Throttle travel - seeking 100% !!!

Topics relating to the Lotus Exige S1 (series 1)
ortope
Posts: 116
Joined: Sat Jun 13, 2020 11:40 am
Location: Switzerland

On my car I noticed that, when assembled to the head, the two throttle bodies tend to seize one against
the other in the closed position, causing the non complete throttle closure.
In order to get rid of the problem we lowered one part of the linkage and after this the throttle closed freely.

If needed I could pst some pictures.

Cheers

Adriano
# S1 016
C8LGY
Posts: 40
Joined: Thu Jun 13, 2019 10:27 pm

Thanks for the feedback guys, much appreciated. Looking again, the butterlies seem relatively smooth and the throttle snaps back to roughly the same place, the only thing I'm unsure of is why it doesn't flyback against a 'stop', as you can see here at the end of the video that I can close the throttle slightly further at the TB:

ImageUntitled by Colgy, on Flickr

and here you can see in this video that the butterflies are almost completly closed (although haven't actually balanced them yet!):

ImageUntitled by Colgy, on Flickr

Is the ability to push the throttle further closed normal? Cable is slack at the throttle end.
ortope
Posts: 116
Joined: Sat Jun 13, 2020 11:40 am
Location: Switzerland

This was exactly my problem.
Taking the two throttle bodies apart they both snapped back without any problem, but
reinstalled on the head due to a little distortion in the alignment this caused the problem
you are describing.

Before (oem):
Image

After:
Image

Cheers
# S1 016
Evoman
Posts: 136
Joined: Fri Apr 03, 2015 12:00 pm

I wouldn't have thought so Craig. I will try and check tomorrow. Does that also have the effect of pushing the butterflies a little more closed?

I did notice on mine the throttle cable bracket was slightly bent - it's not very strong metal. Maybe just the camera moving in your video but looks like the bracket has some flex / movement as you push home the throttle actuator? Might worth checking that too to make sure it isn't just the bracket limiting the correct movement of the throttle cable.
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trackrod
Posts: 335
Joined: Sun Aug 21, 2016 10:43 am
Location: Germany

I noticed the same thing as Evoman: it looks like the bracket of the throttle cables is moving towards the throttle bodies when you are using the screwdriver to forcefully close it. Is the throttle cable really slack? I would repeat the procedure with a fully disconnected throttle cable and see if things change.
C8LGY
Posts: 40
Joined: Thu Jun 13, 2019 10:27 pm

Thanks - I've done some more investigating, and wound down the balance screw and lo and behold it closes a tiny bit more. So I guess although it looks like the butterflies weren't fullly closed, one of them was starting to bind, preventing the rest from closing. :oops:


So now the throttle readings are more consistent; I had nice and steady readings from 10% - 98%.
ImageTPS by Colgy, on Flickr
The creaking is the cable, not my old knees....

Tried to calibrate it and it didn't seem to work, however after a couple of hours it has now changed from 3.5% - 92%. :crazy: I appear to be getting full throttle at the TBs and the throttle cable is slack at the pedal (~10mm of pedal movement before the cable is tensioned) - not sure why it isn't calibrating correctly though! :roll:
Evoman
Posts: 136
Joined: Fri Apr 03, 2015 12:00 pm

Have you adjusted the position of the TPS itself? That could be it if you haven't looked at this yet. When you install a new one it seemingly takes a few attempts for the ECU to recognise the new TPS.

I had similar pain of spending hours trying to figure out why the throttle range wasn't being recognised by the ECU with the OBD reading. Having apparently ruled out all mechanical aspects involving the throttle cable and linkage itself I did end up fitting a new Elise Parts upgraded throttle linkage and fitted a new TPS shortly after followed by the gear linkage upgrade too though that clearly has nothing to do with the throttle travel issue!
C8LGY
Posts: 40
Joined: Thu Jun 13, 2019 10:27 pm

I haven't adjusted the TPS yet, as not convinced that's required. Full throttle is now 95%, so the ECU is definitely doing some sort of calibration - still investigating this!

I know realise what really buggered me up was that I had the throttle pedal depressed about 20% to make access to the screws easier. At some point, I must have cycled the ignition and the car 'learned' the new position resulting in the car idling at 5000 rpm! I then backed right off the idle and balance screws, which then gave me further issues :crazy:

I also found that the pedal stop wasn't wound out far enough, so the cable was being stretched tight. This in turn was bending/flexing the bracket, so thanks for the observation - all fixed now and I still have full travel on the TB when operating the loud pedal.

With the TPS reading at 0% now, had a go at balancing the TBs. Started off by increasing the idle speed until just before speed actually started to rise (IACV fully closed) and worked from there; without doing this the readings were even further apart. Took me a while to realise that the idle screw opens all cylinders (but doesn't necessarily increase idle speed!), whereas balance screw just does 3&4. Looking at the previous results, the TBs were closed further at idle:

...............................................1..........................2...................... 3....................4

Initial..................................3.75................... 2.75...................1.5................2.25
Final.....................................4.6.....................3.6....................3.8................4.6

Cylinders 3&4 are the ones which are adjusted using the balance screw. You can see that the screw was too short, which meant that they weren't as open as cylinders 1&2. Cylinder 3 also appears to have been the one that was binding slightly, because it was further shut and prevented the other cylinders & throttle shaft from fully shutting. Doesn't appear to be an easy way to balance individual cylinders without modifying the TBs and I'm not sure how much difference it would make anyway. I tried a 0.5mm spring, but wasn't convinced that it would be good enough to stop the balance screw from rotating, so ended up swapping it out for a nut and spring washer. Getting there now!
C8LGY
Posts: 40
Joined: Thu Jun 13, 2019 10:27 pm

Just thought I would share some experiences here, for future reference when searching.

Calibration of the TPS seems possible by turning on the ignition, depressing the pedal a few times, and then leaving the igntiton off for a period. Each time this is done, it reduces the '% at idle' by approximately 3%. Therefore, if you fit a new TPS and it shows 15% with the accelerator depressed, you need to repeat the calibration about 5 times.

I enlarged the mounting holes from 4mm to 5mm to allow the TPS to be twisted CCW and reader higher than normal. This had the effect of shifting the range up, which is exactly what was observed; now the 100% was achieved with anywhere from 90-100% pedal travel (OBD reading never went above 100%), but the TPS input was 15% without the pedal depressed. When the calibration at no throttle was peformed, the range (or 'span' in control speak) remained constant, which meant ending up back where I started at around 95% TPS input with the TBs fully open. Also tried a new TPS for EliseParts which had a slightly different resistance range (and weirdly wasn't sprung - although no issue with fluctuations at idle), but made no difference after recalibration.

I'm not sure how much difference the <100% TPS will make, if the TPS is used just to tell the ECU of fast throttle change, as Klaus mentioned earlier. As I'm out of ideas on how to set the TPS range, I'm parking the problem for now!
ortope
Posts: 116
Joined: Sat Jun 13, 2020 11:40 am
Location: Switzerland

Interesting point.

:thumbup:
# S1 016
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