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Discussion Starter · #1 ·
Just spent half a day on the dyno to try and identify the severe shuddering I an experiencing around 4500rpm on max boost.
The fuelling with the green giants was all over the place going super rich under boost, brought the pressure down to 2.8bar and it seemed a bit better but after a road test it was no difference.......so I put the standard injectors back in and set the fuel pressure to 3.2 bar to get a bit more fuel out of them when they are maxed out.
Air/fuel ratio was then checked and was holding good up to around 4200 rpm and 250whp at about 1.2bar boost but on putting the boot down at 4500rpm, boost going to 1.6-1.7 bar the wheels started spinning up on the rollers and the John the dyno man picked up the dreaded sound of pinking so it was shut down. However, fuelling was still slightly rich when detonation ocurred and he reckoned it might clear once the revs got higher but we couldn't stop the wheel spin. (any ideas on why the pinking?)
Back on the road after dropping the boost to 1.5 bar I still get this severe juddering at 4500 but if I feed the throttle in not as agressively it'll pull rapidly to the redline.
However it'll be awkward this saturday at Bruntingthorpe driving on part throttle!
What I plan to do is fill up with some 102 octane fuel which I've just had delivered to try and hold the pinking at bay and then slowly wind the boost up until I get the shuddering than come back a little.
It looks like I might have to go for a stand alone ecu to sort this out and as Unichip are still not launching their new piggyback unit yet might have to bite the bullet and get a Motec system.
Any suggestion or comments on my observations?
 

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Who has mapped the LH for you and can't they remap it to get the fuelling right? I assume it has been mapped for the green injectors? They must have mapped it for a specific fuel pressure.

Judder at boost/RPM sounds like an ignition problem. Is the DI OK? Plugs?
 

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Discussion Starter · #3 ·
I,ve got a new di on and new plugs and have tried 3 di's and 3 amm. I don't have any mods on the ecu etc as the last time on the dyno I never had this problem although it was running lean at 4500rpm this was with standard intercooler and fuel supply. Since then I've put in a uprated fuel pump,adjustable pressure regulator with the green giants, plus a big intercooler and a N/A inlet manifold. Now putting the original injectors back in still gives me the same problem which has occurred since the other mods....but the other mods shouldn't have any bearing on the shuddering, which i assume is severe pinking.
I think its an electrical problem myself but having changed most things, don't know where to start now.
Only thing I haven't stuck in my boot is a spare ecu...doh!
I know the thought process points to not having a remapped ecu but as it ran perfect before although weak at top end I cannot fathom out what is happening now.
 

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Almost sounds like the boost is blowing the spark out at the plugs.
Im guessing youve got new plugs and have experimented slightly with plug gaps deviating from the 1.1mm spec...
Worth a try??

Pete.
 

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Discussion Starter · #5 ·
Good idea Pete, I'm also still running a 0.5 water nozzle and you were running a 1mm one if my memory of Elvington was correct, going up a few sizes might help, but have left spare nozzles at home...anyone going to Brunters with spare Aquamist nozzles, please bring them for testing purposes only!!
 

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IS your clutch OK? You sure it was wheelspin & not a slipping clutch on the rollers? Might explain the judder too...though you'd probably smell it I guess.

I know on our T16 at Goodwood, because of the wet weather we were initially unsure if we had a slipping clutch or wheelspin in 3rd, but the smell soon gave it away
 

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Discussion Starter · #8 ·
No clutch is okay its definitely something electrical. Closed the plugs, up no change, ran 102 octane race fuel still the same, upped fuel pressure, lowered it....no change....didn't have any bigger water nozzles so didn't try that.
It just won't rev passed 4500, hits the wall so I was forced to short shift.
Standard clutch is holding up very well...which surprises me though!
 

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Mark,

I'm still not convinced that your fuelling is okay. With too much fuel I get very similar 'stuttering' symptoms. I could drive through it if I applied the throttle gently. Was fuelling checked throughout the rpm range?


Alanb
 
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