goofygrin

iTrader: (5)

I had a high flow cat but stumbled upon a test pipe, so I'm playing with it to see if it makes a LOT of difference (the jury is still out). It sure smells worse and is much louder in the cabin though.

When I crest hills in traffic, I let off the gas in case there's a cop with a laser and with the high flow cat (or stock no flow cat), when I let off the gas the car would decelerate a decent amount (3-4 mph) just from engine braking. Going down the ramp in the parking garage at work I'd slow down a bit too.

Now, it feels more like an automatic and the car seems to coast more, not slowing down as much.

Is this everyone else's experience?

AJsGenerX

iTrader: (6)

I'm assuming its because there's less back pressure with the test pipe and this is why you are experiencing this.

Spy007

Ive got a HFC and even when I was stock, letting off the gas to decel seems the exact same. It almost seems like it kept on cruising as if I hadnt let off the peddle until a few moments later (20-30 seconds) it finally kicked off and started to decel me. I just attributed it to the drive by wire.

goofygrin

iTrader: (5)

This is what I was figuring, but I didn't think it would make a difference that was noticeable in 2 days.

This sounds like rev-hang to me. I'm talking at low throttle situations, not WOT (where I get the standard rev-hang BS too).

UT_Evo

iTrader: (5)

That's a magical test pipe! No idea why that would happen, I can tell you from testing my friend vs me who had the same set ups just one with test pipe and one with HFC I had about 10-12 more hp than him, but that was on an VIII with the older less-flowing high-flows. The newer ones supposedly flow almost as well as a test pipe.

But off throttle I can't think of why it would be different... Back pressure maybe?

goofygrin

iTrader: (5)

Maybe I'm just high from the gasses

Spy007

So was I (the low throttle part). Im refering to just highway cruising at 75mph... then letting off the gas to coast to 65 with the lower speed limit... and it doesnt seem to let off the gas as much as any car ive ever been in.... till it hits that "hump" and finally lets go.

I get the rev hang more often when im backing up and just creeping back, but it seems to want to rev higher for a couple seconds even after taking my foot off the gas and clutching in.

UT_Evo

iTrader: (5)

Best response so far was your own.

Honestly though, it probably doesn't pollute "that" much. I had the test pipe in my 8 (so none of the fancy 21st tech keeping my fuel system clean ) and they ran the old fashioned sniff test on the car. I passed. I was on the high end of the passing range, but I still passed within Utah limits. So much so that they got confused and had a hard time trying to find my "cat" for the visual inspection part.

I think the guy commented that I polluted about as bad as a car from the 80s?

steinvb12

iTrader: (4)

A test pipe will make a BIG difference when you get a tune and turn up the boost! You need that extra flow when you run more boost.

goofygrin

iTrader: (5)

I is got custom accessport dyno tune (with the HFC).

SilverEvoX

iTrader: (2)

It should be slowing less because of the backpressure man. I noticed mine is better than stock cat vs test pipe. Also alot less engine breaking I noticed running with ASC off during normal decel. I still have a little hump at about 3400rpm that it really slows from there down