Poor Running After Mods

[24seven 104]

I've just fitted some gti-6 camshafts and a gti-6 exhaust manifold to my 306 XS 1.8, and now it's not running properly. it's way down on power compared to before. it runs really really smoothly, smoother than it did on the standard cams in fact. but it's got abolutely no guts to it at all. I'd expected it to be more powerful, but run a little rougher, maybe not idling properly at least until it's remapped, but instead its smooth, idles better than ever but wouldn't pull the skin off a rice pudding. Could it be that the cam timing is out slightly?

[Sandy 189]

Sounds quite likely, engine light on?

[24seven 104]

nah there was no engine light. turns out it was the cam timing. Using the same method to time up the standard cams put them a bit retarded, and the engine had nothing. I've advanced them slightly and it's a lot better - oodles of torque up to 2500 rpm but from there until about 4700 there's nothing, and from there onwards it feels a little slower than standard. Do you know any more on the specifics of where the cam timing should be on a standard engine? i.e. full lift at x° rotation for inlet/exhaust shafts. As it is I've kept the relationship between the shafts as they were, but advanced them together in relation to the crankshaft, but I have a gut feeling that they should be slightly different compared to each other.

Edited August 27, 2008 by 24Seven

[Richie-Van-GTi 70 2 Cars]

Are you using the gti6 pulleys? I suspect a set of 6 pulleys would put them in their correct places. If you have access to any try shoving some slightly larger injectors in there as well, it may be a case of its running excessivley lean.

[24seven 104]

thanks for the advice. I'd thought of using larger injectors as a temporary measure until I get it remapped. th only ones I have immediately available are standard XU5A and XU9J4 ones I could borrow from the 205. might give the latter a try. I don't have a set of 6 pulleys, but apparently they're the same anyway. I'll see if I can get hold of a pair to compare. meanwhile i'm gonna try measuring the lift at tdc with a dial guage for both shafts. Any ideas what they should roughly read on these cams?

[Anthony 1,000]

I don't have a set of 6 pulleys, but apparently they're the same anyway. I'll see if I can get hold of a pair to compare. meanwhile i'm gonna try measuring the lift at tdc with a dial guage for both shafts. Any ideas what they should roughly read on these cams?

The pulleys are different as far as I'm aware - certainly the XU10J4R and RS ones are different, although they look the same.

 

From memory, the lift@TDC is somewhere in the region of 0.6mm inlet and 0.5mm exhaust as standard for GTi-6's

[24seven 104]

thanks anthony. if the R & RS are different then I'd be surpried if mine were the same either.

[welshpug 1,622]

some of them use the same pulley but a different hub, quite a few of the earlier components have been discontinued.

[24seven 104]

ahh yes of course that little hub between the shfts and pulleys will be different. the one thing that sets the timing. wonder if anyone's got some of those knocking around.

[welshpug 1,622]

if you have an earlier engine with the 3 bolts to adjust the pulley (before Build code 07608) the pulley is the same 0805 66 (NFP)

 

the gti6 uses the same hub for the intake and exhaust cam, 0805 68 the XU7 uses 0805 70 and 0805 71

 

 

later engines with the single bolt vary a little more, with a different pulley as well as hub to the XU7, though the same pulley and exhaust cam hub on both XU10's, and the same hub on both cams in the RS

 

XU7JP4 after RP 07609;

0805 83 CAMSHAFT GEAR

 

0805 84 PINION HUB ADM

0805 85 PINION HUB ECH

 

XU10J4R from RP 07609;

 

0805 A3 CAMSHAFT GEAR 42 DENTS - INJECTION XU10J4R

0805 81 PINION HUB VE - GREEN - INJECTION XU10J4R INTAKE

0805 82 PINION HUB BE - BLUE - INJECTION XU10J4R EXHAUST

 

XU10J4RS from RP 07609;

 

 

0805 A3 CAMSHAF GEAR 42 DENTS - INJECTION XU10J4RS

 

0805 82 PINION HUB BE - BLUE- INJECTION XU10J4RS

 

not particularly expensive either, £4.45 each for the hubs, and £15.85 for the pulleys, but a pair of pulleys and hubs from the exhaust cam of a XU10J4R from the scrappy may be even less

Edited August 28, 2008 by welshpug

[24seven 104]

ahh. Thanks for that. I've got the later single bolt type. Looks like a full set of 6 hubs & pulleys are needed then.

 

Cheers

[pip470 61]

Did you get this sorted?

[24seven 104]

yeah all sorted now. The camshaft timing was WAY out on both inlet and exhaust. bought a new set of GTi-6 pulleys & hubs and it's run perfect ever since. might try advancing the inlet cam a little to bring the power down the rev range, since my engine doesn't rev as high as a 6 does.