Is the stock cast manifold really that bad?

[CMG]

OK, so I got my SR running just fine a few months ago. Cracked my Megan elbow soon after and replaced that. Now I got a crack in my cheapo Megan manifold. After that I definitely am not gonna buy another OBX or Megan P.O.S. A new quality manifold will run over $500, and I'd rather spend that on other upgrades. So I have the stock manifold sitting here, and I'm thinking why not just bore it out, polish it up and slap that back on? I figure at least I won't have to ever worry about it cracking again. Right now I'm keeping the boost low and in the future I plan on getting a bigger turbo and a manifold. I have an Apexi Super intake and a full 3" turbo back, so if I use my stock manifold will performance really suffer that much?

[FSUDrifter]

you can extrude hone it and it's good for over 400whp easily. i was told it's provides more low-end power than the aftermarket ones with the long runners. i use it, works fine for me, can't beat the durability.

[Jesse SR20]

Haven't there been sr's making close to 400hp with a completely stock manifold ? No hone or anything.

[doridori23]

Since you have already cracked two items on your exhaust you need to take a VERY hard look at your exhaust. Is the downpipe secured to the transmission? Are there two hangers on the muffler and alteast two hangers on the midpipe? Are all your rubber hangers nice and stiff or does your pipe wag side to side like a dog when you drive? I know several people that have been running generic manifolds for years with no problems.

As far as performance goes the traditional "log" style manifold will spool a turbo faster and typically has a very slight torque diff in low RPM performance. The tubular manifolds come in many diff flavors from "pulse formed" to 4-2-1 or 4-1 etc etc but as a general rule of thumb they will spool 200-400 rpm slower (just enough to notice but not a big deal imo) however they offer better flow at higher RPMs and even on a stock setup you can see +20hp at 5500 RPM and on upgraded setups you will see even more.

[CMG]

My cracked elbow was my fault because I did not secure the dp to the transmission. I replaced it with a Tomei, secured it to the transmission, and I am using all four muffler hangers in urethane. Bottom line is that while the cracking may be partially my fault, if I use the cast manifold I will not have to worry about it period. I'd much rather use the money for better things right now and spend the big bucks for the right turbo, manifold and FMIC at a later date.

[onecrazyfoo4u]

I'm also interested in whethet the stock manifold would be good enough. But, how do you guys secure your downpipe to the transmission? I mean, my dp has a bracket welded to it, but there's nothing to bolt it to. No brackets coming off the frame or transmission.

[FSUDrifter]

there should be an exhaust hanger that comes off of the transmission x-member

[doridori23]

pic on its way getting car in the air and camera ready. Should help you fabricate something for the trans.

[onecrazyfoo4u]

Sweet, that'd be awesome, thanks alot!

[DrifterProdigy85]

Codyace on here made 400whp on a Extrude Honed Manifold and 2871R. I dont think 400whp is gonna happen on a stock cast manifold though. It doesnt seem to flow very good after 6500rpm. I noticed a huge difference in stock manifold and megan manifold on my 2871R .86 setup. Megan cracked on me too. Im gonna be using a Ichiba Version II Manifold on my new setup. Basically the same as Tomei and same or more performance as an Extrude Honed manifold.

[AE86Gio15]

Codyace on here made 400whp on a Extrude Honed Manifold and 2871R. I dont think 400whp is gonna happen on a stock cast manifold though. It doesnt seem to flow very good after 6500rpm. I noticed a huge difference in stock manifold and megan manifold on my 2871R .86 setup. Megan cracked on me too. Im gonna be using a Ichiba Version II Manifold on my new setup. Basically the same as Tomei and same or more performance as an Extrude Honed manifold.

i would stick to stock manifold. I have never had a problem with one and they are very reliable. passing 6500rpm on a sr is not needed unless you have a fully built motor which most guys do not have. save the money and spend it on something that will show you more power gains.

[Hijacker]

the stock manifold is perfectly fine for street applications. Even a 400 RWHP car could use a stock mani and be fine IMO.

I would like to know where you got your data on the spool characteristics between the stock mani and tubular manis, dori dori.

[doridori23]

D40 is broke so had to use Sony cam sorry about quality but you get the general idea. This piece will connect to a diff piece of sheet metal and then your downpipe. depending on the downpipe you might have to make it yourself but 14ga or thicker is more than sufficient.

As far as flow characteristics on a log style vs tubular on spoolup that is a part of the basic theory of Thermodynamics and also through personal experience. The flowrate of the stock log creates too much backpressure past 6500 and the engine can not breathe efficiently. An extrude hone will increase the overall diameter of the log and therefore increase the volumetric flowrate and lower the backpressure. Extrude hone will have virtually no effect on spool. I say virtually because technically the increase in surge volume will slow the exhaust pulses from impacting the blades (therefore creating lag) but the all in one design of the log limits the pulse more than the increase in exhaust manifold surge tank.

The Ichiba Ver II Exhaust manifold is a 4-2 design copied (but done pretty well) from a wonderful Tomei Expreme pulse formed manifold design. It places opposite firing cylinders 1 and 4 on one leg and cylinders 2 and 3 on another leg. They not only allow for the flow to get to the turbo but they allow for the exhaust pulse to reach the turbine blades at the greatest velocity therefore aiding spoolup. The tubular design has a high enough volumetric flowrate to support even the most ludicrous track only car. Combines the spool of a log and the flow of a tubular manifold. I recommend it whole heartedly.

[CMG]

I'm gonna check out shop prices for getting it extrude honed. I'm probably gonna just use stock and forget about it. I do things right so it's still gonna be at least a year before I go crazy on the internals, that's when I'll get the quality manifold.

[DrifterProdigy85]

i would stick to stock manifold. I have never had a problem with one and they are very reliable. passing 6500rpm on a sr is not needed unless you have a fully built motor which most guys do not have. save the money and spend it on something that will show you more power gains.

Nissan made the SR with a 7500rpm rev limiter. I dont see why you wouldnt want to make power to there. I revved my stock block SR to 7500rpm for 3 years with no problems, it wasnt till 8krpm when the lifters started floating and i broke valves. All it takes is upgraded valve springs and the SR can rev to 8krpm reliably which i didnt have. Stock bottom end has already been proven to 9krpm. 6500rpm is for T25 SR's. Its time to move up in life and use those extra 1000rpm.

[DrifterProdigy85]

Technically the stock manifold isnt log style. Its a cast divided manifold. Log manifolds have restrictive 90* bends which the stock doesnt. The stock manifold is a good design, it just lacks the smoothness to give it good flow at high rpm. I imagine honing does alot to help.

[sr20usmcswim]

upgrade manifold changes your power band depending on what you go with. I love tomei because it is so easy to install and it cheap for what you get

[CMG]

Yes the Tomei Expreme is a good choice for manifold for when I upgrade my turbo, but it costs $600. Like I said before I'd rather hone or bore the stock manifold which costs nothing, and use that until a turbo upgrade is necessary. I'm planning on building my engine before I up the boost. I try to do things right the first time around.