manifolds

maybe one of the reasons the old prv doesnt like revving is because the manifolds are restrictive and the ports are small just because you loose a little bottom end tourqe doesnt mean your car will be slower around a track

It probably wont do for big circuits, but it would kill me!!! Thats why I was interested to know what Piper/Kent were calling fast road......Ive seen them offer 250 something profiles for some cars....that would be a good compromise for me.

piper and kent must be wrong then they told me there 270 cam is fast road which is the mildest cam they do on there lists

Its all theory, you can't quote a number and it be fast road/race etc...

Modern multivalve engines such as the Nissan SR20 DET and Skyline go to the 'heady' heights of around 260 degrees when they go for a big power setup, but that number hardly sounds high, and the F1 Turbo engines, you know, the ones that revved to 15000rpm and 1000bhp only ran 244 degree items..

End of the day, if the head is of a design that no matter how much you port it, increase the valve size etc, if it max power band is going to be say 7000rpm max, theres no point using say a 290 degree cam, that will make a power band of say 5-8k...

Increasing the cam timing by around 20 degrees on both inlet and exhaust will be sufficient and increasing the lift by upto another 2mm.

For comparison, here is a plot of a GTA Lemans running the 270 profile cam, bigger turbo, 18 psi of boost and a fully remapped ecu and larger injectors..



It made 330lbft max, but up at 4500rpm, and had less torque below 3200rpm than a standard GTA, even though it was running more boost.

piper and kent must be wrong then they told me there 270 cam is fast road which is the mildest cam they do on there lists

Steve, if you look in any cam manufacturers catalogue, they don't list anything higher than '270' for any car in a TURBO application..

Normally aspirated yes...

Come on then GT5....where are the pics?????

OK some pics, best i could do
[img][img]http://i30.photobucket.com/albums/c314/leylandracer/ex2.jpg[/img][/img]

[img][img]http://i30.photobucket.com/albums/c314/leylandracer/ex1.jpg[/img][/img]

[stephendell]

Newman have done a lot of Renault cams over the years

Around £300 per cam from billet

great shots gt5 would like to see them in person i live in barnsley but visit york 3times a week

that would be fine but they are getting heat wrapped soonish just got a few more bits and bobs to go on then its down to the rollers

gt5 is there any noticible performance gain

not sure yet its overboosting and i dont have the time to get my hands dirty at the mo so im going to let noble set it up

david what sized turbo was used on power graph plus the dip in torque is most probably loss of cranking pressure because extra 50 degrees cam timing the pistons are at least another quarter of an inch up the bore before valves close forcing intake charge out of the valves so your 8to1 comp has com down to mid to low 7to 1 lift your comp back up and you will regain your loss

tests idid after rebuilding afiat uno turbo 1.4 had an 8-1 comp ratio with standard cam with 248 duration and 9.1 mm lift when i changed the cam and fitted a colombo and biriani no not the curry before someone comments they are the people who made camms for lancia abarth during the rally era any way the new cam was ground from billet keeping the same base circle with 10.4mm lift and 272 degrees duration but ilost 26 foot pound of torque i found the comp ratio or should i say cranking ratio had dropped to 6.8-1 i too off the head had it skimmed to suit and got back all but 1 foot pound total horse power and torque with hybrid turbo was 186 plus 184 at 18 psi