Air inlet valve?

[Squall67584]

So in an effort to learn more about the D, I bought the service manuals to read over. While reading through the parts identification manual, I see the air inlet system page, and trace the air from the filter assembly to the source and see that it passes through an air inlet valve. What's the purpose of it? The duct with drain pipe seems like a great idea, but I'm confused by the inlet valve. Would the air be heated by the manifold stove for icy mornings? I'm assuming the cold air kits simply bypass the valve...

[jawn101]

So in an effort to learn more about the D, I bought the service manuals to read over. While reading through the parts identification manual, I see the air inlet system page, and trace the air from the filter assembly to the source and see that it passes through an air inlet valve. What's the purpose of it? The duct with drain pipe seems like a great idea, but I'm confused by the inlet valve. Would the air be heated by the manifold stove for icy mornings? I'm assuming the cold air kits simply bypass the valve...

The valve has a bimetallic thermostat style "flap" inside, that will blend hot air from the manifold stove with cold air from the vent intake to get a more consistent temperature air into the engine. In reality it's overcomplicated and ugly, and I'm not 100% certain why it's even needed. Maybe someone can chime in with an opinion on that.

Yes, the cold air intake kits just have you remove the pipe coming up from the manifold stove, the valve, and the cold air pipe and replace them with a single pipe straight from the intake vent to the airbox. You can then also remove the manifold stove if you choose. I left it.

[WelmoedJ]

I'm living in a sea cliamte country (The Netherlands).
In winter temperatures can go down to -10 ~20 degrees Celsius (14 ~ -4 F).

Even at 14 degrees F, my cold air inlet never gave problems starting the car.
I have to state that the car resides in a (non-heated) garage where temperatures never go below 46 F.
Leaving the car outside overnight while temps go down to 14 F, starting the next morning is just as on summer days.

The wax element in the said "ugly" heat stove and heat riser is not always working well.
This may cause heat from the exhaust mix with cold air and thus lessen the quality of your intake air and mixture.

[dmc6960]

The intake air valve does nothing to assist starting. All it does it provide hot(ter) air to the intake while the engine warms up. The idea was a quicker warming engine has better emissions control. While that is true, the function of the air valve is marginal at best. It really does not warm up the engine any faster than the engine does on its own. Any car you see with it still in tact has a major air intake restriction and a possibly malfunctioning unit which is providing at least partial hot air while the engine is already hot.

Another risk is the pipe leading from the heat stove to the valve can sometimes rub on the coolant line its next to. This will gradually file a hole in the coolant line. That = Bad. It caused a pinhole leak on my pipe. Did I mention this is the one coolant pipe no longer available NOS?

[jawn101]

There's also the issue of the paperboard tube from the cold air vent to the valve rubbing on things like the header bottle, etc. Mine was ripped clean in half when I got the car, meaning that no matter what the valve was doing only hot air was coming in to the motor.

[David T]

The whole air intake system on stock Delorean is very restrictive. Because of the size of the motor, I do not think it is all that bad though. The only way to know for sure is to dyno a car with it all hooked up and with it removed. One of the biggest restrictions in the whole air induction system is the air sensor plate in the metering unit. You aren't getting rid of that unless you EFI the motor! Looking at that plate and then the air inlet valve, all of a sudden that valve doesn't look so bad!
David Teitelbaum



There's also the issue of the paperboard tube from the cold air vent to the valve rubbing on things like the header bottle, etc. Mine was ripped clean in half when I got the car, meaning that no matter what the valve was doing only hot air was coming in to the motor.

[82DMC12]

I was told if I removed the air heater duct that the car might run a little rough when stone cold. I've never noticed it.

Think about it. The engine starts cold, and the heater duct thing is open to draw air from the exhaust manifold area. By the time the exhaust manifold is warm enough to really change the intake air temperature, the engine is warm enough to run just fine on the ambient air. The whole thing sounds like a slick idea but in practice I doubt it works at all. Sure does clean up the engine bay when you remove that stuff!

Andy

[dmcerm]

So what is the part number or description for that CAI hose that can be purchased from AutoZone or Advanced? I'd like to make this change this summer just to see how my car does.

Great thread. Thanks!

[EdR5150]

3 inch Spectre Air Ducting - $19.99

http://www.autozone.com/autozone/accessories/Spectre-Black-air-ducting/_/N-25h5?itemIdentifier=422454_0_0_

Cleans up the engine bay a little. Nice upgrade.

[dmcerm]

Awesome! Thanks. I appreciate your help... Rainy day tomorrow, looks like I have a mini project.
Thanks again!

Mark

[jawn101]

Awesome! Thanks. I appreciate your help... Rainy day tomorrow, looks like I have a mini project.
Thanks again!

Mark

You might find that you need a longer bolt for the clamp that holds the new cold air intake to the elbow inside the pontoon. My original one wasn't nearly long enough to clamp around the larger diameter of the intake. YMMV of course but I know I was annoyed that I couldn't finish the job without yet another trip to Ace :)

[David T]

The whole heated air intake system is NOT to supply warm-hot air to a starting, cold motor. It is to help the motor warm up faster once it is going. The reason is that a cold motor warming up is making more "bad gasses". The quicker it reaches operating temperature the sooner it is running cleaner. It's an EPA thing.
David Teitelbaum




You might find that you need a longer bolt for the clamp that holds the new cold air intake to the elbow inside the pontoon. My original one wasn't nearly long enough to clamp around the larger diameter of the intake. YMMV of course but I know I was annoyed that I couldn't finish the job without yet another trip to Ace :)

[dmcerm]

Good. That makes sense. My main concern when making a change is whether it will hurt the running of the engine or cause more problems than benefits. But if its just an EPA thing, and doesn't hurt the operation in anyway, I don't have any problem doing this small mod. Thanks.

Mark

[Mark D]

You should also enjoy a few HP gained from deleting the restrictive inlet valve...

I was pretty surprised at just how small the area inside the valve was even when at full "cold" position. I noticed a little throatier sound after the upgrade too.

[dmcerm]

My main concern with anything, as I said before, is whether or not this will make my car not run right. Are there any problems that could arise from making this one change? By taking out the inlet valve and just having the CAI tube, will the computer or other emission control sensors throw off my whole engine?
Just checking before I go for it. It doesn't sound like it's hurt any of the other owner's cars but I always feel mine is the exception. If it were to be off, what might cause it to be 'off' after this change and can it be easily fixed?

Thanks a lot!

Mark


The whole heated air intake system is NOT to supply warm-hot air to a starting, cold motor. It is to help the motor warm up faster once it is going. The reason is that a cold motor warming up is making more "bad gasses". The quicker it reaches operating temperature the sooner it is running cleaner. It's an EPA thing.
David Teitelbaum

[jawn101]

My main concern with anything, as I said before, is whether or not this will make my car not run right. Are there any problems that could arise from making this one change? By taking out the inlet valve and just having the CAI tube, will the computer or other emission control sensors throw off my whole engine?
Just checking before I go for it. It doesn't sound like it's hurt any of the other owner's cars but I always feel mine is the exception. If it were to be off, what might cause it to be 'off' after this change and can it be easily fixed?

Thanks a lot!

Mark

It won't change anything. Just try it, you'll see. Putting it back is as easy as reinstalling the valve and heater tube. Don't remove the stove from your manifold and reversing the process will take 60 seconds.

[dmcerm]

As expected, how did you all get the little elbow piece connected back onto the part that is just inside the pontoon? Then once I think I have that on and go to attach the other end to the air filter box, the other end come off again. And I cannot use the original connector that attaches to the element box with the new tubing... That original connector is slightly smaller and won't allow the new hose inside of it. Oh boy am confused now. Any pictures and suggestions... Am I missing something?

[Mark D]

No need to use the elbow where the duct enters the pontoon. The spectre duct end fits in the pontoon hole snug.

You will most likely need to trim the flexible duct by around 4 inches. Simply unthread the rubber end from the middle flex section, cut, and rethread the end back on.

I did this writeup a while back:

http://www.cardomain.com/ride/3341459/1981-delorean-dmc-12/page-4

[dmcerm]

Success! Sorry for the lamenting, I thought I had bitten off more than I wanted to chew.
I have the pontoon end on over top of the elbow piece that IS fastened correctly inside, and the wide end that connects to the element box goes inside that hole. It ain't pretty but I think it works and I still would like to get a hose clamp big enough to seal up the pontoon connection.
Does this look ok? Do you see something else I should do? I'm sure there are a few leaks but it is amazing the difference.
I am certain my inlet valve was stuck in the hot/closed position but for the first time in 11 years of owning car, I actually can actually feel air being sucked in the air inlet vent. It has to help, without a doubt!

Now I am just waiting on my K&N. Let me know anyways to clean or seal things up but other than that, I am happy the car is breathing much better.

Mark

[dmcerm]

Ok, I shortened the hose by about 3 inches or so. Put back on the original adapter off of the element box and secured the hose correctly around it and while I am still using the elbow down by the pontoon, I've decided to leave it the way it is now and just get a clamp to secure the fit properly along with a clamp for the connection at the element box.
Thanks for the link to your car domain explanation, your pictures and captions helped me with the details.
Can't wait to get her in the road tomorrow and test it out.
Thanks again!


10965
No need to use the elbow where the duct enters the pontoon. The spectre duct end fits in the pontoon hole snug.

You will most likely need to trim the flexible duct by around 4 inches. Simply unthread the rubber end from the middle flex section, cut, and rethread the end back on.

I did this writeup a while back:

http://www.cardomain.com/ride/3341459/1981-delorean-dmc-12/page-4