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Discussion Starter #1
hey
im looking at getting some high CR forgies
CR is roughly 10:1
hoping to get the eventual CR to nomore than 10:1 with headwork, headgasket ect

i was wondering what you guys think about having compression this high with a turbo motor?
street tune will be on about 20lb with a swantko turbo (1.28rear) and the custom crane cams from SP, ive got a 60mm wastegate to help with boost creep if any
fuel will be a 50/50 mix of pump and toluene we have here in Australia
eventual octane rating will be between 105-110RON
race tune will be race fuel (VP, C16 ect) and alot more boost!

this is still a 3lt, not stroker

im not expecting full boost till around 5K or just after unless the higher octane brings spool down alot? and im running a 2spd glide with big stall (stall not selected yet)

ive been told that i just cant run as much timing like i could with lower compression and that i should get an ECU with knock control so once it sees detonation it will retard the timing ect

i realise this is a very high CR for a turbo motor but i beleive gone are the days that we have to run low CR on turbo motors now seeing as the quality of fuel is alot better

here in Australia we have a 98RON and 100RON at the pump and most people add toluene here in 30-50% for extra octane (adds roughly 1point per 5%)
like i said, ill be running a 50/50 mix for street and race fuel for strip ect

i have read that Fabio runs over 11:1 with over 40lb of boost and its going great
i realise he has a great tuner and runs on race fuel tho

would like opinions from people that run higher than normal compression on fuel around this octane

thanks in advance
regards
Troy
 

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Higher CR is not as much of a problem if you have 1) proper standalone, 2)a great tuner, and 3)enough octane to support your goals. The reason people would lower compression ratio in the old days, was lack of control over timing, fuel, etc. Now with the likes of AEM, Motec, etc, there are plenty of people that run higher CR than stock. Horsepowerfreaks E46 M3 is has a 11.5 stock CR and they are making in the high 600's on 15psi on just pump gas. My 3.4L that just got done has at least a 9.0 CR. It definitely can be done, but just know that you can't run 20deg of timing on pump gas, at 18psi.

Also, I am skeptic about your gas/toluene 50/50 mix. There are a couple of lengthy threads on this site where people used toluene/gas mix and took timing numbers with the stock ECU and it was not much better than pump. Instead of investing in toluene, I would get a $300 snowperformance Meth kit, and use that. I would run one of the following senarios with your setup:

1) Pump gas= No more than 16psi with very conservative timing.
2) Pump+meth 80/20 (meth/water) = 23 psi with improved timing.
3) C16 = Have your tuner dial this puppy in to the max without knock and back off a couple of degrees for safety.
 

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Discussion Starter #3
thanks for the info

people here in Aus seem to be able to put up2 8degrees more timing into there cars running toluene over straight pump fuel
most people pushing numbers are using toluene here in 30-50% with no ill effects and there making alot more power with the toluene then straight pump

so say that i had fuel in the car with a rating of 105ron, do you think it would be safe to run 20lb with the 10:1 compression?

as for ecu, ill most likely be running an Autronic sm2 or sm4 with knock detection
i did have a microtech but it doesnt have knock detection so im getting rid of it
also have a damn good tuner for the car aswel!

if i get the pistons then with the headwork ect and big boost on supreme nos i hope to crack the 1000rwhp mark on a DD dyno which we all know read lower than the DJ dynos

do you think the higher CR will change spool much at all?

this is a street car but wont be driven and flogged everyday
 

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1) Pump gas= No more than 16psi with very conservative timing.
2) Pump+meth 80/20 (meth/water) = 23 psi with improved timing.
3) C16 = Have your tuner dial this puppy in to the max without knock and back off a couple of degrees for safety.

What do you think of a 2JZ-GE with a TT headgasket? How much psi do you think I can run on #2 on the list with a Haltech EMS?

Im thinking of turbocharging my GE and i want to be in the 9.xx:1 CR. And I was thinking with a standalone, C16 or better, and a good tuner, I won't have any problem running my GT42 in its efficiency range.
 

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thanks for the info

people here in Aus seem to be able to put up2 8degrees more timing into there cars running toluene over straight pump fuel
most people pushing numbers are using toluene here in 30-50% with no ill effects and there making alot more power with the toluene then straight pump

so say that i had fuel in the car with a rating of 105ron, do you think it would be safe to run 20lb with the 10:1 compression?

as for ecu, ill most likely be running an Autronic sm2 or sm4 with knock detection
i did have a microtech but it doesnt have knock detection so im getting rid of it
also have a damn good tuner for the car aswel!

if i get the pistons then with the headwork ect and big boost on supreme nos i hope to crack the 1000rwhp mark on a DD dyno which we all know read lower than the DJ dynos

do you think the higher CR will change spool much at all?

this is a street car but wont be driven and flogged everyday
Its impossile to say what is safe with 10:1 or any CR unless your tuner dials it in. There are so many factors that can affect the overall situation. 20lbs in your car and 20lbs in my car are completely different. Anything from cams, FMIC, headwork, etc all can affect it. You just have to start low, slowly increase boost and timing and see where knock starts to be detected for your desired boost level and back off a couple of degrees of timing for safely.

The higher CR will affect spool tremendously, that is one of the main reasons for going with higher CR and also your off boost performance daily driving around town will be more pleasant.
 

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Discussion Starter #6
thanks again

your running the custom crane cams from SP arnt you?
ill be ordering a set of these soon aswell

i honestly think it will be fine running the fuel i mentioned with nomore than 20lb of boost with the high CR
once its all together with my headgasket, the CR may even dip into the high 9s but wont know until its together

ill talk to a few guys here in Aus aswell and see what they have to say

thanks
regards
Troy
 
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