Bug Screens vs A/C Head Pressures?

[Archive]

Originally posted by Evan A. Beck

Try the fan test. You'll be surprised.

Evan, I have not tried the fan test, but I can tell you it sucks. It does not blow. For your fan test to be halfway realistic, you would have to have the screen in the rear of a fan. Try it with and without the screen, all the while holding your "hand" in front of the fan to feel any difference. Or, you would have to reverse the motor of the fan. Nuff said.

 

[CAM]

I run with my door screen on all year round , for the bugs mostly and for stones and pebbles occasionally. Notice no difference here.



Mike



I forgot , look at my truck pictures to see my set up

 

[Archive]

Originally posted by CAM





I forgot , look at my truck pictures to see my set up

Mike, I sure like your engine compartment!

 

[Bob Wagner]

you will have to rip

my bug screen from my bloody hands... .



I will <b>NEVER</b> remove my bug screen, except for periodic

cleaning



Doc, where's the bug screen poll

 

[CAM]

Thanks Rob,nice set up huh ?, I lost one of my pictures,suppose to have 4,I don't have a clue to what happened to it I'll have to get up w/my son to find out where it went . Mike







I just checked and now it's back again

 

[Doc Tinker]

Hehehe - looks like we got another debate topic



I personally don't like the idea of the screen. I'd rather clean bugs than have an overheating problem on the road, or have my a/c compressor lock up at 2500 rpm and snap the belt.



Go with the Stull grill, if you want to keep the big bugs out, and call it good enough.



Doc

 

[FDziurda]

I think many folks misunderstood my original question. I was concerned that screen "could/might" increase the A/C head pressures and was hoping we had an A/C expert who could comment on this.



I didn't throw my piece of screen away, I just removed it until I know more and understand the potential risks. I can honestly state that I haven't really noticed any significant increase in temps or performace. I ocassionally dig out my pressure washer and clean things up.



Thanks for everyone's comments.



Frank Dz

 

[Doc Tinker]

FDziurda, please reread my comment above. I did state a concern that the a/c compressor might lock up - I didn't make it clear that that's what could happen with excess head pressure though. At high rpm the serpentine belt we have on these trucks would probably snap. The old v-belts would smoke and squeal like a banshee from Hades.



I used to own a radiator shop and a/c service was ½ of my business. I agree with your friend, the a/c tech.



Doc

 

[Evan A. Beck]

Rob, what difference does it make?



The air that is passing through the intercooler, etc, is blowing across them, isn't it? It is not on the suction side, unless the truck is idling, or when the fan clutch is engaged... You know how that thing works, right? Just driving down the road at 60 mph, the fan clutch is not engaged, and therefore isn't pulling much air.



What I am talking about is the raw amount of "ram air" that has to go through the screen.



And by the way, I did the test with the screens on the suction side too... Same results--low flow.



Explain your "reasoning" for saying "to be halfway realistic, you would have to have the screen in the rear of a fan. "



The fan I was using was there to simulate the airflow while the truck is moving... It was not meant to be the fan in the truck... I thought you would have picked up on that. Guess not.



Don;t believe my tests? Well, why don't you get some initiative and try to prove me wrong. Do some of your own tests, instead of doubting mine.

 

[SteveH]

I agree 100% with Rob. I've used the wee little holed screens on diesels for 100k and have NO high EGT's, the thermostat while pulling mountain passes in Montana and Wyoming seldom goes to the right hand side of center, and the bugs were virtually impossible to clean out of the radiator before putting in the screen. Wind pushing at dead bugs push them further into the radiator and further plug it. Use whatever you want, these trucks have so much more cooling that they actually need it is unreal. I'll keep using the screen.

 

[KatDiesel]

Originally posted by illflem

I've run window screen on my trucks since new and have noticed no rise in temps, this includes intake temp, which also has gauge, sender on the manifold.

I would say this is proof right here? Actualy readings of temps, vs "Feel" of airflow.

 

[Evan A. Beck]

Kat, what about the proof I gave when I did the tests with the '00 3500 with a trailer? That's proof too.

 

[KatDiesel]

Originally posted by Evan A. Beck

Kat, what about the proof I gave when I did the tests with the '00 3500 with a trailer? That's proof too.

Sorry, I missed that, with all the posts screwed up with bold letters. I just briefly read this thread before work last night. I would say that "proof" that you provide is irrelavent to "my" situation which is to never tow a thing.



Whether or not one uses a screen is their personal preference. Its just like whether a fella likes a Ford or a Dodge. If you wanna use one by all means use one, those that don't... ... . don't and then everyone stays happy (in a perfect world).



I would say just agree to disagree and be done with it.

 

[Doc Tinker]

I might add that my Dad is a retired a/c, heating and aerodynamics engineer from Chrysler. Several years ago he took his mini-van to Alaska. I noticed in his pictures from the trip that he had a screen installed to the front of the van. Why did he put it on the grill and would putting it on the grill have the same effect as a screen placed directly on the condensor?



Doc

 

[Lordsman]

R-134a vs. R-12

Here's the specs on R-134a vs. old R-12 characteristics.



Discharge Pressure: +30 psi (Head)

Discharge Temperature: - 5deg. F.

Suction Pressure: - 3 psi

Refrigeration Capacity: - 10%

Superheat: - 4deg. F.

Energy Efficiency: Small Decrease



As you can see the head pressure is higher BUT the discharge temp is actually lower. Leave the bug screen on & keep it clean.

I have one and have no problems. Better to keep the bugs & debris OUT of the coil for optimum airflow & condensing.



Above specs are from SUVA(Du Pont) report on alternative refrigerants.

 

[drawson]

Air Temp

After following this I did some testing of my own. I like Bill (illflem) have run a screen from day one on mine and I also have an air temp gauge hooked into the manifold. My testing was done on a hill here locally that is a strait shot 5. 5% grade 1 1/2 miles long. This is where I do alot of my performance testing on. I did this at lunch today. all testing is from the bottom and full throttle, I run to 1400 Deg EGT only half way up the hill. I was letting of at 95 MPH . The outside temp as measured by my truck temp was 96 deg f



Here are the results...



With screen in place the air intake temp was 105 at the bottom and 135 when I let off.

I turned around pulled over removed the screen and let the temp come back down to 105 and then had at it again at the let off the temp was 130.



5 deg differance is much and the EGTs still climbed as fast and the point I got out of it was right at the same spot on the hill.



Here is my thoughts yes there is some restriction from the screen but I put it right back on. It isn't much maybe because up here in the high dessert our air is thinner. But the bottom line to me is that my 1997 w/ 110K on it, radiator, intercooler and A/C condenser look like new!!!! No bugs or rock dents. Rock dents and and bugs far outway the little restriction the screen makes.



TO each there own but I'll be running a screen.

 

[SteveH]

Originally posted by Doc Tinker

Hehehe - looks like we got another debate topic



I personally don't like the idea of the screen. I'd rather clean bugs than have an overheating problem on the road, or have my a/c compressor lock up at 2500 rpm and snap the belt.



Go with the Stull grill, if you want to keep the big bugs out, and call it good enough.



Doc

Hi Doc,

But have you ever had a heating problem because of a bug screen. I've run one in the hottest of weather every year in south Texas and never had a heating problem, pulling a 31 footer and grossing a little over 20k with 3. 54's.

Steve H

 

[SteveH]

Originally posted by FDziurda

I think many folks misunderstood my original question. I was concerned that screen "could/might" increase the A/C head pressures and was hoping we had an A/C expert who could comment on this.



I didn't throw my piece of screen away, I just removed it until I know more and understand the potential risks. I can honestly state that I haven't really noticed any significant increase in temps or performace. I ocassionally dig out my pressure washer and clean things up.



Thanks for everyone's comments.



Frank Dz

Hi FD,

You cannot separate the so called heating up problem caused by a bug screen and the air conditioner increase in head pressures. If I understand this correctly (and will surely be corrected if I am wrong) the supposed air conditioner head pressure increase is temperature related. The hotter it gets, the higher the head pressure. Too much oil in the air cond system can cause head pressure problems. Being overcharged can also cause this. Being undercharged can cause this. I am certainly not an expert in air conditioning and do not claim to be an air conditioner "know it all," but I am ASE certified in air conditioning.

Steve H.

 

[Doc Tinker]

Steve, I've never run with a screen. As a mechanic, I advise against the practice because placing anything over the front of a vehicle will restrict airflow to some extent. If I said it was OK, I would be irresponsible, especially if someone followed my advise and ended up with a problem. I guess it's an ingrained training, not to recommend something that might cause harm.



Doc

 

[Evan A. Beck]

Originally posted by Doc Tinker

Steve, I've never run with a screen. As a mechanic, I advise against the practice because placing anything over the front of a vehicle will restrict airflow to some extent. If I said it was OK, I would be irresponsible, especially if someone followed my advise and ended up with a problem. I guess it's an ingrained training, not to recommend something that might cause harm.



Doc

Well put!