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Late last year I had a customer approach me who wanted a build done, his only request was: I want you to try new stuff and experiment. Music to my ears. Now, I have tried a LOT of stuff to get more pep and response from these sub-soda-bottle sized engines, but there is one thing I have wanted to try but knew it would have to be after I have sorted out everything else: The intake manifold.

On the MR16DDT, the intake manifold design really is not CRAZY important to make torque and power up top, as the air being ram-rodded into the engine by the turbo takes care of that. In fact, on MOST turbo cars you will see that the intake manifold has really been designed with packaging in mind, not efficiency. Most oe turbo cars have smaller turbos, or tricks to make the turbo spool up, so making the intake manifold match pulses and such really does not matter. In a NA car the intake manifold can make or break a torque curve. I am not going to go into all the science behind it, but lets just say Ferrari has resorted to variable length intake runners to try and increase the range of the torque curve because they do not want to add turbochargers to their car. Cool stuff, you should go read about it.

On the MR16DDT the intake runners are ALL different lengths. On a NA car this would be a killing blow to torque. As the air pulse in each cylinder would be different, meaning each cylinder would make more torque at separate times, making for a wave effect in the torque curve. As mentioned above, this is fine on the factory or even mamba turbos. They spool very very quick, so runner length does not matter. But. On big turbo cars, where you wont see peak boost until 3800-4500 (depending on the size turbo) this can lead to less than desirable low end torque.

Let me get this out of the way: I am in no way trying to make a 1.6L engine make 43768979347 ft lbs or torque before boost hits. I am trying to increase over-all responsiveness which in turn will help the turbo spool up quick and in turn make the power the car makes more efficient.

So, I told the customer I had an idea. BIG ADD INTAKE MANIFOLD. I knew it was going to be a LOT of hours doing the math and designing the cad files, so doing it one off seemed silly to me. So I hit up two other customers that are local to me, each with a different set up and asked if they wanted in. They said yes. To be clear: I didnt charge any of the three of them a dime in labor for this, and I am writing this after making the first manifold yesterday after 3 weeks playing around with how I was going to pull it off and waiting for additional laser cut pieces. It took me 9.5 hours to make the first one. Not counting CAD time and ordering. I SHOULD have that down to 6 hours for the next two, but still. its sucks lol. Long story short I charged them $600, including new blow off valves. I am now out $120 on each manifold because I changed the design.

So the plan: Biggest plenum I could fit in the bay to maximize on throttle response. Reduced plumbing by centralizing the vacuum ports to one area to make it easier to work on. As close to equal length runners as I could get to smooth out air delivery when off boost. Largest runners I could fit over the ports to again increase on throttle response. And finally: Avoid at all costs the silly SHARP 90* bend the oem throttle port does to get into the oem plenum. Based on fluid dynamics I had found online that people with way better computer programs than me had done, this is more than likely where MOST of the throttle response vanishes, as it slows down the air SO MUCH that you need boost to force it through efficiently.

At first I tried making them from aluminum. I pride myself on how well I can TIG aluminum and this was going to put me to the test. Lets just say i now know why manifolds are made from castings. It was impossible for me to weld some of the joints without making several more cuts and adding probably another 7 hours of welding to the project. SO the decision was made to switch to stainless.

Stainless presents its own issues: if you do not back purge when tig welding stainless and you use the appropriate amount of fill rod you get "sugaring" or contamination on the back of the weld. On an exhaust system this is not a big deal, as most performance exhausts are over-sized and this wont effect airflow at all, Injen exhausts for instance are not back purged, nor are most other tig welded exhausts. On an intake or IC piping this is not good. Small bits of the contaminated metal can break off, and end up in the engine. No good. Also, intake flow is more sensitive to imperfections. That's why porting a cylinder head on the intake side can produce a bit more torque. This manifold had to be made in stages and tacked together to avoid flexing during the welding process, so back purging was not a realistic option.

So what I did was this: I welded as much of it from the inside as i could so the sugaring would occur on the outside of the manifold, which I could make more aesthetically pleasing later. So I did this at the head flange, and at the plenum flange. I then used a die grinder with a carbide wheel to do and smooth out the ports, and a grinder to flatten the surfaces back out. Resulting is a relatively smooth area. On spots that I had to weld on the outside, I used extra thick piping, which costs more and weighs more, but if you use very thin fill rod and low heat, you can do a decently thick weld without fully penetrating the tubing, which prevents sugaring from occurring. Stainless welds hold up to pressure better than aluminum, so the welds dont need to be as thick to work in this case. I have pressurized this manifold to 35 psi already, and it held no problem. This main build is going to do near 400 horsepower, and will only need 20-25psi to do so on the turbo we are using so i know its good.

In progress photo:
188468


I also had to solve the gasket issue. As you may know, nissan uses inlaid rubber seals on the intake system, not a traditional gasket. So, I upgraded the cutting size of my CNC router, and now have the ability to cut my own custom gaskets in house. Makes life easier for sure. (On a side note I am working on making gaskets for the oem turbo inlet and outlet that arent that silly pressed steel crap that always leaks and replacing them with "Cork" gaskets that work better at repelling oil.)

So here it is all done aside from a polish:
188467


I did not have to extend the throttle wiring, but I will have to extend the MAP wiring for its new location.

Also: It only takes 3 minutes to take the manifold off. It is soooo much easier to work on a majority of the car now, since access to the starter, alternator, and main harness was blocked by the oem manifold.

I install the first one on a big turbo car next weekend, and will be doing a retune on it. I am not sure if we will get to a dyno right away, but I will get it on one eventually. The car I am doing the build on is several months away from being done as the machine shop is taking their time with the block. So even though the turbo system is done, the engine in this car is actually blown from what I believe was a bad tune by a certain e-tuner on a mamba turbo.
 

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Discussion Starter #3
The angled plenum really isn't needed because is is turbocharged. so the air will get in evenly. ALSO, the plenum length and TB tube are long enough where the volume of air coming into the plenum will evenly spread out. A plenum for a boosted car is a completely different set of rules than one that is NA (which that article above is for). If you look at the design of the intake plenums on most turbo true race cars, you will see volume is desired over air distribution, as throttle response is what is usually lost with big power on a small displacement engine, after your on throttle, boost takes care of getting the air into EVERYTHING lol

The runners are butted, but have been ground rounded into the runners, so itll flow good.

Again, just trying to increase throttle on response, so volume is the main contributor to that. and there is now a LOT of it haha
 

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I know you said you weren't going into the science of it, but I can't help and think that while the MR16DDT has a turbo, it's still drawing a vacuum off throttle or cruising. It's not like the engine sits in boost all the time. what I'm getting at is, does the engine just suffer while cruising and the intake is sitting at -6 inHg vacuum? Also, is that extremely brief period of time between WOT and full boost (turbo spool) so short the torque curve is unaffected on the low end? Would be great to see you get one of these for a stock intake vs fabbed intake dyno comparison. I've seen the plenum spacer debunked in a similar dyno test (proof a turbo car doesn't care about volume of the intake because it's literally ramming air down the throat of the engine).
 

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I would rather have a metal intake over plastick anyday. Haha but great question. I never would have thought about the low volume idle aspect of the Juke running. We are always thinking MOARH power.
 

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Here is one for a turbocharged engine. They also used Carbon Fiber wrapped 3D printed ABS to make it.

Here is an old high-boost Honda from the dominant MP4/4
188486

In general, when it really makes a difference and the air comes in from the side, they taper the plenum to even out the amount of air flowing into the different cylinders. If you have CFD that shows otherwise, I would love to see it. On the flip side, they have a lot of resources to make more complex shapes. The improvement involved may not be worth it here for the added complexity.

Most modern F1 cars do not let you see what is going on under the plenum cover. However, one big difference between F1 and a street car is that they do not need low end torque, hence the common use of short runners on velocity stacks.

But it is really cool that somebody is working on an intake. It will be interesting to see how far this could go with further optimization...
 

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Discussion Starter #7
I know you said you weren't going into the science of it, but I can't help and think that while the MR16DDT has a turbo, it's still drawing a vacuum off throttle or cruising. It's not like the engine sits in boost all the time. what I'm getting at is, does the engine just suffer while cruising and the intake is sitting at -6 inHg vacuum? Also, is that extremely brief period of time between WOT and full boost (turbo spool) so short the torque curve is unaffected on the low end? Would be great to see you get one of these for a stock intake vs fabbed intake dyno comparison. I've seen the plenum spacer debunked in a similar dyno test (proof a turbo car doesn't care about volume of the intake because it's literally ramming air down the throat of the engine).
When designing a performance intake manifold you very rarely consider cruising vacuum. You are interested in maximizing throttle response (with volume) and maximizing peak torque ability (runner smoothness and flow capability). OE's consider balancing the two as highway fuel economy is very important for emissions regulations and sales. All three cars this is being installed on have larger turbos, which have fantastic highway economy as a result, so I am not worried about that. As for the brief space between wot and boost, on a big turbo car thats not the case. Even at 5k rpm when you HIT it, there is still latency, not a lot but it is there. Again, this design is to help reduce that with more volume of air for increased response which can help the turbo spool faster.

This is NOT designed for an oem turbo. IF I where doing one for an oem turbo I would have made it VERY differently.

This is to maximize response and help the ability for the engine to make a bit more peak torque.


Here is one for a turbocharged engine. They also used Carbon Fiber wrapped 3D printed ABS to make it.

Here is an old high-boost Honda from the dominant MP4/4
View attachment 188486
In general, when it really makes a difference and the air comes in from the side, they taper the plenum to even out the amount of air flowing into the different cylinders. If you have CFD that shows otherwise, I would love to see it. On the flip side, they have a lot of resources to make more complex shapes. The improvement involved may not be worth it here for the added complexity.

Most modern F1 cars do not let you see what is going on under the plenum cover. However, one big difference between F1 and a street car is that they do not need low end torque, hence the common use of short runners on velocity stacks.

But it is really cool that somebody is working on an intake. It will be interesting to see how far this could go with further optimization...
Now your comparing an extremely high revving F1 engine making like 1000hp at 3957389756873 rpm to a design for a 400hp 4 cyl car that MAY see 7500-8000 rpm haha. When the plenum is large enough, it distributes air more evenly. If you notice on the RB26, that formula one engine, or even the oem mr16ddt plenum (which also has a taper): the plenum has to fit in a certain area with certain criteria, it is also fairly small compared to the displacement of the engine. As your previous article points out, you usually want the plenum to be larger that the displacement of the engine, if it is not, then you do not have the air volume in it to actually fill all of the cylinders, which is where you then need to start worrying about getting enough air to the cyl's further from the side of the plenum. And again, under boost, NONE of this really matters. The turbo is ramrodding air into all the cyls evenly. Usually you need to worry about plenum heat at the rear of the plenum in an engine racing the same direction as an rb or 2j, but on the MR the plenum gets plenty of air flow through the front of the car to where that wont be an issue. When I tune RB engines I have to add a TOUCH more fuel to the last 2 cyl's to avoid knock from increased combustion temps, but not all engines are the same.

I will get one of these three cars onto a dyno to compare with the oem unit. With COVID it just isn't easy to make dyno appointments right now. Two of these three cars where tuned on the local dyno I use, so when i can get them back on there I will. I am more concerned with how it effects drive-ability than anything else right now. As I said, increased response is the goal.
 

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Discussion Starter #8
188513

Fully installed the first of the three manifolds. Though I was not able to get the car on the dyno today, the owner says the throttle response feels better, but it was pouring out, so i will get a full update on how it drives when he finishes his 4 hour drive home tonight.

The car fired right up, idled perfect. I had to add a touch more fuel up top, it was sneaking up to a 11 AFR on his 300 horsepower tune (capped his car there to preserve the oem internals) at 19psi on the stock cams. I will be installing the second one on a AWD CVT model end of next week, that one will get on a dyno within a week after the install so we can see if/where it gained torque in the power band. So day one of testing went fantastic.

Video of the car running and shooting flames will be up on youtube in a few minutes.
 

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Woot.

Not many restrictions left in the Jukes induction system etc.
 

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This thing great in the engine bay! Any plans on adding it to the website after more testing?
 

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Discussion Starter #12
This thing great in the engine bay! Any plans on adding it to the website after more testing?
probably not. it takes 8ish hours to make one, on top of about $600 in materials plus the 8ish hours of CAD design I have into it that I would need to get back, and the countless hours of research and practical testing. The cost I would have to sell it for to justify taking up a whole work day to make would be way too much for most people. I estimate It would end up being $1500-1600. I say this because I make everything to order (though I am now stocking a lot of my smaller stuff to make it faster for people), so If by some chance I got 2 of these ordered on one day, It would take up two whole work days to make them and push back in shop work I have and other orders too.

The ones I did make are for local people that are not in any rush to get them, so there is no pressure to get them done. Most people would not want to wait weeks for it. But primarily the cost would drive 99% of Juke owners off. People say my 400 horsepower PROVEN big turbo kit is too expensive, even though its all hand made and has literal years of development behind it. Not knocking anyone, this just is not the market for things like that. So i'll stick to making outlandish and crazy builds for the one or two people a year that want them, and stick to providing excellent hand made parts and resources to everyone else :)
 

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Discussion Starter #13
Also, Update:

Spoke to the owner yesterday, he finally got dry roads to get on it (it has been pouring around here for a few days) and he says it picks up WAY faster than before. We may need to downtune the car a bit to keep him at the 300 horsepower mark, he says the car is much faster than before. So he is on the low boost map until we get it on a dyno. He says it also sounds different. Which I guess could be true, as the intake manifold will change the way the air acts in the combustion chamber and could effect noise. Again it was raining when he was up here so I couldn't tell. (I say raining, it was more like a hurricane, trees down and such) So. Success!
 

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Finished manifold number 2. I now have the process basically figured out. This one is going on an AWD CVT VF48 car this weekend then it is going on a dyno for some comparisons in the next week or two. The third one will be made early next week and will be going on the current build I am doing. 375whp minimum so that will really push this manifold to perform. I have a BMW I have to re-make a turbo set up for as the shop that tried doing it is in way over their heads, so it may slow down any progress i have on this for a few weeks.
188542
 

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Next up is Port Meth injection. Haha
 

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Oh for sure. Heck you can weld on the bungs and cap them that way they are there.
 
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