ET change from heat soak / hot lapping
#3221904
03/21/24 01:13 PM
03/21/24 01:13 PM
|
Joined: Dec 2021
Posts: 1,146 Loudoun County, VA
Brad_Haak
OP
super stock
|
OP
super stock
Joined: Dec 2021
Posts: 1,146
Loudoun County, VA
|
I spent last Saturday at Capitol and Sunday at MIR getting significant seat time in the 1320 for the first time since 2022. This car has always been very sensitive to heat soak from being stuck creeping forward in long staging lanes, or when I've run two classes that are back-to-back and basically hot-lapping me.
How are you adjusting dial-ins under these conditions? --> Do you have enough data to be able to predict (reasonably) accurately how much you'll slow down? --> Are you taking a s.w.a.g. about how much to change the dial-in simply cuz you know the car's gotten hot?
I got in 10 passes on Saturday and all I can tell you is... yes, the car gets progressively slower as the cool-down intervals get shorter. Disregarding some changes in the DA for the time being, the car ran the following when "cold"... 45-60 minutes between passes: 11.857 11.856 11.876
When the cool-down interval was only 20-30 minutes: 11.978 11.946
When I intentionally hot-lapped the last 3 passes only about 8 minutes between them: 12.228 (spun) 12.024 12.059
So I'm wondering how other people account for this variability. Thx
2021 Challenger 6.4L Scat Pack 1320 100% stock: 1.680, 11.894 at 113.75 (DA 175 ft) weight reduction, wheels, tires, Hellcat air box: 1.661, 11.686 at 115.97 (DA 710 ft)
1973 Challenger 452 ci street/strip [2008] pump gas, DOT radials: 1.454, 10.523 at 126.44 (DA 514 ft)
|
|
|
Re: ET change from heat soak / hot lapping
[Re: Brad_Haak]
#3221906
03/21/24 01:42 PM
03/21/24 01:42 PM
|
Joined: Jan 2004
Posts: 4,576 Motor City
6PKRTSE
master
|
master
Joined: Jan 2004
Posts: 4,576
Motor City
|
We used to do a track rental. The most that I ever got in was 27 passes in one day. This was with my mostly stock Charger cruiser street car. Stayed from 13:60'-13:80's all day. That car doesn't vary much every.
1963 Belvedere 440 Max Wedge Tribute 1970 Charger R/T S.E. 440 Six Pack 1970 Challenger R/T, 528 Hemi 1970 Charger 500 S.E. 440 4 BBL 1970 Plymouth Road Runner 383 1974 Chrysler New Yorker 440 1996 2500 RAM 488 V-10 4X4 2004 3500 Dually Cummins 4x4 2012 Challenger R/T Classic.
|
|
|
Re: ET change from heat soak / hot lapping
[Re: 6PKRTSE]
#3221907
03/21/24 01:49 PM
03/21/24 01:49 PM
|
Joined: Dec 2013
Posts: 4,693 Wichita
GY3
master
|
master
Joined: Dec 2013
Posts: 4,693
Wichita
|
Usually the first pass is .01-.02 slower because of fluid temps. Car usually repeats dead on after unless tremps or DA change radically. I've run 11.41 three in a row with no issues.
'63 Dodge 330 11.19 @ 121 mph Pump gas, n/a, through the mufflers on street tires with 3.54's. 3,600 lbs. 10.01 @ 133mph with a 250 shot of nitrous an a splash of race gas. 1.36 60 ft. 3,700 lbs.
|
|
|
Re: ET change from heat soak / hot lapping
[Re: metallicareload]
#3221943
03/21/24 05:57 PM
03/21/24 05:57 PM
|
Joined: Jan 2003
Posts: 3,923 Richmond, Indiana
19swinger70
master
|
master
Joined: Jan 2003
Posts: 3,923
Richmond, Indiana
|
I assume your engine coolant temp is well regulated? If so, I wonder if your fuel temps rising are what is responsible for the change. I have "hot lapped" at Moparty as part of their "drag-n-drive" class, and my runs were pretty well identical back to back.
1970 340 swinger. sublime 1967 barracuda fastback BB 55 Plymouth Project
|
|
|
Re: ET change from heat soak / hot lapping
[Re: 19swinger70]
#3221994
03/21/24 09:03 PM
03/21/24 09:03 PM
|
Joined: Oct 2005
Posts: 272 Anchorage, Alaska
metallicareload
enthusiast
|
enthusiast
Joined: Oct 2005
Posts: 272
Anchorage, Alaska
|
I've run as quick as 13 minutes apart. Car is usually .01-.02 quicker due to hot lubes. If your car doesn't have a fan/water pump system that you can run with the engine off it's going to be slower. Best thing we've done. Don't shut it off. Let it idle. Yes it'll be slower. Yes it'll be consistent. Doug It's a street car with electric fans and everything else stock, so it'll hold around 180 to 190 degrees water temp once up and running
440, 4-Speed, 3.54 1968, when Dinosaurs ruled the Earth
|
|
|
Re: ET change from heat soak / hot lapping
[Re: metallicareload]
#3222014
03/21/24 10:17 PM
03/21/24 10:17 PM
|
Joined: Dec 2021
Posts: 1,146 Loudoun County, VA
Brad_Haak
OP
super stock
|
OP
super stock
Joined: Dec 2021
Posts: 1,146
Loudoun County, VA
|
The car has a 203* 'stat, but the big issue is while sitting I can watch the IAT climbing continuously until the car starts getting up to speed again
2021 Challenger 6.4L Scat Pack 1320 100% stock: 1.680, 11.894 at 113.75 (DA 175 ft) weight reduction, wheels, tires, Hellcat air box: 1.661, 11.686 at 115.97 (DA 710 ft)
1973 Challenger 452 ci street/strip [2008] pump gas, DOT radials: 1.454, 10.523 at 126.44 (DA 514 ft)
|
|
|
Re: ET change from heat soak / hot lapping
[Re: Brad_Haak]
#3222046
03/22/24 07:21 AM
03/22/24 07:21 AM
|
Joined: Jan 2003
Posts: 8,030 Tulsa OK
Bad340fish
master
|
master
Joined: Jan 2003
Posts: 8,030
Tulsa OK
|
Do you have a way to see air inlet temp? I bet it is much higher on a hot lap and the inlet sensor is also likely to respond pretty slow. It would be interesting to see if you could make a resistor that plugged in and locked the inlet air temp to a single number.
I moved my Barracuda over to a Rife brand inlet temp sensor because they respond very quickly. My car picks up under hood air from the hole in the hood at low speed and idle. So I leave the line with a higher than ambient inlet temp, sometimes as much as 30-60*. The original GM style inlet temp sensor is right at the top of the throttle body. With the GM sensor I start the run over ambient and it took almost the entire run for the sensor to read ambient again. With the Rife sensor it reads ambient almost immediately after I mash the throttle. That helped smooth out my tuning some because the slow response time was messing with the inlet air temp correction. I might have gained a few hundredths from this but for sure gained more accurate data. I am sure an OEM with border line safe compression ratios pulls timing and throttle response with higher inlet temps.
68 Barracuda Formula S 340
|
|
|
Re: ET change from heat soak / hot lapping
[Re: Bad340fish]
#3222139
03/22/24 02:00 PM
03/22/24 02:00 PM
|
Joined: Dec 2021
Posts: 1,146 Loudoun County, VA
Brad_Haak
OP
super stock
|
OP
super stock
Joined: Dec 2021
Posts: 1,146
Loudoun County, VA
|
Do you have a way to see air inlet temp? I bet it is much higher on a hot lap and the inlet sensor is also likely to respond pretty slow. Yes; there is an IAT gauge option that seems to give pretty quick response to changes in airflow. It's generally about 5* above ambient while the car is moving a a reasonable pace, but I can watch it keep getting hotter the longer I'm stuck waiting to move. Those hot runs hurt right from the 60', too. It must take a big gulp of the heated air and pull the timing, then it ramps it back in as the IAT comes down as the car picks up speed.
2021 Challenger 6.4L Scat Pack 1320 100% stock: 1.680, 11.894 at 113.75 (DA 175 ft) weight reduction, wheels, tires, Hellcat air box: 1.661, 11.686 at 115.97 (DA 710 ft)
1973 Challenger 452 ci street/strip [2008] pump gas, DOT radials: 1.454, 10.523 at 126.44 (DA 514 ft)
|
|
|
Re: ET change from heat soak / hot lapping
[Re: Brad_Haak]
#3222999
03/26/24 09:43 PM
03/26/24 09:43 PM
|
Joined: Aug 2011
Posts: 2,869 Pattison Texas
CSK
master
|
master
Joined: Aug 2011
Posts: 2,869
Pattison Texas
|
I have a Tazer it does lots of stuff, one of them is you can run the cooling fans to cool the car down
1968 Charger COLD A/C Hilborn EFI 512ci 9.7 compression, Stealth heads, 4.10 gear A518 ODtrans 4100lb,10.93 full street car trim 2020 T/A 392 Stock 11.79 @ 114.5
|
|
|
Re: ET change from heat soak / hot lapping
[Re: dvw]
#3223018
03/26/24 11:44 PM
03/26/24 11:44 PM
|
Joined: May 2003
Posts: 6,566 Downtown Roebuck Ont
Twostick
Still wishing...
|
Still wishing...
Joined: May 2003
Posts: 6,566
Downtown Roebuck Ont
|
Have you tried running it with the IAT unplugged. It'll set a fault but in normal driving during tests I've never really felt a difference on numerous vehices. Doug I would expect it to default to max IAT range and trim accordingly if you unplugged the sensor. Kevin
|
|
|
|
|