pre 2000 honda civic 1.5 any valve issues?

[marcos]

Hello All,

Thinking of getting a low mileage Honda Civic Aerodeck 1.5l for my next workhorse will be from 1997 - 1999 model year. (I've got an aversion to anything too modern!)

Anyone know if these convert well? I have heard bad things about valve seat recession on Hondas, but perhaps it's only newer models affected. Would be grateful for any advice.

[LPGC]

Does need a lube.

Easy enough conversion.

Ignition systems aren't always in great order, OBD1 doesn't necessarily bring any issues with the myriad of Honda engine sensors to driver's attention. Running on LPG would be more likely to bring such issues to your attention - Of course not the fault of the LPG system, such issues would be an aspect of the car which should be repaired to get the most out of the car in any case.

Put an earth to the grey wire behind the passenger foot-well side panel, OBD1 errors are then displayed as a flash code on the dash (find the flash codes on the net).

Simon

[marcos]

Thanks for the reply,

This model is known for having soft valves then?

Probably enough to make me give it a miss.

I prefer an older vehicle (no plastic manifold) as I would use a mixer system to avoid having to start on petrol but I can't deal with soft valves.

Never used valve lube in last 15 years on LPG and not keen to start!

Shame because Honda motorcycles are bullet proof

Marcos

[LPGC]

Usually Asian and Ford (including Ford based), quite a lot of later model European stuff and the odd Yank with softer than ideal valves.

Wouldn't worry about it too much, just fit a lube it doesn't cost much to run a lube system.

Regards my point on engine sensors, a mixer system wouldn't be affected if problematic sensors affected fueling but would advise a sequential system nonetheless.

Don't be too put off!

Simon

[marcos]

I've run daihatsu vehicles for 40, 000 quite hard miles with no valve issues and before that a mazda which was no problem either. It's a real shame if honda have started using second rate materials in their engines.

If a nice vehicle turns up I might be tempted just to try it without valve lube as I don't really like the idea of adding an extra pollutant to the exhaust which shouldn't be necessary anyway.

If the valves all burn out I'll report back!

As for sequential, i'm not convinced the advantages outweigh the need to carry on using petrol on a daily basis. With mixer systems I only use petrol if I happen to run out of LPG, i'd hate to start having to use a steady amount of the filthy stuff!

[rich r]

Sequential injection LPG systems only use petrol for starting on, same as mixer systems. The only real difference is that the LPG is introduced in more precisely controlled quantities close to where the petrol would be injected.

I think you may have got confused with direct injection engines requiring petrol flowing through the petrol injectors to cool them.

[marcos]

You are right; sequential systems only use petrol for starting but you are incorrect that mixer systems must also do this.

I know because I have 15 years of LPG motoring using petrol only in the event of running out of gas!

This is the reason I believe any benefits of sequential systems are cancelled out by the need to start on petrol...

[Gilbertd]

Standard setting for a singlepoint is to start on petrol but switch over immediately it is running, so you are looking at running on petrol for a matter of a couple of seconds. Unless it is set to start on LPG of course. A multipoint on the other hand, has to run on petrol until the cold running enrichment (think choke) is off so you'll do at least a mile or so on petrol, more in winter.

[marcos]

I've always set mine for gas starting, never been a problem for me, in fact some of my vehicles have the petrol system removed completely.

A multipoint on the other hand, has to run on petrol until the cold running enrichment (think choke) is off so you'll do at least a mile or so on petrol, more in winter.

This is exactly my objection to multipoint: running petrol for the warm up cycle. It wouldn't bother so much to do a mile on petrol with a warm engine but with cold start enrichment? No thanks!

Unless there is a multipoint kit with injectors which definitely won't be ruined by cold starting on gas (anyone got more info on this?) , I guess i'll be sticking with 'archaic' mixer systems.

[LPGC]

Marcus, it is possible to have valve issues without having apparent engine problems. Worn engine valves/seats is an issue in the context it may reduce engine performance / efficiency, also in the context it means the engine (well, cylinder head) is nearer to needing expensive repairs (certainly needed when loss of compression occurs). Without checking, your engine valves might be like brand new, then again they might have worn a great deal. You'd have to compare performance between like vehicles and/or remove cylinder heads (failing examining valves with a bore scope) to know how much VSR had occurred really. You don't know if loss of compression symptoms will be apparent on the Daihatsu tomorrow...

My car runs a sequential system but takes 5 seconds to change to LPG regardless of temperature. Granted it is 1998 model with a low demand V6 engine, metal manifold etc, and I could have fitted a single point system (would also probably have fitted an OBD fix if I had taken that route, to make sure petrol fuel trims stayed around zero so it ran properly when switching back to petrol... not an issue with a sequential LPG system as when calibrated properly they will do that anyway). I preferred the sequential route but if I were converting it 10 years ago would have fitted a single point system, only maybe with the OBD fix. Less of a case for single point systems these days given the similar prices of sequential and mixer systems, 10 years ago the single point would have been a fair bit cheaper for a 4 cylinder conversion and a lot cheaper for a conversion on anything with more than 4 cylinders. Very likely most of this would be equally relevant to most of the cars on your shortlist... Could probably make most of those switch to gas in record time with a sequential system too.

There are 2 reasons why a sequential system starts on petrol with a cold engine. Apologies to Gilbert because I've just noted he's already mentioned much of my point 2 here but I've written it now so will post anyway!

1. The reducer may be too cold to properly vaporise the gas. Can't have liquid gas going in through the LPG injectors, that would mean the engine got wayyy too much gas for a way too rich mixture. Can't have LPG vaporising in the pipe between the reducer and injectors, that would mean the gas would be at way too high a pressure and the system wouldn't be able to cope with that pressure (ECU compensating for such high pressure means injectors would be pulsing for extremely low pulse duration and they can't work properly like that / gas pressure fluctuating widely in the pipe etc). Also, sequential system temp correction isn't always good at extremes of temperature, so even if the above points are not relevant the system can still be out of calibration at low temps.. Temp correction can often be adjusted/improved by the installer, problems with none vaporised LPG can also occur with single point systems.

2. Sequential systems work as a slave to the petrol system, but petrol doesn't atomise properly in a cold engine and unatomised petrol cannot be used/burned/have much of an influence on the mixture the engine requires .. So the petrol system pulses petrol injectors for longer with a cold engine, to apply what would be the 'choke' effect (in carb terms) to allow the engine to get enough vaporised petrol to regain the correct air/fuel ratio. Given the longer injector pulse times the slave LPG system receives under such conditions, it pulses LPG injectors for longer too, but LPG is already (hopefully) a vapour before it reaches LPG injectors so any longer LPG injector pulse means the engine actually gets a too rich mixture... This can be got around by fooling engine temp sensors (so the petrol system thinks it is starting a warm engine, so the choke effect isn't applied) but I didn't even need to do that on my car, LPG temp correction good works to the same effect, but wouldn't work as well on something more demanding.

Single point systems do have a place, some people prefer them, I too like the simplicity and can see advantages with the standalone nature - obviously being a separate standalone system it doesn't need to rely on petrol injection pulses, but you also get better guarantee of equal air/fuel mixture to each cylinder where with any multipoint injection setup it only takes some of the engine valve(s) to flow a bit more air than others or some injector(s) to flow a bit more fuel than others to make for a difference in mixture across cylinders... not much of a point though, and would be an almost equally relevant point for favouring petrol throttle body injection over petrol multi port injection but not many would favour TBI over MPI given the further advantages of MPI. There are vehicles, including some older vehicles, that a sequential system is going to be a better bet on, the reverse isn't often true but there are cases. Only a very slight case for better MPG with sequential over single point on older engines and even then probably mostly due to valve gear wear (related to airflow effecting cross cylinder mixture).

If you touch freezing metal with your hands they are likely to stick to it and cause you injury, touch freezing plastic which is nowhere near as good a heat conductor on the other hand (hehe) and you probably won't feel the cold. I reckon plastic body injectors are longer lived with temporary really cold gas situations (where the gas temp cools the injector body) but cold gas for long enough will still damage the seal at the bottom of injector plungers.

Simon

[marcos]

Simon, thanks for giving such a detailed reply.

I appreciate your point valve wear being difficult to assess without a stripdown however I have done compression checks and also keep an eye on the valve clearances. This along with a reliable 32mpg on gas leads me to believe the valve gear is made of pretty decent stuff. Great idea about using a camera to get a visual on the valves - i've got a usb endoscope thingy; i'll take a image on Wednesday and post it.

Interesting points about the reasons sequential systems need to start on petrol. Fooling the petrol ECU to think the engine is already warm sounds straightforward enough and it should also be fairly simple to add an electrical heating system to get some heat into the vapouriser instantly.

That just leaves the issues of whether the life of the LPG injectors would be shortened by cold starting on LPG.

Is there any data available on this?



Marcos

[scottyf]

Sorry to go off track here a little bit.

Mine switches using a sequential system - Multipoint as some of you will know.
I always feel that as I switch to lpg almost instantly most mornings. That as you say it will try to run a richer mixture but lpg doesn't really need to do that.

So Can I adjust the temp settings multiplyer to lean out the mixture even when cold starting.
At the moment I get no errors etc but I am wondering about running a little leaner and it being okay and saving some gas. Or will the car's ECU just try and change the pulses if the temp corrections wont help?

I imagine lpg I can run at normal pulses on a cold start etc.

[LPGC]

Marcus, I've seen all types of vehicle that should have had valve lubes fitted but didn't, that have done 100k miles on LPG without apparent damage, but have also seen plenty of the same that have done 20k miles on LPG and have compression problems. How the vehicle is driven can make a difference... Exhaust gas temp not as hot at part throttle as at full throttle, exhaust gas of course has to come past exhaust valves, materials including valve metal gets softer with heat.

Plenty info from installers like myself on extreme cold damaging injectors, it does happen, not so much general cold conditions but extremes of cold causes by the refrigeration effect of liquid gas making the phase transition to vapour (in an unheated reducer the effect is akin to putting your aircon on full in the car in the winter), also plenty on cold damaging both sequential and single point reducers. Rubber-like parts that flex in operation can be damaged by cold wherever fitted, so including reducer diaphragms and injector plunger seals.

Those injectors I mentioned that seem to stand up to cold particularly well and are also otherwise generally very reliable are £35 for a rail of 4. Put them on my car and it has switched to gas after running for 5 seconds for a few years and 40000 miles now.. I know I could probably break the reducer and/or injectors if I drove it hard repeatedly especially on a freezing morning though... And I dare say I could find issue with your mixer system if I did the same with that too - Not saying I could break mine or yours for sure, or without doing it regularly, but I bet I could get either to at least run poorly on a cold morning if I went out of my way to try! I suppose for me breaking such would just mean I'd dig some other reducer / injectors out of boxes full of them in the garage, and a slight inconvenience.

Scotty, I'm not suggesting good results can be had in all cases... I started writing some of the technical points that will affect it but have realised there are too many to list and I'd be up all night completing that sort of post! Very vehicle specific and in this sense vehicle means the vehicle with it's particular LPG system fitted in that particular way.

So for now I'll just say - Best bet to try on your car might be to fool the petrol ECU into believing the engine is a bit warmer than it actually is (in a cold start situation). Ideally you still might want the slightly higher idle speed that you get with a cold engine (engine friction will still be higher anyway) but you want to get rid of the bulk of petrol cold start enrichment... Then play with temp correction. But remember that it's summer now... On a cold winter day even with the system changing at 40c reducer temp, gas temp will probably be reading lower even after a minutes driving on LPG than it reads when you first look at the screen in a morning now - you might not want any adjustments you make now to be applied under such conditions, because in winter with reducer temp at 40c the engine will be well on it's way to being warmed up and won't be adding enrichment, if temp correction has worked accurately under such conditions in the past then obviously changing it would mess that up. Mostly been referring to gas temp correction because most systems only have gas temp correction (and without checking I can't remember what ECU you fitted). If you have reducer temp correction, that might be more useful than gas temp correction for this purpose..

Simon

[scottyf]

LPGTECH 221 is the ECU.

Think I had adaption make the adjustments from collecting maps. Then I just monkeyed about with it with the lambda readings. This was all done and full operating temperatures mind.

Then I just had it switch over at a lower reducer temperature because I was getting sick of putting a tenner of petrol every 1000 miles. Now I only put a tenner in every 3500 miles. Increasing the savings quite considerably.

It switches over at 15 degrees. But I know the petrol pulses are still effectively on choke. Which means its dumping gas in while warming up properly. So if at cold I dump my throttle it does run far too rich I believe.

Might eek out another few mpg if it didn't have to do that.
Shame I can't fool the temp gauge as you say on the thermostat to all ways ready a little higher.

[scottyf]

Saying that I could just place a resistor inline with the signal read out on the temp sensor couldn't i?
Say get it to read 20 degree's higher.

That way it would fuel the car on the leaner side on the petrol, and leaner on the gas during the warm up phase.
Problem being wouldn't it then read too high once it reached operating temp.
Not sure this would effect the fueling.

Ie if 20 degrees higher than what ever its reading then at the normal operation it would say 110, which might send the car into electronic panic mode or run far too lean.
Guess its a bit of trial and error.

What have you done previously?