legacycentral bbs

Legacy777 wrote:Can you define "run better"

Sorry, forgot the audience.

More 'crisp' from a standstill (before turbo kicks in), pulls harder...as I mentioned above, when temps get over 80 the car is noticeably less responsive. With the AC on it's like the some of the performance is regained.

TD

wtdash wrote:Sorry, forgot the audience.

More 'crisp' from a standstill (before turbo kicks in), pulls harder...as I mentioned above, when temps get over 80 the car is noticeably less responsive. With the AC on it's like the some of the performance is regained.

TD

Hmmm....about the only thing I can think of is the fuel maps become extra rich during hotter days, and by turning the AC on the extra load may help bring things a little leaner.

To test this theory, if you have a wideband, check AFR's while driving and accelerating during cooler temps. Then try to reproduce similar driving conditions in hotter tempers without AC and then with AC. You're trying to see if there's much varience in AFR's during similar engine loading scenarios.

Legacy777 wrote:
To test this theory, if you have a wideband, check AFR's while driving and accelerating during cooler temps. Then try to reproduce similar driving conditions in hotter tempers without AC and then with AC. You're trying to see if there's much varience in AFR's during similar engine loading scenarios.

I can do this....good idea. I'll report back...but don't hold your breath. Gotta get the other project finished.

TD

93forestpearl wrote:Find me a fuel system in a higher horsepower car that uses a returnless system. There are none.

How about every LS-powered GM vehicle ever built, including the ZR1? Or the Ford SVT Cobras and GT500s, or Chrysler's Hemis and Viper?
Although it's really done to keep the fuel vapor and resultant emissions down, the fact is that a returnless system keep the fuel system cooler because the fuel isn't constantly circulating through the engine compartment and fuel pump, both of which heat up the ENTIRE fuel system, even in the tank. Cooler fuel puts out less vapor, so there you go.

SLODRIVE wrote:

93forestpearl wrote:Find me a fuel system in a higher horsepower car that uses a returnless system. There are none.

How about every LS-powered GM vehicle ever built, including the ZR1? Or the Ford SVT Cobras and GT500s, or Chrysler's Hemis and Viper?
Although it's really done to keep the fuel vapor and resultant emissions down, the fact is that a returnless system keep the fuel system cooler because the fuel isn't constantly circulating through the engine compartment and fuel pump, both of which heat up the ENTIRE fuel system, even in the tank. Cooler fuel puts out less vapor, so there you go.

I may have gone off the handle a little bit. Making blanket statements is bad and I should never have done it. I normally know better. A couple things just bothered me though.



I just don't see proof that a returnless system maintains cooler fuel temps at the injectors, which is the meat of what I was trying to get at when it comes to Subarus and modified fuel systems. Don't take it out of context. A returnless system will keep fuel in the engine bay longer, which has a direct result of fuel temperature at the injectors. But a factory system runs the pump at a lower pressure, which i understand, and keeps the fuel pressure lower adding less heat to the fuel overall. This stuff does not apply to our cars, however.

The long and short of it is decently modified cars do not bother with returnless systems and do not have heat issues because of it. Some may have a fuel delivery issue if their fuel tank says so (ahem, Subaru), so people install a fuel surge tank.

Anyways, fuel temp is really a moot point since flow is what really matters at the end of the day. Most people struggle with injectors (a small part of the fuel delivery system). If someone was really trying, they would have a proper swirl pot.


Sorry to cause such a stir.

93forestpearl, when you say "swirl pot", do you mean a fuel cool can? Basicaly a can with 3/8" or 1/2" fuel line coiled around the inside, and sealed so you can add ice water to help in cooling the fuel. I see these alot on drag cars at the strip.

Brian