JoshHefnerX

Yes, I have searched and haven't exactly gotten the info I'm looking for.

98 Camaro, stock computer, that someone has 'adjusted'
Stock fans/rad
6MT
stock cam, shorty headers.

Car holds temp fine at fwy speed - sits about ~208 at 65mph. A/C on, hot day 110+ here in PHX. Also, no problems at any speed when temps are below 90ish.
Car sorta hold temp at idle in the driveway, hood up, a/c on. about 210-212. Hood closed temp gets up quicker, but still more or less holds temp on hot days 110+
Problem comes in - on a road on the way to my house. Speeds are 35-40. Gains heat pretty quick. From the fwy to my house was about 2.5 miles. Had to stop at the bottom of the ramp and a stoplight part way home. The temp rose and kept rising. Was 228 when I got into the driveway. Let it idle, about 10 mins - a/c on, it started to drop again, slowly.

The temp settings read off in hpt showed 185/180 low, 189/180high. No idea what thermostat is.

First thought is that my fans are weak/tired, since it holds temp on the fwy. The fans don't seem to have the air flow that some of my cars have when blowing but don't have a definitive way to measure. They do kick on/off for both speeds on the pcm specified settings. These are brushed motors in the fans correct? And if the fans were doing the job, and they are turning on in the 180s (they are), that it in theory should hold not much higher than the thermostat temp (which if stock should be about 190). I have replaced the relays, and have a new battery. Running voltage is about 13.8 for ref.

Second thought is raising the speed cutoffs from the factory 35 disable, 30 enable. If I'm understanding the logic, the fans cutoff at 35, and don't re-engage unless I go below 30. So potentially I'm riding around throughout the 30's w/ no fan (which are the speeds encountered on the infamous road)

My previous studies showed in general that you probably more likely need fans up to 50ish to get enough airflow. GM didn't seem to think so...

This is where I asking you guys: Does anyone have data on the speed equivalent of the fans in this car? Has anyone bumped the speed disable up to say 50, and noticed any difference good or bad?

Any other thoughts?

ChopperDoc

Bumping up the MPH a bit on the enable/disable for the fans probably won’t hurt anything. I’m not sure at what point you would damage the fan motor, if at all. GM may have set it this way to reduce drag above “x” flow, since at some point the fan will hurt more than its helping.

These cars always have high temps (at least IAT’s) because of the air box being parked right on the radiator. GM also thought that was a good idea. So… yeah.

Eventually I’m going to install a standup radiator in place of the crappy stock one, and pipe my intake tract down to the nose, as it should of always been on these cars. For now, like you, I’m stuck at 210-230* idle in the summer heat. Fans don’t seem to change that enough in my case. Maybe this weekend I’ll test that MPH theory out for you. I’m not sure it’ll make a substantial difference but I can do it for science lol.

ChopperDoc

Oh and running the A/C will typically increase your temps, not decrease them. The heat exchange occurs at the condenser in front of the radiator. So in essence, you get nice cool air, your radiator eats the hot air off of the condenser.

I recently had a coolant leak on my daily (2012 Cruze) on my way to morning formation for PT. It just suddenly shut the A/C off due to high engine temps. It came up on the DIC saying it was disabled.

So there I was that morning after PT, sweaty as all hell, driving quickly down to the shopette to get coolant with my heat cranked full blast, windows down, on a nice brisk and humid 80* morning lol.

The heater brought the temp down a solid 10 degrees or so. I was giving the engine somewhere else to put the heat from the block. My face. It sucked but it’s better than warping a head.

JoshHefnerX

Thanks, for your response. I appreciate your time.

I am familiar w/ the a/c principals. And noted it due to the extra heat load. A/C did increase temps at idle by a solid 10 deg. However it didn't make much difference on the infamous road. I've driven this several times - and did turn on the heater once, didn't help enough which is my concern.

In the 30's - low 40's mph range the temp never stabilizes. If it found a temp and stayed there, I'd be ok, understanding the balance point. But didn't hit that balance point - and I'm not running no a/c in phx. Too old and fat and intolerant of the heat to do that. lol.

And the chin spoiler is in place.

I'm a little leery of playing w/ too many writes on this pcm - it's the original 98 that are more known to brick without warning. This has been already been played with by a PO, I'm not fond of what was done and not sure how many times it's been written.

I'm not up to doing a pcm swap and have emissions to get through in the next few weeks.

ChopperDoc

I had a 98 PCM for quite a while before finally bitting the bullet and swapping it out with a 0411, P01. That was a long day, but worthwhile in the long run I suppose.

I flashed that thing probably a hundred times or more tweaking the tune and experimenting. It had a hard time keeping up with my 427 LS3. It never did brick. I removed it primarily because it was slow, and secondly because of my 4L80. With a P01 you don’t need the relay. I was having shifting problems with the relay and old computer. So it stood the test of time and tuning sessions.

I will warn you though, that if it ever does brick on you, it’s almost impossible to find one. I’m not aware of a “write limit” on any particular PCM, but if there is one, it’s probably pretty high.

ChopperDoc

I said all that to say, you should be good to flash in some new fan settings. I’d change it to 45/40 or something like that. Then again, it is the infamous 98 PCM as you say. However, If the previous owner played with it, I’m sure you can too lol.

dlandsvZ28

Check the bottom five inches on the AC Condenser and the radiator. If both have never been cleaned I can almost guarantee they are plugged with dirt and sand and gravel. With the bottom rows plugged the efficiency of the ac condenser and radiator is probably only about 80 percent. It's all about total surface area in order to transfer heat from the radiator and ac condenser with ambient air flow.

Here is KS with average summer temps in mid 90's and many time north of the 100 degrees the threshold to not overheat and cool the cabin is for sure over 95. Over 95 overheats, under 95 probably ok.

Believe it or not the C7 Z06 have the same issue. They finally solved the issue but it took 3 to four years. There's a TSB for the fix.

What I did on my Procharged 98 Z28 was to add two 11 inch Spal pusher fans on the face of the AC condenser. The pusher fans move air thru the ac condenser much better in slow moving traffic or in stop and go traffic. BTW - all airflow to the radiator has to move thru the ac condenser first. With the ac on heat from the condenser flows directly to the radiator. So with the ac on the differential air temp is the difference between the temp of the air from the ac condenser and 195 degrees if you have a 195 degree thermostat. So the differential is only about 50 degrees. With the ac off the differential is 100 degrees if ambient if 95 degrees.

The pusher fans worked but not so good when temps were 100 degrees or more. To resolve the issue I move the ac condenser off of the face of radiator and into the front bumper cover. I also added a transmission cooler with the lines running directly from the transmission to the cooler. Isolating the cooler from the radiator will depend on winter temps. If winter temp get to zero or below, you will probably want to route the lines thru the radiator. This step assumes you have a A4.




You can also reduce the antifreeze ratio to less that 50 percent. Pure water cools better than a 50/50 mix. Water wettter also helps

JoshHefnerX

Thanks for the post. I dont know why it didn't occur to me to check/clean the condenser/radiator. But that is a good idea. Gonna pull the fans/shroud maybe this weekend if it's not broiling hot outside and will do it then. Was damn hot this weekend, wife got heatstroke yesterday.

Running an M6, so at least that's one less thing adding btu's to the mix.

I am running ~20% on the coolant, rarely gets down to or below freezing here.