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Discussion Starter · #1 ·
Alright guys I am planning for my build now in the summer and would like to discuss compression ratio's a bit.

The stock compression is 10.5 to 1, but with TT internals and TT head gasket it would be right around 8.3 to 1 which yields a very low power density (natural aspirated or out of boost)

Which lead me to options
1) TT internals with stock head gasket
2) Stock internal with a 1.2mm head gasket yielding 9.7 to 1 compression

What do you guys think I should do?
 

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Discussion Starter · #3 ·
I am trying to make between 330-350 it is not so much the power I am concerned with I do 90% of my driving in a vacuum situation and with a lower compression ratio the power density would be very low in those situations killing power and gas mileage
 

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Discussion Starter · #5 ·
I am making close to that power now about 300 whp my motor just has alot of miles so I am trying to decide whether I build it or but rebuild it (rings bearing etc)
 

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I see your delema, I like the OE compression and would hate the feeling of lower compression when daily driving and out of boost. Kind of like how the car feels on 87 I guess. I have seen guys with lower compression complain before, its just not all that common to see that here.

Maybe option one then, though I do not know what compression ratio that combo yields, just that it is lower. Then you are overbuilt for 350hp and can crank it up if you please, from time to time. I'm going for 350+'ish myself on the GE, will be using water/meth for the higher boost, I've had great experiences with my custom water/meth setup on my truck.

What is your EMS? If its the EMU or a standalone, you can advance timing a bit in the vacuum regions.
 

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Discussion Starter · #7 ·
Well I am running an Aem F/IC and it works great I removed my o2 to have full control of fuel in vacuum and boosted regions I am thing of maybe just a rebuild I would be oem rings, bearings and a complete gasket kit then just add a TT head gasket that is 1.2 mm thick and would yield a compression of about 9.3 -9.5 to 1 which would not kill my power density out of boost but also somewhat safer to prevent detonation, I would probably throw some head studs in that mix

My current setup right now is as follows
precision 60-1 .68 a/r front .70 rear
440cc injectors
AEM F/IC
27"X7"X2.5" intercooler
tial 50mm bov
tial 38mm wastegate
2.5" intercooler pipe hot and cold side
 

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i am 8.3/1 compression, and i tell you what. my car feels so slow without boost right now, but once i get above 3500rpm, my car feels just as strong, if not stronger than what it was when it was stock. now i am running a stage 3 cam, and ported polished, with intake, headers, and open exhaust, but thats just my opinion. if you are only going for 350 hp, get a smaller turbo that spools faster, and then you can be in boost quicker, therefore who cares what the compression ratio is then. i also just read that you have a 60-1, which should spool fairly quickly. you may try cams to increase the speed of the exhaust gasses coming out and spooling that turbo a bit quicker. good luck
 

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^^ I have a log manifold and early spool owns. For track/drag I'll probably desire a tubular, but for the street I love the spool up of my 60-1 w/ log mani.
 

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Discussion Starter · #10 ·
yea i have a tubular manifold now and the spool is somewhat quick I was thinking that with the money that I save without putting gte internals and what not I could speed on some cams or headwork but I am still really liking the idea of stock internals and tt headgasket
 

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i am 8.3/1 compression, and i tell you what. my car feels so slow without boost right now, but once i get above 3500rpm, my car feels just as strong, if not stronger than what it was when it was stock. now i am running a stage 3 cam, and ported polished, with intake, headers, and open exhaust, but thats just my opinion. if you are only going for 350 hp, get a smaller turbo that spools faster, and then you can be in boost quicker, therefore who cares what the compression ratio is then. i also just read that you have a 60-1, which should spool fairly quickly. you may try cams to increase the speed of the exhaust gasses coming out and spooling that turbo a bit quicker. good luck
A 60-1 is already a smaller turbo relative to the IS300 motor. I run TT internals and TT HG. Don't know what that yields though. Can't tell you how the car is out of boost yet, because it isn't tuned.
 

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IMO if I were opening the engine, it would get GTE internals, seems like a no brainier, very affordable, OE made, reliable. W/ the GE headgasket I suppose you might not even really notice a difference, except now your block will be a lot more forgiving to incidents like boost spikes, bad gas, tune variations, getting stupid with a boost controller etc.
 

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IMO if I were opening the engine, it would get GTE internals, seems like a no brainier, very affordable, OE made, reliable. W/ the GE headgasket I suppose you might not even really notice a difference, except now your block will be a lot more forgiving to incidents like boost spikes, bad gas, tune variations, getting stupid with a boost controller etc.
But then wouldn't the HG be the weak link? I would think you'd pop a gasket before you popped a piston.. At least the TT HG is a 3 layer steel gasket.
 

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It would be the weak link, but I do not recall reading of anyone blowing a gasket, it always seems to be the GE ring lands that crap out. Do not recal rods being an issue either, seems like it is the GE pistons that are teh suck. Anyone make an upgraded OE thickness head gasket?

Plus I'd rather be in the position of "crap, gotta change the head gasket" instead of "crap, gotta change internals, again, and maybe scored the cylinder wall."
 

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it is possible for when the HG goes that it allows the coolant to destroy the piston and/or cylinders. i would not say a HG is a safe weak link. i am however running TT internals with GE head gasket. i have been for 1 year @ 415HP. i do have an annoying itch that it might not be safe, but i wont be changing it this year. i'll be increasing the power to ~450hp for this year and maybe more on the dyno ~500hp for safe run. i'll report back if this fails :)


It would be the weak link, but I do not recall reading of anyone blowing a gasket, it always seems to be the GE ring lands that crap out. Do not recal rods being an issue either, seems like it is the GE pistons that are teh suck. Anyone make an upgraded OE thickness head gasket?

Plus I'd rather be in the position of "crap, gotta change the head gasket" instead of "crap, gotta change internals, again, and maybe scored the cylinder wall."
 

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Alright guys I am planning for my build now in the summer and would like to discuss compression ratio's a bit.

The stock compression is 10.5 to 1, but with TT internals and TT head gasket it would be right around 8.3 to 1 which yields a very low power density (natural aspirated or out of boost)

Which lead me to options
1) TT internals with stock head gasket
2) Stock internal with a 1.2mm head gasket yielding 9.7 to 1 compression

What do you guys think I should do?
Well I am running an Aem F/IC and it works great I removed my o2 to have full control of fuel in vacuum and boosted regions I am thing of maybe just a rebuild I would be oem rings, bearings and a complete gasket kit then just add a TT head gasket that is 1.2 mm thick and would yield a compression of about 9.3 -9.5 to 1 which would not kill my power density out of boost but also somewhat safer to prevent detonation, I would probably throw some head studs in that mix
there is all numbers wrong,
right numbers here
http://my.is/forums/attachments/f114/25756d1264432536-ge-build-question-cr.jpg
 

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Discussion Starter · #17 ·
Yea I am now agreeing with blacksport some of the others and looking at the chart that qphoton posted if I ran TT internals with OE headgakset would get 9.6 to 1 compression and that would have good power density
 
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