Is LPG OK for 1UZ?

The 1UZFE EGR Delete Kit is available for sale here.
Here's the dyno comparison I promised. I apologise for the quality as I just took a photo of the page it was printed on, but I'm sure it does the job!

Also while being relative is more important anyway, I might add this this guy's dyno does seem to read slightly low compared to others with the same cars. It is for this reason that I removed his name form the picture; I don't like starting silly arguments!

Celsior%20dyno.JPG
 
Sorry for the confusion; I meant using a P&H box with a standalone ECU. I realise the stock ECU and O2 feedback would get pretty confused trying to drive LPG injectors.

Nice dyno with noticeable gains. This is consistent with what a Prins rep in Canada was getting with his supercharged Cobra.

Sounds like you have a mix of equipment - are you at liberty to say what you're using, ie whose ECU, whose injectors, etc.?

From the photos, it appeared you were using the Prins converter/vaporiser, so I assumed the rest of your kit was Prins too.

John
 
If using a separate programmable ECU, why would you need separate injector drivers? Just use an ECU with suitable injector drivers instead. Without some scaling change, the stock mapping won't run with the LPG injectors too well at all.

I'm using the Prins converter and Keihin injectors, the ECU is locally made to suit the LPG injectors, but it works with the factory ECU - part way between an interceptor, piggyback and standalone ECU. I am also going to be trying several standalone ECU's for more modified engines in the near future.
 

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shinny said:
If using a separate programmable ECU, why would you need separate injector drivers? Just use an ECU with suitable injector drivers instead.
AFAIK, there really isn't a big selection of "reasonably" priced ECU's that provide true P&H drivers onboard. And driving these Keihins (or any other low impedance injector) with a high impedance driver through a resistor pack is a kluge IMO.

These are the only mainstream ECU's I've found which have at least 8 true P&H drivers onboard:

Autronic SM2/SM4
Haltech E11v2
MoTeC M48/M800
Wolf V500

Of these, the Wolf at $1895 AUD looks to be a bargain, and it has 8 ignition drivers as well.

Did I miss any? (other than suppliers like EFI Systems, of course....)
 
EMS 8860 I believe has 8, and possibly something from Microtech.
The Wolf has JUST come out, and I am looking at using it for the same purpose on a project myself at the moment. It has PWM drivers (like a Motec) which could be a big advantage. I will possibly be buying one very soon, and will see how it goes.
 
We are building a 1uzfe longblock for a customer in Australia using LPG. This setup is little special due to LPG. It gets special rings along with ceramic coating of the piston.
 
Sure does LPG runs very very cool and oil lumbrication would be another issue. so those two special progress is a must.
 
Plenty of F#rd 6cyl taxi's running around with 750,000+ km on the clock with standard internals running on lpg here in OZ.
The diffs whine and the back seats smell like puke but those engines keep going.

I always thought LPG ran slightly hotter?

As far as lubrication goes use an engine oil that is designed for lpg for correct valve ashing.

Why ceramic coated pistons? The only reason I can think they may be required is to stop piston torching when running lean.
 
David,

Why did you get the pistons and rings done? it's not them you need to worry about, the exhaust valves and expecially the seats get the real punnishment

I've been driving LPG vialle and Prins systems for the past 7 years now and only had problems with exhaust valves and seats burning down Pistons come from the engines as new, mostly because LPG doenst disolve and contaminate oil in the way petrol does.
on my current honda accord I pour in oil drive that for 15000km and take it out and it's still transparent (it's done over 200.000km now) my previous car was the same at 400.000km but had it's valves and seats replaced twice.

make sure your valves are always adjusted very well, and drive safe for many thousands of kilometers.

If anyone has problems translating dutch language from the prins website just shout.

racers over here tend to fit stelliet (don't know in english) valve seats and get serious levels of EGT whitout burning down.

grtz Thomas
 
Guys we are aware of these issues. The reason we coat the pistons and side is because LPG runs very cool. Therefore whatever heat we get we can try to keep it in the combustion chamber. Because natural gas does not have any lubrication (gas have pre-mixed lubrication due to an oil base fluid) so the valves get punish quite a bit. I consulted with my engine builder and he stated Lexus heads have good valve train and should not be a problem.
 
The reason we coat the pistons and side is because LPG runs very cool.

I consulted with my engine builder and he stated Lexus heads have good valve train and should not be a problem.

Explain that, LPG burns hotter than petrol!

indeed the lexus valvetrain parts are very good, but they will be the first to go. every LPG driven car I know has had these problems sooner or later, indeed some have that very late, honda's tend to go on and on, though european engineered (renault peugot BMW etc etc) cars tend to go pop every 200K-km at least.

grtz Thomas
 
David,

The problem occurs as follows,

I assume you know this but here goes
the valve seat burns up quiker than the valve itself, if that happens the valve can't release it's heat into the head via the seat and eventually the valve gets the hammer too,
that's why you need to adjust the valves a lot more often driving on LPG, if the shimming is out this process is speeded up enourmously,
Stihl had some problems with this on the first series of LPG powered forklifts over here, the cured it by replacing the valve seats with a different material not the valves itself. that's industrial stuff that drives 24-7 for years on end.

the problem is 2 way's the higher combustion temp and not having the abilty to get the same heat transfer as driving on petrol.

coating the valves would surely help keeping the valves in shape, but when the seats go the valve will go also no matter what sort of coating you apply, we are talking very high millage btw.

put sodium filled or coated valves in and stellite seats and you will be fine.

I'd be surprized if the stock pistons in a uz ever go pop because of driving on LPG.

Grtz Thomas
 
Nearly all the conventional wisdom we think we know from hotrodding with liquid fuel is reversed with gaseous fuel, like:

A rich mixture with gasoline is considered "safer" for a turbocharged motor because it produces lower EGT's and helps cool valves. On the other hand, a rich mixture with gaseous fuel produces higher EGT's and burnt valves!

Lean mixtures with liquid fuel puts holes in pistons, while lean mixtures with gaseous fuel simply lowers power and gives cooler EGT's.

You can ask two different LPG "experts" about rich vs lean mixtures, and you'll probably get two different answers. A guy in the business of doing LPG conversions and selling Impco gear in Canada maintains that running lean LPG mixtures is what causes valve recession and "torched" exhaust valves, when it's just the opposite that is true.

There is no evaporative cooling effect with LPG vapor injection, because it is already a gas when it enters the manifold & chamber. There "could" be some cooling effect with LPG liquid injection, but these systems are so new they really haven't hit the mainstream yet.

An LPG mixture burns at a slower rate than a gasoline mix, so it requires more timing advance to get the best power out of it. Fortunately its octane equivalency is much higher than gasoline, so the motor will tolerate the higher advance just fine. Running normal gasoline advance with LPG and a slightly richer mixture than optimum will just about guarantee burnt exhaust valves, because the mixture is still burning when it's exiting on the exhaust stroke.

Here in the US it is expressly forbidden for anyone to do a DIY LPG install for a street driven car. Doesn't mean it doesn't happen, it just means that if you're caught, you face hefty fines, and possibly a federally imposed vacation.

To legally put an LPG system on a street driven vehicle in the US, the "system" must go through an approval process similar to CARB approval, and in fact it is the EPA who oversee this. Hence, "approved" LPG systems in the USA are few & far between, which is a real pity, because LPG is such a great fuel. It's cheap & readily available, distribution is already in place, storage is no problem, retrofitting is not that expensive, and normal gasoline engines can be fitted without any major changes or problems.

About the piston coatings - regardless of the fuel, I would always coat pistons for any FI'd engine I'd build. But that's just me trying to keep as much heat as possible in the combustion chamber, rather than letting it spread to the rest of the engine.

About the valves and valve seats - I'm trying something a little different with my valve seats versus conventional wisdom. I've gone with beryllium seats instead of stellite to try to improve the heat conductivity between the valve and seat. I also had the valves ground with very flat angles to increase the width of the seating surface. They certainly won't flow as well as the nice 3 angle valve jobs, but they should cool better. Remains to be seen if this will work or not. Beryllium is certainly a lot softer than stellite, so I'll have to be watching closely for valve seat recession.

Sorry for the longwinded post, but I'm a real fan of gaseous fuels and hope they'll catch on better here in the US, soon. Perhaps with a new administration in 2008, the restrictions on fitting aftermarket LPG systems will be relaxed......
 
Hey Cribjj,

I absolutly positive that running lean on LPG will burn the whole lot up pretty quickly.

that is the reason my dads volvo went pop. even autogas (which is now prins) I believe has this in the owner manual.

In holland you're also not allowed to build a system yourself, it must be installed by an assinged workshop.
in france it's even madder, you are not allowed into several tunnels and are not allowed to park in most publik parking lots because of them saying tanks could explode, which is not true.

arn't you mistaking diesel perhaps on the rich/lean point?

Beryllium may work, though I've never seen it used in LPG conversions over here. (O.T. nice stuff for speaker cones btw, a little expensive though)

grtz thomas
 
Thomas, I'd be very curious to know the background on the lean problems you've had with LPG.

Nearly 20 years ago I was running lean burn industrial engines in a lab at AFR's higher than 20:1. Very cool EGT's and no hint at all of piston problems. We did have reduced outputs due to the smaller gross amounts of fuel being burnt, however once we were able to push enough air & fuel into them with some monster turbo's, we were able to compensate for the drop in power, and we had their ratings equal to their stoich burning brethren.

Igniting the very lean mixtures was the big challenge. We would spark ignite a very small stoich mixture in a "prechamber" then let that "torch" ignite the main lean mixture. No way could we build an ignition system capable of igniting a 20:1 or 22:1 mixture reliably.

Here is an interesting excerpt from a thread posted on an alternative fuels forum I belong to. This is by a gentleman named Franz Hofmann with nearly 20 years experience (about double mine) with alternative fueled vehicles:

Generally speaking and all things being ideal, a stoich mixture of propane has a flame travel speed of 2.1 feet per second compared to unleaded regular of 2.7 fps. The faster flame travel speed is keyed into its octane rating. Octane generally describes the resistance of the fuel to ignition (the higher the octane, the more difficult the fuel is to ignite) plus it has a higher auto-ignition tolerance. Also, the higher the octane, the longer the burn duration. This is why more HD industrial engines are running Natural Gas instead of Propane, not just because of the proximity to the fuel to the engine.

The stoich mixture is not necessarily the hottest, just the thermo-chemical balance with the most efficient conversion of compounds to energy with minimal residuals. On some engines, you can go richer and have a hotter temp, on others its leaner (you are correct about the liquid fuel evaporative effect). Going richer on gaseous fuel engines can indeed cause burned exhaust valves simply because not all of the combustion is contained in the chamber, when the exhaust valve opens, the process is still continuing and the valve head is torched. A richer mixture will burn valves quicker than a lean mixture (gaseous fuel only).

Both a lean and rich mixture will result in longer burn times (distance between HC molecules on a lean mixture, and crowding of molecules on a rich mixture).

Many research engines have been lost when the principal engineer overlooks the heat absorption factors of a vapor fuel compared to a liquid fuel. On a liquid fuel engine, it can be enriched to lower Nox, the combustion temperatures are lowered by heat absorption, whereas Nox is lowered on a gaseous fuel engine
by enrichening simply by the displacement of air. Leaning the engine sufficiently where the combustion chamber temperature is lowered, almost to the point of lean misfire can also lower Nox. Its hard to control the combustion at these levels.

I've contacted Franz and asked him to join our forum, as he is much better versed in gaseous fuels, particularly LPG than I am.
 
Going richer on gaseous fuel engines can indeed cause burned exhaust valves simply because not all of the combustion is contained in the chamber, when the exhaust valve opens, the process is still continuing and the valve head is torched. A richer mixture will burn valves quicker than a lean mixture (gaseous fuel only).


Hey there's something new to me, if that is true

anyway it says a rich mixture will burn the valves quicker, I've never had a rich running engine on LPG,
though I'm 100% sure a too lean mixture killed my renault engine's valve seats at the last head rebuild, we couldn't get the valves to shut completly anymore 25.000kms before the head was supposed to go (as per the history) exhaust gas analizing at the Prins Autogas and Vialle shop showed a much to lean mixture. the fluid/gas transformer was to blame and was replaced.

so I think in this case we could well be both right. to lean will burn the lot up and to rich will also do. I'm tempted to try out a lot on my engines normally but not this if you don't mind :no:

grtz Thomas
 
Just signed in

I just signed up, looks like an interesting forum. Thanks for directing me to this site.

Franz
 

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