maidenracing1984

Hey guys, i'm new to this forum but i was wondering why the temperature of the motor effects performance so much? A while back i had my car at the track and i trailered it down there and off the trailer, with the temperature still hardly moved on the gauge, the car went a 13.49... after the car got hot, well warm ~160-180ish, the best i could do was only a 13.80. could this be caused by the car running in open loop the first pass and closed the rest? this isnt the first time ive noticed this happening, ive raced my car many times and ive had similar effects, if the car fully cools down for about an hour between passes with the fans running the car will run about .3 tenths faster than if it was still at the operating temp. My car is running the stock 93 tune with a few bolt ons and stock gears stock manifolds. On the cool passes my car averaged a 1.94~1.98 60 foot and when the car is hot it averages a 2.05~2.10 60, but the mph is the same at 99. could this be fixed by tuning the car? maybe throwing in a 160 thermostat and tuning the computer to run it? i understand heat soak can effect an engine, but i wouldn't imagine it being .3-.5 seconds slower. thanks guys

guppymech

iTrader: (7)

If your mph is staying the same, so is the hp the engine is making. The improvement in ET is due to the better 60' times you get off the trailer. Are the 1/8 mile mph numbers staying the same also. Maybe your cold tires hook better than when they get warm. Your times look like you have a A4 trans?

maidenracing1984

yeah its the a4 4l60/700r4 and no the tires hook just as good both passes, the tires held me through a 12.41 pass with a 1.80 60 and i know they're not spinning, i just cant figure out why the torque is more when cold as compared to hot and the 1/8 mile times will be about .10-.15 faster when cold. you can just see the improvement in every part of the et. the 1/8 mile mph may go up .5 when cold but not much of a noticeable difference.

HellTeeOne

I have found that variances in the ambient temperature and humidity level has a lot more effect on the performance of an LTx motor than whether or not the motor is at full operating temperature.

I run a stock stat and my fans are programmed to turn on at 180.

All of that said, if the ambient conditions remain constant, it's been said that these cars like to run "with their feet in the fire and their head in the freezer", meaning that a dry ice bag, cold pack or spraying down with extra bottle of n20 on the intake manifold before making a pass will likely be worth 1 to 1.5 mph in the 1/4.

maidenracing1984

That makes sense i suppose. i know its all about the intake temp, when i would bracket race the car i kept an ir temperature gun with me and would take the intake temp in the staging lanes. if it was 100 or below, it ran like a bat out of hell, if it was 100-120 it ran decent, but anything over 120 it was a slug.

96capricemgr

iTrader: (1)

MPH tells the HP story, it is pretty consistent HP wise. A tenth in the 60ft can easily make for .2 at the other end, a gulp of hot air can slow the 60ft but once moving the IAT goes to ambient.

maidenracing1984

That makes more sense to me, since my CAI is made from thin metal piping it could be easily heating up and allowing the air in the tubing to warm up until it gets higher rpms and then the hp would be the same. i may benefit from wrapping it in a heat deterring material or switching to PVC or plastic K&N type intake. I may also loose some heat in the engine bay by going to headers rather than the stock manifolds.

Ed Wright

iTrader: (1)

That is a tuning issue, nothing to do with it being an LT engine. A few key strokes can lessen that a lot. Even more so with the OBD2 boxes.

maidenracing1984

Unfortunately i don't even have the ability to program my car through the obd1 port, i have to change chips. any clue what part of the tuning is causing it to perform like that? i have the tuning software to tune the car, so i can tune the car myself, i just dont have the know how some guys do.

Ed Wright

iTrader: (1)

When you have air temps effecting the performance too much, most would look into the IAT/MAT correction tables.

HellTeeOne

That is news to me, but coming from someone like you that statement makes my very curious.
My car has always had a very noticeable difference in performance between, say, a 45 degree winter day with zero humidity and a 85 degree humid summer day. This has been the case ever since it was completely stock and continues now with my current ported heads/cam/bolt-ons setup. I don't currently have hard numbers to back it up, but I do remember as a nearly stock/bolt-on car it was 1-3 mph faster in the quarter in cool weather than it was in summer heat.
My car is converted to OBD1 because my tuner reccomended it years ago when I started to do internal engine mods.

Ed Wright

iTrader: (1)

All cars are effected by temp changes that big, but properly tuned the LT1 is now worse than any other.

maidenracing1984

Okay well I'll try to tinker around with those values. As far as the mph goes. My car will gain mph in cooler weather. But in the same weather it remains the same only the 60 ft is different. Which makes me think it was tuning. Because the mph is the same the hp is also the same. But the torque is different. Correct?

maidenracing1984

would it be these values that would need to be worked with?

Ed Wright

iTrader: (1)

Yes sir.
If your 60's vary in the same air, that is not tuning. That would be the car or driver. Not going up at the same coolant temps every time, variations in under good temps (these tend to stabilize going down the tracks if ambient a don't change), trans fluid temps, variations in burnouts, etc, etc.

maidenracing1984

alright, ill see what i can do. If it is in fact the car just not being cooled back to the same temp, would a 160 tstat and tuning the computer to match help the under hood temps?

Ed Wright

iTrader: (1)

I use a cool down battery and Dakota Digital coolant temp gauge. I have a four wire Weatherpak connector between my fans & electric water pump. My cool down battery has 6' leads and a four pin Weatherpak connector. I unplug the car from the fans & water pump. When I plug in the cool down battery it powers up fans, pump and temp gauge. Just look inside to check coolant temp.
I charge the car batteries and cool down battery (separate chargers) between runs. I cool it to the same temp each pass. On a hot day, open the hood in the staging lanes to let the under hood temp equalize. Your car will repeat much better if you keep temps the same. This applies to iron block engines.
Alum blocks, like LS engines, don't much give a ****. Iron blocks (not just LTs) like to run cool water & warm oil. Mine runs quickest leaving about 90 deg F. LS engines, all alum engines I ever worked with, seem to like 180 to 210, then start to taper off. My old Outlaw Sprint Car was that way, and I blamed that on the Methanhol until I started working win the LS1s.

To answer your question, yes it will like a 160 'stat, and set the fans to come on about 175 & go off about 168. Keep it in a narrow range for consistency.

Really hot days I blow a carpet drying fan under the car to cool the trans & converter. Temps there effect converter stall & slip.

maidenracing1984

Yeah. That's what I do with my race car. Last time it was there it ran 7 back to back 5.67's and it's an iron block and heads car. But I was going to invest in a ewp for my lt car. I just haven't came across the money yet. I think I'll buy a 160 tstat and program the fans like you said.

Shownomercy

iTrader: (1)

All that and no external trans cooler setup? Get some quick connects, a pump, fan, and cooler. Bam.

Or real fancy and get a water tank based one.

Ed Wright

iTrader: (1)

You need to go to some NHRA races, and hang around the faster Stock, Super Stock & Comp cars. Watch how they run them. You are way out of touch. I haven't seen a tranny cooler on a fast SS car in five or more years.

Pretty much nobody uses that stuff anymore. You will see guys putting their cars up on the 2 step behind the water box to warm the tranny up. Rossler, A1, ProTrans, all the higher end actual race trannys are shipped with cooler fittings plugged and looped internally.

But, we also drag race. Which is from a dead stop. ;-)