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Discussion Starter #1 (Edited)
Had the FD2 on TDI South's hub dyno on Tuesday for some changes to the map to improve fuel economy at part throttle. To cut a long story short, when the car was dynoed pre-mapping, it mysteriously seemed to be making a few horsepower less across the rev range than when it was mapped back in December, yet nothing else has changed.

A number of possible explanations were put to me, one of which was that if the car had been over revved, the timing chain might have slipped a tooth, putting the cam timing out, especially if the chain has stretched of the tensioner is not up to the job. However, since December to now, I haven't been aware of any power drop and although I have done a couple of mishifts, I don't think I've strayed over the rev limiter. Also, the chain is still quite fresh and I'm using an uprated Toda tensioner. Has anyone had experience of jumping a tooth on the timing chan and if so, was the loss of power noticeable?

Other explanations offered were that the engine is suffering premature wear but I doubt this as the engine only has 36,000 miles on the clock, is serviced religiously (oil change with 5-40 fully synthetic every 3,000 miles), has never been tracked, has never been allowed to run low on oil and is driven with plenty of mechanical sympathy. Any feedback or ideas would be much appreciated :)
 

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change in air temp?

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DIN corrected, so climatic conditions should have no affect.
 

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Hi Andy,

Surely you would have noticed if you timing chain had jumped a tooth?

Got any of the detailed dyno sheets and AFR plots from the runs? Ideally of before and once you lost power.
 

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When you say a few, are we talking a couple of HP or 5+HP?
 

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Discussion Starter #7
Hi Andy,

Surely you would have noticed if you timing chain had jumped a tooth?

Got any of the detailed dyno sheets and AFR plots from the runs? Ideally of before and once you lost power.
I think I would have noticed, and to be honest, the car wasn't feeling any slower as far as I could determine. Might be wrong of course, but I'm getting the timing chain and cam timing checked early next week to eliminate this as a possible problem. No data sheets here I'm afraid
 

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aka Paul
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and did the power return after the re-tune?
 

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happy to be wrong but isnt the din correction based on weather reports? so if its literally 2bhp could it not be a slightly incorrect din correction? unless the dyno monitors air pressure and temp itself and is calibrated?

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happy to be wrong but isnt the din correction based on weather reports? so if its literally 2bhp could it not be a slightly incorrect din correction? unless the dyno monitors air pressure and temp itself and is calibrated?

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Not in their dyno, it's all done via sensors in the room.
 
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Could it be a fuel issue? I assume you're running 99RON (or something similar)?

Do you buy from the same petrol station? Maybe that particular station had a slightly dodgey batch of fuel and you're car is feeling the effect by losing a couple of HP?
 

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I'm thinking a maybe a slightly mucky air mass sensor or air filter, or even a difference in tyre pressures. Either way I wouldn't worry too much about a 1-2% fluctuation.
 

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Could it be a fuel issue? I assume you're running 99RON (or something similar)?

Do you buy from the same petrol station? Maybe that particular station had a slightly dodgey batch of fuel and you're car is feeling the effect by losing a couple of HP?
Andy uses a petrol + methanol mixture to further boost his octane rating. So at a guess I'd say he is running something like 104RON

If it was a fuel issue they would have noticed it I imagine. They remapped the same day, so if suddenly MBT has changed so much it would be obvious to them when comparing to the old cal.

I'm thinking a maybe a slightly mucky air mass sensor or air filter, or even a difference in tyre pressures. Either way I wouldn't worry too much about a 1-2% fluctuation.
FD2's do not use MAF sensors. Also tyres are not used on a hub dyno.

i dont understand why tdi think its a belt jump? has the timing changed?

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+1 :confused:
 

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Discussion Starter #17
Could it be a fuel issue? I assume you're running 99RON (or something similar)?

Do you buy from the same petrol station? Maybe that particular station had a slightly dodgey batch of fuel and you're car is feeling the effect by losing a couple of HP?
Yes, this is something I wondered but the car was fuelled the same as always - with V-Power, so unlikely I guess
 

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Yes, this is something I wondered but the car was fuelled the same as always - with V-Power, so unlikely I guess
I know it sounds a bit odd, but you may have filled up at the station when they were nearly empty which means you get the 'leftovers' and the car may not respond quite so well to it.

Or the station you bought it from is dodgy and watering down their petrol :facepalm:

Just a thought, hope you figure it out soon though.
 

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Discussion Starter #19
i dont understand why tdi think its a belt jump? has the timing changed?

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They weren't sure to be honest. To bring the power back up, they did have to play around with both cam timing and fuelling. One thing that crossed my mind was the calibrations used - to get better and more economical performance with my big bore throttle body, we had to use a different cal (one with an adjustable pedal to throttle translation table in). I am wondering if the logic could be different in that cal - ie, the same data transferred across doesn't yield the same results. I have emailed Hondata to ask them to clarify.

Personally, I'm not convinced it's jumped a tooth as I'm sure I would have noticed a real 'step change' in performance at the time.
 

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Discussion Starter #20
Andy uses a petrol + methanol mixture to further boost his octane rating. So at a guess I'd say he is running something like 104RON

If it was a fuel issue they would have noticed it I imagine. They remapped the same day, so if suddenly MBT has changed so much it would be obvious to them when comparing to the old cal.



FD2's do not use MAF sensors. Also tyres are not used on a hub dyno.



+1 :confused:
Cheers Ash - you're better at answering the questions than I am ;)
 
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