Jukka Harkola

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;

tn_viku1.jpg (2040 bytes) tn_viku2.jpg (2240 bytes) tn_viku3.jpg (2076 bytes) tn_viku4.jpg (2292 bytes) tn_viku5.jpg (2501 bytes)

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 :)

Torque charts.

'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.'

Torque chart


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.'