Confusing Exhaust Sizes

[Manuel Kasko]

Hey guys,

Long story short is I have taken my exhaust off to try get its measurements and work out what could be a restriction at 250rwkw.

I do not understand the results and where to go from here. The dump results confuse me and after the muffler to the cannon is an odd number.

To me the results are all over the place.

Results were acheived by either measuring the circumference and using an online calculator to get the diameter or measuring across the exhaust and just getting the exact diameter.

Cat pipes = 2.5inch (calculated by circumference)

Cat flange = 3inch (exact diameter)

Dump = 3.35inch (exact diameter)

After cat to muffler = 3.5inch (calculated by circumference)

After muffler = 3.88inch (calculated by circumference)

[RRob]

Throw a light down the rear muffler. Have a look inside.

[Manuel Kasko]

Have a look at?

[Piggaz]

See if it gets smaller... Ie a restrictor.

[MrStabby]

AFAIK they usually rate stuff by internal diameter not external diameter, so the pipe wall thickness will be skewing your results. Your cat looks like the problem with those 2.5in pipes. If its not already a metal matrix 100 or 200 cell one, around 4inch core, you'll probably get good results from a change there.

[Manuel Kasko]

It's gutted at the moment so as free flowing as it can get. Would the simple fact of it being a step down to 2.5 be a restriction?

So should I go shine a torch down the cannon?

Is that what you mean by shine it down the muffler

[Sinista32]

Hey Daniel - the first is a decat pipe 3" the second cat in the photo's i sent is this -> "metal matrix 100 or 200 cell one, around 4inch core, you'll probably get good results from a change there"

As I said earlier in another post on this subject in the ACT section. Cats are genrally not the issue in restricting air flow (that is if they haven't collapsed). The muffler is

All this stuff about Catalytic converters and cfm ratings is mostly BS from people who wish to sell you there product.

Decat is obviously better as it has NO internals so absolutely no issue - EXCEPT it breaks EPA regs.

@250 kws with your decat (cat with the guts ripped out) and turbo is NOT your issue. Add 100kws to that and then start thinking about restricted air flow.

I'll go measure both internal diameters if I really have to. Tis better if you just come check them both out.

[Manuel Kasko]

Will organise to come check them out possibly this weekend. My main thought was the whole exhaust ranges from 2.5 inches to close to 4 inches at the end.

Gases flowing from the larger dump and hitting the cat that has pipes going into that are 2.5 inches would have to restrict right?

Or should I be focusing on getting rid of my muffler and stupid cannon and going a different route?

[Sinista32]

True it's a science I dont understand either.

Logically the best system would be the same internal diameter from inlet to outlet.

Spose what I am saying is I dont think your pulling and pushing enough air for it to be an issue. Not yet any way...

[Manuel Kasko]

Hmmm not sure what else would be restricting my setup compared to all the other hypergear guys.

They all seem to be making the same power or better on lower boost. Everything else on my setup is similar or better then what others are running. Only thing I haven't touched is this exhaust.

Possibly this muffler and cannon then?

I'll take it for a brap around the roads with and without the cat etc and see if I find a difference

[Sinista32]

I'd suggest to chat with your tuner. Do some testing with him.

I'm not smarts in this area so I wouldn't listen to me

[Grimesy]

Why dont you drop the exhaust from the cat back and test to see if it is creating a restriction.

It would show on a dyno if it is the cause of the restriction. I thought hypergear recommend tuning like this first? Also are the other results on the same dyno?

[Manuel Kasko]

Not on the same dyno which I understand can vary a fair bit. ACT is organising a dyno day so I will take it to this to test both variances I guess.

When we were tuning it was way to late to test without a cat etc.

[Frosty]

what makes you think you have a restriction in the exhaust? anything under 300kw your not flowing enough for any bigger than 3" as a start! this has been proven a 100time over

[Manuel Kasko]

Just the fact without the cat, muffler it is crazy loud.

Then when you chuck it all back on its fairly quiet in comparison.

Less noise = more restriction?

Also that I feel with my setup I should be making more power.

Or at least the same power on less boost.

I guess I should wait for this dyno day so then I have 2 results to compare

[AngryRB]

the cat is the problem, get a 100cell one that has no flanges at all, can send you some pics of mine if you want, its proven system.

[Manuel Kasko]

I could also just be paranoid

But when someone like Birds makes 260rwkw on like 16psi I think it was.

With a return flow intercooler and using the stock turbo housing with SS1PU internals

Something has to be wrong with my setup.

[Manuel Kasko]

My results

Other results

intake pipe makes abit of differences to response. here's one more result from a customer's R34 skyline running SS1PU. made 255rwkws @ 16psi with 2psi creep mid range. This car's also runs a return flow cooler that get abit hot. With a proper cooler at 20psi it should be getting pretty close result as my test car.

There has been a recent FNT angle update, might affect tinny bit in response but not power wise.

Another results on an SR20

Here it is. SS1PU internally gated bolton version for S13 SR20det non vct.

The thin red line is on stock cams, while the thick red line is on big Tomei Pro 270 dur cams which made it bit laggy. The tune is based on pump 98.

The car's not 100% done at this stage, my expectation sits around the 280rwkws with bit more boost once all finished.

[Frosty]

ok so what i get from that reply is that you made a little less power with the same turbo so your assuming there is a flow issue?

[Manuel Kasko]

less power with more boost.