Thread: P38a to 4 or 4.6 that is the question

Can't say what they're like on gas but there are a few folks here who can. I believe the general response is that they run well on gas... vapour injenction I think is the preferred method.

What I can comment on is 4.0 vs 4.6 in my experience...

I had a rebuilt 4.6 in a 1995 HSE P38A and thought it was great.

I then changed over to a 1999 4.0 P38A and did not notice much of a power loss at all.

I believe the major difference between the two is the engine management system. Pre-99 used the Sagem GEMS system and 99-on used the Bosch Motronic (Thor) system.

I'd like to drive a post-99 4.6 for comparison.

Cheers, Paul.

Old petrolhead's maxim: There is no substitute for cubic inches.

Originally Posted by PaulP38a

Can't say what they're like on gas but there are a few folks here who can. I believe the general response is that they run well on gas... vapour injenction I think is the preferred method.

What I can comment on is 4.0 vs 4.6 in my experience...

I had a rebuilt 4.6 in a 1995 HSE P38A and thought it was great.

I then changed over to a 1999 4.0 P38A and did not notice much of a power loss at all.

I believe the major difference between the two is the engine management system. Pre-99 used the Sagem GEMS system and 99-on used the Bosch Motronic (Thor) system.

I'd like to drive a post-99 4.6 for comparison.

Cheers, Paul.

I have a 99 Thor 4 litre on a vapour injection LPG system and I reckon its great, but I have not driven a 4.6 Thor to compare it with. I did drive Ron's 4.6 GEMS on vapour gas injection system and the power available from his wasn't that much different from mine.

For me the 4 litre is entirely adequate, but I'm not a hoon who likes to have lots of power. Others prefer more power and will prefer the more cubes to do it with. If you need more power, then there's no substitute for cubes. Or a supercharger. Or re-chipping....

Willem

I run a '96 4.6 with non vapour injected LPG, runs like a dream. Personally I cannot feel the difference between running on LPG or petrol.
I should also mention that my 4.6 was completely rebuilt.
We also own a '96 3.9 V8 Disco also on non injected LPG.
The 3.9, virtually the same as the 4.0 on the Rangie, is a tad 'slower' than the 4.6, but the difference is not that great, I find anyway.
I've not driven a vapour injected LPG so can't comment how big a difference there is between it and the standard (manifold) LPG.

I've driven both and didn't notice a dramatic difference. I opted for the 4.6 as didn't want to be driving along wondering about the difference - silly, i know...

Hi

Ihad a 3.5, 3.9, 4.0 and a 4.6

The 4.6 was a fresh motor, 9.35:1 compression with Haltech injection and gas.

That motor was a complete stonker. It blew away any standard 4 or 4.6 I pulled up next to.
The motor was built with 3.9L heads and mandrel bend exhaust.

I sold the car to a bloke I just recently spoke to again. He just had different cam and some head work done plus some different fuel system, he lost me there a bit.

Reckons its quicker than his business partners Cayenne 'S'.

We have a freeway here in SA and I use that as a performance guide for myself and it would accelerate up there very strongly right past 150km/h.
I know, I admit it, I broke the law but it sounded great up through the tunnel at full flight.

Go the 4.6 and find a high compression one.

Just my thoughts.

Happy hunting.
Oh, and the motor build cost just under $7k.

Thanks for all the input.

I think I'll keep my eye out for a post 99 THOR and not worry too much about it being a 4 or 4.6

Originally Posted by big guy

Hi

Ihad a 3.5, 3.9, 4.0 and a 4.6

The 4.6 was a fresh motor, 9.35:1 compression with Haltech injection and gas.

That motor was a complete stonker. It blew away any standard 4 or 4.6 I pulled up next to.
The motor was built with 3.9L heads and mandrel bend exhaust.

I sold the car to a bloke I just recently spoke to again. He just had different cam and some head work done plus some different fuel system, he lost me there a bit.

Reckons its quicker than his business partners Cayenne 'S'.

We have a freeway here in SA and I use that as a performance guide for myself and it would accelerate up there very strongly right past 150km/h.
I know, I admit it, I broke the law but it sounded great up through the tunnel at full flight.

Go the 4.6 and find a high compression one.

Just my thoughts.

Happy hunting.
Oh, and the motor build cost just under $7k.

Was the motor built by Triumph Rover Spares?

I see they are advertising some ex TVR 4.6 long engines currently advertised for around 6k - don't know if they're complete, rebuilt or second hand. TVR actually called the 4.6 a 4.5 although TVR Power are now selling new Coscast 4.6 replacement blocks.