98 S70 N/A: Airbox mod in the Winter Topic is solved

Post by **theWIFES_S70** » 15 Dec 2017, 22:21

Hey everyone, need to do a 900 mile drive to pick up the son from his first semester at college. When I dropped him off, the car was incredible on I-80--went 70mph the whole way and averaged 30+mpg. I've had the airbox mod on our car since Spring. Has really given our car some extra pep and I think it's a great mod for us N/A-folks.

I know Neil mentioned that he really needs his airbox thermometer up North, it's been unusually cold in the NE lately. Should I close this off? Does it keep the car "happier"? (Would make sense is that's the case because the airbox thermostat fails "closed.")

Thanks for the insight everyone.

Post by **scot850** » 15 Dec 2017, 23:32

The main issue I have read of is of the throttle body icing up if it gets really cold. Now why that should be any worse than on a turbo (so far I have not had that issue) I have no idea, other than the turbo has a longer way for the air to travel before it hits the throttle body.

Was your thermostat actually broken or did you just decide to jam it open?

Neil.

Post by **misha** » 16 Dec 2017, 04:58

You'll be fine up to -20 degrees Celsius...confirmed.

Post by **oragex** » 16 Dec 2017, 05:15

As above, mechanically speaking the engine should work fine with the warm air fully closed during winter days. I won't try the same in Alaska, though.

Not sure if P80 is the same, but on P2 this mod is tricky because it affects the mpg greatly if the flap is always left with the hot air fully closed in winter. What I do is fully close the hot air in summer in all driving conditions, while in winter I let 75% cold air 25% hot air when driving on highway and 25% cold air 75% hot air when driving in city. The sole reason for these adjustments is to get the best fuel mileage. Basically for the best mpg in winter, in city driving you need to let more hot air in while on the highway the engine needs more pressurized air so it needs more cold air in.

Post by **theWIFES_S70** » 16 Dec 2017, 08:15

misha wrote: ↑16 Dec 2017, 04:58 You'll be fine up to -20 degrees Celsius...confirmed.

Sounds good, thanks misha.

oragex wrote: ↑16 Dec 2017, 05:15 As above, mechanically speaking the engine should work fine with the warm air fully closed during winter days. I won't try the same in Alaska, though.

Not sure if P80 is the same, but on P2 this mod is tricky because it affects the mpg greatly if the flap is always left with the hot air fully closed in winter. What I do is fully close the hot air in summer in all driving conditions, while in winter I let 75% cold air 25% hot air when driving on highway and 25% cold air 75% hot air when driving in city. The sole reason for these adjustments is to get the best fuel mileage. Basically for the best mpg in winter, in city driving you need to let more hot air in while on the highway the engine needs more pressurized air so it needs more cold air in.

oragex, I drove around for almost two years without knowing that my airbox thermostat had gone out. I thought 17mpg was what the Volvo experience was all about! I thought But then I came upon this airbox delete mod and immediately, the car had more response and my gas mileage almost doubled. It really seems like we need to install a manual control for this flap somehow...

Neil, the flap was closed (flipped to hot) and the thermostat was oozing and rusty. I couldn't open up the housing so I just broke off the flap. And I've been cold air intake ever since!

As always, thanks for responses, fellas!

Post by **abscate** » 16 Dec 2017, 10:01

You don’t get these on turbos as the turbo heats the air up nicely, the the intercooler cools it back. Not a lot of point to regulating input air temp

Post by **oragex** » 16 Dec 2017, 14:42

theWIFES_S70 wrote: ↑16 Dec 2017, 08:15
Neil, the flap was closed (flipped to hot) and the thermostat was oozing and rusty. I couldn't open up the housing so I just broke off the flap. And I've been cold air intake ever since!

As always, thanks for responses, fellas!

It ruins the mpg indeed. If you completely removed the flap, I guess you have covered the rear hole that was going to the aluminum tube?

I wonder if Volvo sells the thermostat box

Post by **scot850** » 16 Dec 2017, 15:50

For the 99-00 they only sell you the lower airbox. Here from the dealer it is about $115 CDN (around $80 US). For the 98 they till sell the thermostat only.

Neil.