OK here are my requirements

1) Boost bhp to about 200
2) Boost mid range torque (2500 to 3500 range)
3) Not lose anything over 2000rpm
4) Not too expensive

I am prepared to

1) Not drop below 99RON on fuel
2) Remove heads
3) Replace some engine components
3) Accept a small loss below stall speed.

Can't quite afford a 3.2 or the hassle of changing.

I think heads may need to be removed as there is no way I can do the exhaust manifolds in situ and 1 is blowing when cold.

Any ideas anyone?

your really looking for that sort of increase to be changing to 3.2 cams...

Not sure if the 2.6 to 3.2 is as easy and productive as 2.5 to 3.0 

Markie wrote on 25. Sep 2007 at 12:47:



Not even sure which cams are used in the DBW engines?

Last time I enquired - no chips for 2.6 so I have asked them again

I don't think they do a chip as such but they can remao your ECU via a laptop. The other option is get a 3.0......

With my previous car the biggest tork gain was from the head work as a result increasing the compression ratio..(not sure this can be done cheap style if you dont have friends in related jobs)

Changing the cams also will improve performance radically..(second hands can be cheap)

workin on valves (sure expensive eliminated)

exhaust manifolds+boxes can change the picture.. (quite pricey)

chip (sure is most cheap way)

other mods needs modification on cooling also(outside the subject)

But whatever you do consumption will be effected or you will get very little gain...if I'm not wrong..

Maybe will  be necessary to change ECU remap (also for lpg)

Fitting more lairy cams will reduce the torque at low RPM. There's always a compromise with changing just cams as you are effectively moving the range of revs over which the engine breathes effectively. I'm sure someone who's got 3.0 cams in a 2.5 will be along to quantify this. May not be worth worrying about with a relatively modest cam change. Need to know if there's a similar spec. difference between 2.6 and 3.2 though.

Porting heads, fitting bigger valves, etc. tends to be more effective at high RPM, in conjunction with cam changes because that's the area where restrictions in gas flow start to become significant. Low RPM tends to suffer again because gas velocity reduces and the engine burns less efficiently.

If it's mid range torque you want the best solution is probably more cubes - i.e. a 3.2 

However, upping the compression would also help and, given that you are on LPG that might be an interesting option. If the pistons are flat on all these engines the differences are in the combuston chamber volume. You just need to do the sums for each engine and see what'd work. Formula Here: http://en.wikipedia.org/wiki/Compression_ratio

Maybe a set of 2.5 heads would be a good option if they could be made to fit? Not sure if they'd make a significant difference - did the 2.5 have higher compression than the 2.6 or was it just the 3.0 / 3.2 that differed in this respect?

Sorting out the exhaust with a proper pair of tubular manifolds with the primaries tuned would also make an improvement in torque, I reckon. I hope somebody tries it one day

Kevin

Martin Imber wrote on 25. Sep 2007 at 12:26:

Unhitch your house from the back...