Twin Spark Engines

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MD
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Re: Twin Spark Engines

Post by MD » Thu Feb 03, 2011 12:01 am

Are the muffler/s baffled or straight through?
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Re: Twin Spark Engines

Post by kterkkila » Thu Feb 03, 2011 3:09 am

Both indeed. First there was straight through type at the middle of the pipe and then baffled muffler at the rear end. Now I replaced the straight though muffler with terminator, but still there's some torque loss. I also tried to remove the rear end without big effect, but on that time I had the straight through type installed and no terminator.
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Re: Twin Spark Engines

Post by Maurizio » Thu Feb 03, 2011 3:31 am

The only way to really find out is measuring I guess.
Several pressure probes in the pipes along the system to see what happens.

btw :shock: i somewhat missed out on updates in this thread... what is all altered to get the latest results. Are you still using the intake variator on, what I somewhat filtered from your site, a 12.5 mm lift intake cam?
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Re: Twin Spark Engines

Post by kterkkila » Thu Feb 03, 2011 4:10 am

We have tried VVT with limited operation range few times, but haven't been able to gain any real benefits. It's useful to make smooth idle with cams retarded, and then set them back to right position when going. In theory it could been used to stretch some torque range, but we haven't used that possibility. If the operation would be reverse, like retarding when powered, then it would be so much easier to use. Other wise cam tuning is pain in the ass, it's hard to be sure how much room there is between the valves and piston.. We have tried a lot of different cams. At the moment there's 12mm lift on both, intake and exhaust.

Besides of cams, also piston design and compression ratio have been varied. Last year we had 12:1 compression and fast burn burning chamber. The results were quite good, but the engine was too knock sensitive. Here's the results.
http://jakita.com/pics/Tehokuva-10.jpg

Now I have reduced CR down to 11.7:1, and testing different exhaust setups. It's hard to get equivalent performance level to 2010 now.. It's relatively easy to get higher HP numbers, or even peak torque numbers, but the overall performance is harder to optimize. Let's see, let's see..
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Re: Twin Spark Engines

Post by MD » Fri Feb 04, 2011 3:45 am

I always have some problems interpreting your graphs but from what I can make out, it seems you are able to squeeze 44Nm more from your engine with 3o HP less than the Brick. How the hell did you do it?
Admittedly the torque spread is narrow which I imagine is what your problem is but still, well done.
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Re: Twin Spark Engines

Post by kterkkila » Fri Feb 04, 2011 8:33 am

I guess you looked wrong scale for the torque. Torque y-axis scale is on the right side of the picture. So if you compare that ca. 205Nm to Bricks value, I quess we're at the same ballbark. Yeah, I'd like to get that 200 Nm also at 500rpm lower engine speed, or ideally already at 3500rpm. But that would mean sacrificing quite a lot high rpm power.
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Re: Twin Spark Engines

Post by MD » Fri Dec 02, 2011 12:22 am

TS only.

Anybody have any information on good modifications to baffling in the oil sump?

Also good set ups for engine oil cooling.

Photos would be appreciated.

(JK, I am not talking about the photos you got stuck on the Kazzi ceilng) :D :D
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Re: Twin Spark Engines

Post by Jim K » Sat Dec 03, 2011 12:24 pm

You can configure your own baffle. The TS pan is a big empty space! Just leave enough room for the pickup to go through and enough holes for the oil to drain down. While you're at it, why don't you make a crank scraper? And why not check out P.Spruell's stuff? http://www.spruellmotorsport.com/select ... _2356.html
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Re: Twin Spark Engines

Post by 75evo » Sat Dec 03, 2011 2:22 pm

Johnson-Ishihara told me the have one for the 4-cyl as well, spoke to him personally last week.
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Re: Twin Spark Engines

Post by kterkkila » Sat May 26, 2012 10:36 pm

Here's some evidences how old TS performing against other brands:
http://mut-palvelu.fi/2012/endurance/en ... uloskt.pdf

That race was driven yesterday at full dry race circuit. As you can see, there was only one BMW and four VTEC Hondas in front of us. I have some ideas how to challenge those Hondas, but one problem on TS engine still exists and that is excessive oil consumption. The oil consumption was now kept in control by lowering rev limiter. The limit was set to 6700. With this compromising the the engine eat only one liter during the race which is the maximum allowable amount. If rising rev limiter to 6900, we need to refill on the race and that's bad for competitiveness. I'd like to rev it up to 7200 or even more, but then oil control is completely lost. I've tried to look answers for the happening but with no success.

So far I have tried different pistons, different ring sets, different liners (new and honed), spruell type scraper plate, closed and open engine breather and different oil types. But now I'm thinking if the reason would be on piston ring or liner resonances? Compression ring heights are std 1.5 & 1.5, so could their nominal frequencies cause the problem?

This oil consumption is a problem only on endurance type racing, thus it seems that Alfa racing community have not had a need to look for measures to correct this. I'm sure there's enough knowledge somewhere, but how can it be found is the hard part.. Anyone??
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Re: Twin Spark Engines

Post by Duk » Sun May 27, 2012 12:03 am

Have you considered a crank case vacuum pump with an oil air separator between the pump and crank case, that then drains back to the sump?
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Re: Twin Spark Engines

Post by kterkkila » Sun May 27, 2012 12:18 am

Vacuum pump could change operation of piston rings, but unfortunately rules won't allow those. Also dry sump cannot be used. All of the oil is escaping via exhaust, there's nothing on catch can. That's why the leakage must be via cylinders.
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Re: Twin Spark Engines

Post by Giuliettaevo2 » Sun May 27, 2012 12:31 am

or valves/guides... but i guess the head is in good shape also since you've rebuild the engine several times.

How about drilling little holes behind the pistonrings? They do this with the 16v engines over here that burn excessive oil. :wink:
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Re: Twin Spark Engines

Post by MD » Sun May 27, 2012 1:14 am

Kimmo,

This isn't going to help much but I remember the race engine in the Brick used to have a lot of crankcase pressure and the location of the oil filler cap on the cam cover was over challenged by the timing chain oil throw off. The combination of the two drove me nuts with oil over the engine. Relocating the oil filler position to the rear of the cam covers helped a lot and installing a baffled and larger oil catch can also helped.

I cannot agree that all TS engines are oil burners as our 12.5:1 CR engine was run to 7200 regularly and did not consume (burn) oil. Yes it did waste some as I have explained above but did not burn oil which I thought was unusual for an Alfa !

Admittedly we did not use it in endurance events so this is not a direct comparison.
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Re: Twin Spark Engines

Post by kevin » Sun May 27, 2012 10:57 am

The guys here had similar issues but solved it through changing oil type and weight . I'm not sure what they using but I know it was way to thin and ended up glazing the barrels in the beginning . Not much help here but might be your problem .
But then again you did 209 laps so is 1 litre oil bad consumption ?
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