VR4 pistons compression ratio drivebility?

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Nosaki Faki
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VR4 pistons compression ratio drivebility?

Postby Nosaki Faki » Wed Mar 30, 2016 10:11 pm

OK, so I need to rebuild the engine.
I know putting VR4 pistons will drop the CR but will it really be noticeable in the driving?
Will also be changing the turbo from the tc06 to td05 with what I think is a small 16g wheel.
Running boost under the factory cut.
I think I would like a higher CR between 7.5 and 8:1 or will the turbo change make it responsive enough and I am just being pedantic?
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Re: VR4 pistons compression ratio drivebility?

Postby sucka » Thu Mar 31, 2016 11:02 am

Standard compression ratio of JA starion is 7.6:1. I may be wrong as I am relying on memory but I believe my calcs had vr4 pistons slightly below 7:1 under sohc starion head.You can use cast NA twin cam pistons under the sohc head which will maintain stock CR, but you will have to fly cut small reliefs as valve clearance is inadequate.
I replaced my old TC06 years ago with a TD05-big 16G (EVOiii) and it was a vast improvement over the TC06.

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Re: VR4 pistons compression ratio drivebility?

Postby Nosaki Faki » Thu Mar 31, 2016 7:20 pm

Yep that's about the same maths a I got. 7.1:1 It does seem pretty low.
would the improved spool up from the TD05 more than make up for the drop?
Good info on the NA ones as I was sort of looking down that road, but I'm guessing fly cutting will drive the cost up a fair bit.
I did find some pistons at 13.5cc I think they may have been EVO ones, would they be a viable option?
I am a fitter machinist by trade so modding the rod ends for 22mm pins is easy enough and free.
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Re: VR4 pistons compression ratio drivebility?

Postby redzone » Fri Apr 01, 2016 1:10 pm

The TC06 turbo has such a huge heavy exhaust wheel that it's pretty hard to find a turbo that's laggier imho. The TD05 will spool up so much quicker you won't notice the low comp. Orange car motor runs 6.4:1 with je vr4 forgies and a 4g64 head which has bigger chambers than the Starion head. It has a korean t3/t4 hybrid on it and the power shoots up at 2800 rpm, that's a full 1000rpm earlier than a stock JA.
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Re: VR4 pistons compression ratio drivebility?

Postby OLDIE » Sat Apr 02, 2016 11:19 am

Can/how far the 64 head be machined to raise the CR and not have the valves kiss the pistons and am guessing that an adj cam wheel will be needed to dial in the cam properly.
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Re: VR4 pistons compression ratio drivebility?

Postby quest » Sat Apr 02, 2016 3:02 pm

korean t3/t4 hybrid on it and the power shoots up at 2800 rpm, that's a full 1000rpm earlier than a stock JA

3800 rpm is really late spinup for a tiny stock turbo 2 valve motor

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Re: VR4 pistons compression ratio drivebility?

Postby Nosaki Faki » Mon Apr 04, 2016 5:42 pm

How about Wiseco forgies? https://www.horsepowerdirect.com/k559m8 ... stock-kit/
They appear to have quite a large lip around the outside edge I am a bit worried about valve clearance as a result .
Anybody used these? or know if there will be issues?
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Re: VR4 pistons compression ratio drivebility?

Postby Alspos » Tue Apr 05, 2016 8:47 am

Look like the ones I have in my other motor (that one day I will put in :( )
They have the fly cut in them, like VR4 and stock ones.
viewtopic.php?f=9&t=14756&start=146

Nosaki Faki
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Re: VR4 pistons compression ratio drivebility?

Postby Nosaki Faki » Thu Apr 07, 2016 8:30 pm

Thanks guys, I went with the Wiseco's, picked them up for $550 delivered with rings pretty happy with that.
Now for rods, can anybody give me a good reason not to buy Maxspeeding rods at $339 a set?
I know they will be made in china but I expect all of the big brands lower lines will be as well.
Scat's are about $450 eagle's are around $550, is there any point forking out the extra cash for these?
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Re: VR4 pistons compression ratio drivebility?

Postby quest » Thu Apr 07, 2016 11:15 pm

for your stated purpose, I would have ran stock n.a. dohc pistons (moded for valve clearance)..... on your oem rods
oem mitsu parts have proven very high quality. Some DSMs have put 3000 pound daily driven pigs to low 10sec on our shitty pump gas
Others gone 5,6,700 hp on their bone stock original 1990,91,92.. blocks. Incredible hardware imo
Too bad the sohc oem pistons are deemed "weak" tho. Seems wierd, seeing as how far the 2.6 folks have pushed their stock G54s

Nosaki Faki
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Re: VR4 pistons compression ratio drivebility?

Postby Nosaki Faki » Fri Apr 08, 2016 3:19 pm

Scratch that my order got cancelled for some reason, no Wiseco's :(
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Re: VR4 pistons compression ratio drivebility?

Postby sucka » Sat Apr 09, 2016 11:09 am

Nosaki Faki wrote:Scratch that my order got cancelled for some reason, no Wiseco's :(



try these guys https://www.built4g63.com/Wiseco-p1/

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Re: VR4 pistons compression ratio drivebility?

Postby redzone » Thu Apr 14, 2016 12:17 am

quest wrote:
korean t3/t4 hybrid on it and the power shoots up at 2800 rpm, that's a full 1000rpm earlier than a stock JA

3800 rpm is really late spinup for a tiny stock turbo 2 valve motor



Yep the TC06 is a dog.
Parts for sale (+freight), fibreglass airdams $370, fibreglass front bumpers $260, reco drag links $165, alloy radiators $925 (unpolished), all mechanical work from stock to performance builds.

PH Garage Redzone (07)54433507 3/5 Service st Maroochydore 4558



https://www.facebook.com/pages/Garage-R ... 3542662585



www.garageredzone.com.au

Nosaki Faki
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Re: VR4 pistons compression ratio drivebility?

Postby Nosaki Faki » Thu Apr 14, 2016 10:50 pm

still looking at other option as a few have popped up.
How necessary are the valve reliefs?
For instance hypothetically could I run a flat top with a standard cam and have no valve issues unless the timing belt broke?
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Re: VR4 pistons compression ratio drivebility?

Postby fugazi » Fri Apr 15, 2016 1:34 am

Take a look at the SOHC non-turbo pistons... do they have flat (-er) top w. reliefs?
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