2015 FRS pulsing at low RPM's in 1st gear

[ImBatman]

Originally Posted by Koa

Brother, I'm not trying to say it's user error. I'm trying to get you to explore the possibility that it can be user error. If a mechanic, a competent one that is demonstrated and understands what happens in a clutch system, can replicate the problem, then you now have evidence that is it NOT the user.

Deduction is powerful.

I will say that I used to have this symptom bad. I commute 100 miles a day in Washington's worst traffic (I405). I have since changed out diff/outrigger/tranny bushings, adjusted the clutch pedal, swapped the slave cylinder for Ultramaroon's 3/8 retrofit, and there is virtually no pulsing now. I couldn't get it to even if I tried (okay, a bit of an exaggeration, but it is VERY hard to induce the pulsing that was exercised quite frequently when everything was OEM). Like you, I've been driving manuals for just south of a decade and was confident it wasn't me.

Turns out it was me and also the car. The clutch point is weird on this vehicle, even with the adjustments I've made and mods I've done to help remedy it. I had to alter how I engaged first and drove in traffic... but even then, I got pulsing. The supplementary mods helped a ton.

Fair enough. I'll stick to my plan and let the head mechanic check it out anyways, just to be safe.

I've adjusted the clutch pedal just so it would be closer to the floor and my knees wouldn't be in my face when fully released. I am planning on doing the slave cylinder swap soon so hopefully that will help, as well.

Also, I see your Washington traffic and raise you Houston traffic... on a toll road... where I'm PAYING to sit in traffic. And pulse lol.

[Koa]

Originally Posted by ImBatman

Fair enough. I'll stick to my plan and let the head mechanic check it out anyways, just to be safe.

I've adjusted the clutch pedal just so it would be closer to the floor and my knees wouldn't be in my face when fully released. I am planning on doing the slave cylinder swap soon so hopefully that will help, as well.

Also, I see your Washington traffic and raise you Houston traffic... on a toll road... where I'm PAYING to sit in traffic. And pulse lol.

Damn- that would be rough haha. If I hit peak traffic times at 7amish and 4pm, I'm sitting at about 3-4 hours in traffic a day, 0-35 mph. Since moving over to 7am-3pm work days, I cut the time down to 2-2 and a 1/2 hours. bleh.

The largest gain I found in reducing the pulses were tranny and diff/outrigger bushing inserts..

an awesome DIY to put the tranny bushing insert in (positive shift kit) -
http://www.ft86club.com/forums/showthread.php?p=1604573

[ImBatman]

Originally Posted by Koa

Damn- that would be rough haha. If I hit peak traffic times at 7amish and 4pm, I'm sitting at about 3-4 hours in traffic a day, 0-35 mph. Since moving over to 7am-3pm work days, I cut the time down to 2-2 and a 1/2 hours. bleh.

The largest gain I found in reducing the pulses were tranny and diff/outrigger bushing inserts..

an awesome DIY to put the tranny bushing insert in (positive shift kit) -
http://www.ft86club.com/forums/showthread.php?p=1604573

Ouch man. Very ouch. Luckily I'm only 35 miles from home so 1 - 1 1/2 hours is about max one way. The only way I'd be able to tolerate 4 hours of traffic a day would be to do it in a car like this one

Thanks for the heads up... I'll look into this mod also. Gonna delay that exhaust system tho...

[Caspeed]

Originally Posted by Koa

Damn- that would be rough haha. If I hit peak traffic times at 7amish and 4pm, I'm sitting at about 3-4 hours in traffic a day, 0-35 mph. Since moving over to 7am-3pm work days, I cut the time down to 2-2 and a 1/2 hours. bleh.

The largest gain I found in reducing the pulses were tranny and diff/outrigger bushing inserts..

an awesome DIY to put the tranny bushing insert in (positive shift kit) -
http://www.ft86club.com/forums/showthread.php?p=1604573

I think the issue is caused by the rubber components in the drive train. They tend to store energy and then release it in a somewhat uncontroled manner. It's called "wind up" much like a rubberband. By changing the compliance in the mounts you can tune most if not all of it out. As Koa suggested the tranny mount/bushing insert is a good first step. I found that it reduced the tendency in my car. The diff. mounts would probably be a good 2nd step. The down side to doing these is increased vibration and noise. A side benefit is that by reducing windup the throttle has a slightly improved control of the rear tires as there is less delay and sharper response from the drive train.

[daiheadjai]

I notice this issue as well - thankfully it only occurs at very low speeds (like 1-5km/hr), which isn't what most of us will spend a lot of time experiencing (hopefully).
Never had this on any of my previous manual cars - I just try to avoid that sweet (bitter?) spot and drive through it.

[swarb]

Originally Posted by fika84

You can usually make this happen if you're not perfectly stable on the throttle pedal. As soon as it starts to happen, the act of the jerking causes your foot to move a little bit front to back which makes it just keep on going until you either completely let off the throttle or give it a good amount of gas to get out of the rhythm. It's not something to worry about and it can be cured by better foot control.

Does the car do it if you let the engine push the car forward? IE - no gas with the clutch released in 1st gear at the slowest speed possible.

It is from all that torque. ALL OF IT. All that torque makes your foot go off of the accelerator which makes the car jerk forward, which makes your foot go forward, stepping on the gas again, thus repeating, from all those torques.

[caballo_glue]

Originally Posted by Caspeed

I think the issue is caused by the rubber components in the drive train. They tend to store energy and then release it in a somewhat uncontroled manner. It's called "wind up" much like a rubberband. By changing the compliance in the mounts you can tune most if not all of it out. As Koa suggested the tranny mount/bushing insert is a good first step. I found that it reduced the tendency in my car. The diff. mounts would probably be a good 2nd step. The down side to doing these is increased vibration and noise. A side benefit is that by reducing windup the throttle has a slightly improved control of the rear tires as there is less delay and sharper response from the drive train.

I have this issue in my car at 4,500rpm in 1st and 2nd. Do you think swapping the bushings/mounts out would help reduce lurching at these rpms? I'm familiar with them at low speeds, that's the car begging for more juice, but I'm new to the car and platform and not sure why mine is doing this at such a high rpm. My guess is it's because it's right after the torque dip and the car is riding the line of "LETS GO" and "Chill"

Any help/feedback would be appreciated.

[DarkPira7e]

I hate this behavior, a lower gear ratio diff may help (3.9 or 3.73), trans mount also helps. I put a solid transmission mount in mine and this problem disappeared. Do not go solid mounts, but get the diff insert bushing, it will help.

[Riftur]

I have owned 2 4 cylinder manual cars and both of them did the same thing at very low speed in 1st gear. I even feel it happening with my auto FRS when in manual mode but it is very minor and only lasts for less than a second before it stops.

[g e]

It happens !

I’ve logged over half a million stick shift miles and it sometimes happened with all of the cars I’ve owned.

The BRZ drivetrain is somewhat more sensitive and less than fluid pedal work will result in a hiccupy drive at slow speeds. I’ve had this car 5-1/2 years and I still stall it out once in a while.

Lightweight shoes help. Really.

[Decep]

This happens every once in a while to me too. Wife will get annoyed sometimes because she thinks im doing something wrong lol. I am usually out of first gear by 10mph anyways tooting around town.

[TooSlow]

I've noticed this too. Driving around in 1st with my 08 Miata seemed to be pretty smooth. When I drove the 86 in 1st it was like everyone says lurching, jerky, feels like stalling etc. I never tried to look into it further just thinking different car different characteristics. I've adjusted by shifting to 2nd asap but wish 1st was smoother for when I'm driving around a mall parking lot look for spaces and driving at crawling speeds.

[extrashaky]

Sounds like another example of driver-induced oscillation to me.

There is a phenomenon usually experienced in aircraft called "pilot induced oscillation." It happens most often in situations where very small inputs to the controls cause large changes in the state of the aircraft. What happens is that there is a very small lag in the pilot's reaction to the plane, and that lag is in phase with the aircraft's response so that it actually exaggerates the movement of the plane rather than diminishing it.

For example, suppose I'm flying an airplane and push the nose up a little, but it goes up more than I wanted it to. The plane will want to level out on its own, but I push the nose down. So now it goes down further than I wanted it do, so I pull up again. Soon I'm porpoising up and down and bucking all over the sky.

I say, "This damned plane! It's hard to control!" But it's really me causing the problem because my inputs are exactly in phase with the plane's response. Most pilots who crash planes due to PIO don't even realize they were doing it. It just seems like the plane went crazy. High performance aircraft, like fighter jets, actually have dampening in the control systems to make them less responsive, to "tune out" the danger spot for PIO.

Similarly, because of the excellent throttle response of our cars, driver induced oscillation happens with the throttle at low speeds. When the car slows down, the slightest input to the accelerator makes it buck up. The natural reaction is to let your foot off the pedal, but that makes the car jerk back down. Most people are not even aware that they're doing it and just think the car is jerky at low speeds. It doesn't happen at high speed because a small change in pedal at higher speeds makes a relatively smaller change in response. A tap that would jerk the car violently at 6 MPH could have almost no effect at 60 MPH.

The way to avoid driver induced oscillation is to change your thinking so that you anticipate what the car is going to do. You do that by driving through the bucking. Instead of trying to get the bucking under control, concentrate instead on keeping a steady foot that drives right through the oscillation and comes out smooth on the other side. The car will smooth out.

[accwai]

There seems to be a number of somewhat unrelated situations in this thread with a lot of unspoken assumptions. The OP says 5mph in first gear but no engine RPM mention. No mention of whether throttle is absolutely still either. According to the gearing table I have, first gear 5mph is 1000rpm stock. As per extrashaky above, you are going to get slapped around if you're really rough on the throttle here. But if you keep it totally steady, I don't think RPM is low enough to stall yet.

Then somebody else says changing to second gear would smooth things out. Now back to the gearing table, 5mph in second gear is 600rpm. At this RPM the car is probably about to stall. I wouldn't do it myself. In the streets, I normally keep things about 2-3krpm. Going above that eats a lot more gas, so I only do that if it's called for. I once ride in a coworker's manual Honda (Civic IIRC). The guy upshifts well below 2000rpm pretty much through the whole trip and the engine shows no sign of lugging. You can't do that in a twin. I'd keep it in the properly RPM range at all times.

Somebody mentions pulsing in first and second gear at 4500rpm because of torque dip. Don't know if that's pulsing around 4500rpm at constant throttle. I don't normally cruise at this kind of RPM as that eats a lot of gas. But when the situation calls for it, I can go from 3k to 6k in one quick go without any hiccup in the middle. Personally, "chill" isn't quite how the torque dip region should be described. It's just a little less "go". I've always had TRD CAI which eases the dip according to some. Never driven a totally stock one, but it's hard to imagine you would pulse/choke passing through the torque dip region. I would get somebody competent to look at the car if it pulses at 4500rpm under constant throttle.

Somebody mentions lightweight shoes. I have a separate pair of lace-up, perfect fitting shoes just for driving the 86. In the early days with this car, when I rush out the door without the right shoes, things got so rough it's scary. These days, things are under control without the reserved pair but I still prefer it.