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Model specific boards => Golf mk2 => Topic started by: leeroy20vt on 08 February 2010, 20:19
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been to roling road today and he is telling me that it has to much compression to get its proper potentional any ideas
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This probably means that the ignition timing is being retarded excessively to avoid detonation, either throughout the rev range if on k-jet (not good at all everywhere) or due to the knock sensor detecting detonation on digifant (normally only in certain parts of the rev range around the torque peak/highest volumetric efficiency unless the CR is insanely high, although most systems only work up to certain RPM's IIRC).
This is definately one problem with high compression ratio's and you might be able to improve matters by using higher RON fuel or fuel supplements if this is the case, but if these dont help you probably need to reduce the CR to get the best out of the engine. You may be able to get an idea of how high the CR os on your car by doing a compression test on the engine (I would presume the readings would be quite high if the cams are not too lairy) or by taking the head off and measuring/ calculating the static CR.
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cheers doa sorry should have put its a 2.0l 16v standard on twin 40s its had new rings and head rebuilt
he said he has had to retard it to compensate and compression is 250 psi
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Yep, that probably explains it! As annoying as it is, your best option assuming better fuel doesnt work is to either swap to the engines original fuel injection in, complete with the knock sensor/sensors or swap to throttle bodies and a new ECU (megasquirt, emerald, etc etc) along with a knock sensor or two if originally fitted to selectively avoid the pinking.
Bonus of the second route is that you will get a much more driveable and powerfull engine,,,,,,,,,,, at a cost whilst you may still get problems if running stock injection and igition, without mapping to suit if possible. Other cheaper alternatives are to fit a programmable ignition system (relatively cheap compared to the full throttle body route but still needs mapping and may result in some nasty flat spots) or possibly to fit some really wild cams (and make it undrivable on carbs!) or lastly to fit a stock head with a light skim though you sound like you want the oomph lol and the head may have been breathed on a bit in other places if the CR is pretty high.
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head is complety standard no port work or any think just peeing me off i spent quite a bit setting this engine up
he said when he advanced it the oddles more oomph lol but starts pinking :cry:
how much hassle to turn back to injection as it was a 8v digifant but all wiring still in place
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Why not machine the pistons and low the cr.
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I'd try two head gaskets first as it's cheap and easy.
Nick
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2 hg would drop it too much, you do that to lower CR enough for boost! has it had a KR head fitted? if so that could be why, kr has smaller combustrion chamger. head casting part number on kr head starts with 027, abf type is 051
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2 hg would drop it too much, you do that to lower CR enough for boost! has it had a KR head fitted? if so that could be why, kr has smaller combustrion chamger. head casting part number on kr head starts with 027, abf type is 051
as far as i know its a 9a head will check in a bit tho
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Best option is to find a stock ABF head (better head and much better cams than the 9A) and bolt that on if you want cheapness.
I'd try two head gaskets first as it's cheap and easy.
Just FYI, thats not even a good idea when lowering the compression ratio for boost due to a number of factors (loss of squish, probability of failure etc etc etc)! Just because some people seem to like doing (risking more like) it on forums does not mean its a good idea lol.
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Best option is to find a stock ABF head (better head and much better cams than the 9A) and bolt that on if you want cheapness.
I'd try two head gaskets first as it's cheap and easy.
Just FYI, thats not even a good idea when lowering the compression ratio for boost due to a number of factors (loss of squish, probability of failure etc etc etc)! Just because some people seem to like doing (risking more like) it on forums does not mean its a good idea lol.
I went through that last week on here but whoever it was still wouldn't listen. Bored head or complete top end re-build in a year?
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stacking gaskets dosent seem to affect reliablity much, you do need richer afr's when hoofing it tho but it's cheep :smiley:
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go argue with toyotec if you think its a bad idea, while you're there try telling him that he shouldnt be reusing head bolts either. been running several turbo conversions like that for well over a year ;)
I'm not going to argue either way, and you certainly cant argue with the results he gets :cool:
9a could have either a KR or ABF type head, as I say check the casting part number. generally the type of rocker cover fixings are a givaway, bolts = kr head, nuts = abf head. but check the casting to be sure.
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I am prob being a numpy here, by does anyone make custom gaskets, with variation in thickness?
:smiley:
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I am prob being a numpy here, by does anyone make custom gaskets, with variation in thickness?
:smiley:
Quick google
http://www.gasketstogo.com/
I guess its pretty easy to do, give em a standard, get some bloke to work out how thick it needs to be to lower the right amount