Twin Spark Engines

Alfa Romeo ONLY please!
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Mats
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Post by Mats » Fri Jul 25, 2008 9:26 am

MD: Fiat/Lancia 16v engine, same block geometry as the old 8v Fiat mill that has been around since forever (Lampredi). Balance shafts on all 16v engines.
Sturdy engine and because of the Rally legend there are about a million after market suppliers. Head flows extremely well (in and out) so it's a good base for a hot build. This is the engine that was fitted in the 155 Supertouring cars (BTCC) but naturally almost everything was custom, most notably the reverse-flow head.

2l V6 with 24v heads? Something like that was available? Since when?
Or do you mean slap on a pair of 2.5 24v heads? usually there are issues with the valves being too close to the cylinder walls and combustion chambers being too large when using a "large head" on a smaller bore.
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Post by Micke » Fri Jul 25, 2008 12:21 pm

As we are extremely far off the TS topic and everybody to 99% just dreaming I tell you the ultimate formula is a 24V 2.5. Insert a destroked 2.0 crank.
Make it 54.8 mm for 1999.8 cc.
At a moderate 11krpm you have a mean piston speed of safe 20 m/s.
With an mean combustion pressure of 13.9 bar at 10500 rpm this would give 330 hp.
An all out racing engine could easily go to 13 krpm which would give way above 350 hp.

This would be easy to buid compared to the impossible 1750 2.0 liter engine which my friend made.

Now dream on :twisted:
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Post by Mats » Fri Jul 25, 2008 1:45 pm

Ah yes, piston speed is the only limitation... 8)
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Post by Greg Gordon » Fri Jul 25, 2008 4:35 pm

Well, I have almost no experience with the 24 valvers, but I seriously doubt you could prevent valve float at that RPM on a 12 valver, oh and there are some other things in the head that might break.

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Post by SydneyJules » Fri Jul 25, 2008 9:16 pm

Micke, as usual, you've stepped it into the next dimension! That does sound like terribly fun motor!

MD, if you want Lampredi info on what you can get going NA, contact Graham Smith of Fiatorque in Sydney- he's had a 300hp NA one on quad throttles do the rounds in Sport Sedans a few years back in a 131. Iron Block though. It was damn quick.
Fixing it bit by bit....
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Post by Micke » Fri Jul 25, 2008 10:05 pm

Valve float is not a real problem. The 12V design is. Just think how high the yanks rev their pushrod engines with 60 mm valves.

Mats is right that the piston speed is only one problem. This is mainly in the 4-banger of course.

A well prepared 24V 2.5 head should be able to flow >300 hp quite easily.
6 x 88 mm bore with 4 valves - if that doesn't flow, then what.

The next step of dreaming is a Montreal engine destroked and with billet 4V heads......
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Post by kterkkila » Fri Jul 25, 2008 11:33 pm

Destroking to make 2-liter with 88mm bore was also on my mind first, but then though that if head would work smaller bores, there could be compromise between 80mm and 88mm bores. I don't like the idea to regrind crank very much (small big ends and weakened crank), especially when it's about such a high speed engine. How big the bore should be to match with 2.5 heads? Would 84mm be enough? If so, there would be 4mm difference to 2.5, so it's only 2mm per side. Then the stroke would be 60mm, which only 6.2mm less than original 2.0 stroke. If the 2.5 heads could be matched with 2.0 bores as they are, that would be easiest and the bottom end would still be good for really high revs. If not trying to achieve DTM performance level, then this would be good option indeed.

If start messing with Lambredi engines, it's good to do extensive research on what can go wrong, and what must be taken into account. There's lot of tricks which are needed to do on those machines. I know some sad stories where guys have been continously destroying those engines, even when everything was tried to do as good as possible using expensive high quality parts.
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MD
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Post by MD » Sat Jul 26, 2008 1:32 am

Some great ideas there guys. Valve clearances are the probable stumbling block but destroking the crank is likely to give us more problems than gains perhaps. As I understand it, V6 engines inherently have a balance problem. I think if you left the bottom end original, it is less likely to be an issue and that issue at big revs would certainly be capable of self destruction big time.

I guess my next step is to get my hands on a 24v head and make some measurements..I could be a while :D
Transaxle Alfas Haul More Arse
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Post by GTV27 » Sat Jul 26, 2008 2:59 am

a 10,000rpm 2.0 V6 would sound sweet and make that little red box really boogey. :D
Jason
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Post by Zamani » Sat Jul 26, 2008 8:50 am

Can the guibos keep it together at 10K rpm?
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MD
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Post by MD » Sat Jul 26, 2008 3:09 pm

Who needs donuts for racing?
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GTV27
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Post by GTV27 » Sat Jul 26, 2008 9:48 pm

hmmm, doooooooonuts!

I'd look at using 2.0 litre ones (they are smaller and therefore less impacted by rotational forces) and inspect and replace them regularly (annually?).

The other alternative is re-engineering the propshaft for uni-s or something similar, but you'd have to be pretty certain the OEM stuff was going to fail before heading off down that particular garden path.
Jason
1983 GTV6 2.8 litre
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Barry
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Post by Barry » Sat Jul 26, 2008 11:48 pm

Dont you believe that...we exploded a std 20l donut yesterday on a n/a Nord at 7000 rpm..brand new donut it was as well..
French cars are shit and shit expensive to service and bloody awful and unreliable and expensive and friends don't let friends drive french cars and you wait years for parts.
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Post by GTV27 » Sun Jul 27, 2008 12:20 am

:shock: :? :oops: :roll: :lol:
maybe some donut cages might be a good addition also :D
Jason
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MD
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Post by MD » Sun Jul 27, 2008 2:30 am

Jason, my money would be on a composite one piece for this job. Serious bucks but it goes with the territory.
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