5-6 shift at WOT- will it?

[wreckwriter]

These are from a stock G8 tune. Appears to me it will never shift from 5 to 6 at anything over 75% throttle. Am I missing something?

[norm8332]

No you are not missing anything. According to the tune it will not shift into 6th at WOT. You can go into 6th in manual of course.

[p71]

Why would you want to be in 6th at WOT?

If you are in sixth and you go o WOT it is going to kick down... (I know you know that)

And unless I am getting my facts crossed you get better acceleration and top speed in 5th so there is no reason to go to 6th.

[wreckwriter]

Interesting. Safety feature for a weak overdrive gear or just to keep folks from going stupid fast I wonder.

[Robert@KBXPerformance]

Interesting. Safety feature for a weak overdrive gear or just to keep folks from going stupid fast I wonder.


Stupid fast and also that puts allot of load on the engine too. Allot of engines are blown due to people doing long stretches of top speed pulls in the higher gears. Recipe for disaster in most cars.

[wreckwriter]

Stupid fast and also that puts allot of load on the engine too. Allot of engines are blown due to people doing long stretches of top speed pulls in the higher gears. Recipe for disaster in most cars.

Seems shifting to 6th would be less stressful than just running 5th up to the top, no?

[wreckwriter]

Why would you want to be in 6th at WOT?

If you are in sixth and you go o WOT it is going to kick down... (I know you know that)

And unless I am getting my facts crossed you get better acceleration and top speed in 5th so there is no reason to go to 6th.

You wouldn't under normal circumstances. I'll never go fast enough to need it but trying to figure out why its that way. I guess someone somewhere might use it....

[p71]

There is no need for it.

I am willing to bet on a stock car the mechanical advantage gained by running in fifth instead of sixth will push the car to a higher maximum speed. I would bet that stock the car will do close to 170 in fifth, but will only do high 150s in sixth, even if you tune your tcm to hold those gears.

I know stock corvettes max out in fifth, because they do not have enough torque to turn the steeper gear at that speed... I figure we are probably the same or worse.

Think of it this way... if you are in granny gear on a bike you can go up a steep hill at about 7 mph... if you put it into the opposite gear your legs do not produce enough torque to even hold yourself on the hill and you will roll backwards and hurt yourself.

Same deal here... the added friction with the wind and road at high speed is equivalent to the load placed on you by the hill. You can get up to your max speed in a lower gear in both cases.

[norm8332]

I floored it in 6th before (manual mode) and it took the TQ (around 455rwtq) at 3000 rpms. So it didn't break at that level.

I guess if you have a heavily modified car and want to exceed 178 MPH then you could just use manual mode. Make sure your tires can take it!:)

[p71]

It is not a matter of breaking stuff... it is a matter of it not being needed advantageous or useful.

unless you are putting down about double what the car puts down stock you are not going to run into the rev limiter in fifth ever, so you will not need sixth.

[norm8332]

It is not a matter of breaking stuff... it is a matter of it not being needed advantageous or useful.

unless you are putting down about double what the car puts down stock you are not going to run into the rev limiter in fifth ever, so you will not need sixth.


Well I know a GXP went 178 with only 415 at the crank and being that on a GT that would equate to 6500 RPMs in 5th I disagree about the double power part.

[p71]

fair enough, I miss worded that... if you were in sixth I am betting you do not get to 178...

[norm8332]

fair enough, I miss worded that... if you were in sixth I am betting you do not get to 178...

It wasn't me. I'm not crazy.:wacko: So I won't be finding out myself anytime soon.

There is a guy (Intense i believe) that is trying to get his G8 to a 9.99 1/4 time and over 200mph top speed but he will have double the power.

[Blackdevil77]

There is no need for it.

I am willing to bet on a stock car the mechanical advantage gained by running in fifth instead of sixth will push the car to a higher maximum speed. I would bet that stock the car will do close to 170 in fifth, but will only do high 150s in sixth, even if you tune your tcm to hold those gears.

I know stock corvettes max out in fifth, because they do not have enough torque to turn the steeper gear at that speed... I figure we are probably the same or worse.

Think of it this way... if you are in granny gear on a bike you can go up a steep hill at about 7 mph... if you put it into the opposite gear your legs do not produce enough torque to even hold yourself on the hill and you will roll backwards and hurt yourself.

Same deal here... the added friction with the wind and road at high speed is equivalent to the load placed on you by the hill. You can get up to your max speed in a lower gear in both cases.

Fantastic analogy and I see what your saying and it does make sense. 6th gear is basically to save gas during highway cruising. Nothing more.

[13 QTR]

So...wreak...you saying you tried to get it to shift into 6th at wot..and it wont?? I've almost got there...I just want see how hard it shifts into 6th at wot. with the 3.27's that's only about 175...I'm shifting at 6150. I've been to 168 and it was still pulling good...just the traffic wouldn't let me continue the run.

[Robert@KBXPerformance]

Seems shifting to 6th would be less stressful than just running 5th up to the top, no?



Nope, it would be more stressful because there is more load being placed on the engine due to it now having less mechanical advantage (as was stated earlier). Kind of like starting a car out in 4th gear instead of 1st gear. In 4th gear you will be loading the engine way too much if you are really trying to accelerate. Now that is an extreme example but it will assist in putting things into an easier to understand perspective when thinking of the differences between top speed runs in 5th and 6th gear. Bottom line is go to the maximum safe rpm that you can in each gear. If the car is still accelerating then shift to the next gear and proceed from there. Not many have to worry about this though. I know I only plan to trap 130-140mph when my car is all said and done so I don't need much more than that for any sort of top speed. :)

[Mike P]

Well I know a GXP went 178 with only 415 at the crank and being that on a GT that would equate to 6500 RPMs in 5th I disagree about the double power part.


Norm:

Whoa! Who is the GXP owner that went 178mph? That' haullin' balls!


...

[norm8332]

Norm:

Whoa! Who is the GXP owner that went 178mph? That' haullin' balls!


...

Read the last paragraph of the first post and check the pictures.:) Here:
http://forum.grrrr8.net/showthread.php?t=4016&highlight=gps+track

[Mike P]

Thanks Norm....

Wow, I would love to run my car at Bristol or MIS in Brooklyn, MI

[wreckwriter]

So...wreak...you saying you tried to get it to shift into 6th at wot..and it wont?? I've almost got there...I just want see how hard it shifts into 6th at wot. with the 3.27's that's only about 175...I'm shifting at 6150. I've been to 168 and it was still pulling good...just the traffic wouldn't let me continue the run.

Nope, have not tried, just looking at the table and seeing that its set to not do so. Wondering why.

[13 QTR]

Nope, have not tried, just looking at the table and seeing that its set to not do so. Wondering why.

Damn....I hope the vms tune took that out. Cause one day...the traffic will be clear and I'm gonna try. I'd hate to hold it on the rev limiter at
170+,waiting on it to shift.

[wreckwriter]

New thread on this topic:

http://forum.grrrr8.net/showthread.php?p=132697#post132697