How does a Grill Block help with engine warmup?
 

Genuine question.
I see people post it all the time but it's not something I can see happening.

I have a UG monitoring my intake temperature. I also have a WAI that pulls air from directly behind the radiator. So, basically, I can watch the intake temp and it never moves from ambient temp UNTIL my engine reaches operating temp (190 Deg F) AND the thermostat opens which lets hot coolant into the radiator. Then and only then does hot coolant flow through the radiator. When my tstat opens I can see my WAI start to work in that the intake temp rises quickly. Until then intake temp is sitting at ambient.

Point is that nothing happens until the engine gets warm anyway. A grill block would do very little to quicken engine warmup, wouldn't it? I mean, if the radiator isn't trying to radiate engine heat it makes no difference whether there's air flow through it or not? Maybe in VERY, VERY cold temps it might make a difference in that there'd be less airflow across the actual engine rather than the radiator? Jes' wonderin'!

Grille blocks increase the temperature of the coolant leaving the radiator. Exit coolant temps vary greatly from summer, around 120 degrees, to temps below freezing where the temp can be as much as close to 100 degrees colder. That cold coolant sucks heat out of the engine when it enters the block, and the restriction to flow in very cold temps means it is moving slower in its circuit.

In severely cold temps you can probably keep the engine cool with just the heater core.
Less heat dissipated into the atmosphere means more heat energy to push the pistons for useful work.

Another factor is grille blocks tend to help aerodynamics.

regards
Mech

I'm still not getting it .... if the coolant coming out of the radiator is so cold then the engine will cool off AND the tstat will shut off and then NO coolant goes to the radiator thereby warming up the engine again. Seems like a grill block wouldn't make a difference in this control system unless the problem is one of the engine getting up to temp and then the very cold coolant bringing it back under temp over and over again. That would make sense in that a grill block might stop that from happening.

Not questioning the aerodynamic benefits of the grill block just the statement of fact that a grill block helps keep the engine warmed up.

Keeps as much cool air from getting into the engine bay as would without the block. The air not only cools the engine by going through the radiator, it also cools the engine by hitting it directly.

If the engine bay is warmer, the engine should warm up faster. If you keep as much air from going in there, the engine bay should be warmer.

-soD

It may be because the general air flow through the engine bay is reduced and so all the hot parts of the engine get hot quicker and that heats up the coolant more quickly?

It's a good question, and I don't know if anybody has done any AB testing.

I installed my block in order to keep the engine at a consistent temp. On the freeway the thermostat would close and sometimes the ECU would go to open loop briefly. This wasted a massive amount of fuel. I bet the increase in fuel economy I saw wasn't from aerodynamic but just the fact the engine would stay in open loop... Plus a side bonus is it protects the radiator from damage. I have seen many bugs splattered on it and a few dings from rocks...

With no block, in winter my engine often wouldn't get any warmer than 172ºF. With block, it stays between 182º-195ºF. Belly pan up front also helps. My belly pan came off due to snow damage and since then, both coolant and intake air temperatures have been down a bit.

It seems to be that forcing the air over, rather than through the engine bay means you get less cooling done at the Radiator.

consequently, the temerature gradient from "in at the top" to "out at the bottom" is lower, and you lose less heat from the block to the coolant (to get it back "upto temp" for going to the rad.

Warmup is mainly affected becasues you stop the colder air entering the engine bay and keeping the engine block cold.

as far as Ic an see.

that reminds me, better price up a thermostat!

On a cold start it takes some time before the thermostat valve to the radiator opens, but the engine does start to heat up right from the start.

The grill block causes less air to flow though the radiator. Therefore the intake takes in air that is heated by the engine, especially when in town.

I see this happen when I take my kids to school (I have a LGB but no UGB): Engine heats up, the air under the hood gets slightly warm.
Drop off the kids, get back into the car, intake air is 10 C above ambient initially.
Stays up at +5C while escaping from suburbcatraz.
Once out of town the intake temp drops to ambient as more air flows through the (stiill cold) rad.

The thermostat will not "shut off". It will restrict the outlet coolant flow which makes the coolant exiting the radiator even colder which exacerbates the issue with engine heat being lost to the now much colder coolant.
Try to understand this if you can, the cooling system is designed for the worst case scenario which is 120 degrees ambient, with maximum load, climbing a significant grade. Under this circumstance the coolant exiting the radiator will be about 30-40 degrees lower than the coolant exiting the engine and the thermostat will be wide open.

Anything less than that and the coolant exiting the radiator will be colder than 140-160 degrees. As I said before, and I have tested it which you can do also if you have difficulty believing simple physics, the coolant exiting the radiator is where huge temperature differences occur. In winter with very cold ambient temps and hypermiling that temp can drop to close to ambient, even below freezing under extreme circumstances.

Every degree you can add to that coolant temp by reducing the effectiveness of the radiator means more heat is available for combustion pressure versus heat absorbed into the cylinder walls.

Several new car manufacturers are doing this with automatic adjustable grille blocks. Thye would not waste the money if it was not effective.

regards
Mech

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!

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.

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)

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

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.

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.

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.

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!).

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.

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.

It sounds like you really want warm air before the engine gets up to full operating temperature.
If you really want air warmed by coolant before the thermostat opens then plumb in a second heater core off your exixting heater core plumbing and build an air intake for it.
Then your intake air temperature will rise along with your coolant temperature.

A radiator feed for the WAI does have some benefit in the transition. The effect of grill blocking/winter fronts however slows down the air entering the engine bay, That air will get heated up by the exhaust etc.; so if the intake feeds from the bay the temperature does rise more quickly, as was proven in earlier posts.

I'm thinking of rigging a movable "snorkel" (maybe the wrong term) that, in one position, pulls intake air from around the exhaust manifold, but then when warmed enough, can be moved away so it doesn't get too hot. Roughly similar to the cowl flaps on some airplanes. I'm thinking a metal tube extension that's hinged. The "heat" position would put the opening right next to the manifold, but the other position moves it a few inches away where it's just getting engine compartment air, not as severely heated by the exhaust.

wmjinman...that sounds neat. I picture a y shaped plenum. WIth one end close to the manifold, the other a bit away. Remember the old carburator warm air valves on the air cleaner snorkels...that amy be an automatic valve for your design.

Your idea certainly got me thinking. Now to find an old air cleaner...

I had plans for a rWAI that takes air heated by the rad but uses a ventilator and a heat switch to get fresh air from the OEM air duct (snorkel).
I think I may switch that around; draw air from around the exhaust with a vent until it gets too hot. But coming the hot season there's no hurry now.

Olds455 ... Whoa, yeah - just use one of those, maybe!!

My thought was a pipe with another movable pipe on the end of it hinged on a pin through the middle. The hinged pipe could be moved via a cable, like a "choke cable", to swing it closer to the manifold for more heat, or farther away for less heat. The pipe's open end would probably be cut on an angle too, so it could snuggle-up closer to the manifold.

I realize homemade moving parts in an engine compartment are asking for trouble though,, so the conventional warm air intake from an older car might just be the ticket!!!

I have seen something like this before in cars that strugled to meet emmissions that were built as late as the 1990s.

Sunday (no WAI) - 288.4 miles / 13.637 gallons = 21.1 MPG
Wednesday (WAI)- 363.9 miles / 15.292 gallons = 23.8 MPG

More realistic than what that UltraGauge junk reported out.

What is "too hot?"

Not entirely sure, but it seems I read on here somewhere that there's an "optimum" intake temperature (for that person, at least), and I'm thinking it was like 90 to 115 deg. F. I'm pretty sure you don't want the intake air to get TOO hot - detonation problems, etc. And I'm guessing air right off the exhaust manifold could easily get to 300 degrees F or more, which would probably be too hot.

Now, it could just be permanently positioned far enough away that it doesn't get that hot, but my thought is for fast warmup, have it so it can really snuggle up close at first, then be backed away. I would watch the "intake air temp." on the ScanGauge & move it away once it hits - whatever - 115, or??

Probably do some "A-B-A testing" to fine-tune it. . . .

Good points, all. I do not remember reading about any "optimum" temperature, as such, but pre-ignition / detonation are things to steer away from.

Preventing overly hot temperatures was one reason I went with a heater core-based heater, as opposed to an exhaust manifold-based heater. It'd be near-impossible to get 300 F out of coolant (and if you're getting that high a temperature out of coolant, you've got other issues...) Another reason was that it was easier to route coolant hoses than it was to route air hoses.

As for the actual temperature? Your guess is as good as mine. I do know that my truck seems to love 130 F as its intake temperature. I would go higher, except that might start wandering into pre-ignition / detonation territory.

Yeah, I think excessive intake air temperature is why they started putting intercoolers on turbos. Good to know yours runs well at 130, though. I'll move my target range's upper limit to there for my testing.

And your heater core idea is probably really good for cruising with a warm engine, but if your goal includes faster warmups, the benefit of warm intake air wouldn't start until AFTER the engine was already warm enough to have hot coolant in that heater core, would it?

And at the risk of being a kill-joy, if I understand right, keeping the engine nice & toasty even at low power levels, is one of our goals, right? So wouldn't the heater core air heater be undermining that effort a little? But the exhaust's heat will always be there, though, and isn't going to cool the engine down by having some heat sucked off it.

You reminded me... I still have these other books, from when I was interested in turbos: Forced Induction Performance Tuning, by A Graham Bell; Turbochargers, by Hugh Macinnes; Maximum Boost, by Corky Bell; and Supercharging, Turbocharging and Nitrous Oxide Performance, by Earl Davis and Diane Davis.

All of these books mention intercooling primarily as a method of cramming even more charge into the cylinders. The use of intercoolers is as a method of detonation control was mentioned as a secondary purpose (even if still important), because intake temperatures will rise as a consequence of being compressed by the boost device. The books note that detonation / pre-ignition becomes a concern when intake temperatures are well above ambient temperature, though (like around 200 F above ambient). Further, any boosted application could benefit from using an intercooler, it would seem. For instance, A. Graham Bell mentioned that even otherwise stock cars with mild levels of boost (as with an aftermarket turbo kit) can benefit from an intercooler, since he found that their stock ignition and cam settings would not need any adjustment due to boost.

This tells me that a 60 F rise in temperature is probably nothing to worry about for our warm-air intake ideas, but anything above that might merit a little bit of caution.

That is true. However, the engine starts heating up its coolant about as soon as it's started, and I have noticed decreased warm-up distances (which would translate into reduced warm-up times).

For instance, on my daily commute, I've taken the below measurements. The distances are approximate due to their being landmark distances from my house, but they do serve to point out that warm-up times are significantly reduced.

.	Stock	With WAI
Needle moves off bottom	0.9 miles	0.7 miles
UltraGauge reports 190 F	5.5 miles	3.9 miles

Using either coolant or exhaust heat, raising the intake temperature will also raise the combustion temperature, and will raise the exhaust temperature. Raising the temperatures in this fashion will raise the rate of heat transfer into the engine block, which will decrease warm-up times.

You could say the exact same thing with using the heater at full blast on an idling car. Since it's somehow able to keep operating temperature even at idle, I'd say there was still some available waste heat from the coolant to be used, especially considering that the idling engine does not suck in anywhere near as much air as that heater at full blast.

Good points. Actually, I have the Hugh McInnis book, too!! And by using a heater core, at least you don't have to wait as long for warmup as if you used the main radiator.

A few times when I had the heater going full blast, I was wondering if my wimpy-ness was costing me MPG. It probably was. :-/

The grille blocks on my Focus definitely help with warm up times. NOT because they are blocking the radiator, because it's not air moving past the engine block.

I hit the highway quick in the mornings. Running at 55 there's going to be a good amount of air running through the radiator (which isn't flowing any coolant since the coolant is cold) and past the engine block. Aluminum blocks don't hold heat as well as cast iron. I suspect that's why.

Makes a HUGE difference on the focus. Almost no difference on the Cherokee.