Maybe try mud flaps on opposite sides in front of the wheels?
Maybe try mud flaps on opposite sides in front of the wheels?
The aero mod suggestions got me thinking...so I did an experiment.
I went ahead and dataloged my commute this morning with the intention of recording a bit of drafting behind a semi truck. Of course this is dangerous and all, but in the name of science I took the risk. Anyway, I drafted for a mile or two at a reasonable distance. The data suggests a huge improvement can be realized if I mount a semi trailer in front of the car...
Hard top, grill block off panel, some skinny tires? and some cardboard. I can temporally pull the mirror from the passenger side but The drivers side mirror has got to stay....Stay tuned for the results.
Meanwhile....
The grill block off panel will more than likely cause some issues until I can get the hole sizes sorted out. The current Miata temperature gage sucks..... so the Megasquirt is being outfitted with an alarm that will sound if the engine temp gets to high.
3.57 main board doesn't have proto space, however it has a DB15 connector that can be customized to suit unique applications. Two output signals were routed to the DB15 One is the temp alarm wires and the other is throttle position alarm. The TPS alarm is for another project I'm working on.
This little gizmo is an active alarm buzzer thingy. It just needs 5V and ground to make noise. TunerStudio has a utility to allow the user to program outputs based on engine sensors. For the temp alarm, I rerouted one of the LED indicators through the DB15 and to the alarm. Works perfect!
Stay tuned!
Keep up the good work. RE aero, try to get any front tire that pertrudes beyond body panels covered.
The tire portion is going to determine whether you want to hypermile this thing or have a good handling sportscar. I vote hardtop and aero mods but go no smaller or taller than stock tires. I mean you could probably drop to 13s with a 65 profile tire and pick up a MPG or two but it just wont handle worth a flip.
My $0.02.
Find any of these on craigslist yet?
Keep it up!
thanks Ross!
This weekend is NASCAR weekend and all the local roads will be clogged 
. I figure I can sort out the grill and engine temp problems in the next few days but to test anything else will have to wait until the NASCAR folks go home.
In reply to crankwalk:
Yeah, I agree the skinny tires are unrealistic and would look like E36 M3. I will try them in the name of science but have absolutely no intention of going that route.
What BMW did with the i3 is very interesting: a tall but very skinny tire allowed them to have low frontal area but not suffer in regards to contact patch size (it got narrower, but longer).
If you add on a CB radio, you can hear the truckers talk about how much they hate you drafting. My volvo was the conversation topic many of times.
Had some time this evening to do a few experiments with the grill block off panel. The temp was about 85F with moderate humidity. The Megasquirt temperature alarm was set to go off at 215F. Overall it was great weather to make a car overheat....... let's take a look.
NOPE! the car overheated within 5 miles. I was able to safely drive back to headquarters with the cooling fan on and the heater running full blast.
A quick modification to the panel and the experiment continued...
Panel back on the car and some more data was collected.
With this panel, the car ran at 212F with the cooling fan on while going 80 MPH on the freeway. Not ideal but getting close. On surface roads the temp hovered around 195F with the cooling fan on. The fan could be shut off for a min or two before the temp alarm would go off.
Stay tuned!
Neat. Maybe mount the panel with some quarter turn fasteners or something so it can be easily removed on the side of the road without tools, just in case?
In reply to Run_Away:
good call!
Something like this may work perfectly...
In reply to Doc Brown:
So what temp are you shooting for? Or a better question- do you know what temp the fan turns on? FWIW, you need to keep the temp below that point when moving- we've taken some data showing that the fan costs a lot of fuel economy.
Also, in terms of experimental blocking- have you tried putting the pattern closer to the radiator? Perhaps the turbulence behind the blocker is causing the air to not flow over the radiator core. At least block off the flow from the sides to prevent the flow reversals caused by the low pressure of the blockers.
In reply to alfadriver:
The goal was to establish the minimum acceptable size opening that would allow the engine to cool itself without the electric fan. These past few days provided the worst case scenario with ambient temps in the 80's and 90's.
This is the finial modification to the panel.
During the experiments, I manually turned on the cooling fan whenever the temperature alarm started beeping. The alarm was set for 215F. During the hottest part of the day on Saturday the alarm went off a number of times and I switched on the fan for a min or two. During the cooler part of the evening the alarm never went off.
At this point I'll need to modify the megasquirt harness for fan control and I'll set the limit for 212F. This should keep the fan from turning on unless absolutely necessary.
Stay tuned!
Ive read some interesting stuff on bellmouths and inlet and exhaust shapes/cuts and how they can have a huge effect on flow. You may be able to use a smaller opening to acheive the same flow by shaping behind the plate.
Just an idea.
I saw the post about fiddling with the cam timing, but didn't see what the results were. We've had a Metro MPG project for the last number of years and picked up some decent results running more compression, less duration, and advancing the cam. 108 degree intake centerline seems to be the sweet spot for us, and we regularly see 65 (US) MPG. Aero is huge, and in our case, mirrors make significant difference.
Where did those mirrors come from?
Mirror. There's a mirror delete plate (gold to a Metro - head) on the other side. Stock Metro/Firefly/Sprint.
If Alfa is right about there being turbulent flow behind the block off plate, I wonder if you might explore using velocity stacks to straighten flow to the radiator.
Edit, I just realized I'm talking out of my ass. Don't listen to me. 
In reply to Zomby Woof:
I'm a complete moron when it comes to the cam timing. I fiddle with the timing back and forth looking for a sweet spot, apparently never happy.
I'm not sure I can do much about the duration, but you reckon I should be focused on advancing the timing?
I would. Increase cylinder pressure. Without knowing where it's phased, it's hard to say, but about 4 to 6 (crank) degrees will put you in the range
Tell me about the stock cam, what is it? Rockers, roller, hydraulic?. I might be able to do something.
In reply to Zomby Woof:
The camshaft is a roller from a 94 Aspire.
I switched over to the roller cam a few years ago. The original cam was a non roller and apparently set up for EGR effect. I'm not sure if switching to the roller cam made any difference but it seemed like a good idea.
Doc, Once you sort out your minimum opening for the grille block off, look at the effective percentage of open area to total original open area. You should be able to get more consistent cooling by spreading the open area across the entire original opening by using lots more smaller holes (based on the percent open area calculated above). The increased spread of the open area will help with the turbulence/recirculation mentioned in posts above.
perforated sheet
If you get really crazy why not use your new temp buzzer output to drive a small motor that opens an adjustable grille system.
I have a little time with cooling and aero, so PM me if you have questions.
stafford1500 wrote: If you get really crazy why not use your new temp buzzer output to drive a small motor that opens an adjustable grille system.
IF? I think the Doc has passed that crazy level long ago.
2002maniac wrote:stafford1500 wrote: If you get really crazy why not use your new temp buzzer output to drive a small motor that opens an adjustable grille system.IF? I think the Doc has passed that crazy level long ago.
LOL
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