bgillette79

Ok I was driving yesterday and was pulling down the on ramp. The turbo was fully spooled and there was no turbo lag.

What I did notice that really seemed odd was almost like a slipping or sputtering as the SUV climbed past 3000rmp up to near 5000rpm. The speed was climbing with full spool from 20-70mph. Yes I was heavy on the pedal to really get out ahead of a group of traffic I could see coming on the highway.

So this slipping or sputtering that I felt was SLIGHT and I don't think the others in the car noticed it, but I clearly did. Anyone else experience this? I will try to make it do it again today to see if I can pin point it more.

MMike1981

so..did the slipping cause a gap in acceleration? Lack of power? Any noises associated with it? was there a clunk? was there any kick back? how many miles are your car? how fast were you going when you noticed the oddness

one thing i always notice when accelerating at a high rate of speed, is that if you are WOT in 4th gear, when the RDX dumps into 5th, there tends to be what FEELS like a lull or a slip in accel, but ive always noticed a smoother increase in speed - but a difference in the application of power

bgillette79

I was in Drive mode, but I'd guess if I remember correctly I was in 2nd gear and 3rd gear pulling hard from 20mph to 70mph. It wasn't floored but I had it down about 3/4 of the way. there didn't seem to be a gap, or lack of power. No noise, or clunk. There was just a feeling that it had that it was "stuttering". I don't know how else to put it. It kept pulling and going, but there was a lack of complete smoothness that I've never felt before with it and I never felt in the test model I drove.

Right now I have almost 2000 miles on it.

It could be the gas in it maybe...I was stuck putting in 93 octance from a not so good gas station in the middle of PA during my camping trip last weekend and I still have 1/3 of a tank left with that fuel in it. My next tank will be 93 octane from Shell..V-Power!! If that doesn't fix it I'll be at the dealer for sure to have them ride around with me and see if they can notice it too!

MMike1981

hmm...so u were @ 70mph in 3rd?

catnippants

I have to be honest - my 2007 has ALWAYS felt like that when hitting the throttle on acceleration ramps - especially on a slight incline. It almost 'feels' like a miss. It's not turbo lag. The RDX power curve is definitely not silky smooth. Others have mentioned it before as well - which is why I never considered it a problem.

Mike

bgillette79

No...I mean the engine started in 2nd and went up to 3rd and when I finally let off the throttle around 65-70 it was in 4th and quickly transfered to 5th since I let off the reves.

I noticed the "stuttering" mostly from 30mph-60mph. So that probably covered 2-3-4th gears.

bgillette79

This was actually on a ramp that was a DECLINE onto a highway that maybe had a slight incline if anything. In about 30mins I'll be in the RDX driving again and I'll see if I can make it do it again so I can better diagnose it. Last night wasn't a good time to be doing it over and over again because I had 3 others in the car with me.

MMike1981

yea...thats what i was about to conclude as well...just seems like normal operation to me, just differences in the power band, maybe because you had people in the car and were hammering it at full spool, who knows, but it just seems like a linearity thing

unless you were experiencing actual engine knock/detonation or the computer sensed issues with grade of gas, i dont think its really an issue, you are just learning the operation of the RDX

bgillette79

As long as it is "normal" I'm cool with it...and will just expect it. If it were a knock/detonation what would I notice..what would I look for/listen for/feel for??

MMike1981

a bang, kickback, thud, thunk, clunk etc...depending on severity, either lightly or in your face could not mistaken what had happened

the trick is sort of predicting where you are when you know you are going to hammer the car...picking the sweet power spots...it will come with more driving, but ive always found the RDX to be unpredictable when calling for WOT or close to it, but once you, well i dunno, learn the car, you will know & it will be second nature, when you will illicit the most power from the car at all times...like floating the revs for a second or 2 before you hammer the power, or, feathering the pedal a little bit, see what works for you, but its not the same all the time.

R*D*X*

i always shift it to smode first before i floor my gas pedal, or drive it hard.

cwepruk

I think it's compressor surge.

Smaller turbos often have this issue at mid throttle/full boost openings. The airflow can't keep up to the pressure differential and that can cause the compressor to stall momentarily. It's a bit hard on the turbo. Solution is more throttle or more RPM

I've noticed it when the trans is reluctant to kick down and goes full boost. With a CAI, it makes a light chirping noise.

bgillette79

So maybe I will do what RDX said.

If I feel like "dropping the hammer" just throw it in S mode and when I'm up to speed just go back to regular Drive. That should UP the RPMs more quickly and thus eliminate what cwepruk is describing as compressor surge.

Sounds like a happy fix to me.

ps...I am running and Drop In K&N filter which should help give my engine a bit more airflow...wouldn't that help with the compressor surge too>?

cwepruk

I think the airflow is dictated on the other side of the turbo - there is limited airflow through the engine (throttle/rpm) but high boost/flow in the turbo. The engine can't use all the air. It was very common on the SRT-4 I had. You could probably experience this by going into fourth gear at 2000 rpm and put your foot to the floor. As the turbo gets near full spool, it can stall for a split second.

http://blog.streetfire.net/2008/05/t...sor-surge.aspx

bgillette79

Very interesting video.

Thanks

catnippants

I agree - you really need to 'learn' how to drive this car. I get a kick out of watching my wife try to drive my car. She can't drive it smoothly. The RDX is weird that way...

Mike