First track day with the new car 2017 GTPP

I'll try to give my .02 about the car, even though it's been out long enough that pretty much everyone knows how they do. I'll try to keep it short and sweet, if I ramble on, I'll do a TL;DR at the bottom.

This is going to be a small comparison to my Focus RS that I sold. The Mustang is all stock except for window tint and a shock tower brace (so I can check the oil easier).

I'm group 3 with NASA, so I'm not a super fast or experienced driver, but I'm not quite green either. I've been doing this for a few years in various different cars.

Out at High Plains Raceway on Saturday, temps were pretty cool in the morning and I was happy about oil temps staying in the green, even when it warmed up throughout the day.

The stock Pirelli's were a little surprising, when they are cold, they don't have any bite but when they are warm I'm actually happy with them. The problem is they get hot and greasy pretty fast and become worthless.

The car definitely wants to understeer. It's actually more prone to it than my RS but you can trail brake and kind of toss the car to get it set where you need it to be. It seems like it needs to be driven that way to get a good lap time out of it. I think an alignment and squaring up the tires to a 275 all the way around will be really beneficial to how it drives.

Turn in isn't as good as the RS, I'm not sure I'll ever drive a car as willing to change direction as that car but that's ok. It still feels pretty good.

Tire wear wasn't bad, when the tires got greasy I definitely took some life out of them but after I noticed that, I was much nicer to them and I they didn't wear much more. No chunking or anything and I am no stranger to destroying tires.

The car rolls out pretty well, the long back straight of the track is a good test of the legs of the car, I'm at altitude so the speeds we see are lower than what most other places with a similar setup would see but I was going 125.5 on GPS vs 118 with my Focus RS. My best friend runs a 16 Camaro SS and he was seeing 133, but he also has track brakes, and squared up sticky 275s so he was able to get on the power much sooner and stay in it longer. I think with the same setup I could probably see 129-130 out of the Mustang.

We got the opportunity to run side by side and we drag raced the straights. The cars are a lot more similar in that regard than I expected. He pulls on me, but it's a pretty slow pull.

Brakes are better than I expected for being stock. They would get a teeny bit soft but even with the factory fluid I didn't lose faith in them.

I also had my first 4 off lol. I got too excited on cold tires, normally in 3rd it will dead hook but between hitting a rumble strip and having cold tires the car walked and I caught it for a second but I freaked out and lifted (bad call). That sent me right off. I'll never let that happen again.

I'm happy with this thing. I went over a full second faster in the Mustang than the RS but the sky is the limit with the aftermarket on the Mustangs.

I'll be doing lowering springs, track pads, fluid, CC plates, some IRS stiffening, wheels, tires and some aero. My goal for this car is to run respectable times anywhere I go and be comfortable getting there.

TL;DR (Longer than I thought)
Car is cool, stays cool, understeers but it's faster than I ever went in my RS.

Track in question

I went off in T3, which is probably the most common spot people lose it. I wanted to get a good run for the straight lol.

Actually, I do have a question for anyone that can answer it and I'm wondering if this is a common thing between cars. Coming up T11-T13 in 3rd gear I run out of RPM about 15 feet short of my braking zone in this car. I had an issue once where I hit the limiter and immediately jumped on the brakes. They were rock hard and the ABS kicked in but the car didn't slow down at all. Does hitting the limiter take some of the vacuum out of the brakes? It was almost as if I had glazed the pads (which I have done before) but I knew they weren't glazed as I had them immediately after and I tend to take care of my pads when I'm running. Has anyone else had this problem?

Thanks for reading.

I have a wierd issue sometimes where I go for the brakes and they're soft, but one pump and they're rock hard. I bleed fluid religiously and recently replaced with new pads, so its not pad knockback or old fluid. I've seen it at the track and lots of times at autox. I have no idea what causes it.

Another issue with braking is one time I spun the car pretty good at an autox (in Track mode with T/C full-off with the 6 second hold). So here I am spun around and rolling backwards, and the car would only give me like 40% of the brake pedal for a few moments until finally it release it and gave me 100% brakes. I had the distinct feeling of the brake pedal stopping mid-stroke and then a few moments later releasing and getting full pedal travel. My buddy thought it was a safety feature for people who get sideways and lift.

Other than those two issues and some occasional hot-pad fade on hard-braking tracks I haven't seen any other issues. If someone has a clue what might be going on with #1, which is what it sounds like the OP may be experiencing, I'm all ears. Only think I haven't tried is getting a dealership to pulse the ABS module while bleeding the brakes.

NightmareMoon said:

I have a wierd issue sometimes where I go for the brakes and they're soft, but one pump and they're rock hard. I bleed fluid religiously and recently replaced with new pads, so its not pad knockback or old fluid. I've seen it at the track and lots of times at autox. I have no idea what causes it.

Another issue with braking is one time I spun the car pretty good at an autox (in Track mode with T/C full-off with the 6 second hold). So here I am spun around and rolling backwards, and the car would only give me like 40% of the brake pedal for a few moments until finally it release it and gave me 100% brakes. I had the distinct feeling of the brake pedal stopping mid-stroke and then a few moments later releasing and getting full pedal travel. My buddy thought it was a safety feature for people who get sideways and lift.

Other than those two issues and some occasional hot-pad fade on hard-braking tracks I haven't seen any other issues. If someone has a clue what might be going on with #1, which is what it sounds like the OP may be experiencing, I'm all ears. Only think I haven't tried is getting a dealership to pulse the ABS module while bleeding the brakes.

Click to expand...

I've heard you need to do that on the GT500s before but I could never get anyone to answer whether or not it was needed on my RS. I could never, ever get the air out of them, even when pulling the handbrake a few times while bleeding the rears. I tried traditional bleeds, vacuum, in different orders, nothing ever worked.

I feel like there may be some benefit to it. So far I don't actually need to bleed the brakes on this car, it has enough brake to over use the tires so I am happy for now. I might consider it if I can find another good deal on some RBF or something.

In the Mustang, when I came up on that turn and had the braking problem, I wasn't out of shape in anyway, I'm almost certain none of the nannies stepped in. I feel like I have decent braking modulation to keep the car in check. The only thing I could come up with was hitting the limiter and maybe that created vacuum issues with the booster and that's why the car was freaking out.

I'll try to recreate it again at some point.

Austinj427 said:

The only thing I could come up with was hitting the limiter and maybe that created vacuum issues with the booster and that's why the car was freaking out.

I'll try to recreate it again at some point.

Click to expand...

This is a common issue with the guys who track the cars a lot and are not afraid to use all the RPMs available on the car. What I believe is happening is the VAC assist to the brakes is being used up before a sufficient amount of vac can be generated. I first noticed this when I was getting use to heal/toe downshifting the car while trail braking into a corner. If I was overly aggressive with the rev match the throttle would hang a bit and brakes would be hard as a rock if I had to modulate on and off the bakes going into the corner. It happened twice and that was enough for me to adjust my habits and limit the effect. I now make sure that the car is in the needed gear prior to corner turn in and my brake pedal is never completely lifted off of while downshifting. I believe that lifting completely off the bake pedal then reapplying the pedal while the throttle is open is what is causing the loss of vac signal to the booster.

To help limit the effect I have my car tuned to a higher redline so that I do not hit the limiter, but care must be taken not to over rev the car. I have mine set at 7800rpm and try and shift at 7500 or less. The limiter on the car will do a combination of ignition cut and fuel cut to limit RPM. The ECU decides what method and how aggressive to apply that method based on how the engine is accelerating to the redline. The limiter also has an effect on throttle position but since that would be the slowest method to control a overrun I believe it is acted upon after the fuel cut and ignition cut are applied.

One of the things that happens with the OEM tune is the throttle will hang open at higher RPMs, you can try this by doing a 2nd gear run to redline and just before you would hit the limiter lift off the gas pedal and throw in the clutch as fast as you can. You will notice the car will hold RPMs for a brief time then start to fall towards idle. Its this holding open of the throttle that limits the available vac source for the brakes. If the throttle is open your vac source is gone. Ford tries to limit the effect on a GT by using a vac venturi just before the brake booster connection at the intake manifold. Ironically on the GT350 this vac venturi is not used and the brake booster is connected to a large 5/8" port directly into the manifold. This hanging throttle is actually even more pronounced when you hit the limiter but it is still there even when you do not hit the limiter.

The simplest solution for this problem is to fix the tune to not hold the throttle open but I am not sure this can be done as FORD may have this buried in a place that the average tuner may not be able to access. DBW tuning is not the easiest thing to tune as there are many things that contribute to the final throttle control and the drivers throttle input is only one of them.

The other possible solution and the one I am going to try is to add another vac canister and check valve in front of the brake booster, then remove the vac venturi so there is a larger reservoir of stored vac signal for the brake booster to access. In theory this will work but I have not tried it yet so I will have to see if adding one will help. I am hoping that by adding a larger reserve of VAC signal and a 2nd check valve that I can return to completing my braking and downshifts as I am entering the corner instead of having to get everything done prior to turn in. Right now downshifting and trail braking together are not an option.

Dave

I've experienced this in both hpde and autocross and always in the scenarios provided above (on throttle at or close to limiter to full brake). Look forward to your experiment [MENTION=20846]ddozier[/MENTION].

Austinj427 said:

I'll be doing lowering springs, track pads, fluid, CC plates, some IRS stiffening, wheels, tires and some aero. My goal for this car is to run respectable times anywhere I go and be comfortable getting there.


I went off in T3, which is probably the most common spot people lose it. I wanted to get a good run for the straight lol.

Actually, I do have a question for anyone that can answer it and I'm wondering if this is a common thing between cars. Coming up T11-T13 in 3rd gear I run out of RPM about 15 feet short of my braking zone in this car.

Click to expand...

Let me suggest picking springs based on rates rather than the amount lowered. Plan on dampers better suited to those rates and using adjustable sta-bars to re-balance the car to best suit you.

New tires may well be a bit shorter, which with hopefully higher cornering speeds will have you shifting in different places and potentially more often. Your T11-T13 problem could easily become a gotta-downshift-from-4th situation instead.


Norm

Norm Peterson said:

Let me suggest picking springs based on rates rather than the amount lowered. Plan on dampers better suited to those rates and using adjustable sta-bars to re-balance the car to best suit you.

New tires may well be a bit shorter, which with hopefully higher cornering speeds will have you shifting in different places and potentially more often. Your T11-T13 problem could easily become a gotta-downshift-from-4th situation instead.


Norm

Click to expand...

I went with the minimal drop springs more for the look. My RS had a pretty firm ride and after a weekend of track driving and a long haul home, it would piss me off pretty bad. I really want a car that is as friendly to drive on the street as this one is stock, but can throw down some decent times. I believe it will. I'm not doing an all out build.

And yeah I ended up short shifting at like 6300 into 4th in that turn but I'm back down to 3rd just a split second later. Shorter tires will force me into 4th but I think taking away the option of third will mitigate my issue.