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Old 06-09-2008, 03:03 AM   #1
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been researching several possible mods,but....

1. The one thing i've seen on the forum is some have put a Light Pressure Turbo in their car. after reading the info about it, i'm not 100% sure how this would increase mpg in a car. way i saw it, it could lower mpg due to a richer air mixture and the ecu would increase fuel for a cleaner burn. Maybe i'm wrong any thoughts.

2. I have a close friend who does body work on cars. I'm going to talk to him about put side shirts on the back of the car. But when i was measuring i notice my spoiler on the car. is this a mpg zipper or does really help that much on the aero?

3. My car had a small wreck in the front and back before i bought it and the hood is alittle messed up but not much. but the the sides of the hood are up just alittle bit may like.....1/8 to 1/4 of an inch. now what i read on aero, this raise in the hood shouldn't hurt my aero,but possible help. in the direction of the air is flow over the hood to the windshield. and with the raise it would seem to flow at a better angle. Again, i could be way off on my calculations. Cause one thing i thought about getting is a new hood(possible a fiberglass one to save on weight)

4. I saw the aero hupcaps on the forum and done a search online can't find them. Any help on this?

5. the previous owner put on wider tires then what the car calls for. is this hurting or helping mpg wise?
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Old 06-09-2008, 04:41 AM   #2
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just a few coments. I think one of the first things anyone should get is a scangauge. it will tell you what your mileage is and what is hurting it as far as driving style.

the light pressure trubo, I am not sure of but you will pay a good amount for it when you put it in and that is a big chunk to start off with.

I would do more research on the side skirts because some people have actually noticed that it hurt mpg and some say it helped. not sure myself on that one.

usually any damage to the vehicle like body damage is not good for the aero of the car. without pictures I can't say for sure. but just as a rule of thumb.

the aero hub caps (racing moon caps) run close to $100 a set. you also see gains of 2-3 tenths of an mpg. not really worth doing. they look cool but don't just get them for FE.

the wide tires are usually worse for FE as well. there again a rule of thumb is narrower is better. people have said that if you get LRR tires that are wider then they are better than non-LRR tires that are thinner. there again just a rule of thumb.


some mods that I like are:
1-scangauge
2-grill block
3-warm air intake (WAI)

just some stuff to think about though. I am sure you will get other responses to help you along.
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Old 06-09-2008, 08:48 AM   #3
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1. Light pressure turbo would help reduce pumping losses, I think. Sucking air through the throttle uses energy; so pushing from the other side could help mitigate that.

2. I looked at the pic of your car. I suspect you're paying a small penalty with the spoiler, but not much.

4. DIY aero hubcaps are the only way they'll pay for themselves in a reasonable amount of time. Search around, folks do it with pizza pans and it doesn't look bad.

5. Take a look at the link in my sig about tire width/rolling resistance. I disagree with BEEF; it is my belief (based on the science presented in that thread) that wider tires have less rolling resistance than narrower tires (given that they're constructed and inflated the same).
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Old 06-09-2008, 02:43 PM   #4
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The turbo on Wagonstein right now could be considered a "light pressure" turbo since I've got the computer set to run a max of 2 psi. This allows me to run 87 pctane gas instead of 93 octane, and it also allows me to shift at a much lower rpm. I've currently got my rev limiter set to 3,000 rpm and it's not a problem to merge on the highway from a dead stop.

Some car companies have tuned turbocharged cars to run stoich up to about 5 psi of boost. My SRT-4 was like that. So it's not dumping extra fuel when you get into boost. I imagine the "light pressure" turbo cars have their computer do the same thing.
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Old 06-11-2008, 08:56 AM   #5
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turbo application would be best if you are going to taller gears, since it takes more power to spin them. 91cavGt so what are your gains with thelow pressure turbo(i would not think that the diffrence woul be great). on aome of the other forums some of the guys that have put on turbos claim that they have actually improved gas mialiage(it might be that the car is not working as hard) but that is just my theory but most of them are running around 10psi
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Old 06-11-2008, 12:44 PM   #6
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usually, (and I may be wrong) the LRR tires are in the smaller sizes. I guess this means they have a stronger side wall. I do agree with the theory of less side wall deflection but with that info. why aren't they making huge tires (255mm+ width) for the smaller cars. I think you get to a point of diminishing returns with the added weight and frontal area. this may also be the reason that usually the narrower tires have the LRR option over the wider ones.

I have a set of 275mm tires on my truck, they are still 29.1 inches in diameter but they are a very sticky composite and are rated to (I believe) 150+ mph. I think the application determines what selection you have as well.

I don't completely understand all there is to know about the LRR tire thing. I am still learning myself. if there is a better explinations of LRR vs other losses (weight and aero) then I am all ears.

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Old 06-11-2008, 12:59 PM   #7
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There would actually be quite a few reasons that there aren't wider LRR tires for small cars.

I suspect that the market for LRR tires is too small for much variety, and since most people looking for LRR tires want narrow (and cheap), there's no reason to produce wider ones.

I think the aero issue is probably worth more than RR at abnormally large widths, too. There's probably a point of diminishing returns on width vs. RR, whereas the aero issue gets significantly worse as they get wider, especially if they exceed the width of the car.

With aspect ratio being used to define the difference between tire categories, if you had 195/65/15 tires, 255 width would be a 45 series, squarely inside of modern definition of the "sport" category. That would destroy marketing of LRR tires.

Plus, it's hard to sell something that looks awful, and excessive width doesn't look good to most people except as part of a more complete sport styling upgrade.

All in all, my non-expert recommendation is merely to avoid going narrower, and look at moderately wider tires available in the correct diameter and in the model you want to buy -- but only when your old tires are ready to be replaced.
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Old 06-12-2008, 08:08 AM   #8
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I have seen an S-10 with 375s on the back. that thing was sweet and the tires didn't stick out a bit.

it did have a tubbed out bed and a built 350 in it along with a little parachute on the back end. I think it was running 10s in the qtr.


but on a more serious note: given what you have said and the theory behind it (which makes sense at least to me) it would be also good to get a tire with a much higher load rating than stock. this would give you much more strength in the side wall but will make your ride rougher. so it could be fesable to put truck tires on a car (if all the dimensions were the same) and get less rolling resistance just by the load rating because of the weight differences in the vehicles.

could you determine rolling resistance by load capacity? when I change my tires next time, I may do that instead of looking for LRR tires. it is going to be a while though. my tires usually last about 3 years.
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Old 06-12-2008, 09:13 AM   #9
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Tires with higher load rating would most likely have more RR at a given pressure, but they also accept higher pressure. I say that because I imagine that the stiffer sidewalls cause more RR when they deflect. I think the total deflection amount would be pretty much the same but the force required to cause it would be more.

If you can put Load Range E tires on, you're looking at a rated maximum of 80psi. If your car isn't heavy enough you won't be able to use that (handling would become bouncy and skittery) and you would probably be better off with 50psi P-metric tires. If it's a fat pig (much heavier than frankencav) then 80psi could work.

FWIW, 80psi is marginal on the rears on my truck when it's empty and the road is slippery. It's always good at the front. I weighed it at a truck scale once that tells you axle weight; there was some stuff in the bed, but it should be good for reference. I'll have to try to find the scale printouts.

51psi is great front and rear on my 3000 pound VW. I imagine 60psi would be ok too but I choose not to exceed the tires' ratings.
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Old 06-12-2008, 12:52 PM   #10
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didn't think about the higher pressure.

another idea (and this may be retarted) there was a tire or should I say rim that accepted two really narrow tires on the same rim. the concept didn't take off. I haven't seen it for a few years. it was the width of a regular tire but had 4 side walls almost like a mini dually. they were putting them on lugury cars like the cadillacs. I wonder if that were any good as far as rolling resistance

obviously, I am not seriously thinking about them as the tires would be very difficult to find and expensive and that isn't even counting the rims.

I am a truck performance guy at heart so all this stuff about better FE is actually the reverse of the way I have thought for about the past 5 years or so. I am learning and hopefully getting better.
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