LPG in a 3rd gen Rx 7?

LPG in a 3rd gen Rx 7?

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Discussion

andytk

Original Poster:

1,553 posts

273 months

Thursday 24th February 2005
quotequote all
Can it be done.

Someone has posted on PH saying that they've heard of someone doing it.
Any details.

First off the Rx7's huge thirst would make it an ideal car for gas.
And secondly LPG is actually higher octane than optimax which would be good for preventing pinking which is a disaster for rotaries.
Plus it burns very cleanly (well set up LPG cars report that when changing the oil it looks very clean when being taken out) which might have its advantages in a rotary.

I'm not talking about some dodgy manifold setup either, I would be thinking of replacing the stock fuel injectors with LPG injectors and then remapping the ECU to compensate. In this way you can keep 90% of the stock setup you just need a new map.
It would of course then only be able to run on LPG which would have its restrictions (no driving on the continent) but I could live with that.

Plus consider this.
My local sells LPG for 29.7p litre.
Super U is about 82 a litre.
That makes it 2.76 x as expensive.

If you take say, 17 mpg and multiply by 2.76:

you get 47mpg.

So you'd be getting the cost equivelant of 47mpg and higher octane.
Christ that would make it cheaper to run that my daily hack (1.4 litre 68hp)

Anyone know if it could be done.

What kind of setup does the efi on a R34b have anyway.

Andy

tuttle

3,427 posts

244 months

Thursday 24th February 2005
quotequote all
Honestly,I don't know enough about it to answer your question but I can't think of any reasons why it shouldn't work.Bl00dy hell!,if you can double your mileage & have a better octane fuel which will burn cleaner in your car,research,do your sums & go for it.
I would imagine a conversion would be under £2k,all in,judging from other gas convs I've heard of.
Kinda takes me to thinking that I should be doing the same with the 'liner.

flat_steve

1,534 posts

254 months

Friday 25th February 2005
quotequote all
Mainly because there is no place to put the tank!

iaint

10,040 posts

245 months

Friday 25th February 2005
quotequote all
I know of a 2nd Gen (Turbo II) that's had the LPG conversion. Slight loss of power but not huge, obviously much cheaper to run. No clue if tere's a 3rd gen with it though.

One possible benefit of LPG would be the temps of the input - due to the expansion from liquid to gas it should be pretty cold and ny cooling on that side is good to lower the chance of detonation! One of the reasons that WI is a must for any seriously tuned rotary IMO!

andytk

Original Poster:

1,553 posts

273 months

Tuesday 1st March 2005
quotequote all
flat_steve said:
Mainly because there is no place to put the tank!


Does the RX 7 have a spare wheel. If so thats one place a tank could go.

If you're converting to run on only gas (as opposed to dual fuel conversions) then you could take out the petrol tank and fit a gas tank there, although the packaging (fit) might be a problem.

Also what about the boot. Is it as bad as an MX 5's boot?

I've never been in an RX 7 but from the looks alone would dearly love to own one. But the huge fuel bills would put me off driving it, which would be a crying shame.

Andy

Pulsatingstar

1,717 posts

255 months

Tuesday 1st March 2005
quotequote all
andytk said:

flat_steve said:
Mainly because there is no place to put the tank!



Does the RX 7 have a spare wheel. If so thats one place a tank could go.


It has a space saver in the bottom of the boot.

flat_steve

1,534 posts

254 months

Wednesday 2nd March 2005
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You'd think I'd know, owning one and all... Sorry!

Guy Humpage

12,047 posts

291 months

Thursday 3rd March 2005
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The only negative to LPGing turbo cars is that it takes more effort to getting the fuelling correct, so therefore costs significantly more, partly cancelling out the main reason for doing the conversion.

markmullen

15,877 posts

241 months

Thursday 3rd March 2005
quotequote all
andytk said:
Can it be done.

Someone has posted on PH saying that they've heard of someone doing it.
Any details.


It may have been me who said I'd heard of it being done, over at the Mazda Rotary Club I remember rumours.

andytk said:
If you take say, 17 mpg


You'll have to be easy on the loud pedal to get 17, I used to get 13 on average, 14 at best on a long run and 9 at worst when thraping it.

Best of luck with the conversion, sounds like fun!

huwbertus

59 posts

248 months

Saturday 5th March 2005
quotequote all
I am no expert on rotery engines but wouldn't the loss of the lubricants in petrol (preveously lead) cause more wear on the rotor seals?

I understand that in a normal engine the valve seats must be hardened (in engines not designed for unleaded) in order to run LPG due to the loss of lubrication.