VEMS 1.8t 630cc coldstart problems

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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Thu Feb 12, 2015 2:48 am

Great job. Is the idle still high?
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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Thu Feb 12, 2015 11:03 pm

Idle is still hight..... I've got a TB coming to fiddle with to see if I can set the resting point more in the closed position. No matter what I do I can't kill it's air supply any other way. I am going to go through it with a fine comb to see if it's pulling air from somewhere not that noticeable. I've read that a can of brake cleaner sprayed around the possible leak sites at idle will give me a clue as it will race the idle a little.
It's gone below 10f out now and the car hasn't been running since 5:30am , I'm about to go see how it starts right now.



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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Fri Feb 13, 2015 12:00 am

Had 10f on the dash and started right up again. Have to adjust the afterstart enrich again but it's going well.
I'm convinced there's something wrong with this TB. The revs were t dropping with the iac ref curve as it should have. I hadn't noticed before but the TPS % was at 5% on Vems. I tapped the throttle pedal slightly and it let go to 0% and the rpm dropped to where it should be following the curves. There's two pots in the TB for the TPS and iac, something's hanging up me thinks.


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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Fri Feb 13, 2015 12:00 am

Image


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Re: VEMS 1.8t 630cc coldstart problems

Postby SEStone » Sun Feb 15, 2015 4:12 pm

FWIW, that engine idles around -5 to 5deg timing stock depending on loads and such. Running such little timing gives a large 'torque reserve' as Bosch calls it, and really slows down response to help stabilize idle control.

I've tuned a handful of cars with 034 using open loop GPO-controlled idle using the idle motor plus the closed loop ignition timing control. Works a treat.
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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Tue Feb 17, 2015 12:31 am

I'm waiting on lugtronic to get back to me so I can get the knock control enabled(instructions per vems seem straightforward and easy to follow though) and to sort out the ign table. I'm not confident enough to go playing with the ign tables so much but retarding the idle blocks is ok I suppose, so after changing those blocks to 3 deg I will have surrounding cells at 14-15 deg , is that too much of a jump??


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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Tue Feb 17, 2015 12:40 am

I still have the P,I,D set to zero. Is there a default to start from with the 1.8t? I raised the freq for the iac to 200hz, I read something about it running at 400 or something with oem. it was at 25hz and was clicking alot, that stopped when I raised it.
Coldstarts are pretty decent now, I had it parked all night in 6f temps and it started first turn, the cold/warmup idle was hunting for the first 10 secs not sure why but lowering the ref dc tables slightly lessens it. I didn't think I'd have to be doing all this stuff but I suppose it's a good way to learn as long as I'm carefull and don't get ahead of myself


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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Tue Feb 17, 2015 1:49 am

Actually, this kind of thing is what takes the most time with tuning if you aren't used to it.

The valve is still clicking, just much faster so you can't hear it the way you were at 25 hz!

If you don't have PID tuned on the IAC, then it probably isn't doing much. I made a nice post here about tuning PID systems. If you use it, you should be able to get that thing working properly. Let me know if you have any questions about it. Even though it refers to boost control the whole time, you can apply it directly to the idle control valve or any other PID system.

http://theprojectpad.com/viewtopic.php?f=28&t=1252
-Chris

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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Tue Feb 17, 2015 5:15 am

Yup, I read it and it really is a great write up, I'm going to tackle it this week sometime hopefully. I will be re-reading it again before doing it.
The vems guide : Set the ref dc table so there's a steady idle around 200 above target, in all temps ,
the PID to bring it to control/correct it smoothly and quickly whenever there's a lot of variance and let the idle ign adv control take care of the smaller quicker changes.
What I don't understand is what brings the idle back down the 200rpm to where I want it after setting the ref dc as above?
All that will have to come after I get the timing idle corrected to bring the rpm down to in around the target 850, it's tough to get time but I'm enjoying learning none the less.


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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Tue Feb 17, 2015 5:32 am

Is enabling the P I D going to bring it (back down 200rpm)to target. Then it will Be taking away or adding to the ref dc as required to correct my idle in different conditions if the ign adv control doesn't get to it first??

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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Tue Feb 17, 2015 6:47 am

Attach your config so we can take a look.
-Chris

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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 1:58 am

Ok, I'll try and get time using my phones hotspot or when I get home later


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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 2:04 am

Is my understanding of the process somewhat correct or all wrong?


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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 2:25 am

I never set the integral increase/decrease limits to zero, do they need to be? I already have the p, I, d all zero.


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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Wed Feb 18, 2015 2:37 am

Not sure what you mean? Did you give an explanation of your understanding of the process somewhere?

If "I" is already zero, the integral limits shouldn't affect anything.
-Chris

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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Wed Feb 18, 2015 2:45 am

Ah, OK here is what you're talking about right?

Urtorsen wrote:Is enabling the P I D going to bring it (back down 200rpm)to target. Then it will Be taking away or adding to the ref dc as required to correct my idle in different conditions if the ign adv control doesn't get to it first??

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So the ref DC (DC = duty cycle) table is basically a pre-fill for the valve. You have to have some reference point for the PID to work from. Let's say the valve takes an arbitrary number of 20 to get the idle to 200 RPMs above your goal idle. The PID will then increase or decrease the duty cycle of the valve to control the idle. Under steady-state conditions, the PID would decrease that duty cycle to something below 20 to get down to your target or goal idle.

The idle air control valve is only capable of handling relatively slow, but high amplitude oscillations in RPM. For smaller, more erratic RPM changes around idle, the timing control is more effective (apparently).
-Chris

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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 2:56 am

Yes, that is exactly my understanding, but you sir, have a way with words!!!!


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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 3:24 am

I have noticed that when the iac ref dc is at higher values in very cold temps (-6 untill 20degC coolant temps) , the rpm will hunt and TPS % changes with it, I thought the TPS pot sender was supposed to be separate to the IAC valve in the throttle body.
So looks to me like the iac valve opens(like its supposed to)dragging the TPS pot up along with it(supposed to be independent?) in turn giving me more fuel(to match TPS position) on top of the warmup enrichment untill it drowns then recovers and on and on. If I blip the throttle a slight touch it lets the TPS% falls to zero and the rpm gets back to where I set it in the iac dc table. It never gives any hassle after its running 30-40 secs. I'm seriously thinking the TB isn't right


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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Wed Feb 18, 2015 3:40 am

Happy to help :)

Interesting that the TPS % is changing. I'm not sure what to make of that unless it is doing it because of the difference in pressure caused by the IAC opening and closing. I'm not sure exactly how your IAC/throttle is set up though. The RPM will hunt if too rich or too lean. Are you sure you aren't too lean?
-Chris

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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 3:43 am

I will test to see if it does the same when the engine is warm by raising the iac dc up to bring the rpm up to 2.5k and see does the TPS % follow


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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 3:45 am

No I'm on target for lambda everywhere, and it's around .95/.96 target idle , the ve table when warm is pretty good , the EGOC is never really active


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Last edited by Urtorsen on Wed Feb 18, 2015 4:03 am, edited 1 time in total.
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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 3:47 am

It's a 2 wire iac valve to injector output 6 I believe



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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 3:49 am

And not only changing, it seems to get hung up on 3-4% after the warmup , untill I toe it a touch then it falls to zero along with the rpm dropping to my target, I will definitely be testing this after work


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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 6:31 pm

So I've read some more about people bench testing the iac motor and OEM it's 400-500hz according to them . I upped it to 250hz, the max on vt. It takes a higher %dc to start waving the rpm, still brings the TPS with it but that's life as I don't see any way to have it nearer 400hz. Warmer weather(30f+)starts are a breeze so whatever.
Came home last night, parked it at 5:30am 8degf, hasn't gone above 10 all day. Started first turn at 5pm again.


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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Wed Feb 18, 2015 6:55 pm

You must work night shift too...
-Chris

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