High flow cat tests comparing run 006 (stock cat), 009 (test pipe), and 011 (Random high flow). The random is a single brick metalic substraite spiral wrap, it is about 4" round. As you can see nothing beats a straight pipe but the Random gets much closer.
Current mods are: 3" turbo back, MBC, stock K&N, and type-S DV. The MBC was adjusted to maintain the same boost with each configuration. (18-19PSI tappering to 16-17PSI).

 

Same test with HP curve.

 

what were the actual gains (very hard to tell from the curves) and A/F ratios of each run?

 

Here is the same data only showing a different 3" high flow cat compared to the test pipe and the Random. These tests, plus my butt dyno definitely tell me that the stock cat costs a noticeable amount of power and throttle response. It also tells me that if you want a cat, get a metallic sub straight like the Random or just use the stock one. Other regular high flow cats do not seem to flow much better than the stock unit. Oh and nothing beats a straight pipe.

 

Wait, where are the 30hp gains people say they get from a turbo-back exhaust and intake (or K&N)???

From the look of those graphs your money is going purely to cosmetic and sound improvements since the power is almost identical on all of them.

wtf.

 

I think the "stock" run is with K&N and turbo-back... He is comparing the results from just the diff cats here.

FB

 

As you can see from the graphs. peak numbers can be somewhat misleading. The average difference from the stock cat to test pipe is about 10 WHP and about the same WTQ. In spots the Random cat is in between the two but usually closer to the test pipe values.

This car is still using the stock ECU with no modification to fuel or timing. There is no significant variation from stock fuel curves 10 above 5k.

Unfortunately I never base lined my car on this dyno, the average EVO dynos 225-230WHP here, these mods showed a 30-35 WHP gain on the Mustang dyno where I did my base line testing.
My last Mustang run showed 268 WHP on a 100+ degree day, on this dyno under similiar conditions (test pipe) I got 260 WHP peak, with the stock cat I see around 250WHP peak, and with the Random cat it's around 255-257WHP.

 

Thats right.

 

Thanks for the info. I like the look of the power difference at 3500 rpms. That really helps in getting the car moving.

 

Oh okay, that's much better news then!

I wish they had a smiley that keels over and dies and then another one rushes over and revives him with good news.

I definitely like those low-end torque gains, but I'm surprised a LESS restrictive exhaust path is yielding more low-end torque.

 

Silver, don't you still have the stock exhuast (muffler) on there?

Tests are often limited by the weakest link, if you still have the stock muffler remember that these gains are just a ratio of the gains you'd expect when you open up the other restrictions. You're biggest bottleneck is probably the muffler now with the random cat or test pipe. With no exhuast, just the cat, random, or test pipe, you get a better picture of just how restrictive each one is. I Did this with my mr2 many moons ago, and thats how I ended up with a 3 inch dump from the turbo to the back of the car, all 2.5 feet of the exhuast. Too much spool and power lost and too much additional weight. I think for track days a 3 inch straight back or dump routed to the side will make great power, and probably sound like a john deer tractor like my 2, but the turbo whistle under boost is intoxicating.

 

These tests were done with a full 3" exhaust system (RMR). Raising the boost a couple of pounds would yield 270-280WHP, with no fuel or ignition modifications. I think thats pretty good don't you?
Especially on a 100+ degree day, even uncorrected it's still 250WHP. I have since gone with an EBC that holds the boost much better and has even better spool response, it certainly feel faster on the butt dyno. We will do more testing soon.
Also keep in mind that the Random cat has a 2.5" pipes, they are comming out with a 3" version soon. I will sell the 2.5" when the 3" is available, there should be a slight improvement with that also.
Any one interested in the 2.5" Random in a few weeks send me a PM.

 

I custom made my 3"random w/hard ends not the swivels that come with the 2.5". Big difference in performance from the 2.5".But now i get a check eng. lite every 400 miles or so.

 

That's interesting, I have had no codes after 1500 miles with the 2.5" pipes. I forwarded this thread to Random, hopefully they can explain why this might be happening.

I think your confusing low end with mid-range. Less than 3K is what I consider low end. More back pressure does help somewhat in that area but turbo spool/mid to high RPMs are usually better with less back pressure.

From what I have seen, a cat back is usually good for about 10WHP, down pipe maybe another 5WHP, the CAT is another 10 WHP, K&N another 4-5WHP, and the DV 2-3WHP. I am about 30-33 WHP above stock right now, that's how it added up for me anyway.

 

Wait why would there be a gain from a DV?? Was your stock one leaking?? I have not had any problems with my stock one yet.

I did the test pipe mod on a completely stock EVO. VERY NICE. about 10+ wheel hp sounds about right. Car does pull much harder.

Eric