Soo happy!! 3.90's are on!

[combatstang]

Marc,I think you made an awsome choice going with 3.90s,Steven loved how his car pulls,and has some what convince me.It's just until I can see him or you pull consistent 1.7-1.8 60fts and below 5 sec.330 fts(which is what I can do now,and on a crappy prepped track on Nitto DRs),I would still be worried about putting it on(this is just my concern on track only,I bet that car of yours is a monster on the street,it would probably totally kill me street light to street light)I know the car must feel completely different now.By the way,Is your idling problem fixed with the IAC completely??

haha.. correct.. i know i can do those 60fts.... just not at LACR.. ask him about it, they never EVER prep there track.. i hate it!!

but dont worry i will be at the track soon, with steven..


My idle problem is fine.. i just get a surge..and can't fix it.. impossible!! i tried it all..

Thanks

Marc

 

[jtfx6552]

if you had two cobras with thee same power, same driver skills, and one had 3.55's and one had 3.90's the geared cobra will walk the other cobra.. not by much but it will.. PERIOD!!... That's the bottom line, thats why I did it...


Marc

I don't agree. There is a list on another site ET's vs modifications, the top cobra's all have 3.55's.
I don't know if the link will be allowed, but here it is:
http://www.modularfords.com/forums/showthread.php?t=7081

In the top 25, only number's 9 and 21 have gears. If gears were the must have go fast mod, wouldn't cars with gears dominate the list?

 

[jtfx6552]

JT...the majority of the facts you present are accurate and indisputable. Also, I agree that if a car is traction-limited, lower gearing can have a detrimental affect.

However, with traction (IRS or not), a car that is geared to take advantage of its powerband (ie...optimally-geared) will out ET (meaning out accelerate in the 1/4 mile) a car with less-than-optimal gearing. 3.55s and 3.73s are less than optimal for the majority of 03 Cobras - even with a redline limited to 6500 rpm.

"Optimal gearing" for the 1/4 mile typically means that you gear the car to run several hundred rpm above peak HP at the end of the run in 4th gear. A stock 03/04 Cobra makes peak power at ~6000 rpm, meaning you want to run the car pretty much to redline in 4th gear - or above that if your peak HP rises.

The idea is to maximize average HP in each gear. In 1st, 2nd, and 3rd gear, that means calculating optimum shift points, for which rear gearing has little or no effect. However, for 4th gear, it means gearing the car as described above.

Put another way, if you're going to use all 4 non-OD gears anyway (which we will all do with aftermarket gearing), you'll go quicker if you maximize torque multiplication (lower gears) in each gear. Torque is multiplied with gearing, so for best ET, gear the car so that it goes through the traps ~500 rpm above redline in 4th gear.

Again - this assumes traction. If you race on street tires or are otherwise traction-limited, then you may or may not go quicker with an optimum power gear.

Also, N/A DOHC Cobra's all came with 3.3x 1st gear ratios, not low 2.x. Most of us that actively raced these cars still used very aggressive gearing, for all the reasons mentioned above, and even more so to get the car moving smartly in 1st and 2nd gear, because you spend most of your time in that part of the track.

Bob

Bob, all the facts I presented are indisputable, as they are the laws of physics.


Bob the 4.55's and 5.13's got popular long before 99 N/A Cobras, I was talking about small block chevy's with powerglides.

What is the typical torque of a n/a cobra have? 330 ft lb? Now the N/a probaly doesn't make the torque until much higher RPM, but to keep it simple, lets use the peak numbers. With 3.35 low and 4.56's that is 15.26 to 1 in low, times 330 is 5035 ft lbs. An '03 with 515 ft lbs and 3.55's has 4863.
With IRS there is little prayer of getting more than 4863 to the ground, I suspect, and you would know more about drag race straihght axle set ups, that it is hard even with a race straight axle set up.

More gear in and 03 will get more wheel spin in first, and more wheelspin on the 1-2. Time lost to wheelspin that can't be recovered in the 1320.

My .02.

 

[11secCobra]

Bob, all the facts I presented are indisputable, as they are the laws of physics.


Bob the 4.55's and 5.13's got popular long before 99 N/A Cobras, I was talking about small block chevy's with powerglides.

What is the typical torque of a n/a cobra have? 330 ft lb? Now the N/a probaly doesn't make the torque until much higher RPM, but to keep it simple, lets use the peak numbers. With 3.35 low and 4.56's that is 15.26 to 1 in low, times 330 is 5035 ft lbs. An '03 with 515 ft lbs and 3.55's has 4863.
With IRS there is little prayer of getting more than 4863 to the ground, I suspect, and you would know more about drag race straihght axle set ups, that it is hard even with a race straight axle set up.

More gear in and 03 will get more wheel spin in first, and more wheelspin on the 1-2. Time lost to wheelspin that can't be recovered in the 1320.

My .02.

thats why us drag racers use slicks :thumbsup:

 

[Bob Cosby]

Bob, all the facts I presented are indisputable, as they are the laws of physics.

LOL. Kindly pardon me for even trying to imply any doubt in these 'facts'. Are you, by chance, an engineer? My remark about the "majority of facts" was in reference to your "no need for higher numericals" comment and your "2.x" gearing comment (talked about below).

I agree, in full, with your discussion of Torque vs HP. And I don't even try to pretend to be smart.

Bob the 4.55's and 5.13's got popular long before 99 N/A Cobras, I was talking about small block chevy's with powerglides.

Ok - being we are talking about Cobras, and a lot of n/a Cobras use that gear, I made an assumption that you weren't talking about Chevy's and powerglides. My bust.

What is the typical torque of a n/a cobra have? 330 ft lb?

No, usually less than 300.

Now the N/a probaly doesn't make the torque until much higher RPM, but to keep it simple, lets use the peak numbers. With 3.35 low and 4.56's that is 15.26 to 1 in low, times 330 is 5035 ft lbs. An '03 with 515 ft lbs and 3.55's has 4863.

No arguement there.

With IRS there is little prayer of getting more than 4863 to the ground, I suspect, and you would know more about drag race straihght axle set ups, that it is hard even with a race straight axle set up.

Just because it is an IRS should not limit the traction. You can hook the IRS, it is just heavy and prone to breakage.

And I disagree with your premise that is hard to hook that 5035 ft/lbs. I did it consistently with my car on Drag Radials and a very basic, street-style suspension. I could have done better on slicks or ET Streets. In my mind, limiting the gearing to 3.55s is limiting your potential.

More gear in and 03 will get more wheel spin in first, and more wheelspin on the 1-2. Time lost to wheelspin that can't be recovered in the 1320.

If you're entire point is built upon a traction-limited scenario, then I have no arguement, and would refer to you my statements above saying the same.

However, with traction, 3.55s and 3.73s keep the car undergeared, and will result in a slower ET than a car gearned more optimally.

My .02.

Ditto.

One more quick question....how much ET did you lose when you went from stock gears to 3.90s, 4.10s, or whatever?

 

[Bob Cosby]

I don't agree. There is a list on another site ET's vs modifications, the top cobra's all have 3.55's.
I don't know if the link will be allowed, but here it is:
http://www.modularfords.com/forums/showthread.php?t=7081

In the top 25, only number's 9 and 21 have gears. If gears were the must have go fast mod, wouldn't cars with gears dominate the list?

In my opinion, this is misleading reasoning. Just because a lot of folks don't swap gears, doesn't mean that they wouldn't go faster with a gear swap. In fact, there are many reasons to believe otherwise.

For example, for those cars that still have an M6 tranny and stock gearing, look at the ET vs MPH. In general, they ET very poorly in relation to their MPH, meaning that they are not accelerating at near the potential of the power-to-weight ratio that they have available to them. That's not a slam on driver ability or choice of gearing - most of those cars are street cars, and that certainly has to be taken into account. I simply reject (completely) the notion that because most of those folks don't have (or list) aftermarket gears, then 3.55s must be the way to go fast.

Also, some of those cars are like hpbyhermann's, in that they have an A4 tranny. That's a whole different ball game with gearing because of the converter.

Additionally, some don't list gears, even though they have them. #3 03flamedcobra is an example.

Some others are most certainly traction-limited, as they run on DRs. #6 F8LBITE is a great example (even though he still manages an awesome 60 ft on DRs).

Bob

 

[combatstang]

In my opinion, this is misleading reasoning. Just because a lot of folks don't swap gears, doesn't mean that they wouldn't go faster with a gear swap. In fact, there are many reasons to believe otherwise.

For example, for those cars that still have an M6 tranny and stock gearing, look at the ET vs MPH. In general, they ET very poorly in relation to their MPH, meaning that they are not accelerating at near the potential of the power-to-weight ratio that they have available to them. That's not a slam on driver ability or choice of gearing - most of those cars are street cars, and that certainly has to be taken into account. I simply reject (completely) the notion that because most of those folks don't have (or list) aftermarket gears, then 3.55s must be the way to go fast.

Also, some of those cars are like hpbyhermann's, in that they have an A4 tranny. That's a whole different ball game with gearing because of the converter.

Additionally, some don't list gears, even though they have them. #3 03flamedcobra is an example.

Some others are most certainly traction-limited, as they run on DRs. #6 F8LBITE is a great example (even though he still manages an awesome 60 ft on DRs).

Bob

Bob, gears make the cobra slower... its ok.. let them keep there 3.55's... :beer:

and we will drive our slower geared cobras :rollseyes

 

[§ilver§nake]

Easy fix, run a taller tire! :rockon:

My thoughts exactly...

BTW, I have 4.10s.
:rockon:

 

[combatstang]

My thoughts exactly...

BTW, I have 4.10s.
:rockon:

and it made ur car slower huh? :bash:

 

[BADASS03SVT]

when u had my dakota with 3.92's she ran 13.90...only change was to 4.56's and the truck went 13.7s. they work, they help....if you dont think so lets race... :rockon:

 

[jtfx6552]

LOL. Kindly pardon me for even trying to imply any doubt in these 'facts'. Are you, by chance, an engineer? My remark about the "majority of facts" was in reference to your "no need for higher numericals" comment and your "2.x" gearing comment (talked about below).

I agree, in full, with your discussion of Torque vs HP. And I don't even try to pretend to be smart.


Ok - being we are talking about Cobras, and a lot of n/a Cobras use that gear, I made an assumption that you weren't talking about Chevy's and powerglides. My bust.


No, usually less than 300.


No arguement there.


Just because it is an IRS should not limit the traction. You can hook the IRS, it is just heavy and prone to breakage.

And I disagree with your premise that is hard to hook that 5035 ft/lbs. I did it consistently with my car on Drag Radials and a very basic, street-style suspension. I could have done better on slicks or ET Streets. In my mind, limiting the gearing to 3.55s is limiting your potential.


If you're entire point is built upon a traction-limited scenario, then I have no arguement, and would refer to you my statements above saying the same.

However, with traction, 3.55s and 3.73s keep the car undergeared, and will result in a slower ET than a car gearned more optimally.


Ditto.

One more quick question....how much ET did you lose when you went from stock gears to 3.90s, 4.10s, or whatever?

In the beginning....lol. when the '03's first came out, there was strong idea that the '03's would respond like previous 4.6 stangs to steep gears. There were many online arguments about how gears would help. Several members here went back and forth about it, challanges were made, and we were all gonna fight it out at the first '03 cobra shootout in bowling green. At that shootout, only two or three 4.10 cars showed up. The 3.55 cars ran better et's and better trap speeds. This obviously was same track, same day results. Since the '03s were almost brand new it was a good test because there were just not many mods available, and the state of tuning was pretty even.

After the shootout, a good friend of mine with 4.10's and I went to Atco. We both had similar if not exact tunes, he had an aftermarket x to my stock h, and I was running consistant mid 11's. His car had yet to break into the 11's.
I tried driving his car, we switched my tires from my car to his to eliminate that variable. We stayed all night, and he finally got one 11.99 out of the 4.10 car. My conclusion after driving the car was, it was very hard to modulate all the torque to the tires, and even when you managed to pull that off, when going into second you had your choice of lossing et to a slow as hell soft granny shift, or blazing the tires all through second.

Agter that night, he then switched back to 3.55's.

What do I believe this proves? That a typical pullied chipped '03 is better off with 3.55's.

With a straight axle, or more important in my opinion, "weight transfer aiding" mods, things may be different. Aftermarket lightweight k-members and A arms, 90-10 shocks, an aluminum block (like the 99 car you had) a blower and associated parts that didn't weigh anything, etc, and maybe the 5000+ ft lbs at the line could be taken advantage of.

I can tell you really tell you totally understand the trade offs associated with gears. If we were in person talking, I think it would be obvious we are both making the same point, al beit talking about different sides of the same coin. I just wanted to point out that more gear is not some no brainer, easy mod that always improves et.

Another reason '03's respond less to gears is because of the torque curve, Obviously with a manual transmission, once the clutch is out, with the tires stuck, engine RPM is dictated by the speed the car is moving. With N/A cars, the car has to be moving kinda fast before the engine starts to hit the power band. This makes a good launch with low numerical gears almost impossible. Either the clutch needs to be slipped perfectly, or the tires need to spin some but while moving the car out, so the car can be putting power to the ground while it is in it's power band. The '03 doesn't have this problem. Full torque is available almost right off idle. In other words, with n/a small block race cars with a typical high rpm power band, some of the ET improvement attributed to more torque multiplication of the higher numerical gear, is really due to being able to keep the car in the powerband on launch.

To sum up my thoughts on gears, the 3.55's are fine. If higher gears were free, maybe they'd be worth a try. But if I was gonna spend money to go faster, I'd spend the $500-1000 higher numerical gears cost installed, on more power, weight reduction and or weight transfer, and maximize what the 3.55 could do before switching.

To answer your last question on previous cars, I always lost et on back to back weeks when just adding a steeper gear. Then I'd spend money to get back to were I was, and rationalize that in it's new form, the car really did need the steeper gear. My 351W powered 82 GT ended up with 4.56's and 28 x 9 slicks with that reasoning.

In my opinion, this is misleading reasoning. Just because a lot of folks don't swap gears, doesn't mean that they wouldn't go faster with a gear swap. In fact, there are many reasons to believe otherwise.

For example, for those cars that still have an M6 tranny and stock gearing, look at the ET vs MPH. In general, they ET very poorly in relation to their MPH, meaning that they are not accelerating at near the potential of the power-to-weight ratio that they have available to them. That's not a slam on driver ability or choice of gearing - most of those cars are street cars, and that certainly has to be taken into account. I simply reject (completely) the notion that because most of those folks don't have (or list) aftermarket gears, then 3.55s must be the way to go fast.

Also, some of those cars are like hpbyhermann's, in that they have an A4 tranny. That's a whole different ball game with gearing because of the converter.

Additionally, some don't list gears, even though they have them. #3 03flamedcobra is an example.

Some others are most certainly traction-limited, as they run on DRs. #6 F8LBITE is a great example (even though he still manages an awesome 60 ft on DRs).

I agree that '03's do et poorly in relation to their trap speeds. I don't think it because they don't have enough gear. I think it is because in stock form they are nose heavy and transfer weight poorly.

It is funny that I look at F8LBITE's, Johnny L's (1.58 on Dr's) and "Venomous John's" 60 Ft's with stock suspension and conclude that the cars do have enough gear, and you conclude the opposite.

With your '04 I hope you do whatever suspension mods you have planned before adding the gear. I'd love to see your pure before gear and after gear results.

Like most, I'm sure the straight axle will have more gear when it goes in because it doesn't make sense to build up an axle with a gear you are convinced you won't want in the long run.

With my car, which will not have skinny's, slicks or an aftermarket front suspension, I know more gear would cost $, help my clutch, hurt my halfshafts, and at best not add anything to my et at the track.

 

[Bob Cosby]

I'm sure we would agree on most everything if we sat down and discussed this, and in reality, we do. However, there are still a few things I disagree with - and if we have to agree to disagree, that's ok with me.

In the beginning....lol. when the '03's first came out, there was strong idea that the '03's would respond like previous 4.6 stangs to steep gears. There were many online arguments about how gears would help. Several members here went back and forth about it, challanges were made, and we were all gonna fight it out at the first '03 cobra shootout in bowling green. At that shootout, only two or three 4.10 cars showed up. The 3.55 cars ran better et's and better trap speeds. This obviously was same track, same day results. Since the '03s were almost brand new it was a good test because there were just not many mods available, and the state of tuning was pretty even.

That's neat, but it proves little. If anything, it just shows that people hadn't yet figured out the car.

After the shootout, a good friend of mine with 4.10's and I went to Atco. We both had similar if not exact tunes, he had an aftermarket x to my stock h, and I was running consistant mid 11's. His car had yet to break into the 11's.
I tried driving his car, we switched my tires from my car to his to eliminate that variable. We stayed all night, and he finally got one 11.99 out of the 4.10 car. My conclusion after driving the car was, it was very hard to modulate all the torque to the tires, and even when you managed to pull that off, when going into second you had your choice of lossing et to a slow as hell soft granny shift, or blazing the tires all through second.

"modulate all the torque" heavily implies traction limited. As I've said a few times before, my gearing recommendation depends on good traction. If you're running street tires or even DRs (depending upon many things), then you may indeed have trouble.

With a straight axle, or more important in my opinion, "weight transfer aiding" mods, things may be different. Aftermarket lightweight k-members and A arms, 90-10 shocks, an aluminum block (like the 99 car you had) a blower and associated parts that didn't weigh anything, etc, and maybe the 5000+ ft lbs at the line could be taken advantage of.

If you're traction limited due to not having some of the stuff above, then gears might not help. Otherwise, even cars with all our weight in front can be made to hook.

BTW...90/10s suck.

Another reason '03's respond less to gears is because of the torque curve, Obviously with a manual transmission, once the clutch is out, with the tires stuck, engine RPM is dictated by the speed the car is moving. With N/A cars, the car has to be moving kinda fast before the engine starts to hit the power band. This makes a good launch with low numerical gears almost impossible. Either the clutch needs to be slipped perfectly, or the tires need to spin some but while moving the car out, so the car can be putting power to the ground while it is in it's power band. The '03 doesn't have this problem. Full torque is available almost right off idle. In other words, with n/a small block race cars with a typical high rpm power band, some of the ET improvement attributed to more torque multiplication of the higher numerical gear, is really due to being able to keep the car in the powerband on launch.

Agree that low-rpm power is much better with the 03/04, and that the 03/04 can make much better use of the 3.55s than the older cars would have. In other words, they are better matched to the powerband than a 99/01 Cobra. However, with traction, you would still accelerate faster if you can multiply that torque. This would be especially important off the line, as you spend ~12-15% of your ET in the first 4.5% of the 1/4 mile, meaning gains here (be it traction and/or improved acceleration through gearing) pay off big time at the other end.

To sum up my thoughts on gears, the 3.55's are fine. If higher gears were free, maybe they'd be worth a try. But if I was gonna spend money to go faster, I'd spend the $500-1000 higher numerical gears cost installed, on more power, weight reduction and or weight transfer, and maximize what the 3.55 could do before switching.

Anybody spending $1000 on an IRS gear swap has issues.

To answer your last question on previous cars, I always lost et on back to back weeks when just adding a steeper gear. Then I'd spend money to get back to were I was, and rationalize that in it's new form, the car really did need the steeper gear. My 351W powered 82 GT ended up with 4.56's and 28 x 9 slicks with that reasoning.

Not sure I follow you here, but so long as you didn't over-gear the car, and so long as you were able to get traction, the car will accelerate with whatever gear maximizes average HP in each tranny gear through the 1/4. I think that's one of those "indisputables" we had above.

BTW...I'd also like to again caveat that gear choice for automatics is quite different than what we are talking about here.

I agree that '03's do et poorly in relation to their trap speeds. I don't think it because they don't have enough gear. I think it is because in stock form they are nose heavy and transfer weight poorly.

Disagree mostly. Just being heavy is misleading - you have to consider power-to-weight. Nose heavy only hurts if it prevents you from getting traction. Once you have traction, it is irrelevant.

I think it is due mostly to poor gearing, relatively modest driving (few people have pro-shifted trannies or really powershift their T56s with no regard to breakage), and traction-limited conditions.

With your '04 I hope you do whatever suspension mods you have planned before adding the gear. I'd love to see your pure before gear and after gear results.

Like most, I'm sure the straight axle will have more gear when it goes in because it doesn't make sense to build up an axle with a gear you are convinced you won't want in the long run.

Ya, it will all be done at once. Data would be nice, but I have a pretty fair idea of what works, and have my mods already planned out. Among other things, and as you alluded to, it makes no sense to through the live axle in without the gear, springs, shocks, and control arms of my choice.

With my car, which will not have skinny's, slicks or an aftermarket front suspension, I know more gear would cost $, help my clutch, hurt my halfshafts, and at best not add anything to my et at the track.

Though I don't think you can say definatively that it wouldn't help ET, it certainly might not if you don't have traction.

I think I need to go count the amount of times I posted the word "traction" in this thread.

Hope you had a Merry Christmas.
Bob

 

[jtfx6552]

I'm sure we would agree on most everything if we sat down and discussed this, and in reality, we do. However, there are still a few things I disagree with - and if we have to agree to disagree, that's ok with me.


That's neat, but it proves little. If anything, it just shows that people hadn't yet figured out the car.

Cars were very similar, only difference was the gearing, and the 4.10's were slower. Comparing the ETs then and comparing with the ETs "on the list" now, The results were the same, there were just less differences to obscure that fact.

"modulate all the torque" heavily implies traction limited. As I've said a few times before, my gearing recommendation depends on good traction. If you're running street tires or even DRs (depending upon many things), then you may indeed have trouble.

AT BG, track prep was outstanding, still the 4.10 cars could not compete.

If you're traction limited due to not having some of the stuff above, then gears might not help. Otherwise, even cars with all our weight in front can be made to hook.

An 03/04 with driver weighs in at 3800 lbs plus, staticly, much less than half that weight on the rear wheels. As you know friction depends on the "normal" force. Even if the 03/04 transfers enough weight to lift the front wheels, and given the moment arm on stock sized tires is about 1 foot, what coefficient of friction will you need to hook up 5000 lb ft?, looks like 1.31. Now that is with 3.55's! Now with 4.10's the numbers grow to 5774 lb ft and a cf of 1.51. On a super prepped track with slicks front wheels in the air, maybe. On a car with "stock" suspension with weight on the front wheels...sounds like spinning to me. For comparison, it looks like you 99 routinely held about 1.38-1.46 (300 lb ft at the engine, 15.26:1 reduction 3300-3500 lbs total weight). Of course, in actuality with all cars on launch, there is the added smack of the inertia of the rotating engine and flywheel. VHT is a racers friend...

BTW...90/10s suck.

Agreed

Agree that low-rpm power is much better with the 03/04, and that the 03/04 can make much better use of the 3.55s than the older cars would have. In other words, they are better matched to the powerband than a 99/01 Cobra. However, with traction, you would still accelerate faster if you can multiply that torque. This would be especially important off the line, as you spend ~12-15% of your ET in the first 4.5% of the 1/4 mile, meaning gains here (be it traction and/or improved acceleration through gearing) pay off big time at the other end.

Agreed, the issue is traction and what it takes to get it. First you need to transfer weight so whatever tires you have in the back can get the grip to transfer even more weight, Since my car is a street car that I like to be able to go around turns and over bumps, transfer and hence traction are limited. For a purpose built 1/4 mile car, I'm sure the suspension can be tweaked to take advantage of the extra T in 1st.

Anybody spending $1000 on an IRS gear swap has issues.

I have heard numbers that high talked about ($800 does seem more typical), the pumkin needs to come out they say, so it is pricier than on a straight axle.

Not sure I follow you here, but so long as you didn't over-gear the car, and so long as you were able to get traction, the car will accelerate with whatever gear maximizes average HP in each tranny gear through the 1/4. I think that's one of those "indisputables" we had above.

You implied I had never taken a car and upped the gears. While I learned form others mistakes and haven't done it on my '03, I have done it in the past. The theoretical results were the car would be faster, in actual racing it wasn't.

BTW...I'd also like to again caveat that gear choice for automatics is quite different than what we are talking about here.

Agreed, however, the auto '03 I was in launched hard on 3.55's since the convertor gives some multilplication.

Disagree mostly. Just being heavy is misleading - you have to consider power-to-weight. Nose heavy only hurts if it prevents you from getting traction. Once you have traction, it is irrelevant.

Since the ability to translate rotaional force into movement depends on the normal force and friction, the distribution of weight and "tightness" of the suspension is critical. If the weight from the front can't be transferred to the rear then the required cf goes through the roof, i.e. trying to move 3800 lbs with only 1750 on the rear axle is a recipe for tire smoke.

I think it is due mostly to poor gearing, relatively modest driving (few people have pro-shifted trannies or really powershift their T56s with no regard to breakage), and traction-limited conditions.

I know a few who shift their T-56's as fast as they can be shifted, so I know it isn't that. The lack of transfer does hurt, though, because quick shifts, especially the 1-2 can really break loose the tires, I have seen ET drags, ET streets and BFG dr's all go up in smoke on a good shift.

Ya, it will all be done at once. Data would be nice, but I have a pretty fair idea of what works, and have my mods already planned out. Among other things, and as you alluded to, it makes no sense to through the live axle in without the gear, springs, shocks, and control arms of my choice.

Once you do those mods, then the car is no longer the typical '03/'04 Cobra. I am sure more gear won't hurt in that situation. It is ashame we will never know how much, exactly it helped. What do you think just the ratio change will take off your ET?

Though I don't think you can say definatively that it wouldn't help ET, it certainly might not if you don't have traction.

I think I need to go count the amount of times I posted the word "traction" in this thread.

I like to drive my car to the track, which means DR's in the rear, normal sized wheels and radials up front, non drag shocks and springs. Even on the best prepped tracks, the car is traction limited.

Hope you had a Merry Christmas.
Bob

Thanks, I did. I hope you did, too.

JT

 

[Bob Cosby]

Cars were very similar, only difference was the gearing, and the 4.10's were slower. Comparing the ETs then and comparing with the ETs "on the list" now, The results were the same, there were just less differences to obscure that fact.

Everything else being equal, 4.10s will not result in slower acceleration. It is simply not physically possible.

Of course, drivers, engines, and traction are not equal. As such, I still disagree (completely) with your premise.

AT BG, track prep was outstanding, still the 4.10 cars could not compete.

See above.

An 03/04 with driver weighs in at 3800 lbs plus, staticly, much less than half that weight on the rear wheels. As you know friction depends on the "normal" force. Even if the 03/04 transfers enough weight to lift the front wheels, and given the moment arm on stock sized tires is about 1 foot, what coefficient of friction will you need to hook up 5000 lb ft?, looks like 1.31. Now that is with 3.55's! Now with 4.10's the numbers grow to 5774 lb ft and a cf of 1.51. On a super prepped track with slicks front wheels in the air, maybe. On a car with "stock" suspension with weight on the front wheels...sounds like spinning to me. For comparison, it looks like you 99 routinely held about 1.38-1.46 (300 lb ft at the engine, 15.26:1 reduction 3300-3500 lbs total weight). Of course, in actuality with all cars on launch, there is the added smack of the inertia of the rotating engine and flywheel. VHT is a racers friend...

No doubt.

Once the front wheels are off the ground - even a millimeter - all the weight is on the rear tires. Further, a great deal of it will be on the rear tires under a launch that doesn't quite pull the tires. If you are limiting your car to a "stock suspension", then it is quite possible you'll not get the traction you need. Then again, you only need enough traction to pull a similar 60 ft as the lesser-geared car in order to out-accelerate it (assuming the tires don't go up in smoke on the 1/2 shift - which is a consideration).

Agreed, the issue is traction and what it takes to get it. First you need to transfer weight so whatever tires you have in the back can get the grip to transfer even more weight, Since my car is a street car that I like to be able to go around turns and over bumps, transfer and hence traction are limited. For a purpose built 1/4 mile car, I'm sure the suspension can be tweaked to take advantage of the extra T in 1st.

Ok. FWIW, my 99 was hardly purpose-built, and did a great job of hooking. My 04 will be no more purpose-built....we'll see how it goes.

You implied I had never taken a car and upped the gears. While I learned form others mistakes and haven't done it on my '03, I have done it in the past. The theoretical results were the car would be faster, in actual racing it wasn't.

My experience has been significantly different. I think you'll find that most more serious racers would agree.

Agreed, however, the auto '03 I was in launched hard on 3.55's since the convertor gives some multilplication.

Hence the reason it is very different from the subject we are discussing.

Since the ability to translate rotaional force into movement depends on the normal force and friction, the distribution of weight and "tightness" of the suspension is critical. If the weight from the front can't be transferred to the rear then the required cf goes through the roof, i.e. trying to move 3800 lbs with only 1750 on the rear axle is a recipe for tire smoke.

But you will never have only that amount when accelerating, as even under very light acceleration, some amount will be transferred.

I know a few who shift their T-56's as fast as they can be shifted, so I know it isn't that.

I've been racing stick cars a long, long time. Very few people shift the cars near their potential, and T56s aren't exactly conducive to it anyways.

The lack of transfer does hurt, though, because quick shifts, especially the 1-2 can really break loose the tires, I have seen ET drags, ET streets and BFG dr's all go up in smoke on a good shift.

Tis possible.

Once you do those mods, then the car is no longer the typical '03/'04 Cobra.

We each have our opinions.

BTW....doing a straight axle swap actually hurts front/rear weight bias.

I am sure more gear won't hurt in that situation.

If changing the gear simply "didn't hurt", I wouldn't bother. I'm changing the gear in order to HELP.

It is ashame we will never know how much, exactly it helped. What do you think just the ratio change will take off your ET?

Assuming I can hook it, perhaps a tenth - maybe a .15.

I like to drive my car to the track, which means DR's in the rear, normal sized wheels and radials up front, non drag shocks and springs. Even on the best prepped tracks, the car is traction limited.

Ok. I haven't decided if I will drive or tow. I will use stock springs - but the shocks/struts will likely be adjustable. I plan to run DRs to start, and slicks on occasion. The car won't be anywhere near as serious as my 99 though - my ET to MPH ratio isn't going to be that good either.

 

[BLWN03]

Very good stuff guys keep it coming.

 

[Carbd86GT]

damn, Bob vs JT, this is good. Everyone, you should be learning something here. I am.

 

[SWEET03COBRA]

Well I have listened to everyone and here is a question. Do you think a gear change would be more effective on a vert than a coupe. I have ET streets and I can't get it to jump off the line. It kind of bogs down, traction isn't an issue for me. 3.73s, 3.90 or no gear change?

 

[Black2003Cobra]

Well I have listened to everyone and here is a question. Do you think a gear change would be more effective on a vert than a coupe. I have ET streets and I can't get it to jump off the line. It kind of bogs down, traction isn't an issue for me. 3.73s, 3.90 or no gear change?

Ideally, (if traction is not an issue), you want to cross the traps just at redline with these cars. That will maximize the average power in each gear, and hence, give you the best results. In theory, (and if you could build one), what you’d really want to have is a CVT (continuously variable transmission) to keep the engine at peak power the entire time sort of like they use on some sleds. Personally, I’d pick a little less gear (based on what your max trap speed is) so that you have some extra headroom to insure you don’t risk hitting the rev limiter and/or having to shift into fifth before you hit the traps. That spread sheet I sent you should help you decide. Weight only factors into what your max trap speed will be for the given amount of power you have. Again, I'd suggest being a little conservative, i.e., pick the highest trap speed you'd think you could ever possibly hit (and maybe even pad it a bit). If you have to shift out of 4th, you'll be screwed.

 

[SWEET03COBRA]

Now how do I chage it so the spedometer reads right now?

 

[BLWN03]

Now how do I chage it so the spedometer reads right now?

Get the gear ratio changed thru the tune...or you'll need one of those speed-cal thingy's from dallas mustangs...they are in all the mag's

Jay