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... SAYING this - my build on my SS is 4/15 and I have none of these problems Vin# 4865 - and that tells me they have done some thing about these problems. My SS is the LE - so unless they only corrected them on LEs the new ones shouldn't be having these problems.
Doug
no such luck. Mine was built in May and it's had the rev hang issue from the very first drive.
 

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no such luck. Mine was built in May and it's had the rev hang issue from the very first drive.
Funny.....Mine has very little noticeable rev hang. I have to focus on it to notice. It drops revs almost immediately. No rev flare yet either. I have the low RPM stutter, but it has not once stalled. Almost 4000 miles now. I often drive aggressively on the empty back roads.
 

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update on a May/15 build...in addition to rpm hang, it also had rpm flare a couple of times, went from about 2k to 3k mid-shift and tried to stay there for several seconds.

If I drive it very conservatively, easy acceleration - the rpms drop normally as one would usually see on a vehicle. As soon as more acceleration is applied the rpms hang. Sure seems like it's trying to burn off unspent fuel.
 

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Just had my first RPM flare happen to me the other morning. I didnt realize what was happening until after it happened and then remembered reading about it on the forum and realized Oh ya this is what they mean. Neverthe less it still scared the crap out of me. I have less than 300 km on my machine, Canadian version.
 

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From reading others posts and personal experience, rev hang/rev flare seems to happen due to the ECU [over] compensating when the driver is "lugging" the engine. Searching "rev flare" across all threads and not just in titles, it seems a cat delete solves the symptoms.

Personally, and I have no concrete testing to back this personal opinion up, rev hang/rev flare seem to stem from the unusual ECU mapping combined with predictive load compensation. If an engine sees an increased load (such as driving up hill) without increasing the fuel supply, RPMs drop (the vehicle slows down). On vehicles with an ECU and "fly by wire" throttle (like the Slingshot), the computer can compensate for a potential decrease in RPM, providing a better, or at least more consistent driving experience (whether or not this is viewed as "good" depends on the driver). Polaris has a custom ECU mapping, which is non-typical for what is normally seen in the industry. I believe the load compensation, combined with "odd" mapping, on a very light vehicle, add up to rev hang and/or flare, depending on many factors such as temperature, air density, intake pressure, driving style, etc. So while the initial premise of load compensation is beneficial from an engineering standpoint, the execution has a few bugs to work out.
 

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Shortly after passing the 9k mile mark, I noticed my SS now no longer has a consistent rev flare or hang. It certainly still has them, but they now seem to come and go at their own discretion, regardless of how I drive. I find this new "feature" to be much more irritating than before as I at least knew what to expect and how to deal with it. The engine is still stock. Anyone else having or had this issue and/or heard of a fix for it?
 

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From reading others posts and personal experience, rev hang/rev flare seems to happen due to the ECU [over] compensating when the driver is "lugging" the engine. Searching "rev flare" across all threads and not just in titles, it seems a cat delete solves the symptoms.

Personally, and I have no concrete testing to back this personal opinion up, rev hang/rev flare seem to stem from the unusual ECU mapping combined with predictive load compensation. If an engine sees an increased load (such as driving up hill) without increasing the fuel supply, RPMs drop (the vehicle slows down). On vehicles with an ECU and "fly by wire" throttle (like the Slingshot), the computer can compensate for a potential decrease in RPM, providing a better, or at least more consistent driving experience (whether or not this is viewed as "good" depends on the driver). Polaris has a custom ECU mapping, which is non-typical for what is normally seen in the industry. I believe the load compensation, combined with "odd" mapping, on a very light vehicle, add up to rev hang and/or flare, depending on many factors such as temperature, air density, intake pressure, driving style, etc. So while the initial premise of load compensation is beneficial from an engineering standpoint, the execution has a few bugs to work out.
Thanks. I guess for what it's worth I'll try the chisel method or buy the cat delete. It almost sounds like the back pressure from this restrictive cat is screwing things up. I guess worst case scenario is it doesn't fix but then again might reduce some heat on the co-pilot side.
 

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update on a May/15 build...in addition to rpm hang, it also had rpm flare a couple of times, went from about 2k to 3k mid-shift and tried to stay there for several seconds.

If I drive it very conservatively, easy acceleration - the rpms drop normally as one would usually see on a vehicle. As soon as more acceleration is applied the rpms hang. Sure seems like it's trying to burn off unspent fuel.
I have the same exact issue! If I shift slow and smooth I get no flare, but if I shift at a higher rpm it flares and sticks for a few seconds. Not a big deal to me, I learned to live with it but would be nice to get it fixed!
 

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...... rev hang/rev flare seem to stem from the unusual ECU mapping combined with predictive load compensation. If an engine sees an increased load (such as driving up hill) without increasing the fuel supply, RPMs drop (the vehicle slows down)......
Can you please explain how is the ECU supposed to detect engine load? Which engine sensors would provide this information in an M/T vehicle? Certainly the RPM signal on its own would not be sufficient.

I have my own explanation of rev hang backed up by test data that I already published here. I also mentioned a stand-alone fix called CUREVS I developed for any car with indirect EFI non-turbo induction. I do not own an SS and have no opportunity to access one for confirmation of applicability/suitability of my fix. Further to previously posted info I have now incorporated an additional function improving engine braking with throttle off for vehicles with delayed or non-existent "fuel cut-off on engine overrun".
 

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@stevenj: You'd have to ask someone with the cracked ECU code. I know when I load the engine, such as letting out the clutch in reverse, then backing up a hill the engine adjusts to the initial load of starting the vehicle moving (and over-shoots), then takes the RPM back down to normal, then on the hill adjusts again even with the longer duration of the load. The same happens when driving in forward gears. It's different from other ECU vehicles on that it over-shoots by a good amount and is very noticeable (and consistent). There does seem to be some sort of limit set as to the speed and amount of adjustment.

I have an on-board computer in my much older truck that taps into the ECU, and the amount of information it pulls in real-time is amazing, especially since newer ECUs monitor even more. HP, torque, throttle position, RPM, speed, instantaneous fuel usage, O2 sensors, intake temp, intake pressure, timing, and way more,a full page of information, real-time. Therefore I can't guess at how Polaris software works, especially since we know it's highly customized.
 

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: .....I know when I load the engine, such as letting out the clutch in reverse, then backing up a hill the engine adjusts to the initial load of starting the vehicle moving (and over-shoots), then takes the RPM back down to normal, then on the hill adjusts again even with the longer duration of the load.....
What you described when backing up a hill is understandable with constant throttle opening. You normally start moving vehicle from a standstill with a fair bit of throttle and as you hold it steady the RPMs climb or fall depending on the resistance the motor has to overcome (e.g. steepness of the hill). I do not see any "predictive loading" at play here.

When there is any overshooting you mentioned it would be the consequence of change in throttle setting (reduction in pressure on the throttle pedal) the driver applies as the car starts moving. It is the rev hang (delayed reduction in power) directed by the ECU that is causing the overshooting, as in any other situation when throttle is reduced suddenly from higher revs.
 

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Discussion Starter · #438 ·
I have codemans exhaust and a cai and it's still revs/hangs at 4k and bogs when stopping. I have had the throttle sensor replaced twice.
 

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No solution here, but perhaps supporting evidence... I rarely get the RPM surge, maybe twice in 4K miles, but when I had the clutch stick halfway to the floor and trying to drive (before I found the solution here), it RPM surged like mad, even a crazy one hanging at 6000rpms for about six seconds. No more rev hangs since regaining full use of the clutch. Wondering if not depressing the clutch all the way to the floor during shifts could be causing it somehow.
 

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Can you please explain how is the ECU supposed to detect engine load? Which engine sensors would provide this information in an M/T vehicle? Certainly the RPM signal on its own would not be sufficient.

I have my own explanation of rev hang backed up by test data that I already published here. I also mentioned a stand-alone fix called CUREVS I developed for any car with indirect EFI non-turbo induction. I do not own an SS and have no opportunity to access one for confirmation of applicability/suitability of my fix. Further to previously posted info I have now incorporated an additional function improving engine braking with throttle off for vehicles with delayed or non-existent "fuel cut-off on engine overrun".
What you described when backing up a hill is understandable with constant throttle opening. You normally start moving vehicle from a standstill with a fair bit of throttle and as you hold it steady the RPMs climb or fall depending on the resistance the motor has to overcome (e.g. steepness of the hill). I do not see any "predictive loading" at play here.

When there is any overshooting you mentioned it would be the consequence of change in throttle setting (reduction in pressure on the throttle pedal) the driver applies as the car starts moving. It is the rev hang (delayed reduction in power) directed by the ECU that is causing the overshooting, as in any other situation when throttle is reduced suddenly from higher revs.
First, that's not what I said. Reverse is without using the throttle pedal at all. Forward is holding the throttle pedal constant, with my overly massive foot pinned against the transmission hump to be sure. I've driven and raced a load of stuff since being old enough to steer, pretty sure I'm qualified to work a throttle.

Second, it's been made exceedingly clear in the last 22 pages over six months the Slingshot uses a fly-by-wire system. I shouldn't have to explain the basics of how that works.

Third, like many of the other people with similar commentary, I drive and wrench a Slingshot, and know how it reacts. While I don't have the ECU code, I, like many people, know the system reacts as reported over the last six months.

Fourth, the ECU system is non-standard. It seems from various threads those who don't own a Slingshot have difficulty understanding their experience with other vehicles does not fit smoothly into how the Slingshot is designed and how it works, and can be very adamant the Slingshot doesn't perform as the owners are describing, but rather the owners are misinterpreting or have a lack of knowledge which leads them to be incorrect in their statements. I posted the link to the very reputable shop that cracked the ECU, maybe you should try telling them they don't know what they're doing and see how it goes, because you telling me that I don't know what I'm doing is not going well.
 
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