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Discussion Starter · #1 ·
Hi,

The TH starts to lack in the 90mph and above when starting from the line. I have raced many of the newer bmw X competitions, Urus and Cayenne’s. Off the line the TH is a beast but at around 90-100mph the competition starts to catch up.
At that speed aerodynamics should not be the issue, it feels like the TH doesn’t get enough air or the supercharger is limiting the airflow. We have at least 40hp and 74ft/lb of torque more than the rest, but for some reason they just pull a lot better.
The strange thing is that, when sitting next to eachother at around 100mph, the TH is the first to pull but than quickly falls behind.
Anyone with any reasoning to this behavior?
 

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Hi,

The TH starts to lack in the 90mph and above when starting from the line. I have raced many of the newer bmw X competitions, Urus and Cayenne’s. Off the line the TH is a beast but at around 90-100mph the competition starts to catch up.
At that speed aerodynamics should not be the issue, it feels like the TH doesn’t get enough air or the supercharger is limiting the airflow. We have at least 40hp and 74ft/lb of torque more than the rest, but for some reason they just pull a lot better.
The strange thing is that, when sitting next to eachother at around 100mph, the TH is the first to pull but than quickly falls behind.
Anyone with any reasoning to this behavior?
Awd falls on its face up top and the th a brick don’t make it no better ! Them other vehicles got sleek lines etc lol
 

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Discussion Starter · #3 ·
Well they all have awd, we can at least control ours in trackmode. Below is a comparison of drag and weight. I still don’t see why the TH falls behind having the most power.

Drag coefficient:
Trackhawk:0.371
Urus: 0.34
Cayenne GT: 0.37
X5m Comp: 0.38
X6m Comp: 0.37

Weight:
Trackhawk: 2,433 kg (5,364 lb)
Urus: 2,197 kg (4,844 lb)
Cayenne GT: 2.295 kg(5,059 lb)
X5m Comp: 2366-2370 kg (5216-5225 lbs)
X6m Comp: 2,363kg (5,209 lb)
 

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I think others got Turbos, which pulls at the top end, slick lines, more air dynamic and most of the power at the top RPM. Trackhawk is the TORQUE monster, top end is not it's thing, but it does hold its own.
 

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I also wonder if there could be a less than optimal gearing in the transmission at the higher speed range.
 

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Probably not, I mean top speed of Trackhawk is what 180-190. I think it's the way it delivers the power.
There are a lot of gear changes to get to 180.
Given 1/4 trap speeds are a little over 100, gear ranges can have an effect at different speeds and shift points.. for example, too tall of a fourth gear could drop you out of the power band for awhile, yet top speed can still be hit.
 

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There are a lot of gear changes to get to 180.
Given 1/4 trap speeds are a little over 100, gear ranges can have an effect at different speeds and shift points.. for example, too tall of a fourth gear could drop you out of the power band for awhile, yet top speed can still be hit.
It's part of it, true, but I don't think its the main factor.
 

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Discussion Starter · #11 ·
You can eliminate all this by doing Stage 1 or 2 upgrade. Problem solved.
At the same time the others can do stage 1 or 2 also. The torque should help us push harder and faster than the others.
I am wondering how much the others transfer power to the rear only disengaging the front.
 

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Discussion Starter · #12 ·
Track hawkPorsche GTUrusX5/6M Comp
1st4.714.714.715.00
2nd3.143.143.143.20
3rd2.112.112.112.14
4th1.671.671.671.72
5th1.291.291.281.31
6th1.001.001.001.00
7th0.84.840.840.82
8th0.670.670.670.64
9th
Reverse3.303.323.323.48
Final3.702.953.093.15
Max rpm6200rpm6800rpm6800rpm7250rpm
 

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At the same time the others can do stage 1 or 2 also. The torque should help us push harder and faster than the others.
I am wondering how much the others transfer power to the rear only disengaging the front.
I wondered the same. The 4wd gets you moving quicker (more traction)but probably hurts once you are moving.
 

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So, the TH, GT and Urus have the exact same gear ratios???? You sure?

Yes, I see the final drives are different.

How does the TH's ratios compare to the GC SRT?
 

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Discussion Starter · #15 ·
So, the TH, GT and Urus have the exact same gear ratios???? You sure?

Yes, I see the final drives are different.

How does the TH's ratios compare to the GC SRT?
I got all the numbers from their websites. I am guessing that the ZF 8speed is used all variants. It is a popular transmission.
 

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Discussion Starter · #17 · (Edited)
Trackhawk: ZF 8HP95
Urus: ZF 8HP(the rs q8 has ZF 8HP90)
GT: 8speed PDK
X5/6m Comp: ZF8speed( 8HP90 or 95)

The only outcast is the Porsche Cayenne GT with inhouse PDK gearbox. Probably the fastest shifting gearbox of the bunch.
The Urus might have the 8HP95 since it is the 2nd gen of the 8HP90
 

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Discussion Starter · #18 ·
Yes I know, i have become [email protected] about this, but I really want an answer as to why we lose momentum after 90-100mph. Specially when all the SUV’s seem similar.
The latest drag race on youtube channel CarWow really shows how far behind we get in a longer run.

 

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Interesting video shoot-out. And fun to watch. But...

As a magazine performance test driver/racer for 25+ years, if it were my test, I'd have pointed out that having five different drivers opens up huge variables in terms of driving talent.

The Jeep driver pretty much was slowest to react, on each test. The instant torque of the TH engine is what had the TH moving out quickly. Not the driver being exactly on-time with the others.

And the "ready, set, go" type of testing also is full of driver variables.

Also, going by the speedometer to register top speed, in any test, is ridiculous. Porsches and BMWs are notoriously optimistic at high speeds. Often 5+ mph optimistic.

It's a cool comparison to watch. The Jeep and Lambo definitely run out of steam as the speeds climb, but that's about all you can take away from this.

Instrumented testing, with one top-quality driver.
The same guy/gal helming each vehicle, one at a time, for 3 to 5 runs (or more if it's a tricky car to launch.)
This the only way to get accurate numbers that give a true comparison.

So...what's holding the Jeep back in higher speeds? I'd have though aero, but that chart posted above in this thread shows (if accurate) that the Jeep has similar aero to the rest. However...coefficient of drag is calculated mostly by frontal area. Not (AFAIK) in actual driving. Wind tunnels are okay, but they won't show the amount of high speed aero lift on a vehicle. Perhaps this is plaguing the Jeep more than the others...thus creating more drag...and the slower accel.

Thoughts?
 
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