20V CQ Tidy Up

[Rusty]

What turbo are you going to run then? But mad to do all of this and fit a k24 7000

[Error404]

Yes and no! In the short term yes as I am not made of money, in the long term I want a torque monster so would like to be somewhere north of 650nm, without sacrificing too much driveability. To be fair I don't know much about turbos.
Plan was always to build a future-proof bottom end and then bolt-on from there.

Pat I have some LS2 coils and will be making my own custom loom for them so I can mount them where I want

[4WheelDrifter]

That is a good point, there was no information in with the pistons, so I will check with Wossner. The only info I have was what was on the box sticker. They are the 8.0:1 pistons

Wow. 8.0:1. Going for some big boost then.
I have to go to plan B to go as low as that.

Was that Philip in BDB? He insisted i measured mine before shipping for that very reason

Yes. It was.
I thought 7 thou didn't sound much, but Philip was horrified with the piece of scrap I had taken up to him. He said he was surprised the belts stayed on. But they did.

[Error404]

Hmmm, sounds like maybe I have gone a step too far with 8.0:1 for my application?
Boost & mapping ain't really my area of expertise, I'm a nuts & bolts man
Thoughts?

[4WheelDrifter]

Get a big turbo ordered.

[Error404]

not quote what I had in mind just yet

[djh]

not quote what I had in mind just yet

gt35 or 42 at least

[4WheelDrifter]

No worries, Alex. Your tuner will love you.

[G60Rallye]

Hmmm, sounds like maybe I have gone a step too far with 8.0:1 for my application?
Boost & mapping ain't really my area of expertise, I'm a nuts & bolts man
Thoughts?

Its a bit low for keeping it sensible on the turbo size. I would have gone for 8.5-9. Low compression means it can run more ignition timing but wont be as lively off boost.

[Thuppu]

Hmmm, sounds like maybe I have gone a step too far with 8.0:1 for my application?

Thoughts?

I wouldn't be too worried about the low compression. What fuel are you going to use? You can do much for the torque with cam timing also.

PS. Big Holset's are cheap compared to BB Garrett's. You maybe loose some minor turbo response, but then again you get a lot more reliability.

Boost & mapping ain't really my area of expertise, I'm a nuts & bolts man

I feel you are my soul mate.

[Error404]

Thomas I will be running normal 98/99 pump fuel so nothing special. Having had a chat to a couple people yesterday they have reassured me I shouldn't worry that the CR is low, it will just mean slightly higher fuel consumption which I'm not really concerned about. So that is good, just have to run more boost

I also spoke to P.E.C. about the Wossner skirt coatings and they confirmed that there should have been info in with the pistons to do with the coating - as suggested are measured before the coating is applied therefore it should be deducted from the measurements, so I will remeasure them later

[Pat D]

Do you know the dish volume and piston height Alex?

If the 8.0:1CR is calculated at zero deck, you may be able to bump that up to about 8.4:1CR by shaving the block down to bring the pistons above deck about by about 0.6mm. I would definitely do a cc check on the pistons if dish volume is not available, you'll then know exactly where you're at with CR.

I'm curious to know as those pistons look like they have a fairly deep dish. If the CR given by Wosner is calulated at zero deck, those pistons would need to have no more than approx 11cc's.

[Error404]

Cheers Pat, yeah I did quick calc yesterday and guessed at 11.4cc in the piston dish - I have bought a burette so I will work it all out correctly, and CC the head to be sure of the figures I have for that. The compression height on the Wossners is slightly higher than the OE pistons though, so I need to work out if I would need to machine the valve pockets slightly in order to take a smidge off the deck

[JariP]

I think Wossner states 12cc for the dish. I bought the same 8.0 cr pistons some time ago. I got them cheap, but after doing some math they weren't so cheap anymore.

I have a 0.4mm shaved block waiting for the pistons but that alone won't cut it. I'm not even sure if the pistons give 8.0 cr, they might even be something like 7.8. Heads can be shaved over 1mm before hitting the intake valve seats so there's some room to play with. Maybe 0.5mm off the heads, some more off the block and some shaving off the pistons to get the correct quench clearance. Or custom lenght rods and just some shaving off the pistons to get the cr to over 9.

[Error404]

Skimming both the piston and deck by the same amount would be the way to go IMHO as the piston dish would be reduced without affecting anything else. I'm not sure how far you can go before the valve pockets need to be enlarged. I'm not too keen on taking much off the head, as there is no opportunity to reuse it, once its been ported and extra decking colling machining etc has been done there is some £££ invested in it. Really need to CC the piston dish and get the exact deck height measured and go from there