Cast versus Tubular turbo Manifold

[Kaleo55]

Well it looks like I might once again be in the market for a turbo manifold for KA-T project. I was interested in hearing your pro's and cons of which type of manifold is best. I have been leaning toward an equal length tubular design, but the better quality ones are a bit too high priced ala Full Race. What's your thoughts in the subject?

[PapaSmurf2k3]

flip a coin and call it a day.

[WDRacing]

It depends on your power goals really. A log isn't even close to be as efficient as a tubular unit, and thats not even being equal length. If I'm given the choice, I'll opt for the tubular. If I wasn't using a tubular mani, then I'd buy the JGS log. That mani is built to last, if you get it coated it won't ever rust either.

WD

[C-Kwik]

Cast manifolds are generally strongest. Any manifold can crank however if, no provisions for expansion are made in it's design. Cast manis generally are thick and heavy and sap some heat out of the exhaust. The Rev-hard mani uses seperate runners, but are un-equal in length.

Log manis are generally most compact and pretty strong due to their compact tubes as long as they are welded well and expansion reliefs exist. Their disadvantage is that the ports share tubes up to the turbo flange. They are certainly a compromise, but can yield good results.

Tubular manis are best for power, but present the weakest design. Expansion reliefs are critical on these as they put a lot of stress on the welded collectors. Even moreso with stainless steel as this material expands a lot with heat. It's also critical to avoid putting outside stress on it. Exhaust systems used with it need to make sure to have hangers placed so that very little weight fromt he exahsut is resting on the manifold when everything is bolted up. Hangers need to be flexible as well and allow the exhaust to move freely enough with the movements of the engine to minimize load on the mani as well. You'll find that many people will go as far as using a flex pipe/joint in the exhaust system to help minimize load on the mani. Some tubular manifolds come with bracing. I'm reluctant to advise anyone of getting one like this. The bracing itself will be much cooler than the runners and expand less when the runners heat up. Bracing can do more harm than good. A well built manifold should be able to hold the weight of a turbo with a light load from the exhaust durung engine movements without breaking a sweat. Companies using such bracing may be making the wrong assumptions about why their manifold cracks otherwise and/or have marginal parts/welds.

Unless you are looking for maximum power, than I'd opt for a good cast or log mani over a poor tubular one. I've craked a poorly prepped cast manifold and even replacing with the same kind, I ran into some slight fitment issues. The wastegate dump tube was off about a 1/4 inch. I didn't realize it at first until I was troubleshooting a wastegate gasket failure. I ended up cutting the pipe for the wastegate return tube and it ended up being about a quarter of an inch off once I was able to tighten the dump tube to the wastegate fully. While this was an easy fix, it also ended up putting the wastegate closer to the frame rail, and caused it to hit the frame rail lightly when accelerating in 1st and 2nd gears. I traded the car before I ever resolved it so I never actually got rid of it, but it would have required me to disassemble part of the turbo system to get to it and have the whole thing modified to fit. It was in a very tight spot. But the point is that manifold failures are not always going to be simple to resolve. Variations in tolerances can create issues and manifold longevity can go a long way in helping to make a turbocharging experience a good one.

[hannibal]

^ Very good advice!

my 2 cents: Unless youre going for huge power (built motor, etc), then stick with the cheaper log/cast mani and spend your money eslewhere...

[Kaleo55]

Thank you for the advice. Here's the rub, sa some of you know, I 've just spent load building my KA-T (you can see here on the forum - "KA-T project finally about to get rolling"). and as I was starting the final assembly I ran into a snafu with IAP's equal length mani and down pipe. I've hesitated to post anything negative about IAP until I reach some sort of resolution with them, although it seems unlikely at this point. I liked their design because it moved the collector and turbo foward, closer to the second runner and it seems like a well made product. I also bought their downpipe to mate with my Turbonetic t3/04 turbo and Evolution wastegate. This was to be mated to the Megan flex down pipe which I already have. The problems are four fold.

First the mounting holes in the mounting flange do not line up properly, they said my studs aren't straight but they aren't lining up with the holes in the head, and thead has been totally rebuilt (see above post). No big deal I can open up the holes.

2. The wastegate flange does not allow enough room for a dump pipe to be mated, the angle is too narrow and would place the pipe too close to runner three. They said it's because theirs is designed for a TIAL wastegte and that the head of the Turbonectics unit is too large. I have the specs for both wg's and they are virtually identical, and head sizeis not at issue.



3. The exhaust pipe ($209.00) does allow the turbo to sit flush and the bottom flange hits the top of the bell housing on the block. Again this is blamed on the fact that I am not using their Garrett turbo. This may be true but I wonder how different the turbine housings are between the two.



4. The turbo appears to sit too high but I am not sure as the motor is not in the car.



I'm hoping to work it out with IAP, but I am not certain they'll give me a refund. So this is why I am in the search for an alternative. Threadstone is marketing a cast mani that looks pretty good, but I am still not completely sold on a cast mani. Ground Zero's product looks pretty nice for a SS tubular mani, has any heard anything about this product, good or bad?

[gaehrings13]

take the downpipe to get rewelded, cut it and mark it where you want it. That is a lot of money for a dowpipe, you can get all those pipes for like 14dollars at napa and weld one at a muffler shop. you only need like two ubends, a o2 bung, and the flange. But if i was in your situation i would cut it with saw zaw rotate it a little and mark it so they can weld it for you. as for the waste gate you could cut more of an angle on the dump tube and weld it like that it would be okay.

Its kind of weird how its angled like that they should have turned that flange a few degrees out.





Just trying to give you some ideas im sure you dont want to hack your **** up.

[hannibal]

Ground Zero makes a very nice manifold. There are a few guys on here and the org that use it. I know Rick does (i think he was the first) and he's making over 600whp with it. You can see his setup here.http://www.ka-t.org/rick.php

About you IAP setup, are you sure the WG outlet faces the front? Seems like it should face the downpipe.

If youre going cast log type, I think JGS is the best for the money like WD said.

You got a link to this Threadstone manifold you mentioned? Ive never heard of it...

[WDRacing]

The WG is facing backwards...it should dump out towards the DP so you could connect the to if need be. The down pipe is an issue though. I guess I could go with IAP saying it's made for a different turbo.

Your best bet is simply to cut the DP and realign it. Any exhaust shop should be able to handle it. Worse case you pis cut out a 3* section and reweld it. This won't effect the flow enough to reduce any power. The holes can be reamed out, just make sure when aligning the manifold, that the runners are exactly where they need to be.

Sorry you're having such issues, when you're that close to a finished product any delays just hurt twice as bad.

If its worth anything, the setup looks really well put together. I can't wait till you tune it and get some dyno time.

WD

[gaehrings13]

lol im and idiot, i can't believe i didn't notice that on the wastegate. omg.........