The mk3 1.9L TD power-quest
So, i htought i'd start a thread to give some new life to this slow diesel forum (no pun intended!).
Late last year I aquired a '94 Mk3 CL Golf. Personal import, 1.9L Turbo-diesel, (engine code AAZ). Note, this is not TDi, its indirect injection like the old mk1!
On the face of it, the mk3 is a pretty car - aftermarket dual round headlight clusters, dark tails and fogs, and ofcourse the elegant Speedline 16x7.5" alloys.
The car was a bit of a dawdler when I picked it up - completely standard engine.
This early model mk3 but late model IDI diesel has the same old VE injector pump that the mk1 uses, much to my joy - it is a highly tuneable item, with a couple of minutes of turning screws the car can become a totally different beast!
the Manual states the stock output to be a dithering 68hp - and i'd believe it! however, theres no question that something was still working at low rev's, because it would still pull well up long hills.
The k14 turbocharger is well matched to the engine for gnereal driving, as i realised after my first modification - a boost guage into he centre consolse, in order to see just what it was doing.
I was glad to see that the stock boost was right where it ought to be at 12psi.
my hunger for more power was overpowering, and as such the injector pump became the focus of my attention. The so called "smoke screw" was the first place to go, and with a small adjustment i soon realised just how under-fuelled this thing was - with just an 1/8th of a turn it went from "slug" to "gets out of its own way" which made me immensly happy.
next, the timing retard solenoid got my attenstion - this retads the timing at low engine speeds in order to lessen the diesel rattle - i couldnt care less! the darn car gained more than a few extra horses under 2800rpm once that was sorted.
Then i began to wonder about intercooling. I was sure that the car could take more air and fuel, but i wanted to build the foundations for future tuning, so more air came in the form of an intercooler.
some basic thermodynamics says that if the turbo is compressing the inlet air to 12psi, then it could be as hot as 130degC on exit! if i could get an intercooler to bring this down atleast to under 60deg, i would get an extra 10-15% more air into the engine - without even increasing the boost!
after a few trips to the wreckers and a lot of headaches, the intercooler from a Pug 405 SRDT found a new home above the gearbox in the engine bay, with a stainless steel cowling and ducting for fresh air from the now functional CL lower air intakes on the front bumper.
10-15% more air then translates into 10-15% more power once the fuelling is up to it, and the difference was remarkable - this car now moves very well indeed!
Up to now, the last modification was the boost compensation device on the injector pump. The pump uses a contoured pin attached to a diafragm to make fuelling adjustments - and the shape of the pin gives an indication of the fuel curve, so to speak. the standard 1.9 pin is flat, with a small bump increasing fuelling a tiny amount as boost reaches 9-10psi.
I sourced a different boost pin from a 1.6 TD pump which gives a more power oriented fuelling curve - a gradual increase as boost goes up - and this has since transformed the car into something truely fun to drive - much more power than the 1600 big carbie LS with extractors that it lives next to in my garage!
I would guess that the modifications so far have given me close to 95hp, a good 40% increase atleast - but though this doesnt sound a lot, it is the extra torque that makes the real difference. from 1500-3500rpm, the little diesel accelerates relentlessly, and its fair to say that the 60-80 time is similar, in the same gear, to the 100-120 time.
all of this without even changing the restrictive exhaust system which is seriously impeding performance..... no prises for guessing whats coming next.
I intend to keep this thread updated as more developments occur, but suffuce to say, im aiming high, but reliable.
'05 Golf 2.0 TDI - daily hack
'03 Allroad 2.5 TDI - huge exhaust, S5 wheels, V6 sound.