NG horsepower upgrades

Huw Powell audi at humanspeakers.com
Thu Aug 26 00:33:34 EDT 2004


This is a reply to several parallel and serial threads on this topic...

> So, I just got my new (to me) ng engine home into my garage. My plans
>  are... [snipped]

> I really wanna break 200hp on a 2.3 na i5.

Whoa, I was taking this message seriously until that!  And a ten valve,
at that.

> 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 90Q)?

I don't think so, see more yap of mine below.

> 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.

Now, those numbers I believe are attainable.

> 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.

The 4kq 5-3-1 manifold & downpipe are worth 5 hp compared to the 5-1 log
style manifold on the 2.2 liter 84-87 coupe gt.  The two cars use the
same engine, that is the ony difference, and they are rated 115 & 110 hp.

The 2.3 liter engine, in the 87.5 coupe & in the 88-92 80Q/90/90Q uses a
similarly nice 5-2-1 manifold/downpipe combination.  I see no point in
changing.

> 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

I still don't buy numbers that high for the ten valve i5 without forced
induction.

> A turbo motor will cost less than that and give you 220BHP almost 
> instantly....

If those high numbers were possible on a driveable, streetable car,
wouldn't Audi have got more than 130 hp on their own?  After all, why
bother with all that expensive turbo hardware and management if 180-200
hp was possible without it?

> 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 ;)

Of course, if all you want the car to do is make that hp at WOT and peak 
revs, and not necessarily be a street driveable car, I suppose my 
arbitrary imagined hp limits might be out the window.

> I mean the aluminium adaptor that goes on the cis metering head to 
> the turbo. Cut it and shut it and adapt it to go straight to the tb 
> on NA cars, I think its cos it has a smoother change in rofile, and 
> no internal waffling.

This refers to the previous comment to get rid of the airplate to 
throttle body hose.  Which is not "waffled" on the inside.  Why exactly 
is this part a problem?

> Why is everyone so quick to get rid of the CIS? 
> I don't see the big airflow restriction.

The air metering system used on the CIS cars is very resistive to flow. 
  To check this out, try lifting the air plate in its cone sometime when 
the fuel pump is running.

Now, it doesn't exactly take "horsepower" to lift it, but that 
resistance to motion must affect throttle response.  It also has an 
upper limit to motion, corresponding to a maximum amount of air that can 
be correctly fueled.  Those who know suggest a fueling limit of about 
160 hp from the 5 cyl CIS systems.

Higher-tech air flow measuring devices (like those heated wire things) 
don't interfere in the flowing capability of the system the same way.

Adding a programmable EFI system allows for fine tweaking of fuel/air 
maps, especially when extra fuel is needed to prevent knock at high 
power levels.  Ditto a spark system that can be "opened up" and adjusted 
by the tweaker.

I'd love to see dyno and time slips on these engines when the projects 
are done!

-- 
Huw Powell

http://www.humanspeakers.com/audi

http://www.humanthoughts.org/


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