Over the years the standard cooling setup for most high end builds is obviously v-mount. But It's gotten me thinking, with modern cooling solutions, is a V-mount still as necessary as it used to be on a 2 rotor single turbo car? 3 rotors and 4 rotor cars don't have the space to accommodate like a 2 rotor does, and it seems like they can get by without major issues (although I'm not extremely well read into the topic).

Now we have things higher flowing electric water pumps, more efficient radiators, high powered fans, better cooling of oil, more efficient turbos, cooler temps from those converting to flex fuel, etc, etc, etc. In 2025 is it still necessary to go v-mount?

I'd love to get input, especially if you have actual data and testing on the subject.

 

from what we have noticed, it is simply preference at this point. v mount is absolutely superior period. better temps in every respect. disadvantages being cost and "complexity". front mount is fine and other than air temps, very comparable in temp control. the deviation between the 2 may be more prevalent on actual track cars but for a street warrior, its not appreciable.

 

I'll Echo this. It really depends on what you plan on using the car for. If its just a street car, with the Koyo N Flow and everything else in good condition, you will be fine, just make sure all your ducting is in good condition and proper (including your undertray.) If you plan on tracking the car (not drag strip) then FMIC will most likely hinder your experience as you will need to run more cooling laps and V-mount would essentially be a must in those situations. If you can get your hands on some old school cores like the Apexi FMIC then those are the best overall for FMIC setups and cooling while not having to gut the front end. Don't forget to include oil coolers as part of your "cooling system." If you don't have an "R" model car with dual oil coolers stock, Sakebomb makes a great dual oil cooler hit now with thermostats that mount on the coolers, I can't overstate enough how important oil cooling is on these cars.

 

First off, many of the 3 and 4 rotor builds you see out there are garage queens and show cars that rarely get taken out and actually driven hard - beyond a couple of highway pulls or a run through the gears. Not that hard to keep the temps at a reasonable level. So don't interpret them as "getting by without major issues". They get by because they aren't driven enough to stress the cooling systems.

I don't think high flow electric water pumps improve cooling by themselves. The stock water pump has enough flow for your typical two rotor. The cooling gets done via the heat exchangers known as radiators - and oil coolers and intercoolers. Those are a more critical component of the cooling system than the pump. The pump might be more beneficial in a 4 rotor (and perhaps 3) due the longer coolant paths of those motors.

Fans are an additional control mechanism used to blow or suck air through the heat exchangers when the car is not moving. When moving, the fans are mostly irrelevant and act as an obstruction to air flow to some extent. Whenever you see a fan setup boxed in with aluminum and the only holes for the air to pass through are through the fans, you can bet that the fabricator doesn't understand cooling systems and air flow.

More efficient turbos and manifolds do benefit engine cooling and underhood temps in general.

Fuel, doesn't really make that much of a difference to coolant and oil operating temps as far as I can tell. Yeah, the internal combustion temps and exhaust gas temps may run a bit cooler when e85 or whatever is used but the engine is still designed to run at 180* to about 210* F so it might not make a big difference in actual coolant and oil operating temps.

 

thermal engineering and tech has changed near 0 in 50 years. Improvements are in the few percent range. Biggest change youll see now vs then that makes a difference is e85. allows you to run a much crappier intercooler/IAT's with e85 than you could before. but not a worse radiator/oil cooling setup. so a SMIC with a well ducted radiator is a much better setup than a FMIC if you have e85 available. VMIC is still better but is not the big leap it once was. Proper ducting is >>> than swapping from smic/fmic to VMIC. make sure the air is getting thru your cooling mediums and they will perform amazingly well in almost any scenario.

 

I dont think this os tnecessarily true for what is availabe non-classified, but we havent found a way to implement many of the recent newer technology to our cars.

For instance, there is a paint that reflects heat back into the atmosphere in the wavelength at which the atmosphere does not interfere so ot is cooled directly by the coldness of space for a larger thermal delta.

So far they are just using it to cool military aircraft and building roofs.

Another example would be heat pipe technology from microprocessors. One could heatpipe the intercooler to a larger heat sink like the body of the car or into otherwise dangerous places like the fuel system.

Also, I dont see much innovation with the technologies we already have in use. One could use a hybrid intercooler that was air to air and air to water or had an evaporative cooled air to water interface (well, some people use water sprayers on heat exchangers which is a simple example).

 

Interesting question that I’ve wondered about as well. I don’t think there have been any new fmic or v mount designs that have come out in the past 10-20 years. Everyone is running the same old designs

 

Actually, not completely true. In general, radiators and intercoolers have not changed as far as basic components, but dual row or dual bank radiators and intercoolers started becoming available about 10 years ago or so. I have a FMIC dual bank intercooler with a duct that runs to the front bumper that is has the surface area around triple the stock intercooler due to a larger size, increased thickness and the dual banks. You don't have to move anything to install it, and I added two Spal 300 cfm puller fans to increase airflow. Theses dual bank intercoolers have been discussed in the forum many times over the last 6-7 years by me and many others. Also, all of my piping and the intercooler are coated for heat blocking or heat dispersion, even the fins of the intercooler are coated for heat dispersion. Look at an old thread about thermal management from around 2019.

Mike

 

The reason dual row ic/rad are not common is that they are a very poor design. They are better than stock, but not by much.

 

Correct me if I'm wrong, but isn't v-mounting almost exclusively an RX-7 thing?

Most cars can get away with front-mounted intercoolers (which provide better intercooling) since their engine cooling requirements are less severe.

Most Japanese sports cars don't stock come with massive oil coolers like the RX-7.

On the other hand, all generations of RX-7 have a high need for cooling oil and water, but also have a fairly tiny front fascia, so for packaging reasons, the only way to get sufficient oil, water, and intake charge cooling is to use a v-mount.

If you add air conditioning into the mix, the situation becomes even more tilted into the favor of v-mounts.

I think actual race cars tend to have the intercooler and radiator packaged side to side, with both getting exposure to fresh air (and they're properly ducted, to boot).

But you wouldn't be able to do this easily on an RX-7, and even if you could, I question whether you could get enough cooling with the surface area available.

It's much easier to just use a v-mount, even though you lose some efficiency when you turn a heat exchanger on its side.

 

Where are you getting your information from? The Knightsport dual and my dual are made from quality IC cores from mainstream IC core manufacturers. I have had mine for 6 years with no problems at all. I did some IC efficiency testing 6 years ago using my dual, my older Greddy FMIC, and the stock IC. The dual was far superior to the stock (the surface area is over 3X stock too) and the dual bank outperformed the Greddy by almost 30-40%. I will try and dig up my data from back then. This was done with dual temperature sensors, an air source mimicking boosted air flow, and a hot air source with the air heated over 200 degrees F. I wasn't done in a professional lab, but the data was revealing. Here is Knightsports data on efficiency and surface area. Can you post your data concerning the poor design and the IC efficiency?

Mike

 

The u intercoolers are inherently bad from a thermo standpoint. The hottest air from engine gets the hottest cooling air (2nd layer) and on the second pass the precooled air then gets the colder air. You want Higher deltas for higher heat transfer. The pressure drop is higher and that curve on bottom is bad for flow. The increased density from 2 layers also probably hurts flow thru the cores. The duct is very nice on the kit though from what I can see.

I'll say that its ok if you are really handcuffed by stock airbox, stock battery, ac, air pump, ast, stock turbos, stock crossover pipe. Its an ok compromise. But if you're ok with minimal mods a larger frontal area smic with something like a Pettit duct is much better for less money

 

Tell me you haven't done engineering thermodynamics without telling me. Average differential temperature is highest plumbing them that way, the same reason you counter flow an air to water intercooler, this also gives you the lowest outlet temperature for that arrangement, it's not like PWR wouldn't have modelled their version the same way they model formula 1 coolers 🙃. It's the best option without compromising block temperature or inlet ducting or AC without chopping half the car apart if you aren't going to custom fab a V mount that works around AC, ducted cold air intake and actually has all sealed ducting.


If you calculate the cross section of the bottom section it's definitely not a problem, certainly no worse than a lot of end tank designs.

 

These U-mount are a marginal improvement over stock while costing close to V mount prices. What are they running now 2k USD? Plus they are a way different customer/use case than the thread op was asking about.

On the design - dual U pass is a poor compromise at best. A second pass of the intercooler is the WORST option/lever you can use when designing an intercooler. Higher cost, added complexity, added failure points added manual labor, to get marginally better vs a single pass. Just make the core frontal area bigger and you get better performance KISS. You'll find nearly 0 race teams, 0 oems, 0 amateur racers use a second pass intercooler because it makes near 0 sense. In 35 years 2 companies have thought this is a good idea. Knightsport (small boutique company and yes there is an extremely small % who could use this for a massive overpay) and scammer 1 and 2( i can use pwr name to sell an inferior product for a huge markup). Any engineer that would recommend this needs their tuition refunded.

PWR does make great products (amazing fit and finish) also sell cores and will make you an ic to whatever size you ask. These u mount ones seems to have been designed/commissioned by some random guy named marcus who was scamming people. Claiming 550-650hp for this kit with, 650 ps twins. some more info on this thread https://www.rx7club.com/3rd-gen-gene.../#post12594832.

 

Noone is claiming they make the most power. They don't cause coolant overheating and are significantly better than stock on a street car. Saying race teams don't use them is moronic, race teams don't use synchromesh gearboxes, don't fit 4 seats, don't fit stereo systems, don't fit catylists.

You can sook all you want but you made statements that are simply untrue.

 

Here is a good article on Indycar heat exchangers (turbo application).

https://www.racecar-engineering.com/news/micros-scope/

One interesting development is they dont use traditional tube and fin heat exchangers for radiators and air/water intercoolers.
They are using primary surface heat exchangers. These use microtubes of stainless or plastic supported by vertical guide/support plates.

 

Mezzo. they are the best on the planet (and off) right now. They are extremely expensive, in the entire FD to 10X FD's depending on the need. and even if you have the $$ their backlog is NASA and F1 so good luck. hopefully the tech trickles down but its not anywhere near the same customer base as rx7s right now.

a quote -

"On the Formula 1 circuit, Kelly said, one team buys between 20 and 30 radiators a year. The cheapest of those radiators sells for a little over $5,000. Kelly wouldn’t specify the top end of the prices for race car radiators. But he did confirm that a person buying a new pickup truck today would have to pay more than the price of the truck if he or she wanted to trade the manufacturer’s radiator for Mezzo’s highest-priced heat exchanger"

 

That $1.49 Pep Boys radiator cap is SENDIN me

 

You can state your opinion, state some facts, and give all the antidotal evidence you want (without actually owning one or using one) about dual pass intercoolers, but I can give you real world results on my own car, which cannot be discounted. On my still twin car with the stock intercooler many years ago, I would see AIT temps, on a typical hot summer day, rising up to 52-55 max C on full boost. When I replaced my intercooler with the Greddy SMIC in around 2006, with its own duct, I saw my AIT rising up to 47-48 C max on full boost. Currently, with my dual pass intercooler with its own duct, I never reach higher than 39-40 C at full boost. The difference from the stock intercooler to the dual pass is significant and even from the Greddy, well worth it in my opinion. These facts cannot be disputed, since it is real world and not simply someone's opinion.
Mike

 

They are certainly better than stock.