Turbo NA build intake - suggestions?
 

Hey all,

I'm on a steep learning curve with some of the rotary technical stuff. I know it's been addressed in other posts, but what has been the best intake setup for a turbocharged NA S4? I've seen Aaron's method of port-matching a TII intake to the NA block but I've also heard of the FD intake used...

The reason I ask is because my intercooler ductwork runs to the driver's side, not the passenger side. So, either I have to change the intake or reroute the ductwork to the passenger side somehow, and that just doesn't seem as clean. Plus, the turbo intake looks a lot cleaner without the dynamic chamber.

Opinions? Suggestions?

Needs more information. Why are you using the NA block? What kind of turbo? What kind of porting? What is the purpose of the car?

Good question! So here's what I have in the works so far...

T76 turbo with cheapie CX Racing manifold
85cc primaries/1680cc secondaries
Microtech LT10S ECU
Aggressive streetport with 5th and 6th port actuators wired open

I'm going for 350rwhp or in that vicinity. More importantly, I want a car that's going to put a smile on my face when I put the hammer down, and still be streetable.

I'm using the NA block because I like the idea of the higher-compression rotors (9.4) combined with the tuning ability of the Microtech ECU. I have a new seal kit and a near complete S4 NA engine, so I have spare parts if I need. Other than that, it's because that's the engine the car came with. I'm working with that I got.

The car's purpose is simply a fun car to drive. I'm doing a widebody kit on it ('88 vert) and dressing it up nice for Sunday night cruising and maybe the occasional rip down the quarter mile. Nothing too crazy.

With that info in mind, what are your thoughts?

I'm confused. The point of the higher-compression rotors is to increase low-end performance and to run more motor and less boost for street/autocross type racing. Wiring-open the aux ports will kill this effect, and the T76 turbo is optimized for a completely opposite setup with low-compression rotors and high boost for drag racing.

It sounds like this is more the case, therefore you should just hook up the intake however it works and call it good. Your engine is totally mismatched, so there is no point in stressing over every little detail of the intake, as it would make very little difference anyway. It's going to be sluggish at the start, but once everything kicks-in I am sure it will bring a smile to your face as you hit ludicrous speed.

I do have two recommendations:
- Use a big air filter.
- Minimize the bends in the plumbing as much as possible.

Okay, now I'm starting to see things a little clearer. I was advised by the local RX7 'guru' that the turbo boost would screw with the port actuators, so might as well wire them open. He's a bit of a wingnut, so I'm inclined to trust your 9,000+ posts more...

And as for turbo sizing, same deal. I guess I should've learned more before buying the T76 turbo blindly based on his advice.

What would you suggest at this point? I'm not dumping huge money into the build but I'd like it to work rather well across the whole RPM range.

And thanks for your patience with a newbie. You probably would rather tell me I'm an idiot and that I have no business doing what I'm doing, but I already know that!!! :lol:

Turbocharged NA engine with port actuators right here, but I assume you have seen this already:
aaroncake.net - RX-7 Media

I'm a wingnut too, but I have owned RX-7s since 1988, and I have a pretty solid aerospace background that usually translates pretty well to cars. However, I am NOT a mechanic! Post-count is an indicator of activity rather than knowledge.

Can you return the turbo to the dealer and exchange it for a different model?

You could just leave it as-is in order to minimize the time and money you would spend on the car. Or, if you want to evaluate your other options, you could send a PM to Aaron Cake and ask him how he recommends controlling the aux ports when using a Microtech EMS. Just make sure you call it an engine and not a motor, otherwise he will get all bent out of shape. ;)

We once had a guy who asked for help with his engine because he installed one high-compression rotor and one low-compression rotor and it just wasn't running quite right. Do you still feel like an idiot now?

Mismatched rotor compression...is that a problem? :)

I'll touch base with Aaron about the port actuators, and thanks for the engine/motor tidbit.

I didn't break the bank with the turbo. I can probably source a new one easy enough. What would you suggest?

.." 85cc primaries/1680cc secondaries "

uh..(chuckle) I would at least UP those Primaries..by 1000%!!! (eight FIFTY!)

Busted!! I noticed the error but wasn't sure how to change it. Yes, 850cc injectors for primaries.

Thanks for pointing it out, Styx.

The T76 would work, but it would be rather laggy for your application. You would have a pretty easy time selling it to somebody who wants to drag race their RX-7.

For faster spool and better response you would be better off with a smaller turbo, preferably with a ball bearing cartridge if you can afford it. I recommend a water-cooled bearing, as it is my opinion that dry-bearing turbos are better suited for a museum of ancient history rather than mounting on a modern engine. Something like a GT35R or 60-series would work well. I recommend contacting Turblown (on this forum or at the website) and ask about options that would be suitable for your goals and budget. You don't want to just buy blindly on Ebay because rotary engines tend to need a larger A/R turbine housing than small piston engines (Honda, etc.) of the same airflow rate, so you really need to talk to a professional RX-7 shop to make sure your turbo has the optimal specifications.

Alright, things have changed up slightly. Or quite a bit.

I've picked up a set of turbo rotors, so now it's almost just a 13B turbo build. I'm getting a lot of varied information, so I'm wondering what your thoughts might be.

I still have the T76 turbo on hand. I have a lightweight flywheel and counterweight on the way. I'm removing all the emissions stuff. It looks pretty straightforward except I'm using NA irons still. Which leads me to porting...

I'm thinking of making one really large intake port on the advice of someone at Mazdatrix. Or, should I stick with a '6-port' streetport without the aux ports? Would it be a noticeable difference? And with the secondary ports done, what should I do with the primaries?

To clarify, my RX-7 (Project Tina) has non-functional aux ports. No actuators, wide open and bridged.

My Cosmo, which has not run yet of course, is built with functional actuators. To accomplish this I used a combination of GSL-SE lower intake (SE irons on Cosmo housings), custom middle intake, FD upper intake. A custom turbo manifold is necessary to keep the turbo from occupying the same space as the actuators. In the case of my Cosmo the turbo is a GT3076R, pretty small with the .82 T3 turbine housing. Designed for low end and midrange to suit the "luxury" nature of the Cosmo, drivable by anyone. Controlling with an MS3-Pro.

To the OP, if you are going to use what you have, then I'd suggest the following:

Don't port anything. The 6 port end irons have huge port area already.

Use the TII lower and upper intake manifold. Port match to the 6 port irons.

Without knowing what "T76" turbo you have it's hard to say much more regarding turbo size, boost levels, power levels.

I've elicited a response from the rotary god, Lord Aaron! I bow on bended knee!

Thanks for chipping in. It's a CXRacing turbo (I know, not exactly high-end, but it's what I have). It's a 1.15 A/R so I'm pretty sure I'll have a ton of lag.

As for the porting, I'm guessing I should still go in and clean up all the runners while I'm port matching?

Yes, that turbo is going to be very laggy especially combined with the large port area of the 6 port irons. You're really looking at a powerband from 4.5K up.

The port matching is done on the intake manifold side. If you have the engine apart anyway then certainly there is casting flash on the aux port runners that can be cleaned up however you really won't see much of a gain.

On the exhaust, an appropriate template to use would be the Racing Beat street turbo template. It opens the exhaust port a bit earlier which will help with that turbo response.