GolfGTIforum.co.uk
Model specific boards => Golf mk2 => Topic started by: Ben Lessani on 17 April 2009, 19:40
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Its not a remote consideration for me, but I remember seeing a car a while back with a K-Jet turbo, but I was wondering how on earth it works.
I thought the idea of K-Jet was a plunger driven off a vacuum, how on earth with it work with forced induction? It would be at full fueling constantly.
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turbo goes between metering head and throttel body
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No then it would underfuel loads surely?
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No then it would underfuel loads surely?
Presumably no matter where the turbo is, the K-Jet fuel supply would need beefing up anyway. Bigger injectors, upping the pressure etc.
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K-jet is bad enough on a non turbo engine!!
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Volvo and Peugeot have done it plus Tickford did a converson on the Capri 2.8 not 100% sure but I believe the metering head was sealed somehow.
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turbo goes between metering head and throttel body
But surely that would just pressurise the intake and force the plunger arm shut?
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I keep hearing the word 'piggyback' when it comes to these shoddy k-jet turbo conversions.
Can someone explain what 'piggyback' means on these conversions?
am i right by thinking its a pikey setup?
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Piggy back is I believe where an extra Electric magical box sits between the ECU and the loom and changes the signals sent, kind of a crude remap :)
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Any clues here Ben :wink: http://memimage.cardomain.com/ride_images/3/2138/1041/30343020013_large.jpg
Tom
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the K jet metering head measures air flow and dishes out fuel according to the shape of the bowl the flap rests in.
when you do a k jet turbo the turbo is downstream of the metering head so air is flowing through the metering head at atmosperic pressure then getting compressed by the turbo and presented to the throttel body. the KR metering head can be used if it's fetteld but all out max is 220 bhp and then you are askign to melt stuff, so you use a saab or volvo metering head and injectors and a few other bits of pipework.
it's a very nasty system tho as effectivly you have a 1D fuel map fuel injected v's airflow so lots of throttel low rpm and light throttel high rpm = roughly the same thing so there a bit suseptable to fueling problems and quite thirsty.
ignition is another issue leave the stock ignition system on and it'll go bang. so ether some piggyback box like k star is used to botch it, and aftermarket ignition controller or a reworked 8v dizzy with boost retard is retrofitted to the motor. these dizzys are to be fair NASTY. all in to build a K jet turbo you need tough pistons you have to run the engine richer than you would most of the time compared to the same engine with EFI, and also have to be gentel with bringing the ignition advance in.
all in all it add up to a thirsty engine that just isn't efficent and dosent last very long
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Have 10/10 for that excellent explanation.
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sounds like a rubbish conversion.
If I was going to do a cheap turbo conversion, i would get a manifold and a presurerised carb and ditch the K-tronic gumph.
if anyone has ever owned a Renault 5 GTT or Renault 11 turbo - so simple to re jet the carb and tune it up and keep it safe (tune it with the aid of a wide band lambda) for years in my early 20s I had 5gtts and a rare 11 T running 160 odd hp and lbs/ft rock solid day to day
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k jet tubo is better than pressuried carb in a lot of ways. OE they were relaible as proved by the audi 10V turbo but the 4 cyl k jet turbo conversions were allways ropey. if i was doing a chep turbo conversion id use a modifyed OE ecu with a map sensor like digifant 1 or 3