V40 T4 LPG high rpm running problem
 

Greetings from Bulgaria!

I bought 3months ago Volvo V40 T4 200HP year: 1998. Really nice car! The problem came when I installed LPG system, because as you may know that alternative fuel is about 2times cheaper than the regular A98 gasoline.
When the car is running on LPG fuel, after 3500-3800rpm the power of the engine suddenly falls. If you are still holding the gas pedal after a secon ot two the engine comes alive and again nearby 4500 falls dead. And again the same situation in the high rpm region. It's the same on 1st, 2nd, 3rd and 4th gear, 5th didn't tryed- it's not important. My LPG system is from Italian manufacturer- Landi Renzo.
Did anyone had that problem and solved it? Thanx in advance for all given opinions.

When the car is running on gasoline A98 there is no such problems.I tryed to run it w or w/o DSC system- no difference. In the range b/n 800-3400rpm I don't experience any problems when I run it on LPG. We tryed changing the system software and putting larger evaporator, but no change.


PS: If this thread is in the wrong section, sorry for putting it here.

You are in the right section with this question.

I presume we are talking about a Landi injection system here.

The LPG injectors which ones do you have MED, Keihin or somthing else? Is the software set to correct injectors?

Is the gas pressure stable and not dropping? Is the reducer temperature high enough at 60c - or gas temperature 40c

Are the injector nozzles mounted directly by the petrol injectors or mounted away from them.

Has the vacuum/boost pressure pipe been conected to the nipple on the reducer?

Are you loosing RPM signal when this problem happens? Is the rpm (brown wire) soldered to the signal wire of a coil?

What spark plugs are you running? Idealy you want copper core with a std gap.

There a few things to check there. Please report back

Is the gas pressure stable and not dropping? Is the reducer temperature high enough at 60c - or gas temperature 40c

As for that question I can report that the outside temp was about 2-3 degreece centigrade. The reducer temp was about 55-60deg. c., but the gas temp after a serious boosting felt down to 5-6deg. c. Normally is about 16-18d.c. The gas temp is measured by a sensor that's just before the gas rail where the gas injectors are.
We replaced the evaporator with larger one, but the temperature didn't raise.

The LPG injectors which ones do you have MED, Keihin or somthing else? Is the software set to correct injectors?

All from above is supposed to be OK.

Are the injector nozzles mounted directly by the petrol injectors or mounted away from them.

They are directly mounted and are close enough to get max efficiency.

Has the vacuum/boost pressure pipe been conected to the nipple on the reducer?
Suppose so, that I didn't check.

Are you loosing RPM signal when this problem happens? Is the rpm (brown wire) soldered to the signal wire of a coil?
No RPM are lost, the rpm needle stays constant and after a while continues to move slowly to higher rpms

What spark plugs are you running? Idealy you want copper core with a std gap.
I was with NJK plugs PFR6B. On the surface of the ceramic body of 2 of the spark plugs there were 2-3mm lines- there was some sort of damage. That's why I replaced them after 2000km with Denso Iridium IK20 0.4mm. - There was no change.


That is what I can tell for shure. I found a thread at the global volvo forum, where someone said that when running on LPG the spark plugs should be changed every 5000miles, because the engine burns them?!? Strange..

PS: I think that the engine was remapped and the boost pressure is above the announced - 0.8bar Unfortunately no time to go for diagnostics and check how the turbo pressior changes at diff rpms.

Thank you for the fast reply!

You can see the boost pressure on the software. It is the map reading on the software.

Can you take a photos showing the position of the injector nozzles?

The temperature is rather low and could part of teh cause of the problem. Have the water copnnections been T'd into both heater hoses or has it been plumbed in series. Plumbing the water in series is no a good idea.

When you say the power falls do you mean that the engine increases rpm very slowly from that point. If does does the engine shudder at all while this is happening? Does the oxygen sensor read rich or lean while it is running badly?

V40 Lpg
 

The observed pressior in the evaporator was between 2-2.4bar when full boosting. As for the power drop- sorry my mistake. The rpms freeze when 4000rpm is reached. After a second or two it continues to accelerate, but it clearly misfires after that and then do it again when 4500rpm, 5000, 5500rpm reached. At that point the engine behaves like it is in the critical rpms when the engine cuts its work above 7000rpm.

The oxygen sensor says that the oxygen/gas mixture is fine, that is regarding the manufacturer (Landi) software. We tryed different revs of the software but still the same in the region above 3500rpms..

The gas temperature is pretty low- 6c is measured when the evaporator is heated to 60c, and the coolant system is at 90c. Do you have any Idea why that happens and what is the normal gas temperature that should go into the gas nozzles?

I made some photos, unfortunatelly w/o removing the engine cover. I hope you get general idea for the situation here.

Greetings!

The low temperature is most likely where the problem is.

Do you have a temperature sensor fitted on the vapouriser or is it just connected to the cars engine temp sensor?

The the vapouriser getting so hot that it is uncofortable to touch? It sould be getting that hot, if not there is a water flow problem.

If the vapouriser is getting very hot but the gas is not heating then that is strange. Has a landi vapouriser been used? They are supposed to be good for higher power outputs but I have little personal experiance with that unit. Perhaps change to a differnt make??

Next question what is the highest petrol injection time you are seeing? and at what RPM?

respond
 

The temp sensor is in the evaporator and measures its temp which is far lower than the coolant temp sensor. Some say that the pressure comming from the turbo is above 1.2bars, which is really a problem for the installed Omegas system. The original turbo pressure is about 0.8-0.9bars. Do you have experience with chipped one? What pressure is reached when remapped?

The gas filter after the evaporator is FJ101G. That model is stated to be installed on non-turbo engines and has following properties:
Particle filter size: 80micro mimimeters
Max pressure: 2bars

The other one Landi Renzo say that should be used on turbo cars Part Number 180/80010.
Particle filter size: 10micro mimimeters
Max pressure: 3.5bars absolute pressure (actual 2.5bars)

After some days of discussion many people in Bulgaria couldn't solve the problem which appears to be serious :))

Thanx for your responses!

I think they are looking at the worng kind of things and being blind to the temperature problem.

The level of boost you are running should not be a problem with regards the electronics. I've converted cars with higher boost levels with AEB electronics but in a slightly differnt platform

I would have thought the landi vapouriser and MED injectors should also be ok with that boost pressure.

The vapouriser sitting at around 60c would not worry much but a gas temurature of under 20c would worry me.

Some of the problem might be the gas pressure unless you are being given the wrong readings - it is also odd two vapourisers have suffered the same problem. The gas pressure should be set to between 1.2 and 1.8 bar. When under load the pressure will usualy drop about .2 - .3 bar.
The manifold balance pipe must be connected to the vapouriser and T's with the MAP sensor. The tapping for this connection also need to be put into the manifold just behind the throttle body and not T'd into any other vaccum line.

lpg
 

Sorry for not responding the last couple of days but it was holidays round here. Last Friday we did some additional test under milder circumstances. The outer temp was 10c. The evaporator's temp 80c and the gas temp about 30c. The problem appeared again. So we can exclude the temperature in our equation. We did the nozzle timing thing under gas and gasoline fuels. When running on gas and reaches 3800rpm the singnal from the lambda says that the air/gas mixture is not enough enreached. So may be the problem is in the evaporator's pressure. On Tuesday ot Wednesday we'll try to increase it and see wether there will be any change the the "critical" sector after 3800rpms. However, the guys from Landi Renzo World said only that there are cars which are suitable to convert and other ones that are not?!? WTF?? No proper explanation was given. Honestly I don't beleive that no one has EVER installed a landi renzo system on his T4 engine without having any problems.

Adjusting the gas pressure will make very little differnce.

The mapping needs to be altered to enrich the fuel mixture at higher RPM.

Does the Landi system have an OBD connection available yet or are they behind with development on that?

Just increasing the gas pressure will not make much differnce as the ecu compensates the gas injection times on gas pressure.

The only reason for possibly increasing gas pressure would be if you were seeing a big pressure drop or switching back to petrol due to lack of fuel supply.

Are the installers experianced in the Landi system?