LPG Chimaera (Follow My Conversion)

[Sardonicus]

Not something I would be interested in personally but its very interesting reading Dave, good luck I am quite sure you will keep us posted and none of those short replies your so famous for .....

[ChimpOnGas]

Teetertank said:

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.

Thanks for your words of encouragement Teetertank.

As one of the first TVR owners to take the plunge & fit LPG to your Chimaera I welcome your input.

You are right about the injector positioning, but there's a bit more to it than just choosing to fit them vertically because is a bit better than horizontal.

Actually the reason vertical is often described as best is not really about sludging, it's more because you typically (but not always) end up with a straighter pipe run this way.

A straight run always being preferable to forcing the gas to turn in it's path from the injector to the inlet manifold.

But it's all a question of packaging, for example the pipe length from the injector to the injector nipple should never exceed an absolute maximum of 200mm.

In fact, way more important than injector orientation is this injector to injector nipple pipe length rule.

And the rule is simple:

"The Shorter The Better"

One of the biggest injector positioning issues on our engine is the physical plenum chamber design, it's one sided layout does ultimately hinder you achieving an ideal symmetrical injector layout.

So faced with these challenges a compromise must be sought.

Coming back to the maximum 200mm injector to injector nipple pipe length rule, you are actually far better off laying the injectors on their side if this means your pipe length can be made shorter than if you had mounted them vertically.

Essentially the "shorter the better" rule overrides the preferred "nice to have" vertical positioning.

At the end of the day vertical injector positioning is preferable but by no means essential.

It's well accepted within the LPG conversion industry that the Keihin LPG injector exists in a class of it's own.

Keihin injectors are of such high quality they do not suffer the same orientation issues as lesser injectors do, read the LPG forums for any length of time & quickly you'll discover that not all LPG injectors are created equal.

With the application of a very high quality & effective Prins LPG filter & the Keihin injector's own internal filters, the build up of LPG residue in the injector becomes more or less a non-issue.

As with any machine or system, following the correct maintenance schedule is essential to maintaining perfect reliability.

With every design there will be small compromises, in this case horizontally mounted injectors with shorter delivery pipes, beat a vertically mounted injector with longer delivery pipes every time.

But we continue to look at these things, there's no blue print for a conversion like this, it's very much a bespoke design.

If opportunities to do things better present themselves, they will be taken.

In fact I've already designed a cost effective dual plane inlet manifold that will deliver improvements in petrol performance & drivability yet allow for improved injector positioning so these benefits can also be enjoyed when running on LPG.

But that's all part of phaze 2, & probably a good six months off TBH.

Lets get her running nicely on LPG using the existing single plane manifold first.

[320touring]

Only mildly jealous of this project- all the car you could want, but with sensible daily running costs.

my 328 is LPG'd so I can see the appeal- be interesting to follow how you get on- certainly opens up the prospect of TVR's for me (although I need to buy the bloody thing first)

good luck!

[ChimpOnGas]

DAY THREE

Injectors plumbed in.

You can just see the 4mm i/d pipes going to each port, all 8 pipes are kept to a similar length.




Injector nipples drilled and tapped as close to the petrol injectors as poss, more best practice in the pursuit of the the best efficiency.




The vaporiser is bolted to the front chassis top rail with 3x 8mm rivnuts, the bracket is made from sheet stainless and also doubles up as a heat shield for the solenoid.




Water feed and return pipe elbows visible, the feed and return pipes will follow the inner wing and be securely fixed using the original rivet holes.

Both pipes will be heat shielded.






Tune in for tomorrow's update.

[320touring]

I take it the Fans for the rad wont draw enough air to make the vapourisor too cold to function effectively?

in my LPG car, the vap is at the back of the engine bay- out of the majority of the airflow through the engine bay?

Just asking

[ChimpOnGas]

320touring said:

I take it the Fans for the rad wont draw enough air to make the vapourisor too cold to function effectively?

in my LPG car, the vap is at the back of the engine bay- out of the majority of the airflow through the engine bay?

Just asking

Radiator fans work by drawing cold air from the front of the car through the hot radiator, therefore the resultant expelled air blowing over the vaporiser is hot not cold.

There is absolutely no possibility of the Vaporiser freezing up from the effects of being blown with hot air, quite the opposite in fact.

A vaporiser is far more likely to freeze due to cold air from outside the car rushing over it when the vehicle is at speed.

This is resolved by virtue of the vaporiser's water jacket; heated engine coolant is circulated through the vaporiser's water jacket completely eliminating freeze ups.

That's why the car will be started on petrol, within just a few minutes/miles the coolant circulating through the vaporiser will have been sufficiently warmed by the engine to allow the switch over to LPG without risk of vaporiser freezing.

Of course the fundamental reason vaporisers are susceptible to freeze ups is because the vaporiser is where the compressed liquefied gas is allowed to return to its natural gaseous state.

The by product of this process is a massive drop in temperature, think about spraying deodorant from an aerosol, it's cold isn't it.

In each example it's working just like your refrigerator does at home, any compressed gas that's allowed to escape will create a fall in temperature at the point of release.

That's why you need that water jacket, and a ready supply of hot coolant to counter the freezing effects of the expanding liquefied gas.

Actually the only potential issue with our chosen vaporiser position is it's proximity to the exhaust Y Piece which has the potential to overheat the vaporiser, this issue has been resolved by the fabrication of a stainless steel heat shield.

The absence of any catalytic converters on my engine also ensures a dramatic reduction in under bonnet temperatures when compared with standard three cat strangled set up that the car left the factory with.

In summary, I think it'll be just fine

Edited by ChimpOnGas on Thursday 28th February 12:31

[TV8]

[quote=ChimpOnGas]


Thanks

Edited by TV8 on Thursday 28th February 09:27

[ChimpOnGas]

For those of you interested in the benefits of tuning using exhaust gas temperatures, here's a quick basic overview.

http://thesensorconnection.com/applications/egt-pr...

It's important to stress EGT is nothing more than another useful piece information to assist mapping.

IT IS COMPLEMENTARY TO AFR, NOT A REPLACEMENT FOR IT.

[ChimpOnGas]

Tank trial fit, a perfect fit between the wheel arches





Now with the valve boxes fitted lets try the roof panel in the boot, perfect





How about roof off touring, will there be enough luggage space?

Again, no problems whatsoever.. and you can see the room for the petrol tank that we are happy now will hold the desired 7 gallons. Happy days





Symmetrical injector positioning fitted flat on top of the rocker covers, & they will operate just as well like this as vertically mounted. Very neat & tidy





Dash off, clock out & in goes the second petrol gauge to show the LPG level. Some electricary needed to match the petrol & LPG gauges. All part of the stealth approach





Real world confirmation all my theory & calculations were correct, & all the key issues around converting a Chimaera to LPG resolved.

A very rewarding day indeed

[SILICONEKID350HP]

Looking good Dave ! are you going to have two guages ? Keep it going

[320touring]

ChimpOnGas said:

Reasoned observations

Fair Comments Chief- just thinking out loud!

latest set of pics show excellent progress- looks probably better than factory finish!

[SILICONEKID350HP]

Whats the maximum HP the vapourisor can cope with ? Teetertank has two ,one each side .

[CHIMV8]

Will she sound the same??

[ChimpOnGas]

SILICONEKID350HP said:

Whats the maximum HP the vapourisor can cope with ? Teetertank has two ,one each side .

I was going through all this again yesterday.

My Prins vaporiser will absolutely handle 400hp no problem whatsoever, a second vaporiser is only required when you get above 450hp.

My Keihin 73 cc Yellow dot injectors easily flow 50hp per cylinder, as with the vaporiser you only need to move up to the brown 100 cc when you exceed 55hp per cylinder (440hp in a V8).

With the turbo delivering 9psi, I'll be gunning for 375hp at the crank (300 RWHP) so both the vaporiser & injectors are well within spec.

If you're still left in any doubt over the capability Keihin 73 cc Yellow dot injectors, here's another interesting LPG project.

Same Keihin 73 cc Yellow dots, this time 10 of them, end result?

505hp & over 600 ft/lbs of torque on LPG.

505 / 10 cylinders = 50.5hp per cylinder.... 50.5 X 8 = 404hp





However, with 505hp this one does need two vaporisers.

[Podie]

Not sure I'd do it, but very interesting reading.

[ChimpOnGas]

CHIMV8 said:

Will she sound the same??

In it's current normally aspirated state, it will sound 100% exactly the same.

Combustion on LPG produces the same tone & volume as combustion on petrol.

I have the no cats (pre-cats removed & ACT Flowed Y-piece) & standard silencer set up, which for me is as far as I want to go given I like to tour Europe in the car.

With this exhaust set up, it sounds like a TVR should on petrol, & will sound like one on LPG.

So absolutely no change at all in the sound department, or the performance department either.

There will be no external evidence the car is running on LPG & no loss of range or luggage capacity (roof on or off).

All the TVR thrills, practicality & unique character remain completely unaltered, this was an essential part of the design brief.

The only difference the LPG conversion delivers is the car will now return the cost equivalent of 40 - 45mpg depending on how you dive it.

Cake & eat it

Edited by ChimpOnGas on Saturday 2nd March 20:00

[TV8]

Great project Dave and look forward to seeing the turbo instal in such detail.

[rburnham11]

Great project and certainly well thought out, nice. One thing.... by law do you have to display those bright stickers on the back of the car saying that there is compressed gas on board? I hope not as if I was going all out to make it so you couldn't tell it was lpg from the outside having to put a cruddy sticker on it would drive me mad.
Just thinking out loud

[ChimpOnGas]

rburnham11 said:

Great project and certainly well thought out, nice. One thing.... by law do you have to display those bright stickers on the back of the car saying that there is compressed gas on board? I hope not as if I was going all out to make it so you couldn't tell it was lpg from the outside having to put a cruddy sticker on it would drive me mad.
Just thinking out loud

Thanks rburnham11.

Honestly folks you could take this one to a TVR show & even the TVR nerds won't be able to spot it's been converted.

Even with the bonnet open it'll be easy to miss, and with the tanks trimmed in the same grey boot carpet it's the exactly same story if I display the car with the boot open too.

With no external filler which is the normal givaway a car is running on LPG, & no nasty "gas on board" safety sticker required, it will be impossible to tell its on gas.

For some reason there still seems to be a stigma surrounding LPG, but I just don't get this.

If it sounds the same & performs the same, if it looks the same & holds the roof & luggage the same, then I can't see why there should be any stigma whatsoever?

This one isn't a taxi & it isn't a cheap old worn out 4x4 either.

It's 100% TVR, just one that will do the cost equivalent of 40-45mpg.

I hope people can see in this case the LPG stigma needs to be forgotten?

[Dr Mike Oxgreen]

The elephant in the room is government taxation policy, which is something nobody can control (not even as voters, if we're honest). It wasn't so very long ago that diesel was cheaper than petrol; I hope you reach payback before the chancellor scuppers your plans.