Early shift light? - LotusTalk - The Lotus Cars Community
 
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post #1 of 14 (permalink) Old 06-25-2019, 08:57 PM Thread Starter
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Early shift light?

Does anybody know of a reason for the Elise ECU to reduce shift light RPM to 7800? Is this indicative of a problem?

My car has consistently given the standard shift lights since I bought it:

6k cold
8k warm
8.5k 1st gear pull (or w/e terminology you prefer)

However today, I noticed at the end of a very long drive (hint: perfectly warm coolant+oil) that I was getting flashed in 1st gear at 8k. In fact it almost looked earlier than 8k.

To confirm, I watched it closely in a higher gear, which doesn't wind out so rapidly. I'm absolutely confident I'm getting my shift light at ~7800 rpm now.

It appears perhaps others have experienced similar

My major concern is that I've learned that the ECU can indicate minor issues through the red light rather than through the CEL.
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post #2 of 14 (permalink) Old 06-25-2019, 10:51 PM
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I have never really noticed it. Do you or can you bang the rev limiter?

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post #3 of 14 (permalink) Old 06-26-2019, 03:41 AM
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as far as i understand, the ecu function that determines redline uses a linear interpolation to choose the cutoff as coolant temperature comes up. i expect that if a driver pushes engine speed to it's limit periodically for the entire warmup, then the cold start would limit to 6k and the value would climb linearly with coolant temperature up to 8.5k (with a 1 sec limit before falling back to 8k).

additionally, the engine speed that the red shift light comes on has a gear dependent calibration. it comes on sooner relative to the actual redline for lower gears. also, as the coolant temp comes up, the shift light should move along with it.

edit 1: added tables from RomRaider that show the calibration, revealing that the Lotus intended behavior for the shift light is to turn on at different engine speeds.

edit 2: this means that when the car is functioning as intended, the shift light will come on at 7150, 7400, 7950 and 8150 rpm depending on gear (then, fall to 500 rpm below each of those between 0.2 and 1 second of sustained redline operation).
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Last edited by Obeisance; 07-03-2019 at 08:45 AM.
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post #4 of 14 (permalink) Old 06-27-2019, 08:33 PM Thread Starter
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Obeisance, thank you! That would make perfect sense given that it was a cooler air night and, despite having driven nearly an hour, coolant temps were probably slightly cooler than usual. Hmm.
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post #5 of 14 (permalink) Old 06-29-2019, 05:12 PM Thread Starter
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Well that wasn't it. It's 90 degrees air temp today and I tested after 40 mins driving in peak temperature, coolant was even up to 200 for a bit at a long stoplight. Still get light at 7800 in all gears. There can be no doubt that slightly cool temperatures were not the cause of slightly lower shift light.

I'm certain that this is caused by something and pretty sure it means something is running suboptimal.

Recent changes before this happened were:
- oil change and accidentally overfilled it a little. The overfill was so marginal that I decided to leave it.
- replaced IACV. That means removing some hoses and TB... It all seemed to go very smooth and I'm not sure how it could be related
- Had a shop install BOE toe links in under 3 hours, while I waited, which is so unrelated that it can't possibly be causal. However, it was strange that my trip meter was reset when they were done, which definitely shouldn't have happened ��

From my perspective, none of these seem like culprits but I'm positive this is a problem needing solving.
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post #6 of 14 (permalink) Old 06-29-2019, 06:35 PM Thread Starter
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Ah, very bad news. Checked oil again and the overfill amount is greater than it had shown after the oil change, and no longer appears trivial/harmless. It appears to be roughly 1/2 quart over, if not more.

I've discovered text in the owner's manual saying that oil should be checked while hot and that cold or luke warm oil after a drive will read artificially low. My standard oil change procedure includes a quick zip around the neighborhood before checking for leaks, which is definitely how I was fooled by a low reading.

I'm now concerned whether I might have harmed my motor.

Current theories:
- overfill lead to oil aeration (foaming) which lead to poor oil pressure and the car's shift light, perhaps, responds to low oil pressure?
- added resistance from crank splashing into oil has degraded power production so that I'm hitting the shift light's timer rather than purely RPM based light which is given only within sub-second windout time. The car has fealt slower but I wasn't sure if that was in my head.

I'd really love for somebody more knowledgeable to tell me where I'm wrong or right. Won't be able to oil change for several days and am super bummed. Probably won't be sleeping well until then either hah.
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Last edited by lance_mn; 06-29-2019 at 08:08 PM.
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post #7 of 14 (permalink) Old 06-30-2019, 04:24 AM
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Does your car have a Accusump system ?

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post #8 of 14 (permalink) Old 06-30-2019, 08:02 AM Thread Starter
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Quote:
Originally Posted by Partsfinder View Post
Does your car have a Accusump system ?
It is stock.

EDIT: I had never heard of the accusump prior to your post and it sounded like an aftermarket part. Perhaps it's an OEM option some elise's have?

Last edited by lance_mn; 06-30-2019 at 08:55 PM.
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post #9 of 14 (permalink) Old 06-30-2019, 06:55 PM Thread Starter
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Canceled some plans in order to fix the overfill today. 7800 shift light persists in all gears while running correct oil level.

Something is surely broken? Anybody have ideas before I head to the local Toyota dealership and give them a blank check?

As a last hope, I think I'll try the gauge cluster recalibration tomorrow (from the uberpost)

Last edited by lance_mn; 06-30-2019 at 08:54 PM.
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post #10 of 14 (permalink) Old 07-01-2019, 02:31 AM
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if it's any consolation, i don't think that your car has any problems or that the shift light is ever involved in displaying diagnostic information. further, i don't expect that it is adjusted in response to engine management apart from what i posted earlier.

if you have a CAN logging tool you can collect the gauge cluster control packet and compare all of the factors that the ecu uses to determine shift light operation.

also, do you happen to know what ecu calibration the car is running? B121E0002H? C121..? aftermarket?
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post #11 of 14 (permalink) Old 07-02-2019, 07:57 AM Thread Starter
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Gauge cluster recalibration did not help the issue (hold the trip button and move key to "run" while door is open).
I'm super bummed.

Quote:
Originally Posted by Obeisance View Post
if it's any consolation, i don't think that your car has any problems or that the shift light is ever involved in displaying diagnostic information. further, i don't expect that it is adjusted in response to engine management apart from what i posted earlier.
I suppose that's encouraging, so I appreciate that Ultimately I'm sure there is something out of order here, even if it turns out to be benign to performance. If I leave it undiagnosed, I'll forever wonder whether I'm making a bad problem worse and won't be able to enjoy myself in the car. Additionally it harms resale value.

Quote:
Originally Posted by Obeisance View Post
if you have a CAN logging tool you can collect the gauge cluster control packet and compare all of the factors that the ecu uses to determine shift light operation.

also, do you happen to know what ecu calibration the car is running? B121E0002H? C121..? aftermarket?
I don't know what a CAN logging tool is. Does it plug into the OBDII interface or elsewhere? I do have a buddy with an OBD2 log scanner and I can check for any codes that just aren't severe enough to trip the CEL.

I don't know what calibration I'm running. Is there a way to tell this without plugging into the OBD2 interface with a particular scanning tool? Also, once we know what calibration it's using, what could we do with that info?

I appreciate the hell out of you taking the time to help man

I think my next step is to remove the valve cover and look for anything obvious. I haven't had the valve cover opened up yet since I bought it.
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post #12 of 14 (permalink) Old 07-02-2019, 08:29 AM
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a CAN logging tool is a device that allows you to record the communications on the controller area network data bus that the car uses to communicate between microcontrollers. in the case of the Elise, such a tool would be able to access this data bus via the OBD port. there may be obd tools that are capable of logging raw CAN data, but I'm not familiar with such a device. i instead prefer hobbyist Arduino microcontrollers with CAN add on.

i guess logging CAN data would be a big leap for someone who has not previously done such a thing. also, i would only want to see this data to see if the car is operating as i expect based on my above posts (this is just me second guessing your anecdotal descriptions of the shift light behavior.. hopefully you'll excuse my skepticism).

the calibration number cannot be ascertained without the use of an OBD tool. obd mode 0x9 pid 0x4: Calibration Identification Number. a lotus dealer would also include this information in an ecu data dump.

i asked about this in case your car is running a different firmware version that does not follow the shift light command procedures that i assume based on the B and C calibrations.
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post #13 of 14 (permalink) Old 07-03-2019, 08:24 AM Thread Starter
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After the most thorough forum search I've ever done, I've found 5 people indicate that their shift light flashes at 7800.

- 1 of them was sure it is normal
- 2 were sure it's a problem but were encouraged by forum members not to worry about it. They apparently took the advice.
- 1 Solved it by doing a gauge cluster recalibration (did not work for me sadly)
- 1 Spent a ton of money chasing it down and apparently never solved it. His last post was a super frustrated list of all the things he'd tried.

I'm feeling pretty discouraged.

For the record, the problem is not normal and is not a failure in my ability to read my tach. I got to race the car at the drag strip once before this happened, I got in 8 passes, and I can tell you that 1st gear flashed at EXACTLY 8500 for all of those passes and the other gears flashed at 8000 for the rest of the passes - NOT 7800. This is in addition to all my tests on the street (dead country roads) equally scrutinizing. I did not bump my head and suddenly decide that the exact same flash point which once looked like 8500 and 8000 actually looks like 7800 now in all gears. If my car is not flashing at 7800, then that's because it's flashing at 7700. I can get to the red flash and let off the gas and push in the clutch all before hitting 8000.

I think that if mechanically everything appears un-impacted I'll live with it (may not have a choice). My current plan is to pop the valve cover and look for anything obvious and eventually get it back to the drag strip in similar weather conditions for 1 quick pass just to see if it has the same performance.

Last edited by lance_mn; 07-03-2019 at 08:43 AM.
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post #14 of 14 (permalink) Old Yesterday, 08:23 AM
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