Detonation w10:1 Compression and QSC pistons

[flagoworld]

Yeah haha a few people are doing variable compression ratio. You can also do it by keeping the valves open longer during the compresssion stroke. 

 

But i did soecifically mean testing different pistons over a period of time. It would be a big task...

[TobyB]

Oh, gawd, it's valvetronic for your... bottom end?

 

Nah, I want poptop pistons or go home!

 

heh

 

t

 

[LarsAlpina]

I'd like to in some way support Toby's words.

 

First: Never understood, if the way octane measuring is standardized in US is comparable to like it is over here in Europe. That said most people over here (Germany) do run on SuperPlus what is said to have 98 octane. The ones with 10,5:1 and higher compression ratios do more often use Shell V-Power or Aral Ultimate which are said to have 100 or 102 octane. For additional info it seems much more common over here to keep the stock Solex 1bbl carbs than it seems to be in US - conversions to e.g. Weber DGV/DGAV are about unknown.

 

Now there wasn't just only one case I've heard of or seen in which the use of TI or tii pistons (9,5:1) in an otherwise stock (Solex 40PDSI, 0231180005 or earlier aequivalent dizzy) 2002 resulted in detonation issues. Mostly the solution is to put on a set of sidedrafts as EFI can cause problems with TUV in combination with the rules for number plates for historical cars (silly but true / standard number plates are possible, but meanwhile quite expensive for cars without catalytic converters over here).

 

Best regards, Lars.

[zinz]

On 5/20/2019 at 9:59 AM, TobyB said:

Smokey Yunik did things like that.  He was nuts.  And had no social life.

 

Wow.. that's a blast from the past.  I remember reading his stuff in Popular Science !!!

 

 

[aventari]

Thanks for the help everyone, I ended up going with these pistons: https://www.maximillianblog.com/blog/10-1-mahle-pistons-for-2002s

 

10:1 Mahle and I shaved the pop-up down 2mm.   Since the head is decked pretty far and the block was decked too, I went with the .3mm thicker headgasket too. According to my rough calculations I'm around 9.2-9.6 : 1 compression.

 

Motor is together I installed it and got it running on the weekend.

 

SO HAPPY

 

 

[aventari]

motor before install

[aventari]

Balanced them myself

[Dudeland]

Makes sense. That would be a fun thing to test ... stick a knock sensor on it and see how high compression you can go before it starts detonating at all

Where would one instal the knock sensor on an m10?



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[jimk]

Exhaust side above the engine mount.

[flagoworld]

Don’t quote me but i believe you can have it almost anyhwere on the block, probably better central, perhaps in one of the empty bolt holes. Then you reference its detection event with the piston thats firing to determine which cyl is pinging. So you need electronic ignition, and a computer, or it probably doesnt do much good anyways...

 

Edit: What jimk says, theres your empty bolt hole right there i guess

Edited August 15, 2019 by flagoworld

[Einspritz]

18 hours ago, Dudeland said:

Where would one instal the knock sensor on an m10?

 

I have mine on the intake side between Cyl 3-4. There is a casting boss, but you must drill and dead end tap.

[iinca]

98 to 102 OCTANE in Europe! WTF? I'd give up beer to put that in the tank

[aventari]

You could try a knock gauge

https://www.summitracing.com/parts/cei-102001

 

or google "det cans" if you want a super cheap, manual version. It's basically headphones attached to the motor.

[visionaut]

Yeah,  there’s a difference between Euro and US “octane” definitions.  See chart. 95 RON = 91 US

 

Oddly enough I myself am fancying a move up in compression beyond 10:1.

 

With the overlap on my Schrick 304, and running here at altitude (home is mile high), and I’m often as not out doing some canyon carving at twice that, I’ve been thinking I could run a bit more than my 9:5:1 Mahle grand pianos without detonation.  I’m always on the rich side, safely up there.  And higher comp might offset the power-robbing reduced available O2 up here.  (At 5K we’re down 15% , at 10K its a 30% loss vs sea level...)

 

On the locally available 91/93 octanes it seems like I could do 10.2 - 10.5.  But maybe not?

 

Though such a ‘mile high setup’ option might prove challenging should I venture back to the flatlands... In which case a Detonation sensor might be just the ticket (along with retarding or jetting).

 

Tom

Edited August 16, 2019 by visionaut

[Dudeland]

20 hours ago, Einspritz said:

 

I have mine on the intake side between Cyl 3-4. There is a casting boss, but you must drill and dead end tap.

 

Sorry, not to hijack but a picture would be greatly appreciated.   Please pm me. 

Edited August 16, 2019 by Dudeland