Exhaust heat exchanger for cold start

[euromodder]

Originally Posted by Diesel_Dave

I can’t think of any downside to this.

Excess heat being pumped into the coolant ?

In order to work & warm up quickly, it needs to be close to the engine.
Thus it'll get pretty hot in a short while once the engine gets up to normal temperature.

Leaving the heat exchanger open on one end will boil the coolant in the heat exchanger, which then will go into the system to be replaced with colder coolant, repeating the cycle.

So you need to shut off the flow of coolant, but you can't close both ends or you'd have pressure building up - though you could possibly vent this into the radiator overflow (which might need more volume).

Putting it further back in the system will reduce its effectiveness to warm up a cold engine, as you need to wait for the exhaust system to warm up.


Another way is 2 exhaust paths - one over the coolant heat exchanger, one bypassing it.
That sort of system would need some critical pipe-work to make sure no hot exhaust gasses go over the HE when not needed.

[DonR]

I admit I stopped reading about halfway through the second page of replies, so forgive me if this has been suggested.

Use the air cooled VW engine defroster system.

Get a second heater core & put it in a box. Make an outer tube for your exhaust pipes, whichever ones you want. Recirculate the air from this outer tube to your aux. heater core via a small electric fan. You don't have to worry about over heating air. Shut off the fan when ever you want. Insulate anything you think is prudent. I wouldn't insulate the exhaust pipes, as that normally makes them rust something fierce.

Don

[Diesel_Dave]

Right now I'm thinking that the best idea would be to put put a copper coil into a short piece of straight exhaust pipe. That way it can be easily moved in and out. In the winter I need nowhere near the cooling capacity of my radiator, so a little extra cooling load isn't going to matter at all. If I'm running too hot in the summer I can just take it out. I don't think that will be the cse because this summer I ran with an upper grill block in 100 F weather and never had a problem.

This also would mean that I wouldn't have to worry about any vlaves or controls--I like that. I'm thinking some heater hose, some copper tubing, a short piece of exhasust pipe and I'd be all set.

[comptiger5000]

Personally, I'd just do like a marine engine, and water jacket part of the exhaust system (manifold on non-turbo engines). Then, up-size the radiator and such accordingly, so you can leave the exchanger in the loop full-time (it should be the last thing to see coolant before discharge to the radiator when the t-stat is open).

[mechman600]

Diesel_Dave, does your Dodge have a DPF or is it a pre-DPF truck? If it has one, the last thing you want to do is cool the engine-out exhaust down. DPFs need as much heat as available, at all times. I have a feeling your truck doesn't have one, and if that's the case, never mind.

[Diesel_Dave]

Originally Posted by mechman600

Diesel_Dave, does your Dodge have a DPF or is it a pre-DPF truck? If it has one, the last thing you want to do is cool the engine-out exhaust down. DPFs need as much heat as available, at all times. I have a feeling your truck doesn't have one, and if that's the case, never mind.

My truck came with a DPF. Your right about vehicles with a DPF--you don't want to take heat out of the exhaust. In that case you'd want to put it after the DPF. There's still quite a bit of heat there, just not as much as up bu the turbo exit.

[mechman600]

"...Came with a DPF." Sounds like you've already done the deed (DPF delete). My buddy at work did a DPF delete on his Dodge and improved fuel ecomony by 33%, no lie. I really uncorks the 6.7s. Plus, it makes the VGT sound like a jet taking off! While doing that I would do the EGR delete as well to get a bit more. You wouldn't believe how much fuel those things dump into the exhaust to keep your DPF happy.

[Diesel_Dave]

Originally Posted by mechman600

"...Came with a DPF." Sounds like you've already done the deed (DPF delete).

Now, now, I didn't say that I took it off now did I?

I can honestly say that I still have my DPF. My EGR too....whether they're actually on my truck on not I'm not going to say--but I still have them.

[mechman600]

Excellent answer!