NG horsepower upgrades

Alan Pritchard apritchard at
Wed Aug 25 09:50:48 EDT 2004

Research suggest sticking with 35mm exhaust valves, and stock inlets,
possibly use 7mm stem exhaust valves instead of 8mm stemmed items, about
25-30 us dollars each, enlarging the inlet can lead to head cracking.
Searching around uk vw sites I decided to stick with 10.5-1 cr for safety,
and im thinking of 95-98 uk octane... and aftermarket efi and spark, also
ceramic coating... I think 11-1 on cis is too silly.... Ditch the stock
manifold and go for the 5-3-1 affair...worth ~5bhp on its own apparently,
and maybe more at the top end. Buy a custom autocraft cat back system for
~£200 iirc... off the top of my head, that's 2.5"  don't try and make your
own (this is Quattro right?) it's a nitemare imho, also stock system is
2.25" anyway. The custom autocraft system made a very noticeable difference,
but that was after a schrick 272 was in.... 
The stroked bottom end on a big valve head is reputed to make 170+ on its
own as far as I can tell from the internet, not sure if that included cam...
Bin cis, it's the biggest restriction at the moment, plus the car idles like
a biaatch cammed up... don't even know if mine will pass emissions at the
moment...If you are in the uk, chuck the cat away, maybe put another
silencer in its place, mine is going...
Do a bit of head and manifold cleaning up....
If you must stick with cis try and get a urq airflow meter-tb "tube" its
aluminium instead of waffled rubber, modify it to take some samco or the
like to your throttle body. Heard about this on the golfs, I think one guy
even made his own with copper tubing, apparently this makes a noticeable
difference in the internet....
Personally, with your guidelines id do this....
Organize a 5-3-1 manifold and dp, fab up a silencer between the dp and
aftermarket exhaust system.... Stage 1..... expect ~10hp+ and a good helping
of drivability.
Wait for my spare head ;) and big valve it with a 272 cam in it (don't think
you could get away with a 276 on the road and cis).got to be a total of 160+
at this point, by feel anyway....
Then realise you need to take that cis crap off and put it in the bin, have
fully mappable ignition and fuel, possibly even with wb control.
Total cost...
Manifold+dp £50
Exhaust £200
Dp-exhaust section £50
Valves, machine work £150
Cam £300 new (ish, mine was about £200 second hand)
Aftermarket efi (megasquirt) ~£400
So around about £1000
Thatll get you 180-200 bhp imho
A turbo motor will cost less than that and give you 220BHP almost
My reason for doing a NA upgrade is purely to prove a point ;) and try and
get some good times in a NA AWD drag class ;)

Best Regards,
Alan Pritchard

Network Administrator
Mechanical Design Engineer
Seaeye Marine Ltd.
+44 (0)1329 289000

 -----Original Message-----
From: 	David.Payne at [mailto:David.Payne at] 
Sent:	25 August 2004 14:28
To:	quattro at
Subject:	NG horsepower upgrades

I'm looking for some logical paths to take to up the HP of an NG motor.  I
want to keep the CIS (just spent a bit fixing it all), and want to maintain
as close to a stock appearance under the hood as possible.  Some of the
questions I have are:
Is the 4KQ manifold and downpipe more efficient than what I have (1989
Is the NG head basically the same as an 8V hyd. GTI head plus a cylinder?
Dependent on the answer to the previous ?? what is the recommended valve
sizes (head and stem)?
How much compression can I get away with using 93 octane fuel?
What is the best cat to use?
My current plan is to use Blau's cam, enlarge the TB, fab up a 2.25 inch
cat-back exhaust, mill, port and big valve the head, shoot for about 10.5
or 11 to 1 compression.  Desktop Dyno says that with 10.5 comp, 42mm intake
and 35mm exhaust (I guessed on the sizes) I should have 155 hp at 6000 and
162 lbs/ft at 4000.  Using the same combo on the 2.6 bottom end takes you
to 161 hp and 173 lbs/ft.  As good as the leak down numbers are on my
engine, I'll have a hard time justifying the 2.6 bottom end.
Alan Pritchard, lets compare ideas!
Dave Payne

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