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Pipe length on V engine

Posted: Wed Nov 05, 2008 1:07 am
by twinturbo
Hello, could anyone give me a little advice on my Supra, running a prins system.

The car runs a little lean on the left bank, only on lpg, I know this as the code it is throwing.

I would like to ask this question to a prins expert, who has this on a V engine.

The pipes from the vapouriser/filter, that feed the injector rails are not the same length, the right bank has a very short 16mm gas pipe to the rails, the left bank, the pipe is very long. I am not talking about the injector pipes here, but the main pipes that feed the rails, as this is a V6 it has 2.

What I am saying is, should they be the same length? or about the same, if so what in MM does this have to be on a V engine.

Someone has also told me that there is some expert setting on the prins VSI, that not even most of the installers understand or use, and some of these setting can be used to adjust the banks, Bank 1 and Bank 2 on an individual basis, as they are usually just adjusted as one.

Can anyone comment on this please.


Re: Pipe length on V engine

Posted: Wed Nov 05, 2008 12:23 pm
by mak-uk
Hi Kev,

On my V8, the placement of the vapouriser/filter and the design of the engine allows the gas feed pipes to each bank to be very similar in length. Please refer to the pictures here:

I do not know if there is a maximum recommended length but as the length of the gas pipes to the nozzles from the injectors can affect performance, I would imagine it would be the same in this case (if there is a significant difference). What is stopping them being the same or similar lengths on your engine? Perhaps the vapouriser/reducer need to be moved? Post some pictures of the installation?

The only advanced software settings that I know of on the Prins VSi system (bearing in my mind i'm not an installer) are for running in open-loop mode. However, really you wouldn't want to mess with these as the way the install is fitted to the vehicle should mean that little or not advanced adjustment is required (ideally).

The best thing to do would be to speak to an Installer/supplier (Alternatech in the UK) or wherever you sourced the kit from.

Lets us know how you get on.

Re: Pipe length on V engine

Posted: Wed Nov 05, 2008 4:08 pm
by twinturbo
Thank you,

the kit was fitted to the car so I don't have much info.

The vapouriser is fitted to the O/S inner wing, and that is the only place it can really go, as its so tight.

The bank on that side has a really short pipe running to the injector rail, the left bank it runs right round the back, its much longer. (left is the lean bank)

I was wondering what the tolerances are, like say they have to be no more that xxMM difference.

Maybe someone might know?



Re: Pipe length on V engine

Posted: Tue Nov 11, 2008 12:29 pm
by SebastianS
Kev, my first question - is it prins v.1 or v.2?

Prins v.1 has great bug in its construction, due to fact, that injecting time is taken only from one gasoline injector, and this is the base to calculate opening time for ALL lpg injectors. That's why prins v.1 will never work properly, when two banks of engine work independently (have their own lambda circuit). If even that bank, which runs too lean will be riched by gasoline ECU (through longer gasoline inj. opening time) - it will not take any effect for prins, due to fact that lpg injector opening time is calculated from gasoline injector from another bank.

Length of lpg pipes from vapouriser to lpg rails has no influence on running rich or lean, but if lenghts of two pipes varies dramatically, it's good idea to join backs of lpg rails together with additional pipe to compensate some differencies of lpg pressure.

Good luck.
(next time go to Poland, to my garage, to get proper LPG system properly installed) ;)

Re: Pipe length on V engine

Posted: Tue Dec 02, 2008 2:22 pm
by twinturbo
so how does Prins V2 work on independent banks?

Do you know all the settings on this system, and you can be sure there is no adjustment per bank? you are saying that the system is not that good?

Tell me more please,