there is to much diference between 8.9 and9.0cr? im going to rebuild my engine and have to decide go with 8.8 cr or wait 2-5 weeks and 100us plus for 9.0 cr..

im going to use vortech v2 with 928 imperller and 2.87 pulley...

Dont know what to do...most people tell me go with 9.0 but 8.8 will be faster and cheaper.. they will be wiseco brand

 

8.8cr is too low for a Vortech. I did 9.5 final compression ratio in my build and others would recommend the same if you plan on staying with a Vortech.

 

^^ THIS ^^

Go with 9.5 as the lowest for a Vortech set up or it will feel 'doggy' down low... Having an install done right now at Dynosty and that is what I went with as well.

 

If E85 is an available option for you, I would stick around 10:1. For premium 91-93 gasoline only, I would go 9.5:1, or no lower than 9:1. You can always add meth injection if you run into some knock.

Most of the "shelf" pistons available are a bit overkill on lowering compression for modern engines like a VQ unless you are going for a world record.

 

thanks!!! here i have 91 octane gas but i can put some 100 octane gallons on the station...i think i will be in 375whp-400whp no more than that... i think 9.5:1 or 9:1 would be ok... my tuner said he prefere 9:1 to have a more safe tune... And i have long tube header that i think will lower the stress on the engine...

 

I'll play devils advocate here and say you won't see that much gain in it. If 15 ish hp/tq or less outside of boost is a big deal to you then yeah do it. If not, you'll be fine with the lower comp pistons.
I personally would run 8.8 as that gives you more room for det down the road; you probably will want to get a bigger blower like a ysi to make more power when you get used to the 928....
I don't understand why so many people on here want to make so much power and give up NONE of the factory like ness of the stock car; yet get surprised when the motor sh**'s its self... Jerry knows what I'm talking about.

 

that out-of-boost power loss compounds the further into boost you go. Ideally, you run the compression as high as you can get away with. It has big effects on the efficiency of the engine. Its more power per psi, better fuel economy, and increases peak power output potential of your fuel system, blower, etc.

Of course, if you dont know how far you will go down the road, you have to choose wisely. You dont want to start to high, cause its obviously not a weekend job to change your CR later. Tougher choice with a blower, when you cannot just adjust boost with the flick of a switch like turbo.

 

I agree with everything you said really... I just see upgrading for more boost as common place now a days.
If the cr was too low for you on this impeller you could always just get a smaller pulley (to push for more pressure). Worst case scenario it shouldn't be too hard to engineer something... ffs they're belts and wheels! Just as a mean time thing before you go bigger.
I know Church Auto just tuned a ysi 350z to make over 700whp. These things can make the power...

 

thanks resmarted!!! i will go 8.8 if i dont have enough power with 2.87 pulley i will jump to 2.75 to have more psi... maybe some day i get a good offer and do it TT, then i will need the lower cr... by the moment i will stay with vortech because its what i have on my hands...

 

Ras has good points BUT I would not go as low as 8.8 on a Vortech unless you plan on doing a Turbo down the road... That 700 was with a race YSI blower and those things are monsters! I searched ALOT before deciding on the 9.5... One guy who went with a 9.0 was not happy with the results from the get go...

Search Vortech in the titles of posts and read up on all the builds...

BUT... If you are seriously considering a Turbo set up down the road then the 8.8 may work for you and be safer...

Just be aware that she will feel a bit 'doggy' down low in the TQ band on a SC setup at 8.8...

 

FYI...that Church car was running 9.5 CR pistons on 91+meth or e85...and Church dynos run higher than dynojets...

 

It was 91+meth if I recall correctly to what Shawn said on the phone.

Still, the 9.5/9.0 setup will be fantastic for a smaller boost/standard vortech setup, but as soon as you step up to a bigger S/C or a turbo.... I'd feel nervous at least.

So OP, if you want more power in the future, if you even think you want more power I'd say go 8.8. If you really really want to stay with the vortech, and that's it (which who ever stays at one power level?! really!?!!) then go for the higher CR.

That being said 9.0 is pretty acceptable still in my book on a turbo car. Would make for a nice street build, but I personally chose 8.8 in my car.

EDIT:
If I were you, instead of spending $100 on upgraded CR, I'd figure out what max power level I'd want out of that engine, and decide on both the cylinder wall clearance AND if I want/need the upgraded wrist pins that wiseco has.

 

You gonna have Shawn tune your car?

 

Raises hand..... me, me, me, me, me...... (lol) I am totally staying w/ the Vortech and no more than the 928 / 2.87 set-up. I absolutely OVERBUILT my motor to get as much reliability out of this build as possible and make it last hopefully for 150K - 200K miles more to come...

I did say.... "Hopefully" ...

 

Looks like it. I refuse to go to GTM. Anyone else you'd recommend in cali for a haltech boosted Z?

 

Can Hal tune it via a remote log-in if you can rent a dyno to put it on?

.

 

Maybe. But I'd think there must be pretty serious limitations if you aren't actually there with the car. Not sure really.

I was considering flying him out. But as of now I don't think I can afford it; would have to drive to a big city, fly him out, get a hotel for him and likely myself (doubt I would be down to drive home at 4 am... maybe lol). Not to forget rent a dyno out... which could be pretty pricey.

With speed density, it wouldn't be too hard to get a nice safe tune working. Shawn sounds pretty competent with the haltech and sounded comfortable with setting up the car the way I wanted.

 

i will go with 8.8... i know maybe in 2 years i will want more power ansd will sell vortech and buy a TT.... Now my budget its for build, then it would be more boost... you have test your turbo?? i have the same headers that you have... what i can put to have a better down TQ since i have that header with nismo cat back... maybe i can put some magnaflow resonator or mufler in the Y??? i feel too much free flow...what you think??

 

Drive your Vortech with 8:8:1 compression on the streets in normal driving conditions and you'll probably want to change to a TT setup much sooner than 2 years. 8.8:1 will suck ***** for a street driven Vortech setup. Listen to the3kgt2, phunk2 (Charles@CJM), and Triji. I'd go with 8.8:1 only if you intend to go with a turbo setup sooner than later.

 

I have a Stock Motor with 10.3CR, and I run my Blower to 16-17psi on 93 octane with no problems. I really don't understand why people feel the need to Lower the CR when they Build. If it were a full out race car @ 35+psi I could see maybe dropping it to 9.5CR, but for a car that spends 90-95% of the time on the street 10-11CR works fine and with a mild cam the Dynamic CR will still be lower than stock.

I think some of the engine builders push the 8.8 or 9CR because it's an off the shelve part and they get a good deal on them.