ScorpioV8

My L33 is getting a LS1 cam & springs, LS6 intake, headers and a tune. I'm wondering what gains in both PERFORMANCE terms and ECONOMY terms raising the compression ratio to say 11:1would have. From engine comparison tables it seems some LSX run 10.9:1 already - on pump gas??
I will be running it on propane (autogas, LPG) mostly which has an octane rating of 105, so there should not be much knocking??

5.3LJimmy

iTrader: (10)

The L33 had 799/243 casting heads from the factory(commonly referred to as LS6 heads). Why would you swap those for the LS1 heads?

To get to 11.1 compression you would need to mill the 799/243 heads .035" down to 59cc and run an 0.040" gasket. To get there with the LS1 head would require milling .050" which is a bit more than generally recommended.

The effect of raising the compression ratio is more power everywhere in the powerband. Depending on camshaft choice you should have no problem running a static compression of 11.1:1, even on pump gas.

Kory 88Iroc Lt1

iTrader: (7)

car to share any info on running lp gas?
Kory

mark21742

For every full point of compression ( going from 10:1 up to 11:1) you gain 3-4% torque and hp acrossed the rpm range.

If you go with a bigger cam that has a later intake valve closing point ( piston farther up the cylinder on the compression stroke) you will get a lower dynamic compression with the same static compression as compared to a smaller duration cam that has an earlier intake valve closing point....that's why you see a lot of aftermarket cam that want 11:1 compression ratios.

For instance my build I'm going with (255/263 .624/.624 115 comp cam) I have a static compression ratio of 12.4:1 but have only 8.22:1 dynamic compression because the intake valve closes at 85 degrees abdc....8.5:1 dynamic compression is. about max for pump gas.

ScorpioV8

Thanks for the info...
The only reason I'd swap to 241 heads is I already have a pair that have been cut 50 thou. I was wondering if I'd get more from standard 799's or high compression 241's.....
Cam advice VERY helpful - great explanation.
Yes I will post a bit about LPG, but got to go to work now - later :-)

Gareth

mark21742

If the porting is done right you can get 241s to flow pretty good

ScorpioV8

OK, running on LPG (called gas in the uk)....

In the Uk regular petrol/gas is $8.40 a US gallon!!! and premium near to $10. LPG(propane) has hardly any fuel tax on it and is about half the price, making conversion very attractive.

On modern engines there are two popular conversions, one for aluminium manifold engines in non-hipo conversions and the second injection based system for later higher hp plastic manifold engines.

I have run the first system for 50,000 miles now, never even backfired once - a common problem on badly set up systems.
Basically the liquid gas is vaporised in a engine coolant warmed vaporiser, this is then fed through a venturi ring into the intake manifold. The more the engine sucks, the more gas it gets. The system measures the lambda sensor and adjusts the gas flow on the fly to the correct mixture. Other than the restriction caused by the venturi ring, (about 10% less power) you can run straight off gas even on cold start if you want. This type can backfire if set up wrong, so use a backfire valve, or leave off a hose clip so if it does go bang it does not ruin your airbox. NOT suitable for plastic intake manifolds!!

The second type actually injects gas directly into the manifold above each port. The vaporiser delivers gas at a higher pressure and it takes warm water to work reliably, so this system does not switch over for a couple of miles from cold. Other than that, it delivers the same power (no restrictions) and does not suffer backfires. Both sytems switch off the petrol injectors when running on gas(propane).
Other than having a large tank in your boot (spare wheel well can be used in a saloon and saddle tanks can be had for 4x4's) there are no other porblems.

Benefits apart from fuel costs.....

Oil stays cleaner for longer (I used to change 3,000 on petrol, now 6,000 on gas)
Lower emissions as gas burns really well

105 RON Octane rating High compression here I come!!

Many emissions testing stations CAN NOT TEST for propane emissions so in the UK at least NO EMISSIONS OR CAT TESTS if you present your car running on gas, they do not test emissions

Systems over here can be had for under $1000, maybe a bit more if you need a big tank.
If you have a big propane tank in your yard, you could pump it into your tank yourself as you may not have filling stations so equipped - there are enough around the UK to make it easy to keep filled up.

There have been reports of some LS engines eating the valves on lpg, but a system called 'flash-lube' can be used to solve this - there is no LEAD/lead substitute in the gas.

My favored supplier is http://www.tinleytech.co.uk/ who told me that they sell a 380 bhp kit for about $900, plus a tank and tax. If that is not enough, some systems can be programmed to switch back onto petrol at high hp levels, so you could have the best of both worlds.

Hope this helps someone

Gareth

LS1121

iTrader: (17)

This is what I am looking for, do you have a link to some more tech. information. Speculators are screwing us big time and we need to get away if we can. Great Post!!!!

lubelizard

iTrader: (5)

Thanks for the information Scorpio. I don't know what propane sells for in the States, or natural gas, but they may be viable options to hedge against the gasoline issue. I do know that running them instead of gasoline provides longer oil and engine life due to the much cleaner burning. What kind of "fuel mileage" do you see with the propane as compared to gasoline?

mark21742

Could you use a type of "Y" adapter for a second set of fuel injectors (like some multiport n2o systems) with one set of fuel injectors for gas, and a second set for propane? You could run a multi pin switch (on/off/on) so only one set of injectors get energized...that way you could have the best of both

ScorpioV8

Fuel mileage is difficult as the energy value of propane is lower than gasoline. I'd base it on cost issues and say that with our prices, it costs me about 3/5th to run on propane compared to gasoline, plus half the oil changes and it is supposedly 'greener'. Not sure how that one works as I'm still burning hydrocarbons, but whatever. So it's like running with diesel car costs but without the noise, smell and smoke;-)

The injectors for the gas are a bit like NOS solonoids (only cheaper as it is lower pressure once vaporised in the unit). The propane ecu piggybacks onto the original PCM injector signal, and ignition, and TPS, and you adjust the gas flow with nozzel size changes in the manifold to get in the ballpark. It also watches the lambda and keep things spot on by varying the pulse width. The idea of piggybacking both sets of injectors is nice but there are too many other issues to make for reliable running.

LPG/propane is BIG in Europe, easiest way to find more tech detail is probably to search Ebay.co.uk for LPG injection kit, find the ecu name they are selling and search for the manufacturers website. There is a lot of Italian stuff, and Polish but they usually have multilanguage manuals for download.

HTH

LS1121

iTrader: (17)

Yes last year I was in Vegas and all the Taxi's used LPG.