forged pistons recommendations

[MR2 Rich]

Best place I found for CP Pistons was these guys;

http://www.performanceunlimited.co.uk/

[MR2 Rich]

Happy with that - I just can't find 8.5:1 pistons!

I read a thread on here awhile ago that explained the way CP measure the CR is different to others. So the ones they list as 9.0 are actually 8.5 with the standard Toyota head gasket, assuming your head hasn't been skimmed.

Here's the link;

http://www.imoc.co.uk/forums/viewtopic. ... sion+ratio

[androo007]

Hi Rich,

Aha, super thanks. just gave them a call, £534 delivered. Will see if I can get lower than that.

I asked the CR and why they are 9.0:1 and not stock 8.5:1 ... he just answered that octane of fuel is higher than it was in the 90's and compression is rising in general now not the best answer eh?

[androo007]

When I was after Carrillo rods Jon was very helpful, Cambridge Motorsport Parts.

http://www.cambridgemotorsport.com/#_

[email protected]

Thanks ash, I'll give them a call now.

Thanks for all teh help guys... daunting to get it wrong!

Also, i was looking at using a Toyota HG - any reason i should use another? (HKS, Apexi etc?) If there isnt a significant reason i'll just stick with Toyboata

[Ryan S]

Thanks for all teh help guys... daunting to get it wrong!

Also, i was looking at using a Toyota HG - any reason i should use another? (HKS, Apexi etc?) If there isnt a significant reason i'll just stick with Toyboata

Hi Rich,

Aha, super thanks. just gave them a call, £534 delivered. Will see if I can get lower than that.

I asked the CR and why they are 9.0:1 and not stock 8.5:1 ... he just answered that octane of fuel is higher than it was in the 90's and compression is rising in general now not the best answer eh?

To be fair his answer is spot on People talking about low compression are basing things on fuel management from 1991 (or the 1970's if you're talking to Bob Hatton).

The gen4 Caldina 3SGTE uses a C/R of 9:1 and they engines take 1.2 bar (probably more in some cases) of boost all day long.

Stock Toyota gasket is more than up to the job it's also 1.4mm (1mm after compression). I'm using a stock gasket on my own build

[androo007]

I guess - but i'll be using the stock ECU for fuel management too.

One thought occurred to me last night - typically i'll end up in a year or two wanting to upgrade the blower. Assuming i want 400bhp, will just forged pistons & engine work be enough? I'm not looking to spend cash unless needed.....

Good news on the Toyota HG.

Compression wise, i'd much rather keep it safe..... i dont care about off boost power so if its safer to run lower compression I'm there

I gave the chaps a call at cambridge a call - they suggested that CP pistons arent as equipped for custom machining as JE PISTONS which are the main product they push and timelines a lot quicker for custom work.

I said i wanted a compression ratio of about 8.3:1 using a 1mm HG - so 8.5:1 pistons ... is that right? He is looking into prices for me.

Anyone have any thoughts on JE? Bad experiences or reputation? I only want to be paying for this once!!!!!

[Ryan S]

I guess - but i'll be using the stock ECU for fuel management too.

One thought occurred to me last night - typically i'll end up in a year or two wanting to upgrade the blower. Assuming i want 400bhp, will just forged pistons & engine work be enough? I'm not looking to spend cash unless needed.....

Good news on the Toyota HG.

Compression wise, i'd much rather keep it safe..... i dont care about off boost power so if its safer to run lower compression I'm there

Yeah as said at the start of the thread, if you're staying with stock management, In 99% of cases though people are forging for power which requires (in the case of toyota at least) aftermarket fuel management.

For 400bhp all you'll need after forging the block is injectors (side feed SARDs will do but hard to come by) ECU and a turbo

oh, and a clutch to cope with it all.

JE pistons are apparently quite noisy compared to most, that could be why they are a fair chunk cheaper. In my case I bought the best I could afford which in most opinions are Carrilo (which is what I went with) or Wiseco. I've no experience with JE personally so just going by word of mouth.

[MR2 Rich]

Hi Rich,

Aha, super thanks. just gave them a call, £534 delivered. Will see if I can get lower than that.

I asked the CR and why they are 9.0:1 and not stock 8.5:1 ... he just answered that octane of fuel is higher than it was in the 90's and compression is rising in general now not the best answer eh?

No worries. Look at the first post in this link;

http://www.imoc.co.uk/forums/viewtopic. ... sion+ratio

It explains why the CP are listed at 9.0 but it becomes 8.5 when Toyota standard head gasket is used.

[Odin_S]

Forgive my limited knowledge but Toyota's CP is only considered "really" safe at standard boost levels i.e. 13 psi/0.9 bar.

We get away with it at 1.2bar to a point on the standard turbo and ecu.
However putting a bigger turbo (bigger air maker) and keeping the CR around the same, isn't the possibility for detonation bigger than if the CR was lower?

Advances in fuel have been made but physics is still the same.

Feel free to shot me down

[MR2 Rich]

Forgive my limited knowledge but Toyota's CP is only considered "really" safe at standard boost levels i.e. 13 psi/0.9 bar.

We get away with it at 1.2bar to a point on the standard turbo and ecu.
However putting a bigger turbo (bigger air maker) and keeping the CR around the same, isn't the possibility for detonation bigger than if the CR was lower?

Advances in fuel have been made but physics is still the same.

Feel free to shot me down

Intake temperature, efficiency of the turbo you are using, mapping and ignition timing play a part as well..

[Ryan S]

The physics are the same. The fuel has changed in the sense that it takes more heat to make the fuel combust, therefore less chance of detonation.

[Odin_S]

Relying on the better fuel we have seems penny wise pound foolish to me.

I would putting as many fail-safes as i could to protect against my engine blowing up. Thats why i went with lower CR.

Anyway its good to get different perspectives on reaching a goal

[Ryan S]

Relying on the better fuel we have seems penny wise pound foolish to me.

I would putting as many fail-safes as i could to protect against my engine blowing up. Thats why i went with lower CR.

Anyway its good to get different perspectives on reaching a goal

That's almost like saying you don't fully belive it's petrol you're putting in the car! Could be orange juice in the tanks at the petrol station

[androo007]

Hi guys,

Thanks for all of the help getting to this stage.

So after ringing around, custom lower CR pistons from JE are circa £750….. too rich for me.

Given that I’m only going to be running the CB20 (for now) and likely never to want more than 400bhp in the future on a mid-sized turbo, I called my chosen builder who said that 8:5 will be absolutely fine, as long as I don’t want to shoot for really crazy high boost of 2 bar+ in the future.

He also said that its extremely rare to be able to drop in 86mm pistons as there is always some machining to do, and although I might get away with +.25mm, +.5 will guarantee a really nice bore and hone. On top of this he said that 86.5 is a completely comfortable bore and had no qualms about going for this….

SO…. On the basis of that, I’m going for CP Pistons, 86.5mm and a CR of 8.5:1.

Massively appreciate all the input so far – you guys are great. Good to see different opinions and options! Better get spending on the CC in secret…… and get packages delivered to work not home

One last thing to add to the list – main bearings and Rod bearings – recommended ACL, standard size.

Hopefully this will be useful for anyone else in the future looking to forge.

[craig]

Relying on the better fuel we have seems penny wise pound foolish to me.

I would putting as many fail-safes as i could to protect against my engine blowing up. Thats why i went with lower CR.

Anyway its good to get different perspectives on reaching a goal

That's almost like saying you don't fully belive it's petrol you're putting in the car! Could be orange juice in the tanks at the petrol station

It might as well be, if Tesco fuel is anything to go by lately.

[Ryan S]

haha, I know right, I use shell only normally, Tesco if I absolutely have to!

Glad you got it sorted matey, I wouldn't say 86mm is uncommon, I used 86mm in my own with a really nice hone. Anyone building a 3sgte will tell you the same, If you can get 86mm then go with 86mm. Taking metal away from the cylinders isn't brilliant regardless of power.

If I were you I'd get the block out, get the pistons out and measure up the cylinders. If you can't get 86mm pistons then go 86.5. In all honesty after doing my build I should have continued to use the car and forged another block (i did actually use another block but wanted my engine out sharp) then when that's ready just swap them over

[androo007]

It's a mr2 specialist doing the build - done a few so I trust what he said on that side.... I just don't want to end up getting the smaller ones then have the ballache of swapping later on.

Looked at getting another engine buy the costs are astronomical for shipping, buying etc and it's spare cash I can't sneak out. Plus it's a second car so doesn't matter if it's at the workshop for a month or two

[Ryan S]

It's a mr2 specialist doing the build - done a few so I trust what he said on that side.... I just don't want to end up getting the smaller ones then have the ballache of swapping later on.

Looked at getting another engine buy the costs are astronomical for shipping, buying etc and it's spare cash I can't sneak out. Plus it's a second car so doesn't matter if it's at the workshop for a month or two

Ach that's cool then man, The issue being that if you did (god forbid) score the cylinder wall or something then the block could end up useless having been bored out already. I wouldn't worry too much, Plenty cars running 86.5mm.

Have a look for bare blocks. I seen one in the UK recently, block and crank(already honed I believe) for £170

edit: block for £170 posted, no crank though.

http://www.ebay.co.uk/itm/Toyota-Celica ... Swu4BVy5gm

[androo007]

ohh really? Interesting........

[Ryan S]

ohh really? Interesting........

Trust me, the best advice I can give to anyone doing a forged build is to build up a seperate engine. It's VERY disheartening having the car off the road while the work gets done. It feels like you're never going to have it finished. Admittedly it's my own fault for taking on other project etc but it'd be a a lot better having a fully built engine ready to drop in/swap over than having the car off the road for any amount of time. I can't even remember how my car drives. Fastest thing I've drove (bikes aside) is my Volvo V70 which is quick but is it 300bhp Mr2 quick?? No idea!