View attachment 91924


Considering I never get above ~120mph at the tracks I go to, the 4:10's seem to be a no brainer, no? I use 4th gear very frequently, and getting up to 146mph is an absolute joke, won't ever happen on a road course LOL.

What was your peak torque on the dyno?

 

[Bill Pemberton]

I have been to Thunderhill only once , on the original track in this video, but I would bet both SMG and Fab are correct , as with 5 miles of track , wouldn't it depend on the course layout whether one hits 5th or not.

Now how was that for a diplomatic answer during the Christmas Holiday Season!

 

[SMGDHG]

What was your peak torque on the dyno?

Good question. I don't have the dyno sheet in front of me but I want to say peak tq was somewhere between 4.6-5.2k and peak hp was around 6k.

Would love to get cams to raise the rpm of my peak tq.

 

[Fabman]

Who’s the goon that you know who shifts into 5th? Speeds are nowhere near 5th gear range even with 4:10’s

The guy who's won the SMG Championship there 5 out of the last 7 years.
Just got off the phone with Dig Motorsports. The fast ones do hit 5th for a second and they run 3:90 gears.
They do however change out the 5th gear for a lower ratio 5th out of something else, but yes. They do hit 5th.

 

[SMGDHG]

The guy who's won the SMG Championship there 5 out of the last 7 years.
Just got off the phone with Dig Motorsports. The fast ones do hit 5th for a second and they run 3:90 gears.
They do however change out the 5th gear for a lower ratio 5th out of something else, but yes. They do hit 5th.

Did you call them just for this conversation? If so, that is really nice, so thank you

That is really good info, thanks Sal. I wonder what they are revving to. Sean, who did my tune essentially did a copy paste of what the spec mustang cars run, and he set the rev limiter to 7.2k. Said it’s plenty safe. I think I hit around 115mph on the front strait at Thunderhill currently. However I could see that number increasing by 5, maybe even 10mph once I get Hoosiers and the new wing which should have less drag than my current one.


It’s something that I will have to play around with for sure.

 

[Fabman]

Just got off the phone with Roger Eagleton, the driver. Yes, 5th gear is a thing.

https://www.facebook.com/video.php?v=432973495666645

 

[Fabman]

Did you call them just for this conversation? If so, that is really nice, so thank you

That is really good info, thanks Sal. I wonder what they are revving to. Sean, who did my tune essentially did a copy paste of what the spec mustang cars run, and he set the rev limiter to 7.2k. Said it’s plenty safe. I think I hit around 115mph on the front strait at Thunderhill currently. However I could see that number increasing by 5, maybe even 10mph once I get Hoosiers and the new wing which should have less drag than my current one.


It’s something that I will have to play around with for sure.

Yes, I wanted to make sure I wasn't giving bad info....unfortunately that video is from facebook and it won't show up here for some reason. But trust me, its real.

 

[Fabman]

2nd. attempt:

https://www.facebook.com/video.php?v=432973495666645

 

[Fabman]

Nope.

 

[Bill Pemberton]

Now , wasn't that nice , help from one TMO member , thanks from another , and they are pals again. Big reason you should tell your friends about this site, it is all about fast fun and helping others with the passion for tracking/autocrossing/etc.

...............Merry Christmas from TMO where the gift of friendship means helping those other drivers who may kick your ass the next time you hit the asphalt!!!!

 

[Fabman]

Cant seem to upload video either....WTH?