Grill Block Poll.
 

I have a grill block in my VX, nearly flush with the rest of the bumper, left an area about 3" by 4" open right in front of the radiator, simaler to the OEM grill block opening, I also closed over the fog lamp openings, I didn't notice any change, so I'm wondering if I'm alone in this.

I did my grille block at the same time that I was learning all the new hypermiling techniques.

While I certainly saw some significant gains during that time period (from 40mpg up to 48mpg) I can't attribute my gains to the grille block.

Just put a lower grill block on my BMW 325is this morning, and drove the car about 130 miles, mostly highway cruising at 80 mph, but also in some freeway commuter traffic and some in town.

So, results are highly subjective, at best preliminary, and based on the on-board fuel computer, which has been reliable in the past. That said, at highway cruise speed, the OBC indicated a mile or two better mileage over the same stretch of highway that I've monitored many times before, and the car "seemed" a bit smoother and quieter, presumably due to less turbulence. This is not a proper test, only a preliminary impression, so take it as such.

I'm still making assessments, But I put a GOOD grille block on, the bottom one didn't hold up well so I just left the top. It runs hotter, heats up faster, and seems to run smoother.

I don't know, but judging by how many miles I've driven and the fuel gauge position, I'd say that I'm getting between 22-25mpg's this tank. which is better than ever. More tanks will have to confirm, but since I'm on spring break and not driving, I'll say that that'll be a few more weeks :D

My car showed higher speeds (~3mph) during NC coast on hills, with grill block and passenger mirror delete. With all gaps taped or weather-stripped on the front end, and the other grill opening partially blocked, I now coast at 70mph where I used to get up to 65.

Faster warm up....

If I engine brake to a stop light - my coolant temp drops 20-30+ degrees otherwise...

I'm a beleiver
 

I installed a grill block on the Geo in mid Feb.
My mileage has improved, noticeably.
42 mpg when filled in Feb.
48 mpg when filled in Mar.
Halfway though this tank I removed the right side mirror and added one of the wide angle interior mirrors.
I am sure this helped but this was also only the last half of the tank.
After covering the grill, I was able to coast longer on several of my regular stretches.
There is a point in my after work drive where I cut the power and EOC till my exit.
I have been moving my begin marker further back since installing the block.
My best EOC before block was ~ .7 mile.
Now I'm up to ~ .9 mile
As for noise, the Geo is very loud inside and I can't tell a difference.
However there used to be a rattle/hum from the front left @ 55 mph, I don't hear that anymore. May be some piece of deflector material behind the grill is loose that no longer gets the wind.
So in response,
Emphatically,
Yes.
So much so that I purchased the VW grill block for my Daughters Jetta.
Now I just have to put it on.
S.

I installed the Matrix's grill block this fall as it was getting colder out. The mileage was plumeting and the next tank actually stayed the same or was slightly better and temps were continuing to go down. Faster warm up was also a big deal as the wifey likes comfort.

I put in an above-bumper, behind-the-grill block and immediately noticed 3 differences:
> The engine warms up about 30% faster
> The car is more stable (less nervous, slightly quieter) at highway speeds
> Coasting distance is noticeably longer even at moderate speeds (60 km/h).
So it works!

I did an A-B-C (admittedly not ideal) back-to-back test on a fully warmed up car and noticed an immediate improvement as soon as the block was installed:

http://metrompg.com/posts/photos/ACFBE8B.gif

http://metrompg.com/posts/grille-blocking-part-2.htm

now i gotta getta rear wheel skirts
 

Metro, I didn't realize the skirts had that much impact on your mpg.
I've blocked my torn bumper with duct tape and will make a permanent block in my new bumper, which is hanging on the wall of my garage btw. I must now go find the info on your wheel skirts so I can make my own, in my spare time on the second Tuesday next week.

Take that graph with a grain of salt. I haven't done A-B-A on the skirts on the Firefly/Metro.

That said, I believe that skirts are going to be most helpful on cars with short rear overhangs like ours - because there's less bodywork aft of the wheel arch for disturbed flow to reattach before separating at the back of the vehicle.

grille block
 

I believe CAR and DRIVER quantified an improvement for their "Crisis Fighter Pinto",back in March of '74.So many Big-Dogs have mentioned or recommended the practice over the decades,that I've always considered it an integral part of any streamlining project.Sorry!,I have no specific quantitative data for the solitary modification.If you'll look around,many new cars have fake grille openings.It gives the stylists busywork,and streamlines the car without the owner's awareness.

Good memory, Phil. The Car & Driver article states that the Pinto's grille, fully blocked netted a 2.6% increase in MPG at 70 mph.

The interesting part was: when combined with their giant air dam, the full grill block resulted in a 13% increase in MPG @ 70 mph.

With the area ahead of the radiator opened up, but the sides remaining covered, the MPG advantage was 9%.

Goes to show how aero changes are not isolated. Change the flow in one area, and it has downstream (and upstream, if done at the rear of the vehicle) consequences.


http://ecomodder.com/blog/wp-content...front-blog.jpg

Hard to tell
 

I made mine in concert with getting the ScanGuage, so technique over shadowed aero technology. I may take mine off for a week, and see if anything changes.

However, I recent added some baffles that restrict cold air getting to air filter inlet. Under hood air definitely has big effect on IATs now, and mileage was increased as a result. If I do take it off, I expect a drop not due to aero losses, but cooler IATs.

Off topic but this sure jumped out at me:

Photo in post #14 shows that the tires need more air.
General wisdom is that with radials you can't tell visually whether they're over- or underinflated. But when seen from front or rear and they bulge out where they meet the road, to me that means they need air.

Well, I was right, I got 22.56mpg. I can do better cause I was confused the whole time. check out the jeepin' build thread as to why, cause i don't feel like reposting it. I now know it helps.

i'm obviously coming in late on this one, but my packaging tape upper grille block has helped more than i expected. i haven't filled my tank yet to get any accurate number, but my jetta usually gets ~400 miles to a (14 gallon) tank. this is nice because every 1/4 tank interval on the gauge should be about 100 miles on the trip odometer. i taped up the grille about halfway through this tank (~200 mi), and now at the 1/4 mark, i've gained 35 miles over where i would normally be (335 vs. ~300).http://ecomodder.com/forum/member-vw...aging-tape.jpg

before i added the grill block i was averaging 30-33mpg combined driving. after i installed the block i hit 35mpg for the first time with the same driving routes and techniques(with an auto transmission).http://i183.photobucket.com/albums/x97/imokrs/A0393.jpg

I did a partial grill block on the explorer and removed xbar on roof rack at same time. I have seen around 2.5-3 mpg improvement. I feel the grill block is mostly to credit I did one drive with xbar off and saw minimal improvement maybe .5 mpg

I noticed the grill block reduced warm up times, but didn't notice an improvement in MPG. Too many other variables at play that any improvement would be lost in the noise.

Will have to agree. Warm up is ridiculously fast now yet watching torque the temps don't seem to get excessive at any point. My explorer guzzles when it's cold.

The four-piece grille block for my Cummins-engined pickup is what I install for temps above 41F (below that is the full coverage MOPAR under hood "winter-front") and depending how high ambient temps are (and whether I hook up the 35' trailer), it helps in warmup, but more importantly keeps coolant temps higher when lightly loaded on the highway.

I leave the upper two pieces in place during hottest months. I was advised by a Cummins engineer to not allow higher than normal op temp; will admit I sorta cross that line, but not in a serious fashion.

I believe that mpg improvements are marginal, but faster temp rise -- and temp stability -- make it worthwhile.

Mine is cut from a heavy plastic. Uses two short bolts, fender washers and wing nuts per piece to hold against grille.

.

I'm starting to become a believer. I have a first generation Passat/Dasher and it runs cold. The third genneration Passat had a nose that looks like this:

https://upload.wikimedia.org/wikiped...t_20071205.jpg
https://en.wikipedia.org/wiki/Volkswagen_Passat#B3...

The VW emblem is hollowed out for a snorkel. I think I can reproduce that look with a piece of sheet metal and a Mexico Beige rattle can.

I am going to re-do my grille with this stuff.

https://images-na.ssl-images-amazon....oL._SY355_.jpg

It's a 3' x 3' square of black aluminum perforated 20 gauge sheet. The holes are 1/8", and it has 40% open area. Hopefully, it'll give about as much improvement as a corplast sheet at low speeds, but allow more airflow than corplast at highway speeds.

That's the stuff I want for a Kammback visor on my lift-back rear window.

Unfortunately, that "grille" becomes OPAQUE to airflow at higher speeds, slowly approaching a solid blockage eventually. It's sorta like *how* the holes in microwave oven door/window screens stop the microwaves from coming out and cooking YOU.

Isnt that what you want?

My cars front area is like that. Could they have designed it that way one wonders. If that is the case, i have new found respect for the engineers.http://www.mercedesmedic.com/wp-cont...od-release.jpg

That's what I would want. City driving is when you need better airflow due to start stop. Highway your really not using that much power therefore not generating a lot of heat

An example of 'vena contracta'. I'm thinking at right angles to the flow at the rear of the roof it would be a non-issue. Maybe a piece of perf metal painted body color for my grille block?

So, is me building a grille block a stupi idea?

Not a stupid idea. Upper grille blocks from my following of others experiences along with my own seem to be more effective. If your in a cooler climate it's a great idea. It will reduce warm up time immensely. Also really depends on your vehicles. Time of year may also dictate whether u can use it as well if your in warmer climate. Always make it easily removable and have a way of watching your temps other than the dummy guage on the dash. Right now where I live temps are in the 70s by 10 am typically. Been in the 90s and I have had no issues with my grill block. That in itself is due to the fact I only did a partial block. Will do more in winter months. Anyways vehicles are developed to be able to keep themselves cool in the worst case scenario. Like driving up a 20° grade in death valley pulling a trailer. Maybe a bit excessive but you get the idea. If your driving ecomodder style you should be able to get away with at least a partial in any climate.

Same here. It *might* be helping, especially in the winter, but so much else has changed since I started getting serious about MPG.

I took all of my grille blocks off a few weeks ago because it wasn't taking long to reach operating temp and trip the radiator fan at 90-100°F ambient. Back to focusing on driving techniques to eke out gains until it gets cold again...

Welp, my grill block (lower -- there's only a small slot below the hood left for air flow) didn't cause me any issues yesterday, when it was 90-something degrees. Temp gauge never moved above it's usual half way mark. Nor did it on a highway climb up the mountain to get out of this town a couple of weeks ago. This is on my Firefly.

The cooling fan comes on when you stop moving. And it certainly aids warm up time the rest of the year!