Twin Spark Engines

Alfa Romeo ONLY please!
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Micke
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Re: Twin Spark Engines

Post by Micke » Sat Apr 06, 2013 11:20 am

Seems it's finally time for me to move from the old Nord time to modern TS era.
New 85.2 mm pistons and liners just arrived. Call me a sucker for shiny things but the pistons are pure p*rn.
Design criteria destroyed my plans to go short stroke. So, instead we'll see what's the max hp we can achieve. Piston weight and thin rings make high rpm possible.
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Re: Twin Spark Engines

Post by Mats » Sun Apr 07, 2013 1:53 am

Oooh, shiny...

Looks like pretty agressive squish?

Prego scale? :lol:
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Re: Twin Spark Engines

Post by Micke » Sun Apr 07, 2013 4:21 am

As squishy as possible with the TS head.

They were out of Grazie scales.....
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Re: Twin Spark Engines

Post by kterkkila » Sat Dec 28, 2013 1:37 am

kterkkila wrote: Just wondering, why some say that 22 m/s piston average speed is typical for endurance racing and 25 m/s for short races? Like this one:
http://hpwizard.com/mean-piston-speed.html

With 88.5mm stroke 22 m/s would be equal to 7460 rpm. So in my case
- 20m/s (6780rpm) -> oil consumption is OK
- 21m/s (7120rpm) -> oil consumption is too high, might survive on a race or not
- 22m/s (7460rpm) -> dead engine, around 1 liter per hour..
After wondering a while and collecting some information:
http://alfatune.fi/cms_naytasivu.php?si ... anguage=en
Last edited by kterkkila on Sun Jan 19, 2014 4:29 am, edited 1 time in total.
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Re: Twin Spark Engines

Post by kevin » Sat Dec 28, 2013 8:14 am

Very interesting article . So you could technically see if you have ring flutter if you could measure your crank case pressure between 6000-7000rpm and see where it is highest to confirm your oil consumption is caused by this .
Also interesting is if your oil weight /type can lead to higher friction between ring and sleeve increasing ring flutter .
Are you gonna try steel rings now.?
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Re: Twin Spark Engines

Post by kterkkila » Sat Dec 28, 2013 11:53 am

Steel and even gapless rings has been tested already, so now it's time to try thinner rings. The bottom end with 1mm top rings has been run in already but it goes to next race season before getting real race results.

In theory the difference between the oils should be really small, as the forces caused by friction should not make much difference in general compared to forces from cylinder pressures and piston acceleration. Anyway great number of different oils have been also tested without success.

Measuring the blow-by have been in my mind for several times and I even tried it ones, but the instrument didn't like pulses coming from the crank case. That was a small hot wire flow meter. I realized only after the tests that of course it reads also the backward direction and ads that to output.. Mechanical device would be better I think.
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Re: Twin Spark Engines

Post by MD » Mon Dec 30, 2013 1:40 am

Kimmo,

I am probably not entering this discussion exactly in tune with what is going down apart from ultimate oil consumption. However in reference to crankcase pressure, after we ran in the new TS race motor in the first race car, it made a lot of crankcase pressure much to my surprise. Nevertheless, it did not have a major oil consumption with a rev limit at 7200.
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Re: Twin Spark Engines

Post by kevin » Mon Dec 30, 2013 3:25 pm

MD , I think oil consumption is relative to the type of racing . Ie if your car last two heats of 12 laps on a modern gp circuit that's ok as you can top up in between heats but if you're endurance racing then you got problems . In our racing I could live with excessive blow by on one of my motors due to the short sprint set ups .
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Re: Twin Spark Engines

Post by kterkkila » Fri Jan 03, 2014 1:02 pm

That's correct. Loosing 1 liter per 6h is same as loosing 0.16 liters per hour, or 0.04 liters per 15 minutes. And that's what I keep complaining :)

Edit: If revving all the time up to 7200 with an hot engine, my last setup would eat maybe 1 liter per hour. That would make 0.25 liters per 15 min, which can be seen already in dip stick.
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Re: Twin Spark Engines

Post by Mats » Sat Jan 04, 2014 3:39 am

I guess you need to fill fuel in 6h? Top up oil during fueling/driver change?
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Re: Twin Spark Engines

Post by kterkkila » Sat Jan 04, 2014 4:07 am

I have set the rev limiter to 6600 to avoid filling the oil during the race. Oil leven can be checked same time than filling the fuel tank and changing the driver, but if there's need to fill it, then we have to do that on team pit. Some tracks the team pits are just before or after specific fuel filling place, but at some tracks there's a long distance between.

So basically the oil consumption works as a rev limiter.
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Re: Twin Spark Engines

Post by kterkkila » Sun Jan 19, 2014 1:00 am

kterkkila wrote: After wondering a while and collecting some information:
http://alfatune.fi/cms_naytasivu.php?si ... anguage=en
I changed that page so that there will be also some project blogs and car specs. To start, I made one page about the old endurance racer and started blog from ongoing Tommi's project.
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