Getting more MPG's out of a non-hybrid with aerodynamic tech from the Prius?

[ridegsxr714]

I recently bought a 2010 Corolla S for these reasons, price, low available intrest rate, great fuel economy, looks and reliability (amon other reasons). The Corolla has a mpg computer and I can watch my fuel consumption as i drive and get my average mpg i have got in the mid 40's for hwy mpg's withe the criuse on going 60mph). I want to do some mods, but only if it lowers fuel consumption. One thing that i have thought of was replacing the stock Corolla S spoiler with the rear trunk lip spoiler (pictured below). The thought is that the stock spoiler may cause more drag and the lip spoiler may help the aerodynamics the same way the Prius' lip spoiler does. The Corolla S3 concept looks very aerodynamic in the trunk area.

I'd love to hear your thoughts on this and any other suggestions for getting more mpg's out of my Corolla.

[krousdb]

At 60 MPH, I would guess that you would see little difference. You would probably be better served by changing to the CE wheels and tires. You might drop by ecomodder.com and see what those guys have to say. They discuss aero mods on non-hybrids all the time.

[Fred_H]

Yes, get rid of that oversized spoiler. Just remember that at high speed against a headwind the rear end will get a bit light because of the increased aerodynamic lift.

If you have an accurate engine coolant temperature gauge and monitor it carefully, you can partially block the grill by varying amounts depending on weather and driving conditions. There are plenty of threads about that. If you have easy access to the backside of the grill, you can block it there so it doesn't affect the looks.
The principle behind that, is that it takes less energy to push the air around the car than through the radiator. Grill blocking also has the additional benefit of keeping the engine slightly warmer in winter, thereby reducing friction.

Nice flat wheel covers or wheels, with few spokes, also help a tiny little bit. But make sure there is enough airflow around the brakes to keep them fom overheating.

[patsparks]

My guess, and it is only a guess is the best thing you can do is fit low rolling resistance tyres, pump them up to the sidewall pressure, minus 2 psi on the back. A spoiler which is contiguous with the boot lid has to give lower wind resistance, but I think it would be minor. A block heater if you live in a cold climate would be good value. How about moon domes?

No mod works better than a driver behaviour mod.

[icarus]

Originally Posted by Fred_H

Yes, get rid of that oversized spoiler. Just remember that at high speed against a headwind the rear end will get a bit light because of the increased aerodynamic lift.

If you have an accurate engine coolant temperature gauge and monitor it carefully, you can partially block the grill by varying amounts depending on weather and driving conditions. There are plenty of threads about that. If you have easy access to the backside of the grill, you can block it there so it doesn't affect the looks.
The principle behind that, is that it takes less energy to push the air around the car than through the radiator. Grill blocking also has the additional benefit of keeping the engine slightly warmer in winter, thereby reducing friction.

Nice flat wheel covers or wheels, with few spokes, also help a tiny little bit. But make sure there is enough airflow around the brakes to keep them fom overheating.

I'm sorry, but you have the concept of grill blocking wrong. The reason for grill blocking has nothing to do with aerodynamics or "reduced friction"! The reason to block the grill is to allow the engine to warm up quicker (and indeed warm up at all!) and therefore run MUCH more efficiently. A ICE doesn't begin to run efficiently untl ~190f. The Prius struggle to get to that temp, even in warm climates.

Some benefit may result in doing the same with corrolla, but the effects would be less as the ICE runs all the time, and therefor gets and stays warm easier.

Icarus

[Fred_H]

Originally Posted by icarus

I'm sorry, but you have the concept of grill blocking wrong. The reason for grill blocking has nothing to do with aerodynamics or "reduced friction"! The reason to block the grill is to allow the engine to warm up quicker (and indeed warm up at all!) and therefore run MUCH more efficiently. A ICE doesn't begin to run efficiently untl ~190f. The Prius struggle to get to that temp, even in warm climates.

Some benefit may result in doing the same with corrolla, but the effects would be less as the ICE runs all the time, and therefor gets and stays warm easier.

Icarus

Hi Icarus, actually I understand the concept of grill blocking very well.
But the OP asked about the aerodynamics of a non hybrid car.
There are aerodynamic benefits from grill blocking on a non hybrid car.
So I told him about the aerodynamic benefits of grill blocking on a non hybrid car, because he asked about aerodynamics on a non hybrid car.

I had been doing grill blocking for about fifteen years on my former non hybrid cars also. In winter I had an increase of about one to two mpg with grill blocking, compared to without.

Yes, I admit that I neglected to also mention all of the other benefits of grill blocking on non hybrid cars, such as the slightly improved combustion efficiency during warmup, and the slightly reduced pumping losses. Not because I "have the concept of grill blocking wrong", but because I concentrated on answering the question that was asked.

He asked about aerodynamics. I answered about aerodynamics.

[Shawn Clark]

Grill blocking for aerodynamics is likely to be far less effective than for winter temperature control.

The OP is probably correct about the spoiler. Spoilers are for high speed downforce. If one is not running near/at/above triple digits the benefits are questionable...especially if you aren't trying to corner at such speeds. At 130+ mph (speed limiter removed...and a few other mods, had to use the tach to determine speed past 110) my 240SX was still accelerating and felt well enough planted. It had a small spoiler and very low Cd for the time (.29 in '91.)

The advice about pumping up the tires is not aerodynamic in nature, but most likely true for efficiency (minimizing rolling resistance.) Look at the placard pressures for the Corolla, then use the same pressure offset front to rear and use the sidewall pressure for the maximum setting. This might handle differently in wet conditions, so after changing the pressure drive cautiously until you have adequate feel for cornering/handling characteristics (as you would in a new vehicle or new set of tires.)

If your Corolla already has more than sufficient ground clearance then lowering springs might make some sense. (I'm more a fan of stiffer suspension.)

[icarus]

I suspect, though I have no evidence to support it, but I suspect that conventional grill blocking will have almost zero effect on fuel economy due to cleaner air flow. If you were to sculpt and install a "clean" front from front bumper to windscreen you might have some effect. On the other hand, the drag caused by air under the car would probably have a worse effect on drag. Of course, the ICE needs some air for combustion as well as some for cooling. The ideal radiator would be one that ran coolant through a thin smooth surface. The object of the radiator is to increase the net cooling area (fins).

So I contend that grill blocking might have some fuel mileage effect on a Corrolla, but the benefit would come from more efficient operating temperatures rather than any "real" aerodynamic improvement.

Icarus

[fuzzy1]

If you are really serious about aerodynamic mods, have you read up on the AeroCivic? The owner is a frequent poster on the hypermiling forums, and can pull 95 mpg at 65 mph. This may be an excessive mod level to apply to a new car, but you could pick up some lower level ideas from it.

[Fred_H]

Originally Posted by icarus

I suspect, though I have no evidence to support it, but I suspect that conventional grill blocking will have almost zero effect on fuel economy due to cleaner air flow. If you were to sculpt and install a "clean" front from front bumper to windscreen you might have some effect. On the other hand, the drag caused by air under the car would probably have a worse effect on drag. Of course, the ICE needs some air for combustion as well as some for cooling. The ideal radiator would be one that ran coolant through a thin smooth surface. The object of the radiator is to increase the net cooling area (fins).

Originally Posted by icarus

So I contend that grill blocking might have some fuel mileage effect on a Corrolla, but the benefit would come from more efficient operating temperatures rather than any "real" aerodynamic improvement.

Icarus

I never said grill blocking would work aerodynamic wonders, but it definitely has an aerodynamic effect. In winter probably about on par with ditching the oversized spoiler.

But anyway, aerodynamics or not: It works. It also works on non hybrid cars. And it's a good bang for your buck.


Optional reading:

The problem is not the turbulence caused by the grill on the outside of the car, it's the air that goes through the grill. Most of the air that goes through the grill then goes through the radiator, hits the fan, hits the engine and transmission, and whatever makes it around eventually hits the firewall.
So, most of the air that goes through the grill into the engine compartment is being accelerated (or braked depending on your frame of reference) up to nearly 60 mph before being dumped out the bottom. In contrast, most of the air outside the car flows much more smoothly.

The grills on the Corolla are around ten percent of the frontal area.


Mercedes E-Class Coupe – Slickest production vehicle in the world - CleanMPG Forums

Lowest coefficient of drag production car in the world

Mercedes engineers have succeeded in aerodynamically optimizing the body of the new E-Class, achieving an impressive Cd of just 0.24 making the E-Class Coupe the world's most aerodynamic series-production car.

To reduce aerodynamic drag, there is an all-new electro-pneumatically controlled grille closure shutter. Its development is based on the knowledge that the air flowing through the radiator and the engine compartment accounts for up to ten percent of a car body's total aerodynamic drag. The fan shutter allows the engine's cooling air quantity to be limited in line with requirements, thus saving fuel. In essence, this means that, when the engine is running under part load and requires relatively little cooling, the radiator grille is closed by a circular system of louvers located behind the radiator. For minimum cooling, the shutter allows just a small amount of residual air to enter the engine compartment, but opens completely when the sensors signal that more cooling air is required.

When the fan shutter is closed, the Cd falls by 0.013, which is equivalent to a fuel saving of up to 2% when travelling at 80 mph. The fan shutter is fitted as standard on the four-cylinder models and on the E 350 CGI BlueEFFICIENCY Coupe.

for more details see also The 2010 Mercedes-Benz E-Class: BlueEFFICIENCY Technology | eMercedesBenz - The Unofficial Mercedes-Benz Weblog


http://www.aeromech.usyd.edu.au/15afmc/proceedings/papers/AFMC00216.pdf

The aerodynamic drag coefficient of most passenger vehicles is

now around 0.3. The use of body shape and external detail
optimisation has led to this low drag coefficient. The remaining
areas of exploration and optimisation are the underbody and
cooling system. The cooling system of a typical passenger
vehicle contributes between 6 and 10 percent to the overall drag
of the vehicle [5]. Furthermore engine cooling systems are
designed to meet two rare and extreme conditions. Firstly,
driving at maximum speed and secondly driving up a specified
gradient at full throttle while towing a trailer of maximum
permitted mass. At all times, in fact the majority of the time, the
cooling system operates below maximum capacity while
incurring a drag penalty [4].

Car Aerodynamics

Don’t’ underestimate the difference in drag created by even small changes, an example is the Calibre 8v which has great car aerodynamics with a coefficient of drag (Cd) of 0.26, but the 16v, 2.5 and turbo Calibras have a coefficient of drag of 0.29, just because they had to open up the front grill to allow for extra cooling. Air entering through a grill, through a radiator and out underneath the car creates a lot of drag. Some manufacturers now have much more efficient ducting of the air to the radiator and ducting away through either the wheel wells or better still strategically placed vents out of the bonnet.

Efficient Radiator - Tech Articles - Stock Car Racing Magazine

Like many things in racing, keeping your engine cool is a tricky task wedged between making sure you have enough airflow through your radiator to keep the coolant within the proper range and taping off the grille opening to increase downforce and reduce drag. When you boil it down to its most basic precepts, it's about consistency (and saving yourself abuck in avoidable engine repairs) versus outright speed.

As a rule, you never want to give up any more grille area in the front of the car than necessary. Taping over the grille is one of the few ways you can improve aerodynamic downforce and also reduce drag on a race car. The best way to keep the smallest grille opening is to build the most efficient cooling system possible. That doesn't necessarily mean you can simply install a larger radiator, because if you cannot supply a steady, cool flow of air across every inch of the radiator's surface area, you are wasting its capacity.

Vauxhall Insignia ecoFLEX

The aerodynamics experts at GME optimised the Insignia ecoFLEX in many areas using traditional methods like adding panelling under the tank in front of the rear axle, which improves drag coefficient and increases downforce. They also partially closed the radiator grille to send more head-wind around the body for better aerodynamics.

F-150 GAINS FUEL EFFICIENCY AND AERODYNAMICS WHILE BEEFING UP TOUGH TRUCK IMAGE | Ford Motor Company Newsroom

Other areas that Ford’s truck designers focused included the grille opening, running board, side mirrors and doors. Conventional wisdom suggests that a grille opening needs to be large to maximize air flow to the radiator, but the size of the grille opening on the new F-150 was optimized to allow enough air into the radiator while blocking the excess to minimize drag.

http://autospeed.com/cms/title_Low-Drag-Car-Aerodynamics/A_109778/article.html

Combustion air is drawn into the engine, usually from near the front of the car. This air movement normally doesn’t create much drag but the flows of cooling air through the radiator do create a lot of drag. On a car with a front radiator, a huge amount of air enters through the cooling duct opening, is forced to flow through the radiator, and then spills out untidily underneath the car. This turbulent movement of the radiator cooling air increases the Cd figure by as much as 10 per cent. For example, the radiator cooling airflow accounts for 8 per cent of the AU Ford Falcon’s drag. This means that without this drag penalty, the car’s Cd would drop from 0.295 to 0.271! (Back in the days of the AU Falcon, manufacturers actually released data on their cars’ aero-effectiveness.)

The use of a radiator intake duct that retains attached airflow for at least most of its length will give the best flow with the least drag. Controlling the flow of air after it leaves the radiator core is also important. Ducting air out through the wheel wells is efficient, but even better is the ducting of the air out through the top of the bonnet. Many sports homologation versions of road cars have taken the approach, fitting special vents to flow radiator air out through the bonnet. However, care needs to be taken that this flow does not disrupt the attached flow across the upper surface of the bonnet.