I have read for a while now about how sensitive TPI cars are to hot and cold weather conditions. And how hot weather really slows them down. Hence the popularity of the low temp thermostat mod, cooler turn on temps for the fans, IAT relocation, etc.

I'm not sure about the reason for this, but let me tell you it is absolutely true!

Since I finished the latest mods on my car (headers), I have only really driven in in hot / humid conditions during Sydneys summer months. This summer has been very hot and very humid. When I nail the car from a standing start in these conditions, it would spin the tyres for about 10 feet or so.

Well late tonight it was coolish and dry, for the first time in months! I decided to do a few test runs driving home in the wee hours

I nailed the car in D from a standing start. Result? Well she seriously smoked up both tyres, went sideways, and redlined almost immediately in first gear!

I thought OK, lets try something different. So I rolled along at idle doing about 10 to 15 MPH, and then floored it (again in D). The car didn't go sideways this time, but the tyres immediately broke traction and sqealed severely all the way thru 1st gear. It only hooked up about 1/2 a second after it changed to 2nd

This baby 305 motor is really hauling some ****! I can't believe there is so much difference in power depending upon what the weather conditions are like.

I'm really looking forward to another run at at the track in the winter months, with and without nitrous. Without the nitrous I think that my 14.6 secs summer run will be shattered, in favourable weather conditions



------------------
1987 Chevy Camaro IROC-Z. 305 TPI. 700R4
14.6 secs @ 93 MPH.
2.14 sixty foot.
Nitrous soon! :-)
http://www.camaro-firebird.org
Camaro and Firebird pages in Sydney, Australia.

 

What are tyres? LOL.
Hey, if you run into Elisabeth from Survivor, kidnap her and send her to me!
Yes, TPIs are affected by heat. Thats why we bag the plenum with ice between rounds at the drag strip. Keeps the incoming air cold and fools the MAT/IAT sensor. GM keeps the TPI running hot (like 220deg F) for emissions purposes. Thats why the fan switch is a popular option.

------------------
Rob P
89RSconvtZZ4TPI
Edelbrock Hi-Flow Intake
SLP Dual Cold Air Intake
1 5/8" Headers
Semi-Siamesed Runners
MSD6AL/relocated MAT/ AdjFPR/IROC frnt@rear swaybar/wonderbar/steeringbox/alum drvshaft/ Alston SFC/3:23posi disc rear/MAC LCA/H.Adams Panhard Rod/KYB struts/ shocks/
92Z28convt5spd
71Impala convt 402BB
BETTER DRIVING THRU SUPERIOR HORSEPOWER!

 

My '87 is very heat sensitive. When it's cool it runs hard but I can really notice a loss in power/ET during the summer heat. For some reason my '98 is less sensitive. Plastic intake maybe?

------------------
87 Formula 350 13.94@96.67
98 Z28 1LE 13.15@107.59
1LE Owners Association

 

I know how the temp is. During stop/start conditions in Daytona Beach during the summer, the engine really bogs down. I notice a strong gas smell and the oil pressure dips way down. Doesn't happen in cold weather.

------------------
1985 Camaro Z28
minor mods, wires, filters, etc., Accel SuperCoil/cap/rotor,
305 bored .030 over, new pistons, cam, lifters, timing kit, water pump, high-flow cat (3" out), Dynomax Afterburner muffler (2.5" out), O2 sensor, MAF sensor, 160W JVC head unit, Rockford Fosgate Punch 360 amp, 2 JL10W0 subs, custom box.
"You may laugh in the face of fear, but it'll be a nervous, unconvincing little laugh."

 

your tires may have hooked up better in the warm weather.

Curtis

 

so true... florida summers play hell with our cars. when it got cold this winter and i was cruising around town the car felt so much more powerful... it's the only reason i like winter down here =)

------------------
'88 WS6 Formula - Stock LB9

 

You are sooo right! I lived in MD all my life..I moved down here just a month ago for schooland when I to the track, I went 6tenths slower down here!!! It was about a 45 degree temperature change..MAN OH MAN!! That was depressing considering I had done alot of work to the car too. I only lost 2 MPH though. 15.2@92 here is a 14.6@94 in November in Maryland!


------------------

• Red '88 IROC 5 Speed 305 TPI w/3.08
• Dual Friction Stage III Centerforce Clutch
• Accel 300+ Racing Ignition
• Accel 300+ Pro Sleeve Plug Wires
• AC Delco Rapid Fire Plugs
• Flowmaster Force II 3 Chamber Cat Back Exhaust
• Hypertech Chip
• Hypertech Airfoil
• Gutted Air Box
• Best E/T 14.686, 60' 2.205, 1/8th mile 9.461, 1/4 MPH 93.91
• Best 60' 2.17
• TPiS AFPR set to 42psi using Accel Fuel pressure gauge (Installed after run)
• Aluminum Driveshaft (Installed after run)

 

Yarnboy, that is amazing to see the numbers you posted up. 0.6 seconds slower!!!!!!!!!!! A HUGE difference.

I can definitely believe it too, based on SOTP feel.

Summer here in Sydney is hot and humid (sub-tropical), much like Florida I imagine. We have temps from around 85 to 110 in the summer, with high humidity.

In winter the air is dryer, with daytime temps around 60 deg. Perfect for racing

Oh and Rob P, if I see Elisabeth I am keeping her here in the beautiful land Down Under

------------------
1987 Chevy Camaro IROC-Z. 305 TPI. 700R4
14.6 secs @ 93 MPH.
2.14 sixty foot.
Nitrous soon! :-)
http://www.camaro-firebird.org
Camaro and Firebird pages in Sydney, Australia.

 

The temperature does play a bit of a role in these cars, but it's usually not extreme. The engine will run better in colder temperatures, but if you can lower the engine temp via the mods desbriced, relocated MAT, bypass IAC, maybe cold air induction, lower temp thermostat with programmed compensation on the chip, and the fan swith the engine should not vary all that much. What you described with your day time and night time runs sounds much more like a traction issue. On warmer pavement or I should say with warmer tires your car will hook up much better and likewise your times should be better. The tires will break loose very easily on cold ground. My suggestion is one of two, either do these mods and see how you run in the heat or do a small burn with your tires before you do a run. This especially helps with putting a couple of gallons of water on the ground backing into it burning a bit to heat up the tires and clean them, and then pulling up to run, same as in the burnout box at the track. If your tires are warm and you get a good launch under both conditions then and only then can you really compare the hot to cold air temps. Good luck and happy racing.

------------------
87 GTA 350 L98
K&N filters, beefed up TH-700r4, Accel Manifold, Ported Plenum and Runners, Fuel Press. Regulator 49.5psi, air foil, modified MAF, SLP cold air box, Hypertech Thermomaster chip w/160 thermostat, MSD 6AL and Blaster 3, B&M shift kit & megashifter, Moser Ford 9in Rear with Richmond 3.50 and locker, Edlebrock TES headers and Cat Back,Hotchkis setup in rear, Poly suspension and Koni in the front, relocated MAT, bypassed IAC,

Fastest ET's
Stock-0-60 6.8, 1/4 15.0 @ 94
Best-0-60 4.7, 1/4 12.8 @ 112
Norm-0-60 5.2, 1/4 13.2 @ 108

 

You actually need to spend some time at the track to know what is really going on. But anyone who does knows that as the night goes on, the air gets cooler, and you run faster (now if the temp gets down in the low 50's & 40's, maybe you would have some traction problems). And the difference CAN be extreme (.6 IS extreme, most people will see only a .3 or .4 difference). Cooler air is more dense, more air = more power. TPI is just a little more sensitive to it.

In bracket racing..you are not necessarily looking to get your best ET, but to be more consistent... I had an 82 Firebird with a carbed 350, that ran 16.0...not lightning fast, but it ran 16 flat all day long...and I won quite a few races that way. My IROC is not as consistent... I can vary up to .4 between hot and cool runs, and that is NOT condusive to winning bracket races.

But if you are just trying to get that "best" ET, before your run ensure that you are completely cooled down. Even the Mustang guys know to ice their plenums between runs to reduce the heat soak effect. You dont have to go to that extreme (or maybe you do), but little things like keeping your hood up between rounds, ensuring you are at the front of the staging lanes (or waiting at the back of the line till most people have run and then get up to the lanes), not running your engine until the staging director motions you to the waterbox, will all help you run cooler/faster. Run your electric fans any time the motor is running (and for a while after, with a manual fan switch).

I get my best ET's when my coolant temps are between 100* and 110*, but every car performs differently. You just have to find your "sweet" spot. And the only way to do that is to run it in hot weather, run it in cold weather, and run it again and again and again. Log your results...Log your tweaks and modifications. I have over 260 logged runs and pretty much know how the car is going to act in certain situations. Many Sportsman class racers have race computers where all their previous data is recorded and they can predict, within a certain degree of accuracy, what they are going to run given certain track conditions (air temp, barometer readings, etc.)... Each time you make a modification, you have have to run the car in different situations all over again... To people who say "I changed this or that, and I am running much faster", I say..."Show me the Time-Slips". And not just one...

------------------
Mike Metzler (Desert86Roc)[*] Webmaster: SpeedWorldMotorplex.com[*] Click Here For 86 IROC 305 TPI (406 build in progress) Page

ET's @ 1250 ft[*] 14.28 @ 95.461 mph (uncorrected, NOS, no headers)[*] 15.365 @ 86.785 mph (uncorrected, headers, no NOS)

[This message has been edited by Desert86Roc (edited April 02, 2001).]

 

How is the MAT relocated and the IAC bypassed? Thanks, Doug

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'91 Z28 - 50,000 miles. All power options leather. 350 TPI:
K&N; Fastchip; Airfoil; Custom 'Ram-Air'; SLP Headers; Slp Runners; Borla Catback 50% open; Dual factory Cats; Poweraid TB spacer; March underdrive pulleys; Accel Extreme 9000 wires, Accel coil; Hypertech rotor & cap; NGK platinum plugs; manual fan switch; TB coolant bypass; Pirelli P7000 Z245/50/R16 all season tires; Energy suspention motor mounts; smog pump delete.
S Cobra Radar Detector; Z28 SS Floormats