xe/let camshafts

[vauxestate]

iv heard that if you put a inlet cam from a xe into a let you will gain more power as with puttin the let cam in the xe you will gain power how true is this ??

[meritlover]

true to an extent but without looking at the profiles/overlap and timing its hard to say.

if the XE cam has high overlap then it will remove a lot of heat from the combustion chamber but will make the turbo work harder and drop boost. you could probably pick up gains from advancing it a few deg though. perhaps, but perhaps not. there are bound to be losses somewhere or the LET would have had an XE cam from the factory and they would not have bothered to waste time developinig a new cam for the LET.
depends whether you want a nice good car to drive or a high peak figure to impress friends and family.

[ck]

the xe inlet cam has the same duration as the let inlet cam, only diffarence is the xe inlet cam has 1mm more valve lift hence why you can get aprox 20hp and 40lb gains when using a xe inlet cam in an let (has to be retarded half a tooth with a vernier or 7degrees)

and no an let inlet cam will reduce the power of an let. someone has probably told you that so that ppl buy there standard let cams lol...

[ck]

with the xe inlet cam fitten in an let even on std timing marls there is a massive diffarence in how the power is delivered, power comes in stronger and earlier... even better with a vernier retarded half a tooth (7degrees)

its a tried and tested mod, even with a big write up in TV mag

[meritlover]

why retard it? is this to allow the clearence of the 1mm extra lift?
surely advancing the inlet would let it open early and allow for better filling?

[ck]

with the xe inlet fitted there is slightly more overlap than the std let cam hence you have to retard this over lap out. if i remember correctly the xe inlet on a std pulley and std markings will gain aprox 10-15bhp and aprox 20lb torque, with a vernier fitted to the xe inlet cam and retarded 7degrees (or half a tooth) then you will gain aprox 40lb torque and 20hp. there is a good write up in TV cant remember what issue tho..

[djbrowney]

just to prove the point some people who are running big brake let's are running the standard xe inlet camshaft and an adj vern rather than a set of uprated ones :thumb:

[craig green]

IIRC the cam must be fitted with a vernier as the testers at Jam sport detected knocking when installed on the std timing marks. It needs retarding by 1/2 tooth to get the full gains.

[meritlover]

with the xe inlet fitted there is slightly more overlap than the std let cam hence you have to retard this over lap out. if i remember correctly the xe inlet on a std pulley and std markings will gain aprox 10-15bhp and aprox 20lb torque, with a vernier fitted to the xe inlet cam and retarded 7degrees (or half a tooth) then you will gain aprox 40lb torque and 20hp. there is a good write up in TV cant remember what issue tho..

thats a considerable gain for minimum expense/effort. i have not played with the 20XE or LET iam not the lover of the large block. so you keep the LET cam in the Exh the extra lift will help cylinder filling i guess.
why would they not have done that from the factory? high emmissions perhaps? you are knowledgable ck and you are very coherent in your explanations.
thank you today i have learned a little more than i did yesterday.

[meritlover]

IIRC the cam must be fitted with a vernier as the testers at Jam sport detected knocking when installed on the std timing marks. It needs retarding by 1/2 tooth to get the full gains.
if that is the truth there is probably improved cylinder filling and det is more easy to achieve. perhaps the ign timing was too agressive. why did they not just adjust the ign timing a few degrees?

[ck]

craig it was fine on std timing marks gaining power and torque, best at half a tooth retarded. but they tried a full tooth retarded to see what would happen. i.e without a vernier. and at a full tooth retarded yes the ecu was detecting pinking/knock and was automaticaly pulling back the ignition advance reducing power loads...

[Adam]

if that is the truth there is probably improved cylinder filling and det is more easy to achieve. perhaps the ign timing was too agressive. why did they not just adjust the ign timing a few degrees? It was a standard LET ecu, you cant adjust the ignition timing manually :thumb:

Aye, 1/2 a tooth/7degs retarded works best with the xe inlet iirc.


LEt cams into a xe will loose power/torque

[vauxestate]

right so i can put the xe cam in my let as it is an will run ok on standard markings but to get full power use a adjustble pully 1/2 a tooth/7degs retarded

[Lee H]

In theory you can put it in on standard timing marks but when I did the car felt really flat low down and I ended up swapping back to the LET cam. Every car could respond differently though I guess depending on how much head has been skimmed, how thick headgasket you are running etc.

[vauxestate]

cool sweet thankyou every one that'l be the turbo nova nealy dunn just the miami blue nova to xe now

[Dod]

IIRC the cam must be fitted with a vernier as the testers at Jam sport detected knocking when installed on the std timing marks. It needs retarding by 1/2 tooth to get the full gains.

Not entirely ture. It would be benificial but it runs very well without it. My mate has this mod done and swears by it, infact I've been in his motor and I even swear by and at it.

http://i3.photobucket.com/albums/y92/Dods1/imagem359.jpg

[meritlover]

It was a standard LET ecu, you cant adjust the ignition timing manually :thumb:


i didnt realise it was the OE ECU. not a very conclusive test then, without comparing IATs etc. perhaps the det could have been removed with a bigger intercooler or better fuel etc.... who knows.
for sure then some people will find it fine with std pullies etc.. but what ck explained is true enough with regards to overlap.

[Stuart]

http://www.vauxhall-sport-forum.com/phpBB2/xe-inlet-cam-mod-t1893.html

[ck]

spot on stuart, i forgot about that one:)

one thing though. to me the pictures mean absolutly bullcrap in that post. how can you compare an inlet to exhaust cam? lol

[Dod]

You cant, but I think it looks nice. LOL

[Stuart]

iirc, the inlet and exhaust cams on the XE and the LEt are the same in terms of the inlet matches the exhaust, bar things like dizzy drive/cam pin locations etc....

[ck]

nope lol

xe inlet is 255degrees
let inlet is 251 degrees
let exhaust is 250 degrees

not sure what teh xe exhaust cam is.

[Stuart]

250 and 251 are pretty much the same then ;) esp in terms of manufacturing tollerances.

And I mean the XE inlet/exhaust are the "same and the LEt inlet/exhaust are the "same", not that the XE and LET share the same cams.

[meritlover]

one degree is a lot when it comes between an engine detonating and not detonating. if there was a tollereace of +- 1mm on a thing like a cam, i would be worried. Mmmmm pistons with up to 4mm clearence lol