A real tuning question.. (engine blocks)

In news:3ryGf.37754$ snipped-for-privacy@newsfe6-win.ntli.net, Ed wrote something quite bizarre, possibly in an effort to confuddle the world. It went like so;

Wills rings and a composite HG should cure the head / block problems, my Cossie ran a ringed block with a GpA HG and it also had the head bolts replaced with studs, and the head machined to take nuts + captive washers with a pretty big surface area to spread the torque further around the head.

34psi of boost and it never popped a gasket.

As for the thinness of the walls... go for it...

Ive goto say I'm tempted. It will make what is possibly the most powerfull Micra engine powered Micra on the planet... I just know that the 930cc engine is very tough, and I dont know this of the 1235cc engine, and I cant afford really to waste a set of rods and pistons trying to find this out :) I think perhaps I shall stick a totally standard 1.2 bottom end on the low comp turbo head and see what happens to try and get an idea, (bet I can blow that pretty quickly tho ;) haha!

Ed

I should add that the 1.2 is known for its weaker head gaskets even in NA form.. Although some do use them very sucessfully for grass track racing now, and dont seem to have a problem...

If each cylinder radius is 2.5mm bigger, won't the walls be 5mm thinner?

no!

OK, I was assuming the cylinders would still be centred on the same points relative to the overall block.

No your maths is wrong!

If you do a 5mm overbore (thats your 2.5mm radius) then the walls are obviously 2.5mm thinner!

But which walls? The wall between two cylinders will be 5mm thinner. Or the liners will be 5mm closer. Or something like that.

Which is what I suspect Grant was getting at.

cheers, clive

*ding*

Well the liners will not be moving, and they are round yes? So its still 2.5mm thinner wall on every liner.

Which shouldnt be an issue really???

???

What's a typical liner wall thickness? 7mm or so? 2.5mm thinner on that is significant.

At this point I will bow out to those with knowledge of overboring engines - how much overengineered are liners?

cheers, clive

I cant see it being even a small problem. I have run big bored bike engines making 300+ at 30 psi boost with alloy (air cooled) blocks, and thin liners! Everything else failed at one time or another while drag racing but the liners never did! The only thing that causes problems with distortion is heat, but unless you run it lean, or too advanced for the boost level causing daft peak cylinder pressures unnesassarily then it should be fine.

The bike had 100 of Nitrous on top as well... Thats over 400 bhp per litre. Liners are the last thing you need worry about regardless of the opinions of "tuners" that are selling you stuff. What you are after is high AVERAGE cylinder pressures. Not damaging super high peak pressures. That rout causes big ends, gaskets, pistons to fail and causes early detonation due to the fast pressure rise due to early ignition. Run the timing a bit later than is best for peak power, and a bit richer too. And just use more boost to compensate. That way you get less engine heat/peak pressures / detonation probs, and potentially more power as more boost can be used before engine failure.

They are pretty much overengineered. It will only cause problems if peak cylinder pressures are too high caused by too much timing on boost. See post 2! I just wrote a small book!

Bah! is that all? ;-)

I cant see how much that one made? About 400? But its a higher reving motor (less pressure/torque) and water cooled. So its stressing the liners less.

But also remember that I was talking about my street/drag bike, and we never measured it with the nitrous on! And I used to build and own mobile bike dynos like that one, and have tested bikes (on petrol) up to 450nhp, and some methanol / nitrous/ bikes at 550 plus! And we tried a fueler once! Never again! My eyes still sting and it just kept wheelspinning... I have had much dealings with stupidly powerful bike engines and daft speeds/acceleration!

Is a pic of one of mine (dyno trailer), this is bruntingthorpe while testing for Perf bikes mag. This is one fast straight! The bike on the dyno only did 174 through the timing lights and made 120bhp if your interested.. Almost stock 750 motor in a modded yam GTS hub centre steered shassis thingy.

>

About 700bhp

Nearly as much as your mate's Altea then? (c:

> >

Mad! So the stupidly engineered steel liners in a car motor should absolutely piss it!

I was hoping to have some feedback from you! Great ok. I can keep control of everything else, I was considering ringing the block but I have a feeling this will also not be needed, and a true block and head with copper headgasket I hope will be fine.. I shall start planning this. :) hehehe.. Oh burgerman I have a highpower kit on the way soon as well....

Ed