How does a Grill Block help with engine warmup?

[Miller88]

My opinion is it helps because there's not air flowing through the engine bay. While there is no coolant going through the radiator (or at a significantly smaller amount), there is still air flowing through the engine bay.

On my Focus, with no grille blocks, and being driven very easily, it has a hard time getting above 160F coolant temperature. I can , however, grab the hose on the other side of the thermostat and there is NO heat and the radiator is stone cold. In fact, I drove it for about a half hour very easily and took the rad cap off. I could stick my finger in and it was very cold.

With the grille block, it does warm up a bit quicker. However, I have to be careful, with the COMPLETE lower grille blocked and the upper grille, it will get a bit toasty on long highway runs. Next year, I am going to leave a 2x3 opening in the middle grille, block the upper and monitor temperature with my netbook instead of the on board "engineering mode".

On my focus, a good amount of heat comes OUT of the top grille ... which is really odd. I originally blocked the bottom grilles when I used to do a lot of short trips, but didn't notice a huge decrease in warm up time ... when I stopped, I noticed that all of the heat was coming out of the top. With the top one completely blocked off, it heats up much quicker in the winter!

[RedDevil]

Grill blocking won't quicken the heatup *by much*, but it will reduce fuel consumption slightly because of warmer intake air. But you need to monitor as hot intake air can have adverse effects.

Some cars that have EGR don't benefit much from a hot air intake. I only detach my snorkel when around or below freezing. Without my LGB the effect is almost nil.

(* edit. I meant to write that, just didn't. Obviously hotter intake air will heat up the engine more quickly, raising the intake temp even further. As Vekke has shown with a full grill block it is substantial. Actually the greatest heat source will be the exhaust system, and the quickest to heat up too. It all comes down to how much of the air that is heated this way will find its way into the intake.

[Vekke]

I have done some testing at cold climate. That summer grill block already block over 60% of the grill but even still the fully blocked is much faster

http://www.youtube.com/watch?v=_Vx4ADTKS1g

In this video similar setup than in previous video, but now I started to drive immediately.
Now the blue engine temp light stopped in 132 seconds from the start with summer grill block on (about 8 minutes when car running in standstill). After 5 minutes inside temp was already at 0 celsius (10 minutes when car running in standstill). after 10 minutes it was over 10 celsius. Next test will be with winter grill block. That summer grill block works fine up to -10 celsius but after that its too cold inside to take out the winter jacket and gloves etc.

Winter grill block.

http://www.youtube.com/watch?v=EmH3xX6koWg

In this warm up video I have installed Tuneko Lupo 3L winter grill block in place. Weather is -18 celsius and it takes 110 s to stop the blue light which means engine is at +5 celsius (summer grill block 130s and in standstill idle 8minutes).

zero celsius inside temperature is reached at 3 minutes and 27 seconds. +10 celsius is reached 6 minutes 28 seconds (it took ten minutes with summer grill block to reach +10 celsius)

[olds455]

I'll try extreme differences for an explanation. Try to suplement what Old Mech has written.

1-If your radiator is completely blocked of airflow, the engine will heat up more quickly because the coolant will not lose temperature while flowing throught radiator (I know it will lose a bit heating the objects close by) and the engine would NOT have to re-warm it up, therefore the engine would continue to warm and would stabilze to a temperature more quickly.
2-if your radiator had air flow and reduced the temperature of the coolant as it passed through, then the engine would have to warm it back up. which sucks heat out of the engine and moves it through the coolant back to the radiator.

In situation 1 the engine WILL heat up more quickly to a stabilized temperture.

Another analogy is filling a bucket with water. Water is heat and the bucket is the engine and radiator system. Your goal is to fill the bucket with water (engine with heat). If you pour water into the bucket it will fill up. NO problem.
Now put a hole in the bottom of the bucket. The hole is the air flow through the radiator.
1-If you plug the hole (stop air flow through the radiator), the bucket will fill more quickly.
2-If you open the hole, (allow air flow) the bucket takes longer to fill because some of the water (heat) runs out of the bucket (system).

If you watch engine coolant temps through the UG or Sg, you can see the temp rise to just above the thermostat set temperature. shortly after, the temp drops a good bit (10 to 20 degrees in my car). After the drop the thermostat will close again until coolant temp rises back enough to fully reopen the thermostat. This cycle will happen a few times with the temperature drop being less and the time between high points being less and less until the temperature stabilizes.

I also use the grill block to increase the stabilized temperature. My car seems to like 215 or so, not 195 or much higher than 220. The higher and lower temps make it difficult to get high instantaneous mileage and therefore a higher trip average. I adjust the total front end opening to accomodate ambient temps. The electric radiator fans supplement if I get the opening too small and allow a damage free commute until I adjust the opening.

---that was longer than I though it woudl be. Hope it helps.

Scott

[t vago]

Originally Posted by RedDevil

Cars that have EGR don't benefit much from a hot air intake. I only detach my snorkel when around or below freezing. Without my LGB the effect is almost nil.

The Karen-Mobile seems to benefit pretty well from the heater core-based WAI I finally hooked up this past Sunday. Since then, ambient air temperatures have varied between 24 and 38 F, and intake temperatures have varied between 88 and 95 F. According to its UltraGauge, per-tank average FE went from 21.0 MPG to 26.1 MPG. I will do a fillup tonight when I commute back to home, and find out what the true per-tank FE will be.

Point being, the Karen-Mobile's engine is equipped with EGR, and it does well with a HAI.

[RedDevil]

Okay, I changed my comment to SOME cars. What I saw on my car was that the benefit gets lost when the temperature gets above 30 Celsius and gets significantly worse at 50 C. It is never much better anyway, except when lifting the intake temp above the 2C / 35F barrier. Strangely that seems to be a FE cliff on the Insight.
But not all engines are the same and EGRs will differ too.

[slowmover]

A grille block ought to be distinguished from a winter front (where the latter truly covers the heat exchangers and all other opening past the firewall into the engine compartment).

A grille block, on the other hand, only blocks air from the body of the vehicle, and even then may not cover all openings towards the heat exchangers.

That said, just the use of the grille block on my diesel pickup brings my warm-up temps higher in the 7-mile commute I have on days of around 45-60F. When colder, this variance is higher. I will see a 20F difference read on the UG upon arrival. The commute is mainly highway plus frontage road after a 1-mile start on city streets.

The aero benefit plays in the longer the drive. The colder the temps, but especially the higher the winds. A diesel makes this an easy choice (GB, plus the WF for the truly cold days).

When I use the block heater, I am at op temp prior to the end of that 7-miles on days of around 50F, with winds of 15-20-mph.

Without some way of decreasing wind speed against the heat exchangers the truck has a hard time getting above 120F on this commute in late fall through mid-spring (188F is op temp).

I would say that a DIY grille block is cheap enough not to have to worry over. It's easy to find the effectiveness, and then make/buy something better.

[campisi]

Well thanks, folks,for all the explanations and videos (and thanks to those who don't condescend in their explanations). I do, in fact, understand simple physics and I have at least a basic understanding of negative-feeback control systems and how they operate.
I have 'jimmied' up a quick grille block on my Forester and we'll see if it actually reaches operating temperature quicker than without the block. My original suspicion was that it would have to be VERY, VERY cold before a grill block would impact engine warmup times but now I have my doubts. I have a very good idea of how long (and where in my commute) the engine finally reaches op temp without any block so I can do a decent quick compare. If I think there's any difference I may do some more rigorous A/B/A testing for my own edification. I anticipate startup temp tomorrow morning of about 39 Deg F (so not that cold compared to what Mr Vekke contends with in Finland!).

[wmjinman]

I've been following this thread a bit with some interest, and in my mind, it's not solely related to the radiator because, as you keep pointing out, until the thermostat opens (to more than a trickle), the radiator isn't much of a factor anyway. But I've read an article once about how an engine gets cooled, and the radiator is only like 30% or so. I think more than that goes out the exhaust, a bunch is radiated through the oil & oil pan walls, while some is radiated directly through the block, heads, and intake manifold.

Now all this radiating that's going on will go faster if the temperature difference between the hot engine and the cold air surrounding it is higher. So to me, blocking the grille is like closing the doors & windows of your house on a cold & windy day. Even though your furnace would come on and keep your house warm (like the engine's thermostat), it would take longer. Blocking the grille allows more heat to stay in the engine compartment, slowing the rate of the engine radiating it's heat. (like closing the doors & windows in the house lets the furnace shut off sooner)

Of course, once the thermostat opens and the water flow through the radiator starts, it will be cooled less if the grille is blocked, too. So, to me, blocking the grille helps more of the heat from the fuel you're burning at the cold start stay in and around the engine than it would if a blast of cold air coming though the open grille was free to keep blowing it away.

So that would be my attempt to explain how a grille block helps the engine warm up sooner.

[olds455]

I can see the 30% from the way my car has reacted to some changes.

I started with the deep airdam with a hole and upper grill block. I adjusted the hole to get the engine temp I wanted.

When winter hit, I tried some insulation on top of the engine. It was cardboard with foil on the bottom where clearance was tight, and a piece of 1" foam board with foil where ever it would fit (all 1 piece). With the added "blanket", the engine temps went up. (back up since winter took them down).

I added a full belly pan later and the temps went up a bunch more. I had left an outlet very similar to the factory style "bottom feeder" cooling with the belly pan, so Airflow from the aridam hole through the radiator was expected to be similar.

I removed the blanket while leaving everything else the same and my cruising temps dropped from 230 and cycling the fans to steady 205 to 208 or lower at the same speeds and ambient temps.

I had similar reaction to a WAI. It incresed my engine temps again but increased intake temps too much and it was modded for a compromise.

I currently run a front air entry on a curved lead into the belly pan that is 2.5" by 14" and make 195-206 as long as I don't sit. I will make the smaller to get temps back to 215 at cruise.