getting tired of atmospheric wastegate, but worried about power loss

[turboglenn]

Anyone here ever go from atmospheric dump to re-routed? I ask because i've wanted to quiet her down for a while now but the only thing i found on google were people claiming to have gained 30 - 50hp by going to an atmospheric dump, but nothing about losses from going the other way. So i'm hoping some of you can give me some input..

My setup i sas follows for exhaust

T-netics t3 style cast mani, ts 5 bolt turbine housing with stage III wheel. 2.5'' DP with no kitty, then straight through a thermal R&D cat-back

How much do you guys think i may lose by routing it back into the DP?

I could make a 3'' DP if i wanted and have some material in SS but it's rather4 thick walled for my likings.. I'm just to the point where i'd really like to hear more of what's going on in the engine and the bay (and anything else around for that matter ) So far the only way to make it softer is to turn the boost up (which is fun ) but ultimately i'd love to not even hear the WG for a while just ot see how i like it but i will not sacrifice anymore than about 5 - 8hp for the cause....

Gimme your thoughts please (but experience would be more helpfull )


Oooops, forgot i posted the same thing last year or so, feel free to delete or start a new convo, let the mods decide

 

[LiquidX]

IMO I think it would only become a power deterrent if the angle at which the re route enters causing a lot of turbulance on an already restrictive exhaust. The amount of exhaust gasses being pushed out of the wastegate will make a difference on that too.

I would say that if you could get a larger downpipe that would help out any possible issue that would come up.


You could have your dump re routed in a preferred location entering right at the down pipe bend or further back. Downside is you'll have more pipe and the angle on the dump tube may not be the best for exhaust travel. If you do decide this however, keep it wrapped so the exhaust will be moving as fast as it can to get out of the small diameter dump pipe.

 

[ToughTalon]

I cant find the data to back up my claims right now but from what I have heard, it is possible to gain power if you re-route the waste-gate dump into the exhaust. My bro is a big Honda guy and he said there were a few guys on Honda-tech that did a waste-gate re-route and they ran the dump along the down pipe until the rear of the engine and tied the waste-gate in there. So that essentially gained a tuned length waste-gate exhaust they claimed to have gained power.

This is merely food for thought. I am currently enjoying my first vacation in years so when I'm not sitting on the beach I can get more info from my brother if you would like.

 

[El Cuervo]

Hey whats up Glenn! Finally getting some time to work on your car??
I've posted here before about my experiences with the stock o2 housing, recirculated o2 housing, dump o2 housing, external dump o2 housing and now I'll be running an external recirculated o2 housing.
I don't have any dyno sheets or any kind of data like that. What I can tell you though is that the biggest difference was from a stock o2 housing to an internal gated ss recirculated o2 housing. I'm comparing these 2 because they are the closest on design. I was having boost creep with my stock housing. This was after my 3inch exhaust. I swapped it for a tubular internal recirculated o2 housiing. I did gain a very little but noticeable spool. In other words. Turbo response came in sooner. This is on a 14b. Not just that but the housing seemed to have as they say: "cure my boost creep". Or so it seemed. I then decided to go internal dump. There wasn't any difference at all. Maybe a slightly faster turbo response. But maybe. One thing that I gained though was the infamous sound. I did like it at first. After a while it got very annoying. I then got an ebay external dump with a cheap wastegate. [I had to unhook the wastegate arm. The one that you fixed the other day]. Well I went external dump. I did not notice any difference at all. The sound just changed a bit but it was annoying as well. After 2 months of so, i decided to go back to internal gated recirculated o2 housing. I bought a mid steel. Didn't want to spend too much since I knew that I would be going external gated recirculated. Well, I did noticed a very slight decrease in turbo response. Very little if any. The same that I could have noticed when I went recirculated to dump but backwards. I did get rid of that nasty sound. Thats why I had asked you if you could build me a resonator to help with the noise. Now I'm going external again but recirculated. This wil be my last o2 housing. I'm getting sick of swapping them all the time.
As soon as the turbo is done, I'll let you know if I noticed any difference. The thing here is that I was running a 14b at 15 psi. Then I went back to stock boost level which in my case was at like 8.5 to 9 psi.

 

[black_gst]

i cant comment too much on power difference because im still tunning my talon and i had it dumped on my old gst but honestly i dont think there is much if any power difference... i need to get rid of the muffler thats on my talon because it necks down to 2" in there and my gst had the greddy SP exhaust which was more free flowing then what im running now.

but any way heres a pic of my custom recirc. i just bought a flex pipe to add to this because it doesnt seal so well i keep blowing out gaskets where the WG bolts to the mani

 

[-red97rum-]

Well I just recently went from a recirc setup to an atomosphere dump and I can't EFFING stand it. I will be putting my recirced setup back on asap as the external dump is only temporary. I didn't feel any increase in performance and honestly my car felt a little bit better recirculated. It could just be I'm not used to hearing the dump..

Hey Adam, my setup looks very similar to yours! Who would have thought

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[black_gst]

^ what are the odds of that

 

[2gGSX]

I have a slip fit recirculation tube with my PW46 gate and I'll hopefully be dynoing sometime soon. If I can adjust it without burning myself too bad, I can try to dump my wastegate and see if it pick up any power.

In my opinion however, I don't think it makes a difference unless you majorly screw up the design and somehow create significant exhaust backpressure post turbine-outlet.

 

[clockworktoy]

No differences other than noise.

 

[turboglenn]

when it first started being soimething i thought of doing i googled "going to atmosphere open wastegate" and got all kinds of claims from a minimum of 17 to about a max of liek 48-50 HP with 3inch DP and a one inch dump

I feel more confident in taking the time to do it hearing from you gusy that going back you didn't notice a huge loss, because you know how some people mak eposts, lord knows what the metal state of the posters were, ould have been a hundred horse gain with a CAI

 

[pneumo]

Speaking of questionable eposts, I personally saw a honda turbo setup that had the external wastagate pointing at the engine block. There was no dumptube! The exhaust coming out of the wastegate just hit the engine block and stayed under the hood!

I just thought of that when ToughTalon said that honda owners gain power when recirculating the exhaust. do'h!

I always recommend to my friends that an external dump should extend at least below the crossmember so exhaust gas doesn't get sucked in under the hood. Have you tried a motorcycle silencer on the dumptube?

 

[habitatguy187]

There was an interesting post here over the winter with a link to a srt4 where the owner did before and after dyno sessions. He first dyno'd with it vented and then used the exact same o2 housing but just extended the dump tube to around where the downpipe ends and the catback begins (no caty). He lost 39whp by recirculating it, and it looked like it was done very nicely and that there would be very little exhaust turbulence.



EDIT: Found it, but the pics have been removed, shame cause that was the best part.

http://www.srtforums.com/forums/f24/tale-dump-tube-different-approach-power-loss-perfection-315402/

 

[turboglenn]

yea, that was the ONLY post i found where it w3as tested backwards instead of going from recirc to open and i don't wanna lose 20hp. I'm not pressing every componenet to the edge for every last ounce but i don't want to either, and if i'm going to loose 30+ HP i don't wanna stress other parts any harder trying to get back what i had to begin with

 

[habitatguy187]

I think that external dumps are very beneficial once you reach a certain HP level. Check out this post on exhaust size vs. hp -

okay, I found the article by David Vizard, and it was actually in Super Chevy magazine. It's a long article, so I'll supply you with his exhaust math below:

according to Mr. Vizard (who's theories I happen to value) you need to flow 2.2 CFM (cubic feet per minute) of exhaust per 1 HP. Therefore you first need to know what your flywheel HP is, and multiply it by 2.2

So for an example if your engine produces 500 HP at the crankshaft, then that's 500x2.2=1,100CFM. Now remember that because you're using dual exhaust and therefore will have two exhaust pipes (left and right) then you need to divide this total CFM figure by2. So that's 1,100 CFM cut in half.... or 1,100 divided by 2=550 CFM. So you'll need an exhaust pipe diameter that will flow 550 CFM. with that in mind here are the pipe diameters and their flow rates (according to Mr. Vizard)...

2.5" diameter=560CFM

3" diameter=672CFM

3.5" diameter=784CFM

4" diameter=896CFM

so just do the math above using your engine's HP and you'll be able to determine how big of an exhaust pipe diameter you'll need. I hope this helps you.

or

In general 1 inch Hg backpressure = 1 HP lost

For reference, we have the following conversions factors:

1 ATM = 14.7 PSI = 76 cm of Hg = 29.921 inches of Hg = 1.013 bar


So do a little more math and and it wouldn't be too far off to say that a 500 hp engine could see as much as 20% power loss from a single 3" exhaust.

 

[pboglio]

On Subaru's, there is indeed a pretty decent power improvement due to the shared turbine & internal wastegate exit areas. On a DSM I don't see it happening as the merge is designed pretty well and the flow losses are minimal.

As a data point, my buddy was running some popular brand of 02 dumped housing on his EVO, then he swapped to a Megan 02 housing that is internally routed. No difference in peak power on the datalogger. This was at the 320 w.h.p. range. He thought he was going to lose power, and I just laughed cause I knew the external dump wasn't doing jack for his car, which I was right.

 

[turboglenn]

well, I'm going to play it safe and assume that with the 431 horses i made on e85 and the 503 it made with the laughing gas that i'm going to suffer a loss with my 2.5 inch DP if i re route back inwince the wastegate is effectively turning my DP into a 3incher when it opens (i'm sure some one will correct that math so forgive my "rough" estimate)