LPG and Turbo

[cribbj]

Peak & Hold driver, these are used to correctly drive low impedance injectors.

Some ECU manufacturers advise that their boxes can drive low impedance injectors with the addition of a resistor in series with each injector.

This scheme simply limits the amount of current the ECU has to output, and the injector doesn't open as fast as it should with a true P&H driver. Sometimes it's not a problem, but it can be noticeable if you're running some really big (like 1600cc) low impedance injectors and you can't get them to idle properly.

Actually this is the way Toyota, Honda and other OEM's drive their low impedance injectors, so I suppose it works, after a fashion, but the injectors certainly don't open as fast as the injector manufacturer intended them to.

AEM's ECU is like this, so to their credit they came out with a separate P&H driver box if people want to drive low impedance injectors correctly. Here's a link to this box: http://www.aempower.com/ViewCategory.aspx?CategoryID=83

BTW, the Prins ECU is already setup with the correct P&H drivers, and costs less than a standalone plus a P&H driver box.

And although the above might sound like a sales pitch, no I am not a Prins salesman....

 

[Deuce]

John, thanks for the explanation. I have trouble working out some of the abbreviations used sometimes.

 

[cribbj]

No problem; hotrodding is really getting to be a confusion of alphabet soup these days.....

 

[urtwhistle]

cheers cribbj, so realy it seems you realy do want the prins ecu then, just to simplifi the job ie all the P&H and all the triggoring of all the relays and valves are handled by 1 specific peice of hardware rather then a mongrelised setup that would be hard to trace problems with.

i know this has nothing to do with toyota's butttttttt since there is a majority of ppl who can actualy give me a correct answer, i'll run this by u.

i am quite possibly buying a r34 GTT skyline thats been modded quite a bit with a power FC ecu. sooo if i was to convert this car to lpg with the prins ecu and all, id be able to control and change the AF ratio with the Power fc. right????
cos from what i understand the prins would be piggy backing the power FC. soo if i change the amount of fuel in the power FC it will change the fuel getting dumped in by the prins???.

or have i completely missed the point. can i use the prins to add more fuel with out any piggybacks at all? and forget the power fc all together?


sorry bout all this i just gotta get it all worked out in my head b4 i go and waste all my hard earned lol

chris

 

[cribbj]

To date, the majority of LPG installations are still dual fuel, and that's the prime reason an OEM ECU is kept with the Prins setup. That, and that little problem called OBD, which I think in Europe is called something else. No user tuneable, standalone ECU can reproduce the OBD signal, so the OEM ECU has to be kept for compliance.

Of course if compliance isn't required, ie for offroad or racing use only, and you're already running a standalone ECU for petrol, and you want to convert over to a dedicated, single fuel LPG system, you can ditch the liquid fuel system, injectors and ECU, and the Prins system should work fine as a standalone fuel management ECU, however it does not have ignition capability!

But just be sure you have enough LPG pressure in your tank, for the maximum boost you want to run, on the coldest day you'll encounter. My mate Pete already went through this in Oz and found he didn't have enough LPG pressure for his boosted application. Matter of fact, when it was the dead of winter at his location, he didn't even have enough LPG pressure to run the Prins system on his motor, without the turbocharger. In short, ask your local LPG supplier what the vapour pressure is of his LPG for the coldest day you want to use it. If it's not at least 2.5-3 barg, I'd forget about trying to run a boosted car with the Prins, or any other SFI LPG system.

 

[urtwhistle]

all good points CribbJ.
ok soo in the likely event i dont have enough gas pressure, and is forced to go a dedicated carbed lpg setup. what type of ecu would u use to take full use of it. since its a carbed motor now, the ecu doesnt need to worry about the fuel management, would u just use a piggy back to control the air flow or would u still go full stand alone.

1 thing that i dont like about carbed motors is the limited tunability with them, unless u constantly drive at WOT.

i know this is getting beyond me but i was wondering if u went duel carb's but had a gas valve on 1, so that if u wanted a street tune only gas was flowing through 1 and air through both or a race tune, gas and air would be going through both.

i dont know if this is possible, bit with my limited knoledge it just seems with out having 2 carbs u would be limited to what u were capable of doing were twins u get twice the amoutn of jets to tinker with.

 

[cribbj]

If you find you need to go naturally aspirated, and carbureted, have a look at technocarb. They make pretty good kit.

Then of course, there's always the old standard, Impco

Here's a good LPG fuels forum too: Propane Forum - Alternative Fuels The Canadian/American membership on this forum are more familiar with carbureted LPG applications.

 

[Deuce]

Talk to Gasresearch in Melbourne. On my planned supercharged setup they have suggested using dual gas carbys, one large and one small, connected via a progressive linkage. The small carby operates at low speed (flow) and then the large carby cuts in as the speed (flow) increases, until they are both wide open at full throttle.

 

[edz]

Gas research

Some great info in all these articles, thanks Cribbj for all the helpful info, you've saved me a lot of money as I was thinking of the prins setup, but there is no way the prins setup will work in Canberra (-12 deg c in winter)

BTW - GasResearch - http://www.gasresearch.com.au/, if you read their forced induction page, they only recommend draw through turbo systems with their throttle bodies, quoting limited successwith blow through. Would be be very interesting with a backfire and lpg in the intercooler and plumbing - not!

You can see the way they setup the dual throttles to be staged in the pics.

 

[lexluther]

GasResearch

Actually guys, if you call up and speak to GasResearch (who are in Brisbane, NOT Melbourne) they will tell you that depending on your application, BlowThru may well be the better way to go. There are however potential pitfalls with running what is essentially a pressurised lpg system in what is designed to be a negative pressure system. And really is not something that should be attempted by someone who just wants to have a go, and does not fully understand how the system works. This is why the Draw through method is mentioned as preferrable because from the carby point of view, that is what is is designed to do: have air/gas drawn through it.

If you speak to them, they will (quite rightly) usually recommend you talk to a professional installer and performance tuner before attempting a forced induction LPG application. Seems to be more responsible than other manufacturers who will sell you the stuff and let you stuff it up yourself. :saevil:

 

[Deuce]

When I last visited them they were at Dandenong in Melbourne, but looking at their web site it appears they have moved to Qld.

 

[Pro]

i was thinking for an LPG setup it might be easier to leave the TB where it is and fit the mixer before the turbo.

that way, the mixer relies on suction, and the turbo doesn;t need a carbon front seal.

only downside is, you can't run a BOV (or intercooler) or you'll be venting LPG all over a nice, hot engine bay.

prob an okay setup for a mild, automatic daily or something - but it would work.

 

[urtwhistle]

Hi, been a long time since i have posted on here. Well i finaly got off my ass and organised my gas injection set up for my r34 gtt skyline. i ended up going a Prins duel fuel setup controlled by a apexi power fc programable ecu. i will post up some dyno sheets once i get it installed and running with all the bugs ironed out.

im already trying to figure a way of firing the lpg and petrol injectors at the same time.



chris

 

[cribbj]

Great - where are the pics? Let's hear all the gory details too!

What are you doing for an LPG tank?

 

[lexluther]

How will you boost reference the system? How much boost will you be running?

 

[urtwhistle]

hey guys, no pics of the prins setup atm, just waiting to get some time for the install. im using a round tank in my spare tire well. only like 40-50L i beleive. The car is currently tuned for 14psi with a stock turbo and it runs fine on 98 octane fuel, so i'm presuming that it should be fine on gas just a little rich. it will be running the largest keihein injectors which i think are 93cc but dont quote me on those figures.
the setup is costing roughly $4000 Au dollars, but luckily for us Aussy's our government rebates gas conversion's and my state further rebates it soo i will get some were around 3000 back from the government.

i was originally going for a Profire setup. it is a extremely good ecu, but at this point isnt able to be ran duel fuel legaly. not that running a power fc is legal either. Also Brad at profire is extremely helpfull he has alot of knoledge on boosted gas setups as he has several him self.

 

[urtwhistle]

hello ppls of the world. finaly got a camera that would work. so here are some pics of the Prins setup on my GTT skyline. the car runs great for untuned car. it costs me $35 to drive the same distance it used to cost me $70............. and there is no knock wat so ever on gas. the car pulled 244rwhp on petrol with a dodgy tune. so it should be interesting to see what happens when it goes back for the final tune. i would recomend this conversion to any 1 who has $5k floating around with no good use.

chris

 

[Lextreme II]

Chris,

Do u think you reduce the picture size? Its too big and hard to see.

 

[Death By Bass]

Chris,

Do u think you reduce the picture size? Its too big and hard to see.

dont you like scrolling? :

my sources tell me that the largest direct injector will only support about 40kw each...

for me, this means two injectors per cylinder, maybe more, for the aimed power...

its just not practical for me at this point in time, although I do like the idea...

 

[urtwhistle]

sorry guys about the massive picture size, i posted with out previewing it.
from what i can tell so far you would be correct about the 40kw. but that fine by me. 240kw out of a 2.5lt family wagon should be just nice.