External wastegate on Hks 1.8 manifold
 

Hello,
I am going to install a tial 38mm on my hks manifold.
As you can see from the photo the side that I am going to mount doesn't allow the wastegate to fit ideally.

Attachment 202007

So I came up with 2 solutions.

1. Drilling a smaller hole than 38mm (could this work or am I going to have boost controlling related problems?)

2. Make a flange like in the newb drawing below

Attachment 202008

Any other ideas or solutions are welcome!

IIRC the HKS is a top mount which already puts the turbo up pretty high with minimal hood clearance- won't any kind of spacer cause problems? If those attributes are true, then you'd be better off putting the port opposite the flange opening (where the runners converge) using a short tube. The top mount should allow room for this position since that makes more space under the manifold.

My only concern with this is the welding on the cast iron. Many welders here are trying to avoid it for some reason.

Cant you just have a steel pipe of 2" maybe 5" or 6" long welded to the manifold and push it down to the bottom of the engine or to the front depending on how the turbo pipes run.

I would not go with such a modification to the manifold.

:idea: Your SOL..... get a better mani with a EWG bung already designed in it..... Best solution bar none..... less headache and probably less problems just my :2cents: onther than that you could buy the cheap ebay spacer with one already in it...

http://cgi.ebay.com/ebaymotors/TURBO...Q5fAccessories
or
http://cgi.ebay.com/ebaymotors/t3-tu...#ht_500wt_1182

except one is 400 bux and the other a t3

They're just examples.. :jerkit: not actually solutions to his problems just ideas that he could look into that's all.

I get it.

There's also the issue with hood clearance with a big ass spacer like that.

yea good point..... (refer to previous statement about mani) :giggle:

Nothing wrong with welding cast iron as long as you do it right. Reason people here avoid it is because the mild/ss flows better and mild flanges are readily available. It CAN be done.

Over the last 4-years of track action, I've seen numerous cast manifolds fail, especially cast iron with welding. Maybe its a failure in execution, but not something i would jack with if you EVER want to see the track. I wouldn't trust it on the street either, but if it fails on the street you're not out any track time/$$$.

I have the same HKS mani, and hood clearance is a huge issue. You can't really go up any higher, and the way the manifold is designed, there really isn't any place to put an external wastegate. It's pretty much new manifold if you don't want to run internal.

On that note, my HKS 1.8 manifold has been awesome.

To properly weld cast iron you have to preheat 300* F weld and ping the weld in between passes. While finishing up with post heat treatment. To be honest its not worth the hassel. Thats why its fun to pick up some steel and build something bullet proof. No preheating bullshit just turn on the heat and go.

THIS

/thread

Thanks for the response.
I started to think about it when I saw this, and thought... what the hell, I can be there too.

http://img442.imageshack.us/img442/2274/hksexternal.jpg http://img442.imageshack.us/img442/h...jpg/1/w480.png

Drilling a smaller hole on the side would be a problem ?

I wonder how long it will last until there's a crack between the wg and turbine ports... not long I bet.

+1 It will probably crack between the turbo and the wastegate.

If you decide to stick with cast iron manifolds, there is more room to drill a hole on the Flyin Miata manifold and the iron is thicker and stronger. It moves your turbo to a side mount instead of a top mount. Right there on top is a good location for the wastegate.
http://www.flyinmiata.com/Store/images/22-21000.jpg
Flyin' Miata : Turbochargers : Parts and upgrades : 1994-05 FM turbo manifold


But I would recommend that you buy a good fabricated steel manifold that is designed for an external wastegate. It will flow better and make much more power. And it is beautiful.
This is ABSURDflow:
http://www.absurdflow.com/miata/stdvband/stdvband5.jpg

http://www.absurdflow.com/miata/stdvband/stdvband4.jpg
http://www.absurdflow.com/miata/stdv...bsurdflow5.jpg

ABSURDflow - Available Products

Really? My FM3 has a similar setup and it's going strong. Plus it's i'm like the 4th or 5th person to have this manifold so it has probably somewhere north 200K of miles on it.

Durability all depends on thickness of the cast iron at that section and also the composition of the cast iron upon casting... Choose wisely.

I think there's a big difference between cutting the hole in an existing casting and having the port engineered into the casting. Given the small amount of metal dividing the two ports, it will have to sustain a lot of stress from heat and load.

I'd be tempted to find a spare turbine housing and try to mod that for an external wg port. Or find one made for the purpose.
http://www.atpturbo.com/mm5/graphics...-043_450-2.jpg

Found a modified turbine housing, albeit it's from the Gurney Toyota Eagle MKIII. It can work. These engines made 700hp from 2.1L with lots of boost running for hours and hours on end without failing.
http://octanereport.com/uploads/imag...porsche_15.jpg

Agreed 110%...

I've got both HKS and Flyin' Miata cast manifolds and the FM is much thicker and heavier everywhere. I wouldn't do it with the HKS.

Stan Levine has since abandoned that design and built his own manifold to replace it.

I recommend running the internal wastegate before modifying the HKS manifold. It tends to crack in the bottom of the collector without any modification. I know, mine was welded twice and cracked again. If you want external then I highly recommend running a different manifold and selling your HKS in the usable condition it is in now.

If your port your turbine housing WG port like BEGI I bet you'll be fine.

I know like nothing about fluid dynamics but I'd be willing to bet that because of the location of the port that it creates turbulence in the housing which would significantly affect spool...

I don't think it would affect spool much at all because the WG should only open after target boost has been hit.

Thats not the issue the issue is that the placement affects the A/R ratio of that part of the turbo so that it isnt transitioning properly. It would never flow quite as good as a turbo that wasnt like that.
But unless you just want to pick the fly shit out of the pepper, its probably fine, and Im sure plenty of people have used them successfully.

I would have to agree that this design would have an effect on efficiency. This would not so much hurt spool however, it would hurt with boost spiking I am sure. This would be due to the high velocity air being pushed through the turbine housing. And in Physics, the material (air in the case), will take the path of least resistance. In this case, the air is more likely to continue through the turbine housing rather than make a 90° turn into the wastegate. So the opening of the wastegate will be slightly delayed thus causing a slight to mild boost spike on the system. Thusly this is why when designing a manifold the optimal setup is to have the air have a direct path to hit the wastegate rather than making an extreme turn. :2cents:

It's almost ironic that the turbine housing with the port casted into it is in the same location that the championship winning endurance toyotas had it. And I doubt they stuck the port there because they didn't have anywhere else to put it. Gurney is not known for making compromises.

To the OP- what's the issue with the internal gate now? Why the urge for the external gate?

I like that wastegate turbine housing, looks like one solid piece.

^That I agree with... It may have been a way to take out a failure point as compared to adding a flange to the manifold. However, it sure does look nice... It's just that I can't get past the velocity that the incoming air would be carrying that would make it want to enter the port readily rather than pass by it and cause a slight overboost situation. Could they have installed it there to get the slight overboost situation? Essentially a 'sneaky sneaky' way to get some extra horsepower that might not make flags fly during inspection? Then all they would have to do is tune for this and done. Just a thought...

As far as being worried about overboosting, you can just set up your boost controller to open the waste gate at a slightly lower pressure and so when you would be going to over boost you would be at your target pressure.

Having not seen the inside my concern about that housing it that there is a 90* lip that would catch some of the air and create a sort of bubble affect from turbulence generate by that amount of air hitting that angle that would alter the flow of air right at that lip forcing air to not travel correctly though the housing. (see image for possibly convoluted worry, sorry for not using cad, I don't have it on the computer)

argh!

http://www.boostedmiata.com/technica...te_turbine.jpg

http://www.boostedmiata.com/technical/wategate_out.jpg

The above design would be much better if you had to run a turbine housing mounted EWG...

Finally done and works like a charm.

http://img97.imageshack.us/img97/9223/dsc0028i.th.jpg

http://img191.imageshack.us/img191/345/dsc0030z.th.jpg

Turbo no hit wastegate?

I ran accross this myself with my last car. I found a welder that did it with no guarantees and I had asolutely 0 problems. I will get some pics of it. Its a mildsteel tube welded right to a cast iron peice. The welder is in PHX and is truly top notch and explained that he essentially used something similar to a brazing rod, but much better. I am welding-stupid so I really dont know excatly what it means. But it supported the weight of my 38MM and the 2 foot dump pipe under very hot conditions (the ar ran very rich with little timing advance meaning tons of heat) without any problems. This was on a OEM 2G DSM ex mani. Pretty weird setup actually, you dont see a lot of internal and external gated 16gs LOL.

This is a good point too. I did not care much if I cooked a stok 2G mani because they are a dime a dozen anyway. Not neccesarily the case here.

This is a fantastic design really. Its totally correct that the fluid will take the path of least resistance. So what makes one path easier than another to take if you are a very hot gas with a relatively low density and high pressure?

Pressure differentials. A proper wastegate mounted to that location opens up a huge low pressure path of the hot exhuast gas relative to the turbine housing itself, which is inevitably a throttling device that creates high pressure. The hot exhuast gas has 0 trouble 'making the turn' because of all the forces affecting each little particle of exhuast gas, inertia is was down the list. Inertia is pretty much the only thing that makes it diffcult to for a particle to turn like that in this case because the port has plenty of volume and I assume no huge chuncks of metal in the wg passage.

Basically, gas will flow right out that port in higher volumes than going through the turbo untill the pressure going out that port is equal to the back pressure of going through the turbine housing itself. This is good.

You might get a bit less laminar flow through that thing, but my bet is that its pretty much unmeasureable on the dyno at any RPM in terms of boost threshold or TQ from one setup running that and another running a collector-mounted EWG.

Nope :)

Nice work man, I had my doubts when I started reading the thread but looks like you pulled it off. Any pictures of everything all mounted up?

How about your oil drain line?

The fit is quite tight but I'll try to get some decent pics today :)

Here is one of my friends Greddy mani but I dont trust it much:
http://img15.imageshack.us/img15/9250/dsc00022yz.th.jpg
http://img269.imageshack.us/img269/3...00023wr.th.jpg
http://img5.imageshack.us/img5/4875/dsc00026tb.th.jpg

I have a bad feeling your oil drain line is going to cause a fire. Make sure you keep it away from the wastegate, and better insulate it as well.

It's close but it doesn't touch the wastegate. Insulation is wise thinking, thanks.