Well, we took the car for a try after the head gasket install. 13.25 @ 120MPH
Off the line very slow 2.8 60ft. and then I would shift the car very early because wheel spin ( street dunlop tires). On 4 gear I felt some thing wrong and lift of the throttel. Took the car home running because it ran perfect onless it boosted. A piston ring whent puff! Guess it was the pump gas! anyways wiseco pistons with crower rods are next. I got a competion on the 27 (nissan Vs. Subaru) . :ylsuper
120MPH! not even a full pass!
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themadscientist
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Imissmyturbo
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I also read up on their ITM design from a few turbo books, and you are 100% correct, it is not a very good design if you are planning on doing serious competition with the RB. The way it's shaped causes it to have some of the runners sucking all of the air, and the others gasping for breath. Also with it's design could cause massive intake "turbulence."
It's a shame too, I think it looks nice
Looks and functionality are 2 different things, however....
Awesome run though, man. Post some results when you get your beast fixed, boosted up, and have good tires on her!
Out of curiosity, What turbo are you using? How much boost?
It's a shame too, I think it looks nice
Looks and functionality are 2 different things, however....Awesome run though, man. Post some results when you get your beast fixed, boosted up, and have good tires on her!
Out of curiosity, What turbo are you using? How much boost?
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rbsileighty
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I'm sure the manifold design was well thought out. It seems to have a tapered design that will allow velocity increase due to the reduction in volume toward the end of the manifold. You also have to remember that all cyl are not "sucking" at the same time, and the manifold is pressurized when the "gasping" would be a problem. The only problem would be due to the amount of volume of air the manifold can hold and the size of the TB (to allow enough air inside), which I'm sure GReddy was able to address. I would not worry to much about the manifold.
There is some serious pressure in the chamber due to a 9:1 CR and the high boost level he was running... so I'm sure that is a big factor in the problem, but like always this is my opinion. Just make sure you don't overlook running some quality rings when you do those pistons and rods.
Good luck on the rebuild!
There is some serious pressure in the chamber due to a 9:1 CR and the high boost level he was running... so I'm sure that is a big factor in the problem, but like always this is my opinion. Just make sure you don't overlook running some quality rings when you do those pistons and rods.
Good luck on the rebuild!
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Imissmyturbo
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rbsileighty
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I would say that is a good read, however keep in mind the following:
Quote »In summary, my suggestion is, until you upgrade the internals of an RB20/25, the standard plenum and TB is perfectly fit for the job. You would be better off spending your money elsewhere. Once you have got to the stage of upgrading the internals, then by all means change the plenum, but make sure you have an ECU that has individual cylinder fuel trim.[/quote]
Quote »Sure there are places for front mounted TB’s and aftermarket plenums, I have used them myself, often. But not on engines with standard internals.[/quote]
Quote »I have tested the flow rates on our Superflow bench of standard RB20/25 inlet manifolds, plenums and TB's and there is no restriction of any substance up to 450 bhp. That's not guess work, it's a FACT.[/quote]
I definitely trust Sydneykid, since he seems to have had a whole lot of experiance with these motors. I have spoken with him several times over emails, and I like his reasoning and thinking.
Fito's car is far from a standard RB25, and is putting out well over 450bhp. This is where my reasoning stems from, in that the plenum is at the least of his concerns. I still agree with what I said before.
This should however help the rest of us who are not putting out that much power in making our modifications. I do appreciate the comments, as they have helped in my decision for my RB20. Looks like I will be keeping with my stock manifold until I can design a better manifold for my 400rwhp goal... or hone the stock one. The 120 deg bend looks like the most ideal route for me.
Quote »So I might just sum up from my perspective; There is only one advantage from moving the TB to the front and that is reduced pipework length. This may lead to improved response, but it does nothing else eg; there is no horsepower advantage up to the limit of the standard internals.
Conversley I won't call them dissadvantages, let's say risks instead; 1. Poor distribution or airlfow leading to lean A/F ratios in the rear cylinders and detonation[/quote]
Again, in Fito's case he has the Microtech which can control each of the cyl's individually, which should allow him (and anyone else in the same case) to overlook the downfalls of a front facing manifold.
Quote »In summary, my suggestion is, until you upgrade the internals of an RB20/25, the standard plenum and TB is perfectly fit for the job. You would be better off spending your money elsewhere. Once you have got to the stage of upgrading the internals, then by all means change the plenum, but make sure you have an ECU that has individual cylinder fuel trim.[/quote]
Quote »Sure there are places for front mounted TB’s and aftermarket plenums, I have used them myself, often. But not on engines with standard internals.[/quote]
Quote »I have tested the flow rates on our Superflow bench of standard RB20/25 inlet manifolds, plenums and TB's and there is no restriction of any substance up to 450 bhp. That's not guess work, it's a FACT.[/quote]
I definitely trust Sydneykid, since he seems to have had a whole lot of experiance with these motors. I have spoken with him several times over emails, and I like his reasoning and thinking.
Fito's car is far from a standard RB25, and is putting out well over 450bhp. This is where my reasoning stems from, in that the plenum is at the least of his concerns. I still agree with what I said before.
This should however help the rest of us who are not putting out that much power in making our modifications. I do appreciate the comments, as they have helped in my decision for my RB20. Looks like I will be keeping with my stock manifold until I can design a better manifold for my 400rwhp goal... or hone the stock one. The 120 deg bend looks like the most ideal route for me.
Quote »So I might just sum up from my perspective; There is only one advantage from moving the TB to the front and that is reduced pipework length. This may lead to improved response, but it does nothing else eg; there is no horsepower advantage up to the limit of the standard internals.
Conversley I won't call them dissadvantages, let's say risks instead; 1. Poor distribution or airlfow leading to lean A/F ratios in the rear cylinders and detonation[/quote]
Again, in Fito's case he has the Microtech which can control each of the cyl's individually, which should allow him (and anyone else in the same case) to overlook the downfalls of a front facing manifold.
Fellas, a bit of math:
Displacement of RB20 per revolution = 1 Liter
At 7000 RPM, going through a round plenum with 90 mm diameter (about 3.5"), this translates to a flow speed of 1880 cm/s (pretty fast).
Over a single revolution, the air travels 16 cm (7" or so) at that speed and has to fill 3 cylinders. 16 cm is a significant fraction of the length of the manifold, and thus pressure gradients are a very BIG deal.
So you can see why intake manifold design is tough. There are VERY significant pressure gradients inside even a large manifold at 7000 RPM. This is why F1 and Champ cars have those huge plenums.
I doubt seriously if Greddy's design is any better than OEM. It looks like it has a smaller volume, which tends to exacerbate the problem (unless by some stroke of magic the pressure variations resonate in a constructive way at 7000 rpm).
But hey, it fits well, looks good, and makes installing an FMIC a sinch.
Displacement of RB20 per revolution = 1 Liter
At 7000 RPM, going through a round plenum with 90 mm diameter (about 3.5"), this translates to a flow speed of 1880 cm/s (pretty fast).
Over a single revolution, the air travels 16 cm (7" or so) at that speed and has to fill 3 cylinders. 16 cm is a significant fraction of the length of the manifold, and thus pressure gradients are a very BIG deal.
So you can see why intake manifold design is tough. There are VERY significant pressure gradients inside even a large manifold at 7000 RPM. This is why F1 and Champ cars have those huge plenums.
I doubt seriously if Greddy's design is any better than OEM. It looks like it has a smaller volume, which tends to exacerbate the problem (unless by some stroke of magic the pressure variations resonate in a constructive way at 7000 rpm).
But hey, it fits well, looks good, and makes installing an FMIC a sinch.
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rbsileighty
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Wulfgang wrote:Fellas, a bit of math:
Displacement of RB20 per revolution = 1 Liter
At 7000 RPM, going through a round plenum with 90 mm diameter (about 3.5"), this translates to a flow speed of 1880 cm/s (pretty fast).
Over a single revolution, the air travels 16 cm (7" or so) at that speed and has to fill 3 cylinders. 16 cm is a significant fraction of the length of the manifold, and thus pressure gradients are a very BIG deal.
So you can see why intake manifold design is tough. There are VERY significant pressure gradients inside even a large manifold at 7000 RPM. This is why F1 and Champ cars have those huge plenums.
I doubt seriously if Greddy's design is any better than OEM. It looks like it has a smaller volume, which tends to exacerbate the problem (unless by some stroke of magic the pressure variations resonate in a constructive way at 7000 rpm).
But hey, it fits well, looks good, and makes installing an FMIC a sinch.
The goal is to produce a shorter overall route (higher flow capability as well) to the TB and therefore produce a more usable powerband. However, it seems that the real benifit to this design is at WOT/Drag/dyno queen (the posted link explains this... individual TB's vs. one big TB). This setup makes since for a drag setup, it gets the air from the turbo to the cyl's in the most direct way possible. Under WOT conditions the volume of the manifold is not a huge factor once it is pressurized correct (as long as the volume is not a throttle itself)? Also, this GReddy manifold is for the 25 and not the 20.
Like I said, I will most likely use the 120 deg bend with the stock manifold (maybe honed) for my setup. I do not, and will not have as much power as Fito's car does now. I am not a drag racer, so the front mount TB position manifold wouldn't be best for my application. Looks like this discussion has saved me some money on building/buying a manifold!
My bad. Numbers should be roughly the same for RB25 tho. I was just trying to convey the difficulty of designing manifolds.
As far as shortening the flow length, I have a question. Why do people always assume that an FMIC has to have air flowing horizontally? I understand that a big, long FMIC looks good under the grill, but wouldn't a vertical flowing FMIC be better for an RB (end tanks on top and bottom with both the inlet and outlet on the driver's side). This would fit better with the stock intake manifold layout, and would not increase the overall flow length by more than a few inches, if at all.
Why do we not see more of these? I know they usually are a bit less efficient (hotter charges), but they have about half the pressure drop, which could more than compensate for the few extra inches of flow path.
As far as shortening the flow length, I have a question. Why do people always assume that an FMIC has to have air flowing horizontally? I understand that a big, long FMIC looks good under the grill, but wouldn't a vertical flowing FMIC be better for an RB (end tanks on top and bottom with both the inlet and outlet on the driver's side). This would fit better with the stock intake manifold layout, and would not increase the overall flow length by more than a few inches, if at all.
Why do we not see more of these? I know they usually are a bit less efficient (hotter charges), but they have about half the pressure drop, which could more than compensate for the few extra inches of flow path.
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rbsileighty
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They are hard to find, which is most likely the reason. I know a lot of domestic guys use them (my buddy's 383 stroker w/ Paxton NOVI 2000 blower has one), but they are not common amoung imports. Most of the intake manifold designs you see on RWD turbo cars do not have our same design as well. This is all theory, but I think it make since (obviously).
If anyone sees error in my reasoning on this post, please feel free to point it out. My experience is there, but I don't (and never claimed to) know everything.
If anyone sees error in my reasoning on this post, please feel free to point it out. My experience is there, but I don't (and never claimed to) know everything.
When (if) I get FMIC, I want to try one. Looks like an easier job overall, less cutting and welding. I know one of the very first turbo 240SX's had one (done by CarCraft, which is typically domestic projects as you said). Besides, I do not like the looks of the airflow characteristics of most of the horizontal flow FMICs, with both the inlet and exit right down near the bottom of the core.
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Yellow4g63
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Wulfgang wrote:When (if) I get FMIC, I want to try one. Looks like an easier job overall, less cutting and welding. I know one of the very first turbo 240SX's had one (done by CarCraft, which is typically domestic projects as you said). Besides, I do not like the looks of the airflow characteristics of most of the horizontal flow FMICs, with both the inlet and exit right down near the bottom of the core.
Road Race sells Veritacal Intercooler's I think the Owner Mike W (Very Smart Guy) said it cools better or something I can't rem it's been a while.
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rbsileighty
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Well, back on the topic of Fito's car... I found this and it might be helpful for you Fito:
"stronger as in which one will wear out quicker i have heard the rb25 have proplems with their ring lands up around 250 rwkw"
This is a selection from a RB20 vs. RB25 strength argument on another forum (not to be started in this thread please). I hope this helps a little. 250rwkw is ~ 335rwhp... which you are well beyond in your car's power.
"stronger as in which one will wear out quicker i have heard the rb25 have proplems with their ring lands up around 250 rwkw"
This is a selection from a RB20 vs. RB25 strength argument on another forum (not to be started in this thread please). I hope this helps a little. 250rwkw is ~ 335rwhp... which you are well beyond in your car's power.