Jump to content
HybridZ
Gollum

180 Degree L28ET Intake

Recommended Posts

First: This is posted here because so many other intake manifold threads are here. Should this section get renamed to Air/Fuel Delivery?

 

 

Ok, I've been kicking this idea around my head for a while now. This is my basic "sketch" I made to give a visual to what I'm going to say:

 

L28etIntake.jpg

 

I know this would have to be changed a bit to actually work, it's just a sketch. One of the most obvious things to me is there needs to be more straight material at the head so there's room for the manifold bolts.

 

 

One of the main reasons I even thought of this idea, was a way to get around complicated intercooler piping. With this design you avoid needing to feet two intercooler pipes through one side, or running the far side around tight bends to be between the radiator and valve cover.

 

I realize the runner length is insanely long, but I'm not sure that will really hurt performance THAT much. I myself don't plan on running a hot cam, or making power beyond 7k. In the long run I expect to still peak power aruond 5500-6k. This will be a street driven Z, and I don't want to ruin power at any RPM.

 

If I do make this I hope to make it for under $300. I'll be using aluminum solder with a propane torch , and getting aluminum craps if I can. My budget GOAL is actually $200, but $300 is more of the expected budget.

 

Another upside I was thinking about is that this gives you much easier access to the turbo, might also help keep the turbo a bit cooler giving it some extra space for air to move around.

 

So... advice? Suggestions? Should I leave X amount of runner exposed inside the plenum or make it a smooth transition?

Share this post


Link to post
Share on other sites

Yea, hood clearence would be tight to say the least... I've been considering a lower and farther back engine placement if I do this, wich really adds some cost.

 

$100+ for mounts

$100+ for driveshaft shortening

 

Those runners are.... 35mm? Lemme check... Yup, 35mm. Finding exact specs on the stock setup wasn't EASY. Though I didn't look too long I admit. At least I didn't start a thread asking for that info. ;)

 

The throttle is 60mm, and offset to the far side. I was thinking this should help eaven out the flow between cylinders a tad.

 

EDIT: I take that back. Mount's should be that expensive. Just need to find some scrap metal around and buy a case of beer for the welder friend :D

Share this post


Link to post
Share on other sites

Dunno how much you could lower the engine (like seriously, I don't know haha), but it seems like the oil pan to front crossmember clearance is pretty close... Would be a good excuse to make solid mounts though if it works out.

 

So you're going off of stock runner sizes, instead of increasing them for better flow? Just curious. Perhaps at the top section some of that oval flattened style tubing could be utilized.

 

Another (likely bad) idea would be to cut semicircle notches out of the valve cover, and weld the tubing into them, uniting the valve cover and intake but giving more clearance. Probably would add heat soak though.

Share this post


Link to post
Share on other sites

Oval tubing is more expensive and harder to find.

 

I'm honestly not sure how large the stock runner diameter is. Lemme see what I can dig up real quick.

 

I'm not going to be porting the head, so I'm not sure how much benefit there would be to increasing the runner diameter.

 

Oh, and from looking at JohnC's pictures of his race car there's plenty of room to go down and back.

Share this post


Link to post
Share on other sites

Looks like the runners on my 79 635csi. The bmw guys seem to prefer the later style manifolds for making more power. Probably due to the position of the throttle body. When they turbo this engine the best performers have the inlet manifols set up more like the traditional nissan one. I dont think you will gain much if anything. What you make up for in intercooling pipe you lose in manifold pipe and probably throttle responce.

 

Douglas

Share this post


Link to post
Share on other sites

Yea, I realize the overall length would be about the same. It's just a simpler/cleaner setup in my eyes.

 

I've also considered making my own manifold that just stays on the driver's side, just means getting an intercooler with the inlet and outlet on the same side, and figuring out how to fit them through the core support.

Share this post


Link to post
Share on other sites

I ran a Nissan Comp oil pan and was able to drop the engine 2" and move it back 4". Making that change requires a lot of other small changes:

 

1. Header clearance to the driver's floor pan.

2. Driver's side engine mount removal to get header in/out.

3. Center hood latch mount removed.

4. Shortened driveshaft.

5. Oil pump and/or balancer clearance over anti-roll bar.

6. Shifter hole clearance.

7. Modified/new engine and trans mounts.

8. Exhaust clearance to trans mount.

9. Cooling system hose changes.

10. Intake manifold/brake MC clearance.

Share this post


Link to post
Share on other sites
L28etIntake.jpg

 

I know this would have to be changed a bit to actually work, it's just a sketch. One of the most obvious things to me is there needs to be more straight material at the head so there's room for the manifold bolts.

 

The Mikuni-tyle ITB manifolds have virtually no room for bolts, either - you can always use studs instead.

 

 

One of the main reasons I even thought of this idea, was a way to get around complicated intercooler piping. With this design you avoid needing to feet two intercooler pipes through one side, or running the far side around tight bends to be between the radiator and valve cover.

 

It's an interesting thought - am I interpreting this correctly that the manifold plenum would actually be on the passenger side of the engine (US passengers, that is)?

If so, you are going to want to incorporate some sort of quick release mechanism so that you can still get to the valve cover for things like valve adjustments, etc. Take a look at Monzster's Wiggins clamp arrangement on his manifold for instance - there are some less expensive options you could use, such a v-band clamps.

 

I realize the runner length is insanely long, but I'm not sure that will really hurt performance THAT much. I myself don't plan on running a hot cam, or making power beyond 7k. In the long run I expect to still peak power aruond 5500-6k. This will be a street driven Z, and I don't want to ruin power at any RPM.

One thing you might consider - since you are going this far out of the box, it might be good to think about using a symmetrical plenum design to get more even flow distribution to the cylinders - think 5 liter Mustang manifolds. Also, didn't somebody just do something similar with a diesel manifold?

 

, and getting aluminum craps if I can.

 

Sounds painful :mrgreen:

 

Another upside I was thinking about is that this gives you much easier access to the turbo, might also help keep the turbo a bit cooler giving it some extra space for air to move around.

 

It would also give you less exposure to exhaust manifold heat - if you did the quick release thing above, you might

be able to get by with something trick like carbon fiber for the passenger side bits.

So... advice? Suggestions? Should I leave X amount of runner exposed inside the plenum or make it a smooth transition?

Monzter did a post in the early stages of his manifold development that looked into runner transition designs - that would be a good place to start.

Share this post


Link to post
Share on other sites

Thanks for the insight Tim!!!

 

I meant scraps... boy I got a good chuckle out of that this morning.

 

You've assumed correctly though. The plenum would be on the passanger (left hand drive) side of the vehicle, opposite side of the inlets.

 

I know the runner length LOOKS really long, but idealy the plenum would hug the valve cover really well to keep the distances short.

Share this post


Link to post
Share on other sites

Wow, I'd forgotten about that commercial. Man that's funny.

 

OTM - This will be turbo, so I'm not sure how much runner length affects power, other than throttle responce. And no I havn't calculated the helmholtz yet... Not even sure how honestly.

Share this post


Link to post
Share on other sites

Here's the plenum after some slight revisions. Shorter straight length, a bit more radius added.

 

L28etIntake003.jpg

 

 

I added the fuel rail for visual purposes, just to get an idea of what it'd look like.

 

I'm wondering what it would take to use a stock manifold as a base for this.... Would bring down costs. Wouldn't have to buy one of blake's flanges, or make my own.

 

The clamp idea seems pretty cool tim, but I'm wondering if I might end up with sealing issues if I go too cheap on them. That's a lot of clamps that will need to make pretty good seals.

Share this post


Link to post
Share on other sites

Kinda Reminds me of the P65 Nissan Intakes on JDM vehicles like the Leopard and Cedric. They were on both L20E and L28E's.

 

Runners wrapped around under the plenum, around the outside, and actually airflow entered the runner on the top or on the valve cover side of the plenum. Someone posted some photos here, I'm sure. There is a removable piece on the plenum.

Share this post


Link to post
Share on other sites
Kinda Reminds me of the P65 Nissan Intakes on JDM vehicles like the Leopard and Cedric. They were on both L20E and L28E's.

 

Runners wrapped around under the plenum, around the outside, and actually airflow entered the runner on the top or on the valve cover side of the plenum. Someone posted some photos here, I'm sure. There is a removable piece on the plenum.

 

Awesome, I found the pictures. I'm going to post them here as well. Thanks for the heads up tony. Some good reading in that thread.

 

p651.jpg

 

p652.jpg

 

It's a nice and compact little manifold. I'm amazed at how sharp those bends are though!

Share this post


Link to post
Share on other sites

Here's another mockup/new design. This is probably a bit closer in design to what would actually get built for these reasons:

 

1: Easier to work with assembling panels vs round plenum

 

2: Multi curve runners to keep the runners close to the valve cover without making contact.

 

My runner length is 29.0465, darn close to 2nd wave calculations for 5500rpm

 

1st bend is 4" radius, 2nd is 6" radius.

 

L28etIntake004.jpg

Share this post


Link to post
Share on other sites

A thought I had was to do just the oposite, make the turbo header go over the valve cover and keep the intake lower. This way the heat is rising away from the intake.

 

Of course, a custom intake would also be necessary. Not exactly sure if it would work, but was just a thought.

Share this post


Link to post
Share on other sites

That thought hadn't crossed my mind... sounds extremely complicated if you ask me. You'd end up with the manifolds crossing and things might get messy. Not much space to cross them.

 

If you're trying to move the turbo... you could move it to the wheel well... :D

 

I'm on a tight budget though, so a custom exhaust manifold hasn't been in the budget from the get go. As soon as I started learning about the torchable aluminum solder ideas started racing through my head....

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×