Lancia Integrale flywheel - max safe rev limit.

[Ozze]

Hi Guy

I'm currently building a new engine for my Dedra Integrale. You helped me out a while ago regarding compression ratio in the engine.

But here are my new questions.
1: How much is safe to rev the Integrale / Dedra 2000 turbo flywheels? I read in a post earlier that 7200 for cast iron fw is safe limit. But in your book, which is great, you say that the Integrale fw can be revved higher. How much higher?
2: For my own safety I'm thinking of building burst protection around the gearbox if or in case the fw feels like exploding. Have you done this to a Integrale gearbox or is it a total waste of time?


Regards from Sweden

[Guy Croft]

Ozze, hi

I do not know for sure what the Integrale FW is made of, cast iron or cast steel. It has the same low hardness (under 20 HRc) as the early TC and is probably - in my view just some close-grained cast iron.

Now I have never had a FW burst and although you are right to ask, the limit is more set by the rods - especially the OE bolt-only ones, I had hoped when I wrote about them in the GC manual that they would be a more survivable type than the early nut & bolt ones but later (post publishing) experience of racing them in short oval showed otherwise, ours broke at the neck (under the wrist-pin) quite quickly using 8000rpm limit, I mean within a few laps, whereas the older rods had lasted far longer in other GC engines in long circuit racing.

Metallurgy test which I will mention in the GC V/W in the new rod article will show that the samples of later rods we sent to the lab had inferior heat treatment, only partially hardened. I'm not saying that this is generally true (how could I know?) but it certainly shook me. The report also said they were both only equivalent to say, En8 mild steel, albeit forged and hardened and tempered.

So after that I said, well any OE rods - set lower limits and use race rods for high rpm, and in the case of OE rods I don't recommend any higher than 7200 these days. What people think and do then is up to them and yes, I know of people who have raced them far higher.

I have run the OE FW on 8v and 16v (bigger item) much higher than that but I am not assert the absolute safe speed. Racing doesn't work like that unfortunately. I Have run 8v and 16v FW to 7800, 8000 routinely. I know of higher figures too, far higher, accidental over-rev 16v Tipo eg: 9000 plus..

That said over 7500 I would certainly want to dowel to the crank, lighten the FW and have it carefully balanced with the crank by a proven expert. And I would not particularly want to run a heavy OE style clutch at very high speed either.

Flywheels most often burst from being too thin round the critical center region or out of balance (incl clutch). An out-of-balance pulls the heads off the FW bolts and the FW bursts as it goes thru the bellhousing. Would I be concerned about a well-balanced item and fit a protector? No.

Anyone who has experience to the contrary is welcome to comment.

GC

GC