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Toymods Board Member
I supported Toymods
Location:
Turramurra, Sydney.
Registered:
May 2002
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C/R for turbo. What would you do?
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Tue, 06 January 2004 09:17
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Alright, with my new motor, because the block & head have been machined, using the standard 1.25mm toyota 4A-GZE head gasket would result in a C/R of 9.5 or so, which I reckon will be a bit too much. I need a 1.8mm HG to maintain the standard 8.9 C/R, but as you could bet, 1.8mm is pretty hard to come buy, except in copper, which I don't really want to use (but let's not go into).
So anyway HKS have a 1.6mm or a 2mm, which would result in C/Rs of 9:1 or 8.7:1, (or 9.04:1 or 8.73:1 to be a little more exact).
I know it's only a small difference, and I know it's not gonna be the difference between 100 & 200hp, but I'd like to know, just out of interest, what other people would choose if they had too.
Also the turbo is an HKS GT2510, so it's small & shouldn't have much lag, plus it's suited to higher boost, so there's 2 good reasons for the lower C/R.
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Location:
Sydney
Registered:
May 2002
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Toymods Board Member
I supported Toymods
Location:
Turramurra, Sydney.
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 09:25
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It's also running an aftermarket ECU, so fuel & ignition are both adjustable, and I do & only will use 98ron fuel.
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Location:
Sydney
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 09:35
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OK well my idea was the RON being the variable that u can use to control pinging
so it turns out that boost is gonna be the only variable....(seeing as though 98 RON is the highest u can conveniently get)....that i can think of..
so lower C/R up the boost
or higher C/R down the boost
1) also what i would do is hook up a knock sensor to an LED light....to help u to tune your boost levels for max boost without pinging
2) also what id do is ...seeing as though u have an aftermarket ECU....i dont know if this is an option....but if u could...hook it up so whenever pinging is picked up through the knock sensor...not only does it flash the LED....it retards ignition timing aswell
number 2 id do but shouldnt occur once youve already tuned it with number 1....however its just there for precautionary measures (bad batch of fuel etc...) cause ppl REALLY underestimate the consequences of pinging
Ta
Mani
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Location:
Lost in the K hole
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 09:39
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joel, remember that reducing compression ratio by putting in a thicker head gasket will blow open your squish clearance, and make things way more likely to detonate (the reverse of your attempt to try and reduce compression in the first place)...
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Location:
Sydney
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 09:46
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ed ive heard that useing 2 headgaskets is dodgy and can cause pinging due to the unsmooth line-up or something like that ?
how does a single thicker gasket endanger the combustion chaember ?
or is it a lengthy explanation ?
if so ill search it if its been covered
Thanx
Mani
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 09:54
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| manipulate wrote on Tue, 06 January 2004 17:46 |
how does a single thicker gasket endanger the combustion chaember?
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| ed_ma61 wrote on Tue, 06 January 2004 |
open your squish clearance, and make things way more likely to detonate
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Thats the main reason, if you have a search you will find it in a bit more detail but you may have to dig.
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Location:
Sydney
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 09:57
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"open your squish clearance"
if that means what i think it means i dont understand how that works ?
does "squish clearance" simply mean the clearance between piston and head ?
sorry to hijack Joel, if u want i can take it elsewhere, just say the word
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 10:02
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What sort of power level are you after? Is it going to be a street car?
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Toymods Board Member
I supported Toymods
Location:
Turramurra, Sydney.
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 11:09
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Ah, now that's one of the negatives of the lower C/R I forgot about. Good point.
The car's going to be a street car, & I'm chasing big power yet. 150rwkw would be a very good start, but going by similar setups (but not taking account of their C/Rs) it should put up with a bit more.
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 11:21
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I'd be inclined to use the 9:1 compression ratio. Stricly speaking from an outright power standpoint it will have less potential, but in a normal application with an efficient turbo like the one you're using it should be fine give proper intercooling.
Also remember than every psi of boost is equal to more power the higher the compression ratio is.
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Location:
Brisbane
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 11:41
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All modern turbo engines are moving towards higher compression ratios. Detonation is not a problem with good tuning, and the advantages are many: more power, better off-boost response, increased thermal efficiency (hence fuel economy), faster turbo spool-up, the list goes on! I'd go for the 9.0:1 option for sure.
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Location:
Sydney
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 12:19
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good tuning is always the real key.
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Location:
Melbourne
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 12:42
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My tickeled 7M will have a bit more compression, much nicer in a street car to be on boost quicker!
i'll be looking 9:1 (NA design pistons with some smoothing to pistons and head) with 14 psi run by the motec should'nt be an issue 
Maybe consider some water injection if your ecu can run it!
Allan
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Location:
Melbourne
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Tue, 06 January 2004 12:53
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| BigWorm wrote on Tue, 06 January 2004 20:17 |
Also the turbo is an HKS GT2510, so it's small & shouldn't have much lag, plus it's suited to higher boost, so there's 2 good reasons for the lower C/R.
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Remember also you will flow more air with higher compression and have a higher volumetric efficiency so that will alter your turbo calculations
Allan
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Location:
Perth
Registered:
September 2003
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Re: C/R for turbo. What would you do?
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Wed, 07 January 2004 04:07
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yeah i'm with Norbie on that too.
i always like to find middle ground, instead of an 8.0:1 and 20psi off-boost slug (but a ripper when it does come on!) i'd much rather a 9.0:1 and 12-14psi all round performer, nice to drive in traffic and still enough poke on and off boost. with good tuning and a good charge cooling i see no reason why that wouldn't be feasable.
i'm turbocharging my 1UZFE soon, and with good tuning i will be running 10.0:1 CR and 10psi of boost. i have heard of people running up to 20psi on the stock engine, but i don't think i want to be in the car when that kinda combo goes *pop*.
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Toymods Board Member
I supported Toymods
Location:
Turramurra, Sydney.
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Wed, 07 January 2004 07:58
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Yeah, I reckon I'll go the 1.6mm gasket, & the 9:1 C/R.
Thanks for helping me decide!
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I supported Toymods
Location:
Perth
Registered:
May 2002
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Re: C/R for turbo. What would you do?
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Wed, 07 January 2004 08:00
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Always a pleasure. 
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