changing idle flunctuation

[TomTomTom]

Hi,
Anyone heard of being able to tune the engine's setup so that the idle rpm will not fluctuate in relation to whether the cooling fan is running? The reason I would like to do that is that my idle rpm's drop by as much as 200-300 rpm when the cooling fan goes off and that makes hill-starts more tricky. Basically, I'm on a hill, raise the clutch to just the right spot, then right before I manage to press the gas peddle the idle RPM happens to drop off just then stalling the engine (people behind honking, etc).

It's a new Mazda 6 2.0 liter and I've been wondering why I've had occasional difficulties with hill starts in my new car (never had that problem on manual before)... THEN I noticed the RPM fluctuation... did some experimenting and determined for sure that it's the sudden inopportune drops in 300 rpm's that causes the stalls.

So can the Mazda mechanics simply "setup" the engine to STAY at the higher rpm level @Idle regardless of the cooling fan running or not??

Thanks, it would be nice to know a little more myself before I go to the service place.

Cheers

 

[TomTomTom]

Can you not just press the accelerator a bit to keep the revs up?

Not while I have my foot on the break as I'm on a hill.

 

[TomTomTom]

Just learn some clutch control - the regular idle of your car is the lower figure, it increases to compensate for the air conditioning when its turned on (and, as a consequence, the cooling fan comes on).

Like I said, I did experimenting with it. The lower rpm figure can barely hold the car on a very small incline... any more of an incline and it can only slow the sliding-back at best (and I realize that hand brake is needed in more extreme cases)

I've never remotely had a problem like this on other manual cars. I haven't driven manual for a few years before this car, but I'm not a beginner at it.

 

[TomTomTom]

Lol yes, that lever down to your left is called a handbrake

Read my above post.

 

[TomTomTom]

Anyway, I guess it's a little hard to believe that the lower rpm level is inadequate, but that's what's happening. I know how to hill-start on both small and big inclines and I know how to tell the difference. I'm well versed with clutch control. Just wanted to know if taking out the fluctuation is generally possible.

 

[TomTomTom]

Dunno about mazdas but i used lemmiwinks with my revo stage 2 software and upped my revs by 40rpm so my harsher dogbone mount doesnt vibrate now. Before you could feel slight vibration through the steering, now its gone.
Ask your dealers if its possible then find someone on the mazda forums with the appropriate cable and software (again, if its actually possible)

Thanks, hopefully they can do it then.

The variation is just so extreme in terms of available power that it really messes me up. I raise the clutch until I feel it catching just enough, then the next thing I know is it's not nearly enough because the revs went way down.

Thanks

 

[TomTomTom]

You are going to have to explain more - what are you trying to do? Allow the idle speed to hold the car on a slight incline with your foot off the accelerator?

Exactly that. No one else in this thread does that? .... raise the clutch to catching just-enough (while foot on brake), then calmly move foot to gas pedal while car holds position. Works on most reasonable hills. I've always done that.

 

[TomTomTom]

Your car does not produce suffcient torque at low rpm to move your car up the "incline", hold it on the handbrake and give it more revs.

NO. Not move-the-car... just to hold the car in place long enough to get to the gas pedal.. lol

Personally I think you need to adapt your driving style!

it's worked on all other manuals I driven just fine. you'll even find that technique in a driving manual

 

[TomTomTom]

Virtually no cars will do this! It's not what you are supposed to do with a manual car. You bring the clutch up as you apply throttle.

Well this is a surprise to me. It's what they teach in driving school and like I;ve repeated it's what I've always done. And for anyone else catching up, again yes I know about hand-brake on extreme hills.

Anyway, thanks everyone

 

[TomTomTom]

For what its worth, the 20vt VAG engine can easily pull away from the steepest of hills on the bite point, it just keeps raising revs until it goes.

No surprise to me. It's amazing what a car can do at idle if it's not badly underpowered or at too low idle.

 

[TomTomTom]

I wasn't expecting debate nor the jokes about my clutch control (which is just fine... arg).

Anyway, I guess in the UK people only use hand brake on any hill. Good enough.

But those who don't have really underpowered cars... just try it before you knock it. It's pretty neat and it doesn't eat the clutch any more than moving off, probably less if you don't hold position for too long. Go to a reasonable incline and try it. With foot on brake, raise clutch until you feel a slight shudder... don't raise clutch too much. Then release brake ... if the hill is not excessive, the car will hold. Less cumbersome than using hand brake every time. I didn't make this up, it's what I and many others have been taught.

Cheers

 

[TomTomTom]

Fair enough if you've got a huge engine-d car or a diesel, but you've got a 2.0 Mazda.

it has no problem doing it when the rpm's haven't dropped by the 300 rpm amount. And other non-diesel cars I've driven have also done it just fine.

Most people don't actually use the handbrake on a hill-start anyway - off the brake and straight onto throttle/clutch and the biting point will get you underway quite happily.

I know that. I do that too.

And TBH if you went to a garage about this I think you'd get a few smirks.

Thanks for the warning, but I've never heard of this technique being a no-no. Different strokes in the UK.

 

[TomTomTom]

BTW, I think some people mistunderstood "cooling fan" for the A/C. I meant the cooling fan on the rad.

Also BTW, the level that the idle rpm drops to after the fan has been runnung is lower than average for the car.

 

[TomTomTom]

Well I fail to understand how doing this wears the clutch more than regular moving off or for that matter doing a hill start with the quick-footed method. If you've never done it yourself, you're probably imagining something brutal... it's very quiet, uneventful and smooth when you do it.

Anyway thanks. Maybe the Mazda 6 just isn't a good car for doing that with. Oh well. I'll just get out of the habit if the rpm drops can't be "dialed-out" of the system.

 

[TomTomTom]

Tried it on the way to work this morning.....and bugger me....it actually works, as long as I bring up the clutch slowly.

Just found a steep sloped side-street, stopped at the bottom, stuck the car in first and lifted slowly, it make a little grumble when the clutch was 1/2 way up, but then went on to creep all the way up to the top, without me touching the accellerator pedal. Slowly admittedly, but it did do it.

As volospian said, it's only to hold the car while you move your right foot from the brake to the gas. Once you're on the gas it'll feel a little different from your usual moving off since your clutch is already part way up... you might chug a little the first time you try it.

 

[TomTomTom]

Yes, also known as slipping the clutch

it's very minor since you're at idle rpm and only long enough to move your foot from brake to gas. Besides we're not talking about spinning it as in "smoking it" or anything even close to it. You spin it probably more when you quick-foot it on an incline (also reversing a split second of backward momentum).

There is zero extra revving... very smooth.

Just try it... maybe takes a few tries to really get consistent. There's a rather narrow sweet spot on the clutch that holds it just right.

 

[TomTomTom]

Either way it's wrong and you can't blame the car for it.

I was taught to use the handbrake to hold the car whilst setting bite point, just adapt, you go to the dealer with this problem and they'd just laugh at you.

I understand that the car might not be perfect for this because of the rpm fluctuation and that the rpm drops so very low suddenly. When however the rpm is steady, it works a treat with the Mazda 6... really

I'll just drop the habit and do only quick-foot and hand brake from now on with this car... it's not right for it unlike other cars I've driven.

 

[TomTomTom]

I really don't see the advantage of this technique. How can it be any quicker than using the handbrake, throttle and clutch simultaneously?

Once you're proficient at finding the sweet spot where the clutch holds it, it's just an easy and very smooth thing to do... don't know what else to say about it.

The world of manuals can live without it though... quick-footing and hand brake are a piece of cake as well. It's just another way to do it

Edit: but not to be done on steep hills where you would rather use hand brake. Only where you would otherwise quick-foot; advantage: not even a split second of backward momentum.

 

[TomTomTom]

Simple solution is to not ride the clutch on such a knife edge. Give it a bit more gas so that the slightest error or fluctuation in RPM isn't going stall it...

the whole point of this is to hold the car long enough to move foot from brake to gas, so that's kind of irrelevant.

not addressed specifically to NathanE:
I can understand the skepticism if you've never heard of doing this, but it's really not any more wear on your clutch than a quick-foot hill start where you counter that split second of backward momentum... think about it (and no, I don't over-rev when I do the latter)

Try it a few times to get moderately proficient at it, then decide whether it's "excessive wear" on the clutch. If you "see", hear and feel for yourself how it goes (when done right and not on an excessive hill), I can't see how you can conclude that it's excessive wear.

 

[TomTomTom]

lol


he isnt riding the clutch... he isnt causing extra damage and ZOMG *** WORLD WONT END!

yeah it's totally fine for the car...

Come to junction... stop with foot brake and stay on foot brake!

Then when you want to go, let the clutch out till you feel it bite... then you can take your foot off the brake and put it on the accelerator without rolling back and pull away quickly and safely ( providing you car has enough power/torque not to just stall >.< )

exactly how it's done (only to clarify that you're not rolling back at all as you're switching to the gas pedal). A diesel would be a little more forgiving because it won't stall as easily if you're off the mark, but any reasonable power/weight ratio car will do it

To the OP - get another car lol

I'm happy with the car I don't mind doing hill starts the other ways. Just was curious to what extent the idle rpm stuff can be tweaked... like if it can be forced to not fluctuate at all (it's +/-300 rpm fluctuations that cause the issue)