Wastegate Runner Length
11-29-09, 01:35 PM
#1
Wastegate Runner Length
Lately I've been working on my long runner SS304 exhaust manifold that mates up to my GT35R with a Tial SS housing. I designed the manifold to be efficient and maintain good response. I've got everything laid out for the manifold and ready to weld except for the wastegate tubing.
I always see threads about wastegate runner lengths being equal, but not really on the effects of the WG runner lengths. My setup is custom so not too many people have similar setups. Since I have a merge collector, I will only have 1 wg runner that comes out of the elbow right before the turbo.
My main question is what are the effects of wg runner lengths? In my case, (just throwing numbers out there) I would be comparing a 3" runner right out of the elbow to something like a U-bend 12" runner. How much does exhaust theory about pulses/pressure/tuning apply to wg runner length? The wg runner entry is placed right before the turbo either way to control boost creep.
Just look at the pictures so you understand what I'm talking about better. Just imagine that the wg runners are welded on the elbow; I tried to make the pictures look like they were fitted. Really, I would rather use a longer U-bend but I don't know if that is the better option to control boost and such.
Short WG Runner
Short WG Runner Reference
Long WG Runner
I always see threads about wastegate runner lengths being equal, but not really on the effects of the WG runner lengths. My setup is custom so not too many people have similar setups. Since I have a merge collector, I will only have 1 wg runner that comes out of the elbow right before the turbo.
My main question is what are the effects of wg runner lengths? In my case, (just throwing numbers out there) I would be comparing a 3" runner right out of the elbow to something like a U-bend 12" runner. How much does exhaust theory about pulses/pressure/tuning apply to wg runner length? The wg runner entry is placed right before the turbo either way to control boost creep.
Just look at the pictures so you understand what I'm talking about better. Just imagine that the wg runners are welded on the elbow; I tried to make the pictures look like they were fitted. Really, I would rather use a longer U-bend but I don't know if that is the better option to control boost and such.
Short WG Runner
Short WG Runner Reference
Long WG Runner
11-29-09, 02:19 PM
#3
I'm certainly not a fluid dynamics expert, but I would assume you wouldn't want the need to accelerate the mass of air that is stagnant when the gate is closed. The longer the runner, the greater the mass of air that needs to begin moving in that direct when the gate begins to crack open.
I would think the best placement would be to have the v-band right on the outside radius of the bend.
I would think the best placement would be to have the v-band right on the outside radius of the bend.
11-29-09, 03:40 PM
#4
Another question, suppose I do go towards the more direct method with a short runner wg system, would it be best to just run the runner inline with the merge collector (just like I have pictured in my setup) or run the runner tangent at something like 45 degrees?
11-29-09, 03:45 PM
#5
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do it inline. the more direct, the better. you want absolutely no restriction when it is time for that wastegate to open, otherwise it wont function as well as it could.
11-29-09, 04:07 PM
#6
You should also use a nice brace on the turbine housing to help support the turbo since you are using very thin tubing..
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11-29-09, 07:06 PM
#9
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is this going in an rx7?
it could just be my eyes, but it looks to me like it doesn't have enough space between the engine and strut tower. I know in an FC theres only 11 inches between the engine and the tower, and i believe that a FD has even less space.
have you measured it up yet if it is going in a 7?
i could be completely wrong, i'm just speaking my mind.
it could just be my eyes, but it looks to me like it doesn't have enough space between the engine and strut tower. I know in an FC theres only 11 inches between the engine and the tower, and i believe that a FD has even less space.
have you measured it up yet if it is going in a 7?
i could be completely wrong, i'm just speaking my mind.
11-29-09, 08:47 PM
#11
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11-29-09, 09:03 PM
#12
Yeah, response should be really nice and hopefully this manifold will give me a broad power band. I'll have to log back pressure vs boost to see what ratio I'm at. Theoretically, the design should give me something close to a 1:1 ratio to reduce engine stress and increase efficiency = more power.
But I don't want get my hopes up high since this is the first "prototype". I'll do some testing with it and if everything holds up fine, maybe I'll sell a couple off since I have enough tubing for another 1-2 exact copies.
But I don't want get my hopes up high since this is the first "prototype". I'll do some testing with it and if everything holds up fine, maybe I'll sell a couple off since I have enough tubing for another 1-2 exact copies.
11-29-09, 09:19 PM
#13
I like your design a lot, and fit is good.
I wanna ask how big of a dp do you plan on running because it doesnt look like you have a ton of room for it, could just be the pics but I am curious?
Also make sure you plan the welding steps on that thing flawlessly or its gonna be a royal pain, tig welding can be a biatch.
I wanna ask how big of a dp do you plan on running because it doesnt look like you have a ton of room for it, could just be the pics but I am curious?
Also make sure you plan the welding steps on that thing flawlessly or its gonna be a royal pain, tig welding can be a biatch.
11-29-09, 09:29 PM
#14
Yeah, that why you see several taped sections. I only tacked pieces together that I thought would work out nicely during the welding process.
11-30-09, 01:50 PM
#15
After staring at that setup for 10 minutes I finally understood what you are doing. I had initially assumed you were running dual wastegates which was probably why I was confused. How come you went through all that trouble to get a better response and powerband but decided to go with an undivided setup?
Either way, nice setup.
thewird
Either way, nice setup.
thewird
11-30-09, 02:51 PM
#16
I figured somebody would ask why I didn't just go with a divided housing. I guess my reasons are...
1. Tial housings are easier/simpler with an exhaust inlet v-band connection.
2. Tial housings are more compact/lighter
4. Tial housings are stainless
5. Tial housing designs make up for that lost response that you see from undivided housings.
a. I don't believe my manifold is perfect in any way, but I do believe (relatively) properly designed manifolds can get away from divided housings to maintain response.
b. Check out the Twins Turbo Jack Mardikian FD manifold.
6. It was easier to design a long runner manifold using a merge collector than dicking around making the bends go into a t4 flange.
7. A merge collector also makes wastegate plumbing easy.
8. I wanted a fun challenging project. Anyone can make the "normal" looking manifolds.
9. It'll work fine for me, pros or cons, it's just what I wanted I guess.
FYI, I just measured the runners and they came out to be what I expected. The rear was around 26.25" and the front was around 28.25". Not perfectly equal and I knew it wasn't going to be when I built it. Its just the compromise I made when I designed it because it gave me easier to work with angles and better clearance. Hopefully it doesn't make to much of a difference.
Can anyone recommend good K-type thermocouples? I want to order the EGT bungs and weld them on the tubes before I weld the tubes to the base flange. However, there are 1/8" and 1/4" NPT bungs and I'm not sure which sensors to use yet for the decision.
1. Tial housings are easier/simpler with an exhaust inlet v-band connection.
2. Tial housings are more compact/lighter
4. Tial housings are stainless
5. Tial housing designs make up for that lost response that you see from undivided housings.
a. I don't believe my manifold is perfect in any way, but I do believe (relatively) properly designed manifolds can get away from divided housings to maintain response.
b. Check out the Twins Turbo Jack Mardikian FD manifold.
6. It was easier to design a long runner manifold using a merge collector than dicking around making the bends go into a t4 flange.
7. A merge collector also makes wastegate plumbing easy.
8. I wanted a fun challenging project. Anyone can make the "normal" looking manifolds.
9. It'll work fine for me, pros or cons, it's just what I wanted I guess.
FYI, I just measured the runners and they came out to be what I expected. The rear was around 26.25" and the front was around 28.25". Not perfectly equal and I knew it wasn't going to be when I built it. Its just the compromise I made when I designed it because it gave me easier to work with angles and better clearance. Hopefully it doesn't make to much of a difference.
Can anyone recommend good K-type thermocouples? I want to order the EGT bungs and weld them on the tubes before I weld the tubes to the base flange. However, there are 1/8" and 1/4" NPT bungs and I'm not sure which sensors to use yet for the decision.
11-30-09, 03:24 PM
#17
Looks good man,....but as far as response time....the longer your exhaust runners are the longer it'll take your exhaust gasses to hit the hot side correct? why not chop as much of the exhaust runners our to save on spool time? May not look as artsy..but i bet it'd spool much much faster.. I noticed an incredible difference when I went from my megan racing header to my custom equal length....pics below
11-30-09, 03:34 PM
#18
I figured somebody would ask why I didn't just go with a divided housing. I guess my reasons are...
1. Tial housings are easier/simpler with an exhaust inlet v-band connection.
2. Tial housings are more compact/lighter
4. Tial housings are stainless
5. Tial housing designs make up for that lost response that you see from undivided housings.
a. I don't believe my manifold is perfect in any way, but I do believe (relatively) properly designed manifolds can get away from divided housings to maintain response.
b. Check out the Twins Turbo Jack Mardikian FD manifold.
6. It was easier to design a long runner manifold using a merge collector than dicking around making the bends go into a t4 flange.
7. A merge collector also makes wastegate plumbing easy.
8. I wanted a fun challenging project. Anyone can make the "normal" looking manifolds.
9. It'll work fine for me, pros or cons, it's just what I wanted I guess.
FYI, I just measured the runners and they came out to be what I expected. The rear was around 26.25" and the front was around 28.25". Not perfectly equal and I knew it wasn't going to be when I built it. Its just the compromise I made when I designed it because it gave me easier to work with angles and better clearance. Hopefully it doesn't make to much of a difference.
Can anyone recommend good K-type thermocouples? I want to order the EGT bungs and weld them on the tubes before I weld the tubes to the base flange. However, there are 1/8" and 1/4" NPT bungs and I'm not sure which sensors to use yet for the decision.
1. Tial housings are easier/simpler with an exhaust inlet v-band connection.
2. Tial housings are more compact/lighter
4. Tial housings are stainless
5. Tial housing designs make up for that lost response that you see from undivided housings.
a. I don't believe my manifold is perfect in any way, but I do believe (relatively) properly designed manifolds can get away from divided housings to maintain response.
b. Check out the Twins Turbo Jack Mardikian FD manifold.
6. It was easier to design a long runner manifold using a merge collector than dicking around making the bends go into a t4 flange.
7. A merge collector also makes wastegate plumbing easy.
8. I wanted a fun challenging project. Anyone can make the "normal" looking manifolds.
9. It'll work fine for me, pros or cons, it's just what I wanted I guess.
FYI, I just measured the runners and they came out to be what I expected. The rear was around 26.25" and the front was around 28.25". Not perfectly equal and I knew it wasn't going to be when I built it. Its just the compromise I made when I designed it because it gave me easier to work with angles and better clearance. Hopefully it doesn't make to much of a difference.
Can anyone recommend good K-type thermocouples? I want to order the EGT bungs and weld them on the tubes before I weld the tubes to the base flange. However, there are 1/8" and 1/4" NPT bungs and I'm not sure which sensors to use yet for the decision.
Looks good man,....but as far as response time....the longer your exhaust runners are the longer it'll take your exhaust gasses to hit the hot side correct? why not chop as much of the exhaust runners our to save on spool time? May not look as artsy..but i bet it'd spool much much faster.. I noticed an incredible difference when I went from my megan racing header to my custom equal length....pics below
thewird
11-30-09, 05:19 PM
#21
Once I get some real world testing in, I plan on getting the turbo coated for the reason of keeping the heat in. I don't want to drop $200 on ceramic coating before I know the welds/manifold is certain to hold up to abuse.
12-22-09, 12:39 AM
#25
Old [Sch|F]ool
I'm certainly not a fluid dynamics expert, but I would assume you wouldn't want the need to accelerate the mass of air that is stagnant when the gate is closed. The longer the runner, the greater the mass of air that needs to begin moving in that direct when the gate begins to crack open.
Interesting, that.