Do you guys running turbos lower the compression ratio on your max? What amount of boost can you run on the stock 10:1 (I think) compression ratio? If you do lower the C/R, how do you go about doing so?

 

Oh boy!

 

?? My question makes sense; I'm not sure I understand your response.

 

Some have, some have not

Quote:

What amount of boost can you run on the stock 10:1 (I think) compression ratio?

depends on alot of factors, mainly tuning.

Quote:

If you do lower the C/R, how do you go about doing so?

By changing parts in the engine.

 

Use different pistons or on other cars I've seen it done by raising the heads...

 

How about some useful information this time around?

Ok, how common is it?

"Tuning"... Hrm.. I'm going to assume you mean intake air temps (as a result of the cooling capacity of your intercooler) and fuel octane. There's a few other factors that might affect it (a different cam, for example, can increase/decrease effective compression ration), but assuming all-stock internals, what's a ballpark of how much boost someone can run?

Wow.. that's amazingly general. The guy who made this post might still be new to this, but that doesn't mean you need to treat him like an idiot. What parts? Off of the top of my head, I can think of swapping in dished pistons or utilizing a head shim.

 

All of his questions have been addressed before. Vague questions usually results in vague answers.

 

I'll try and not be vague...
I think a more valid question would be:
What amount of boost can you safely, reliably run on the stock 10:1 compression ratio?
As Jeff92se put it. Lots of factors, mainly tuning.
IMHO anything over 10-11 psi boost requires that you reduce the compression ratio to keep things safe and reliable for a daily driven car.

There are two ways to reduce your compression ratio.
Cheap alternative - Head Gasket Spacer or thicker replacement head gasket. This increases the height of the engine head, whereby reducing the effective compression inside the combustion chamber. A 0.050" spacer will reduce CR by 1 giving you 9:1 compression ratio...ideal for boost. Talk to "TILLEYS99". I believe he had tried this.

Better Alternative - Engine rebuild.
9:1 CR pistons, valve springs and rings from a VQ30DET motor. These drop right in our regular VQ30DE motor. You could buy these from Japanese engine importers or from Jim Wolf. The only one I know with this setup is "i30krab".

As a side note: You will have to look at fuel, MAF sensor and Throttle Body upgrades before you can reliably boost 14+ psi.

Good Luck

 

Addressed before, perhaps, but that doesn't mean the information is readily available. A quick search on "lowering compression ratio" and "lower compression ratio" doesn't yield any post clearly addressing this issue. Where I come from, vague questions usually result in requests for clarification.

 

 

I would reccomend standing back.

SuDZ

 

It's like Ragu, "it's in there". He should know what or specifcly "who" to look up for the engine building becuase there has been only a handfull who have posted their experiences with it.

Plus where I come from searching for the answer is much more valuable than just having someone spit it out. I mean really, do you think these types of complicated and potentially dangerous questions can be answered in the scope of a few posts? Question 2 could fill hundreds of pages depending on how detailed you want to get. From what mechanical knowledge standpoint is he coming from? Would he actually understand the answers if someone actually took the time to answer completely? So for the 3 minutes it took for him to come up with these questions, I'm supposed to spend 20 minutes researching his past posts to see if he's knowledgable enough to understand replies that completely encompass his questions?

 

The VQ30DET turbo engine internals are not worth **** past 18psi daily driver. Don't go there. Custom pistons, rods, sleeved bottom end, built turbo head and intake collector is going to get you where you need to go.

I don't believe any of the other turbo guys because they don't have the dyno sheets nor the proof that when they mod runs reliably. I, on the other hand, am documenting my car every step of the way.

My plans is to make the first twin turbo 4th gen Maxima on the planet running 20 PSI daily driver, 30 PSI on track. Don't flame me just yet...the end product is due in only a month or so.

-A

 

Whoah.

 

I can't wait to see a 20psi maxima. Good luck.

 

Been there, done that!

More than a few times I did these 30 minute write-ups trying to explain rather complex topics on the honduh boards only to realize after the guy replied next that he was completely clueless and didn't have a freakin clue what I was even talking about. This one guy even freakin flamed me for making it seem complex. WELL IT IS!!!

So now I start off vague and if they seem to know what they're talking about I'll actually put some effort in

 

Wish you all the best on your twin turbo setup.
18 psi for a daily driver is more than enough for me...and it should be for most people. 18 psi equates to approx 500 crank HP!!

 

Thanks, I just a little sick and tired of hearing all these Honduhs and Acuras running high compression and turbo setups, and getting into the higher boost zones than we can. I'm interested, it's cool and all that, but what of Nissan products? So far, I've received two flame mails about how you CANNOT twin turbo a VQ30DE, but the last time I checked, the front and rear bank manifolds are indeedy SEPERATE.

After I get the setup running stable, I'm gonna crank it on the track and see how much boost she can run. Then I'm gonna test it again. And again. Then I'm gonna write to all these damned speed magazines and tell them to feature my car, a NISSAN MAXIMA, in one of their major stories. I am sick and tired of RSXs, Civics, Accords, Supras, even 240SXs getting the glory. Cmon, there has got to be some room for MAXIMAS!!!

-A

 

juss cause some people dont document everything doesnt mean its BS tho. I dont document ALOT of the things i do on my car because to me its a waste of time and i dont care to do that, but everyone that knows me knows im not BS. i did my setup over 2 years ago, when people found out bout it i got soooo many flames about lying and whatevers. It dont matter tho cause i knew it was for real and i didnt need to prove anything to anyone.

twinturbo Maxima will take alot of work but is not impossible. im not flaming you here, but i honestly believe that anyone wanting to twin turbo the Max is more into the "show" part. Good luck on all that and id be interested in hearing bout it when your done. Isnt Premier helping you with this? my friend that works for them metioned something like this.

 

Yes, Premier is working on this, I think you've been talking to Hoon.

Yeah, it probably is more for show purposes, but with so many turbo maximas flying around, why not run a twin turbo version? At least it'll be unique.

What I don't get is why everyone is so secretive when it comes to turbo manifolds, how to run their setup, etc. I'm glad to see group deals on turbo kits being offered, but many people fly blind because they lack info on what they CAN do, vs. what's out there. Sure, that's mostly THEIR responsibility, but after the hell I've been through, I'm going to be a "Maxima Consumer Advocate" and make sure my fellow Maxima owner gets all the info/experience that I've attained on how to turbo a Maxima. For whatever that's worth. Damn, sounds like I'm running for a political office or something...

-A

 

I'd vote for you...

 

So guys, avalon42, Turbo95Max, going back to reducing compression ratio, what are your experiences/suggestions.?

 

My suggestion is to get custom pistons/rods, because using a modified head gasket is NOT recommended. It helps out on TOP of using lower comp pistons and rods, but not just by itself.

For example, the VQ30DET uses a head gasket that is slightly thicker than our VQ30DE, but the compression ratio is 9:1. My pistons and rods will be 9:5 to 1, and I will be using the VQ30DET head gasket as well. A good intercooler helps out, as well as a good exhaust flow. You don't want heat trapped in there, I run 3" from the downpipe, but 2" for the exhaust inlets into the turbo.

Technically, it is possible to run boost on 10:1, but I'd dissuade you from doing so if you want any sort of reliability, especially for those of us who can't stay away from turning the boost up. turbo97se/nigel is making some serious hp #s by turning up the boost, but I don't think he is running that daily driver. I am up for the daily whoopa$$ turbo maxima, so I have to shell out the $.

-A

 

Ignition timing control is key in running high boost and high compression. "knocks on wood" I havent had any problems yet with 13-14psi on a stock internals. I use the J&S to retard timing and keep peak cylinder pressures down, by retarding the ignition timing so the combustion takes place later in the stroke and more combustion gas's are vented sooner. I only need a few degrees of retard at this point. Their is a point where timing retard will no longer work for this and lower CR is needed. 13-14psi is all I will ever get out of my V1 SC so I wont be lowering my CR anytime soon. But for 18psi or more, yea, lower CR sounds like a good idea to me.

 

Hehe twin turbos! I had the same idea. I have it planned out and it is indeed possible but it is not easy if you want to do it right. Too bad I don't have time to do it until January. The reason I want to do twins is not for show at all but for performance. The way I plan to do mine, you won't even be able to see them! Now you are doing twins, I guess I'll have to do quads!

By the way, I drive mine daily at 9.3 psi and it is plenty fun there! I have tried daily driving at 11 psi for a while but had problems hooking up the power to the ground. I think 11 psi is OK, but I would definitely get the larger injectors for more fuel.

As far as documentation is concerned, I think I have done my part there with dyno sheets. I don't want to waste my time documenting stuff when I can be enjoying my car. I have not had any time to go to the track this year. Now Bandimere is closed and I am not going to drive to Pueblo! If people ask me questions, I will answer unless they are just clearly wasting my time!