What are your thoughts on this technical type people................

We've got a thread going about this on the MR2 boards, and I was just interested in people's opinions in principle:

 

My downpipe keeps divorcing itself

 

whats the point of this? surely 1 pipe is more restrictive than the other?

 

Looks like a simple wastegate pipe to me, is it not?

 

It is, but it's to be used on the stock internal gated turbo..........

 

benefit as I understand is to separate the main exhaust flow from the wastegate flow, because either the downpipe entry masks the wastegate outlet, or the wastegate flow interferes with the main exhaust flow, causing a flow restriction.. The two are then merged further downstream in a more favourable fashion. There was a similar discussion on scoobynet last year, as some of them suffer similarly with wastegate outlet shrouding in standard form.

 

commonly used on jap cars with the smaller turbos that have that kind of exhaust outlet, seems to have a benefit from tests.

useless on cossies and bigger turbos as the turbine oulet is totally different

 

seen this on a some datsuns to over come echaust flow problems on boost but not sure of the benifits myself.

 

thought about this with the frst and T2

only thing is i thought "screamer pipes" if im not mistaken dont re-enter the exhaust? or is that a different thing

 

Its not a screamer pipe, but similar principal to when people run external wastegates.

Cant run that wastegate pipe as a screamer as it isnt totally sealed from the normal exhaust, so youd sound like you had a leaky exhaust.

 

i know the cossie housing/wastegate is v similar to Lotus T3, and much more efficient than a lot of other designs.

 

Most T25/T28/T3s have exhaust outlets like on RSTs, that need an elbow, and thats when exhausts (or just the elbow) like the pictured one is used.

 

a lot of the gt range have 5 bolt outlet - i know this is diff to RST, but what about T25/T28?

 

Yes, the smaller of the GT range is the same too

 

so what is the benefit of such an arrangement, i kno that a T2 is split like the above one?

 

its will show gains over the standard setup,,, but if these gains are worth the effort is another topic

 

not too fussed, ive got a pair of spare downpipes and 2 spare elbows off the turbo

 

Not really the case now..... used to be the "IN" thing with the Scoobs (It was called a twin dump system). That was until it was accepted that an open mouth, but bigger bore pipe was better.

 

And here's one I prepared earlier showing the difference in the open neck kind.

 

fagin is that just the oem one with the divider removed? did it make any noticeable difference etc etc

 

The one shown is not an OEM downpipe, but the 2005-> oem ones are open neck. That tells you something, if the manufacturer is now using an open neck design. Before the open neck the oem ones looked like that below.


Both OEM - Left one is 2005 onwards (open neck), Right is pre-2005 semi closed face.

I havent personally tested twin dump ones against semi closed faced and open neck ones.

Twin dump ones were supposed to aid spool up and boost control (of certain turbo's).

 

the plot thickens

luckily or unluckily whichever way you want to look at it, the frst has a 90degree elbow there, so i dont think open mouth or semi closed would make so much difference, think ill look into merging the 2 sections of the elbow though, a lot less work than running a seperate waste pipe and judging by those pics youve just shown me, is the way forward

thanks for the pics and info

 

Open mouth and semi-open mouth make a huge difference..... that I have tested!

 

ill take the hack saw and dremel to one of the spare elbows tomorrow then and take some pics,


there wont be any detrimental effects to merging the wastegate and exhaust routes will there?

 

What difference it would make to your turbo application though, I am unable to comment. Nothing tested, nothing gained though!

 

might not make any difference, but if this is the way its developed surely it must be a step forward, im all up for doing cheap small modifications, i feel its little bits that make the difference between to two "similar" spec'd cars

all adds up.................. or so i hope