Higher RPM vs Weight to start car from stop in 1st gear

[Chiba]

Hey all,

I'm new to this forum and only found this place last week. Very informative but I am slightly information overloaded as there are just too many tips. I am a new manual driver, driving a 2013 WRX for around 3 weeks.

I'm starting to get fairly comfortable with starting in 1st gear from stop. I try to be off the clutch at 1.5K RPM.

Anyways, something interesting happened today which I would love input from experienced drivers. I think it hasn't been discussed and would be very useful for new manual drivers like me.

I drove myself and 2 male colleagues to lunch this afternoon and for some reason I kept stalling at lights.

After thinking about it at work (shhh!) I realized something: If the car gets heavier, should I be starting at a higher RPM (i.e. 2000 rpm rather than 1500rpm) to compensate for the weight? Is this situation similar to a car pulling a trailer?

If you're wondering, the combined weight of my colleagues is around 400 pounds.

Thanks!

[rml605]

Welcome!

And nice car. WRX is one of my choices for my next car.

IMO, but i'd let more experienced guys chime in, would be to still go no more than 1.5K or but slip the clutch a drop more.

[IMBoring25]

You do obviously need to do something differently, but I would consider 2000 for just standard launching in traffic to be excessive for anything other than a small-displacement motorcycle with a wet clutch.

It sounds to me like you would benefit from a drill that's been discussed many times here, no-gas launching in a parking lot. On level ground, pretty much all vehicles will (eventually) launch without the use of the gas given only patient clutch work. Doing this really lets you feel the clutch take-up in what's variously described as the friction point or the friction zone.

In actual usage, more weight demands more throttle or moving the clutch through the friction point/zone more slowly. Using more throttle is not necessarily the same as using more RPM because you can let out clutch to pass more torque to the wheels and keep the torque generated by the engine and passed to the wheels equal. My goal is generally a launch very close to idle but that's a tall order for a beginner.

For the launches, if you focus on your clutch work, the rest will take care of itself as your skills develop.

[theholycow]

If your normal launch has no margin for error then more weight will require more of something...more RPM, more time with the clutch, more torque (heavier clutch engagement + more accelerator but not more RPM), more jerking, etc. Launching on level land with an extra 400 pounds might be similar to launching on a mild incline (except no rollback worry).

With practice you'll be able to do it at the same RPM using more accelerator and more clutch. For now do whatever works best for you.

[ClutchDisc]

Welcome!

I drive a 2001 Chevy S-10 and have hauled some heavy loads in it before. Yes a lot of weight will generally require more gas on your launches. If you were giving it just enough gas without the extra weight and then gave it the same amount of gas with the extra weight, that would explain why you were stalling it. Similar situation, when I run my AC it puts enough of a load on the engine that if I give it the same amount of gas that I give it when not running the AC, it will stall.

P.S. Post pictures of your car in the Members Cars forum! It sounds like a nice car.

[Shadow]

I drove myself and 2 male colleagues to lunch this afternoon and for some reason I kept stalling at lights.

After thinking about it at work (shhh!) I realized something: If the car gets heavier, should I be starting at a higher RPM (i.e. 2000 rpm rather than 1500rpm) to compensate for the weight? Is this situation similar to a car pulling a trailer?

If you're wondering, the combined weight of my colleagues is around 400 pounds.

Thanks!

No, 400 lbs of passengers in a 3500 lb car really isn't very significant. You can launch at your normal RPM without issue...if anything, just slip the clutch a bit more.

BTW, don't get too hung up on your launch RPM. With practice, you'll be able to launch from idle RPM, with a full car load of people or when you're alone. Try to focus more on your clutch engagement than your RPM.

[tankinbeans]

You've received some good advice already. I'll say welcome to the board and don't overthink what you're doing.

It could have been a case of nerves, they never help. You'll figure out what works for you.

As for the other tips, take them with a grain of salt until you're more confident/proficient. They're helpful, but not necessary for a beginner. I'm barely out of that stage myself.

[ClutchDisc]

No, 400 lbs of passengers in a 3500 lb car really isn't very significant.

Actually 400 lbs is a significant amount of weight in a 3500 lb car. That's about 11.5% of the cars weight.

[tankinbeans]

No, 400 lbs of passengers in a 3500 lb car really isn't very significant.

Actually 400 lbs is a significant amount of weight in a 3500 lb car. That's about 11.5% of the cars weight.

I remember having trouble with 800 pounds of passenger, not counting myself. Then again I was in a gutless Corolla with a bad clutch. In Clifford 800 pounds of passenger, not counting myself, is just fine. He's a bit more powerful, and has more torques.

Each car reacts differently, and I'll take the driver at his (or her, I may have missed a gender identifier in the post and don't wish to assume) word that it may have created a challenge. I remember thinking, when I was learning, that my tire pressure was causing issues.

[Chiba]

Wow guys, thanks very much on all the tips and comments.

I think overall its two things, as suggested by everyone:

1) Just nerves. Peer pressure to yourself when you have passengers
2) Have to think of it like a hill; slip the clutch point a little longer with normal RPMs to get the car going

I will make sure not to Rev to 2000 as much as possible at starts, but that should come as I gain more experience.

A few more tidbits mentioned in the thread, but not related to it:

a) He
b) Funniest thing - I've tried numerous times to no-gas launch the WRX in a safe environment; It'll do it but it stutters like a mechanical bull - reading the WRX specific forums, the issue is likely due to the ECU program by Subaru.
On the other hand, I've tried no-gas launches in a Mazda 3 when I was learning (I actually took a lesson) and had absolutely no problem.

c) I'll post an intro and picture of the car soon
d) Clutch engagement - I think I'm developing both the good and bad techniques at the same time (another story, another time since I'm at work)

[daleadbull]

^ I think the trouble with no-gas launch might be because your car is AWD. Mine is too and in order to no gas launch, you need to slip the clutch more. More grip means more force needs to overcome it. I usually pause for a second at clutch engagement in order to get it hooked up.

[theholycow]

^ I think the trouble with no-gas launch might be because your car is AWD. Mine is too and in order to no gas launch, you need to slip the clutch more. More grip means more force needs to overcome it. I usually pause for a second at clutch engagement in order to get it hooked up.

Nobody is overcoming grip with a no-gas launch in any car, unless it's got a 1000hp alcohol fueled dragster engine with a messed up high idle and bald street tires on snow.

There's more drivetrain loss with AWD, wasting some energy, but that would just mean your no-gas launch would be a little slower; it shouldn't cause anything described as "stutters like a mechanical bull". The buggy ECU program sounds like a plausible explanation.

[Chiba]

^ I think the trouble with no-gas launch might be because your car is AWD. Mine is too and in order to no gas launch, you need to slip the clutch more. More grip means more force needs to overcome it. I usually pause for a second at clutch engagement in order to get it hooked up.

Nobody is overcoming grip with a no-gas launch in any car, unless it's got a 1000hp alcohol fueled dragster engine with a messed up high idle and bald street tires on snow.

There's more drivetrain loss with AWD, wasting some energy, but that would just mean your no-gas launch would be a little slower; it shouldn't cause anything described as "stutters like a mechanical bull". The buggy ECU program sounds like a plausible explanation.

Ok I might have exaggerated on the "mechanical bull"; its more like a cyclic stall-no stall bumpy ride until you start gassing.

I think its a combination of both AWD traction and the ECU program that causes this issue. So following with that train of thought: yes, a no-gas launch IS doable for the car, but I would not want to do it regularly.

That's what I'm experiencing in this car anyways. Definitely my two cents rather than what happens in all WRX's.

Oops.. kinda off topic now

[tankinbeans]

Oops.. Kinda off topic now

It's your thread, if you didn't bring it off topic (you didn't, really), it would have been jacked eventually.

[theholycow]

^Word. Off-topic is the nature of forum threads except with heavy moderation, and those places are no fun.

To reiterate: Traction is NOT an issue and is not in play. No traction issue has any role in a no-gas launch (unless you're on smooth ice or deep in mud). A no-gas launch uses a fraction of a percent of available traction with 2WD or AWD alike. Differences in available traction don't come into play for launching until you're doing a hard racing launch. Traction is not compromised with 2WD for a no-gas launch on any surface other than ice or mud, a dry or wet pavement regular launch, or even a dry pavement aggressive jumping-out-into-traffic launch.