External Wastegate, Can Swapping Between Screamer And Plumb Affect The Tune

[stump_69]

Alright guys, I tried searching couldn't find an answer for what I was looking for.

I'm going to run an external gate on my r33, I'm wondering if swapping between plumbing back and running screamer will it affect the tune?

I'd run screamer usually but if I run into trouble with the popo I obviously would have to plumb in.

Everything would be v band to make life easy between swapping a plumb pipe in or swapping to a screamer with a blank on the dump.

Would swapping between the two affect the way the car drives?

[Hanaldo]

Yep.

[Risking]

Merge the two a decent length down the exhaust and make the merge angle blunt as possible. It shouldn't effect the tune a great deal if the merge is okay.

I know there is guys who have back to backed with external gates and reckon they gain hp venting to atmosphere. I'd like to see how the merge was done in those examples

[Don Dada]

I say yes as back pressure will increase with the plumb back......How much of a difference??? I dont know

[ARTZ]

I didn't notice any difference plumbing mine back in at the cat..

.except the car is a shit load quieter and more enjoyable to drive now...screamers get boring real quik n a street car and the disadvantages far outweigh the benefits

[abr33]

Do you have any idea how much the max fine is for a screamer in NSW? If you did you wouldn't risk it!

[hypergear]

Probably not much in terms of tune. How ever the shape of the curve do appears to be pointy after 6500RPMs while plumb back rounds off.

[Risking]

  On 03/02/2013 at 4:35 AM, Don Dada said:

I say yes as back pressure will increase with the plumb back......How much of a difference??? I dont know

If back pressure increases in the exhaust its due to the merge of the two gases not being correct. Not because the waste gate is plumbed back

[MrStabby]

  On 03/02/2013 at 6:33 AM, Risking said:

If back pressure increases in the exhaust its due to the merge of the two gases not being correct. Not because the waste gate is plumbed back

If you plumb the waste gate in, you're pushing more gas down the exhaust, so it will always increase back pressure, even if the merge is perfect. If the exhaust is properly sized the increase will be negligible. If its too small, it will be significant.

[Risking]

The ammount of exhaust gas being bypassed on boost is not that great compared to the ammount required to drive the turbine.

Years ago I did a back to back on my race car with internal GTRS turbos and then the same turbos with external gates/screamers and welded up internal flaps. Made no power differnece but boost control was more steady over a long period (say ec main straight and Bathurst)

We ran it on the dyno twice and the tune was the same. All the lambda logging was the same too. Only differnece was the boost was a steady 28psi instead of a slight wave from 28-30psi.

A waste gate merged at 90deg to the main pipe or even 45deg to the main pipe is not much good but is the normal easiest way to do it.

You won't notice squat difference driving it around on the road if the merge is good.

[ARTZ]

Mine merges into the front of the cat body. So a 3inch front pipe and 2 inch screamer enter a 5inch body cat seperatly then exit into 3.5 inch exhaust...sound is sex on boost too...

[ARTZ]

Mine merges into the front of the cat body. So a 3inch front pipe and 2 inch screamer enter a 5inch body cat seperatly then exit into 3.5 inch exhaust...sound is sex on boost too...

[STATUS]

depends on power and exhaust size, regardless of merge type if the sizing is marginal your in trouble.

[Risking]

The thing to look at is surface area not diameter.

Your 3in exhaust is 7.06in

Your 2in screamer is 3.14in

Total surface area of 10.20in

A 3.5 system has a surface of 9.62in

I can't see that being a problem as a 2inch screamer pipe is way overkill and you wouldn't be anywhere near its capacity.

Most 1.5in gates are adequate

So 3inch at 7.06in

1.5 screamer at 1.76

Total of 8.82in surface area

A 3 inch exhaust would Sufice and not be a restriction at most people's level if the merge is right

We've regularly used 1.5in gates on 400-450kw engines with no problems so I highly doubt the 1.5 screamer is at capacity on most people's 300ish kw setups

A 3.5 inch exhaust (which is typically what we use for anything 400kw +) would have a greater surface area than the dump and screamer pipe. It couldn't possibly be a restriction if the merge is done right.

My math might be off having done it on an I phone calculator but it appears correct.

[luke gtr]

area of a circle app(android)ftw!

twin 3" exhaust, nearly identical to 4" single.

also consider what youll use the car for.

alot of tracks in motorsport dont allow gate.

and you may have to run 2 tunes to make the most from it.

[34GeeTeeTee]

I run mine both ways, no problem....

[luke gtr]

  On 04/02/2013 at 11:15 AM, 34GeeTeeTee said:

I run mine both ways, no problem....

so, you swing both ways?

[luke gtr]

Ask your tuner about tunes.

I remember talking once to dvs jez, and he didn't sound confident on tuning a screamer for 95octane.

if it didn't make a difference, it wouldnt matter.

[Hanaldo]

  On 04/02/2013 at 11:15 AM, 34GeeTeeTee said:

I run mine both ways, no problem....

The Haltech would adjust for it no problem man.

How my old tuner explained it anyway, I asked if it could be done and he said with the Nistune it's a bit difficult but with something like the Link it would be easy.

[Lithium]

I had run both with my GT30R + RB25 combo ages ago when I had external wastegate and it made no real difference to boost control or power.