Subaru Impreza WRX Turbo Conversion and Issues

Message

grybaz · #1 Post by **grybaz** » Thu Jul 05, 2007 3:17 pm

Right, here's me; new forum joiner, with my LPG Converted Subaru Impreza WRX Turbo. The system I've got installed is Romano N, all looks good and performance wise I like LPG much more than petrol, but got several issues; When I've got LPG installed there were several CARB configuration issues which I have rectified by purchasing cable and adjusting system to the point where I think it works best. Leaving computerized configuration aside I've got one problem that really annoys me; when I accelerate hard and get engine to certain REVs (that depends on which gear I'm in) but mostly happens on higher loads - I just loose pressure at Vaporizer then system switches to Petrol for several second and gets back to LPG when accelerator released a bit. I managed to visit installer not the one who’s done work originally – and been suggested that pipe coming from tank might be to thin. Has anyone of you had problems with loosing pressure? I wonder how doe’s V8 engines get sufficient gas from tank?

woody · #2 Post by **woody** » Thu Jul 05, 2007 9:03 pm

Dont confuse a V8 with your 4 cylinder engine. You need to work out how much horsepower per cylinder.ie a 400 hp v8 is easier to run than a 300hp 4 cylinder. However , many things come in to play with performance engines,and the first is gas supply to the vaporiser.secondly the vaporiser needs to be physically able to vaporise the liquid which is delivered,the injectors need to be of the correct flow rate ,and the mapping needs to be accurate , not guess work. If all of the above are correct , your car should drive the same as it does on petrol. You should have a 8mm feed to the vaporiser,if you do,then it is almost certainly a mapping problem. Cheers Keith <a href="http://www.gastech.org.uk" target=_top>www.gastech.org.uk</a>

go_lpg · #3 Post by **go_lpg** » Thu Jul 05, 2007 10:28 pm

Eimantas, How many vaporisers? How many (if any) filter/bowl units on the front end, and of what size? Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

grybaz · #4 Post by **grybaz** » Fri Jul 06, 2007 2:17 pm

Keith, I'm not confused about V8 and 4 cylinder engines, it's just logical that V8 will require more GAS to be vaporised, my WRX is only 225BHP and honestly it performs better on LPG than PETROL. Since I've read you post I'm not sure that are you quote as mapping <IMG SRC="http://www.my90.co.uk/lpgforum/clipart/happy.gif" ALT=":-)" BORDER=0> is it the bit where you adjust 8 separate INJECTOR SETTINGS on you laptop using RISN software ? Ross, I don't think thats the case of not getting enough GAS, because Cut-off happens with full tank as well. When you say 8mm pipe is that inner diameter or outer that you're quoting ? And finally Steve, I've only got one vaporizer and not very sure what are these filter/bowl units ? Thank you all in advance for trying to help me, as I do about 1200 miles a week in my Scooby and haven't got much time left to visit an expert.

go_lpg · #5 Post by **go_lpg** » Fri Jul 06, 2007 6:30 pm

Gas filter and bowl units normally have a solenoid fitted on the top, having two electical connections, and copper pipe going to and from the body of the unit. You should have at least one. In any event, and before we get deeper into this, are you certain that your system loses gas pressure at precisely the time it cuts back to petrol? I ask because the switch back may be due to something different, i.e. the injector pulse width reaching the maximum (factory default preset) setting of 24Ms. If that max. injector pulse width is reached the system will switch back to petrol whatever the gas pressure reading is. Better to check this first before spending time going along potentially the wrong path. Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

woody · #6 Post by **woody** » Fri Jul 06, 2007 10:17 pm

Unfortunately your logic does,nt apply.The reason it performs better on gas is because it is almost certainly running on petrol after changing back , due to variouse reasons ie, pressure drop,injectors maxing out,wrong delivery pipe size,incorrectly plumbed vaporiser,wrong map reference,etc etc. If you adjust the 8 map boxes you may get it to run somewhere near right,if all of the above are right. Finally, if you had visited an expert in the first place , you would not be seeking the advise of the forum posters. cheers Keith. <a href="http://www.gastech.org.uk" target=_top>www.gastech.org.uk</a>

go_lpg · #7 Post by **go_lpg** » Sat Jul 07, 2007 9:15 am

OK Keith and Ross, let's see if Mr Eimantas comes back with a Y/N on the gas pressure. This could be a useful exchange of info for all 4 of us. Eimantas - When running your new check on gas pressure, it would also be wise to watch the red/blue ball or Gas/Petrol indicator depending which page you are using. The switch can 'lie' if the software is set up in a certain way, telling you that the engine is running on Gas when it is actually running on petrol. There is a lot to watch for if the test is to produce meaningful results so you'd be better getting someone else to drive, holes in the scenery may result! Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

grybaz · #8 Post by **grybaz** » Mon Jul 09, 2007 11:47 am

Good morning to all, Right, reading all your posts everything gets more and more complicated, but thanks for that and lets continue; 1st thing, Keiths comments; I think I've got 6 out of 8 boxes mapped just fine as Scooby goes like stink <IMG SRC="http://www.my90.co.uk/lpgforum/clipart/happy.gif" ALT=":-)" BORDER=0> I've got some glitches on LOW revs, but that is due to be rectified soon as... When you say it's almost certainly running on Petrol after changing back; I say it's definitely NOT, when accelerated hard on high revs it's goes back to petrol for few seconds only (you can definitely feel that, don't need to look at switch), then goes back to LPG when accelerator released a bit; and I'm only talking about performance before switch to Petrol, because it's definitely better, I'm looking to find a rolling road for 4 wheel drive in close to London so I can confirm with proper testing. Visiting expert, well first of all the expert was recommended by Autogas Worldwide, a company in High Wycombe, he haven't left much of impression but he certainly did rectified few problems. He also advised me to but vaporizer with adjustable gas pressure; when I called Autogas Worldwide to order one they just laughed and said that person must have fitted his last LPG kit a long time ago. Also being a DIY person I rather consult with people on forums this way I will know my car better, also this stuff is very interesting to me <IMG SRC="http://www.my90.co.uk/lpgforum/clipart/happy.gif" ALT=":-)" BORDER=0> I can also CONFIRM that there's only one BOWL... As for other comments/request I will get back with more detail this afternoon; I will be using my precious lunchtime to investigate <IMG SRC="http://www.my90.co.uk/lpgforum/clipart/happy.gif" ALT=":-)" BORDER=0>

grybaz · #9 Post by **grybaz** » Mon Jul 09, 2007 2:22 pm

Lunchtime is over and I've came back with some results: 1st problem identified is; PIPE it's actually 6mm, I always thought it's 8mm. It's wrapped in black heat shrink plastic and looks FATTER than it is. So first task is to replace a GAS supply pipe. 2nd would only be MHO: SPARKPLUGS... whatever changes I make in mapping table the engine IDLES unevenly. As I said before plugs are original subaru parts and wasn't changed or GAP narrowed when installing LPG. I'm attaching document with screenshot, if someone would look at it maybe there are some obvious problems to be adjusted. Thanks<center><table border=1><tr><td><img src="http://www.my90.co.uk/lpgforum/icons/at ... t_icon.gif" align=left alt="application/octet-stream">RISN Screenshot <a href="http://www.my90.co.uk/lpgforum/messages ... G-4590.unk" target="_blank">LPG.doc</a> (120.3 k)</td></tr></table></center>

go_lpg · #10 Post by **go_lpg** » Mon Jul 09, 2007 11:39 pm

Forget the switch display, see post of July 7th, 2nd para. It may well be meaningless. Result of gas pressure test as described in July 6th post, 2nd para. is crucial before moving on. The only correct approach is systematic, methodical. Anything else is guesswork which brings success only sometimes... Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

grybaz · #11 Post by **grybaz** » Tue Jul 10, 2007 4:31 pm

I've got an idea, just wonder if thats worth trying, I can install screencapture software on my pc and do a test drive, therefore that will enable you to see whats is actually going on, it will be movie type file. Will get back with some results ASAP

go_lpg · #12 Post by **go_lpg** » Tue Jul 10, 2007 5:31 pm

OK, although I only have dial-up ( I cannot get anything else here). For now, some food for thought - Today I finished development of a new conversion (new to us that is), Jaguar V12 6.0 litre, 340 bhp using Romano SGi. It runs just fine all the way up to 110 mph with 6mm back to front pipe, no cutting back to petrol, no pressure drop or similar problems. In the past I have converted BMW V12, BMW M5, Audi S8 V8 4.2 340 bhp, Bentley Turbo R, Jaguar XJR 370 bhp, Range Rover Sport 4.6 Supercharged etc. etc. all with 6mm back to front pipe fed from a single hole tank. IMHO, and with this evidence to back it up, the 8mm pipe requirement for performance cars is myth, pure and simple. If the above cars run perfectly on 6mm pipe it is reasonable to assume that yours would too. Also today I looked at a car converted elsewhere using Romano. It had various issues but the one that may be of use to you was this; At idle, the switch displayed 'gas' as did the laptop (blue ball). How was it that I was able to disconnect all 4 gas injectors with the engine not only continuing to run, but not even miss a beat? Easy when you know the system...The software had been set to run the engine on petrol at minimum RPM and it was doing just that, although the switch and laptop told us otherwise. As I have said, under some conditions these can lie. What triggers the fuel-in-use display on the switch and laptop is the gateway RPM, along with the other criteria, NOT what fuel the engine is actually running on! Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

claicerrig · #13 Post by **claicerrig** » Sat Jul 14, 2007 10:51 pm

The symptoms use describe are virtually identical to the problems i encountered with my Nissan 200sx Turbo. 1)At 3100 rpm change to petrol so fitted an 8mm feed pipe 2)Car would then change over to petrol @ 5400 rpm this was traced to the standard Nissan Injectors giving 100% duty cycle max open no signal to fire Lpg injectors. Overcome this by fitting 555cc inj and a "stage 2 "chip with a custom map on petrol . Car was then set up by CSW to run LPG and the car has not lost a beat in 2yrs. One problem that does rear its head occasionally is when driving in a spirited manner through twisty bits with a low LPG level i have suffered from fuel cut caused by the fuel moving around (The lack of Baffle effect) Hope it goes ok fir you Dave

go_lpg · #14 Post by **go_lpg** » Sun Jul 15, 2007 10:29 am

Fuel 'slosh' is a definate factor when considering LPG tanks that have no baffles (and no traditional LPG tank does to my knowledge). Certainly this effect can cause a short reduction / cut in liquid supply. Ross K. described this effect very well earlier on. In addition, 6mm pipe cannot flow as much liquid in the same time period as an 8mm pipe, that is also fact. Both effects can be cancelled out by the fitting of a larger LPG filter / bowl unit near the vaporiser(s). On performance conversions (say my V12) I fit two of these. The effect is the same as having a small LPG tank under the bonnet, i.e. no break in supply due to tank 'slosh' and no waiting for fuel to come along a pipe from the tank. This approach is much easier than going to all that trouble with 8mm pipe, only to find that the limiting factor (certianly in the case of single hole tanks) is the hole on the multivalve or pipe fittings. Truth is that the fitting of 8mm does not improve supply at all when the smallest hole in a fitting at the tank or vaporiser end is considered. What it does do is establish a larger fuel reserve along the pipe's length, along the car. That is more easily provided by the use of a larger filter/bowl unit.... Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

richy_boy · #15 Post by **richy_boy** » Mon Jul 16, 2007 2:55 pm

Very interesting topic here chaps.. Good to see a scooby running on LPG as this was one of my next potential purchases (amongst a million others). I'm surprised the 'chocolate piston' hasn't had an issue with the higher potential EGTs of LPG though, so it's good to see some evidence backing it as a valid project. I *think* I have 6mm piping on my car, which quite happily copes with 295bhp 310ftlb from a 2L turbo'd engine. That's running on BRC vaporiser and one 'HF' filter. Rich

go_lpg · #16 Post by **go_lpg** » Mon Jul 16, 2007 9:47 pm

Maybe Chocolate Pistons would match Ford's Lard valves very well?

woody · #17 Post by **woody** » Mon Jul 16, 2007 9:52 pm

Hi Rich , i would be very supprised if your car is on 6mm pipe, all Genius Max kits are supplied with 8mm as standard,check the colour of the pre vaporisr solenoid,if it is red,you should have 8mm pipe. cheers Keith <a href="http://www.gastech.org" target=_top>www.gastech.org</a>

go_lpg · #18 Post by **go_lpg** » Tue Jul 17, 2007 10:20 am

Very feasible Ross, all of the above, and you are probably right. To eliminate loss of pressure (I also doubt this is happening) I have asked a logical question to which there has been no reply to date. When we get that reply, we can either learn something new or simply move on. A while back I did similar calculations on injection times, arriving at similar results to yours. I got rubbished at the time although that was due to an owner who knew better. I'll see if I can dig this work out. In any event, certainly we must not forget this fact - Most LPG injection systems run from the existing petrol injection times and re-interpret (increase) them for LPG. If an engine has injection times of (say) 20Ms at highish revs on petrol and they are 'maxed out' (reaching the point where they would be open 100% of the time) then that point has to be reached much earlier when on LPG. With LPG having only 85% of the calorific value of petrol and then being injected as VAPOUR instead of liquid, (Petrol) the point of 'maxing out' has to be a lot lower than when on petrol, it could not be any other way. Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

go_lpg · #19 Post by **go_lpg** » Tue Jul 17, 2007 10:28 am

Ah, and BTW, if Romano 'sees' low gas pressure whilst running on gas it will automatically switch back to petrol and sound an alarm. This is the very same function as the 'tank empty' facility. To cancel the alarm the driver must hit the button although this simply maintains petrol operation. Not until the button is pressed once more will it try to go back to gas, and only then after doing its prescribed diagnostic self -check, temperature, pressure and RPM protocols. In short, I doubt that low pressure is the culprit here. Regards Steve <a href="http://www.go-lpg.co.uk" target=_top>www.go-lpg.co.uk</a>

woody · #20 Post by **woody** » Tue Jul 17, 2007 10:36 pm

As far as i can see here , low pressure will only occur when, the vaporiser cant deliver enough vapour,due to lack of liquid to vaporise or the vaporiser is not up to the job. We have just installed a dedicated 10 cylinder kit [single ecu single vaporiser] to a 6.8 V10 motorhome , approx weight 7 tonne,under max accel up hill at 5500rpm the pressure drop was from 2200mb to 2190 mb and fuel trims within +/-2% to petrol,but with only approx 350bhp ,or 35bhp per cylinder it aint really working hard. cheers Keith <a href="http://www.gastech.rg.uk" target=_top>www.gastech.rg.uk</a>