Improve low RPM throttle lag and throttle linearity (quick and easily reversible)

hli

Member
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Mazda 3s
The touchy throttle and abysmal lag at low RPMs of the 2 have been bothering me for a while. I've noticed that this isn't an issue when the clutch is depressed; throttle response is greatly improved when the clutch is disengaged, and the throttle is much more linear, instead of the super aggressive response for the first half of pedal travel, and almost nothing towards the last 2/3 of travel that the car has stock. I know this can be remedied with a tune, but I definitely don't have $500 to spend on one at the moment, so I thought up another method.

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In order to implement this, simply disconnect the clutch actuation sensor (blue sensor in above photo). There are two sensors on the clutch pedal; one to determine if the clutch is depressed fully for starting the vehicle, and another for determining if the clutch is depressed at all for the cruise control on the touring models, and also for switching the throttle mapping on both models (I assume so that people don't stall the car every single time they take off due to the immense lag). The sensor you want to disconnect is the one that is closer to the driver. It is a simple clip, just use your fingernail or a small screwdriver to press in the locking pin and disconnect the sensor connector. This effectively fools the ECU into thinking that the clutch is depressed all the time and it stays in the more responsive throttle map.

Throttle response is greatly improved in the low RPM ranges, and the throttle is now linear. It will be fairly noticeable when you drive around the first time after disconnecting the sensor. The only reservation I have with this is I'm not certain if there is a neutral ignition map that the car now uses instead of the normal ignition map it should be using. I haven't noted any CELs as a result, but I have yet to test it long term. Take of it what you will; its a quick and easy reversible mod.
 
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I could always dyno it to see what happens when the B-Spec car is back in the shop again.

Derrick
 
This is a very curious discovery. I wonder if it would make any difference on my tuned car, or if this problem has already been tuned out.
 
Yeah, I believe cruise control will no longer work because it thinks the clutch is always depressed. If you really wanted to, it would be easy to wire an inline switch so you can enable/disable the sensor easily.

@Derrick, I think your b-spec car should have a tune that already adjusts the throttle map, so you might not see a difference. An easy way to check is if you leave the car in first gear with no throttle input and all of a sudden floor the vehicle, the stock 'laggy' response would require about 1.5-2 seconds for the car to respond. With the sensor mod, I'm getting closer to .5-1 second. I assume a tune would be about .5-1 second response as well, because when I was looking into getting one, that was one of the advertised benefits.

However, if the tuner did not adjust the neutral ignition map or throttle map, it would be interesting to see if there were any differences.
 
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I was unsure of this when I first read it because of while we worked on tuning my car we looked at the throttle mapping and there isn't any noticeable lag between throttle application and the throttle body movement.

Last night I unplugged the switch and this morning I noticed no difference in throttle. I then plugged it back in and drove doing the same tests and noticed no change. I then tried it one more time unplugging it and again noticed nothing.

My car has never had the kind of lag which you are talking about, which is why I was unsure about this. Even the 0.5-1s lag you mention seems off. Can you upload a video showing this lag?

One other question this is on a Mazda 2 right? Just wondering because next to your name it says Mazda 3s.
 
Yes I do own a 2, I had a 3s before The lag only really occurs when you are in gear with your foot off the clutch and throttle. Floor it and the car takes about 1.5 seconds to respond.

Do you not notice any difference in throttle linearity? It should be especially noticeable when changing gear. Whereas I originally only needed to depress the accelerator about 1/8 after shifting for a smooth transition, now it takes about 1/4, due to the byproduct of having a more linear throttle distribution.
 
I checked hitting the gas at a few different RPM as well as heel and toe down shifting. Is there a particular RPM you have the issue? I am thinking tonight I might try to get a video of the tachometer and say when I floor it so you can see how it reacts. Any gear you have in mind, so I can use the gear and RPM in the video?

If there is that much of a delay heel and toe would be impossible.

Also I have looked at the throttle map for the tune while I made it, as well as physically checked the throttle body, and they are linear.
 
I can relate to hli pre tune on my 2. It had that same lag at under 2k where if you push the gas, you sometimes get that lag of about a second before the motor responds. Post tune, the problem is remedied. I can't say what difference this makes since my car is already tuned.
 
The issue with throttle response only happens at idle while in gear. The throttle response is fine when the clutch is depressed, so heel toe is unaffected. There is no difference past 2k RPMs as EF9 mentioned. I'll see if I can get a video showing the difference between having the sensor plugged in and then disconnected. Are you trying this with the stock tune, or on an already tuned car? It seems the issue goes away after a car is tuned.
 
I just noticed the issue that you noticed. I have not tried this as I have gotten the tune and have noticed that this lag is no longer there
 
Ahh I think I see what you mean now. I wouldn't have noticed it because I never drive below 2000rpm, While diving around I typically keep the rpm's above 2500. I can check on my car at some point possibly tonight sometime while getting ready for an autocross tomorrow.

I have a tune, but we never changed the throttle mapping on it. I know because I did it.
 
Interesting, that is quite a significant difference in response time. I'll have to check myself how my car behaves when I do the same.
 
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Sprint booster does not fix the throttle response, rather it makes so that the first 3/4-1/2 of the throttle is extremely sensitive; it excaberates the problem with throttle linearity that I have with the car, and doesn't improve the lag. However, it does give the impression that you are driving a faster car simply because for a given amount of pedal travel, it multiplies it by a certain amount and feeds that new value to the throttle sensor.
 
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