LPG Chimaera (Follow My Conversion)

[ChimpOnGas]

Moving on, lets look at the petrol gauge:



A 200mm petrol sender has been selected to work with the bespoke aluminium reserve petrol tank, the resistance will be trimmed to show a genuine full to empty over the full working range of the existing TVR petrol gauge, reflecting the now reduced 6/7 gallon capacity.

The needle will just fall twice as fast as it does now when running on petrol.






Now lets look at the LPG gauge



Same resistance trimming story as with the petrol sender, the clock will be removed from the dash & replaced with an original matching TVR petrol gauge to display the LPG level.



One of the objectives for my conversion is that it's invisible to the casual observer

Replacing the clock with a second matching TVR petrol gauge to show the LPG level is just one of the little details that helps achieve this goal

More to follow.........

[Solitude]

Into the fire.......well done Chimpongas type bloke.

That Ribol is a touch.......negative, towards you (posts read a bit bhy) what have you done to upset her/him ?

[ChimpOnGas]

BountyHunter said:

im impressed - obviously a lot of thought has gone into this.

one thing - I recall from my own LPG experiences that you "only" get 80 - 85% ish fill rate.
so prob more like 50 litres in those tanks - but thats still 11 gallons ish.

Thanks for your support of the project BountyHunter, & to others that a have shown me their encouragement.

80% of 60 litres is 48 litres.

I'm working on an average conservative LPG fuel consumption figure of 21mpg.

This is taken as 15% lower than my absolute worst case average brim to brim petrol consumption of 24.4 mpg since I moved to the Canems engine management system.

For those that don't know, this reduction in economy is due to the calorific value of LPG being lower than that of petrol (by weight).

The 15% figure is typical touted within the LPG conversion industry, however there is some evidence (as yet un-proven) that my system may be more efficient than this.

I am reliably informed many LPG systems actually often deliver a 10% reduction in economy or better, & apparently 10% is not outside the realm of possibility on my conversion.

However, as I've already pointed out this is yet unproven, so lets err on the side of caution initially by sticking with the pessimistic 15% economy loss figure.

Right, get ready for some deeply dull maths folks

48ltrs / 4.54 = 10.57 UK gallons

10.57 x 21 = 222 miles on LPG

My design brief states a 300 mile LPG range.

So to achieve my 300 mile range we can work the calculation back like this:

300 / 21 = 14.28 UK gallons

14.28 x 4.54 = 65 litres of LPG required

At a 100% fill of 60 litres I should actually see:

60 x 4.45 = 13.21 gallons @ 21 mpg = a 277 mile range

So it already looks like I've missed my target range by 23 miles even on a 100% fill

Please read my comments above on the 80% fill rule, at the end of the day it's personal choice to exceed 80%.

Compromise exists within any design, however in this case I believe it will be the application of common sense that will deliver my requirements in perfect safety.

The good news is the times I really need that 300 mile range is when I'm touring, & long motorway trips at 80mph should actually deliver a real world figure of 25.5mpg on LPG even using the pessimistic 15% calorific loss equation.

This changes everything:

300 / 25.5 = 11.76 UK gallons (or 53.4 litres) of LPG required to meet my 300 mile range brief

So you see folks, it all depends on how efficiently we can get the engine consuming LPG.

If we achieve a 10% economy loss not the pessimistic 15%, then she'll be consuming LPG at 27mpg at a steady 80mph.

300 / 27 = 11.11 UK gallons (or 50.44 litres) of LPG required to meet my 300 mile range brief

TBH I suspect it'll be close but no banana on the whole 300 mile range objective.

But then again something in the order of 270 miles is still a very practical touring range to my mind.

Only time will tell

Edited by ChimpOnGas on Tuesday 26th February 15:08

[TVR Stef]

I'm intrigued, how do you fill the LPG tank more than the pump allows? Every pump I've used just stops at a set pressure I presume. Or is it something to do with the valve on the tank?

[BountyHunter]

ChimpOnGas said:

Please read my comments above on the 80% fill rule, at the end of the day it's personal choice to exceed 80%.

how would you fill beyond the approx 80% though ?

un my experience its the garages pumps that wont allow it (by stopping when a certain pressure level is reached) not anything you do yourself

[jojackson4]

After running a LPG transit for ten years no problems with maxing the tank the pump stops come rain or shine a full 16days of sun in the ten years
Pretty sure the tanks have some kind of pressure release or expansion built in for the 4 hot days a year we get
BRIM A WAY



I was always 5L short of full when the pump stopped unless it was very cold (most of the time) and you got an extra 2L in
Running a diesel transit now and running costs have gone up a1/3
Crack on mr chimp it's worth it

[SILICONEKID350HP]

Im surprised you have not used the space in the far right and left of the boot space ,it`s a masive area.

You can`t be putting your foot down if your worst is 22mpg ...

When the Turbo is fitted you will be getting 9mpg when you boot it ..

Fantastic project ,i will be following with interest.

I`m thinking about the piggy back type system ,it will be good enough for cruising .

You must be buying masive LPG injectors for the Turbo .

[ChimpOnGas]

jojackson4 said:

After running a LPG transit for ten years no problems with maxing the tank the pump stops come rain or shine a full 16days of sun in the ten years
Pretty sure the tanks have some kind of pressure release or expansion built in for the 4 hot days a year we get
BRIM A WAY



I was always 5L short of full when the pump stopped unless it was very cold (most of the time) and you got an extra 2L in
Running a diesel transit now and running costs have gone up a1/3
Crack on mr chimp it's worth it

Good post, I like input like this from real world LPG users

There's a nice chap over on the Wedge forum called John "Gaswedge" that I'd like to see join in here.

I know he's done many thousands of happy cheap LPG miles over quite a few years in his converted RV8 Wedge, and there's at least two LPG Chimaera's that I'm aware.

Not to mention "pjac67's" very powerful Emerald equipped & recently converted Griff too.

jojackson4's comments support what I've heard from others, with care & common sense we needn't demonise the 100% fill.

For those that don't understand what's going on, the valve is in your tank not the forecourt pump, the pump doesn't know how big your tank is, and the petrol station wants to sell you as much LPG as they can.

So why & how would the pump know to stop at 80%, like I say the cut off valve is in your tank, and it can easily be adjusted just like the ball cock on your water tank.

But I don't want to get bogged down on fill levels, you can see all my calculations above if this is your special interest.

One thing is for sure though, packaging is the issue, carrying enough gas to get a good range while still retaining sufficient boot space to take the roof panel & plenty of luggage is the biggest challenge of all.

You will always be restricted in the size of tanks you can fit in, even a few extra litres of LPG held in those tanks can make the difference between a practical conversion & one that annoys you because you're forced to constantly keep filling up.

I'm confident 270 miles is enough, but I'm still pushing for my 300 mile target, however it ends up lets not forget I've still got 150 miles of the devilishly expensive liquid fuel on board as a backup.

Thanks again for everyone's words of encouragement, I'm glad I'm not alone in seeing the potential benefits of running a TVR on LPG.

Look out for my next instalment

[mrzigazaga]

Sounds the way to go Dave..Especially if fuel prices start creeping up again..(Inevitable)..Its fun having a fast car but no good if the only thing it cant pass is a petrol garage....I emailed matey earlier so hopefully he will pop on and input some knowledge..Im thinking maybe later if i go for full boost on the SC project that gas power will be enough for the 110 jiggawatts needed to go back to the 1980's to visit TVR..Mainly for spares..The 88 MPH is no problem..Good luck with it mate...Ziga

[ChimpOnGas]

SILICONEKID350HP said:

You must be buying masive LPG injectors for the Turbo .

The turbo is a way off yet Daz, but the vaporiser allows for boost reference & has ample capacity to feed the blown engine.

You're right though mate, injectors are a different story.

Injectors do exist to do the job no problem, but I'm not keen on fitting the Keihin 100cc Brown Dots needed if it means my current normally aspirated set up can't be made to idle nicely.

In its normally aspirated guise, we're far better off using the Keihin 63cc Orange Dots.

Eight of these world class LPG injectors should give me a nice smooth idle with capacity to supply an engine producing up to 288HP.

Thats small change in your world Daz, but more than sufficient right now for my little normally aspirated 4.0 litre Gas Bag.

One step at a time me old mate

Edited by ChimpOnGas on Tuesday 26th February 20:15

[Skyedriver]

Great reading, even if I don't understand it all
LPG is the only way I could afford to run a TVR now.
One point though, my 4.0HC Chimaera only ever returned 20mpg at best as a daily driver.

[BountyHunter]

ChimpOnGas said:

jojackson4's comments support what I've heard from others, with care & common sense we needn't demonise the 100% fill.

For those that don't understand what's going on, the valve is in your tank not the forecourt pump, the pump doesn't know how big your tank is, and the petrol station wants to sell you as much LPG as they can.

So why & how would the pump know to stop at 80%, like I say the cut off valve is in your tank, and it can easily be adjusted just like the ball cock on your water tank.

I was also talking from experience (4 different LPG vehicles so far, including an RV8)

ive never even once managed more than an 85% fill ever.
ive tried too - once lpg runs out keep on turning it back on to use as much of the stuff as possible just to see how much I could get in on a refill.

If the valve is in your tank then thats fine, but I was told by several people when I bought my first lpg car that it works off the garage pump sensing the internal pressure and not going past a certain point. (which would also explain why different garages give different fill amounts - I knew of one local garage where I could always get in about 2.5 litres more lpg than anywhere else)

as for why wouldnt a garage want to see as much as possible - the worries of being sued if your tank explodes after "overfilling" would certainly be one reason.


anyways as i said this is a well thought out project, and one as a regular lpg user im going to watch with interest

good luck and well done for having the balls to do it

[BountyHunter]

ChimpOnGas said:

You're right though mate, injectors are a different story.

Injectors do exist to do the job no problem, but I'm not keen on fitting the Keihin 100cc Brown Dots needed if it means my current normally aspirated set up can't be made to idle nicely.

In its normally aspirated guise, we're far better off using the Keihin 63cc Orange Dots.

Eight of these world class LPG injectors should give me a nice smooth idle with capacity to supply an engine producing up to 288HP.

i've experienced (though it wasnt mine) an Alpina B10 V8 S with circa 375bhp on lpg - and it idled perfectly.
So it can be acheived readily enough.


one "fix" that could be used is keep the smaller injectors, and then fit a big extra injector (or more than one) that is plumbed into the main inlet tract and feeds in at higher revs.

another option would be 8 more injectors that only start to feed at higher revs (think Sierra RS500 style twin injector head - but much much cheaper)

edit.
instead of extra injectors you could probably with your system use a vapour ring for extra lpg at higher revs - in conjunction with the regular injectors.

Edited by BountyHunter on Tuesday 26th February 21:39

[SILICONEKID350HP]

I discussed an LPG conversion with a local installer ,he told me it needs a cage around it because it`s a fibreglass car ..

What about insurance ?

[ChimpOnGas]

Update, the original petrol tank is out to make way for the LPG tanks & bespoke auxiliary petrol tank.




The stainless steel bracket fab work is well under way.




Readying the injectors




And positioning making use of original fixings




Tomorrow is drilling & tapping for the injector nipples, pipework fitting too.

[ChimpOnGas]

SILICONEKID350HP said:

I discussed an LPG conversion with a local installer ,he told me it needs a cage around it because it`s a fibreglass car ..

What about insurance ?

The tanks will be securely bolted to the rear of the chassis.

TVR kindly provided four perfectly positioned & very strong mounting points.



My chosen tank position delivers the best weight distribution & the safest location by far.

LPG tanks are extremely strong, much stronger than the original TVR aluminium petrol tank in fact

Conclusion, no cage required


To answer your second question Daz, I spoke with my insurance company last week & they want £20 as a one-off admin fee to record the change to LPG.

They also confirmed my annual premium will only go up by £20 when I renew my policy in May.

Not the end of the world given the fuel cost savings

[SILICONEKID350HP]

I don`t understand why Euro boxs don`t come with LPG ,they could be an extra ..seen a guy filling up a Ford Fiesta,the tank was a perfect impression of where the spare fits ..He told me he got equivalent to 90mpg on the run , Nottingham to London cost him less than £10.. Those donut type tanks must be ready available to fit where the spare fits .

[ChimpOnGas]

Looking to get tanked up

Two is always better than one.

As the Bishop said to the Actress...

"The more holes the better"

[Teetertank]

BountyHunter said:

ive never even once managed more than an 85% fill ever.

Modifications are required to the filler mechanism in the tank to get a higher fill. ChimpOnGas described it well: as like bending the ballcock on your cistern. An LPG tank has a shut-off valve plunger; manufacturers supply these conservatively so that there is a good amount of spare space in the tank to allow for expansion if the tank heats up.

If you bend the shut-off plunger you can reduce the "safety margin". But if you have a correctly fitted escape valve then any build-up in pressure will be released from the tank anyway - so I don't think there is a danger of the tank exploding from excessive pressure. You just want to make sure that the tank vents to the outside of the car otherwise LPG can build up in your boot and a spark could then cause trouble. If you drive the car stright after filling up you will be recreating the safety margin. You just shouldn't brim it then park up with a full tank.

I have 60 litre tank and sometime manage to get more than 60 litres in there (like 61 or 62 litres in). I think the outside temperature and also the forecourt level/slope can affect how much gas you can get in too due the the incline on the plunger on the liguid gas.

[Teetertank]

This is shaping up to be a great thread - fantastic effort. Like the use of a TVR fuel guage for the LPG.

ChimpOnGas said:

The stainless steel bracket fab work is well under way.

Readying the injectors

And positioning making use of original fixings

I have heard that LPG injectors should be mounted vertically. Not sure if this is to prevent build-up of sludge or to ensure wear is even. It's probably a minor point, but seeing as you are going to so much trouble you may want to check if you haven't already.