if V-mounting is so great...
 

if v-mount of intercooler is so great, why does no OEM do it? what's the downside?

I v-mounted my intercooler and I had to get the radiator/oil cooler sandwich almost flat to clear the ground--it lies around 25 degrees from ground... (with fan, shroud, and oil cooler, it's almost 7" thick). Intercooler on the other hand is mostly blocked by the factory front sheet metal which I can't cut too easily without compromising integrity of hood latch, headlight mount, etc... I just can't imagine air going into the radiator OR the intercooler effectively at speed. even with ducting, I could see most of air being bled out through 0.5" gap between the intercooler and radiator (that's where air will be rammed and cause high pressure as I go up in speed)... am I missing something?

I think there are two key components to making a V Mount work:

1) A vented hood, this will provide negative pressure to draw the air through the intercooler.

2) A non stock bumper to allow large airflow and less severe mounting angles.

Ducting will help facilitate point 1 to occur through the radiator as well by venting under the car. Also i would be moving my oil coolers further up front and to the sides like the 1999-2002 RX7's.

Tom

I would imagine the OEMs stray away from V mounts due to cost. Most decisions they make are done off a cost benefit analysis.

am I missing something?

Sounds like it from your description of your v-mount.

First, you should get your oil cooler off the stack.
Keep them in the sides of the bumper like stock. If that isn't possible put a short oil cooler right behind the front bumper opening. I did that with FC oil cooler and it worked great.

Next- gap?
There shall be no gap. It needs to be ducted and shrouded to work well. Once air enters the front bumper opening at speed the air pushing to get in the bumper opening will force air through your radiator and intercooler. Most your cooling issues will be at low/moderate speeds when just your fans are pulling air through your radiator and intercooler.

The angle and sizes of your radiator and intercooler cores create a compromise that you decide the balance of. More upright angle on radiator will cool engine better, more upright angle on intercooler will cool intake charge better.

There is a lot of room ahead of the engine. You can get the radiator and intercooler core sizes that work best for you.

Here you can see HKS chooses to emphasize intercooler flow.
https://cimg6.ibsrv.net/gimg/www.rx7...7f77055029.png

Here you can see Knight Sports balances intercooler and radiator flow more.
https://cimg3.ibsrv.net/gimg/www.rx7...f5f0820c6c.jpg

RE Amemiya emphasizes radiator flow more with a very thick intercooler core to act as a heatsink for low speed situations (would work great with fan and/or vented hood).
https://cimg7.ibsrv.net/gimg/www.rx7...a5ed855b96.jpg

Greddy is similar to RE Amemiya, but includes a intercooler lower duct to help guide air into the intercooler at low speeds despite its shallow angle.
https://cimg5.ibsrv.net/gimg/www.rx7...3c928d5999.png

a better question is why do so few V mounts put the intercooler in the lower position versus the upper? the answer is complexity, even though it allows you to completely bypass the vented hood part of the equation... heat also rises, so if the fan is not pulling air through then the intercooler is heat soaking sitting on top.


but don't listen to me, i don't know anything.

The reason is because it puts the leading edge of the radiator at the bottom front of the car, which is where you hit stuff. Automakers are in the business of building cars that actually tolerate minor impacts without destroying the radiator. As good as it is for cooling, it's terrible engineering in the context of a usable car.

i actually put that backwards, and changed it to more accurately depict what i was getting at. i almost never see intercoolers at the bottom, which seems to be the most efficient place for it.

years ago kits were simplified to reduce "turbo lag", until we realized that it was a virtually nonexistent problem but we kept the traditions going.

Crash worthiness.

That and a V-Mount is a pain in the ass. You have to relocate or delete vital things like the battery, A/C, power steering, etc. etc. with several kits. Plus, you need to change the hood and create different ducting so it works properly, etc.

For a street car it has few advantages for an OEM to mass produce it on a car.

thanks guys. I appreciate your explanation with diagram blue. I think I will go back to normal vertical stack configuration. It seems like some engineering is involved to get it right, and often, when done not perfect, I can see how it won't be as good as the vertical mount. plus, it gives me reason to buy a shiny new radiator! :lol: I butched my current one pretty badly by welding bunch of crap to it.

has anyone try those decommissioned nascar radiators on ebay? one with built-in oil cooler. I could fit 28x19" radiator with built-in water-to-oil cooler, and curious whether anyone tried them. I'm trying to get away with side mount oil cooler to reduce nose weight and simplify plumbing.

yea reducing lag was another reason why I went with v-mount... it made theoretical sense to me by reducing charge volume, but I also heard otherwise in real life.

i almost never see intercoolers at the bottom, which seems to be the most efficient place for it.

Have you hefted a big radiator full of coolant?
Same reason we use Aluminum for radiators and intercoolers even though it is not nearly as good as Copper. Aluminum is still better than copper per weight.

In racing the heaviest components get mounted as low and centralized as possible.

has anyone try those decommissioned nascar radiators on ebay? one with built-in oil cooler. I could fit 28x19" radiator with built-in water-to-oil cooler, and curious whether anyone tried them. I'm trying to get away with side mount oil cooler to reduce nose weight and simplify plumbing.

Back in 2001 on my FC horizontal mount IC I used the Griffin Nascar 28"x19" radiator and the medium Isuzu NPR intercooler. I call it horizontal mount instead of V-mount because the radiator and intercooler each had its own dedicated sealed ducting though it was arranged like a V-mount.

As noted previously my FC intercooler was mounted low right in the front of the bumper opening. This worked well, though once I went to 26psi on my EFR 7670 it would have been good to have a thicker IC with more mass and a fan on it (as well as a vented hood).

Intercooler air enters the cut in the rubstrip. You can just make out the front mounted oil cooler. The oil cooler height is about half the front opening height. Air could flow right over it, but it does go through. I had oil temp gauge.
https://cimg3.ibsrv.net/gimg/www.rx7...6361175968.jpg

Here is how it looks in the engine bay. You can see the angle of the radiator on the backside.
https://cimg9.ibsrv.net/gimg/www.rx7...6e34c942d8.jpg

This is the duct that feeds the intercooler. Below is the duct for the radiator.
https://cimg2.ibsrv.net/gimg/www.rx7...8b20c3b1e3.jpg

Same shot with IC duct floor removed and bottom tray removed. You can see oil cooler.
https://cimg0.ibsrv.net/gimg/www.rx7...c26ab445fb.jpg

My set-up was biased toward radiator airflow as when I made it I was running 10psi on a very efficient 60-1 turbo and 350rwhp.
https://cimg9.ibsrv.net/gimg/www.rx7...8890cc5f3d.jpg

Packaging and cost reasons are why oem manufacturers tend to stay away from vmounts. Remember most of our modified cars have emissions and other accessories removed, making packaging a non-issue. It is by far a superior option over a front mount or stock mount.

Great photos. How have you found the V-mount without bonnet venting? Although I can see the merit in having a bonnet vent, my thinking was that you can avoid needing one by properly diverting and balancing airflow between IC and radiator on the cold/front side of the setup. After all, conventionally mounted radiators and intercoolers don't require the need to create low pressure zones via venting.

The set-up worked well enough up to 18psi. It would lose a hp or two on back to back dyno runs with no dyno fan and about 15hp on the 3rd pull.

On 10psi boost it would do 340rwhp fresh and drop to 325rwhp heat soaked.

With the dyno fan on it would stabilize after the 3rd run.

When I ran 26psi it could have used more cooling. A fan on the back side of the IC or simply a more massive IC core or both those and a vented hood. It would lose ~25hp peak doing back to back dyno run with no dyno fan and more power loss under the curve (~50hp less at 4,000rpm).

On 26psi it would do 420rwhp fresh and 390rwhp heat soaked.

With the dyno fan on it would stabilize after the 3rd run as well.

Fantastic info, thanks. I'm very inclined to give it a go without the vented hood. A 10" e-fan triggered by manifold pressure or air temp would be very simple and cheap to hook up.

That's fantastic info and pictures. Thank you. man.. makes me want to actually keep the v-mount... I was thinking about it and I can fit an aluminum angle between the intercooler and radiator to make the gap negligible.

did you buy carbon sheets and cut them? I can source 0.04 alum sheets easily and I have no experience working with composite sheets.. having real tough time cutting the sheets with my jigsaw without having my wrist bones out of alignment from all the f'ing shaking... :lol:

Yeah, I just bought CF sheet and cut it up. You gotta use Carbide bits (the ones that look kinda furry on the edge) as the CF eats regular steel jigsaw blades very fast.

I've had good success with metal snips, too. But, I was cutting much smaller patterns.

Even with a 1/2" gap between the IC and radiator you could easily seal that up with a high quality foam. This is what I used to seal up most of my custom v-mount set up.

Bulk Foam Block | Outdoorplay.com

Super durable and easy to work with. This stuff is really tough and you can make really complicated shapes easily. 170 mph+ and no problems what so ever.

hey long time! thanks man. How do you attach that foam to structures? do you just wedge it? I found this thing called gaffer's tape, and it's holding to radiator great despite heat cycles so far. It's rated to 200*F, so it's right at borderline. I haven't run it during the summer though. :scratch: how are things coming along?

Just cut it to be about double the thickness your sealing up, place it on the radiator then bolt down the IC. This foam is really stiff but flexible. It should be so tight there should be no need for the gaffer's tape. When you pull it out again it will look like a mold of the surface it was sealing. Makes reinstalling easy.

As far as my project I have to pull the motor apart again but it is put on the back burner. My youngest son is going through some major health issues and hobbies will have to wait.

thanks. sorry to hear about your son. hope everything turns out ok.