Building a 3.0L engine

It's a low compression engine and relies on boost to make it work properly.

Very much so, but its more the asthmatic cams that make this engine crave boost. If you ever drive you GTA with the turbo disconnected, it simply will not rev past 4k....

http://www.renaultalpineownersclub.com/ ... ht=biturbo

Ready for the 2008 season???!! I may beable to afford it by then....or not

That's my point really. It's a true old school turbo engine in that the turbo is part of its overall design.

As you've rightly said before David the first thing is to check that everything is functioning as it should be before you start tuning, and obviously if the boost just isn't there that would explain things.

Especially the comment that it doesn't want to rev!

http://www.renaultalpineownersclub.com/phpBB2/viewtopic.php?t=2005&highlight=biturbo

Ready for the 2008 season???!! I may beable to afford it by then....or not

lol, you wait till you see the induction side lined up to go with it....

As far as I'm aware nobody has ever fitted the 3 litre pistons to a 2.5 turbo lump, I did enquire many years ago whether this was feasible but could never get a definitive answer.

Well allow me It IS possible, but you have to machine out the block in order to accept the 3 litre liners, and you'll need a new crankshaft too. It'd be a lot cheaper and simpler to invest in a Laguna engine and swap out the pistons...... if they were available, which they're not.

So you're stuck with your 2.5 engine. I think the simplest and cheapest route to greater power is a set of custom conrods 5mm shorter, a crank and cams (and even heads, if you want to buy an A610 intake manifold) from a 3 litre naturally asp, a bigger turbo, better intercooler or chargecooler and a new ECU. You'll have a 2849cc bona fide turbo engine with big valves, much tougher pistons than a 3 litre, higher lift cams and an ECU to make it all work. You'll only lose 114cc over a "proper" 3 litre

In fact that gives me an idea...........

*disclaimer* - never done this, just seems obvious.

The main problem with shortening rods is you put a lot of side loading on the piston now, wear, heat etc...hence why people try not to do it. If you are going to go short rod, you need pistons with longer skirts to compensate, so you may as well for for forged pistons to start with in a lower comp and do it properly. If your going for big power you wouldnt even bother messing around with standard pistons.

I do low comp forged pistons for both 71 and 73mm bores, moly coated skirts in any spec with all rings for £750 a set..

..anyway, back out of dreamland again....

Ancillaries - its all about the right spec externals, forget about how much CC you have and the size of yer valves.... as the most powerful V6 spec doesnt come down to how big the engine is...it comes down to who can afford the best turbo, chargecooler, injectors, manifolds etc....Increasing the capacity is cheap in comparison....

I hear what you are all saying.
I do intend to get my car on a RR to check it over but unfortunately i do not know where to go!
There are a few in the area but in my experience they don't inspire much confidence if at all any!!!

I don't mind making a trip as long as i know that the RR operator knows his stuff.Any recommendations?

I am off to see an engineer friend of mine today to see what he says about the tuning side of the engine,just out of interest.
He used to work for Brian HART back in the day so he knows his stuff!

Peter, what caused your engine failure?

I'm surprised to haer that the GTA suffers from 50-60 bhp transmission lose,you would normally expect those figures from an auto box!!??

I do low comp forged pistons for both 71 and 73mm bores, moly coated skirts in any spec with all rings for £750 a set..

Not much use in a PRV then (88, 91 and 93mm bores)

Are your 93mil pistons direct copies of A610 ones?

I do low comp forged pistons for both 71 and 73mm bores, moly coated skirts in any spec with all rings for £750 a set..

Not much use in a PRV then (88, 91 and 93mm bores)

Are your 93mil pistons direct copies of A610 ones?

I use 20mm thick rings...

Nope, dished for more valve relief, as the original design means you can't run any more valve lift.

I don't mind making a trip as long as i know that the RR operator knows his stuff.Any recommendations?

Theyve only got to do a power run, and check the boost pressure is correct.

Is there any way of raising the compression ratio above 9.5:1 on an even fire 2850 cc atmo engine without machining the head down ?


10.5:1 would be good

could you lower the combustion chamber area ? (inserts or welding)

are there any high comp pistons available?

Is there any way of raising the compression ratio above 9.5:1 on an even fire 2850 cc atmo engine without machining the head down ?


10.5:1 would be good

could you lower the combustion chamber area ? (inserts or welding)

are there any high comp pistons available?

Increasing the bore size (hassle)

Smaller combustion chambers, or Z7W heads, but again, whole lot of hassle, no dizzy drive etc, inlet manifold mounting (not as much of a problem for you as your running seperate bodies)...

Forged pistons can be made, but as you have non standard cams, so you can't guarantee to not have problems, so you would need to have very high comp slugs made and then get them machined personally to your engine.

Increasing the bore is the only way of bumping up the compression without having to worry about piston/valve problems.

I've got the Z7W engine withe the 9.5:1 comp pistons
If the combustion area in the Z7W heads is 51.59 cc
and the combuston area in Z6W is 53.3 cc
and the pistons are both listed as 9.5:1 what would be the comp ratio

the thing with my manifolds is i am not really goimg to know how much it has increased lag,because i have a new bigger turbo which is going to be more laggy than the last turbo i still have a bit to do before its running nice and to see what i have gained from the manifolds,turbo set up