Modifying the stock manifold rb25det

[datsunmotorsports]

Do you guys have any opinions about this?

I mocked it up and had a acquaintance lathe and weld it up.Im not sure if Im actually going to use it. It looks good and accepts the stock throttle body. I was going to use the Q45 Throttle body, but I couldnt fit a 4" tube on the manifold without serious work.

I was thinking about bolting it up and strapping the car down to the dyno to see if it helps or hurts the torque. Though i cant imagine this being any better than the stock position.

Hell, Ill probably get crap for messing around with this.

[img]http://www.datsunmotorsports.selfip.com ... 010246.jpg[/img]

[img]http://www.datsunmotorsports.selfip.com ... 010247.jpg[/img]

[img]http://www.datsunmotorsports.selfip.com ... 010248.jpg[/img]

[img]http://www.datsunmotorsports.selfip.com ... 010249.jpg[/img]
Modified by datsunmotorsports at 10:24 AM 7/15/2009

[DrifterProdigy85]

Nice. A buddy of mine from RB-Performance.net did this to his too. I cant see it helping or hurting anything. Really it just gives a better look not having the IC piping across the top of the engine.

[datsunmotorsports]

Nice. A buddy of mine from RB-Performance.net did this to his too. I cant see it helping or hurting anything. Really it just gives a better look not having the IC piping across the top of the engine.

Actually Im trying to make room up front for the AC Condensor as my hack job of an intercooler and piping takes up the whole front of my car and this will free up the room and let me put my air filter up front.

Im test fitting it today and worried about the angle of the throttle body hitting the hood or blocking the radiator hose area.

[20DET]

i run a rb20det manifold dats cut and weldid with the factory throttle body weldid on for a front facing plenum...works great...looks better then the ugly pipe over the rocker covers and significantly reduced lag

[Darius]

This has been done before and it has also been critiqued, somewhat negatively. The problems with the longitudinal intake manifolds is that cylinder #6 runs lean. If you're not shooting for big power, then it is probably safe. But if you're looking for considerably more than stock, I'd research this a little better and honestly, steer a different direction. I'd rock a Freddy manifold before I'd change the intake manifold in that way.

[datsunmotorsports]

This has been done before and it has also been critiqued, somewhat negatively. The problems with the longitudinal intake manifolds is that cylinder #6 runs lean. If you're not shooting for big power, then it is probably safe. But if you're looking for considerably more than stock, I'd research this a little better and honestly, steer a different direction. I'd rock a Freddy manifold before I'd change the intake manifold in that way.

Hey Darius,Do you know where you read that?I dont know enough on the subject. I do know that a setup like this on a carb would go lean on the rear, but cant see how a EFI would do so as well, though Ive heard it many times on forums. I figured that the first runner would have a problem not the last.

In any case Im not looking to get much more than 300whp. In the future if Id like to shoot for more, but I figured I would spend the money on the Greddy manifold. For now I just need something to let me install my AC and the new intercooler without spending 1200USD on just the manifold.

[Darius]

It is documented in several threads on NICO as well as SAU. Basically, the issue is that the air enters the front end of the manifold and is forced to turn 90* to enter the intake runners. With it being difficult for the air to make the turn into #1 & 2, the excess air backs up into the remaining cylinders with #6 being forced to take the remainder of it. This creates a lean condition in cylinders 5 & 6 compared to 1 & 2. The exhaust gases recombine at the turbo to create an AFR that appears normal at the wideband O2 sensor. The necking down of the Greddy/Freddy towards the rearward cylinders helps mitigate this situation, but it isn't ideal.

An ideally designed plenum will employ velocity stacks and have adequate volume to help equally distribute air to all cylinders and keep cross-stack velocity in check. The runner length should also be resonance tuned for best performance in the rev range that you plan to run.

[mean240]

It is documented in several threads on NICO as well as SAU. Basically, the issue is that the air enters the front end of the manifold and is forced to turn 90* to enter the intake runners. With it being difficult for the air to make the turn into #1 & 2, the excess air backs up into the remaining cylinders with #6 being forced to take the remainder of it. This creates a lean condition in cylinders 5 & 6 compared to 1 & 2. The exhaust gases recombine at the turbo to create an AFR that appears normal at the wideband O2 sensor. The necking down of the Greddy/Freddy towards the rearward cylinders helps mitigate this situation, but it isn't ideal.

An ideally designed plenum will employ velocity stacks and have adequate volume to help equally distribute air to all cylinders and keep cross-stack velocity in check. The runner length should also be resonance tuned for best performance in the rev range that you plan to run.

if you guys search on this i started a thread on this and didn't get much reply . but on the other forums in the UK i'm a member on a few of them . and alot of the members run the modded stock manifold and there have "NOT BEEN A CASE OF SOMEONE BLOWING THEIR MOTOR BECAUSE OF THIS MOD". A Tunner has quoted that. i have some walkthru and how to do that mod! i believe...

really cheap and easy. and for the record no power has been reported by doing that mod. Only "Lower intake temps and Throttle has inproved by 40% if i remember correctly!

PS: pics dont work by the way.

[20DET]

well id love to debate this...ive had myn tested and it flowes evenly to all 6 on a flow tester...the top were the throttle body bolts to is raisened tho to put it up higher....and upon inspection of the spark plugs theyre all clean but number 6 is slightly the tiniest bit black on the insides compared to the other 5 so number 6 is the slightest bit richer....but then thats the end that the fuel enters the rail 1st so i guess that 1 will allways run richer thn the rest...if you get someone skilled to do the job it works perfectly

[mean240]

well id love to debate this...ive had myn tested and it flowes evenly to all 6 on a flow tester...the top were the throttle body bolts to is raisened tho to put it up higher....and upon inspection of the spark plugs theyre all clean but number 6 is slightly the tiniest bit black on the insides compared to the other 5 so number 6 is the slightest bit richer....but then thats the end that the fuel enters the rail 1st so i guess that 1 will allways run richer thn the rest...if you get someone skilled to do the job it works perfectly

Nice, well there you question solved

[240z4u]

You guys make all these claims about flow, but until you have actually looked at CFD modeling of different types of intake manifolds you are just stating others opinions.

Someone claimed that this mod never blew up a motor? okay.

You flowbenched that manifold that you have? Sounds like you didn't to me. Also sounds like if it was flowbenched it was not done under pressure in a turbocharged scenario.

you guys are arguing with physics, which is pointless. I will agree, that perhaps the issue is over hyped though, and it may not be as serious as everyone says.

Evan

[Darius]

I also find it impossible to believe that all 6 cylinders receive the same amount of air by modifying the stock manifold. The orientation of the stock manifold doesn't even result in equal air distribution. It is pretty good, but not equal. And yes a guy on SAU posted his results after putting his manifold on a flow bench and measuring the cfm thru each runner. Cylinders 3 & 4 received ~290 cfm while the remaining cylinders had ~260 cfm. 10% difference.

And I call BS on guys never blowing their motors because of this phoenomenon. When piston rings or head gaskets go bye-bye, guess which cylinder it is on. Almost always 5 or 6. So you can hypothesize and talk to your "tuner" all you want, but there is evidence that when the engine power gets significantly above stock, these things begin to manifest themselves into knock. That's why I say keep the hp down and you won't notice anything.

[datsunmotorsports]

Well as you can see by the pictures IF you were able to pull them up I am short a bunch of fittings and piping.

Seems like the consensus is that this manifold will work just fine on a stock or close to stock RB25det with no problems.

Its a tight fit with the 200sx radiator, and shouldn't be a problem with the other radiators that mount the hose on a side tank like most aftermarket installs do with this swap. I think Ive come to the end of the line with this manifold. The gap in cash for all the piping and fittings is too much for me at this time.

If someone wants to pickup where I left off Im looking at selling the manifold for what I have into it... which is too much, but it satisfied my curiosity. If not it can collect dust in my garage like a lot of other things.

[240z4u]

So essentially it just won't fit well enough for you? Seems a shame to bail on it now, it will certainly work fine for a stockish setup! I didn't mean to indicate otherwise.

[mean240]

You guys make all these claims about flow, but until you have actually looked at CFD modeling of different types of intake manifolds you are just stating others opinions.

Someone claimed that this mod never blew up a motor? okay.

You flowbenched that manifold that you have? Sounds like you didn't to me. Also sounds like if it was flowbenched it was not done under pressure in a turbocharged scenario.

you guys are arguing with physics, which is pointless. I will agree, that perhaps the issue is over hyped though, and it may not be as serious as everyone says.

Evan

I got mine done! I spend most of my time on the skylineforums than nico. searching for info on the motors and other BS, but after searching and asking alot of Questions from people who did this mod, and the person who said it that a motor has not blew up because of that mod was a tunner.. and i'm assuming "YOU DON"T KNOW ANYONE who BLEW THEIR motor EITHER DO YOU " with this mod ?

I see what you're saying though, without a chart for you to LOOK at and say there you go! hard to believe , but oh well.

[mean240]

I also find it impossible to believe that all 6 cylinders receive the same amount of air by modifying the stock manifold. The orientation of the stock manifold doesn't even result in equal air distribution. It is pretty good, but not equal. And yes a guy on SAU posted his results after putting his manifold on a flow bench and measuring the cfm thru each runner. Cylinders 3 & 4 received ~290 cfm while the remaining cylinders had ~260 cfm. 10% difference.

And I call BS on guys never blowing their motors because of this phoenomenon. When piston rings or head gaskets go bye-bye, guess which cylinder it is on. Almost always 5 or 6. So you can hypothesize and talk to your "tuner" all you want, but there is evidence that when the engine power gets significantly above stock, these things begin to manifest themselves into knock. That's why I say keep the hp down and you won't notice anything.

I agree with what you're saying, but first he's not my tunner never said that. thats what one the tunners said on the forum, and there's a few people running this mod with no problems pushing over 400HP search and find out for urself!

[Darius]

I don't know what threads you are reading there because everything I can find argues against chopping the stock manifold. There are occassional posts by guys that can't grasp the concept of fluid dynamics who say, "Well, it works. I've had it in there for 4 years without a problem."

There is an overwhelming e-pinion that there are more risks and drawbacks than the mod is worth. And a used chinese manifold is only like $300. Why tempt Murphy to save a couple hundred bucks?

Do whatever you want. I'd never do it and I strongly suggest not pushing it if you do.

[240z4u]

http://forums.hybridz.org/show...ntake

Guys, if you really want to learn something about intake manifolds, check out this thread. Doubt you make it through all 18 pages LOL. Really great thread on flow characteristics.

This is the reason that I vehemently deny that a forward facing manifold can provide perfect airflow.

Evan

[datsunmotorsports]

So essentially it just won't fit well enough for you? Seems a shame to bail on it now, it will certainly work fine for a stockish setup! I didn't mean to indicate otherwise.

It fits great and would make everything fit better under my hood. IF I had the rest of the plumbing. I have another project that is taking precedence at this time though. When I complete this project (fingers crossed) I will figure out what I am going to do about my intake.











1968 2000. The body is hovering 3' above the pictures and still needs me to replace the passenger side door pillar as it is rusted out.



Its my wifes car and she says I have to get focused on it so it will be done in time.

BTW if you dont own an aluminum welder(tig) and a lathe and can work both of them, then your looking at machine/welding costs that are a good chunk of the cost of a Freddy Manifold.

[mean240]

http://forums.hybridz.org/show...ntake

Guys, if you really want to learn something about intake manifolds, check out this thread. Doubt you make it through all 18 pages LOL. Really great thread on flow characteristics.

This is the reason that I vehemently deny that a forward facing manifold can provide perfect airflow.

Evan

o

ohhh im sorry, i started a thread here while back but um check out skylineowners.com i'm a member there!

lots of info on who did it and gains Dyno charts.. and of course people who desagre of course !

lots of good info!