[JP'sTc]

Ok, ive basically learned to drive stick in a day and a half but I have a few questions. Whenever im in a parking lot or some where similiar that im going to be going very slow ( but not stoping completely) should i leave the car in second gear even though the car kind of feels a bit rough? Its almost like a very small jerking feeling when i let of the gas. Second question is should i keep the gears high even if my speeds aren't very high? For example if im going 35 and im in 4th, is that ok? And if for whatever i reason i have to slow down to lets say....20 should i leave it in 4th and then just accelerate or should i downshift into 3rd? There were several more questions I had, but ill ask once i get all this down. Any help would greatly be appreciated, thanks guys.

 

[kurker]

I learned stick on my tC too. Only downshift into first if you are going less than 5 mph. You'll feel that the car doesn't want you to put it in first if you are going faster. I assume that you are not past your 1000 break in miles yet so accelerating from 20 mph in 4th is not the best idea. it will make then engine work harder than it needs to. You should downshift into third to accelerate. 35mph is 4th is ok if you are just cruising, but if you need to accelerate you should be in 3rd. Do your engine a favor and don't rev it too high for too long until you are past your break in miles. This will be hard because you are just learning stick, but try not to dump your clutch from high rpms when starting in 1st while your car still has less than 1000 miles on it.

hope this helps, good luck and congrats!
Do NOT take my advice as law and if I am incorrect in anything here please somebody correct/flame me. I have insulation, I can take it!

 

[JP'sTc]

Yea I only have about 150 miles on it, and ive already done like half the things im not suppose to by accident. so basically keep my revs low and my gears matched?

 

[lucidspoon]

Originally posted by JP'sTc@Oct 3 2005, 08:24 PM
Whenever im in a parking lot or some where similiar that im going to be going very slow ( but not stoping completely) should i leave the car in second gear even though the car kind of feels a bit rough? Its almost like a very small jerking feeling when i let of the gas.

What I usually do if the car starts to jerk some from going slow in second, is to push the clutch in and coast. Then, if you want to start accelerating again, you can give it more gas before you release the clutch, and it shouldn't jerk as much.

Be careful when doing that though. You don't want to ride the clutch, because that can tear it up. You'll get a better feel for it the more you drive.

 

[Obike]

Everyone has to learn sometime, and I congratulate you on getting a manual!

Personally, I always stay in the appropriate gear for what will be best to avoid an accident (even when slowing down). You never know what will happen when you are coming to a stop, so being able to get the heck out of there ASAP can save you from a serious wreck (it's saved me numerous times). As far as cruising in a parking lot and feeling that "jerkiness", that's just the engine letting you know you are getting close to stalling. At that point give it a lil' more gas or put the clutch in and coast.

 

[lo bux racer]

Not exactly. The ECM shuts off fuel when you close the throttle between 1800 and 1200 rpm. This is an EPA emissions thing, and has been in place since the 80's. There's actually a test in the FSM for fuel shutoff that calls for the tech to rev the engine to 3500 rpm and let the throttle close to observe the injectors get shut off while the engine decelerates to idle.

So if you are cruising around at parking lot speeds between 1500 and 2500 rpm, the engine will be starving for fuel every time you let up on the gas, and then hitting hard again as soon as you apply a little gas. It makes for a really jerky ride. I slip the clutch alot in parking lots, and it does no harm because you're not putting a lot of torque on the thing, just using it to smooth out the power delivery. I've done it for many years and never had wear issues with any clutch I've owned.

 

[Ryan'stc]

This brings up a question I have about fuel and power. If I'm driving at 25mph it feels like I have more response than if I'm driving at 65 and I am revving the engine at the same rpm level. Now why is the engine more responsive at low speeds than at high speeds if it's the same engine speed?

 

[Drift Motion]

torque

 

[Greenfire]

Originally posted by lo bux racer@Oct 4 2005, 01:12 PM
Not exactly. The ECM shuts off fuel when you close the throttle between 1800 and 1200 rpm. This is an EPA emissions thing, and has been in place since the 80's. There's actually a test in the FSM for fuel shutoff that calls for the tech to rev the engine to 3500 rpm and let the throttle close to observe the injectors get shut off while the engine decelerates to idle.

So if you are cruising around at parking lot speeds between 1500 and 2500 rpm, the engine will be starving for fuel every time you let up on the gas, and then hitting hard again as soon as you apply a little gas. It makes for a really jerky ride. I slip the clutch alot in parking lots, and it does no harm because you're not putting a lot of torque on the thing, just using it to smooth out the power delivery. I've done it for many years and never had wear issues with any clutch I've owned.

So this may partly explain the throttle hesitation we all complain about.

 

[serith]

Yeah, I know exactly what you guys are talking about, and I tend to take my parking lot @ work with lo bux's approach.. just slip the clutch. Or go slow in 1st @ ~2600rpm's..

That jerkiness kills me. lol

 

[oldman]

In response to "Ryan'sTc" question..

Torque is NOT really the clear answer, although it is a large part of the answer. At a given rpm, the engine can produce only so much torque (and HP). At both 25 and 65 mph, if you're at the same rpm, the WOT (wide open throttle) torque/HP available from the engine is the same (but not the HP you are using to cruise at a steady speed - see below).

What's obvioulsy different is the gearing (5th vs. 2nd I'm guessing). Lower gearing makes for acceleration, higher gearing makes for speed. In a sense, the gears act as a torque multiplier - remember, HP = torque x rpm. Aside from drive train and parasitic losses, engine HP = wheel HP; and if wheel rpm's are lower than engine rpm's, the wheel torque has to be higher. The lower the gear, the greater the multiplier. Also, in low gear, when you "punch it", small incremental changes in speed equate to relatively large changes in engine rpm (thereby very quickly providing even more torque/HP up to the engine limits). In high gear, small changes in speed produce smaller changes in engine rpm (and therefore slower/smaller increases in torque/HP).

What's not so obvious is the fact that at 65 mph, you're already using more HP/Torque just to maintain that speed vs 25 mph....tire rolling resistance, body wind resistance, bearing losses, and [final] drive train losses are all greater as speed increases. Therefore, you also have less HP/Torque available for accelerating. (Remember, you're crusing, so not at WOT, and therefore not at max torque fro the given engine RPM)

That's why you might be able to outrun a higher HP car in the 0-60 or even quarter mile (gearing, weight & skill), but almost never be able to reach as high a top speed, even if you had gearing that would allow such speeds... You run out of HP before they do.

 

[lo bux racer]

Originally posted by Greenfire@Oct 4 2005, 03:40 PM
So this may partly explain the throttle hesitation we all complain about.

Yes, in a small sense, but if you reduce the rotating weight with a lightweight flywheel, the hesistation disappears. Slow speed jerkiness is directly related to fuel cut though. I avoid slow speed driving at low rpm just for this reason, or as I said, slip the clutch to keep the gas on while running at parking lot speeds.

 

[Greenfire]

I read about an easy fix for the throttle delay on scionlife. It works like a charm, hesitation/jerkiness is gone. Shifting/clutching is much smoother.. very noticeable.

hesitation fix

Basically by extending the upper throttle stop, you eliminate that 1/4 inch dead spot of the pedal. I tried it just by using a few pieces of electrical tape and it works quite well. Just make sure you don't raise your idle. If the idle goes up then use less tape or whatever have you.

 

[lo bux racer]

I just pulled mine out of the car to check if there is any slop in it. There isn't. Zero. Zip. Nada. Nil. Nothing. Instant change in resistance as soon as the pedal moves.

I don't doubt it works, but I disagree it is removing any slop in the accelerator.

I still prefer the Fidanza solution.

 

[wolo]

You and me both, Lance.

 

[Greenfire]

Its not removing slop. There is none, I agree. The throttle electronics simply don't register for the first 1/4" of depression. By lowering the pedal starting point you eliminate the dead zone. Im gonna start a new thread about this, mabye some other peeps can try it out and report back.

 

[Greenfire]

Allright I stand corrected, apparently the electronics do register as soon as the pedal is touched.. but I don't think the signal becomes strong enough to actually raise the rpms until you push it some more.

 

[lo bux racer]

I don't think so. You really need to drive a car with a Fidanza flywheel. You will stop believing there is a problem with the electronics, and agree the problem is really inertia. I suspect futher reductions in rotating mass (like a true lightweight harmonic damper, or removing the balance shafts) would result in even better throttle response. All you are doing with the shim under the accelerator is opening the throttlebody from it's idle position and changing the ignition timing, so it will respond quicker. One of the things TCCS does is set idle timing when the throttle is fully closed. When it isn't it advances the timing from 10 degrees (on most Toyco engines) to around 21 or 22 degrees. I will admit I have not tested this on the 2AZ, but I know this is true for all the cable operated throttlebody engines. That's why they have the IDL contact in the throttle position sensor.

I'd also be curious to see if the fuel cut feature is disabled with this mod. If either of these things are happening, your fuel economy and emissions profile should be affected.

Now you have me curious as to what is really happening with this...

 

[Greenfire]

So do you think we are causing any harm by putting that spacer in? I always tried to keep my foot on the throttle all the time anyhow to avoid the jerkiness. But now im thinking about warming the car up on a cold winter morning.. just sitting there idling... but not truly at idle.

Otherwise, I think I understand what you are saying... so basically it takes a little more than that 1/4" of throttle to get everything rotating and moving... and for the ignition timing to change.

 

[lo bux racer]

I can't say if it's harmful or not. It might be, but without really doing some study on what is actually happening, I can't be sure. It might be completely benign, and only affect idle emissions. I really can't say without looking at the affected systems with and without the mod.

I suspect the reason for the delay is the accelerator change doesn't make enough power to overcome the inertia until you've put about a 1/4" into the accelerator. I've experienced exactly this with the wife's auto on my driveway incline. I have to hit the gas much harder than I think is prudent before the car moves, and when it does move, it jumps ahead unpredictably. The manual has similar issues with the stock flywheel, but ever since the Fidanza went in, I've not had any of these issues. Power delivery at low throttle openings is predictable and just like any cable operated system I've owned.

My timing light doesn't work with low voltage (OK, so it's 23 years old, and I probably need to join the 21st Century for better diagnostic equipment), so I can't easily test the ignition timing theory, and I don't have a super trick OBDII scanner like the Toyco tool or the other tool (anybody want to give me $8k to buy one? Yeah, I thought so) so I really can't validate my theory.