Soo happy!! 3.90's are on!

[SWEET03COBRA]

thanx

 

[primo]

Red03Dave needs to chime in!

 

[projekZERO]

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.



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


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...



Agreed


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.




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.


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.



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


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 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.



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?



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.



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

JT

theres an old man out here that has a white cobra coupe dynoed 420 hp and 420 tq.

yet he managed a 11.5 @ 116 mph. hows that for e.t. vs. mph and his cobra is stock weight this is off a 1.6 60 ft.

Oh by the way. he has 4.10's

enough said.

 

[SWEET03COBRA]

Well if I can find someone to put in the gears for a good price I will hook it up and find out.

 

[jtfx6552]

theres an old man out here that has a white cobra coupe dynoed 420 hp and 420 tq.

yet he managed a 11.5 @ 116 mph. hows that for e.t. vs. mph and his cobra is stock weight this is off a 1.6 60 ft.

Oh by the way. he has 4.10's

enough said.

Ok, how about me, 11.41 with 441 rwhp, stock gears. Enough said.

 

[Bob Cosby]

Or me. 11.43 with 355 rwhp, 4.56 gears. Is that enough said?

 

[11secCobra]

Ok, how about me, 11.41 with 441 rwhp, stock gears. Enough said.

i went 11.11 on 445rwhp and 4.10s. enough said :thumbsup:

 

[redstaf426]

Yeah yeah,okay!!enough said lol!! :lol:

 

[2003Slobra]

I have seen enough from the track point of view, but for someone who just wants to SOTP feel on the street, would 3.90's be just about right. I will still go to the track, but not enough for me to worry about if I am going to be running out of room in 4th or not. Other than that the information is great! :banana:

 

[11secCobra]

I have seen enough from the track point of view, but for someone who just wants to SOTP feel on the street, would 3.90's be just about right. I will still go to the track, but not enough for me to worry about if I am going to be running out of room in 4th or not. Other than that the information is great! :banana:

honestly, i wouldnt get gears unless your car is anything but a track car.

with that being said, if you want your car to be at its full potential in the quarter and only use 26" tires and keep the eaton, id go for 3.73s or 3.90s

 

[projekZERO]

Ok, how about me, 11.41 with 441 rwhp, stock gears. Enough said.

you ran a 11.4 @ 122.98 mph thats 6.5 mph faster but u didnt mention that

and cecil dragway is 320 ft alt

he did this at fontana 1,100 feet alt.

not to mention u pa guys usualy have better da then us west coast guys.

so 700 ft less alt
21 more hp
and 6.5 mph faster

and all you could do was 1 tenth quicker?

you just furthered my point!

 

[jtfx6552]

you ran a 11.4 @ 122.98 mph thats 6.5 mph faster but u didnt mention that

and cecil dragway is 320 ft alt

he did this at fontana 1,100 feet alt.

not to mention u pa guys usualy have better da then us west coast guys.

so 700 ft less alt
21 more hp
and 6.5 mph faster

and all you could do was 1 tenth quicker?

you just furthered my point!

Couple of things to consider. First, that 11.41 was when I was still in my halfshaft paranoia days, on soft clutch slip, 60 ft wasn't good, If I had launched harder, the ET would have been even better.

But, beyond that, you would rather trap 116, that 122?

That is what hapened at BG when 4.10 cars and 3.55 cars ran side by side, the 4.10 cars were all in the teens, the 3.55 cars in the 120's. So the 4.10 car you mention put up a good et on a prepped track, what happens on the street when you line up a car that traps 122 next to a car that traps 116?

Happened with my friends car, he had 4.10's we busted balls to get an 11.99 @ 119 on Dr's when my car, the same night went 11.70 on F1's, with less mods.

As for the car you are describing, what does it have done to it? You said "stock weight", does that mean IRS? Even if it has IRS, it only has 420 ft lbs of torque. Fits with what I am saying, that a typical pullied chiped Cobra with 500 ft lbs and 3.55's has all the rear wheel torque the stock suspension can handle. 500*2.66*3.55=4721 lb ft, which is actually more than the car you describe, 420*2.66*4.10 is 4580 lb ft. This matches well with what I have said, 3.55's with 500 lb ft is plenty of torque, more than the car you mentioned that pulled the 1.6 60 ft. You didn't take it out to the next decimal point, but I have many 1.6x 60 fts.

Heed the words of Bob Cosby, with traction, which he believes means a straight axle, the "right" shock valving and control arms, which he has figured out after years of racing experience, and shifting like a trained mongoose, he figures to get .15 improvement. Is that a good gain for the $? When racing in a heads up class where the whole field may be seperated by a tenth or two, of course. However, to the average racer, even if they managed to figure out the right control arms, shock valving and suspension set-up, they probably still wouldn't even be consistent enough to tell the difference.

Then consider the typical '03-04 Cobra, the guy with all stock suspension that likes the car to handle well. Will he be able to get enough traction to get any improvement in ET? I doubt it.

 

[jtfx6552]

i went 11.11 on 445rwhp and 4.10s. enough said :thumbsup:

Great run, what was your suspension and tire set up at the time?

 

[jtfx6552]

Or me. 11.43 with 355 rwhp, 4.56 gears. Is that enough said?

I have already said that I agree 100% the n/a Cobras need a very steep gear...

 

[projekZERO]

I have already said that I agree 100% the n/a Cobras need a very steep gear...

his car is stock weight meaning. stock irs everything . he sometimes even leaves the spare in. pretty much as if it were right off the show room.

420 hp.

chip. intake. cat back. pulley, thats it.

no midpipe. no port work. no throttle body

the gears dont hold your mph back.

its in my opinion the gears gears drop your e.t by .2 and change your mph marginaly if not at all.

u cant compare one car and one driver to another.

u need to compare 1 car with same curcumstances. before and after a gear change.

yes gears will leave u with less traction.

that just means you need to adjust to the change.

this guy trapped 119.8 mph at a track with a alt of 200 ft. with the 410's. but the prep was poor at only manages a 11.8

so near 120 mph with 420 rwhp downt sound to me liek the gears are keeping his mph down.

dont forget us socal guys dont have fast tracks like you guys have. and the da makes it even worse.

my local track is 2710 ft. and in the summer da can be around 6000.

try pullin some mph with that!

 

[jtfx6552]

chip. intake. cat back. pulley, thats it.

no midpipe. no port work. no throttle body

I did that all the time, on F1's, mind you.

the gears dont hold your mph back.

its in my opinion the gears gears drop your e.t by .2 and change your mph marginaly if not at all.

u cant compare one car and one driver to another.

u need to compare 1 car with same curcumstances. before and after a gear change.

Did that, buddies car, 4.10's no 11's, switch back to 3.55's mid 11's all the time, went up 4 mph, too.

I am not sure why the 4.10 cars I have seen have trapped poorly, but they did.

yes gears will leave u with less traction.

that just means you need to adjust to the change.

Adjust? Adjust how? leave easier do you don't spin? That means there is power your not using, and your et gets worse.

this guy trapped 119.8 mph at a track with a alt of 200 ft. with the 410's. but the prep was poor at only manages a 11.8

so near 120 mph with 420 rwhp downt sound to me liek the gears are keeping his mph down.

I trapped 120.98 at Bowling Green, not east coast, in high teens da (I forget if it was 1700 or 1900 ft), with 4 mods, pulley chip, catback and CAI, on F1's.

dont forget us socal guys dont have fast tracks like you guys have. and the da makes it even worse.

my local track is 2710 ft. and in the summer da can be around 6000.

try pullin some mph with that!

2710 actual with 6000 da sounds tough. I would suspect that your actual torque with such little air would make gears have a much better chance at doing something positive.

 

[SWEET03COBRA]

damn, almost coming to blows. Hell if people want to raise a "freddy go fast fund", I will do back to back runs with a gear change

 

[projekZERO]

you adjust by getting a better tire.

and i remember the da that day at carlsbad even tho the track is 200 ft the da was 1,600 and he trapped 119.8. so his mph is there for his mods.

if you think gears lower your mph so be it. marc will be back at LACR next weekend.

he trapped 117.8 and 117.9 last time. lets just see how he does this time.

plain and simple gears make the car accelerate faster. but you loose top end.

yes some say you loose mph. but in cases ive experienced this did not happen.

but accelerating faster should mean your e.t. drops.

we will have to wait and see.

we will have moe data next sunday.

 

[11secCobra]

all the 4.10 guys guys trapping in the teens were prob. on 26" tires...i run on 28s, and have no problem trapping 122+ now

edit: stock eaton

 

[kilroy]

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.

~*"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.

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.
~
Bob

• The "gearing your car several hundred rpm above..." is gospel.
• I agree with JT that for 1-2 tenths, the average Joe may spend the mod money elsewhere first

Congrats on the gears Marc, post your new times asap!