Power Fc Tech Question

[warpz0r]

Hi All,

Ive booked my rb30det in for a LPG conversion and the tuner said that he can tune my power fc with just advanced timing...

question i want to know is what do i not need to now run the engine?

do i need a AFM since its just spark as the LPG carby controls gas flow?

do i need an Exhaust 02 sensor? (ecu doesnt need to increase/decrease timing as it will be manually set if possible?)

thanks

[Cubes]

Depends on the setup.

The gas injection setups replace your petrol injectors with gas injectors. The ecu then controls the injections in the usual duty cycle manner. This is the best setup for performance, reliability, economy and safety.

If you run a gas carb setup well... On N/A's they place a massive restriction on the inlet lowering performance BUT they do offer excellent economy.

SOME gas systems utilize the o2 sensor and run closed loop mode, so again better economy.

Yes you still need an AFM as how will the motor know what load is being placed on the motor.

Please do keep us posted with the results and problems you come across, shall be an interesting read.

What setup are you going? Gas injection, gas carby or the old gas O-ring setup.

[warpz0r]

Its getting the Gas research throttle body - so its a carby setup tuner said i should get between 300kms and 400kms to a tank og gas

[Sydneykid]

The LPG thing has been popping up a bit lately, understandable with the ever increasing fuel prices. Here is short blurb I posted on the Stagea forum yesterday;

Here’s a quick run down on why LPG is a bad idea;

1. You need 1.3 litres of LPG to go as far as 1 litre of 98 ron.

2. The LPG tank (being a pressure vessel) has thicker walls, hence for the same outside dimensions it will hold 20% less.

3. Add 1 & 2 together and it means 50% less distance between refills compared to he same dimensioned petrol tank.

4. LPG is now 99 ron, the 110 ron dropped to get the price down

5. There isn’t an LPG system designed for RB’s, so you would need one to be made up “special”. Think lots of $’s.

6. They will use a single point gas mixer (not 6 injectors, not sequential), it will simply be connected to the throttle, more throttle opening = more gas squirted in. No fuel mapping as such.

7. Your standard ECU will run the ignition etc

8. Driveability, cold start and run, hot run etc will all suffer as a result of the poor (in comparison) fuel metering.

9. If you live in a cold area you won’t be able to drive your car until it warms up. If you don’t warm it up, drive off and accidentally use too much throttle you may well get a gas explosion in the inlet system. Not large enough to hurt you but large enough to require a top end rebuild.

cheers

[Jimbo2000]

good read SK thanks

interesting to know its no longer 110RON which was starting to sway me a little

[Cubes]

Its getting the Gas research throttle body - so its a carby setup tuner said i should get between 300kms and 400kms to a tank og gas

Good stuff, the gas research carby completely slipped my mind. There is another much more restrictive gas carby that I have had experience with. Absolutely riped the guts out of performance. But it did return damn close to petrol fuel economy on cruise. However, give it a boot full and it sucked considerably more.

SK is on the ball with the lower octane rating, it also varys from servo to servo.

With regards to backfiring I never had any issues with the gas carby but did on the old O-ring setup.

Another issue I came across is when the motor is cold, give it a bootfull and the gas convertor will freeze as the water temp is unable to handle the conversion rate. This isn't an issue if you don't boot it until water temp is at least up.

I would only ever consider a gas conversion if it were to use gas injection. The carby setup has many flaws, as sk has suggested.

[warpz0r]

There may be some flaws but if i pay 55c per litre for my 70litre tank and get 400kms opposed to $1.55 for 98ron to fill up 68 litres to get 450km - i can see a cost difference and hopefully my wallet will too...

and on reliability

there are a couple of 9/10/11 second VL turbos going around on gas carby setups... i think its alot of people saying what they think rather than what they know. (no offence sk, maybe you do know)

[VB-]

There may be some flaws but if i pay 55c per litre for my 70litre tank and get 400kms opposed to $1.55 for 98ron to fill up 68 litres to get 450km - i can see a cost difference and hopefully my wallet will too...

and on reliability

there are a couple of 9/10/11 second VL turbos going around on gas carby setups... i think its alot of people saying what they think rather than what they know. (no offence sk, maybe you do know)

i thought there was a few VLs around to runing very low times on LPG (and if not im damn sure there are some V8's), but on fullboost its sayin that the RED XE(F?) is the first running 9s on LPG.

as for the backfiring, good systems hsouldnt do it. i was reading up on one the other day, an XR6T makin about 368rwkw (automatically switching between petrol and LPG as the injectors oculdnt supply enough LPG high in the rev range) and supposedly the guy started it and straight away gave it a good hard rev... no backfire, and if he did it that time, it would only have been because he knew it wouldnt backfire... so in short, wait for a bit more developement before going LPG. i thought LPG was at 110 too, but now that i know it isnt, its not lookin as appealing

[WazR32GTSt]

there;s another thread about LPG have a read...

i had it setup on my old car - an 87 supra non-turbo and atill have it on out family car an R31

there were a lot of tething problems in getting it setup with the system "freezing" and a whole lot of other issues

also as mentioned, the fuel economy is terrible - i used to fill up every second day and that's not an exaggeration...

LPG = stupid idea.

my opinion - do what you want.

[paulr33]

also takes longer to fill up

and theres usually only 1 or 2 gas bowsers vs 8 to 12 petrol

[warpz0r]

my parents car is a 94 falcon converted to run on gas because of the long trips they make

again there is only a 50km per tank difference at just over 1/3 the price of petrol

anyways, $500 from my pocket, $2000 rebate, i dont care if i lose 20rwkw in the process because im still going to have a fast car and a fast car that will be cheaper to fill up than petrol

[Cubes]

warpz0r,

Just don't be fitting up a cheap gas system. My system years ago cost me 2.8k.

[warpz0r]

its the gas research kit with the metal cover for turbo applications

[Sydneykid]

i dont care if i lose 20rwkw in the process because im still going to have a fast car and a fast car that will be cheaper to fill up than petrol

I have yet to see an aftermarket LPG system that doesn’t loose at least 15% in power. So I strongly suggest that you do the maths on your car, our R33GTST would look like this

205 rwkw + 60 kw losses = 265 kw

265 kw – 15% = 225 kw

225 kw – 60 kw losses = 165 rwkw

That’s a 40 rwkw loss.

Forget about the max power loss, that is minor compared to the driveability you loose. The throttle response is crap, the lag is much more noticeable. The idle is rough, it doesn’t like power steering, aircon and large electrical loads. Plus it will run like shit when it’s cold.

All for a lousy $20 a week, it’s bad value for money in my opinion.

cheers

[Sydneykid]

i thought there was a few VLs around to runing very low times on LPG (and if not im damn sure there are some V8's), but on fullboost its sayin that the RED XE(F?) is the first running 9s on LPG.

as for the backfiring, good systems hsouldnt do it. i was reading up on one the other day, an XR6T makin about 368rwkw (automatically switching between petrol and LPG as the injectors oculdnt supply enough LPG high in the rev range) and supposedly the guy started it and straight away gave it a good hard rev... no backfire, and if he did it that time, it would only have been because he knew it wouldnt backfire... so in short, wait for a bit more developement before going LPG. i thought LPG was at 110 too, but now that i know it isnt, its not lookin as appealing

Tuning LPG for WOT with an auto box for a 1/4 mile run is a piece of cake, try driving the car around everyday. That’s the real test.

The XR6T LPG set up was basically still experimental, the gas injectors are several hundred dollars EACH. They have to be so big to control the gas pressure, plus the gas fittings to feed them, they won’t fit on most inlet manifolds. There are quite a few years of development left until LPG injectors are worthwhile considering, purely from a cost perspective, then there is the packaging aspect.

As for the backfiring and freezing when cold, please tell me when you have found a “good system” because all the ones we have tried all suffer from at least one, and most from all of the symptoms.

cheers

[Beer Baron]

what car are you butchering to fit this LPG system?

[Cubes]

Are you sure 2.5k for a gas research setup?

Depending on power made it 'should' be considerably more than that as you will possibly need twin gas research carby's and twin converters.

[warpz0r]

it the 440cfm gas research carby which should flow between 250rwkw and 300rwkw so no need for twins

[Cubes]

I think your figures are out.. But I could be wrong..

440cfm is around 30.5lb/min. 30.5lb/min is around 335hp or 250kw worth of air at the flywheel, not rear wheels.

So say 190rwkw.

So how about twin gas convertors.... Unless they now have something more suitable since i dropped lpg on my v8 commodore that had an ecu, cams etc.. To be honest.. The cars performance after the conversion is really what made me sell the car.

It didn't however see any cold start issues, backfires or poor economy. BUT performance did suck. You using the propper gas research carb won't see this massive inlet restriction as I did. The gas carby i used sucked.

[warpz0r]

well they installer said its all the good stuff, and i wont be needing twin carbys... its only more money in his pocket so why would he downsell to me?

ill let you all know when i get in installed