The V8 Owners Forum -

Right,

So I have recently installed an innovate LC1 wideband lambda kit so I am for the first time able to see accurately what my AFR's are when running.

This is in a Landrover 90, running SU carbs and Megajolt. Engine is a stock but rebuilt 3.5 lump at 9.35:1 compression. Mixer ring on each carb fed from the vap with a closed loop mixer valve on the feed to these.

My problem is this:

I seem totally unable to get the air to fuel ratio to drop into the 13's when accelerating hard. Using the main mixture adjustment and winding this out pretty far only seems to give me a maximum of around 14:1.

Having the main mixture out this far has required that the idle screw is wound completely in so that it ticks over stably. AFR on tickover is currently around 11 as of this morning.

I have currently got the manual power/economy valve opened all the way, so this should not be restricting any draw the engine may be putting on the vaporiser.

Cruise AFR's are fine as they are controlled by the oxygen sensor.

So- any ideas on how I can get the WOT AFR richer without my idle AFR getting worse?


Things I have checked are:

LPG filter- clean (only a couple of thousand miles old)
Checked for heavy ends- barely any at all.

One thing I have yet to check is what the stepper motor does on the motorised power/economy valve when open loop. It is currently set to go open loop at idle to prevent hunting. I have been assuming that it would just wind out and open fully, but i guess it could just centre itself which would restrict the suck that the vap feels on acceleration when taking off from stationary.

Failing any surprises with the closed loop system, the vap has done at least 30,000 miles without a rebuild- could this be causing my issues, or is it just down to me needing a better/different vap unit?

Thanks all

I can't specifically answer your question, but when I tried to set my 3.5 V8 up using a wideband, I also couldn't get an appropriate AFR across all operating conditions. I ended up with it perfect at idle, and lean at all other times....

I plugged about 1/2 the holes in the mixer to get the adjustment on the vapouriser to be about centred at 14.7:1

My mistake was to mix & match bits from eBay.

Perhaps your system isn't a 'kit' but a mixture of bits.

Chris.

Bought the whole shebang from Tinley tech as a kit a while ago, as specced for a landrover v8. Am thinking that maybe the vap unit is not big enough?

The idea on plugging holes may be an idea, although I'd rather not lean it out on acceleration anymore than it already is.

Recent mpg results seem to be promising though and performance is pretty good, so am tempted to leave it as is.

At MOT time I can set the Megajolt to not trigger the open loop condition on idle so should see 14.7 for the emissions test

So if I do go for another vapouriser, any suggestions? Have read a few things about OMVL 90 units being good.... true?

I have a Bigas sequential kit from Tinley on My 3.9 RRC, the vaporiser unit is small but has performed well over the past 7 years.

If you need advice I havwe always found them helpful

Is it worth posting some pictures up

Here's an old and slightly rubbish pic, the LPG setup is the same, but I am now using Megajolt for ignition (Ford EDIS coilpacks), and the rubbish Kenlowe fan control has gone, replaced with an x-eng one



The hoses from the Y-piece to each carb are the exact same length on each side, although they now route a little differently so that they aren't kinked or compressed at all.

If you bought it as a kit from Tinley, give them a call. Or better, make an appt and turn up.

Chris.