HI Guys,I did an exhaust Dyno comparison test on my car today at a great shop,Fluid Motor Union..
They had a Dyno Dynamics dyno which read lower then any other dyno I have been on in the past...I made a thread about that earlier today explaining details of the others dyno numbers..
OK,,I had on my car a Milltek with HJS 100 cell cats rated at 350 HP each which has 2.75 inner muffler piping except of the muffler outlet exit tail pipes ,2.5'' and stock tip size ends,which I cut off and welded 2.75'' piping + tips on to match inner piping.I tested a Fabspeed 2.75'' catless X-pipe against it..It is more of an independent bend from each bank with a window..

The graph with the green one was the first run on the X-pipe when it was just put on cold,,526Hp.
The other graph with the pink X-pipe was the 2nd run ,warmed up, like the Milltek was ran,,517Hp

My Differences in Dyno Numbers

Hey Guys I am at Fluid MotorUnion doing the exhaust swap comparison now. My 100cell Milltek to a Fabspeed catless X.
All I can say it that their Dyno Dynamite dyno in a 4th gear pull is not a happy numbers dyno as compared to the others I have been on. They don't use 3rd because they say it is to violent for the strapping situation.
Ok,, on Protomotive rear Dyno Packs-625, Porsche Exchange rear Dyno Jet-600, Kelly Moss AWD Mustang - 550, And now on this Dyno Dynamics so far 515 before swap.
The graph power curves looked all pretty similar on all the dyno's.
Truth be told.

Pretty nice John. I'm sure you can feel the earlier/stronger tq. It almost looks like the car started pulling back after 5800 or so. Can you data log it? Should have kept going really.

How did you like the sound when you drove off?

Thanks...
To tell you the truth,,It does sound real good but I think it is to loud for me..My daughter seems to think the same..I like the stealth mode better but after I changed the Millteks tail piping size it did sound like a perfect balance.
So,,what happens if I removed the 100 cell HJS ,I think I would pick up close to the catless x-pipe in low mid TQ? I was really surprised on the mid top of the RPM range with how good the Milltek faired..
Who knows ,,I might sell the X-pipe and put the milltek back on..

Remember the Milltek will also get louder if you remove the cats. Try to log and see if it's pulling timing on the pump gas. Or add in some race and see how she feels up top.

They had some sort of data coming from the port plug to the dyno computer/monitor that showed timing,and they said it had no spikes to show it pulling timing?

Do you have a boost map as well?

The green line looks like the boost ramped up earlier and spiked higher (probably due to the higher exhaust flow). People running pump gas are typically limited to a given boost. If the boost spikes and you have to turn it back down in that RPM range, than the gains could be lost.

Later, Steve

Steve the boost ramps and air fuel were almost identical, as I checked that out also.
As you can see then that those big 100cell HJS cats do flow well enough to sustain the top end power,, at my level..

For that difference, I would definitely keep the cats on the car.

Hopfully my 2.5" Fabspeed exhaust with 100 cell cats won't be much of a restriction at my goal of 600whp.

Later, Steve

[QUOTE=sdfdvghzhao;3864214]How did you like the sound when you drove off? [/QUOTE

Great sports car sound/tone but a little on the loud side for my likes,, so far.

Holy crap John you finally went catless! How does the butt dyno feel compared to the Mil? You feel like shes boostin quicker? Throw in a 5 gl drum of 110-112 in her and fill her the rest of the way up with 93. I'm curious of your impressions then.

-Ron

Do you think the Milltek would get that much louder since they are big 100 cats now and being a muffler system??
I don't think it would get any where near this catless Fabspeed..

Ron maybe us old dogs can be taught new tricks...LOL..
It does feel and pull harder when it hits boost but I don't feel a difference in upper end range pull..
But this Fabspeed is kind of loud for me..I will give it a few days..
Hmm...Make Milltek catless or put the big HJS 100 cats on the Fabspeed??

I really don't think I can get use to how loud this system with my driving style in the city....I guess I am getting old...LOL..
Not bad at steady cruising but as soon as you give it any gas it is a sharp powerful tone that I do like except now others do look at the car when I get into the gas pedal and it does get loud inside also..
Decisions ,Decisions....Milltek back on,,or put cats on X ??