Just wondering if using crushed bends on the dumptube will have any serious downfalls. I understand mandrel bends would be better for flow reasons, but I can't weld and my dumptube needs to have quite a few technical bends for clearance purposes. Also I can have it crushed bent for about half the cost. Suggestions? Btw, I'll be runnin no more than 12 psi, if that matters at all.

 

get an elbow...and use a long flex pipe...

 

get a flexible exhaust pipe from autozone or advance

 

Only thing I'd be worried about is the flex pipe not keeping it's form, basically I need something that won't move around, plus sooner or later I thought about runnin it closed loop, I'm not sure if you can weld the flex pipe.

 

No you cant weld the flex pipe. You can get your downpipe crush bent but you will have to understand that max power will not be realized due to restriction, even on 12psi. Crush bending can reduce a pipe significantly of the bends are tight. If you are on a tight budget and need the car running then get the pipe crush bent. The only upside to this decision is knowing you will make more power once you decide to get a proper downpipie made.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by msmotorsports &raquo;</TD></TR><TR><TD CLASS="quote">No you cant weld the flex pipe. You can get your downpipe crush bent but you will have to understand that max power will not be realized due to restriction, even on 12psi. Crush bending can reduce a pipe significantly of the bends are tight. If you are on a tight budget and need the car running then get the pipe crush bent. The only upside to this decision is knowing you will make more power once you decide to get a proper downpipie made. </TD></TR></TABLE>

he's asking about a dumptube for the wastegate, not a downpipe. i honestly don't know how it would affect boost control, that is all a wastegate does anyway. i guess if you can hold your boost steady, then it's fine.

 

it wont be a problem.

think about it...once air is leaving the wastegate its already done its purpose. the wastegate has opened up to bleed off boost....the dumptube just gives it a place to go and aims it that way.

you'll be fine.

 

You do want the lowest amount of resistant. e.g... 38mm vs. 35mm, the 38mm is less of a constriction, and there would be less of a pressure drop. Then you can compare the typical runners in some of these log mani (1.5 diameter with a gracious 6" radius been)... they have a L/D of 8 (meaning, it will take 8 times the length of the diameter of the tube to recover the pressure loss and get back to laminar)... compared to a mitred 90 deg bend, which has a L/D of like 60.

But then again, it's all relative.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Mr. Vapor &raquo;</TD></TR><TR><TD CLASS="quote">it wont be a problem.

think about it...once air is leaving the wastegate its already done its purpose. the wastegate has opened up to bleed off boost....the dumptube just gives it a place to go and aims it that way.

you'll be fine. </TD></TR></TABLE>
Guess that's what I wanted to hear... but...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by scartail &raquo;</TD></TR><TR><TD CLASS="quote">You do want the lowest amount of resistant. e.g... 38mm vs. 35mm, the 38mm is less of a constriction, and there would be less of a pressure drop. Then you can compare the typical runners in some of these log mani (1.5 diameter with a gracious 6" radius been)... they have a L/D of 8 (meaning, it will take 8 times the length of the diameter of the tube to recover the pressure loss and get back to laminar)... compared to a mitred 90 deg bend, which has a L/D of like 60.

But then again, it's all relative.</TD></TR></TABLE>

So, basically if I increase the length of the dumptube, this will make up for the shitier flow of the crush bends??? Trying to relate...(I'm not an engineer)

Also, if I opt for 1.75" diameter crushed-bend piping rather than the standard 1.5" (mandrel bend piping) would this roughly amount to be equivalent, considering the larger "crush diameter" would decrease to the mandrel size at the bends???

I might be over-analyzing this a little too much....Just help me GO Faster on my stock block without blowing **** up

 

Okay I'm kind of a dumbass so lemme see if I understand this.......

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by scartail &raquo;</TD></TR><TR><TD CLASS="quote">You do want the lowest amount of resistant. e.g... 38mm vs. 35mm, the 38mm is less of a constriction, and there would be less of a pressure drop.</TD></TR></TABLE>

I thought with higher pressure drops you would have greater flow, but maybe I am mistaken.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by scartail &raquo;</TD></TR><TR><TD CLASS="quote">Then you can compare the typical runners in some of these log mani (1.5 diameter with a gracious 6" radius been)... they have a L/D of 8 (meaning, it will take 8 times the length of the diameter of the tube to recover the pressure loss and get back to laminar)... compared to a mitred 90 deg bend, which has a L/D of like 60.</TD></TR></TABLE>

Here you explain flow characteristics of manifolds. Is the dumptube really as important as all this? The end result is less flow which would theoretically restrict the air vented from the manifold which would result in more boost correct? This is of course assuming that the dumptube is that much of a restriction. I don't really know if it would or would not be. Maybe you can explain whether it would or would not be. Just for the sake of my curiosity.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by scartail &raquo;</TD></TR><TR><TD CLASS="quote">But then again, it's all relative.</TD></TR></TABLE>

You mean there is no such thing as absolute flow?

 

i already have like a 8" long 1.5 diameter dump. i dont have any bends, instead i had it cut and welded to create the bend i needed. im going to extend it out of my engine bay with flex pipe. im not worried about using flex pipe.

even if you loose a little flow due to bends/material used, im going to say that you will make it up in power gained by not having your exhaust dumped in your engine bay and run the risk of sucking it back into the engine

 

I have a crush bent dump tube.. its 1.5" diameter and has 3-4 minor crushes to make its way to the ground..

I had no problems holding boost steady at 4-6 psi

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by KeyserSoze &raquo;</TD></TR><TR><TD CLASS="quote">Okay I'm kind of a dumbass so lemme see if I understand this.......

I thought with higher pressure drops you would have greater flow, but maybe I am mistaken.

Here you explain flow characteristics of manifolds. Is the dumptube really as important as all this? The end result is less flow which would theoretically restrict the air vented from the manifold which would result in more boost correct? This is of course assuming that the dumptube is that much of a restriction. I don't really know if it would or would not be. Maybe you can explain whether it would or would not be. Just for the sake of my curiosity.

You mean there is no such thing as absolute flow?

</TD></TR></TABLE>

I'm not an expert by any mean, but I do have flow experts that work in my department... :-D They know their stuff.

A pressure drop would mean that you slowed down. You don't want to slow down. A good example is the log manies versus the sidewinders or something like... The sidewinders have nice long runners, so after exhaust makes the turn of from the head, it picks up speed along the straights.

Back to wg's... the 38mm has a bigger openning than a 35mm. There is smaller of a pressure drop and less of a resistant. The exhaust gets out quicker.

But for our purposes (at least mine for sure, I'm after wimpy HP)... It doesn't matter much.

Oh... BTW... For my setup, I just have bend off the wg, and I used an flex pipe (from autozone) to the run the rest.. :-D

 

35/38mm wastegate running just 12psi should pose any issues if you run crushed bends. The only issue it can cause is possible boost creep, but people rarely have issues with internal gates running more boost than what you will. It has more to do with where the WG is placed on the manifold, than how restrictive it's dumptube is.

Anyways, a dumptube is easy and cheap to remake, so go with whatever you can if you're in a bind or whatnot, then fix it later (very soon).

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by GaRn &raquo;</TD></TR><TR><TD CLASS="quote">I have a crush bent dump tube.. its 1.5" diameter and has 3-4 minor crushes to make its way to the ground..

I had no problems holding boost steady at 4-6 psi</TD></TR></TABLE>


I had an almost identical setup on a 38mm tial, and it held boost fine at 10psi. I originally had a flextube dumptude and had to remake it becaue it caused boost creep.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by scartail &raquo;</TD></TR><TR><TD CLASS="quote">

I'm not an expert by any mean, but I do have flow experts that work in my department... :-D They know their stuff.

A pressure drop would mean that you slowed down. You don't want to slow down. A good example is the log manies versus the sidewinders or something like... The sidewinders have nice long runners, so after exhaust makes the turn of from the head, it picks up speed along the straights.

Back to wg's... the 38mm has a bigger openning than a 35mm. There is smaller of a pressure drop and less of a resistant. The exhaust gets out quicker.

But for our purposes (at least mine for sure, I'm after wimpy HP)... It doesn't matter much.

Oh... BTW... For my setup, I just have bend off the wg, and I used an flex pipe (from autozone) to the run the rest.. :-D </TD></TR></TABLE>

Ahh, you know what I think I was confusing when you were saying "pressure drop" with psid. In essence from what I understand, flow is only possible due to a differential pressure. With no differential pressure you will have no flow. So the crushed bend produces more backpressure and less psid across a particular section and thus the end result will be less flow. You are saying (and correct me if I'm wrong as it sure as hell wouldn't be the first time) that the pressure drop that one would want is the lowering of the pressure on the entry/exit/duration of the bend. This lowering of pressure before/during/after the bend is what allows for better (well maybe not better, but more) flow. If this is what you meant then it makes perfect sense. To my simple brain anyway.

 

Dump tube theory follows the same theory as downpipe theory. Just think about it and you will realize this has to be the case.

 

i dont think that there is

1. enough pipe, bends or air flow to make a difference in a dump tube being mandrel vs crush
2. there is barely any bends, that a crush would be that much less supeior.

maybe what .25% of an HP

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by KTeller8 &raquo;</TD></TR><TR><TD CLASS="quote">i dont think that there is

1. enough pipe, bends or air flow to make a difference in a dump tube being mandrel vs crush
2. there is barely any bends, that a crush would be that much less supeior.

maybe what .25% of an HP</TD></TR></TABLE>

agreed