Power boost valve

[Dave Meredith]

I've discovered one of these things on my TVR

The previous owner reckons it's this thing that made him increase the idle speed because of the increased fuel supply at low revs. Anyway, I'm of a mind to remove it because I don't like 'non-standard' bits. It's one more thing to go wrong and complicates a fuel system which is complicated enough already (at least it is for me! )

I've heard of them being troublesome (too high a pressure or too low). If I remove it do I need to re-tune the engine? I would be interested to know your opinions guys!

[GreenV8S]

If it's a rising rate fuel pressure regulator, then when it is working it'll give you the standard fuel pressure with the throttle closed but increases the fuel pressure more than normal as you open the throttle. In other words it'll run richer when you put your foot down. If it was running lean as standard, this might produce more power. Adding more fuel than you need doesn't produce any more power though, usually it produces less.

I said "when it is working", because one well known brand with three letters in its name has a reputation for failing and messing up the fuel pressure.

So it's a solution for a problem you may not have, which may be causing problems of its own.

[Dave Meredith]

Thanks GreenV8S - It will be coming out as soon as I get the chance. I don't want what it's giving me even if it is working alright. I never bought the car purely for it's performance although that helps

It's got a supply pipe going in to the bottom and two other pipes going to the plenum chamber. One out of the top and one out of the side. It sounds like the power boost valve would have been fitted in place of the fuel pressure regulator. I've got a jpeg of the installation but don't know how to put it in this message

Before I take it out it looks like I need to get hold of a fuel pressure regulator. Is this correct?

[350zwelgje]

Yes, you need to get a standard fuel pressure regulator, as it was replaced by what you have now. The proper one depends on the engine you have. For example I have a 350i and the regular is the same as found on all original 3.5 Rover V8 with fuel injection. If this is the case, you can get one from a landrover dealer. If you have a tuned engine, probably somebody on here can point you in the right direction and where to get it (and what the pressure setting needs to be). Standard fuel pressure is 2.5 bar (live on the continent so don't have psi information at hand).

I use a rising rate fuel pressure regulator (of the brand Peter was refuring to) and are happy with it as I can set it to 2.7 bar (have much crisper throttle response and the engine pulls much better from 2000 rpm onwards as with the std regulator). 2.7 bar seems to be a better pressure according to information from Steve Heath for the 3.5 engine. As I installed it myself, I still have the old regulator and keep it as spare part.

Rob

[Dave Meredith]

I've sourced the existing regulator for the princly sum of £4.99 so I'll be fitting it next weekend. I'm hoping for better fuel consumption and should be able to lower the idle speed which is currently around 750rpm when warm. It'll be interesting to see if the response when accelerating is any different to what it is now with the power boost valve fitted

[GreenV8S]

Dave Meredith said:

should be able to lower the idle speed which is currently around 750rpm when warm.

Do you really mean lower? Normal idling speed is around 900 rpm.

[Nacnud]

Dave Meredith said:

should be able to lower the idle speed which is currently around 750rpm when warm.

Your profile doesn't indicate which Wedge you have, but mine won't idle as slow as that.

Mine came back from the recent tune-up idling at 1200rpm which is perfect for all-weather use (engine doesn't stall when I turn the lights on).

In the Summer I lower the idle to about 800rpm as the burble sounds much better. Just have to be darned careful and remember to feather the throttle a bit when if the headlights are on or while parking (power steering will stall the engine).

[dickymint]

:Nacnud lives....he lives I tell you | Welcome back

Always thought that a "standard" 350 should idle between 600 and 800 quite comfortably unlike the larger Wedges that need higher revs.

Edited to say my old 350 had an FSE boost valve and would still idle at around 700rpm.

Edited by dickymint on Monday 16th October 18:06

[350zwelgje]

Dave Meredith said:

I've sourced the existing regulator for the princly sum of £4.99 so I'll be fitting it next weekend. I'm hoping for better fuel consumption and should be able to lower the idle speed which is currently around 750rpm when warm. It'll be interesting to see if the response when accelerating is any different to what it is now with the power boost valve fitted

Lowering it can cause too low oil flow! And not enough flow is wrecked engine.... Mine is at 850-900 rpm and that is fine to keep the oil pressure and flow at the right levels. Some highly tuned engines (probably due to camshaft and removing air flow meters) need over 1000 rpm. So 750 is the minimum, and I also would advise to increase it a bit (think that 850 was the correct setting for standard RV8s).

Rob

[Dave Meredith]

Thanks for the feedback!
When cold starting it idles at 1100rpm and when warm it's around 800. It's pretty steady so I may well leave the idle speed alone. Previous owner said that he'd raised the idle speed because of the power boost valve so I was expecting you all to say that you were all idling at lower revs! Maybe I'll leave well alone.
I've got a 350i by the way

[Dave Meredith]

...........and I've updated my profile with a picture of my TVR!

[dickymint]

This may be useful to you.........www.v8engines.com/Acrobat/Powerboostvalve.pdf