VEMS 1.8t 630cc coldstart problems

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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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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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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 7:48 pm

Yup, 10-12 hr shifts in auto-industry with a decent commute, besides the unsociable hours it's good in some ways, against traffic coming to and from work with a good crew to work with. Having a bit of daylight to play with before work is great too.


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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Wed Feb 18, 2015 8:27 pm

I work 12 hour shifts at night (for now), but I also sleep at work! This kind of schedule can be tough, but sometimes you gotta work hard for the money!

Sorry I don't really have any input on your situation for now. If the VEMS output can only operate at 250 Hz, that would definitely impact the functionality of a valve which is meant to be operated at double that frequency... Is there a way to use a different IAC?
-Chris

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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 9:07 pm

I could tuck an isv valve away under the IM for use during winters and delete during warmer weather. Two different maps. Maybe make a plugnplay pig tail to run from the stock harness TB connector and split it to two legs, TPS for the TB and then a two wire connector down to the ISV.


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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Feb 18, 2015 9:12 pm

Just a case of deleting the pigtail and deleting the lines to the isv come winter.
Why do they stop at 250 hz, is there any board modification or future changes to go higher freq??


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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Thu Feb 19, 2015 1:46 am

So the TPS and the iac valve are all the one.......and .....Well I feel like a fool for not seeing it or trying it sooner......but, I noticed the 'iac on' tab going green, on and off, as the rpm was hunting up and down. So the idle was getting switched off with TPS !! The iac motor would open the valve(throttle plate), in turn the TPS %(&rpm) would increase with it, reach the threshold of 1% and switch the iac control would drop off > valve closes bringing TPS below 1%, idle control would enable again below this 1% and it would keep cycling like that ......revving the engine.

so, I raised the 'TPS threshold for iac enable' from 1% to 10% to try it out (probably can drop it to Id say 5% later when I have more time to play) and the iac works perfectly with dc curve, it's -2f outside and started and idled fine.
Is there a downside to setting the threshold at around 5%????


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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Thu Feb 19, 2015 2:04 am

Image


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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Thu Feb 19, 2015 2:08 am

The IAC will just kick in sooner when letting off of the throttle and will keep going when you get back on it until you are past 5%. This may or may not hurt driveability depending on your tune and TPS. Try it out and if you don't notice a problem, keep it!
-Chris

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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Thu Feb 19, 2015 2:18 am

For now I'm leaving the PID off and just using ign idle control, ......once I'm at 60deg the ref dc is zero so it won't do anything anyway.
It seems to drive fine with the PID control dissabled but ....
Like you said I will see what it drives like when I have the PID set up and the TPS threshold at that setting, hopefully it will behave!!


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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Apr 15, 2015 2:25 am

Been playing with this thing trying to get it working , but only using the iac dc untill coolant is at 70 deg then dropping it to zero and letting the ign advance do the rest. I tried using PID to control it at all temps but it's horrible, and it's no wonder, the OEM control is a little more complicated lol. Taken from another persons report on testing:
"I scoped the two wires driving the DC-motor in the throttle housing. At steady idle it is stable with a frequency of 500 Hz and a period of about 0,4 ms period. I gave it some throttle and let go. When the ecu senses the rpm going down it inverts the signal to the motor. Then when the idle is stable again it switches back"

So I'm thinking of using a 2wire bosch iac valve as it doesn't seem like VEMS has or will have capabilities to mimic the oem control of this system.

The valve I'm planning on plumbing in is a bosch
0280 140 516
The iac is setup as INJ output 7 , and as pwm. Is that suitable for that type IAC valve??? Do I need to worry about messing anything up or safe enough plug n play and change reference dc values and maybe frequency. It says it uses 1A & 9V fully open.
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Re: VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Apr 15, 2015 2:27 am

For anybody wanting to read the full thread http://www.msextra.com/forums/viewtopic.php?f=4&t=38238
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VEMS 1.8t 630cc coldstart problems

Postby Urtorsen » Wed Apr 15, 2015 2:43 am

Was also considering this as It looks nice and plumbing would be neater. http://www.diyautotune.com/catalog/cust ... -p-69.html
Looks like it's a 4 wire stepper though, bit more wiring and config changing....looks cheaper and easier to get the bosch pwm
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Re: VEMS 1.8t 630cc coldstart problems

Postby loxxrider » Wed Apr 15, 2015 4:50 am

Your description of how the valve works when scoped on a stock setup sounds like how it should act with properly tuned PID. Not to sound like a jerk, but I don't think the OEM control is any more complicated than what VEMS is capable of providing. I think you just haven't tuned it properly.

Have you read my guide to tuning PID?
-Chris

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