3t/2t-gze to suit LPG

[Radar]

G'day all, now im getting pretty serious into the plan of this build and i need to know how to work all this stuff out...
I am wanting to run 11.5:1 compression with a supercharger on LPG
billet crank, forged rods, custom pistons... How do I archive this, I understand the whole thing of HEMI heads with the detonation elimination..
I want to lenghten the rods while shortening the pistons or what ever you do (please explain this part too)
I'm going alloy rods to handle the power and Wiseco custom pistons or BRD custom racing pistons.
I just want to know what kinda; dish, deck height, crank throw... Just all the tech sides of it, or at least point me in the right direction thanks... =]

Lewis

[Radar]

Ok let me, try and explain a little better what I want...
I will be running LPG needing about 13.1:1 compression to suit liquid gas injection
BUT
I want a blower too which means to run 13.1:1 compression i have to run the blower on 8psi with the compression ratio at 8.5:1... This seems very tame to me ? I'll be running alloy conrods and billet crank... can someone tell me how much more I can go?

[abently]

Are you going to run Mechanical LPG Injection or LPG Vapour Injectors ?

Secondly, where you buy your LPG makes a huge difference, as the quality varies GREATLY amongst the retailers.....

Try and use flat-top pistons to get your CR up as high as possible, if its still under 10:1 then you can run a 70% Piston OD dome on it about 4-5mm high without affecting flame travel.

Aluminium conrods are only necessary once your pushing 150-200+WHp per cylinder. But that figure really depends on each Engine, if your running the right Oil weights, pressure and clearnaces and the bearings need replacing every 2000K's etc, then you will benefit switching to Aluminium conrods. If the bearings are fine at 2K, 5K and then 10K, its safe to say you don't need to run alloy rods.

Don't worry about changing the rod/stroke ratio. There's not much to be gained unless your running piston speeds close to 25 -26m/s. Which I doubt will happen as power will most likely drop off way before then unless you re-do the Cylinder Head ports.

Also, don't go using the "Dynamic compression calculator" to determine your set-up, the truth of the matter is DCR means nothing and no Engineer uses it.

What supercharger is it and how much Airflow can it output ? Its safe to say you can run at least a 10:1 static CR with a 70lbs/min Blower on LPG.

Best bet would be to speak to maybe CAPA and see what they have done with LPG and Blowers regarding their Injection method and static CR.

[Radar]

abently cheers for the reply man, i've still got plenty of research to go by the looks of it... I think my main question is... how much boost can my engine handle reliably? The injection is just a standalone unit using a modified petrol rail and modified injectors to inject liquid LPG... direct port injection btw..

[Grega]

i'd be interested to know how you're stopping things from freezing up. mrshin on here was looking at this also some years ago now.

what supercharger are you going to run? remember our vtec friends run 10 and 11:1 comp with 7psi - alot of how your engine is going to hang together depends on how well you are tuned. given you are going to be running LPG you will have inherently cooler mixtures (careful, not too cold) - plus with the different flashpoint of LPG over PULP/ULP gives you a bit more room to move with ignition and compression.

i ran a force inducted 2TTEU thru a GRA mixer with stock pistons ect and did have issues with detonation (not to the point of destruction mind you)

theres an excellent book on proprane injection - can't remember what its called but recommdned reading. its by some fellow out of the states whos' been doing it for years.

oh and yes the quality of LPG does vary wildly - down in the city we have a butane content to propane but in the sticks where LPG is used for home heating the propane content is much much higher.

[Grega]

oh there is also stradlater on here as well

this is also a useful site : http://www.performancelpg.com/

[abently]

abently cheers for the reply man, i've still got plenty of research to go by the looks of it... I think my main question is... how much boost can my engine handle reliably? The injection is just a standalone unit using a modified petrol rail and modified injectors to inject liquid LPG... direct port injection btw..

Boost ?........

// Remember boost is just the back-pressure in the Intake manifold.

Depends which Supercharger.......... your cam timing and static CR.

You really want to use as less boost as possible for a given Airflow. Your on the right direction using a Supercharger.

Are you sure you can use modified Fuel Injectors for liquid LPG ? Boral was holding the rights to the Velo (sp?) Liquid LPG System in Australia and obviously slowing the introduction of it..... Was thinking and still considering about bringing it in from the UK (where it is also sold and people speak english lol) but then would have to do some dodgy paperwork to get the LPG System approved as the old type......

[mrshin]

Firstly, I must ask, if you're keen to go to such effort with the engine, why start with such an old engine?

[celicapain]

Unless its a nitro drinking KB big block, you've already compromised your future potential visa ve power outputs/reliabilty. and i like nutso super/turbo fours, so leave him alone mrshin, you might make him do something sensible or summin.....

[mrshin]

Sensible and playing with cars are mutually exclusive.

[Radar]

Mr.Shin - The old engine is for originality, stand alone LPG injected, rebuilt, worked, supercharged 33yr old motor and no engine swap sounds like a winner plan to me! =] The motor has everything a motor needs to push out good numbers for what it is..

Abently - Boral from my understanding don't hold the patient, they are just mass producing the custom injectors.. I think This would require more research.
When I spoke to the company that I want to buy the LPG injection setup from they recommended that I run a final compression rate of 13:1 so thats 8.5:1 with 8psi.. After some more reading and speaking to some tech head mates they basically explained that if I want more psi, just inject more fuel to match?

Grega - Cheers for the heads up, people do say LPG from small towns tend to run a little nicer. The supercharger I'm not sure of yet, still plenty of research to be done before the final decision is made to buy a certain type of supercharger.. If I'm rebuilding the engine it's all got to be matched =]

I was thinking for a driveline w58, hilux airlocker diff, and disk breaks all round

[jeffro ra28]

To clear up some common misconceptions i think everyone should read this. http://www.acl.com.au/web/acl00056.n...e?OpenDocument

LPG does not support more ignition timing advance at high revs. Only at lower revs.

Radar- Aluminium rods do not stand up to the thousands of heat cylces that a steel rod does. They are exclusively used for drag racing purposes and non endurance motorsport purposes.
If you want to spend mega $$$ and have a lightweight bottom end, then titanium rods are much better suited.

Also, as abently has pointed out, LPG RON varies ALOT! As stated in the above linked document aswell. You would have to be certain on the concistancy and qaulity of every batch. Heck even i notice a difference in LPG qaulity driving my falcon.

DCR is a result mostly derived from your camshaft timing events.

8psi and 8.5:1 static compression ratio is childsplay. Heck, you could get away with that on a bog stock engine with carbies.

EDIT: Hemi chamber elimanating detonation? A hemi chamber is the most resistant chamber shape to detonation, it does not elimanate it. However thats about the only thing it has going for it compared to a modern style squish/wedge chamber.

[Radar]

Jeffro ra28 - The LPG RON does vary alot i'm not arguing that fact, and true as it is.. Using LPG liquid injection helps this matter alot at the end of the day its still higher octang than pump ULP.. The rods, ok well I guess steal is the go cheers =] if 8.5:1 with 8psi is childs play
tell me how much do you think a motor like that could run without stressing it overly?
That article as well, is incorrect to a degree, LPG just like any type of fuel requires the right compression rate and so on for it to be burnt/exploded efficenctly.. that test is done on dual fuel cars where the compression rate would be lucky to be over 8.5:1, when fuel atleast needs 11:1

[jeffro ra28]

Its impossible to predict "how much". It seems today that the standard for moderately (10- 20psi ) boosted pump fuel engines is 8.5:1 static CR.

The engine builders goal is to create as much DCR as possible without causing detonation. DCR is practically impossible to accurately predict.


DCR is influenced by the following

Camshaft- the governor of how long the valves allow air in and out.

Breathing efficiency- how much your engine 'flows".

Ring seal- Ring sealing changes throughout RPM, all rings have some form of compression leaking.

Weather conditions- How dense and humid the air is.

That being said, in your position. If it were me, id be aiming for around 10:1 CR with a max boost of 10 psi. Mainly being dependant on your SC type and efficiency. This being the ultimate with perfect conditions. Allow less for the un controllable variables you will encounter.

[Radar]

So once I get the, numbers/sizes/flow and so on I should roughly predict the kind of potential power of my motor? I'm sure there are engine programs that you can type that kind of information into and it does the calculations and so on..
The temp and density shouldn't overly matter due to the superchargers very dense air and super cold LPG to cool the air as well as well as an expansion rate of 1:243 in the chamber