Gti6 Cam Timing Adjustment

[allanallen 528 2 Cars]

hi, There seems to be plenty of people around that have played with the cam timing on the 6 engine but I can't seem to find any specific values of how much adjustment has been made and how the engine reacts to it.

my standard engine is currently sat in the stand with the timing set as standard, I've accuratley checked the lift at TDC and have

 

inlet 0.38mm lift

exhaust 0.76mm lift

 

most people seem to advance both cams, which will give more lift on the inlet and less on the exhust at TDC. This apparently gives more mid range grunt but sacrifices top end power and you lose the 'kick up the arse at 4kish. Now does anyone know what to actually advance them to? ie 1.2mm inlet, 0.2 exhaust.

 

I've also heard mention af retarding the inlet (dan taylor IIRC) which moves the power band up and allows it to rev cleaner to the limiter? anyone got any values for this?? Although my cam wheels are virtually fully retarded at the standard setting so can't really see how this is possible?

 

I'd ideally like the engine to pull right up to limiter as it will be run with a fairly short box on my track car. I also find licking the limiter more fun than short shifting at 6k I realise the later may make a faster car but its grin factor i'm after.

 

cheers for any help, allan

[welshpug 1,662]

I find shifting at 6.5k and pulling away from the nutter smacking his head on the limiter at 7450 far more fun

[dcc 855]

Pointless doing this unless you are sure your bottom pulley is correct! i thought mine was (made 160bhp and 130ftlb on rollers) but turned out to be out quite a bit, made the car feel sluggish! surprised there was no problem with the pistons and valves!

[allanallen 528 2 Cars]

Pointless doing this unless you are sure your bottom pulley is correct! i thought mine was (made 160bhp and 130ftlb on rollers) but turned out to be out quite a bit, made the car feel sluggish! surprised there was no problem with the pistons and valves!

 

 

As mentioned I'm setting/checking the cam timing relative to the piston position so the bottom pulley has nothing to do with it?! For what its worth my standard timing was set using an aftermarket solid bottom pulley.

 

Just to clear things up i'm really after accurate measured values rather than guess work as I really dont want to risk clouting a piston. Cheers allan

[petert 591]

The theory goes that if you advance the inlet cam you'll improve low-mid range torque. However, if you don't have enough duration (as is the case with a GTi6) you'll sacrifice top end hp. An Mi16 in contrast, has more duration and thus still has a good top end when the inlet cam is advanced.

 

Again, theoretically advancing the exhaust will iimprove top end hp, because the exhaust valve is opened earlier in the cycle. Likewise, as soon as the exhaust valve opens any downward force on the piston ceases. So thus you start to loose torque. Like the Mi16, the GTi6 has very efficient exhaust port flow so advancing doesn't do much with standard cams.

 

At 0.76mm the exhaust is probably at its optimum. I wouldn't advance the inlet past 1mm however, you'll just kill the top end. Something like 0.76mm on both might be best. The reality is you've only got a few degrees to play with before you do more harm than good (both power wise and mechanically).

 

If you're checking lift @ TDC then the condition/position of the harmonic balancer is irrelevant. It's only important if using the dowel method to set the cams up initially.

 

FYI, duration at 0.050" lift

XU9J4/XU10J4 216 deg.

XU10J4R 195 deg.

XU10J4RS 205 deg.

[taylorspug 7]

I find shifting at 6.5k and pulling away from the nutter smacking his head on the limiter at 7450 far more fun

 

Except you wont...

 

Pretty much agree with Peters above post regarding sacrificing top end hp on the std '6 cams, although obviously hes saying it from a technical point of view, as opposed to my bum in seat and looking at graphs!

 

I retarded the inlet cam 3 degrees IIRC on my car when it was on the standard management, and it still pulled strong through the midrange, so im not sure why people think its going to end up with no power until after 4k, as its not really true. Mine would still pull cleanly up steep hills in 5th gear from about 2k. To me it made the engine characteristic alot nicer, much more like a 1900 MI which i liked as it made the whole car more enjoyable (if i wanted boring quick id get an 8v turbo! ). From my point of view i tried a few different inlet cam timing setups and settled on this as the best for me, plus i measured it as the quickest too (in a straight line granted). Its a 16v motor in a fun little car, half the point is revving the bollocks off of it!

 

Then when it went on the rollers with bodies on it made more power than comparable setups, and had pretty much the same torque figure. So im still not sure why its thought to be the inferior way to go? Its also worth mentioning that revving mine out has the added bonus on the road of sticking the motor nicely back into the flat area of the torque curve when i change gear. Theres a graph of mine on my project thread if you are interested.

[KRISKARRERA 2 1 Cars]

Anyone got any approximate figures? Like is it a case of gaining 2 bhp at 4000rpm but losing 10bhp at 6500rpm?

[allanallen 528 2 Cars]

cheers gents, some interesting info there.

 

As I mentioned before, i'm not sure how I can retard the timing as the pulleys are virtually in the fully retarded position?? I may be able to remove the belt and adjust the pulleys anti-clockwise a tooth then re-fit the belt. This may give me adjustment both ways

 

KRIS, When advancing the inlet it sounds like its more a case of gaining some midrange torque and sacrificing some top end horse power. Not sure if anyone will have any exact figures though.

[Tom Fenton 1,542]

Thats the way to go Al, if you count the pulley teeth and then divide into 360 that will tell you how many degrees you'll get by going round a tooth.

[welshpug 1,662]

The car I have driven and seen how much BOTH cams were moved, was not down on power whatsoever, and was up on torque by about 10 lbft over book figures.

[KRISKARRERA 2 1 Cars]

The car I have driven and seen how much BOTH cams were moved, was not down on power whatsoever, and was up on torque by about 10 lbft over book figures.

How much were they moved though?

[welshpug 1,662]

about 11 degrees.

[KRISKARRERA 2 1 Cars]

That's loads! Surely musta killed top end?

[welshpug 1,662]

nope, still pulled very well at the top, just maybe not as well as others that were dog slow in midrange

 

hard to check again now really, headgasket has gone, engine is in bits and its having a V6 engine fitted instead

Edited January 18, 2010 by welshpug

[maxi 36 1 Cars]

Is this a piss take? Is it april 1st yet?

 

Maxi

[allanallen 528 2 Cars]

Is this a piss take? Is it april 1st yet?

 

Maxi

 

which part maxi?

 

 

 

 

 

about 11 degrees.

 

If you advance the inlet cam pulley by 11 degrees over the standard setting I rekon you'll make a terrible mess of your engine. 1 tooth is around 8 degrees IIRC.

 

Did you measure the 11 degrees at the crank? That would make the cam 5.5 degrees advanced which sounds a bit more feasable?

 

allan

Edited January 22, 2010 by allanallen

[welshpug 1,662]

11 degrees crank yes

[maxi 36 1 Cars]

which part maxi?

 

 

 

 

 

 

 

If you advance the inlet cam pulley by 11 degrees over the standard setting I rekon you'll make a terrible mess of your engine. 1 tooth is around 8 degrees IIRC.

 

Did you measure the 11 degrees at the crank? That would make the cam 5.5 degrees advanced which sounds a bit more feasable?

 

allan

 

 

Exactly that fella. I would expect all sorts of colourful sounds comming from the engine if the cam was advanced by 11 degrees.

 

Maxi

[taylorspug 7]

When did we start measuring cam timing adjustment at the crank?

[maxi 36 1 Cars]

When we had the peugeot parts CD encrypted into our brains! Just think, 1000's of part numbers to clutter no end of posts giving us a high posting count........Thats living alright!

 

Maxi

[Alastairh 47]

When did we start measuring cam timing adjustment at the crank?

 

Is it the way the Welsh work?

 

Cheers though Dan, is set my timing up this week as per your instructions, seeing as I know yours goes well . Hopefully I can try it out soon!

 

Al

[welshpug 1,662]

When did we start measuring cam timing adjustment at the crank?

 

ever since cam timing wheels were attached to the crankshafts by the camshaft manufacturers I'd imagine, plus what with the figures quoted for pug cams that open around 106-110 degrees after TDC, its surely logic that you'd do the same and measure at the crank?

Edited January 22, 2010 by welshpug

[welshpug 1,662]

Is this a piss take? Is it april 1st yet?

 

Maxi

 

was there any need for that? couldn't you have said politely that you disagreed?

 

 

When we had the peugeot parts CD encrypted into our brains! Just think, 1000's of part numbers to clutter no end of posts giving us a high posting count........Thats living alright!

 

Maxi

 

What has that to do with cam timing?

 

The fact that I help people who are too lazy to look up part numbers on servicebox themselves?

 

how does that "clutter" a forum?

 

Its giving an answer, an answer or suggestion is not "clutter"

 

This is clutter;

 

Is this a piss take? Is it april 1st yet?

 

Maxi

Edited January 22, 2010 by welshpug

[taylorspug 7]

Is it the way the Welsh work?

 

Cheers though Dan, is set my timing up this week as per your instructions, seeing as I know yours goes well . Hopefully I can try it out soon!

 

Al

 

Ok Al, good stuff, glad i could help mate. Its all down to personal preference at the end of the day, but as you have mentioned its not as though mine is lacking in any department.

 

 

ever since cam timing wheels were attached to the crankshafts by the camshaft manufacturers I'd imagine, plus what with the figures quoted for pug cams that open around 106-110 degrees after TDC, its surely logic that you'd do the same and measure at the crank?

 

Im sure they do. But we have spent the entire topic talking about moving cams certain amounts (the only real mention of cranks was on the bottom pulley issue), only for you to completely change to measuring it at the crank without even stating you were? Its making it look both extremely confusing, and like you have no real clue what you are talking about...

[welshpug 1,662]

I stated that measurement because that's how cam manufacturers measure it to my understanding, not my fault someone decided to do it otherwise and they did not make it clear at all that they were doing so.