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33421

General Discussion Area / Re: LPG idle - back to the drawing board?

« on: 04 January 2008, 11:54:22 »

Went out this morning, for a little drive. Once the vaporisor hit 30deg she went straight onto gas. Drove for a while with no problems. Pulled back up afterwards, and the idle was hunting again, on gas only  

 

Measured the battery boltage with engine running - just over 13v, and a little blip raised it a touch.

I would still expect nearer or just over 14 volts so something is not right.

Maybe I wasn't closer to narrowing it down after all...

I think you probably are. Something is odd with the supply volts. If they're up and down, the LPG ECU will be chasing it with the injector duration to compensate for open/closing time.

Given the pressure is OK, I'm wondering if there is a problem with the injectors. The software is reporting them as "too big" when calibrating, I just wonder.....

True, but they were also maxing out under full throttle so I wouldn't go any smaller :-/

What injector duration is it running at idle (LPG and petrol)?

I would follow Mark's suggestion of an analogue meter on the battery. I suspect the volts are all over the place. Cold weather = more electrical load and poorer battery performance so it makes it worse.

Kevin

33422

General Discussion Area / Re: MOT Done

« on: 04 January 2008, 12:26:28 »

The emmisions test slip - what is what in it?

As in what do the numbers mean?

The prime measurements are Hydrocarbons (HC), Carbon monoxide (CO) and lambda.

You'll normally have a set of figures for natural idle and fast idle.

Limits for these typically as follows although later cars may well have manufacturer specific limits : CO<=0.3%, HC<=200ppm and Lambda 0.97 - 1.03.

Kevin

33423

General Discussion Area / Re: Air Compressor

« on: 28 December 2007, 14:28:07 »

Just bought a tiger 8/44 myself. Like any direct drive compressor it's a bit noisy but appears to be nicely built. Have only used it to pump up a few tyres and blow the dust out of my PC so can't comment much further but it looks to be one of the better quality compressors I've seen at that money.

This is an oiled piston type compressor but they do a similar range of oil-free ones at about the same price with slightly lower air delivery. They might be a better bet for spraying, I suppose.

Outlet is a 1/4" union, not a decent coupler, but it's easily upgraded - see Screwfix link above

Kevin

33424

General Discussion Area / Re: The 3.2/2.6 O2 sensor mystery.

« on: 03 January 2008, 11:34:10 »

What do you guys think of it

Got to be worth a try, I guess. Like most lotions and potions for use as additives they make some impressive claims. Whether it's snake oil or not remains to be seen. At least you have a problem at the moment, so you will have an idea whether it's done anything or not.

I am sure the use of a few resistors or resistor-zener setup would do a nice job of keeping the ECU quiet.

I wonder if the ECU is clever enough to look for activity on the post-cat sensor when the cat is cold, and verify that it disappears when the cat gets hot, or if it is enough just to never have any activity...?

Kevin

33425

General Discussion Area / Re: The 3.2/2.6 O2 sensor mystery.

« on: 03 January 2008, 10:16:46 »

Your right.....he knows nothing (but doesn't claim to!)

He He. If in doubt, give it a good spanking! A proud graduate of the Italian school of car care!

Kevin

33426

General Discussion Area / Re: The 3.2/2.6 O2 sensor mystery.

« on: 03 January 2008, 09:18:45 »

Thanks for the information. Interesting... I guess the pre-cats are the devices in the elbow of the exhaust where it turns rearwards below the manifold? Always wondered what was in them, and why the post cat sensors weren't behind what looked like the cats :-/

Given that MOT emissions are still fine without them, and that their only purpose appears to be to drive  the emissions light, the bodger in me wonders if the signal from the post cat sensors can be spoofed to keep the ECU happy? After all, I'll replace the cats when the emissions are no longer MOT compliant, not when a light on the dash tells me, thanks.

Kevin

33427

General Discussion Area / Re: LPG idle problem - THINK I've cracked it.

« on: 04 January 2008, 00:07:36 »

Oh, and try to do without the seat heating and all other luxuries until you sort it because I suspect the new battery will end up going the same way as the old one

Kevin

33428

General Discussion Area / Re: LPG idle problem - THINK I've cracked it.

« on: 04 January 2008, 00:06:04 »

I guess if the battery was poor, or in a poor state of charge, varying electrical load would cause flickering (in the absence of the full alternator output being available) due to higher internal resistance of the battery, so yes, the battery has cured the flickering for one of those reasons, but I still suspect the root cause is either a dodgy connection at the battery terminal (where the alternator output connects, placing resistance in series with the alternator output) or a problem with the alternator giving poor or fluctuating output.

The positive terminal was suspect when we fitted the LPG so that's the first thing to address IMHO.

Kevin

33429

General Discussion Area / Re: LPG idle problem - THINK I've cracked it.

« on: 03 January 2008, 22:32:17 »

Check the voltage across the battery at a fast idle with no load on and then with a few loads on and see what's going on.

Also, see if you can get a voltage reading between the positive terminal and the strands of wire going into the crimp connection. Might tell you if you're dropping volts at that connection.

If the terminal is getting hot that's a sure sign that all is not well.

Kevin

33430

General Discussion Area / Re: LPG idle problem - THINK I've cracked it.

« on: 03 January 2008, 20:11:56 »

My reasoning is this. I rekon there is a poor connection in the alternator to battery positive+ cable. This is confirmed by the terminal getting hot and wire looks bad.

Hmm. Battery needed a jolt from the charger before it would start in my garage post-LPG fitting, then the +ve terminal got 'kin hot when it started...

The LPG ECU only read around 12.5v running, too, IIRC.

Can you remake the positive terminal with a new terminal - even as a temporary measure - or is the cable too far gone?

Wobbly battery voltage could explain a few of your LPG troubles I reckon.

Kevin

33431

General Discussion Area / Re: The one extra missing from my Elite.............

« on: 02 January 2008, 20:21:42 »

 

Kevin

33432

General Discussion Area / Re: The one extra missing from my Elite.............

« on: 02 January 2008, 20:08:57 »

Mine has an intermittent setting but no adjuster (MV6). I wonder if it's just a stalk change? Just looked at the wiring diagram for the wiper switch and it's giving me a headache! Bear with me...

Kevin

33433

General Discussion Area / Re: More Jeremy Clarkson....

« on: 03 January 2008, 14:13:59 »

Hmm. It's a sign of how bad things have got when you can read that and think "Well, actually....".

Kevin

33434

General Discussion Area / Re: Performance section

« on: 03 January 2008, 15:27:58 »

Just remembered. I have been putting all these performance musings together into a document. Watch this space.

Kevin

33435

General Discussion Area / Re: Performance section

« on: 09 December 2007, 20:21:35 »

There are lots of high flow cats on the market, just look at say VXR8, it will have two cats that can flow more than any Omega's cats, as for the induction system the car maker will do it's best to give you best of all worlds, as we all know, it's a trade off, power = noise, Car makers love QUIET Comfortable cars  

There may be small improvements to be had in the cats, but I've yet to see any improvement to the unduction system.  Most of the 'improvements' increase noise and decrease performance...

Taking off the cats will gain more power as the exhaust will flow better.
 I bet if someone was to have the whole lenght of the induction system tested for flow, you will find that you could impove on what Vauxhall has done and the same for the head/s and exhaust system, but it's all about the cost and time and a very good workshop

The problem is, in any system, there'll be one component that is the weakest link. Change anything else and this component will still be your achilles' heel.

Yes, you might get a horsepower or two by changing other parts but it won't be worth the effort.

GM clearly went to a lot of trouble with the induction system. They didn't have to fit the complex multiram setup and it's there to give good torque over the whole rev range, particularly at low RPM which is important for a heavy car. I don't doubt that a few BHP could be gained at high RPM by removing it, but it'd be at the expense of a lot more at lower RPM and wouldn't result in a faster car on the road.

The throttle bodies are plenty large enough for 200 BHP, IMHO.

The weakest link is reckoned to be the exhaust manifolds which are how they are for packaging reasons rather than performance. Unless you change them for a tubular manifold with properly designed primary lengths rather than a "3 into 1" at the cylinder head you may as well leave the whole setup standard IMHO.

Kevin