Summer performance?

[Lethalchem]

Temps have been in the high 80's to mid/low 90's here lately (which is actually a cool year, to be honest). I've been a little curious about the car's performance lately so I thought I'd ask what other guys in similar temps are experiencing. I was driving home this afternoon (temp 88) and dropped the car into 2nd gear at 40mph and punched it. Car was in Sport mode and I got no wheelspin. Not even a hint of it. I expected a little kick out before it tucked in (like it did when it was cold out here).

This reminded me of a 1st gear rolling punch I did with my brother-in-law in the car and it had almost no spin then either. I'm on stock factory tires and I know they stick better when warm but I'm surprised by the lack spin in both these scenarios. The car seems "soft" on the hit and then builds power after it gets higher in the revs, which is not the way positive displacement blowers typically work.

I would chalk this up to the TC interfering and pulling throttle AFTER detecting significant wheel spin (like it did during the colder months) but I'm not getting the wheel spin first. Is anyone else getting this kind of traction in hotter temps or do I need to make sure my car is making the power it's supposed to be? Everyone talks about how much of a "beast" this car is and I've always felt differently about it. All intercooler plugs are connected properly. I checked that first as soon as I took delivery. Thoughts?

 

[Devious_Snake]

In the warmer temps, hooking is not that much of an issue. Your car is still stock with the 3.31 gearing. Your right the initial hit is not there, but honestly even at 40 in 2nd, its not going to hit that hard until it climbs. Trust me the factory tune is soft. The other issue is I know you particularly, are subconsciously comparing your modded cobra to this car. Very different power deliveries. Now my car is at 701/690. At a 2nd gear roll on in 40 it hits, and it hits even harder in 1st. I dont think there is anything wrong with your car, your are just a more seasoned driver. Sport mode does yield more and everything off is really the fun mode to be in, but needs more attention.

Fwiw I am now running 305 DR's. The car feels so much faster with those mounted on the stock wheels. I could imagine if I threw 3.73's in there.

I think of this car as a "refined hammer" in stock form, it becomes a sledge once you add mods and open her up. To most people stock is enough, but some of us need to be on the edge I guess. Start modding! :beer:

 

[BOD89LX]

What were your inlet temps? Mine is modded and I have the PSS tires in stock size and when it was 95 and humid out I could do 1st gear rolls and have to pedal it just a little. When its 60 out and cool night time roads 1st gear has no chance and 2nd will spin if I blast it hard but a smooth roll on and it's fine. So your car sounds like its were it should be. I would guess the reason it pulls harder the fast you go is due to the inlet temps going down with increased speed and air flow. If you watch your inlet temps on a 1/4 mile pass you will see it drops to ambient temp pretty fast.

 

[Smackiavelli]

Here in the suburban shadows of Manhattan Island, we've been trudging through the slop of mid to high ninety degree temperatures and 70 degree dewpoints for over a month. If you step outside your front door and walk ten feet, it feels like you're doing butterfly stroke relays through The Dead Sea. Granted, the last few days have been a bit cooler, but overall this summer has not been much of a friend to a blown car.

That said, in this airmass I am vastly unimpressed with the Shelby's performance. Sure, if you nail it in first on the F1s 30 seconds after pulling out of the driveway, you still experience the cliche of the rear end breaking loose. In no way, however, is this thing the tighty-whitey stainer it is when temps drop below 50. With the ambient heat and humidity as significant as they've been, these cars heat soak to an end of mechanical emasculation. Aside from the first couple times you run through the gears (when the motor is still cold), mine also feels sluggish and uninspiring for the number of equines that run free in the engine bay.

During this ridiculous heatwave, when she's good and warm and I give her, say, 70% throttle in first, the motor sounds decidedly suffocated. Kind of like someone with Stage 4 Emphysema hacking up a phlegm-slimed chunk of lung. There have been many times this summer that I've cracked the loud pedal only to have her fall flat on her face and struggle northward in the RPM range. A buddy of mine recently accompanied me in the Shelby on a bikini-watching excursion to a popular coastal destination not far from us. Big surprise, it was hell fire hot that day. His observation about my new ride was pretty money: "It moves out well enough. But for such a beast, this weather sure turns it into a swamp boat with its ass stuck in the mud."

You probably share my sentiments, Lethal. I'm looking forward to Fall and a new pair of Pilot Super Sports.

 

[Farmer-Ted]

There have been many times this summer that I've cracked the loud pedal only to have her fall flat on her face and struggle northward in the RPM range.

Might want to get it checked out. If what you says is true, it sounds like you have more problems than heat. It's been upward of 105 F around here many times this year and even after long drives with inlet temps in the 150 F range mine pulls cleanly to red line every time.

 

[Fordfourlife]

I can defiantly tell mine has less power when it is hot and humid out vs a dry 65 degree day.

 

[Lethalchem]

I appreciate all the replies guys. It's helpful to hear some of you guys are experiencing similar things. Devious, you're right, I know I keep comparing it to my old 03 Cobra but I feel like the cars should react in similar ways since both use positive displacement blowers, etc. I've lived in Arkansas for 40 years so I'm familiar with humidity/heat, I just keep getting thrown off by the way a car with almost 200rwhp less reacted compared to the Shelby. I could never floor it in first or 2nd gear without spinning no matter what temp it was outside. It just keeps making me question. The Shelby has a bigger blower and a larger displacement motor, it boggles me why it feels like it has less low end torque.

I'll know better once I get it on a dyno and check the power, it just feels weird. Maybe I'm just not accustomed to all the electronic involvement (fly by wire and traction controls that actually work, lol).

Here's a time slip of a 1000' pass I made awhile back and I felt my mph was low, only adding to my suspiciousness. I'm in the right lane:

 

[72SBC]

Mine deffinitly feels slower in the heat. I ran mine when it was 95-110* and still managed to pull 127mph out of it hot lapping it. It's still fast don't worry.

 

[USV8PWR]

All cars, all engines actually, are affected by heat. I remember thinking as a 17 year old kid that my 6 cylinder SHO was not nearly as powerful or quick during the brutally hot summer months. My next car, 1993 Z28 with the LT1, was even worse. I quickly learned the bigger the engine, and the tighter it sits in the bay, the easier it was to become heat soaked. With that said, the 2013 Shelby has a much more powerful engine with a supercharger and it gets HOT. So there are no surprises here with the reduced summertime performance.

Cars like this are a BLAST to drive in really cold temps because all of the extra HP. But then there is much less traction too so it becomes dangerous.

 

[BAS]

Are these observations based on cars with track packs or not?

Smackiavelli - wonderful piece of creative writing, really enjoyed reading your post


Sent from my iPhone using Tapatalk 2

 

[USV8PWR]

Are these observations based on cars with track packs or not?

Smackiavelli - wonderful piece of creative writing, really enjoyed reading your post


Sent from my iPhone using Tapatalk 2

Mine has the track pack, and while that I'm sure that option helps somewhat, extreme heat outside still holds down its performance.

 

[MOUNT-N-SLOT]

Try the same pulls with the TC completely disengaged, eliminating TC as the issue. But be careful, the car seriously steps out.

90 - 70 degrees makes a big difference in stock tire grip.

I have the Track Pack. My inlet temp will climb well over 140 at idle waiting for a light on a 90 ambient day. Once I start moving, within a few minutes, it's 2 degrees below ambient. There is a difference in power at those temps. On my dyno run, my 3rd pull was higher than the 2nd because we waited a couple of extra minutes for the fans to drop the inlet temp.

 

[Smackiavelli]

Might want to get it checked out. If what you says is true, it sounds like you have more problems than heat. It's been upward of 105 F around here many times this year and even after long drives with inlet temps in the 150 F range mine pulls cleanly to red line every time.

I briefly considered taking it to the dealer, but I know from having owned numerous high HP cars that, generally, their M.O. is to suffer a palpable power decline in excessive heat (as others have also noted). The key, though, is not really the heat. It's the relative saturation of the lower atmosphere (a.k.a., humidity). By itself, a 100+ degree temperature--while having an adverse effect--is not typically enough to inspire that 'driving through molasses' feel. When, however, you have, say, a 73 degree dewpoint coupled with 100+ degree temperatures, the heat index elevates by a marked percentage (the exact number depends on a variety of factors, not the least of which being the depth of the moisture at the surface). With all the rain we've had, evapotranspirative influences play a role as well. For instance, I've seen ambient dewpoints this summer in the low seventies raised locally by evapotranspiration to mid and high 70s. That kind of airmass is intolerable for human or vehicle.

So, it's not just about heat. It's the quality of the air the engine is breathing. For our purposes, hot, dry air would be considered higher quality than hot, saturated air. I'd take inlet temperatures of 150 in an airmass characterized by 50 degree dewpoints any day over 95 degree inlet temps with a 73 degree dewpoint.

I see you live in Salt Lake City. While you guys don't completely escape humidity, your climate is predominantly subhumid. If I'm not mistaken, your deepest surface moisture typically occurs during the spring. Conversely, your summers are characterized by high heat but low RH (I just looked at a surface map for SLC and the dewpoints seem to be in the high 40s to low 50s--pretty dry). I mention this, because I wonder how your Shelby would feel to you if you drove it in 105/75 degree air as opposed to 105/48 degree air. The former is close to what my Shelby has been breathing (or choking on, more accurately) all summer. There could still be an issue, of course, but my gut is that the motor just isn't responding well to gasping through an SAI. That's what the stock CAI becomes in a 105/75 airmass - a Sauna Air Intake.

Smackiavelli - wonderful piece of creative writing, really enjoyed reading your post.

Thanks, dude. Just trying to add a little suspense and color to talking weather and sluggish Shelbys.