Power after Highway Driving?

[aaronsbiza]

I have been noticing lately that my 95ATX has quite a bit more power and pep when Driving on the highway. After a nice long drive on the highway it seems that the car runs so much better. However, when driving in the city the car seems to have a pretty large loss in power. I used to be able to smoke the tires from a dead stop, but I can no longer do it. Is there a reason for this? Shouldn't the car run the same consistantly? Is this a symptom of a sensor on its way out? O2 Sensors? MAF? Any input would be helpful. (60K has been Done, no oil in plug wells, no codes)

 

[MOSHO92]

Though this doest really help the solution, ive noticed that my MTX is very similar. After driving a long distance/time on the freeway it feels pepyer for a few days. But if ive been chuggin around stop and go traffic for a week it feels a little sluggish. I think of the freeway as exersize for the yamaha!!

 

[yamahaSHO]

Could be heat soak shrug

 

[aaronsbiza]

Heat Soak..? Could you please elaborate

 

[yamahaSHO]

Yeah... When you are driving on the freeway, you always have fresh cool air passing through the engine bay. This helps keep the runners cooler, which allows cooler(more dense) air to enter the motor. Stop and go driving prevents some of that fresh air to pass through the motor, this allows the runners to heat up. With the runners hot, warm(less dense) air now enters the motor.

If you turn off your motor and feel your runners, you will be able to touch them with out burning yourself. Let it sit for about 3-5 minutes and I bet the runners are too hot to touch. Hope this helps explain the above paragraph.

Also, do a search on Phenolic Intake Spacers.

SHOnut Phenolic intake spacers

 

[aaronsbiza]

Thanks for elaborating... I am going to bypass my tb coolant lines soon, so maybe that will make a diference. Thanks for the input.

 

[yamahaSHO]

No problem... I my self would not do the TB bypass. But thats just me, good luck!

 

[aaronsbiza]

Well I live in Sacramento, so It never gets even close to freezing all year long, so theres no problem with doing the tb bypass. I wonder if there may be some way of attaching an alternative cooling system specificaly for the Intake Manifold. That would be an interesting project.

 

[SHO_ROLLER]

What is a TB bypass? shrug

Anthony headbang

 

[aaronsbiza]

There are coolant lines routed through the throttle body that are supposed to keep the TB from freezing in the winter. Being that I live in Sac CA it never gets that cold and it just adds uneeded heat to the intake. If you do a search you will find procedures on bypassing the coolant lines. It is an easy mod and may add a pony and a half, atleast it keeps the heat down a bit on the intake.

 

[SHO_ROLLER]

Thanks! I'll do more research through the search function. thumb

Anthony

 

[Detenator]

I noticed the same thing about mine. Next time you do city driving, take a look at your temp guage. When it gets above a certain point i always notice a complete dropout of low end torque. Its pretty embarasing to stall it constantly in the city because i forget that i have to hit the gas harder with a hot engine. Some of these Manhattan people are pretty relentless if you don't go before the light changes green. (HONK HONK)

 

[PUZ]

I would agree with the heat soak. I have been in contact with many cars and it seems that most small displacement motors designed with performance in mind tend to loose a lot of there pep when everything gets hot as it does in city or stop and go driving. That alternative cooling thing you speak of seems like a waste(too much effort not enough gained). Just hook up the happy gas!!! It’s the same concept, kinda

hail ZEX hail

 

[sdpatt]

Could it be that on the highway, the engine is farther up the rev range and closer to the power peak so there actually is more power available. The heat soak issue is valid, but wouldn't result in a "pretty large loss in power." Most of the miles on my car's odometer have been accumulated on the highway, but haven't noticed this phenomenon - other than my perceptions of the engine's output.

 

[yamahaSHO]

Right now I am deciding wether or not I want to pick up some phenolic intake spacers.

 

[HopefulSHO]

Heat soak may be an issue, but I'm assumign as long as there is some air going through the intake it will keep the primary runners somewhat cool.

I did the TB & IAC valve coolant bypass "mod" when I did my upper 60k a few weeks ago, and it's amazing how much cooler my intake manifold is. It really does make a difference.

I imagine another reason could be that on the highway @ crusing speed, you're really not accelerating much. Around town, in stop-and-go traffic, you're constantly slowing down and speeding up, and perhaps your body gets used to the feeling of acceleration, so it does not feel as powerful as before.

 

[aaronsbiza]

My thought was that perhaps the computer is recalibrating itself at higway speeds. Being that the car is moving at highway speeds the sensors are are reading more extreme data. Maybe the computer is receiving data from sensors such as the MAF that may register data differently at higher speeds. Just a thought.

 

[autobahnsho]

aaronsbiza:
My thought was that perhaps the computer is recalibrating itself at higway speeds. Being that the car is moving at highway speeds the sensors are are reading more extreme data. Maybe the computer is receiving data from sensors such as the MAF that may register data differently at higher speeds. Just a thought.

I second this-

When I drive "spiritedly" on the open road then go home, the next time I start the car up (next day even) it runs a little sluggish for a while. The heat doesn't seem to matter in mine as much as different driving situations do..
Will

 

[Markus]

aaronsbiza:
I have been noticing lately that my 95ATX has quite a bit more power and pep when Driving on the highway. After a nice long drive on the highway it seems that the car runs so much better. However, when driving in the city the car seems to have a pretty large loss in power. I used to be able to smoke the tires from a dead stop, but I can no longer do it. Is there a reason for this? Shouldn't the car run the same consistantly? Is this a symptom of a sensor on its way out? O2 Sensors? MAF? Any input would be helpful. (60K has been Done, no oil in plug wells, no codes)

I have recently completed my 60K. I found new power and smoothness but I still had low off-the-line power. I also had a VERY mild hesitation on the highway when SLOWLY accelerating from 120km/h (75mph) in top gear. Josh T. (SHONUT) suggested my MAF may be bad. I unplugged it and the highway hesitation went away and highway power went up. Off-the-line power was still low. I replaced the MAF today (with an OEM MAF) and all my power is back.

I had performed the diagnostic tests and even with the old MAF no codes were generated.

 

[pete c]

Has anyone ever played around with venting the hood? Some cars have vents in the hood which are used (I presume) to vent off engine bay heat. Seems like this would help keep things cool and might also improve the sho's biggest problem (engine sensor failure).