High speed pulls question???

[dormeas]

Okay I don't know if this has been thought over but....

I was wondering how many of the 03/04 Cobras, that fail because of WOT in 5th and 6th gear, have been professionally tuned by a reputable tuner?

Could be none could be all, hell I don't know I just find it odd that our cars would be incapable of doing 160+ runs without breaking. There are videos all over the internet of Cobras doing 0 - 160 over and over.

My friend who had an 02 Z06 used to go 0 - 170 - 0 like 6 times in a row on any given night just for fun..... Are they that superior in build quality?

^^^Also the above is just an example of what a Z06 is capable of, and I know its dangerous and stupid and ignorant and all that so "save it" with the dad talks.

 

[thomas91169]

two things are going on.

1) 5th and 6th gears are Overdriven, which puts alot more strain and load on the motor, which gets enough strain as it is from the blower.

2) Our motors are designed with tight PTW (piston to wall) clearance, and just "eh" pistons.


The main issue is when you hit 5th, you have already been WOT for quite some time, so your motor is already heated. Lets not forget the Eaton isnt exactly the epitome of efficiency, and the heat exchanging system can only pull out so much heat. So after being in the throttle for a easy 30 seconds, you are now hitting your OD gear. Load on the motor is increased by XX%, which just pours on the heat. Heat causes piston to expand into a cavity it doesn't have room for, piston meets wall, you are now on the path to a rebuild. Not to mention your tuner doesnt compensate for a 5th gear pull, if he did, you would get maybe 15* of timing and you would have a 10.5:1 AFR to keep cylinder temperatures and pressures down. Most tuners, unless you specify, will assume you arent retarded and will give up if you havent won by the end of 4th.

Cooling mods help the situation but you are talking about Russian Roulette when hitting 5th gear and still laying into it. The best flowing coolant couldnt keep the cylinders cool enough under these extremes to keep the pistons from making out with your cylinder walls.

The ultimate way to have a motor withstand the stresses of boost and the heat involved with a roots/twin screw boost source, and to live at those conditions is to build it properly. This means forged and coated pistons that better withstand heat and dont expand, proper PTW clearance to compensate for piston expansion, etc.

You have to remember too, a ZO6 isnt a 3600lb pig with just marginally better than stock mustang aerodynamics, its also naturally aspirated (less heat and combustion pressures) with slightly better gearing. The stresses on the motor arent multiplied when it hits its OD gears as much as they are when ours hit the OD gears. SVT never tested the 03/04 motor at OD loading during WOT because thats not what the OD gears are even designed to do.

 

[dormeas]

Good info there and I appreciate it. Just seems like there could be more to it. Maybe not...:shrug: Thanks

 

[Fastlane Cobra]

Its been explained quite often. It sucks because some of us can drive top speed all day long. In the early years as my car was under warranty I was also often driving 150 plus. But after all of the damaged motors from top speed pulls I have read about I take it easy. I am a little disappointed that after 4 gears you have to slow down or risk motor damage. On the autobahn many cars with only 200hp can outrun the highly regarded 03 cobra from city to city.

I was so close to getting the new M3 because I hate excuses, shortcuts, and products that always need second guessing. The M3 seems to have gotten it right. But I held off and decided to keep the cobra. Even with all the issues I still like this car. This top speed issue still bothers me.

 

[04RiceEater]

My car was tuned by RWTD. Did a few top end runs and melted a huge hole in the piston. So its not who tunes it,its just matters if the person driving is retarded or not. (LOL)

 

[dormeas]

I was so close to getting the new M3 because I hate excuses, shortcuts, and products that always need second guessing. The M3 seems to have gotten it right. But I held off and decided to keep the cobra. Even with all the issues I still like this car. This top speed issue still bothers me.

I am dangerously close to selling my Cobra and buying a c5 z06 and being done with it.:shrug:

 

[DREAMCOMETRUE]

The rebuilt of my Cobra will be done the 2nd week of January because of a 5th WOT my 1st and last one believe me!!!! I just had the estimate for the rebuilt $$$$$$ EXPENSIVE:fm: My fault no one to blame but me. Since i blew my motor there is a thread like this one that comes out each week, and someone reply by saying they did not know about the 5th and 6th gear WOT. Lets see on this thread if we have another one. I say again this subject should become a STICKY!!!!!!!!! It would save lots of motor,money,and stress,and the wife going crazy lol

 

[Black Talon]

I have done 5th gear runs. If you do not do back to back runs and your car is tuned right you will be fine. Many have done top end pulls and been fine, but many have melted a piston. It is always in mind when high end racing, I wouldn't make a habit of it.
6th gear is asking for trouble.

 

[03cobra#694]

^^^^^What he said,heat build up is our enemy!

 

[CobraBob]

Two things are going on.

1) 5th and 6th gears are over-driven, which puts a lot more strain and load on the motor, which gets enough strain as it is from the blower.

2) Our motors are designed with tight PTW (piston to wall) clearance, and just "eh" pistons.

The main issue is when you hit 5th, you have already been WOT for quite some time, so your motor is already heated. Lets not forget the Eaton isnt exactly the epitome of efficiency, and the heat exchanging system can only pull out so much heat. So after being in the throttle for a easy 30 seconds, you are now hitting your OD gear. Load on the motor is increased by XX%, which just pours on the heat. Heat causes piston to expand into a cavity it doesn't have room for, piston meets wall, you are now on the path to a rebuild. Not to mention your tuner doesn't compensate for a 5th gear pull, if he did, you would get maybe 15* of timing and you would have a 10.5:1 AFR to keep cylinder temperatures and pressures down. Most tuners, unless you specify, will assume you aren't retarded and will give up if you havent won by the end of 4th.

Cooling mods help the situation but you are talking about Russian Roulette when hitting 5th gear and still laying into it. The best flowing coolant couldnt keep the cylinders cool enough under these extremes to keep the pistons from making out with your cylinder walls.

The ultimate way to have a motor withstand the stresses of boost and the heat involved with a roots/twin screw boost source, and to live at those conditions is to build it properly. This means forged and coated pistons that better withstand heat and don't expand, proper PTW clearance to compensate for piston expansion, etc.

You have to remember too, a ZO6 isn't a 3600lb pig with just marginally better than stock mustang aerodynamics, its also naturally aspirated (less heat and combustion pressures) with slightly better gearing. The stresses on the motor aren't multiplied when it hits its OD gears as much as they are when ours hit the OD gears. SVT never tested the 03/04 motor at OD loading during WOT because thats not what the OD gears are even designed to do.

Very good comments my friend! :thumbsup:

Here is a question I've always had. Why do a WOT pull to 160 in the first place? I would think your 1/4 mile trap speed would be more than sufficient if you're looking for an adrenalin rush. I just don't understand why people risk their motor when they know pulls to 160ish is a known potential issue with these motors. Because the end result can be very expensive. :shrug:

 

[Jomo1994z71]

1st-4th only for me...

 

[SM0KE]

1st-4th only for me...

+1

 

[03 TOPLESSSVT]

+2

 

[SonicDTR]

It really has nothing to do with the gear its in, its all about the load and heat placed on the engine.

For example, if you somehow had a trailer on your cobra and all you could muster was 70mph WOT in 3rd gear, the same issues would occur. It just so happens that 5th and 6th put that much stress on the engines.

As for being beaten city to city on the autobahn, I dont think that would be true at all. You can cruise at 150mph without being WOT while doing it....actually when you let off going that speed the engine would probably cool off very quickly due to airflow.

 

[Smacked_in_ATL]

Definitely 1st-4th WOT only. I only boost in 5th on the interstate to pass, from a cruise....and that is rare. Never in 6th.

 

[ReCoil]

Just rig up a setup that fogs liquid nitrogen into the radiator..

 

[AaronK]

I was so close to getting the new M3 because I hate excuses, shortcuts, and products that always need second guessing. The M3 seems to have gotten it right. But I held off and decided to keep the cobra. Even with all the issues I still like this car. This top speed issue still bothers me.

I am dangerously close to selling my Cobra and buying a c5 z06 and being done with it.:shrug:

M3s and C5Zs are not without flaws and disadvantages.

two things are going on.

1) 5th and 6th gears are Overdriven, which puts alot more strain and load on the motor, which gets enough strain as it is from the blower.

2) Our motors are designed with tight PTW (piston to wall) clearance, and just "eh" pistons.


The main issue is when you hit 5th, you have already been WOT for quite some time, so your motor is already heated. Lets not forget the Eaton isnt exactly the epitome of efficiency, and the heat exchanging system can only pull out so much heat. So after being in the throttle for a easy 30 seconds, you are now hitting your OD gear. Load on the motor is increased by XX%, which just pours on the heat. Heat causes piston to expand into a cavity it doesn't have room for, piston meets wall, you are now on the path to a rebuild. Not to mention your tuner doesnt compensate for a 5th gear pull, if he did, you would get maybe 15* of timing and you would have a 10.5:1 AFR to keep cylinder temperatures and pressures down. Most tuners, unless you specify, will assume you arent retarded and will give up if you havent won by the end of 4th.

Cooling mods help the situation but you are talking about Russian Roulette when hitting 5th gear and still laying into it. The best flowing coolant couldnt keep the cylinders cool enough under these extremes to keep the pistons from making out with your cylinder walls.

The ultimate way to have a motor withstand the stresses of boost and the heat involved with a roots/twin screw boost source, and to live at those conditions is to build it properly. This means forged and coated pistons that better withstand heat and dont expand, proper PTW clearance to compensate for piston expansion, etc.

You have to remember too, a ZO6 isnt a 3600lb pig with just marginally better than stock mustang aerodynamics, its also naturally aspirated (less heat and combustion pressures) with slightly better gearing. The stresses on the motor arent multiplied when it hits its OD gears as much as they are when ours hit the OD gears. SVT never tested the 03/04 motor at OD loading during WOT because thats not what the OD gears are even designed to do.

One of the best posts I've seen.

Normally, before a run, I'll tell whoever I'm racing that I'm only going to the top of 4th which is about 120ish. I do this so there isn't any accusing going on (this happens often when I run Z06s, they always want to race until they run out of road :nonono

 

[SLEEPERSTATUS]

two things are going on.

1) 5th and 6th gears are Overdriven, which puts alot more strain and load on the motor, which gets enough strain as it is from the blower.

2) Our motors are designed with tight PTW (piston to wall) clearance, and just "eh" pistons.


The main issue is when you hit 5th, you have already been WOT for quite some time, so your motor is already heated. Lets not forget the Eaton isnt exactly the epitome of efficiency, and the heat exchanging system can only pull out so much heat. So after being in the throttle for a easy 30 seconds, you are now hitting your OD gear. Load on the motor is increased by XX%, which just pours on the heat. Heat causes piston to expand into a cavity it doesn't have room for, piston meets wall, you are now on the path to a rebuild. Not to mention your tuner doesnt compensate for a 5th gear pull, if he did, you would get maybe 15* of timing and you would have a 10.5:1 AFR to keep cylinder temperatures and pressures down. Most tuners, unless you specify, will assume you arent retarded and will give up if you havent won by the end of 4th.

Cooling mods help the situation but you are talking about Russian Roulette when hitting 5th gear and still laying into it. The best flowing coolant couldnt keep the cylinders cool enough under these extremes to keep the pistons from making out with your cylinder walls.

The ultimate way to have a motor withstand the stresses of boost and the heat involved with a roots/twin screw boost source, and to live at those conditions is to build it properly. This means forged and coated pistons that better withstand heat and dont expand, proper PTW clearance to compensate for piston expansion, etc.

You have to remember too, a ZO6 isnt a 3600lb pig with just marginally better than stock mustang aerodynamics, its also naturally aspirated (less heat and combustion pressures) with slightly better gearing. The stresses on the motor arent multiplied when it hits its OD gears as much as they are when ours hit the OD gears. SVT never tested the 03/04 motor at OD loading during WOT because thats not what the OD gears are even designed to do.

impressive answers bro:rockon:

 

[thomas91169]

Its been explained quite often. It sucks because some of us can drive top speed all day long. In the early years as my car was under warranty I was also often driving 150 plus. But after all of the damaged motors from top speed pulls I have read about I take it easy. I am a little disappointed that after 4 gears you have to slow down or risk motor damage. On the autobahn many cars with only 200hp can outrun the highly regarded 03 cobra from city to city.

Actually autobahn wouldnt phase the cobra in 5th and 6th gears at high speeds if you are just cruising. Its being WOT that matters. If you could somehow be light on the throttle, hell 150-160 is do-able. Dunno if id trust a mustang at those speeds for long term cruising though.

I was so close to getting the new M3 because I hate excuses, shortcuts, and products that always need second guessing. The M3 seems to have gotten it right. But I held off and decided to keep the cobra. Even with all the issues I still like this car. This top speed issue still bothers me.

there were no shortcuts in the production of the 03/04 Cobra, if you are curious, read Iron Fist, Lead Foot. The issue was the car just flat out isnt designed for WOT in 5th and 6th gears, especially being already WOT for 2nd-4th. Its not much an issue with naturally aspirated cars, but the heat induced with forced induction, and especially a inefficient roots blower, is just too much when being under those loads for those periods of time. I cant think of really any forced fed cars that are designed to be WOT in their OD gears, someone might bring up the heralded Supra but the ones that are, are big turbo BPU++++ whatever, which are way more efficient at making boost than a heaton thats blowing fire at 15psi, or even any Twin Screws.

 

[c6zhombre]

Here is a question I've always had. Why do a WOT pull to 160 in the first place? I would think your 1/4 mile trap speed would be more than sufficient if you're looking for an adrenalin rush. I just don't understand why people risk their motor when they know pulls to 160ish is a known potential issue with these motors. Because the end result can be very expensive. :shrug:

I agree. I find a hard enough time finding a spot to redline 3rd and make a WOT shift to 4th. Can't imagine too many places a 5th and 6th gear pull can even be accomplished, other than a HUGE closed off course or in germany on the autobahn.

I'm not one of those "don't ever race" in public kind of people...on the contrary, I have some fun. It's all 1-3 fun. 135+ speeds is just stupid on a public road :shrug: