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-   -   Warning: Bad to bump start and skip gears (http://www.fuelly.com/forums/f8/warning-bad-to-bump-start-and-skip-gears-2116.html)

budomove 05-16-2006 08:02 PM

Warning: Bad to bump start and skip gears
 
Posted these questions on HT and got the following response.
Just a heads up.



Is it bad to shift from 1st into 4th, assuming you are not revving 1st too high. My gears are really long...4spd std?

I recommend either shifting to neutral and letting out the clutch to rev match fourth gear or push in the clutch, shift 2-3-4, and let out the clutch. It is easier on the synchros.

Is it bad to coast in neutral?

It is OK to coast in neutral. Make sure the clutch is out to keep the input shaft spinning. This ensures lubrication. I usually coast for shorter periods by depressing the clutch with the transmission in gear. For longer periods, I shift to neutral.


Is it bad to coast with engine off, and bump start?

Don't bump start. You can really stress the axles. If you do bump start, use the highest gear. Coasting with the engine off also cuts your engine lubrication. So, you are restarting each time. It is not as bad as a cold start, but I don't recommend it.


SVOboy 05-16-2006 08:11 PM

Def rev match if you're
 
Def rev match if you're doing anything serious with rpm changes, that's my rule. And we always try to bump start in the highest gear anyway, I've never felt it to be a stressful event when I've done it. And the neutral advice makes sense, don't want to wear the throwout bearing with the clutch in.

JanGeo 05-16-2006 09:03 PM

Shifting from 1st to 4th or
 
Shifting from 1st to 4th or 5th is ok if you let the engine rev down a bit - there is enough drag on the clutch that the slower engine speed will also slow the clutch disk down and just pause in neutral before going into the next gear. With the Clutch pressed in the clutch disk spins at the speed of the car times the gear ratio that you are in. Going fast and putting it in first gear really spins the clutch disk and the throwout bearing. It can explode the clutch disk if you are going too fast. Throwout bearings usually don't wear out much anymore as better ones are being used now. Most of the gears are turning from the axle end and they are located low in the gear box and throw a lot of oil around to lubricate everything. The input shaft not turning is not a problem. The bump starting is turning the crank from the center and is even easier on the main bearings than the starter BUT it is a start without oil pressure so there is unlubricated wear going on for a fraction of a second and probably with HOT oil which is thinner than cold oil but there could also me more of it? Don't pop the clutch too fast either as it does load the axles and CV joints and use higher gears at higher speeds as you already know.

philmcneal 05-16-2006 10:44 PM

Quote:Don't bump start. You
 
Quote:

Don't bump start. You can really stress the axles. If you do bump start, use the highest gear. Coasting with the engine off also cuts your engine lubrication. So, you are restarting each time. It is not as bad as a cold start, but I don't recommend it.
hm... interesting my axles get banged when i bump start at really low speeds like 15 km/h or 10 km/h in 2nd or 3rd sometimes. 4th I rarely get a bang and 5th is usually smooth but sometimes rev goes a little to high. So far 4th has been very good to me....

but that means i'll have to bump start when my speed gets below 30km/h... then idle drats! Aw man a few mpg or a new axle Ill dedcide hMMMMMMMMMMMMM

as for lubrication that's what synthetic mobil 1 0-20w oil for hybrids are for! Works for regular cars that support 5-20 like mine but I yet have to make the switch!

plus I heard putting it in your tranny fluid gives it boost too! maybe more silky bump start?

SVOboy 05-17-2006 04:12 AM

With my project I'm using
 
With my project I'm using 5w20 (down from 5w30) for the time being, until I can find some 0w20, :(

Anyway, phill, you can get autozone remanufactured axles with a liftime warranty so you can break as many as you want, :)

krousdb 05-17-2006 08:24 AM

Re: With my project I'm using
 
Quote:

Originally Posted by SVOboy
With my project I'm using 5w20 (down from 5w30) for the time being, until I can find some 0w20, :(

I have a stockpile of 0W-20. I might be able to spare some for you are interested.

cheapybob 05-17-2006 11:17 AM

Re: With my project I'm using
 
Quote:

Originally Posted by krousdb
Quote:

Originally Posted by SVOboy
With my project I'm using 5w20 (down from 5w30) for the time being, until I can find some 0w20, :(

I have a stockpile of 0W-20. I might be able to spare some for you are interested.

I tried changing to 1/2 5w-20, but it had no effect on MPG that I could tell

philmcneal 05-17-2006 11:18 AM

since this threada bout the
 
since this threada bout the fear of bump starting i'll add to other people's remarks

Quote:

Even if your tires do not blow up on you, they will wear in the middle in no time. In any size, at any cost, it takes more to replace tires then what you save on gas.
Your engine works outside of the designed temperature envelope, which means fouling everything- from spark plugs to your catalytic converter. Plus, your oil probably has never get to operating temperature (it takes much more time for the oil to get warm then the coolant). You do not ever burn the moisture and fuel contamination out of your oil. That means the sludging possibility is eminent, even with synthetic oil.
Re-starting the engine as often as you do increases the oil contamination by the fuel and removes vital lubrication layer from the cylinder walls.
Your exhaust will rust out very fast too because the water condensation there does not ever burn off.
It is not quite safe to switch the automatic transmission from D to N while driving. Depending on conditions you might as well switch into R with all the consequences.
As was mentioned before, you lose ABS, EBD, power steering and get a strong possibility of the steering wheel lock-up.
I have the ScanGauge as well. As much as I like it for everything else, it is not as accurate in measuring the fuel consumption as "at-the-pump" method. I log both every fill-up, and the SG readings are usually off by more then 10%, no matter what engine size you set in SG.
To me, some of your tips totally make sense, although many are just not helpful, and some are quite dangerous.
hmmmmmmmmm svoboy i didn't know axels were that cheap to begin with haha.

JanGeo 05-17-2006 12:30 PM

Saving a few mpg Yeah you
 
Saving a few mpg Yeah you know the amount of money you save in 50,000 miles of driving if you get 3% more MPG with higher pressure is about $100.00 if gas is $3.00 a gallon and you get about 40-45mpg. Is it worth the ride quality loss . . . hummmm I wonder. The tire wear should be a little less with higher pressure however but then you have the extra wear and tear on the suspension components from the hard drive. Makes me think a little . . . hummm.

SVOboy 05-17-2006 08:26 PM

Quote:hmmmmmmmmm svoboy i
 
Quote:

hmmmmmmmmm svoboy i didn't know axels were that cheap to begin with haha.
Think it's like 60 each with a lifetime warranty for my car.


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