Sneak peek at gutted plenum dyno results.

[Jason84NA2T]

I now have the dyno data and will start formatting it to complete my plenum page when I get time. Three pulls were done on each plenum, and as each one got more heat into it after a pull, power went down 7-10hp as expected. This is something you really can't avoid, except for giving the same amount of time between pulls to allow the plenum (and IC) to cool slightly. The plenums were not run stone cold on the first pull, the engine was warmed for a little bit before we ran them, still they get heat in them quickly, so even 5 mins between pulls would not restore them to ambient temp. This was also as expected, so I will average the best and worst of the 3 pulls on each for comparison. For most of them this was the first and third pull.

All of the gutted stock plenums have similar characteristics and made very similar power figures. The stock plenum flat out sucks.

Below is an image of the end result, showing gains of (one of) the modified plenums over stock. I'm not telling which gutted design performed "better" until the page is done (so you can read it there). As I said; there is, overall, only a very small difference between each of the gutted plenums.



Below is a pull with the stock throttle body and the 240SX throttle body. This confirms the flow bench findings that the 60mm throttle body is a completely useless waste of money on an un-modified plenum even if you port the entry to match. I can't believe so many people wasted their time on this one with no flowbench or dyno evidence for so long. Behold parrot power! Stock is the solid line and 60mm is the dashed. We gave it some extra cooldown time while swapping the throttle body, so it should have made a couple more hp just from that; oh well.



In a small side note, I want to throw this out there for debate. I've read some people's postings on other forums saying things along the lines of bigger is better, and they put big throttle bodies on little engines, so why not on ours? This is a simple tailoring of the throttle characteristics of the engine in question, and not by any means a measure of actual performance "design" or horsepower expectations of the engine. Throttle response and part-throttle characteristics change greatly with the size of the throttle plate (less movement + larger plate = more airflow... derrrrrp).

[G-E]

the 60mm t/b might be best suited to the pathfinder plenum or any custom one...

reason being is their internal diameters are going to be much larger than 60mm already, pathfinder (besides being squarish) has an extra few mm top and bottom and lots on the sides

it's too bad you didn't test the difference on a larger chambered intake but at least you can show it's not an upgrade for stock...

[j30_vg33et]

Great testing!

Thanks for finally putting some teeth in the intake manifold debate. When you update your intake plenum page, be sure to include your current mod's to give a sense of how the data will scale for others.

I would have loved to see the comparison between:
stk Z / LP Perf / Pathfinder / Gloria(Maxima) manifolds.

The reason being, they are all fundamentally different in their design.
stk z / LP Perf = short runner, common plenum.
Pathfinder = long runner, common plenum.
Gloria(Maxima) = short / long runner, variable geometry.

Has anyone put a Gloria manifold on a flowbench?

Also, what's the deal with the big torque bump at 3600? Did you dump in a bunch of timing there?

[Jason84NA2T]

Re: Great testing!

j30_vg33et wrote: Thanks for finally putting some teeth in the intake manifold debate. When you update your intake plenum page, be sure to include your current mod's to give a sense of how the data will scale for others.?
I will be absolutely sure to add that information. It was my full intent to dyno on a engine with completely stock heads and lower intake. I actually went to do just that but discovered the engine had developed so much blow-by that it pretty much stank us out of the shop. I decided to make another trip (mind you the dyno is about 2 hours from my house) once I had the "new" engine in; a week and a half later.

j30_vg33et wrote: I would have loved to see the comparison between:
stk Z / LP Perf / Pathfinder / Gloria(Maxima) manifolds.

The reason being, they are all fundamentally different in their design.
stk z / LP Perf = short runner, common plenum.
Pathfinder = long runner, common plenum.
Gloria(Maxima) = short / long runner, variable geometry.

I would have loved to also, but time and money... fabbing up new charge pipes to use ONE time, new blockoff plates, plus additional runs, just too much. The financial aspect of anything performance-related can- and usually is -the determining factor in how far you get or how much gets done on any project. I am grateful to the few people who pitched in a little money to help me out, but after the response I got from other people, I can honestly say if I ever do anything project like this again that I won't bother publishing the results.

I too would have loved to see the difference runner length made on the torque and hp figures, even more so on an NA engine. The flapper on the maxima plenum is interesting to me. The center of the plenum 'opens' to a common chamber, but to accomplish what result? It would be nice to see on a flow bench... which leads you to your next question:

j30_vg33et wrote:
Has anyone put a Gloria manifold on a flowbench?

Not as far as I know. There was one for sale on ebay a couple weeks before I flowed the batch, but I didn't want to spend $80 for two parts I will probably never use.

j30_vg33et wrote:
Also, what's the deal with the big torque bump at 3600? Did you dump in a bunch of timing there?

There's a 'bump' on that tune I worked into the timing map at 2800-3600 to encourage fast spoolup. It worked pretty well on the street, but caused a strange "camel hump" on the torque curves as timing was pulled immidiately after for the torque peak, especially at higher boosts. The thing is it made the car so much more drivable that I left it. Sometimes the system seems a little laggy too, probably having to do with the amount of volume in the system compared to how quickly it builds boost and moves into the higher load columns.

[j30_vg33et]

intake manifolds

I understand what you're saying about the leach factor when it comes to financing research. But, sadly, that just seems to be how it goes. It's the kind of thing where you want to do the research anyway, so you do, and everybody does benefit if you post it. One of the best examples is the diy_wb guys. They figured out how to do the back-end electronics to read out wide-band o2 sensors, made it public, and were promptly cloned by Techedge and all the other low cost wbo2 shops. The dudes who did the basic work get no credit, nor compensation, but we all benefit. Just how it goes...

I'm in the unique situation (around here) in that I'm running the VG in a 91 Maxima. Thus the comparison to the Gloria manifold is most interesting. Here is some info on the theory of that set-up from the FSM:



So when the valve is open, Powervalve = off, the upper plenums are connected and each cylinder can draw air through both throttle plates. This is like a short runner intake manifold e.g. z31. It should be noted that even in this mode, the runners in the lower manifold are much longer than a Pathfinder or z31 lower since they actually cross the center of the V rather than meeting in the middle. This is how Nissan splits the plenum.



Here the valve is closed, sealing the two sides of the manifold from each other. This seperates cylinders 1-3-5 and 2-4-6 into two little three cylinder engines. It also effectively increases the intake runner length to about a mile as illustrated. Since the engine has a 1-2-3-4-5-6 firing order, splitting the cylinders up like this eliminates any cross-talk between intake events and keeps one cylinder from stealing from another. That's the theory anyway.



This is the dyno graph from my Maxima when it was bone stock. Saddly, it's the only dyno pulls I ever did. You can pretty clearly see the effects of the manifold when it's "on" below 3650 rpm. You can also see the torque nosing over pretty hard before the valve opens.

I'm not sure if it would be equitable to compare an NA z31 to this config. Maybe. This motor was 9:1, sequential injection, with some seriously nasty Y-pipe & exhaust system going on. If someone out there has a dyno graph of a NA Z it'd be interesting to compare the shape of the curve.

I'd like to figure out what the main culprit is in killing the top end power of that engine configuration. Intake manifold, ports, cams, exhaust system...

Jason, you said something about the throttle response not "being-there" in your post above. I assume that is in reference to the big plenum manifold. Did you try smoothing / shoring-up the "camel-hump" with timing?

Thanks again for doing all this work. I'll be happy to chip in where I can.

[MrwassmanNA2T]

Re: intake manifolds

I don't fully understand, so this maxima/gloria manifold is a variable length type of thing?

[Jason84NA2T]

I can see how that would make the common runner length for those 3 cylinders much much longer, but does opening the center chamber change the dynamics of the airflow that massively? They are still all pulling from the two long runners. I understand the theory, but the execution seems somewhat strange compared to many other variable intake designs.

I guess I would have to compare your dyno graph there to a pretty much stock NA Z31 to see the difference in shape, but it looks like it does make a fair bit more low end torque.

I notice your user name.. are you planning a VG33 swap?

[j30_vg33et]

Uh, yeah.

WaZZ300: Yeah, it's a variable length manifold idea.

Jason: Yeah, building a VG33 from a 97 Pathfinder. It's a total saga worthy of a TV movie.

Stk Maxima intake manifold. 370cc injectors / M30 ecu.
Garage ported heads / chambers. Coated. JWT S2 cams / springs.
8.5:1 Arias pistons. Coated.
Modified z31 exhaust manifolds. eHoned. Coated.
GT35R kinda, 40mm Tial gate. A/W intercooler.
3" exhaust, cat, muffler, muffler.

Like everyone, there's a bunch of development work in the cards. Speaking of which, I should get back out in the garage and put some more stuff together.

[G-E]

the last variable intake I was reading about used two runners per port with a flapper instead of a butterfly that would open one and block the other, the actual runner difference was 5" or so

think of the pathfinder plenum doubled over so the log paralleled the ends of the runners, and had a short velocity stack shooting into the lower plenum, with the flapper door between that and the upper runner

the actual implementation was small so the curves were simpler and nicely tapered into the head, it was an inline engine so none of the splitting complexity we have

none of this is beyond the realm of laymen as far as the concept goes, the actual engineering behind such things is really really complicated, and requires tons of testing

the gloria plenum could be considered the cheap hack that serves the purpose but keeps cost down

[MrwassmanNA2T]

God an inline would be so nice

[j30_vg33et]

Bump.

Excited to see the results page!

[Jason84NA2T]

j30_vg33et wrote: Bump.

Excited to see the results page!

I can't seem to get excited about anything lately.

[j30_vg33et]

Uh, bump.

I'd be pretty excited about all that extra power you're making. Good job!

You really should get that GT35R on there and enjoy it's lagless 70% turbine efficiency. Which a/r did you order?

[Jason84NA2T]

j30_vg33et wrote: Uh, bump.

I'd be pretty excited about all that extra power you're making. Good job!

You really should get that GT35R on there and enjoy it's lagless 70% turbine efficiency. Which a/r did you order?

yeah, it's funny to compare the curves... the new powerband is much broader than this old one. The only changes were the maf bypass, another 4PSI boost and advancing the cam timing 4 degrees. Going from 418 to 452 was a pretty big difference on the butt dyno too. I wonder if the walbro could keep up with a small shot of nitrous on top of that to hit that "magic" 500whp?

It's not a R as far as I can tell, it's a standard version and the smallest of the GT35's. I didn't pick it out because it came installed on a car I bought last year along with a bunch of other go-fast goodies. The compressor is not really going to be an upgrade, but the turbine and turbine housing are as well as the exhaust elbow and external wastegate. That is, if I even decide to swap them on. I like how the car drives now, and a higher spooly RPM would most likely just mean less boost in lower gears and less midrange torque.

[grahfz]

do I smell a second 'crazy-fast z' in the works?