Delurker

I volunteer. All I need is a car, some slicks, and a nearby track. Some skill would probably also be helpful.

betrezra

I bet to put decent slicks you'll need to put some C300 rear brakes to fit a 16" wheel.......
A 2nd set of wheels with d/r's will help .

betrezra

https://mbworld.org/forums/amg-gt-gt...00hp-gt-s.html



Rt st 2----700hp


This is getting interesting gents.

Merc63

Mph is a high 11s time with traction. Not bad for a bone stock car.

JPMBenz

What do you mean?? Haha

betrezra

A "FEW" backseat drivers

Will617

Good job JP and thanks for sharing. I'm sure you definitely left some on the table with the 12.5 but I must say that the MPH for that time is impressive.

PeterUbers

Slicks....

JPMBenz

LOL I'll be nice and just agree with what your saying.

PetroC63

Nice. That 119 mph trap is very healthy especially in the heat. This car is screaming for a set of drag radials. lol

You should try again in October. I bet you pick up another 1 to 2 mph from the temperature change alone.

For comparison sake my stock CTS-V ran 12.1 @ 119 with a 2.0 60' in October at Atco.

JPMBenz

My friend has a CTS V Coupe on street tires, with mods, ran 11.2 at 127.

JPMBenz

Right lane here.


Ran again last night. Here are the things I changed:

1) 1/4 tank of fuel. Last time I had a full tank

2) Adjusted my seat to be slightly further back; created more leg room so a easier push on the throttle.

3) Tires were at 20 PSI down from 22.

4) Temp at the track was 75.

5) Traction control was 100% off.

60' was much higher then the first runs. I tried using LC but the tires in 3rd broke and the ESP in Sport kicked in. Hence, why that wasn't the faster run.

betrezra

Contrasting with the tuned C63s run of AMGTTV8 you have high 1/8 mile MPH.... YET lower 1/4 MILE MPH..... must be his tune.

THanks for sharing. I can't wait to get my 1/4 mile run in..... it's 104degF here now..... so no rush on this end.

Will617

Wow 12.1 is very good JP, kudos bigtime .
It's amazing to see you run 4/10 quicker but you are 3 MPH slower but as you said the ESP interfered and robbed you. It shows us that there is still some left on the table. I'm sure you are aware of this as well and must be eager to run again. With some practice I believe high 11's and in the 120's should be possible. As always, thanks for sharing.

JPMBenz

Actually it works the opposite....the faster the 60' foot the quicker you will get down the track with a lower speed. The speed decreases along the the time. Does that make sense? I feel, all everything working right, 11.8 at 116 is what the car will run. The car truly needs to be driven with the ESP off to gain the full use of the 1/4 mile.

msd3075

The need to lower your tire pressure that low doesn't apply to modern-day, low profile street tires.

There are two main reasons why you would significantly lower your pressures:

- To increase your contact patch size. Pounds per square inch (psi) --> lower pressure means you need more square inches (larger contact patch) to support the same weight of the car.
- To allow the sidewall of the tire to more easily flex to 'soften' the shock caused by the launch.

The short sidewall on street tires isn't going to flex at all under longitudinal stress. Not going to happen by a long shot.

As for the contact patch, with the stiff sidewall of modern street tires you can only increase the contact patch so much before you begin to deform that contact patch and make for uneven contact with the road (i.e. the middle of the patch basically folds under and the edges of the patch take most of the stress). If the gas-door pressures say the rear should be 33 psi, I wouldn't go much below 28ish on the dragstrip. Anything lower is counterproductive.

When you enter into the world of drag radials and slicks, the old-school rules still very much apply.

Also, another thing I wanted to make sure of is that you aren't driving through the water box and doing a burnout. The only reason to do a burnout in street tires is to clean them off, but if you just avoid driving through debris you shouldn't have a problem. The little amount of heat you might put into street tires won't make a difference, and if anything you'll end up with trace amount of water in the tread that'll greatly affect traction.

TTA850

This is a misconception that many people have

http://www.w8ji.com/tire_spin_and_mph_myth.htm

Will617

I think I need a math major to fully understand lol.
I've just learned from experience running the 1/4 mile that when it hooks up my ET as well as the MPH would be better. The first and foremost important part is for it to get traction of the line.

msd3075

It's easier to think about it this way.

The more traction you have, the more power you will be able to put to the ground. More power means quicker ET and higher trap speed than with less power. Therefore, everything else held constant other than traction, a car with more traction will have a quicker ET and higher trap speed.

If all you are doing is essentially making you car more powerful by being able to use more of that power, how could it be slower?

betrezra

If you have a low ET, but low trap speed.... that is high tq.... and falling on it's face on the top end....... or traction issues on the top end (n/l for this car).... or letting off on the top end.

Or if it's an aero dynamic problem...... brick truck type vehical...... falls on it's face up top....... low MPH........

data-logging will unlock some of this mystery.

msd3075

Low ET with low trap speed can also be the result of light weight and (relative) low power. Think of something like the Lotus Elise. You have similar power/weight ratio as a heavier, more powerful car, but you have a significantly worse power/drag ratio.

Falls under the same principle as your "brick type truck". Drag kills the top-end performance for both but for different reasons.

betrezra

My guess is Heat Soak at top end of 1/4 Mile in summer months, pulling back timing, killing power.

JPMBenz

Going again on Wednesday...LOL

msd3075

That's my assumption too.

Too bad it won't cool off around here until Thanksgiving time......

RDOCA

You really think so?? 12 sec.
What happens with a 20 min. track session pushing hard?