Yep, this is the kind of thing that could doom the SS. We have well under a hundred delivered that we know of and this sounds like it's a pretty common thing. Think about the effect only a few out of Millions of units had on Toyota and earlier, Audi.
This seems widespread enough that I'm wondering if Polaris attempted the same rev matching on downshifts feature that some performance cars (Vette, M4, etc) are including. Maybe they tried and didn't test enough to get it right.
While I agree that bugs will be found (ala a loose battery cable), things like this should NEVER happen with ANY vehicle. Regardless of price. Regardless of manufacturer.
This is the sort of thing that can cause, oh, I don't know - ummm, DEATH!
Since so many people are experiencing this and quickly, I can't believe that Polaris didn't catch it with test mule vehicles.
And you are correct - 'timely' means yesterday. And yes, production should be halted until this is fixed.
I'm curious though - any mechanic types here? Sounds like this is an ECU issue versus something mechanical. Can any knowledgable folks chime in?
As a designer and manufacurer of ECUs (for the experimental aircraft market) I think I can chime in. It definitely sounds like an ECU/FBW problem. I assume FBW is integrated on the SS ECU. Polaris can't even point to floor mats as the cause
I designed a Fly By Wire version of my ECU but while in test I experienced uncommanded throttle responses and even though I eventually found the probable cause it freaked me out so bad I canceled plans to market it.
The only time a car ECU should make any independent adjustment to the throttle is for cruise control. Only exception is for rev matching which is why I speculated that maybe Polaris or GM tried to implement that function and blew it. It IS a hard thing to do.
If it is an ECU problem, I can't imagine that any dealer mechanic is qualified to address it. If it's a mechanical hang-up of the electronic throttle pedal they might.
Yes a MAF could cause it but even if it is the problem is usually a small piece of lint or other object on it and usually isn't faulty. GM'scan have an issue with MAF and not set a code. We usually clean them with electrical cleaner and re install them. Its also a good idea to go through the relearn process after cleaning also. K&N filters will often cause an issue with MAF due to the oil residue getting on them.
Unless the MAF is integrated into that curved piece of air duct just after the ail filter, I can't spot one under the SS hood in the photos. There is an electrical connector going to that duct but that looks like the inlet air temp sensor. If there isn't one there, this must be a speed density EFI system that doesn't need one. Anyone out there with a SS see a MAF sensor?
The C7 Corvette and M4 both have manual trans rev matching. The purests don't like it because there is no excuse for heel & toeing but the ECU does a great job of this if done right.
I guess im trying to make friends. Dont want ro make anyone mad. I have a friend that has an old datsun. And way to much money. He is dropping a fresh gm 2.0 ecotec into it. And the guy installing it pointed out several shortcomings of the intake tract. He said all of them cound be overcome by software. But the placement of what he thought was the mass air metering device (which is directly behind the throttle butterfly) was going to be difficult to meter exactly. Now seriously he got way above my pay grade at that point. So I needs another tech to go out and see what he was talking about
You got that right. Just downstream of the throttle body is a HORRIBLE place to put a MAF. If it is the modern type (hot wire) type, they depend on the airstream being more or less smooth laminar flow. The throttle plate at anything other than WOT is going to introduce all kinds of turbulent flow. Even that kink just above the TB could be problematic.
I know, this is all speculation but working with airplane builders all over the world made it necessary to diagnose problems with minimal information and I kind of enjoyed the puzzle solving aspect of it.
The SS version of the LE5 does not use a MAF sensor but rather use the aforementioned AIT sensor mounted in the intake tube and a MAP sensor mounted in the intake manifold. So that explains that.
Thanks Orangeman, that explains it. The SS uses a speed density system so we can eliminate MAF sensor as a possible cause. MAP sensors are immune to the types of problems that MAF sensors have.
After reading NW's post above I'm starting to think 'high hanging rpm' is just another anomoly caused by the intentionally slow throttle response that Polaris programmed into this ECU. i.e. you suddenly let off the throttle then suddenly punch in the clutch - the engine revs because the throttle body hasn't responded to the gas pedal yet but the load is suddenly taken off the engine.
This may also explain the perception that some have reported that the SS has dissapointing power. They probaly perceive power as that sudden surge of torque when hitting the gas pedal. The slow response to the pedal is probably intentional to increase the final drive belt life in the SS.
If you want to test this theory, rev the engine to 5000 or so, floor the throttle and pop the clutch in 2nd gear from a full stop Let us know what happens if you're crazy enough to try it.
I agree with Otter. Drive By Wire systems can be programmed to effect a desired end result such as belt life. I have thought for some time that was the case here. But if that were true, why would Polaris be so concerned about their own programing and be studying their own rev issues?
Does not add up.
My guess is that the engineers already know the story but the PR & management guys can never admit that there are any compromises in their product. It's the 'We're perfect' syndrome.
I would have prefered that they had no nanny function other than ABS and ESC but included a caution against abusive use of the throttle to increase belt life in the operator manual. But that would have been admitting to the design compromise thing.
I can see this, but isn't it very hard on an engine to be sitting at 5,500+ RPM without any load applied for 5-10 seconds as a way of "helping" the inexperienced? (This is how I first noticed it, took off really quick, then had to stop for a sudden red, so clutch in and foot on the brakes, took about 10-11 seconds for it to finally figure out I wasn't going to upshift or what ever...)
I've always been told to avoid high RPM with no load to the engine.
The quicker the sequence of throttle off to clutch in (especially from high throttle) the more you would notice the 'high hanging rpm' thing.
Driver habits and different situations probably account for the differing reports from owners. I'm surprised it took 10-11 seconds to for the ECU to figure out what to do though. Polaris may have taken this slow throttle response strategy a little too far.
Stan's thoughts on this helping new standard shift drivers when downshifting could be another reason. If entering a turn and downshifting, breaking the rear tire loose because of too low engine rpm could really surprise an inexperienced manual driver.
I'd agree, the first two times I noticed it was when I made my first aggressive run with it, and shifting from 2nd to 3rd and was a bit confused. The other was another hard run and a "damnnit there is a red light" and pushed in the clutch.
Curious. Were you holding the clutch in during that long rev hang?
If it happens again (hanging for 10+ seconds) and you think of it, try shifting quickly to neutral and let out the clutch. The clutch position switch may trigger the ECU to knock off the rev hang.
If it didn't and the transmission was in gear. this really WOULD be dangerous.
This is why I was concerned. Blipping the throttle, releasing the clutch in neutral, etc did NOT stop it. ALl of the standard things that I would have thought could stop it didn't.
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