No Cat=Sluggish Takeoff?

[TooFastTooG]

Hey guys, just had a question for ya.

I recently drove my friends girlfriends car which was a 97 GST, completely stock. The car felt so much better when leaving from a stop. Now im not talking wot, just normal driving. Basically, it felt alot more "torquey".

Now my 95 GSX which is lightly modded:K&N Air Filter, DejonTool MBC, Autometer boost and A/F gauge, 2.5 Exhaust, Dejon Tool UICP, 1st Gen BOV, Aluminum Intake Pipe, and NO CAT.
My car feels like I need it give it alot more gas to take off and it just feels "sluggish". It feels great top end though. The exhaust was done before I bought the car, and I think it was done cheap, becuase after my downpipe its all 2.5" and no cat.

So to sum it up im thinking that this is mainly becuase I have no cat? I searched and people have problems in midrange but I just want to know if this also effects you from a complete stop too. Thanks in advance!

Edit: I did do a boost leak test a while ago and I found a leak in the biss screw and my stock intercooler piping, both fixed.

 

[4BangR-x]

no cat means no back pressure, in turn it will give u somewhat of a slower take off, but not for long. By 1500 rpm all that lack of backpressure is helping the turbo do its job better

 

[lasertim]

Going without a cat will not cause a power loss in the low end.

 

[4BangR-x]

yes it will, there is NO back pressure, atleast not as much as having a cat will provide.

 

[DSMcrazy3]

Going without a cat will not cause a power loss in the low end.

Yes it will, 4bangR-x said it right. The absence of backpressure will infact take away bottom end power, while providing much better flow for the top end.

 

[lasertim]

no cat means no back pressure, in turn it will give u somewhat of a slower take off, but not for long. By 1500 rpm all that lack of backpressure is helping the turbo do its job better

Explain please.

Dont forget that this is a turbo car which already has a huge "restriction" in the exhaust, meaning the turbo itself. Good thing that restriction makes up for itself in the end

Less back pressure on a turbo car=faster spool which should mean more power sooner.

 

[lasertim]

Yes it will, 4bangR-x said it right. The absence of backpressure will infact take away bottom end power, while providing much better flow for the top end.

This topic has been gone over many many times on many boards. No one really ever comes to an agreement. Please explain to me why a restriction after the turbo can help in any way.

I am not trying to start an argument, just getting your opinion.

 

[Booster-Shot]

All I know is that I have to put on a high flow cat for smog and Im not looking forward to it.

 

[TooFastTooG]

Well I guess we have different opinions, but from what I have read, like said above: No backpressure =loss of power. Just want to be sure of this.

So im assuming that a kinda happy-medium is a high flow cat? What do you guys run? With or without cat?

 

[4BangR-x]

Basically it boils down to this, It doesnt hurt for more then a quarter a second, but its the reason his friends girlfriends car feels faster off the line than his.

Yes the turbo is a restriction, but so is adding a cat to that. Lets say you have these 2 restrictions, a cat and a turbo. Both provide alot of backpressure. Taking away one will reduce the back pressure, thus not allowing the car to get off the line as quick. Is it noticable, apparently. Does it mean your car is slower, NO. It will eventually be rewarded for its lack of backpressure.

By the way...NO cat all the way

 

[TooFastTooG]

Basically it boils down to this, It doesnt hurt for more then a quarter a second, but its the reason his friends girlfriends car feels faster off the line than his.

Yes the turbo is a restriction, but so is adding a cat to that. Lets say you have these 2 restrictions, a cat and a turbo. Both provide alot of backpressure. Taking away one will reduce the back pressure, thus not allowing the car to get off the line as quick. Is it noticable, apparently. Does it mean your car is slower, NO. It will eventually be rewarded for its lack of backpressure.

By the way...NO cat all the way

Very well said.

Heres a question, so would it just as noticable of the loss of top end power by adding the cat as it is by not having a cat in bottom end power. Does that make sense?

 

[DSMcrazy3]

Basically it boils down to this, It doesnt hurt for more then a quarter a second, but its the reason his friends girlfriends car feels faster off the line than his.

Yes the turbo is a restriction, but so is adding a cat to that. Lets say you have these 2 restrictions, a cat and a turbo. Both provide alot of backpressure. Taking away one will reduce the back pressure, thus not allowing the car to get off the line as quick. Is it noticable, apparently. Does it mean your car is slower, NO. It will eventually be rewarded for its lack of backpressure.

Very well said

What do you guys run? With or without cat?

I run with a cat. A real high flow cat. Not a test pipe, I perfer to keep it legal and so should you.

Heres a question, so would it just as noticable of the loss of top end power by adding the cat as it is by not having a cat in bottom end power. Does that make sense?

For me, both were noticable. When I ran the car open headers, I felt a bit sluggish off the line, when I got new piping and muffler put on and closed the exhaust I felt more torque, but seemed to choke in the higher RPMs

 

[4BangR-x]

yes it makes sense and yes you will notice the top end power kinda sag. No cat is a great cheap mod for good speed.

I dont have emissions so I dont care about legality, if i get stopped out in these rural ass area its not for loud exhause or smokey tailpipe. theres plenty of Big'ol trucks that are louder then me!

 

[TooFastTooG]

Thanks alot for all the quick replies, you have anwered my question very well.

Im thinking I am going to get a high flow cat, mostly because it just feels to sluggish for me, and the gst responded very well in the top end as well even for being stock. But also I do have have emissions in my area, and I dont want trouble with that down the road.

 

[DSMcrazy3]

I was talking about staying legal for the earths sake , but the law is a good reason too..Since it's in the earths defense.

 

[Talesin]

Yes, having no cat will reduce your low-end torque/power noticeably. However, as stated above, the added top end more than makes up for it. Anyone with an aftermarket exhaust with no cat, but with a removable silencer can get a similar feeling by adding or removing the silencer, so long as it causes an exhaust restriction.

With the silencer, you get a good bit more low and midrange, but the car chokes a bit at the top. Without, you seem to stumble/amble a bit in the low RPMs, but once you get going, you can just take off like no tomorrow.


As for the green reason to run a cat, that's great. Get the California smog nazis to pay attention solely to what's coming out of the tailpipe, and I'm sure that 90% of the tuner cars equipped and tuned with WB02 will pass with flying colors, while the retards in SUVs will get slapped with 'gross polluter' fines. Sounds like the best course of action to me, at least.

 

[PieEyedPiper]

To be honest guys? Good discussion about the cat vs. no cat.
But I have a different opinion.

a) was it not decided in a bazillion threads that any backpressure of any kind of our cars is not desireable, no matter the RPM range?

b) but most importantly I feel the difference this guy felt between cars is not related to any exhaust component at all - but rather the fact that we was comparing an AWD to a FWD.

It would make sense because:
-AWD is heavier than a FWD
-AWD has more moving parts than a FWD
-AWD has more drivetrain loss than a FWD
-AWD deficiencies as compared to FWD would be most noticable when making the least amount of power. At take-off from a stop sign etc.

Interesting discussion.

 

[TooFastTooG]

To be honest guys? Good discussion about the cat vs. no cat.
But I have a different opinion.

a) was it not decided in a bazillion threads that any backpressure of any kind of our cars is not desireable, no matter the RPM range?

b) but most importantly I feel the difference this guy felt between cars is not related to any exhaust component at all - but rather the fact that we was comparing an AWD to a FWD.

It would make sense because:
-AWD is heavier than a FWD
-AWD has more moving parts than a FWD
-AWD has more drivetrain loss than a FWD
-AWD deficiencies as compared to FWD would be most noticable when making the least amount of power. At take-off from a stop sign etc.

Interesting discussion.

Nice comments, I did not think too much about your last point.

But, I guess its hard to explain what I feel on a message board. I can tell you that I would be able to feel a difference between it just being a little slower then the gst from a stop and what it feels like now, almost "loose".

But I definetly relize what your saying. Thanks for the comments!

 

[lasertim]

To be honest guys? Good discussion about the cat vs. no cat.
But I have a different opinion.

a) was it not decided in a bazillion threads that any backpressure of any kind of our cars is not desireable, no matter the RPM range?

b) but most importantly I feel the difference this guy felt between cars is not related to any exhaust component at all - but rather the fact that we was comparing an AWD to a FWD.

It would make sense because:
-AWD is heavier than a FWD
-AWD has more moving parts than a FWD
-AWD has more drivetrain loss than a FWD
-AWD deficiencies as compared to FWD would be most noticable when making the least amount of power. At take-off from a stop sign etc.

Interesting discussion.

I agree with you 100%. Very well said.

 

[lasertim]

For me, both were noticable. When I ran the car open headers, I felt a bit sluggish off the line, when I got new piping and muffler put on and closed the exhaust I felt more torque, but seemed to choke in the higher RPMs

Are you refering to when you were n/t with this comment? N/T applications are a whole different ball game when it comes to back pressure.

 

[jongreene]

I have no cat on my lightly modded AWD and it pulls hard as hell from take off. I understand what you mean by the fwd feeling more torquey though I think its just because they throw all the power down to 2 wheels and it feels alot more untame.

 

[Sivad87]

Holy mis-information batman!

first off the only engines that truly NEED, as in required to run correctly are 2 STROKE engines! thats why they have the goofy shaped pipes. because it creates a (tuned) backpressure. it makes a wave of pressure come back to keep the A/F charge in the combustion chamber. same with nitro R/C cars. they are 2 stroke.

Now if you look at the whole cycle of a 4 stroke engine there is absolutly no purpose in backpressure. there is a whole stroke dedicated to just relieving the exhaust gases from the combustion chamber. if you have back pressure all it is doing is making the piston work agains itself, and also could leave exhaust in the combustion chamber after the valve slams shut. making it displace air causing less power.



Im very sure that all you are feeling a difference between the cars is in the drivetrain, and engine condition. the gst could be in better condition than the gsx.engine could be cleaner. just in general running "better" but not neccisarily faster (because of mods)

there is too many things that could play into the fact of why it feels stronger. but the backpressure thing has been beaten to a bloody pulp many times and ive seen it time and time again where it will be slightly benificial to the car. even though new age cats flow very well, its also a problem because they clog over time.

anyways, theres my .02 cents take is as you wish.

 

[No_Skillz]

Holy mis-information batman!

first off the only engines that truly NEED, as in required to run correctly are 2 STROKE engines! thats why they have the goofy shaped pipes. because it creates a (tuned) backpressure. it makes a wave of pressure come back to keep the A/F charge in the combustion chamber. same with nitro R/C cars. they are 2 stroke.

Now if you look at the whole cycle of a 4 stroke engine there is absolutly no purpose in backpressure. there is a whole stroke dedicated to just relieving the exhaust gases from the combustion chamber. if you have back pressure all it is doing is making the piston work agains itself, and also could leave exhaust in the combustion chamber after the valve slams shut. making it displace air causing less power.



Im very sure that all you are feeling a difference between the cars is in the drivetrain, and engine condition. the gst could be in better condition than the gsx.engine could be cleaner. just in general running "better" but not neccisarily faster (because of mods)

there is too many things that could play into the fact of why it feels stronger. but the backpressure thing has been beaten to a bloody pulp many times and ive seen it time and time again where it will be slightly benificial to the car. even though new age cats flow very well, its also a problem because they clog over time.

anyways, theres my .02 cents take is as you wish.

This is very reasonable. However, when I had my civic I know there was a noticeable power difference in the low end between having an exhaust and running an open header with nothing else done to the car. Does anyone else have any TECHNICAL insight?

 

[TooFastTooG]

Hey guys,
Well today I went and had a hi flow cat installed, and let me tell you that I can defenetly feel a difference, although it does not feel just as "torquey" as the gst, it feels alot better. Im thinking what you guys said about the GSX weight and mechanical differences has alot to do with it. It just feels like I dont have to give it as much gas now to reach the same speed. Thank you guys for all the help!

P.S. This is a very informational thread lets keep it going!

 

[jongreene]

Sivad87, that makes a ton of sense....what you said about the piston working against itself and us having turbo engines it makes even more sense why backpressure would only hinder performance.