Re: 1.8 head on 2L performance/tuning question

[Brett Van Sprewenburg <brett@netacc.net>]

>Okay, here's my next stupid question. I had a (16V) 1.8 head put on my 2L
>block with the Euro intake cam, new valves, guides, seals etc. It doesn't seem
>as fast, or is about the same. It has some moments of brilliance, crazy tire
>spinning stuff, but more often about the same or a bit less than before with
>the 2L head. It should have gained quite a bit of HP, so what are likely
>things to look at ? (car has 268000kms on it so anything we haven't changed is
>a candidate) The injectors were not removed, intake was just set to the side
>for the transplant. (we have a Euro manifold on order ( I think...) and will
>put in new seals then) So what are likely possibilities? Cam timing? Fuel
>supply/quality? The dreaded vaccuum leaks? It has a sort of sewing machine
>sound to it, not as growly as it was. The car is CIS, has the TT fuel
>enrichment module and TT exhaust (with the cat), and the bottom end is low
>mileage so not a likely candidate. Also it bogs a bit when first started,
>until it has run for a few seconds, and would stall if you pushed the gas
>right away. But not always.(fuel supply?) Sometimes crazy fast (this was the
>goal), but not consistent. So pardon me if this is a dumb question, it should
>be a lot better, no? Grounding can be ruled out, as can bad plug wires. Sorry
>for the longish post, just wanted to present the facts. TIA Cathy
>

I have heard that the real story on the gains to be had with the
1.8L head vs 2L head aren't all that large.  There is no denying that
stock to stock, the 1.8L intake ports flow more air, while the 2L's
exhaust ports flow slightly better.  I'm going to say that an educated
guess is that the 1.8L head outperforms the 2L at higher rpms.  My
reasoning is that at lower rpms, air velocity has a huge impact on
apparent performance.  A better flowing port is almost surely larger,
and the larger the port, the slower the air moves for a given pressure
because it's spread out over a larger area.  Note how the performance
equation was also affected by a euro intake cam at the same time.  This
affects performance throughout the rpm range with mild gains in the
low / mid range, and decent gains higher in the rpm band.  I'd hazard
a guess that the low and mid range gains of the euro cam in the stock
1.8L head have brought it back to about the same performance of the 2L
head, but you should be seeing nice gains of about 8 hp or more up top.

Other then that, be absolutely sure of your intercam and engine timing.
As being a single tooth off anywhere will drastically affect where
the car makes power.

Now that I've stuck my neck out, I'm sure someone else will take a
whack at it. :-)!

==Brett

 \/  '84 Scirocco (ITB racer 2B) | "Hot VW's, take two home. They're small"
\/\/ '88 Scirocco 16v (Show), '92 Passat 16v (Winter+) | - brett@netacc.net

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