Its not always about MPG

[oil pan 4]

I remember seeing a blog about a guy with a metro who put in a sweet belly pan, then boiled his gas tank with trapped exhaust and coolant system heat.

[Tahoe_Hybrid]

Originally Posted by oil pan 4

I remember seeing a blog about a guy with a metro who put in a sweet belly pan, then boiled his gas tank with trapped exhaust and coolant system heat.

metros have 8 gallons how long will it take to boil 24.5 gallons?

[oil pan 4]

Since the relationship between prism surface area versus volume is almost linear so a tank with 3 times the volume only has double the surface area. So about 50% more time.
So if that guy boiled his metro gas tank in 40 minutes, if conditions were the same for both tanks then the big 24 gallon tank would take just 1 hour total to reach the same temperature.

[roosterk0031]

My Cobalt fuel trim had been maxing out off and on for over a year before I finally figured it out. Evap Purge valve was creating a vacuum leak. My code was always a lean code, don't remember the number, even though it was running crazy rich. Got the first replacement part from O' store worked a few months. ACDelco part been working 5 months now.

Tahoe & Cobalt even have the same part number.

[cRiPpLe_rOoStEr]

Originally Posted by Tahoe_Hybrid

how do go about fixing the rear as the air issue (the air from the underbody gets shot straight up in the air exiting from the rear end) i guess this could be a significant source of drag

You mean getting something similar to the extractors often found on racing cars? Go for it.

[Tahoe_Hybrid]

Originally Posted by roosterk0031

My Cobalt fuel trim had been maxing out off and on for over a year before I finally figured it out. Evap Purge valve was creating a vacuum leak. My code was always a lean code, don't remember the number, even though it was running crazy rich. Got the first replacement part from O' store worked a few months. ACDelco part been working 5 months now.

Tahoe & Cobalt even have the same part number.

it's the MAF/IAT combo

the IAT is showing 20-30 degrees higher on a stone cold start.. the MAF might be incorrect as well as it back fired a few times as well

I run chevron fuel

the MAF/IAT sensors are a common failure

sometimes it cranks too long and goes to 1500-2000rpm(with it's obnoxiously HUGE Electrical 60,000 watt starter)

[aerohead]

Originally Posted by COcyclist

Is there a high pressure fuel pump in the tank? This has largely removed vapor lock in modern cars. Also I believe there is a return line so fuel should always be circulating to the tank, helping keep the lines cool. Insulate the fuel lines if necessary.

Read up about rear diffusers. Ideally the rear 1/3 of the full belly pan should taper upward slightly. Aerohead has suggested 5 degrees above horizontal is best for low drag. This reduces lift and drag and helps fill the rear wake.

Belly pans from the manufacturers leave the exhaust uncovered. This allows heat to escape while giving much of the benefit of a belly pan.

From Hucho's reporting of Carr's research,the 'long' diffuser,@ 2.8-degrees upsweep angle would provide the highest drag reduction,and if that couldn't be utilized,the 'short' diffuser of 4-degrees would be the next best thing.
Neither diffuser will perform at maximum unless the oncoming flow is optimized.
Some racers will incorporate fiberglass tailpipe/muffler wrap and auxiliary heat shields if necessary,in order to completely cover the belly.

[roosterk0031]

I also had to replace the MAF pigtail. Swapped MAF sensors between the 3 cars I had at the time the had the same part with no change.

[Tahoe_Hybrid]

Originally Posted by roosterk0031

I also had to replace the MAF pigtail. Swapped MAF sensors between the 3 cars I had at the time the had the same part with no change.

when it's close to the IAT temp it runs fine

outside on the temp of 75f it starts running hwerid
say 90F-95F or 45F etc..

the engine will oscillate then the transmission will refuse to move at all and will sit there revving the engine..

(transmission is not married to the Engine RPM)


as I can shift it to manual mode
(which just turns off Auto Stop, EV mode and changes the "shift points" it also married the Engine to the transmission, as Engine braking is now enabled)


there is no silver in the transmission fluid it's clean and fresh



it's really slow to respond sure the wires are good i all ready tried cleaning it etc..

there could be a cracked solder inside it or the sensor wire damage, i'm going to take it apart when i get a new one.. to see what failed

the connectors are clean and shiny ..


when it's at the IAT temp outside everything works fine.


Auto stop works
EV mode works
No sitting there engine revving
Transmission moves normally and smoothly

[cRiPpLe_rOoStEr]

Originally Posted by aerohead

Some racers will incorporate fiberglass tailpipe/muffler wrap and auxiliary heat shields if necessary,in order to completely cover the belly.

AFAIK exhaust wrap also allows the catalyst to heat up sooner, decreasing the so-called "cold phase" which is where most of the harmful emissions are generated. Seems ideal for a hybrid, considering its engine would be operating in a more intermittent way in city driving. On a sidenote, besides protecting nearby components more sensible to heat, retaining more heat at the exhaust flow instead of allowing it to irradiate is often claimed to improve its flow.