Surging Cruise Control
 

This topic has been posted before but the last post was dated in September and I'd like to get some updates re: the cruise control surge.

Like many RX-8 owners, my car is doing the same thing. I set the cruise for 65-70 and I can feel the car rocking back and forth even though the difference in speed does not register on the tach or speedo. It is subtle but definitely noticeable.

My car has just >3,000 miles on it, though I don't use cruise control very often.

Your experience?

Mine seems very consistant. I am going on a 300 mile trip tomorrow so I will take my garmin gps and check it out.

Mine doesn't surge or rock or anything. Doesn't even skip a beat when I engage the cruise.. it just keeps on without any change in speed.

However I do have that stupid false check oil light at speed.. need to get that oilpan replaced... I just don't want anybody else touching the car but me!

Yah. so with my 3000+ miles I have zero surging.

I dont have that issue either. I dont think it's that many owners that are seeing this at all. When it first came up I tested CC at speeds from 65 to 80MPH and didnt get anything at any speed.

No cruise control problems here and used it extensively on my 2000 mile round trip to VA for Christmas.

The original issue stemmed from when you release the cruise control and press reset (typically on an uphill angle) from a slower speed (15-20mph), some people, including me, have experienced the cruise going WELL beyond the original setting, only to fall back to normal after a seemingly long time above the original setting.

It is intermittent, but is annoying in traffic when it does happen.

No problems with the cruise control here either, and I love the way the speedometer shows and stays on the EXACT mph. I am spoiled by the speedo, my next car will have to have a digital speedometer.

Mine also worked just fine and I went on a 2,900 mile trip for the holidays. My cruise control was active for about 1/3 of the time.

Re: Surging Cruise Control
 

I had the surging problem once, but it was only after I had slowed for a moment, then hit the resume button.

Are you sure you aren't just feeling it pull now and then as the terrain changes. I can't imagine a scenerio where the speedo and tach wouldn't register a speed change.

I haven't noticed a cruise surge either. AT or MT?

I don't think I would use reset on an upgrade. I use it in level cruising with no traffic impediments, but otherwise just come to the speed you want and click Set. Don't know why; I guess I don't like the acceleration rate you get when you use Reset.

That said, my cruise is rock solid. Speedo don't flicker like some have mentioned; click up or down in 1 mph increments; I am very satisfied.

Here is the original thread i spoke of:

https://www.rx8club.com/showthread.p...threadid=10032

Definitely check it out so I can prove I'm not crazy!!!!:(

No problem with mine- in fact I've never had a car with CC that was so rock solid. And I love the cool feature of adding exactly 1 mph by tapping ACCEL and slow 1 mph by tapping COAST.

My cruise control has been rock steady.

Had mine since Halloween and have had no problems. Always smooth.

ok having read this thread and the previous thread from the link i have an idea- what if it is not surging at a specific speed but at a specific rpm range? perhaps the speed your setting it at is right about where the secondary or tertiary ports open. as the car moves up and down the rpm range slightly going up hills or downhills the port is open and closing. even slight grades might cause it to fluctuate enough to make this happen. what do you think?

My first 8 (VIN 883) did it once when going up a long grade. I don't remember what I did to start it surging but it was going nuts until I turned the cruise off.

Both cars oscillate when cruising on a slight grade but most of the time it's not enough to make the speedo change.

Vince

Not sure if this helps but what about the gas?
It got to 15 degrees here last week and mine would not idle at start up until it warmed up for a few minutes. Dealer told me to stop putting premium gas in it and just put regular. I changed gas and it started idling again. He said they have the same problems with high end VW's.

Ok, i have the exact same problem with my car since day 1 . (august 5th) I took it in twice for various reasons other then that and menrionned it both times. 1st time they di nothing,(i knew more about the car then they did at the time) 2nd time they said the had to reprogram it and that it should be fine... to no avail, it's still doing it, not ALL the time but at about 110 KPH it's very frequent, above 115 kph it almost never happens. i'm barely using the car for the winter but i will keep on bugging them with that problem until it is fixed !!

what is the rpm, roughly, at 110kph in 6th gear?

I would estimate around 3350-3400... at least on mine (I have been making a conscious effort this week to use 6th gear on my way to work on a 55mph road to see if gas mileage is better under the magic 3250rpm point... I can go about 63mph and stay under there).

-Sean

that is pretty close to the 3250 point. i think this adds some weight to my arguement of the opening/closing port as a cause of the surge feeling.

I'll bet you're right... add in the fact that my speedo is 5% off due to 40 profile snowtires, and that would put the magic speed at approx 109.5km/h<=>3250rpm based on my car and crappy math skills.

-Sean

take note i didn't even try to do the math i wqaited for someone else to do it ;)

When my car was new and I would use the cruise control I never noticed any surging while holding one speed. However when I would change speed using the cruise buttons it would be very jerky. After a while the car smoothed out and now when I change speeds its very smooth.

The original post said he didn' t use cruize very much so I wonder if the ECU has to learn how to control the cruize control much like it has to learn how you drive. Just a thought. Try and use it a lot for a while and see if that helps.