Low Torque

[dcc 855]

Ive read on the gti6 forum that the AFR should be 12.5 with WOT, now looking at my graph my AFR is low 11's, and doesnt even reach the mid 11's untill 5500rpm.

 

What controls the AFR in a gti6 engine? What parts can I check and replace - not only to improve upon the AFR but to find why the torque is low.

 

Thanks

Dan.

[James_R 3]

Check the cam timing first off, the engine has no wideband lambda so can only see if the mixture is above or below 14.8.

 

As said check cam timing first, the ecu will fuel for the factory set timing, if it differs it will be wrong.

 

james

[welshpug 1,657]

I checked the cam timing for Dan after that RR run, the inlet was slightly off but not much at all, IIRC it was about a mm, exhaust was spot on.

[petert 587]

You need to give it a compression test first to assess if the engine is healthy. If it's down on compression (for what ever reason) the ECU won't know this (at WOT) and will be delivering the correct fuel for a healthy engine. Anything from 12.5 to low 13's would be nice. However, a low AFR will still make similar power. The lambda sensor only controls mixture at light to mid loads. The ECU will thus correct the mixture for an unhealthy engine at cruise.

[petert 587]

it was about a mm,

 

What does this mean? Lift at TDC?

[welshpug 1,657]

no, the pin hole on the cam sprocket

 

 

edit, which I think would be roughly 2 degrees odd.

Edited May 19, 2009 by welshpug

[CaptainK 11]

Hows it going with the GTi6 engine Dan? Any luck with those parts you swiped off me on the Eurotrip ?

[dcc 855]

Well after changing every sensor on the engine, and getting little to no change at all, it was decided that the timing was surely the culpret!

 

Phil (pip470) and Paul (3rdtimelucky) both got stuck in and checked the timing on my car, which with the standard pulley, as all timed up to perfection with the minor tweek that Mei (Welshpug) had made to the inlet cam. However, it turned out that the bottom pulley had turned 30-40degrees on the rubber, which quite frankly amazed us all at how it was even running, let alone making decent power (120ftlbs - 160bhp). We think it was about the equivalent to being 1.5 (probably closer to 2) teeth out! Phil and Paul then timed the engine up with a solid lower pulley as best they could and the car is living a new life!

 

Luckily the engine doesnt tap at all and pulls really well now, so we hope the valves are in good condition.

[welshpug 1,657]

phew!!! Gather it goes rather better now then?

[dcc 855]

The difference really is night and day!

[pugman211 0]

That was a lucky escape then wasnt it!! What do you think it will be maiking now??

[tagy 1]

Glad to here its sorted.

 

Bit crappy that the pulley can slip on the rubber like that.

[welshpug 1,657]

I'll be checking mine soon after hearing that Dan, I recently made a template to work out crank angles and it has the pin hole marked on it for reference, so it has more than one use!