Sorry if this has been covered previously but do the bolt spacings allow fitment of the later 370 and or even the earlier turbo plenums with twin throttle bodies onto a non turbo 2005 G35 DE.
It would appear from several tests I have seen, including using say LS1 type 90mm TBs that the intake is a serious issue in trying to drag Hp out of these engines.
Gaining 25 Hp by simply lifting off the top cover whilst mid dyno run says it all.
Ultimately going ITBs is the go but then there is a pile of work to arrange clean/cool air into
the 3 trumpets on each side, but having twin intakes makes a start in that direction at least.
Im building "proper " long tube headers with 3 steps into merge collectors for the out side of things, as the so called " test " pipes and short header tubes are a technical joke, so would like to have options on the other end.
cheers
Wayne

 

I can't say for sure but I doubt the plenums are a direct fit. Do you already know how you're going to wire up 2 TB's & MAF's?

 

Why not just buy some long tube headers.

 

On the long tube headers, rather than building your own (unless you're doing it for the enjoyment of having an awesome project, in which case carry on!), PPE's LTHs are pretty darn good. They're only a single step but they use a proper merge collector. I'm not sure how much better you'll be able to do with your design and it may or may not be worth the trouble. There's one other decent LTH option out there now that I can't remember off-hand, if I remember it later I'll post again (no, it's not OBX lol). There are also rumors floating around that a certain intake/exhaust savy former rocket scientist might be doing some testing with a new long tube design as well, although that's probably many months out.

Herrschaft is correct that with two throttle bodies come the requirements for two MAFs, but the new AEM Infinity provides dual throttle body control (and I'm sure dual MAF/MAP reading as well) so that's not an impossibility anymore, simply a very expensive add-on to get the tuning you need. But if you're doing a ballsy build you should have something that will let you tune it perfectly and the AEM's not a bad option from what I've been hearing so far. I would look into the measurements on the lower runners between the DE and HR engines. I believe they are pretty similar, in which case yes you could bolt up an HR upper onto the lower runners on your DE. Some modification is probably required but I'd start with the FSMs and get a look at whether or not they're visibly of similar design. I recall a guy trying this a while back and coming to the conclusion that it was physically possible, but it was not in his comfort level to have it tuned and running correctly if he got that far along so he scrapped it. But I am pretty sure it wasn't a mechanical / installation related reason for walking away.

Another option is to simply mod a larger throttle body. As you stated the GM 90ish (87mm if I remember right?) TB has been done. It's relatively close in surface area to the HR dual 60mm TB setup which is one of the things that really gives that engine a strong benefit over the DEs. Since you're already aware of it being done I'm sure you had a reason for the duals and I'd love to hear it. I won't argue against it either because if you can tune for it I think it'd be pretty slick.

 

Also if you find yourself in North Carolina any time soon and want to get a look at the PPEs let me know. Mine are off the car and probably will be for the next couple months until I finish my rebuild so it'd be easy enough to get a close look at them and see if there's anything in their design that will help you in making yours.

 

I like the thought of long tube headers but, don't they delete the cats. And, having to get your exhaust snuffed by the state every two years are so, won't that cause you to fail the inspection. As for the plenum it sounds good but how many extra horses would it provide on the DE engines. Also, why not just drop in a engine from a G37S.

 

Yes long tube headers delete the cat. If you live in California, or anywhere that requires a smog test, you won't pass it. If you live in one of the wonderful places that just looks for OBDII codes or safety inspections, you're generally in much better shape all around, because screw California, lol.

Look at what Nissan changed from the DE to Rev-up DE to HR and then you'll have a better answer of whether or not the extra horses are worth it. The biggest differences from 03 DE to HR are the exhaust cam timing (also found on the rev-up DE), some different coatings and the dual throttle bodies. There are more but for our purposes those are the ones that often overlooked. There's an old saying that an internal combustion engine is just a large air pump, and if you think of it in those terms it makes a hell of a lot of sense to increase the amount of air getting INTO the engine before you do anything else. Easy ways to get more air in? Larger single throttle body with larger (3.5-4") intake tube and MAF with a retune. NWP put together a really nice package to easily accomodate the 75mm TB used in the 09+ Maximas. If you want to creative there are options that we discussed above. But yes, it's worth it.

Last thing to think about is the history on this platform, particularly where the closed minded users on this forum are concerned. I'm going to go ahead and make some heads explode here but there's more to this platform than MREV, Spacer, HFC/Test Pipes. There's also a reason almost all aftermarket intake tubes fail to provide any significant improvement in power / performance (they're all the same size which means they aren't pushing anymore air through). And lastly on the intake side, no matter what plenum setup you're using you're going to be limited by what air is coming into it and what volume the plenum can hold (which goes back to OPs mention of opening the plenum and gaining power).

To your last questions - how many extra horses you'll get on a DE is the wrong way to look at it. Everyone wants to know how much power you'll get from mod #3. That's stupid. Sorry. Consider your entire build and pick parts that will work together in order to provide a solid end result. There are a lot of things that individually won't do much, but when working together do wonders. And why drop an HR engine and deal with the cost, ***-pain of wiring, and hassle for a barely better engine when you can make a couple changes and end up with a very similar starting point far cheaper?

 

Also if you live in CA, by the letter of the law, you're probably screwed with HFCs (most of them anyway, if not all) and definitely screwed with test pipes. So you should just move if you want power and want to stay legal, the OEM cats are the most restrictive portion of the exhaust.

 

I live in New Zealand so smog legislation is not part of our reality - yet.
My occupation is designing and building two stroke race pipes, with a little four stroke race stuff when I can be bothered or the customer has more money than sense.
I designed and built the parts for a PhD project that I was the supervisor of at a local uni that involved the full modelling and running of the old Formula Ford 1600 race car engine in the Fluent simulation code.
This produced easily the most powerful dyno combination of cam timing, and header design ever seen in the FF1600 community, it won the National title easily and the driver is now knocking on the F1 doors.
I have never seen a G35 type 3 step LTH design with merge collector, an exit nozzle and tapered secondary tube as eventually evolved from that small Ford project, so I am doing my own - even apart from the insane costs of getting Burns or likewise involved.
That setup will be going on the car anyhow and tuned with a local reflash.
The G37 3 step is for sure the best I have seen, but as it says, its a racing orientated design, and I want a street screamer kept under 7000, those headers would be just getting going at that rpm level.
The intake side will initially just be the usual spacer,Z tube and pod until I can collect the parts needed to go dual TB or ITB.
At that stage I will use a local ECU manufacturer called Link, that can handle easily dual TB, or as I would prefer, try driving the ITBs with the stock TB fly by wire stepper motor, though getting a cable working would be a very minor issue in a build like I am proposing.
A simple way to run dual TBs would be to drive one with a stock servo setup, and run a cable across to the other
But probably by then its worth going to a combination input with MAP to help get over the gulp factor issues with ITBs.
There are plenty of crashed dual intake cars around so If the turbo type dual setup actually fits, then that would eliminate the drama of having to build dual air boxes and cold air intakes as I would need to run ITBs on the street,so is part of the decision making process.
Sure a hair dryer is easy power,but ITBs are WAY sexyer to my twisted mind.

 

You'll be good either way based on what you said above, but take a look at the AEM Infinity before you settle on software. It's doable with the single TB servo and cabling, but it's far easier (and more accurate) with the electronic control. It's been done both ways, but the AEM's got a lot going for it. Same for ITBs, you could use one channel of control per bank and minimize cabling (it may have full control per cylinder, I do not know, haven't looked that deeply into it).

Keep us updated when you get working on it, in for results

 

I have just been given a LS1 TB to play with so as an interim I may have a go at grafting this on.
Having just fitted a spacer the first thing I noted was that the bend that went around the corner from the TB to the rear of the plenum would have to be completely replaced with a larger tube bend, and then nicely flared out before tig welding around an enlarged plenum entry hole.
No so hard really, but next question would be what air flow body to use.
Im not familiar with an LS1 but I assume it has a matching flow body that would be connected with straight tube as is the stock setup?

 

The bend is easier to work with on the 75s, there's enough material to port out to match but yes once you're at the 90 range you'll want to do exactly as you described. Air flow body = MAF? If so you'll be fine to use one of the VQ compatible aftermarket MAFs. You might be able to make a GM sensor work but that's more wiring than I'm comfortable with personally. The guys that have done it have just used sensors that are already plug and play with our harnesses but are able to read higher voltages (Uprev, AAM, etc. bunch of options I can't remember at the moment)