Dead spot in part-throttle acceleration at ~2200-2500rpms
Thread Starter
Not DAVEB the parts guy
Joined: Aug 2000
Posts: 8,549
Dead spot in part-throttle acceleration at ~2200-2500rpms
Over the past few days I've been noticing a slight dead spot in acceleration during part-throttle from 2200-2500rpms. It just feels like the car is lagging and then it's completely fine after 2500rpms. It's not huge issue because paasengers can't feel it, but I can. The temps in my area have been in the 85-90 degree range so I'm thinking it may just be the MAF/ECU adjusting in the lower rpms when the underhood intake temps are extremely high. Anyone else feels this?
Dave
Dave
I feel the same thing..I remember reading a post a while back aobut this same situation and people coming to the conclusion that there IS a dead spot at part throttle 2200-2500...Thats just how the tourque curve is set up
-matt
-matt
Donating Maxima.org Member
Joined: Aug 2000
Posts: 577
I've always had that light throttle "dead spot" on hot days for as long as I've owned my '95. Its not so apparent when I am heavy on the gas. The light throttle dead spot doesn't show up when driving in cool weather.
Having an automatic exagerates the problem.
Having an automatic exagerates the problem.
Thread Starter
Not DAVEB the parts guy
Joined: Aug 2000
Posts: 8,549
Originally posted by tattoo
any ideas on what might be causing this???
any ideas on what might be causing this???
Dave
Originally posted by Dave B
I would guess that the extreme underhood temps, less dense air, higher humidity, etc make the ECU and MAF have to constantly adjust timing and air/fuel ratios to keep the motor from detonating under load.
Dave
I would guess that the extreme underhood temps, less dense air, higher humidity, etc make the ECU and MAF have to constantly adjust timing and air/fuel ratios to keep the motor from detonating under load.
Dave
Originally posted by gtr_rider
I thought I was the only one
I thought I was the only one
Noticed this for such a long time and thought that it was just me. Especially driving my mom's auto, feels like the engine just felt like taking a break.
Oh yea. One more thing. I remember reading on here that if you find a better ground for the MAF or something it eliminates this dead spot. Anyone have any experience with this?
Donating Maxima.org Member
Joined: Aug 2000
Posts: 577
I don't think changing the ground would make much difference unless the existing grounding point was defective (corroded, loose, etc).
The Place Racing CAI upper section (or similar intake product) cleans up the dead spot to some extents.
The dead spot is also exxagerated by the torque converter slippage in the following way:
1. Torque converters provide for greater acceleration through a given slippage IF the increase in engine torque percentage exceeds the slippage percentage.
2. In the range of 2000-3000 rpms, the engine torque is relatively constant. Unfortunately, the torque converter does not remain locked-up in this speed range with anything more than 1/8th throttle. Therefore, the slippage exceeds the increase in torque so the acceleration drops off.
3. Based on the physics of the converters; the faster the road speed, the more difficult it is to produce slippage for a given torque input. (not necessarily bad). Off the line, a driver can see up to 2000rpms of slippage the moment the throttle is applied. From 2000rpm of road speed, maybe only 500 rpms of slippage may be acheivable. From 3000rpm of road speed, perhaps virtually no slippage can be produced even with maximum engine torque. The converter can transfer more torque and power at higher road speeds. Some of you may wonder why at medium to heavy throttle, your Maxima seems to blast off once past 3000rpms. You have your torque converters to thank for sandbagging the low-rpm response.
4. With more heat, the tranny fluid becomes less viscous. That promotes more slippage which the VQ series engine is not well suited for.
Why are transmissions designed this way, you might ask?? A "tight" converter would mean that at a stop, the driver would have to maintain considerably more pressure on the brake pedal to hold the car still, or perhaps the engine would have to burn more fuel to hold an idle. It might even require the "incovenience" of putting the selector in Neutral while at a light to reduce such stresses. Because the average driver complains to exert the least amount of effort in driving, the mechanicals in the average car are sandbagged by the designers.
my two cents
The Place Racing CAI upper section (or similar intake product) cleans up the dead spot to some extents.
The dead spot is also exxagerated by the torque converter slippage in the following way:
1. Torque converters provide for greater acceleration through a given slippage IF the increase in engine torque percentage exceeds the slippage percentage.
2. In the range of 2000-3000 rpms, the engine torque is relatively constant. Unfortunately, the torque converter does not remain locked-up in this speed range with anything more than 1/8th throttle. Therefore, the slippage exceeds the increase in torque so the acceleration drops off.
3. Based on the physics of the converters; the faster the road speed, the more difficult it is to produce slippage for a given torque input. (not necessarily bad). Off the line, a driver can see up to 2000rpms of slippage the moment the throttle is applied. From 2000rpm of road speed, maybe only 500 rpms of slippage may be acheivable. From 3000rpm of road speed, perhaps virtually no slippage can be produced even with maximum engine torque. The converter can transfer more torque and power at higher road speeds. Some of you may wonder why at medium to heavy throttle, your Maxima seems to blast off once past 3000rpms. You have your torque converters to thank for sandbagging the low-rpm response.
4. With more heat, the tranny fluid becomes less viscous. That promotes more slippage which the VQ series engine is not well suited for.
Why are transmissions designed this way, you might ask?? A "tight" converter would mean that at a stop, the driver would have to maintain considerably more pressure on the brake pedal to hold the car still, or perhaps the engine would have to burn more fuel to hold an idle. It might even require the "incovenience" of putting the selector in Neutral while at a light to reduce such stresses. Because the average driver complains to exert the least amount of effort in driving, the mechanicals in the average car are sandbagged by the designers.
my two cents
Originally posted by chris j vurnis
I don't think changing the ground would make much difference unless the existing grounding point was defective (corroded, loose, etc).
The Place Racing CAI upper section (or similar intake product) cleans up the dead spot to some extents.
The dead spot is also exxagerated by the torque converter slippage in the following way:
1. Torque converters provide for greater acceleration through a given slippage IF the increase in engine torque percentage exceeds the slippage percentage.
2. In the range of 2000-3000 rpms, the engine torque is relatively constant. Unfortunately, the torque converter does not remain locked-up in this speed range with anything more than 1/8th throttle. Therefore, the slippage exceeds the increase in torque so the acceleration drops off.
3. Based on the physics of the converters; the faster the road speed, the more difficult it is to produce slippage for a given torque input. (not necessarily bad). Off the line, a driver can see up to 2000rpms of slippage the moment the throttle is applied. From 2000rpm of road speed, maybe only 500 rpms of slippage may be acheivable. From 3000rpm of road speed, perhaps virtually no slippage can be produced even with maximum engine torque. The converter can transfer more torque and power at higher road speeds. Some of you may wonder why at medium to heavy throttle, your Maxima seems to blast off once past 3000rpms. You have your torque converters to thank for sandbagging the low-rpm response.
4. With more heat, the tranny fluid becomes less viscous. That promotes more slippage which the VQ series engine is not well suited for.
Why are transmissions designed this way, you might ask?? A "tight" converter would mean that at a stop, the driver would have to maintain considerably more pressure on the brake pedal to hold the car still, or perhaps the engine would have to burn more fuel to hold an idle. It might even require the "incovenience" of putting the selector in Neutral while at a light to reduce such stresses. Because the average driver complains to exert the least amount of effort in driving, the mechanicals in the average car are sandbagged by the designers.
my two cents
I don't think changing the ground would make much difference unless the existing grounding point was defective (corroded, loose, etc).
The Place Racing CAI upper section (or similar intake product) cleans up the dead spot to some extents.
The dead spot is also exxagerated by the torque converter slippage in the following way:
1. Torque converters provide for greater acceleration through a given slippage IF the increase in engine torque percentage exceeds the slippage percentage.
2. In the range of 2000-3000 rpms, the engine torque is relatively constant. Unfortunately, the torque converter does not remain locked-up in this speed range with anything more than 1/8th throttle. Therefore, the slippage exceeds the increase in torque so the acceleration drops off.
3. Based on the physics of the converters; the faster the road speed, the more difficult it is to produce slippage for a given torque input. (not necessarily bad). Off the line, a driver can see up to 2000rpms of slippage the moment the throttle is applied. From 2000rpm of road speed, maybe only 500 rpms of slippage may be acheivable. From 3000rpm of road speed, perhaps virtually no slippage can be produced even with maximum engine torque. The converter can transfer more torque and power at higher road speeds. Some of you may wonder why at medium to heavy throttle, your Maxima seems to blast off once past 3000rpms. You have your torque converters to thank for sandbagging the low-rpm response.
4. With more heat, the tranny fluid becomes less viscous. That promotes more slippage which the VQ series engine is not well suited for.
Why are transmissions designed this way, you might ask?? A "tight" converter would mean that at a stop, the driver would have to maintain considerably more pressure on the brake pedal to hold the car still, or perhaps the engine would have to burn more fuel to hold an idle. It might even require the "incovenience" of putting the selector in Neutral while at a light to reduce such stresses. Because the average driver complains to exert the least amount of effort in driving, the mechanicals in the average car are sandbagged by the designers.
my two cents
It makes sense now. FAQ time.
Originally posted by matty
We have 5-speeds and we still feel the hesitation and no Tourque converter ???
-matt
We have 5-speeds and we still feel the hesitation and no Tourque converter ???
-matt
I've felt the hesitation in both a 5-speed and auto Max. So I guess that would explain why it's more pronounced with autos but doesn't explain why it happens in the first place.
Thread Starter
Not DAVEB the parts guy
Joined: Aug 2000
Posts: 8,549
I drove around today paying close attention and it's definately related to heat soak of the engine and high underhood temps. I believe the reason we can really feel this dead spot is because most of us are using some sort of non-OEM intake. Why does this matter? Because the aftermarket intakes remove the stock intake's ability to store and pressurize the air in the resonators. This lack of pressurization causes the MAF to have slight tuning problems because the air becomes slightly turbulent in the lower rpms. The effect of the hotter air seems to make the problem more noticeable.
If my engine is cool or the weather is cool, it doesn't have the dead spot.
As for the MAF grounding mod, I did it a month ago and it did make a difference. My car's part-throttle acceleration is much better than it was. I use to have some "bumpiness" in acceleration at 3800-4000rpms, but that is completely gone.
Dave
If my engine is cool or the weather is cool, it doesn't have the dead spot.
As for the MAF grounding mod, I did it a month ago and it did make a difference. My car's part-throttle acceleration is much better than it was. I use to have some "bumpiness" in acceleration at 3800-4000rpms, but that is completely gone.
Dave
Originally posted by Dave B
I drove around today paying close attention and it's definately related to heat soak of the engine and high underhood temps. I believe the reason we can really feel this dead spot is because most of us are using some sort of non-OEM intake. Why does this matter? Because the aftermarket intakes remove the stock intake's ability to store and pressurize the air in the resonators. This lack of pressurization causes the MAF to have slight tuning problems because the air becomes slightly turbulent in the lower rpms. The effect of the hotter air seems to make the problem more noticeable.
If my engine is cool or the weather is cool, it doesn't have the dead spot.
As for the MAF grounding mod, I did it a month ago and it did make a difference. My car's part-throttle acceleration is much better than it was. I use to have some "bumpiness" in acceleration at 3800-4000rpms, but that is completely gone.
Dave
I drove around today paying close attention and it's definately related to heat soak of the engine and high underhood temps. I believe the reason we can really feel this dead spot is because most of us are using some sort of non-OEM intake. Why does this matter? Because the aftermarket intakes remove the stock intake's ability to store and pressurize the air in the resonators. This lack of pressurization causes the MAF to have slight tuning problems because the air becomes slightly turbulent in the lower rpms. The effect of the hotter air seems to make the problem more noticeable.
If my engine is cool or the weather is cool, it doesn't have the dead spot.
As for the MAF grounding mod, I did it a month ago and it did make a difference. My car's part-throttle acceleration is much better than it was. I use to have some "bumpiness" in acceleration at 3800-4000rpms, but that is completely gone.
Dave
Thread Starter
Not DAVEB the parts guy
Joined: Aug 2000
Posts: 8,549
Originally posted by matty
Dave,
what is this grounding mod you speak of ?? I have no clue and ive never heard of it before
-matt
Dave,
what is this grounding mod you speak of ?? I have no clue and ive never heard of it before
-matt
Dave
Originally posted by Dave B
Splice into the ground wire of the MAF and run the extra ground wire to one of the engine grounds. It only works if your MAF's ground isn't very good. I tested my MAF's ground with a volt-meter and mine the readings were pretty bad.
Dave
Splice into the ground wire of the MAF and run the extra ground wire to one of the engine grounds. It only works if your MAF's ground isn't very good. I tested my MAF's ground with a volt-meter and mine the readings were pretty bad.
Dave
EGR Cleaning
Originally posted by 96white
how do you clean it , and where is it located?
how do you clean it , and where is it located?
The large tube coming from the exhaust isn't the problem. The small metal tube on the bottom (which connects to a rubber hose) connects the EGR to the intake and has a narrow passage that easily gets clogged with carbon resulting in too little air flow. This can cause pinging at light throttle so the ECU retards timing, which decreases power and can cause surging similar to a bad knock sensor.
Spray carb cleaner in the small tube to clean the deposits, maybe even use a small drill bit to poke in there. Also check the condition of the rubber hoses since an air leak will cause problems. Too much flow such as a leak or weak EGR valve spring can cause midrange hesitation.
The EGR valve controls the amount of exhaust gases circulated back into the intake to be reburned. It stays closed during idle and wide open throttle and only operates during midrange RPMs when the engine is warm. The BPT valve monitors the EGR system so the ECU knows what's going on down there. A properly functioning EGR system doesn't rob power, but a malfunctioning one does.
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