Gtr Factory Exhaust Manifold, Turbo Side Porting

[Marko R1]

I just remembered the guy who did extrude honing in Sydney had stuff for sale on ebay, maybe he has closed up. I bought a machine a few years ago but the cost to run one and the jigs you needed turned me off it so I sold it again.

Here's a graph of your head Marko with the port and no manifold, port and std manifold and port with the runner and outlet opened up, not a massive difference with the porting, there is some though. The manifolds are a definite restriction though as you can see in the graph. I'd like to test those 6 boost twin manifolds, they really look the goods.

i checked out ebay - nothing there.

i spoke to horsepowerinabox.com.au today, they dont make manifolds for the gtr.

i still think i should stick with the stock manifolds - can anyone advise if the above graph results can be improved with an extrude hone on the exhaust manifolds or am i chasing my tail for sfa gain?

[Beer Baron]

I just remembered the guy who did extrude honing in Sydney had stuff for sale on ebay, maybe he has closed up. I bought a machine a few years ago but the cost to run one and the jigs you needed turned me off it so I sold it again.

Here's a graph of your head Marko with the port and no manifold, port and std manifold and port with the runner and outlet opened up, not a massive difference with the porting, there is some though. The manifolds are a definite restriction though as you can see in the graph. I'd like to test those 6 boost twin manifolds, they really look the goods.

yep the guy in sydney who was doing the extrude honing has given it up and sold his gear apparently.

nice little test greg. have you tested the tomei twin manifolds? if you're keen to test them on a ported or standard head I'm happy to send you some to use.

[Beer Baron]

Up to a certain power level, the basic engineering (shape and cross sectional area) should flow heaps, with the restrictions multiplying at each poorly matched junction (ie. head to manifold, manifold to turbo, turbo to dump). At the factory rated power level it wouldn’t be a problem, but proper finishing work = “free” power due to efficiency gains.

I reckon you’re in the box seat Richard, with that Tomei gear at your disposal, but the guys who are cost-limited surely wouldn’t be too far behind with a set of properly finished stock cast items? Be interesting to see which way you go.

I like the general way GTRSean went with port matching, but going off pics maybe needed some more work around the short side radius at the collector? Those sharp edges looked a bit abrupt.

It’s great to see guys getting their hands dirty, learning what makes their car go, and sharing the experience.

The thing I like about keeping the stock manifolds is that they will be much better at keeping the heat (energy) in the pipe which is what we want. the tomei ones are better than most as they are quite thick walled and of course the shape of the primaries and the collector and the flanges are better than stock, but even though they are better than most stainless/mild mani's they still can't match the stock ones for heat retention.

I am going to give the stockies a going over and see how closely I can get them to match the ports of the head and of the turbine inlet. Like I said the tomei mani's worked really well on the last set-up I had and I'm sure they played a part in how 'urgently' it came onto boost and how it didn't drop off up top, but the stockies well ported may not be far behind. the other thing to consider though I guess is if you were paying someone to port the mani's and it took say 8 hours work (not unreasonable) @ $80 an hour you are not far off buying a set of tomei or 6 boost ones. but as a DIY it's the way to go.

[Dale FZ1]

Definitely a juggling act on design, and retaining heat energy is something I'd consider important. No doubt most fabricated tubular type setups would suffer greater losses than cast ones, unless ceramic coated I guess.

For the DIY blokes it's easy to disregard the cost of your own time when you've got the gear to do the work, but if having to pay a workshop yes, then a set of 6boost or similar manifolds starts to make good sense.

Incidentally, are there any pics floating around of the 3>1 manifolds 6boost make for the RB26? Interested to see what the collector design looks like.

[bigmikespec]

Incidentally, are there any pics floating around of the 3>1 manifolds 6boost make for the RB26? Interested to see what the collector design looks like.

"im late" a forum member has them I think, have a look at the RB26 dyno sticky

[J'z-R33]

Incidentally, are there any pics floating around of the 3>1 manifolds 6boost make for the RB26? Interested to see what the collector design looks like.

Here you go... 3>1 low mount 6 boosts..

[Mr GTR-32]

They look great now all we need is these flow tested to see how good they flow compared to the tomei and the stock ported items.

[Beer Baron]

some pics of the tomei manifold. quite a different collector. but a VERY straight path from exhaust port to turbine. the finish and workmanship on them is amazing and they are using good quality stainless and nice thick walls. these are one of the few stainless mani's i've seen that can take a beating without cracking.

got to love jap parts. check out all the stuff they give you with them for fitting. the 3 layer metal exhaust gaskets would be over $100 to buy on their own let alone all the genuine nissan turbo gaskets too. they even include bolt paste and the locking tabs too so your nuts don't fall off.

[Beer Baron]

you can see in this pic how small the turbine entry is on an HKS GT-SS turbo. it needs a bit of porting love I think before use.

[Gav]

some pics of the tomei manifold. quite a different collector. but a VERY straight path from exhaust port to turbine. the finish and workmanship on them is amazing and they are using good quality stainless and nice thick walls. these are one of the few stainless mani's i've seen that can take a beating without cracking.

I read this post the other week and thought to myself that I'm glad I had the Tomei Manifolds. Then during a routine check under the car last weekend I found a crack (shown up by a trail of carbon)!

I'm expecting that it should be possible to reweld, however I don't want the cracks to return so I may get some gussets or tabs welded on at the same time.

Hard to see the extent and exactly what caused it, however I'll post up some pics once I get them off over the next couple of days - stay tuned

[Beer Baron]

d'oh! where is the smiley for eating my word?!?! just goes to show they are better than most but still not perfect.

where was the crack? on a weld i'm guessing? they main improvement they have over 90% of stainless manis out there is the fact that since the pipes are extruded in the shape they need they don't weld sections of pipe. only weld pipe to flange and the collector/turbine flange. so that's really the only place they can crack and can be stopped buy a few little bracket I reckon.

they are still the best option out there i've seen.

check out the difference in flange outlet size between standard and tomei on their site. I really don't think you can port a set of stockies that far. in the graph they post they make a decent gain over even the N1 manifold.

[Gav]

d'oh! where is the smiley for eating my word?!?! just goes to show they are better than most but still not perfect.

where was the crack? on a weld i'm guessing? they main improvement they have over 90% of stainless manis out there is the fact that since the pipes are extruded in the shape they need they don't weld sections of pipe. only weld pipe to flange and the collector/turbine flange. so that's really the only place they can crack and can be stopped buy a few little bracket I reckon.

Bloody hard to see from underneath, but it looks like on the flange weld. Will know when I get them off in a day or so. Other possibility is that I transferred some force through the exhaust when I straddled the ripple strip recently at Barbagallo's

[Mr GTR-32]

Gee thats a big flow difference very interesting picture well done.

[Beer Baron]

Bloody hard to see from underneath, but it looks like on the flange weld. Will know when I get them off in a day or so. Other possibility is that I transferred some force through the exhaust when I straddled the ripple strip recently at Barbagallo's

yeah that's a big possibility. I've cracked a few headers this way. particular on the alfa which has a side pipe which of course sits quite low. it gets nailed and transfers that up to the mega $ headers and we end up with crack. :)

[Gav]

some pics of the tomei manifold. quite a different collector. but a VERY straight path from exhaust port to turbine. the finish and workmanship on them is amazing and they are using good quality stainless and nice thick walls. these are one of the few stainless mani's i've seen that can take a beating without cracking.

Richard, unfortunately I didn't have a camera with me when I picked up the manifolds today and dropped them off to the welder. The cracks were exactly along the welds that you show in the top picture. These are MUCH better than the welds on my Tomei manifolds and as shown in your bottom picture penetrate right through the thickness of the wall to the inside. MINE DON'T

The welder will simply reweld and these and is confident that it will hold. The failure is from expansion/contraction due to heating - it is obvious from the colour change that this is the hottest part of the whole exhaust system here. A little disappointing from Tomei in my opinion.

[Swiper the Fox]

I welded my HKS ones up and hand finished them internally before getting them coated.

Double ceramic coated in High-Temp Black is the only way id use a stainless manifold. Without the coating i feel the heat losses counteract the gains from increased flow.

Ported stockies hold a lot more heat in the gas path which increases gas velocity and ensures a harder hit on the turbine.

[fatz]

about 5 years ago i port matched my stock gtr manifiolds

same turbos same head

the lowest i coul dget the boost to stay on stock actuators was 10 psi before modsand 14psi after

could not get it lower

so it definately was more free flowing

[ezy_09s]

I think with nice porting of the runner entry to match ex port diameter & turbine flange,coupled with the black ceramic coating could yield results very close to hks or tomei manifolds..

Im in the process of doing this to mine right now.

[9krpm]

I just took my heat coated stock manifolds out and wrapped them a few weeks ago.

The heat coating is convenient but they don't last very long under the high temp condition.

Wrapping is the way to go.

[Marko R1]

i heard that wrapping the stock manifolds can crack the pipes (or was that only relative to aftermarket pipes?)