For boost under 15psi wouldn't it be better to run 9.0:1 compression I am not sure how much difference it would make but with mid range boost numbers the higher compression might help you make some more power. Something to think about. I have the CJM kit and it is a nice kit and I have a buddy with an AAM one he likes it so if AAM is cheaper i would go with it.

 

Thats what I was thinking, but my mechanic said I should go for 8.5:1. If I brought him 9.0:1 he wouldn't say no, but I'm just going off his recommendations. You think it would make that much of a difference?

 

I don't know for sure how much difference it would make, if the builder wants 8.5:1 I would go with that or ask him why not 9.0:1. i think I might look into it more myself just for curiosity sake.

 

My first build I had 9.0.1 compression setup and I saw slight detonation on pump gas even at boost lower than 14psi. My builder recommended me to go to 8.5.1 and I trusted what he said and so far I am pushing 14-15psi with no issues.

 

I had 8.8:1 pistons and got over 600 whp (on a Mustang dyno, not a DJ) at 17.5 psi with 93 octane.

Alot depends on the tune, the supporting mods, the exhaust back pressure, etc., etc.

The pistons were ceramic coated, so that did help.

 

9:1 compression

22 psi and sometimes spikes up to 26ish

no knock


I love E85 !

 

^^^ show off! . I would also go with 8.5 if I were to do it again, but not really needed for the 530bb kit. The extra safety from detonation is well worth the trade off vs the 1-2% loss of power while off boost. Urban, you rebuilt motor. I have to find your thread...

 

^^^^

The compression ratio really should depend on the OPs goals. The build should be cohesive. With 9.0:1 compression, the OP will be able to max out the 530bb kit, even on pump gas. There really is no reason to go with any lower compression than that.

Now, if the OP thinks it is likely that he is going to want bigger turbos in the future and get up around the 600 whp range, the 8.8:1 pistons proved to work for me on pump gas. Per Japtrix, 600 whp on their Mustang dyno is equivalent to about 660 whp on a DJ. We did that on 93 octane and we had room to spare.

If the OP thinks that it is likely that he is going to want to get that particular motor up into the 700 whp range, then he should consider 8.5:1 compression. Even if he goes with 9.0:1, he can always use meth injection, though.

Now, let me be clear, will 8.5:1 compression make getting to 700 whp easier than 9.0:1? Yes it will, but the OP has not indicated that he is going to want to do that and there is no way the 530bb turbos will get him anywhere near that hp level.

Again, imo the build should be cohesive. Everything should be selected to optimize the manner in which they work together. If it were my build and I were going with the 530bb turbos, and I was planning on staying with those turbos for a long time, then I would go with 9.0:1 compression. If I thought I might be getting bigger turbos in the future, only then would I go with lower compression.

 

I went with the 8.8:1 coated Weisco's, Tomei rods (got a great deal) and JWT S1 cams/springs. The idle is fine and I daily drive my car.

 

The first build was never posted and that is becuase it was a package deal (bought turbo system and engine), I noticed a few issues like smoke from take off and slight detonation, later found out both turbo seals were bad and 91 octane pump gas sucks

My second build by GTM was posted and so far it has been great, pushing 520rwp at 16psi, trq is in the mid 500's

 

Thanks a lot for this info. I will be sticking with the 530s for quite sometime, and maybe do what rcdash has and upgrade at some point to the 700s. But that will be a long time. I'll probably go with 8.8 or 9.0. My goal is to hit 500whp but I fear that is pushing it and probably won't be happening with the 530s. If you were in my position would you go for 8.8 or 9.0?

 

I want to break 500 with the 530bb kit

 

What octane gas do you have?

Alot depends on the build. Like I indicated, I got over 600 whp with 8.8:1 on 93 octane. So, I asume 9.0:1 is probably good to north of 550 whp on 93 octane, and probably good north of 525 whp on 91 octane.

So, given your goals, and ignoring costs, I would lean toward 9.0:1, and maybe even higher if you have 93 octane available.

Now, you should look at costs. The difference between 9.0:1 and 8.8:1 is about 2%, so the performance differences will not be significant. When I built my first motor, Wiseco was the best value piston when comparing cost to quality, and for FI it was only available at 8.8:1. Other pistons of equivalent quality were much more expensive. So, I stuck with Wiseco. You need to look at your budget and determine what you are going to spend on pistons. If there is a 9.0:1 piston that is high quality and available within your budget, then that is what I recommend. If not, then look elsewhere.

 

We have 91 octane here in Vegas, no 93 . I will actually probably buy your rod/piston combo, and stay with 8.8:1. If you're going to use them or sell them let me know before you do

I was reading the Built motor + Osiris thread on my350z. I'm now considering doing Osiris instead of Haltech, it seems like it has better driveability by keeping the stock ECU. I'm guessing I would need the Osiris tuner package, but I'm still a little confused as to the whole thing works. I order the tuner package from them and then I need to buy the bigger MAF sensor too right? With what they give me, I can go to my tuner and have him tune it? This reflash stuff is new to me

 

I still have them, and I do not presently have them listed for sale, so they are still available.

For your build goals, I would go with Osiris. It is very cost effective and is turning out to be a very good option. About a week and a half ago I was at Japtrix and hanging out with Roger while he tuned a Subaru using the Cobb system (roughly equivalent to the Osiris from what I can tell), and I was impressed by the flexibility it had. Yes, the stand-alone EMS's have a lot of neat features, but the core of what you need seems to be available with the Osiris re-flash. Combine that with a good boost controller, and I think you will be in very good shape. Heck, the Osiris even gives you the capability to run multiple maps and change between the maps using your cruise control buttons (if you have that). That is really, really cool.

Moreover, if you go with an aggressive cam, you will want to re-flash anyway to get it to the idle smooth. When I did that, it costs me $500. To step up to the full Osiris, it's only few hundred dollars more. So, if you take into consideration the cost of the Haltech and the re-flash, you will be saving about $1800 by just using the Osiris.

EDIT: I think that the Haltech has boost control built in, so since you need an external boost control with Osiris, the cost savings will be less, depending on the cost of the boost controller you use.