plainred02Z

I just started driving a manual about 5 days ago. I don't know **** about all this downshifting buissness, so when I am coming up on a stoplight or stop sign I shift it into neutral and coast/apply the breaks ( like it was an automatic ). Then when its time to go again, I put it in first and am on my way. My friend took a ride with me and said "wowowo your gona wear out your breaks really quick doin it like that, you should downshift"

What is this down shifting stuff he is talking about? I do the neutral thing as thats what my dad does in all his manual trans cars.

When I try to do the down shift style stopping, my car feels like weight just transfered to the front and a surge of power is hitting the back wheels. One time I went from 3rd to 2nd and the tires chirped ( I guess I'm doing it really wrong ). Hence I don't think my car likes it.

Sorry for this newb post, but any help would be sweet. Thanks.

blackmaro99

iTrader: (5)

Downshifting is fine if you rev-match. If the downshift is slowing your car down significantly then you are wearing out the clutch.

What you are doing is fine and brakes are a hell of alot cheaper than a clutch. Slap your friend.

Ericbigmac83

iTrader: (19)

Your friend is an idiot. Brakes are made to stop cars, the engine is not. the end

plainred02Z

LOL!

Ferocity02

iTrader: (60)

Downshifting is pretty much only good if your road racing, and it's mostly done to ensure you're in the proper gear when leaving the turn. Downshifting on the streets just sounds cool, if you're good at it, and if your car sounds good. I did it all the time, I was very good at it and would rev match perfectly and could practically drop the clutch without jerking the car at all. But as mentioned, brakes stop the car, not the engine.

Avengeance

iTrader: (4)

MrDude_1

iTrader: (4)

you're only wearing out the clutch if its slipping.

downshifting a synchronized transmission (like yours) is really easy.

lets say you're in 6th, coming to a stoplight, and the light changes.... well what gear do you put it in then??
thats something you need to know anyway. lol.


heres the simple way:
clutch in and let off the gas most of the way
put it in a lower gear.. say 4th.
SLOWLY let the clutch out like a normal shift..... DONT drop it. dont excessively slip it.

doing it correctly, the RPMs jump up but the car continues to smoothly decelerate.


heres the "cool sounding" addin:

instead of letting the clutch out and having the engine jump up... *blip* the throttle as you let the clutch out.
you can then do all of this faster, and the car decelerates smoother, and it just sounds kinda cool.


and when that light changes ahead of you, you can just roll on the gas, no shifting.



btw, there is ZERO need to EVER downshift to first.
with LS1 cars, theres little need to downshift to 2nd..... just downshift to 3rd, and by the time the engine is near idle, you're almost stopped anyway, so just push the clutch in.



when you do it right, nooone notices, you just smoothly come to a stop. btw, the drivers manual in most states clearly state that you should not be coasting in nutural.. lol.


also.. this is very useful when going down steep hills.. instead of riding and smoking the brakes, just put it in a lower gear and keep off the gas..... the engine will use zero fuel (since the EFI cuts the fuel at 0% throttle under decell) and the engine will slow the car.

oh, and another thing.
DONT hold the clutch "most of the way" out as the engine comes up in a attempt to slow it. THATS how you wear out the clutch.. like i said at the start of this post.. you only wear out the clutch when its slipping.. so dont slip it. let it out and dont ride your foot on it.

Krab

iTrader: (28)

Yeah, I wouldn't listen to your friend very much, it sounds like he doesn't know what he's talking about. These guys already hit all the main points. I don't know about anyone else, but I'd much rather replace some brake pads and rotors than a clutch.

What you're doing right now is right. Kick your friend for the rest of us.

Camaro Rick

iTrader: (2)

Ask your friend to teach you, then send him a bill for a new clutch. Not to mention the extra tenth or two mpg you loose by doing it.

Keenov

iTrader: (5)

Sweet, you put an automatic into neutral before hitting the breaks?

MrDude_1

iTrader: (4)

actually, if you want to be technical, you GAIN MPG.


the LS1 (like all modern motors) does not spray fuel when theres zero throttle % and you're coasting down in gear. techically, the engine is effectively off.. or infinite MPG.


meanwhile, if the engine is idling as you're coasting down, you are using some fuel to keep the engine running... and are therefore using more gas.

but thats stupid nitpicking... lol

Ferocity02

iTrader: (60)

Good point, our cars have DFCO, deceleration fuel cut-off. Basically when the motor is at around 1900 rpm, and the vacuum pressure is VERY low(no throttle), the computer will turn off all of the injectors. Obviously, if you put the car in neutral, this won't happen because you're idling, and need fuel to keep the engine alive. So, downshifitng is good in that sense.

Bandit LS1

iTrader: (2)

Brakes are cheaper to replace then your clutch

MrDude_1

iTrader: (4)

anyone who wears out a clutch by downshifting is a dumbass.



is that blunt enough to work as a rebuttal?

2002_Z28_Six_Speed

iTrader: (19)

Dead on. It's actually illegal to be in netural at stops in many states. They will always rag on you if a wreck happens and your car gets pushed.


DFCO does spray fuel but only a small amount. It uses about the same amount as idling, but a little less. You have to consider maybe at idle is 3.5 or 3 mS INJPW and DFCO is maybe 2.2mS INJW.

If you have modified your car you need to go back and tweak the map settings, rpm values, and speed setting or it won't come on. Further, DFCO won't come on for a couple of seconds. DFCO will definely save you money with a little tuning. It can save gas if you verify that it is coming on. Otherwise you are wasting gas.

MrDude_1

iTrader: (4)

log the injector pulses....

but on mine (2002 Fbody OS) the Deceleration Fuel Cut OFF is off completely.. its zero until the RPMs approch idle.. then it eases in quickly.

i would not be suprised if GM has several calibrations thruout the years that cuts them on and off diffrently.... ive been missing with it since highschool with thirdgens, and its always been a cutoff for me at higher RPMs, but how it eases back in changes alot.

2002_Z28_Six_Speed

iTrader: (19)

The PCM will never command the injectors off. Anytime a commanded pulsewidth is lower than the default minimum pulse then the minium pulsewidth table will be used.

What software are you using to view the injector pulsewidth? That might be the decripancy.

CaMaRo67RS355

iTrader: (75)

im with him ^^^

MrDude_1

iTrader: (4)

i was logging the injector pulsewidth for injector #7 with a PIC controller (#7 was just easiest to wire neatly, no other significance)

it was for this project i was working on, that i have yet to finish.. its pretty neat.. i wanted an accurate-ish MPG reading, but i wanted it to be universal, so i was logging values like RPM and injector pulsewidth.... of course its made stupidly difficult by the fact that the fuel pressure on a stock LS1 is not manifold pressure referenced... so i had to copy the table from HPtuners....
look at post #7 here: https://ls1tech.com/usa/showthread.php?t=314371


i have logged it before in HPtuners, but to be honest, i never really paid enough attention to remember off the top of my head if it logged zero or not... although if its anything like the earlier GMECMs, it skips the min injector constant if its in full cutoff... but like i said before, i wouldnt surprised if they changed that. we're talking a 20+ year span of firmware diffs.. lol

SladeX

brakes are cheaper and easier to replace, if you've done a clutch change, you will appreciate this statement all the more.

I'd only downshift for road racing. I have no problem downshifting myself, can do it on a whim and I do usually when I know the light is going to change soon or if I am coming off the highway. If I know I'm going to stop for awhile, I'll just use all brakes. In an emergency stop or panic stop, I leave it in gear to just below idle regardless of gear and then slam the clutch in and bump to neutral.

As far as mpg goes, your right foot dominates that department, go easy and you will save, and well you know how hard that is in a car like this...