angela_itr

My turbo kit came with a small dump tube... I mean really small, both in length and diameter. In fact I feel that it is quite inadequate after seeing this thread:
https://honda-tech.com/zerothread?id=1271237

The tube is the same diameter to match up to the w/g flange, so would there be any benefit to fitting a bigger dump tube? I would've thought that the flow would only be as good as the narrowest point in the system, eg the w/g flange... am I mistaken? Also I guess its not long enough, so the hot gases are hanging around in the engine bay.

What kind of problems/symptoms might this cause? Pic below:

raene

I'd be more concerned about the location of the wastegate than the size of the dumptube. Your setup is basically a log manifold which will help with that placement but I'd still much rather see a central wastegate at an equal angle as the turbo flange.

You actually want a tube that increases in diameter as it distances itself from the wastegate flange. The exhaust will escape the manifold through the wastegate and it will be pressurized at the wastegate exit somewhat less than the manifold pressure. How much it is pressurized depends on the size of the dumptube and the pressure in the exhaust manifold. This gas will want to expand as it travels away from the wastegate and lower its pressure, and as it expands, it will IMO accelerate, which will help draw exhaust out of the wastegate by lowering pressure at the exit. A constant-diameter dumptube will allow expansion in only one direction with backpressure as the result, and an increasing-diameter dumptube will allow for expansion in multiple dimensions while avoiding much of the turbulence and dirt found in a no-dumptube situation.

Think of a ooogah-horn type of shape, that's what I'd think is "best". A smoothly increasing diameter. The wastegate flange can't be larger than the wastegate valve anyway.

Finland

Are you getting boost creep? If not, then the tube is adequate.

angela_itr

I seeee.... thanks for the explanation

As for the manifold, well had I spent more time reading on HT before buying the Drag kit, I might've gone for something different. I would really love a full race EL manifold but just can't afford it yet.

Is there something inbetween, that moves me away from the incorrect w/g placement but isn't as pricy as a full race mani? I read the recent comparison between log and EL manifolds... what would be a good log mani to go for?

angela_itr

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Boondock Saint &raquo;</TD></TR><TR><TD CLASS="quote">Are you getting boost creep? If not, then the tube is adequate.</TD></TR></TABLE>
I don't think so... with the .4 bar w/g spring I was getting about 5psi on the boost gauge, and with the .5 bar spring it was just over 7psi. Presumably the boost gauge would show the actual boost, whether due to creep or not?

Is boost creep a consistent thing or might it just happen every now and then?

SOHC_MShue

sometimes you will get boost creep if the temperature changes.

angela_itr

lol not much chance of that in the UK... unless its a drastic temperature change downwards!

Actually its just about the first day of summer here today... at last

SOHC_MShue

haha damn late summer.

Finland

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">sometimes you will get boost creep if the temperature changes. </TD></TR></TABLE>

I don't think so. You might see an increase in boost pressure due to a change in air density (cool air is dense), but creep is more of a function of inadequate waste gate, or manifold design.

SOHC_MShue

well i know a lot of people with mbc's complain about how they get boost creep bad sometimes in cold weather.

Finland

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SOHC_MShue &raquo;</TD></TR><TR><TD CLASS="quote">well i know a lot of people with mbc's complain about how they get boost creep bad sometimes in cold weather. </TD></TR></TABLE>

Well, I think you just made the case for air density affecting boost level. Dense air should result in an increased but stable boost level, as opposed to "creep", which is an increased, but relatively unstable boost level.

SOHC_MShue

well some that i've seen have been unstable. Like they will hold a constant amount in warmer weather, but when it gets cold it will spike uncontrolably.

angela_itr

I guess when I'm making "proper boost" I'll be better able to comment on boost creep and spiking

ITSME4G63

looks more than adequate to me, doesnt get in the way of anything, as long as your dump tube isnt in the way of any oil feed or return lines or anythign that would get damaged by ehat, youre straight.