Hot summer days and the SC

ricardoa1 said:

I used to come up with crazy ideas but at this point you are right not interested in reinventing the wheel.
What I got seems to work ok,
Are you sure you don’t have the pusher wired to the HI wire? From what I see in my options I don’t see how to make it work like you say unless I leverage the Hi wire. The pusher fan won’t do much but might help cool the condenser and push the it’s hot air to the sides while sitting allowing the radiator fan to suck up slightly less hot air.

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Yes, I'm sorry if I gave you the wrong impression. The pusher fan and the radiator fan are wired to the HI wire, and set to run in concert with each other. We installed the largest pusher fan we could find that would fit, a SPAL 2000cfm, and having it makes a big difference. That being said, you know that if I get on it in the heat down here it still isn't enough to prevent the heat from building up.

So the heat got to SPAL fan as expected running 100% this will be my third spal fan that has quit and stated to draw too much amperage. So on a new quest to repair and resolve the issues, as a last attempt before having to give up on the MP FMIC, this time going for dual fans. I found some Moshimoto 10” blade fans that flow and an amazing 1500-1600 CFMs each, I would like to figure out what is the best way to run these two powerful fans without melting stuff. I was thinking one right from the low speed wire using the vehicle wiring and the second one to the high speed wire, then having BE overlap the high and low. So low starts at 190 and Hi start higher if needed? will that work?
The alternative is to power one and a relay with the high speed wire and 2nd with the lo wire which will get switched to the relay power when the hi speed wire triggers it. That will run both.

Guess I need help figuring it all out and the best approach, most dual fan cars have sequential starts to not overload the system since at start is when most amperage is drawn.

So can both hi and lo run simultaneously or is the computer and relay module only doing one or the other?

Might be time to get off the stock systems, and isolate new fans on their own relays, direct circuits and temp triggers. I'm sure Mishimoto could hook you up with all you'd need, including wiring diagrams.

KMT said:

Might be time to get off the stock systems, and isolate new fans on their own relays, direct circuits and temp triggers. I'm sure Mishimoto could hook you up with all you'd need, including wiring diagrams.

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The SPAL was on an external relay, not trying to reinvent the wheel, they advertise 10A during continuous use but I doubt that’s accurate with how much flow they put out, I want two fans as a safety net. In case one fails also will allow me to run a thicker fan and the motor not hit the water pump pulley. If I pull this off it will be revolutionary for the MP FMIC ppl these fans are used in drift cars and sound like buzzing hornets nest. Kinda excited try it and hopefully do endurance stuff with the car.

https://m.youtube.com/watch?v=WzPkem2liws

When you said "I was thinking one right from the low speed wire using the vehicle wiring", which wire did you mean, exactly, assuming you're looking for a trigger and not power? Low speed power at the stock fan, or EEC feed for the low speed relay in the IRCM? Remember, there is a fan cutoff at a certain highway speed, and a fan forced-on when A/C is engaged.

...these fans are used in drift cars and sound like buzzing hornets nest

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If that's all you're after, wouldn't playing cards in the wheel spokes be a lot less expensive...no wiring needed...?

It depends if I am going to run a shroud on them, with one, both fans need to be on otherwise hot air will just circulate from the stalled fan, path of least resistance. Or as an alternative I run a divider or pin it straight to the fins.

If both need to be on simultaneously, I wanted to have a delay if I run a shroud. The stock wiring will power fan 1 with the Lo wire. When Hi wire goes hot it will run fan 2 and trigger the relay to power the number 1 fan. So if have Lo to turn on at 190f and Hi to turn on at 191f. This will provide a cushion, and will be on two separate circuits on case of a problem I wont be stranded with a totally overheating car.

The alternative with no shroud would be no external relay and just have Fan 1 on the Lo wire and Fan 2 on the Hi wire. Assuming I can overlap the Hi setting over the Lo setting in BE. For example Run fan at 190on and 184shut off, but have Hi start at 195F if the Lo fan cant get the job done. Will both wires run if I force it on BE or is the IRCM only do one circuit or the other? Are there there even two circuits? Or is it just one and the relay does either HI or LO but not together.

I can live with the noise, if it fixes my car without going true FMIC. I actually love the MPIC, I love the Pipes and the flow of the IC. alot of big HP mills achieve it with this IC and I am skeptical using anything else.

ricardoa1 said:

...or is the IRCM only do one circuit or the other? Or is it just one and the relay does either HI or LO but not together.

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There are two fan circuits/relays (example '90 SC).



I did some testing and confirmed that if the hi circuit is on, so is lo. We're told the factory expects that if hi is commanded on, lo is already on and the fan spinning under load, since if hi was suddenly turned on alone it would risk spiking a too high current draw.

Using three 5 pin BOSCH relays, you could wire them where LO is the two fans in series, and HI is the two fans in parallel.

Let me see if I have a drawing for that ... Found one!



I would say that you'd connect FAN LOW to PCM FAN CTRL 1, and the FAN HI to PCM FAN CTRL 2 AND 3, to make the magic work.

That puts them in series for lower fan speed (and lower noise!) when LOW speed fan would be commanded; puts them in parallel (for max CFM) on HI speed fan.

All it takes is three BOSCH relays - one must be 5 pin, the other two can be 4 pin (but I'd buy a set of 5 pinners because, well, they're cheap in quantity.)

EDIT: That "IGN HOT" line may need to go to ground to run the fans; the IRCM output is to supply the 12V. If, however, you pick up before the IRCM, then it needs to go to IGN HOT. Just as a note.

RwP

Excellent info gentlemen.

Ralph I like the parallel idea. Never knew fans can be run like that to slow them down. That would help with longevity assuming at low speeds it gets it done in mild temperatures. Feeling positive!

I finished installing the new Mishimoto fans, I cant share pics they are always too big! And unfortunately summer decided to pack it up and temps in Boston are mid seventies, so just like every year my fan takes a dump, testing will have to wait till next year. I just need to wire the relays in the above mentioned manner, I juiced the fans viathe battery it was impressive, wind gushed like a stock fan which does a great job. I also took my time to rubber foam all seams on the shroud plate, and I also added foam on the IC and lower radiator to ensure the only air drawn is from outside and not from areas in the engine bay, I did it by running two strips vertically of window AC insulation foam between the IC and Condenser. Any air will have to pass through the front of the car ONLY, via the Condenser then IC then to radiator. Anyways, hoping for the best. My voltage is back up to 13.6 at idle with nothing on so I'm glad the charging system was not my problem, let see with everything on what it will drop to but I think I will be fine, I feel like I am getting to a good place with the car mechanically speaking, the low voltage was probably causing my misfires I had short on the fan wire causing issues over bumps, a hot mess.

RalphP said:

Using three 5 pin BOSCH relays, you could wire them where LO is the two fans in series, and HI is the two fans in parallel.

Let me see if I have a drawing for that ... Found one!

View attachment 71155

I would say that you'd connect FAN LOW to PCM FAN CTRL 1, and the FAN HI to PCM FAN CTRL 2 AND 3, to make the magic work.

That puts them in series for lower fan speed (and lower noise!) when LOW speed fan would be commanded; puts them in parallel (for max CFM) on HI speed fan.

All it takes is three BOSCH relays - one must be 5 pin, the other two can be 4 pin (but I'd buy a set of 5 pinners because, well, they're cheap in quantity.)

EDIT: That "IGN HOT" line may need to go to ground to run the fans; the IRCM output is to supply the 12V. If, however, you pick up before the IRCM, then it needs to go to IGN HOT. Just as a note.

RwP

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Almost had it working, both fans turned on at 6v each when Lo went hot, but when the Hi wire goes hot the monkey wrench on my car is that the LO speed shuts off. So I’m left with only one operating at 12v while the second one takes a break. Argh! It gotta figure out how to energize the relay that goes dead on Hi setting. Rechecked everything 3 times, spent hours soldiering etc.

Also alternator takes a dive when things get hot on the car still dropping voltage as temps increase, voltage reading mid 11s. What are most of you seeing when car is on idle and AC and lights are on?

At a loss with the extra relays and wiring. I found a way of energizing the lo wire with a fourth relay. And tested the system via the KO code reading sequence. I got them at the slow speed when the LO wire went hot, and when the HI wire got power both fans ran on high setting by giving 12v to the lo wire. All great in theory, and used BE to do the HI fan setting to one degree higher than the Lo fan settings. But the reality was that the car went straight to 220-228 before temps stabilized. Some more testing showed that the HI wire never turned on. It was alway just the Lo wire going hot, what I did manage was to turn on the 94 pusher circuit.

Why is it that the Hi speed wire doesnÂ’t listen to my command in BE but the pusher fan does. BTW the pusher does not have setting in BE I was explained that itÂ’s a logic of the HI speed. It’s all works during the KO code sequence? Argh!

Anyways, running 4 relays to make them run at 6v is getting kinda silly and at 6V as expected doesnÂ’t even scratch it. And so I got frustrated and snipped all my awesome connections and ran the new fans with two relays in a standard configuration, pusher fan is still turning on. And things started to cool as intended.

I am now worried about this voltage situation at idle, voltage lower than 11V is going to run the fans slower and while I got some voltage back from tossing the worn out SPAL now the pusher and is amperage is putting stress back in the system.

I had an AUTOZONE alternator lifetime warranty. I claimed the warranty, guy didnÂ’t bother testing it. Just ordered it. Looks high quality w new parts. I will be running the stock sized pulley, but I have the Underdrive kit and the tensioner bottoms out, a bigger idler will make the belt rub on the water pump I think. Anyone have any ideas on keeping the underdrives but stock on the alternator?

Bumping this up, I've been running the two 10" for about two years at full 12V on each. This summer being put to the test almost every weekend. I feel like it was successful, but there always room for improvements. So asking an additional brainstorming question.

I run 180deg tstat like most, I have read threads on 180deg thermostat and the added benefits of keeping the engine cooler. Below a few points made.

A. Less pressure in the system, adding longevity of the hoses and components, radiator swelling etc.
B. Giving a larger window of between operating and and overheating condition when performance driving.
C. Keeping engine cooler, allowing SC tubes and IC and keep them cooler so when performance is needed, you will have a cooler air charge temperatures, allowing the IC to be less susceptible to heat soak at the end of a power pull.

Mechanic wisdom says 195deg thermostat allows undersized cooling components to run more efficiently, the theory is that the the fan will remove more heat per circulating cycle, and running a 180deg Tstat will just make things worse because without adjusting the fan the static heat of the radiator will increase.

Here is my question.
My cooling system with the AC running hot summer maxes out at about 220f, it just cant cool any further at full demand AC, 95deg sun out hot pavement etc. when at idle. During highway use that ceiling is greatly improved downwards air flow definitely plays a part. My question is would there be any benefit to running the 195deg thermostat, will it improve that heat soak ceiling? My thought is that there is no point switching to the 195deg since the ceiling is way past 195deg and Tstat would be fully open just as much as a 180deg at 220f, so it wont help it run any cooler as per the mechanic wisdom that a hotter Tstat is better when the cooling system is undersized. Going to the 195 will also keep me from the benefits above preached benefits, some which are debatable, when temps are mild 70s and low 80s where the car can bring temps down to 205-210. Is the above statement inaccurate, and a gradual opening of the Tstat gives the 195deg doesn't fully open till later, hence cooling more efficiently in an undersized system?

Is there something I'm missing from my theories, or will the 195 provide a more stable coolant environment given my limitations in the system. Will it provide better results when at the ceiling and allow the system to run cooler in extreme circumstances like road racing etc. GM runs the corvette very hot right from the factory, is it so they don't need a million coolers to overwhelm an otherwise small system for the HP they produce?

Let me know your thoughts.

Popular wisdom, from DD himself, says you should reflash the chip in your computer to tell it there is a 180 thermostat in there. Otherwise the thermostat opens at 180, the radiator then heats up and the fans don't come on till 195. The end result is your car will run hotter because the fans are starting up at a disadvantage. 220f is actually the ideal temp for the engine to run at for efficiency and that is the result with the 195 with stock computer fan triggers. I have a 180 in my car with a stock fan, the computer has been adjusted and overheating has never been a problem. Unless I am in stop and go traffic on a really hot day, which never happens anymore.

I don’t have a stock fan, I have a MPIC and two 10” electric fans. But as I mentioned the radiator is heat soaked and I cannot go lower than. 220 when full demand. The fans are scheduled to go on at 195 and turn off at 185 which it does when the ambient air is cooler. So spring and fall is fine.
The question if a 195 thermostat is worth the trouble in my case will it improve summer? My thinking is that either thermostat would be fully open. So there is no point, or will the 195 stabilize temperatures that’s high up?

Put the radiator out in front of the IC and Condenser.

Thanks Chris and external aux or oil cooler is in my mind, but trying to debunk the thermostat theories of one running hotter than the other.

I spend several hours reading online. And basically there are always two camps to thermostats and fluid thermodynamics.

One side says Tstat only crates a floor for which the engines temperature to operate, therefore 180 and 195 makes no difference if temperatures are at 220.

The other side says the thermostat works as a restrictor and allows dwell time in the engine to pick up heat and radiator to shed heat.

Then the answer to that is that the cooling systems in a car is a closed loop system and it’s only limited by the radiators ability to transfer the heat. Running no thermostat would simply remove the floor for cold climates. And has no ability to cool the engine more than with the thermostat.

Then then the other camp goes on about restrictor plates in racing applications and how it lower temperatures etc. there is dwell time needed blah blah. I don’t know what is true or not anymore.

Ricardo,

I struggled with all the same questions and theories for years. In addition to what you are saying about people insisting that a restriction of some type is needed in the coolant flow to allow more time to transfer heat into the air, there are others who are doing the opposite. For example, the main reason people switch to an electric water pump is greater amount of coolant flow especially at low rpm like idling in traffic. The electric water pump kits that were developed for the SC motor had greater flow than stock water pump and were supposed to cool the motor better. So I don't know which is true. That said a bigger radiator and bigger fans always seems to help, and that's the direction I went. I also think a 180 t-stat and revised fan settings are needed.

BTW, the fans on my SC aren't flowing nearly as much air as my Hellcat. When those fans are running on high it's super loud. BTW, I'm running a 170 t-stat in that car and temps don't get over 195 no matter how hot it gets.

>thermostat works as a restrictor

I was taught that a certain amount of coolant flow restriction was needed to help prevent air pockets/flash boil around hot spots in the heads.

For a DD, the stat helps bring the engine to temp faster (emmisions/drivability), and then to keep the engine at a desired temp that matches engine scheme. If the engine runs outside spec. hotter or colder, the ECU will attempt to modify A/F and/or timing. We all know this stuff, but...

When I have a modified engine that is running well but the OE cooling system isn't able to handle additional heat, the first mod I consider is a larger radiator with a thicker core & higher CFM fan(s). I know that juggling stats is low hanging fruit, but I'm not sure it's that simple these days.

Yes the restrictor theories contradict the closed loop theories. While increase pressure in the engine circulation side might prevent some sort of hot spots from forming. If you allow the coolant to stay longer in the radiator common sense would say you are allowing more heat to build up in the engine so it negates it. This is why I’m trying to debate if the simple $15 dollar Tstat is a solution. I’m just trying to maximize and optimize what the car has but also no giving up on the benefits of cooler engine temperatures during the times of the year where the size of the radiator and fan become adequate and that’s below ambient 80deg. I would guess that both 180 and 195 are fully open at 220f would provide the same restriction, but if the 195 only partially opens and offers a bigger restriction vs the 180 and could provide better cooling due to dwell theories, then it warrants some exploring. It inverse could be said of this restriction is a problem then 195 might be a terrible idea and the 180 or no thermostat would be the right path to take.

Another point to make is does air the fan move more air when moving, does it stack the air flow or does it only flow what the fan is capable of? This is important when setting the MPH you want the fan to turn off. Again I have BE so playing with the setting are at my disposal.