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Truenotch's BEAMS AE86 racecar discussion


Truenotch

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From what I've read, proper engine builders stay away from decking blocks or skimming heads by the amount required to bump the CR up by a point or so. I understand it can create a sub par combustion chamber shape and lead to some issues with swirl/mix etc. In an engine like the BEAMS I'd say Toyota (Yamaha) would have engineered it pretty well up top.

Are you doing pistons? What about some crazy sorts of high comp slipper pistons or something to get it doing nice things. Technology has come quite a long way recently with injector technology, not to mention ring and cylinder coatings you can now do quite cheaply to reduce losses and make things run more effeciently = more power.

Also regarding modern engines, Mazdas new range of petrol and diesel turbo engines are all 14:1 CR :lol: Unheard of! Very off topic though.

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12:1 comression is ALWAYS a good thing...but ue not a real man till you get it up round Diesel spec and run 27:1 compression!

Most modern diesels these days are running as low as 14:1 CR.

also with skimming 0.5mm off the block would you run into issues with the crown of the piston hitting the overlap of the head gasket if there is any? What about the valves, are the pockets in the crown deep enough for an extra 0.5mm? I would perhaps look at fitting a thinner head gasket if they are available or if you're not using one already.

Thats cos most modern diesels are turbo and require lower compression for reliability.

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Not going to break the bank on pistons. Everything has already been balanced and we're good to go apart from deciding on whether to deck the block.

The piston edge sits 1mm below the mating surface and Toda do a .3mm head gasket to bring the comp up to 12:1 (standard is .8mm) so I figure skimming .5mm should be safe. We won't know without trying it though. I considered buying a Toda from Simon/Surfab in CCH but nothingsfree snapped it up first :lol: .

Might just slap it back together and be happy with 11.5:1 instead.

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that would depend your piston/rod combo and intended revs. I would probably be inclined to leave it as the gain would pretty minimal in the grand scheme of things and you would be absolutely slutted if you destroyed an engine, they can sometimes go in a big way when it happens too!

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I'd rather skim the block than run a thinner head gasket.

Wouldnt be surprised if the toda one is just like factory but fewer layers of steel.

Would rather have better odds of sealing well, and ease of replacing with factory gasket if need be.

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  • 3 weeks later...

Nope. I've never had the cash or the motivation to take my car that far north, but I'd take a wild guess at around 1:17.

Horsepower is only a small piece of the puzzle man - my car has never been far above 115kw at the wheels but it manages to get the power to the ground and flick around corners.

Have you done any laps around Hampton before? It takes a while to really get the hang of driving a car on its limit.

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yeh, I should, according to last owners log book, His was aiming for 1:17 at Pokekohe. he only managed 1:23 tho.

I am guessing my car only have 90-100kw at the crank, so proabably 80-90kw at the wheels, which is really enough.

so Yeh, I will see what the car can do once I got chance to go to Hampton downs or pokekohe.

I have got semi slick tyres, But I really want to put road tyres on them see how the car handles once the limit is reached.

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