Jukka Harkola
is a Fin.
And as I already took evidence of during the IMM'95 in Sweden;
these Fins are something else.
If you ever see an immaculate modified Mini with silly amounts of
torque chances are the owner is a Fin.
Jukka is not different, as you can read below.
Nor are his friends as you can see from the pics of one of his friends, Viku's roadster.
You can't help but drewling...
Jukka Harkola's Torque Rolling Road graphics.
This is what he had to say about this so far;
- On the torque chart
- On
CompressionRatios (CR's)
And this is what Viku has been up to;
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Jukka said on this;
'Here are some photos that I have taken of my friendīs
2-seater roadster.
Engine spec is pretty hairy, 1380 cc, big valve, high CR, own
scatter cam about 300 degrees, 45 DellOrto, 50 hp nitrous
package, about 130+ hp, 0-100 about 6,1 sec with nitrous, about
6,8 without, 4 speed SC/CR box, 3,65:1 diff. It is fast and it
screams about 8000 rpm. One of the most extreme around and
prettiest, eveything is show quality finish.
Body, all steel, 2-seater, sectioned, about 3-4 inches cut at the
waistline, inc. bonnet, boot lid and doors, strengthened,
stainless roll bar. Check the photos and youīll get an idea what
has been included. Try these, lowered rocker cover, lowered
radiator, modified petrol tank ...
THIS IS ALL HOMEBUILT, except for paint.
Hope you like it. Youīll propably see it at IMM2000 unless my
friend has finished his ambitious engine swap. He is putting a
LARGE 16 V engine into his Clubman...'
See, I told you these Fins were wicked :)
'These figures were obtained with 0,5 bar boost. that has
proved to be very nice amount for road use.
I now have it on 0,7 bar which susprisingly is even nicer setting
on the road.
First measurement after 500 km too rich at the top rpm (A),
second with 9 000 km and intercooler functioning (B).
The trick (?) to get nice response even low down is to have a
large engine and high CR. Usually torque increases with engine
size and there is actually a big difference between 1275 and
1380. So by using 1380 you are better off. Secondly high CR also
promotes higher torque figures but is sensitive to excessive
boost. So I tried to balance this problem with
big engine, highish CR 8,5:1 and with intercooler. Present
conversions in UK seem to use even 10:1 CR with water-based
intercoolers (chargecoolers) with no apparent reliability
problems. And of course with Mini trans there is always the limit
of how much and for how long. I think that I could use 1 bar
boost for shorter period but even now there is enough power.
Also the turbo is actually loading all the time. The amount
depends mainly on the charger design, exhaust flow and engine
load. So even if the boost gauge shows boost (e.g. 0 bar or more)
at about 3000 rpm on 1st gear, pushing on 4 th gear from about
60-70 km/h it shows boost already at 2500 rpm. There is also more
cylinder filling happening below that RPM figure which promotes
more power. This means that the turbo engine is not an strictly
off-on case but with nice setup the power
comes fluently from low down and the peaks more or less hard
depending how successful recipe you have in your engine. I tried
to build mine with torque in mind and if you can open the excel
chart youīll see the tourque after 2500 rpm.
Lower rpm graphs are a mess because it has been a bit difficult
to get the SU fuelling spot on. It seems to have problems with
going from vac to boost condition and no matter the needle mods
it never has been perfect. Itīs much better now but not perfect.
The main problem is that there is actually a pressure loss
through the carb, as much as 0,2-0,3 bar on lower rpm. I have had
the boost gauge fitted on manifold and before the carb. The fuel
regulator senses the pressure at the plenum and keeps the fuel
pressure always about 0,2 bar above that of the air pressure. Now
you may have +0,2 bar at the plenum but still vacuum in the carb
throat. This means tah for a short time the fuel pressure is more
than 0,2 bat over the air pressure and you get more fuel. This
only caused problems on 4th gear when the load was high and revs
low. The SU just donīt react fast enough. Std. turbos donīt
seem to have this problem but mine has larger intake volume due
to intercooler and this seems to affect the overall situation.
This is all guess work because there are no similar cases around
to help me out. I have planned to fit a Dellorto turbo carb which
has superior flow to SU and is easier to adjust. But it works OK
as it is so why bother..'
And also;
'I have been following the rolling road discussion on the
Mini-list and like you may have found out there are a wide
variety
of rolling roads. The results are always open for questions and
debate but still they give some idea about your car. But you are
right, I have enough (?) power and torque.'
CompressionRatios (CR's)
'CR depends on the engine. On normally aspirated engines CR is
usually around 9-10:1, 20 years ago even as high as 11:1 was
found in certain Hi-Po US sports cars. Nowadays engines tend to
have higher CR simply because engine sensors and managements can
detect detonation and retard the ignition.
On turbo cars especially serious ones the CR is roughly
between 7-8,5:1. Lower the value higher the boost that can be
used. The limiting factor is detonation. If you have a CR of 10:1
and add an turbocharger then you are in for a lot of problems.
Pressurized air heats up and this combined with harder squeeze
due to high CR equals to preignition and detonation.
Result: minor or major disaster. If you want to retain high CR
intercooler is needed, possible with rich fuelling. Extra fuel
tends to cool the engine a bit. Too much fuel and it washes the
cylinder bores. I think that with std 9,4:1 CR and intercooler 10
psi boost would still be possible but it would be very critical
to ignition timing. Too much advance and good bye engine...
I have seen one example of 10:1 CR and turbocharger in a 2-liter
Mondeo. It was fitted with a very powerful air-to-water
intercooler (called chargecooler). I remember that the boost was
closer to 10psi. It is extreme setup but works if you can dial in
the changes in the engine management.
Any engine with higher CR should be more torquey low down
compared to similar engine with less CR. The same thing happens
with normally aspirated engines. How much is the difference ???
Canīt really tell exact because it depends on the engine, i.e.
size, number of cylinders, configuration, straigth, vee, flat
etc... Could be odd Nms, could be a lot.'