Wiseco 8.3:1 or 9.0:1???

[spidy3]

wiseco 9.0:1 or 8.3:1 comp ratio?


current set up is in profile....

additions will be...

Scat rods
comp 1012 cams
fully ported head
manley springs & retainers
1mm oversized exhaust valves
removed balance shafts
AFC
pocketlogger
(want to run 22 psi on EvoIII)

Which is the more resonable/reliable compression ratio to go with for a daily driver / weekend track warrior???

need to decide this weekend, ordering parts monday

Dom

 

[JDNSBR]

Well I would say that choice is up to you. Both are going to be streetable. Where the 9:0:1 is going to give you a little quicker spool up the 8:3:1 you are going to be able to run a couple more PSI up top. Personally I would go with the 9:1 and stick with a quick spool. Both are very streetable though. You will be capable of 22psi on the 9:0:1 with the proper tune.

 

[GRITZ]

Im going to run 8:8 comp in my starion 4g63 swap...

 

[blackGSX2g]

I would go with the 9:1 pistons. I just got link tuned out alot better and am running my 50 trim at 25psi on pump (93) with no problems. I love the boost response and gas mileage. My last tank was 25-26mpg around town with mild-moderate boosting (and some tuning runs).

Be careful with your boost. You will need more fuel than others with lower compression running the same turbo, so plan your fuel system accordingly.

 

[tstkl]

also remember a mitsubishi 4 layer metal head gasket is thicker than stock, so it will decrease your compression ratio. what i plan on doing is buying the 9:1's and using that head gasket so it will be a little less than 9:1. my guess is it wouldnt be any less than 8.8:1, but its a somewhat noticeable drop apparently

 

[blackGSX2g]

also remember a mitsubishi 4 layer metal head gasket is thicker than stock, so it will decrease your compression ratio. what i plan on doing is buying the 9:1's and using that head gasket so it will be a little less than 9:1. my guess is it wouldnt be any less than 8.8:1, but its a somewhat noticeable drop apparently

That is a good point I forgot to mention. I ran with the stock headgasket and stock fuel system and it blew out at around 14psi at the track in 4th gear. The MLS gasket is a wise choice and should bring your compression down just a tad.

 

[Silverstrocker]

Ross 7.5:1....oh wait were talking Wiseco, i would go with the 8.8:1 that just me and my goals, you have to remember what your goal is, do you want to be able to run a great deal of boost or are you just building a mainly street car and you want more power but less amounts of boost, by that i mean you can run over 20 on either but it would be safer to get into the high psi numbers with a lower compression piston, hence why i went with my 7.5:1 ross

 

[spidy3]

Im looking for a quick street/track car. I figured if I went with 9.0:1 CR it would help out with spool since I will be adding high lift cams (Comp 1012) and that will slow spool down. So they will kind of cancel each other out in a way. Hoping that will help out for daily driving also.

Im also looking to get around 400awhp. I know I know, EvoIII 16g and 400awhp is pretty hard on 93 oct. I was also hoping that going with a higher compression it will let me keep my turbo and not have to upgrade to a larger one to run more boost. Since 22-24psi is close to top efficiency for the EvoIII on 93 oct. to my knowledge. (correct me if im wrong please)

Also are there any people running 9.0:1 CR and running say high 20s in psi on a 20g or a little bigger?

thanks for all replies

Dom

 

[spidy3]

Also...

Will I be hitting a ceiling for power if I go with 9.0:1?

Since I wont really be able to upgrade turbo. And since I have most bolt-ons already my next upgrades would be bigger turbo and supporting fuel mods.


Dom

 

[blackGSX2g]

Also are there any people running 9.0:1 CR and running say high 20s in psi on a 20g or a little bigger?

thanks for all replies

Dom

I run 25psi on a PTE 5031 with 9:1 compression. Before I got my external wastegate I would creep to about 30psi by redline.

 

[spidy3]

a 50trim is probably the biggest you would go with 9.0:1 CR right? Something like a GT30R or a little bigger wouldnt be safe to run on that high of a CR correct?


Dom

 

[GILZTSIAWD]

I am running scm61 with no problems and its alot bigger than your regular old 50 trim

 

[EclipseGST95]

if you run a higher compression you can make less boost and still make as much power as a lower crompression with higher boost and probably wont have as many problems cause the more boost you run the more parts that break

 

[tstkl]

so your saying a car with say, 0psi and a CR of like 16:1 would produce the same hp as a lower compression, higher psi set up, and will be reliable? gee, sounds like you should pass this info onto all the people with n/a cars. they dont need turbos, just insanely high compression ratios.

my point is that while it is "safer" to run a lower boost on a higher compression ratio and you will see similar performance, its not something that you can take the limit as x -> 0 (for you math and science junkies) of. It helps to have some more compression, but sacraficing compression for boost means more power, and if your engine is designed for that power and high pressure, it doesnt matter. a higher compression is just an easier way of getting the same power levels.

 

[Thomas91169]

id do the 9.1's if i wanted a car that had some pep around town under the transient boost spectrum.

lower compression are good for cars that are more track oriented, that are gonna run tons of boost(30+psi), and arent necessarily gonna see much if any daily driving.

evos run 9.1ish compression, and those guys run up to 28-30psi on the stock turbo with no issues regarding the pistons and CR. with 9.1's on a forged 4g63 rotating assembly and mls hg and arp studs, i see 25-28psi capible motor with long life given your ability to tune this setup right.

 

[spidy3]

Thanks for all the help guys

I decided on the 9.0:1 CR. thru all my posts I learned that you can run a higher boost (high 20's) with a higher CR, its just gives you a narrower space for error when it comes to tuning. That shouldnt be a problem tho since I am going to get it dynotuned once everything is together. I mean you cant get a new setup like Im doing and not get it dyno'd haha.


THANKS AGAIN!

Dom

 

[GILZTSIAWD]

Thanks for all the help guys

I decided on the 9.0:1 CR. thru all my posts I learned that you can run a higher boost (high 20's) with a higher CR, its just gives you a narrower space for error when it comes to tuning. That shouldnt be a problem tho since I am going to get it dynotuned once everything is together. I mean you cant get a new setup like Im doing and not get it dyno'd haha.


THANKS AGAIN!

Dom

I did But that is only because there is no dyno anywhere near here. Good luck with your setup and keep us updated on how it comes out!

 

[roni-wan]

would be a good idea to run about 23 psi plus nitrous on this 9.0:1 wiseco pistons?

 

[DarkstarTsi]

I'm also on the same dilemma regarding the CR on the pistons I'm about to buy. My car has the following fuel mods:
680cc fuel injectors
255lph fuel pump
TD05-20G turbo
What I want is a street car that will see the track once in a while. Correct me if I'm wrong in my understanding but if I go with a hif¡gher CR (Wiseco's 9:1) and lets say around 18-20PSI on pump gas I would actually get the same power levels as if I had let's say 8.5:1 CR and around 24-26psi boost???
Another question...which combination is more octane fuel dependant, high CR/low boost or low CR/high boost???
I'm about 80% certain I'll go for the 9:1 CR Wiseco's.........just need a thumbs up on that combo. Also, I'm not planning on changing my turbo for a while so that would also be a choice factor on my piston CR selection.

Thanx a lot for your replies.

 

[Bmxr152]

just remember your ging to have to do something with the timing otherwise your going to get alot of knock with all that more compression! I am learing that right now!

 

[90 GSX]

just remember your ging to have to do something with the timing otherwise your going to get alot of knock with all that more compression! I am learing that right now!

I'm surprised nobody mentioned this. To get rid of my knock with shitty CA 91 octane (probably lower, oil bastards) at 16 psi I needed a big ass front mount, full fuel system, and I had jeff at dsmchips burn me a chip with 2g timing maps on it. Now my car gets 19* timing max on the highest map and it rarely knocks. At that point you can use the cas to tune out any more knock, but only to a certain extent.

By the way, my mods are in the profile but if you don't want to look, I'm running 1g big rods with 2g pistons, coated, .020 over. It should be somewhere around 8.5:1 compression. Honestly if I were to do it again, considering I have 91 octane, I'd trade off compression for boost and use something around 7.5:1 to 8.0:1. IMO, 8.5:1 is too high to go past 20 psi (to get the bigger turbos into their efficiency range) unless you use alky injection or race gas. My friend has an evo3, stock 1g bottom end (7.8:1) and that car hauls ass at 16 psi with a supra smic and a stock fuel system with the same gas in my car. His duty cycle got close to 120% (holy shit!!!) and I never saw more than 4-6 counts of knock but usually 0.

Alcohol injection does amazing things... you will most likely need it running 9:1 compression on pump gas with lots of boost. I know julio at alkycontrol.com personally and helped him design his kit for the 4'th gen f-body. You should check it out, the progressive controller is sick.

 

[S Ladd]

personally if you had either a standalone or at least a nice dsmlink or AEM, I would chose the 9.0:1. If you are dealing with stock timing, I would go with 8.3:1. I have the 9.0:1 with stock timing, and I get a good bit of detonation on pump gas.

 

[DarkstarTsi]

I don't live in the US and the gas at the fuel pump we get has 3 octane levels. 90 octane, 95 octane and 97 octane (98 octane is coming out soon though). I don't have a standalone and I'm not planning on getting one in the near future, I'll stick to my Maf translator for now.
I currently run 18PSI of boost with my 20G setup, just 7-10 counts of knock at low rpm's and 0 knock during boost.
The timing issue kind of bothers me, do you think 97 octane gas will do the job if I go with the 9:1 CR Wisecos??? 8.3:1 Wisecos, 8.5:1 Ross or 8.8:1 Arias pistons are the other alternatives (although the Arias pistons are kindda expensive for my budget). Maybe I should start thinking about the 8.5:1 Ross pistons as my alternative???

 

[nightspeed87]

Compression isnt as great as you think for these cars, it just makes it harder to tune around and gives you less room for error.. I mean if your a hardcore tuner, then sure squeeze everything you can out of it, but for the average person, Id stay with the stock compression ratio, or just dont go higher than the 2g compression ratio ( if your a 1g ) 8:5.1.... Thats the highest Id go, ( thats what I have actually ) It seems more like the sweet spot on these cars. But it still presents a problem on stock 1g timing, so if you dont have link, or a dsmchip then your going to be screwed in tryuing to run even 12-14 lbs of boost on 2g compression ratio, so Id imagen 9:1 comp wouldnt allow you to run more than 10lbs on stock timing... ( Thats why I got chipped for my 8:5.1 comp 2g pistons )

A wiseman once told me that timing and boost are the biggest power adders in the mix, and compression is the least of the three... For example, 19 degrees of timing on 25 lbs of boost with 7:8.1 comp will more than likely net you more power than , 14 degrees of timing, with 9:5 compression ration, on 20 lbs of boost. ( If you could even get boost that high on a comp ratio like that, which has been done but isnt easy. )
Raising comp a few points is like going from a 11.5 a/f ratio ( which still provides a safe zone and decent power gains, ) to going to like a 12.1 open loop air fuel ratio which barely gets you any more power from doing it, and loosing that safe zone for adding more boost.... Not worth it.

Basically going any higher than 8:5 without crazy tuning measures/ devices is sacrificing too much boost and timing for a little more lousy compression...
Just my opinion...

 

[GVR4592]

I've tuned a bunch of higher(8.5:1-9:1) compression 4g63's and never had any problems running 20-25 psi on 92 octane. If you guys are having trouble with 8.5:1 and 20 psi, it's a tuning issue.

My friend has an evo3, stock 1g bottom end (7.8:1) and that car hauls ass at 16 psi with a supra smic and a stock fuel system with the same gas in my car. His duty cycle got close to 120% (holy shit!!!) and I never saw more than 4-6 counts of knock but usually 0.

Are you saying your friend has an Evo 3 car with a 1g bottom end in it? Or he has an Evo 3 bottom end in his DSM?