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Old 06-10-2018, 06:48 PM   #1
GeneralBurrito
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Default Should the pre heater hose inlet from the airbox be capped off?

So I did the flapper removal mod a couple months ago and put netting on both intlets to prevent large debris from entering the airbox. After driving for a while, I opened the airbox up today and the filter was still clean (other than the black marks it gets from trying to set it in place correctly). Should I keep the preheater inlet open, but kinda protected by the netting, or completely capped off in a dry place like California? Is it placed in a spot that would suck in a lot of water when it rains (if it ever does here)?
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Old 06-10-2018, 07:19 PM   #2
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IMO it doesn’t really matter. Whatever your preference.

If you have a belly pan in place there isn’t going to be much water splashing around if you would drive through rain.
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Old 06-10-2018, 07:23 PM   #3
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I should probably slap one on then, the original one disintegrated from being 30 years old.
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Old 06-10-2018, 08:09 PM   #4
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I never capped mine at all. Had no issues. This was on my winter beater too so... gnarly conditions.
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Old 06-10-2018, 09:23 PM   #5
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I had the flapper closed for a long time in my 245. But recently while I replaced the air filter I also made both air intakes cold air. The engine liked that. So I would suggest have both go to cold intake air. More air easier to suck in.
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Old 06-10-2018, 09:40 PM   #6
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Originally Posted by dl242gt View Post
I had the flapper closed for a long time in my 245. But recently while I replaced the air filter I also made both air intakes cold air. The engine liked that. So I would suggest have both go to cold intake air. More air easier to suck in.
Yeah the engine has been happy since I got rid of the broken flapper. More air seems like a good idea. I think I'll keep it open for air, a belly pan would be on my list of things to get, but not a priority.
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Old 06-10-2018, 10:01 PM   #7
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FWIW the belly pans are ~$27 shipped from Rock Auto / ebay.
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Old 06-10-2018, 10:56 PM   #8
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FWIW the belly pans are ~$27 shipped from Rock Auto / ebay.
Yeah, I was looking them up earlier and found the URO pans for around $27.
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Old 06-11-2018, 09:05 AM   #9
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I have one of the URO pans and it works fine. I did have to enlarge some of the bolt holes so they lined up, but that was a minor inconvenience IMO.
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Old 06-11-2018, 11:51 AM   #10
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Later models had the warm air intake on the airbox capped off.
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Old 06-11-2018, 04:27 PM   #11
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Snorkel to the airfilter box is a huge restriction even on a stock engine. Adding a second cold (ram) air intake hose will make a small but noticable difference.
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Old 06-11-2018, 04:32 PM   #12
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Cap it off to get only fresh air from the factory cold air intake. I don't remember the default position of the flapper, but you want it modded to hold against the heat pipe port, that way only fresh air comes in through the front port. After that it probably doesn't matter if it's capped, but it will look better if it is.
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Old 06-11-2018, 04:53 PM   #13
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Cap it off to get only fresh air from the factory cold air intake. I don't remember the default position of the flapper, but you want it modded to hold against the heat pipe port, that way only fresh air comes in through the front port. After that it probably doesn't matter if it's capped, but it will look better if it is.
What is the con of not capping it off and having another port for more fresh air though? The flapper is long gone because it was stuck covering the "fresh air" port. I removed it and the heater hose to then have 2 ports to suck in fresh air. They've both been covered in netting to prevent large debris like leaves and such from freely getting sucked in.
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Old 06-11-2018, 05:16 PM   #14
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I pulled that junknoff years ago and never capped it. No problems. Don't worry about it.
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Old 06-11-2018, 05:29 PM   #15
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Quote:
Originally Posted by GeneralBurrito View Post
What is the con of not capping it off and having another port for more fresh air though? The flapper is long gone because it was stuck covering the "fresh air" port. I removed it and the heater hose to then have 2 ports to suck in fresh air. They've both been covered in netting to prevent large debris like leaves and such from freely getting sucked in.
That's fine then. The only reason I suggested capping it was so you didn't suck in hot engine bay air.
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Old 06-11-2018, 11:46 PM   #16
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You use the long preheater hose to turn forward to the front of the car. From the preheater hose ending run a pvc or piece of exhaust pipe through the hole for an air intake on that side of the car. Two cold air intakes. This example is on a 93 245. So the preheater hose comes from the bottom of the air box on the left side. Then goes under the fan shroud and turns forward to the hole in the right front sheet metal near the headlight. I used the stock air intake elbow for the pipe to go into at the front.
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Old 07-21-2018, 09:14 AM   #17
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Quote:
Originally Posted by dl242gt View Post
You use the long preheater hose to turn forward to the front of the car. From the preheater hose ending run a pvc or piece of exhaust pipe through the hole for an air intake on that side of the car. Two cold air intakes. This example is on a 93 245. So the preheater hose comes from the bottom of the air box on the left side. Then goes under the fan shroud and turns forward to the hole in the right front sheet metal near the headlight. I used the stock air intake elbow for the pipe to go into at the front.
I know it's been a while, but would you mind taking pictures of how your intake is setup? My preheater hose was way too mangeled to use again, but I'd be willing to buy another hose to route around to make some good cold air intakes.
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Old 07-21-2018, 01:25 PM   #18
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Quote:
Originally Posted by GeneralBurrito View Post
I know it's been a while, but would you mind taking pictures of how your intake is setup? My preheater hose was way too mangeled to use again, but I'd be willing to buy another hose to route around to make some good cold air intakes.
If itís mangled then just cap off the heater hose inlet at the airbox and mod the thermostat to only suck air in from in front of the condenser.
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Old 07-21-2018, 01:37 PM   #19
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Quote:
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If itís mangled then just cap off the heater hose inlet at the airbox and mod the thermostat to only suck air in from in front of the condenser.
Right now, both inlets are open with netting to prevent large debris from entering the airbox. It's been driving with with a little more pep in acceleration, but I'm just wondering about ways of getting colder air instead of sucking air from the engine bay. I already removed that restrictive 90 degree pipe with the small opening to feed more air into where the actual airbox inlet is, which helped a little as well.
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Old 07-21-2018, 02:18 PM   #20
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So you removed the ram air trumpet and think that helped?

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Old 07-21-2018, 02:26 PM   #21
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So you removed the ram air trumpet and think that helped?

the 90 degree pipe that sticks out near the radiator? It seemed restrictive since it had like 2" inlet and a 3" outlet.
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Old 07-21-2018, 02:37 PM   #22
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Good thing you weren't on the design engineering team that made up these cars.

Venturi effect
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Old 07-21-2018, 02:56 PM   #23
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Good thing you weren't on the design engineering team that made up these cars.

Venturi effect
Well I can just put it back on, simple, no need to tease.
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Old 07-21-2018, 03:28 PM   #24
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So I did the flapper removal mod a couple months ago and put netting on both intlets to prevent large debris from entering the airbox. After driving for a while, I opened the airbox up today and the filter was still clean (other than the black marks it gets from trying to set it in place correctly). Should I keep the preheater inlet open, but kinda protected by the netting, or completely capped off in a dry place like California? Is it placed in a spot that would suck in a lot of water when it rains (if it ever does here)?
GB,

I'm interested in knowing about the Port to the Grill inlet side's flapper....If the thermostat is working, that means the hot air flapper is closed(after the car is warmed up)and the Port to the Grill inlet flapper should be open?
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Old 07-21-2018, 03:41 PM   #25
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Well I can just put it back on, simple, no need to tease.
Just saying seeing something like that should arouse your curiosity and provoke further thought and study, rather than ripping away at a system that obviously cost more to make than a $12 cone filter to make.

Ya Volvos have had cold air intakes, cones and thermostatically controlled warm air input since the 1970 140s so it's nothing new.

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GB,

I'm interested in knowing about the Port to the Grill inlet side's flapper....If the thermostat is working, that means the hot air flapper is closed(after the car is warmed up)and the Port to the Grill inlet flapper should be open?
The air box is designed to provide the engine with a supply of air at 80ļF which is the ideal temperature.

That said they run pretty well with it bypassed, especially here in Cali where it's usually somewhat warm, and / but there is the risk of the AMM getting fried if and when the air box thermostat gives up the ghost so defeating the system is a common hack.
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