ACUITY
Senior Member
- First Name
- Russell
- Joined
- Jul 26, 2017
- Threads
- 2
- Messages
- 357
- Reaction score
- 699
- Location
- Baton Rouge, LA
- Vehicle(s)
- 2017 Si
I appreciate your experience making you apprehensive, and I appreciate the insight, but I'm afraid this is not all exactly factual. First, the coolant flow is reversed after the thermostat housing on the motor. That means water with entrapped air still passes the bleeder line to the overflow tank after passing through the motor and before going to the radiator. Second, because the water velocity is sufficiently high in modern engines, unless there are isolated cavities where air can accumulate (like often was the issue in older engines' heads etc), the air actually is entrapped in the water in most parts of the system, especially the radiator, because the bubbles can simply not get out of the way of the high-velocity water. Another important note is that you are not pumping the water "up" or "down" or anywhere. The water goes in a loop. This means potential energy of pumping up is always retained since the fluid will eventually go down an equal amount. You still deal with frictional losses and minor losses in turns, but the additional losses from our hoses are so low that you would not be able to quantify it without a very sensitive flow test rig. Granted, the gains are minor and do require other upgrades for them to get their full potential, but for the few people out there that have had consistent overheating issues at many hot track days, every gain gets them closer to a full solution. For street cars, we normally say that the hoses are unnecessary unless your OEM hoses are needing replacement, and then there is no harm and you get the advantage of silicone (namely, longevity in hot temps).Don’t do this to there are very good reason not one single car manufacturer does coolant flow through rad hoses this way. And slight loss I coolant the reverse flow will pump air through the cooling system. Instead of channeling air to the bleeder hoses built into the system you now pump air to the bottom of the radiator. Also if the car comes close to overheating the boiling coolant will not longer go to the top of radiator but get stuck cause water pumps can’t pump air downward. Another reason not to do this is the secondary coolant sensor to turn the fans on earlier. Half the radiator still ha colder coolant in it. This is an ineffecient way to cool. You’ll burn up you rad fans running them non stop unless you tune the fans to run off the primary sensor and not the secondary sensor. Plus you now pull coolant from the top of the radiator and cause heat tends to go up you get inconsistent temp control. By pumping from the top down through a radiator allows more time equalize temp across the rad having greater cooling efficiency. That’s what the factory routing is that way. The only thing your doing is turning the fans on earlier: that’s where the temp difference is coming from.
You will not find a single race car done by pros doing this. You will not find a single manufacturer designing cars running coolaht this way. Coolant out of a motor always goes to the top of the rad and pulls cooler coolant from the bottom. If this worked Honda would have done it already.
just get a grille don’t waste money on this.
I am an A class master tech. I’ve been building cars on and off 20 years. The potential gain does not our weigh the risk. Now instead of heating up slowly near boiling temps it will just sky rocket in seconds.
Before starting Acuity, my day job was to designing high-end heat exchangers for F1, LMP1/2, DTM, GT, Indy, and some military/defense/aerospace. We never ever worried about the flow direction explicitly, only the tank geometry to make sure air never got entrapped in tanks (which is partly a material strength issue due to temp gradients that air bubbles will induce in a cooling system) and having enough fluid velocity to counteract any buoyancy of entrapped air while the system is being purged.
Moral of the story: flowing cooling in the opposite direction on the wrong rad setup could hypothetically get you in trouble, but when an experienced cooling system designer is being mindful of why the OEM system is designed the way it is and what can be modified and what can not, it is possible to execute this with no negative repercussions.
Another important thing to note... Flowing any given rad backward will not net gains. We have gotten this question a lot. The optimal flow direction (thermally) has everything to do with the relative thermal gradients of the different heat exchangers in the stack and the resulting thermal gradient of the cooling air. So why did Honda not do it? Presumably because they did it the way they've always done it AND because on a stock car driving on the street, the gains of swapping it are very very small. You have to start pushing the car on a hot day, lap after lap, to get to the point where reversing flow makes any sense. People hate to hear this, but OEMs and auto manufacturers are actually incredibly risk-averse, and the result is they don't like to change things that worked in the past. If you don't believe that, look at Honda's shifter linkages back to 2000. Almost nothing has changed on them in 20 years.
~Russ
Thanks for the love! Agreed, the temp gain is really only advantageous to people who have fought overheating on the track in the past. If you've gone to the track and never overheated, you can probably get away with some good quality OEM hoses. That said, the silicone will outlast the OEM EPDM so if the OEM hoses go and you need new ones anyway, it doesn't hurt to get a little bit better cooling in the process too.When they released the reverse design I was intrigued by it. Russell Garehan, one of the Acuity managers is a Mechanical Engineer with years of experience in heat exchanger design especially in the high performance automotive industry. My money is on him designing something that won't damage our cars. He also did design work for Hybrid years back. At the end of the day though is a 2°C temp reduction even worth it when the page claims you need the other upgrades too? IMHO probably not.
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