Test pipes increase engine risk?

[SilverStone05]

I have to agree with ANYTIME, any potential benefit of a test pipe isnt going to be big enough to deystroy the ozone. I run high flow cats on all of my cars instead of test pipes. There are gains to be had using high flows over standard cats, but there is no need to gain the additional 1.3hp and kill the ozone using test pipes.

I'm not buying it....I still think that you will see appreciable (10+ whp) gains in a forced induction application by using test pipes. I wonder if any turbo guys here are running test pipes and if they could give us any insight.

I too believe that the gains resulting from high flow cats is not worth the money.

And don't get me wrong, I agree with you, it cannot be denied that the total elimination of the cats is more harmful to the environment and something that can get you in trouble. However...my 95 300ZXtt passed smog testing with flying colors here in Ohio 3 years back with all FOUR cats removed. (Precats, just down from the turbos and the main cats in the middle of the exhaust)

 

[KGP]

I wonder if any turbo guys here are running test pipes and if they could give us any insight.

Most turbo NSX's, save the cartech/bell system, don't even have room for cats. So, don't look for hard data there.

 

[BioBanker]

And a guy who just pulled his cats immediately after dynoing his car free'd up about 30HP.

My question comes from that experience as, if I wanted 30 more HP, I would have to go to 9lb boost, get all new injectors, pumps, AEM EMS for OBDII and pray to god that Im able to get it tuned such that my engine runs, and doesnt grenade.

So, with the risks (both quality of life and engine) from increasing boost to get 30 more HP, Im wondering if they're worth it given cats can be yanked for little bucks and no additional risks to the engine.

Just thinkin' thats all.

 

[ANYTIME]

You've taken a hit off of the GO FAST crack pipe once, now slowly put it down and walk away..............

 

[sjs]

You are missing a couple points. Regarding the odor, if you smelled fuel then it wasn’t properly tuned or was in open loop where it needs to be rich. Read my post again where I said “unless your car is running rich”. Other than that the difference should be impossible to tell from a following car. But, if the car is running that rich then the cats aren't able to do their job very well anyway, which leads me to my second point. In open loop/WOT/high loads & RPM, the cats don’t do much anyway. They work really well in cruise mode around stoich, but as soon as you stand on it your AFR starts heading towards a much richer mixture. Someone please correct me if I’m wrong and point me to a factual reference, but I don’t think cats are very effective at typical “performance” mixtures of around 12:1, not to mention trying to "process" a phenomenal CFM when the car is under load at high RPM. Any idea what the velocity of the gasses are? Even the dyno-type emissions tests keep cars in closed loop with lean mixtures because they would all fail at WOT (with a few ultra-low emissions exceptions of course). As for cats, I took my CTSC car through the full simulated drive at the emissions test center with and without cats several times each as I was working on the AEM maps and the pollutant graphs were almost indistinguishable.

So if you are really worried about the environment, never use more than ½ throttle or 50% RPM. While your at it, sell the NSX and buy a Civic or a hybrid. Don’t get me wrong, I’m very conscientious about the environment but the holier-than-thou bit is a very slippery slope on this topic. I could cruise in my NSX without cats all day and pollute the air less than you do in a few fast starts from a stoplight. Actually I couldn’t, because I put the cats back on.

Edited for spelling and "cats aren't able " rather than "cats are able".

 

[NetViper]

Well Dave, prove us all wrong. Take off the cats and see what a huge gain you get.

 

[da3dalus]

I'm not buying it....I still think that you will see appreciable (10+ whp) gains in a forced induction application by using test pipes. I wonder if any turbo guys here are running test pipes and if they could give us any insight.

I too believe that the gains resulting from high flow cats is not worth the money.

And don't get me wrong, I agree with you, it cannot be denied that the total elimination of the cats is more harmful to the environment and something that can get you in trouble. However...my 95 300ZXtt passed smog testing with flying colors here in Ohio 3 years back with all FOUR cats removed. (Precats, just down from the turbos and the main cats in the middle of the exhaust)

Yea there are definatly gains... I run a 3" electric cutout on my mazdaspeed. At 15psi it puts down 356whp through a cat, with the cutout open off the downpipe at the same psi i lay down 387whp.

There are gains, but for 99% of the NA crowd it wont make a difference, a FX500, then yea, go for a test pipe. The rest of us dont need to kill the enviorment.

 

[AU_NSX]

You guys crack me up!!! Can I have some of what some of you are smoking!!!

Test pipes damaging your car...lol

Catalytic converters saving the ozone layer... lol

Proof that you can get any advice you want to hear on the internet..

 

[SaberX]

Yea there are definatly gains... I run a 3" electric cutout on my mazdaspeed. At 15psi it puts down 356whp through a cat, with the cutout open off the downpipe at the same psi i lay down 387whp.

There are gains, but for 99% of the NA crowd it wont make a difference, a FX500, then yea, go for a test pipe. The rest of us dont need to kill the enviorment.

Electric cutout... thats kinda cool. Does anyone have something like this on the NSX? That'd be pretty sweet.

 

[da3dalus]

Electric cutout... thats kinda cool. Does anyone have something like this on the NSX? That'd be pretty sweet.

I got mine from http://www.quicktimeperformance.com/

they have a lot of info on their website. No reason why it cant be applied to the NSX. :biggrin:

 

[Daedalus]

Is that not seen as an obstruction by the exhaust when closed? Seems like the pressure waves would be reflecting off the plate and back toward the source. I can believe you get more power when it's open vs. closed, but what about closed vs. straight pipe? Anyone ever do a test on that?

 

[sahtt]

It seems, predictably, that not too many NSX owners have experience with test pipes. Coming from Nissan 300zx turbo's, Fd's, s2k's, 1000's of these car owners run test pipes, many as one of their first mods. Even in n/a format, it is usually the best gains for the money. I ran test pipes on my 300zx turbo and S2000 I recently sold.

1st. Won't hurt your car. No different than adding a better flowing exhaust as most variables are concerned. In fact, it causes less heat build-up and better fuel mileage.
2nd. Doesn't smell like rotten eggs. Where this originated from, I'm still not sure. It smells like more potent exhaust fumes, and if you can smell exhaust at all inside your cabin, you have other problems.
3rd. On a turbocharged car, depending on the number of precats and main cats, removing the catalytic converter systems can easily giver you 6-10whp in a n/a car peak, and 20+whp in a turbocharged vehicle. NSX's are special, but they have combustion engines and run on petrol just like anything else; the same applies.
4th. This one is not intuitive, but the increase in sound in most* stock exhaust systems is not significant by adding a test tipe, n/a or forced induction. I'd say adding a test pipe is approximately 1/4 or less the additional sound compared to the additonal loudness of adding a standard aftermarket cat-back exhaust.

Lastly, though this can be ignored, the pollution caused by an NSX, or all NSX's for that matter, running on test pipes is at best extremely marginal. I have studied quite extensively motor vehicle pollution regulation due to some fields of economics I was involved with while helping the state's relationship with some trucker and industrial companies in Houston. Sadly, the pollution China released [obviously this is general, there are many different types] since its transition to the free market system based economy of the early 80's alone blows any issues like these out of the water. Luckily, their massive growth/lending strategy is being slowed down later this year, and an environmental analysis and restoration will proceed. Regardless, from 1985-1990, China released more polution than the U.S. has since the end of the 1st industrial revolution [to the present]. Pollution controls put on civilian populations' commuter vehicles is not where one should be focusing if they want to help global air pollution, though we must all do our part to the best of our abilities, even if it means giving up 10hp(!). That's a whole other topic, go drive!

 

[BadCarma]

I have been away from the forum for a couple weeks due to on going heart issues and come back to this totally confusing, misleading and utmost WRONG information pertaining to test pipes on an NSX.
I have heard it stated that not many of use have experience with them. WRONG! I have had them on my whip for 4 years without a SINGLE issue. Some state they stink others that they slag the engine, gain WHP, don't gain WHP, mess with the AF ratio haha, and thats about the sum of it.

1. Test pipes IMHO are run for a reason, now if its a valid reason cool, if not it makes no difference other then unwarranted expenditure of funds.
2. I ran them as to not damage my cats with n20 which is a valid reason as well as those running S/C and Turbo's OR a motor overhaul for massive CFM due to high NA aspiration because with that you need to let the motor breath as well as all in the list.
3. If you are NOT running what’s listed above you won’t gain jack shit! I saw someone suggest race fuel, on an NA car it will SLOW you down, high-octane burns slower and we use it as added knock and detonation protection.
4. TEST PIPES WILL NOT INJURE YOUR CAR!!!
5. Finally, I don’t recognize most of the posters to this thread. It seems we have a lot of new people with X'S and a lot of posers whom don’t own the car and use what info they think is pertinent from other cars their familiar with in regard to tuning. This FI/N20 forum use to have some serious bad ass tuners and lots of experience with the car.... LOTS OF REAL WORLD EXPERIANCE. Please do the forum the respect it deserves by researching your facts before posting and lurk for a while. if you don’t have experience with an NSX do not post to the tech forum, general cool but don’t jump in here and mislead the uniformed. Sorry guys but this beloved tech forum is going down the crapper due to 15 year olds posting and posers.

Best Regards David

P.S. I forgot to mention that in addition to running them myself for spray I have Taitec pipes that have thread bungs to except a wideband A/F gauge and logger and an EGT gauge both of which are essential for F/I and N20.

 

[SilverStone05]

Shoot...someone's going to have to dyno and get back to us.

If someone can find me some test pipes for an 05 I will gladly be the test mule. :biggrin:

 

[SilverStone05]

Yea there are definatly gains... I run a 3" electric cutout on my mazdaspeed. At 15psi it puts down 356whp through a cat, with the cutout open off the downpipe at the same psi i lay down 387whp.

So you just proved my point.

There are gains, but for 99% of the NA crowd it wont make a difference, a FX500, then yea, go for a test pipe. The rest of us dont need to kill the enviorment.

Read my post, I don't know why you are arguing with me over an N/A application, I never mentioned it...If you'll look, the person who created this thread has a supercharger. Furthermore...this thread is posted in the Forced Induction section :wink:

 

[da3dalus]

So you just proved my point.

I cant help it that the NSX i went to purchase in febuary was sold on my way to pick it up by a really shady owner who sold it out from under me after i put down a deposit. Sorry i havent found another perfect car yet that would eliminate my "poser" status.

I'm not arguing with you over the NA application, simply refferring to all of the other people that were mislead thinking that they were going to get 40whp at thw wheels on their NA cars, when in fact your post, as you point out, was reffering to a supercharged example.

 

[Bob Kenney]

Any modification to let an engine flow better will help to increase its output; provided it is tuned to take full advantage of the flow rate. An engine is, in many respects, an air pump. The more efficient that pump the more power it will make. It all becomes a balancing act to keep modifications working together to achieve the greatest gains. :smile:

As stated earlier the higher the levels of modification the more pronounced the gain from test pipes. There is a logical progression to this whole evolution of your individual engine's performance; the higher you reach the more refined the modifications tend to become. At some point test pipes will be consider by the truly serious seekers of high HP. Are they a logical progression in the search for more power? Yes. Are they morally, legally and ethically responsible? That is an answer each one of us needs to decide for themselves based on many considerations.

The easy proof of level of gain they would provide is a test; a dyno pull before install, a dyno pull after install with no other modifications. This would let them earn their name "test pipes".

These are just my thoughts and not meant to argue for or against test pipes. :biggrin: :wink:

Happy Easter/Holiday/Spring to all:biggrin:
Bob

 

[TURBO2GO]

So I read this whole thread and I am still not sure what the answer is to BioBanker's original question:

Will freeing up the exhaust lean out the motor on its own?

 

[TURBO2GO]

Is that not seen as an obstruction by the exhaust when closed? Seems like the pressure waves would be reflecting off the plate and back toward the source. I can believe you get more power when it's open vs. closed, but what about closed vs. straight pipe? Anyone ever do a test on that?

My thoughts exactly...

 

[TURBO2GO]

I am wondering what type of risks to the car increase if you free up power by removing the cats.

I ask this because with the autorotor CTSC, it appears that if you pull the cats, using only the basic bolt ons and the 6lb kit, that a NA2 will put out about 395 to the wheels. That is maybe even more then what the same car would put down with the high boost kit and a full-on AEM EMS with injectors and pump and tune, etc...

Increasing the boost has the inherent risks that are obvious. But I am not clear what risks are increased if the exhaust flow is increased via pulling the cats. Will the car run leaner? Will the increased power increase heat or stress on the engine components? Does anything change?

TIA

Dave

My guess is that these scenarios are not the same. If you have freer flowing exhaust, the engine is just more effecient. You will have lower operating temps and less stress on the motor than if you had more boost from the SC, and then bottled it up with exhaust restriction. It seems with an NA motor that the ECU can easily make up for minor improvements in flow with better exhausts and better intakes. What it does with a supercharger and all the Comptech stuff cheating the fuel system into working right, I have no idea... I think that is what you are inquiring about, and thats what I really want to know too.

 

[AU_NSX]

So I read this whole thread and I am still not sure what the answer is to BioBanker's original question:

Will freeing up the exhaust lean out the motor on its own?

No...

 

[Bob Kenney]

My guess is that these scenarios are not the same. If you have freer flowing exhaust, the engine is just more effecient. You will have lower operating temps and less stress on the motor than if you had more boost from the SC, and then bottled it up with exhaust restriction. It seems with an NA motor that the ECU can easily make up for minor improvements in flow with better exhausts and better intakes. What it does with a supercharger and all the Comptech stuff cheating the fuel system into working right, I have no idea... I think that is what you are inquiring about, and thats what I really want to know too.

You are on the right track; you need to separate the the test pipe issue into 2 categories:
First case: A naturally aspirated stock engine with intake, headers, exhaust and test pipes.
Second case: The same engine with the addition of a CTSC.

In the first case scenario it is my feeling that the ECU can compensate for the increased efficiency by increasing the fuel pressure and duty cycle of the injectors to compensate for the increased flow rate.

In the second case scenario the ECU has been tricked into not seeing the boost and the fuel pressure has be increased by increasing the voltage supplied to to the fuel pump. [I am speaking of the CT Whipple SC] This is how the 240 cc injectors are able to feed sufficient fuel to the 6lb SCed engine. If you increase the boost to 9lbs [9lb kit] it comes with larger injectors since the stock injectors are maxed out at the increased flow rate at 6lbs.

The question is: what happens to the air/fuel ratio of the 6lb SCed engine if test pipes are added. If the engine is equipped with an AEM with larger injectors there will be no problem; if not, how close to the edge of a safe A/F are we coming? I am not sure; but I have ordered a set of test pipes and will find out in the next few weeks; stay tuned and I may be able to supply additional information.

Bob

 

[TURBO2GO]

No...

Can you elaborate? aren't you moving more air through the motor? in which case more fuel is needed or you run lean?

If you are running an autorotor with 6psi boost and lose exhaust backpressure by a freer flowing system (removing or changing cats or whatever), how does the factory ECU and the comptech stuff handle this change?

This is what we want to know. We are not really concerned with an aftermarket engine management system, we already know what those do.

 

[AU_NSX]

Can you elaborate? aren't you moving more air through the motor? in which case more fuel is needed or you run lean?

If you are running an autorotor with 6psi boost and lose exhaust backpressure by a freer flowing system (removing or changing cats or whatever), how does the factory ECU and the comptech stuff handle this change?

This is what we want to know. We are not really concerned with an aftermarket engine management system, we already know what those do.

Read what Bob Kenney said... He is spot on!

FI is totally different situation to NA...

RE: Removal of CATS and substituting CAT pipes...

The substituting of CAT bypass pipes for the CATS does NOT INCREASE the amount of air moving through the exhaust system or engine. With CATS, the pressure in the system is ever so slightly higher in fact it is so slight it is really negligible.

 

[RON98]

Isnt that guy running a supercharger?

Since supercharger is not effect by exhaust flow, taking off the cats should not effect the air intake of the engine.

If it where turbos, the extra flow could over power the ability of the waste gate to dump exhaust to the point where the WG could be fully open and the turbos still making boost.

The reason from my understanding your car picks up more HP is cause cat causes restrictions on the exhaust flow. On the exhaust stroke and a few degrees into the intake stroke, the extra presure in the exhaust manifolds allows more already burnt ( some what inert ) gasses to remain/enter back into the chamber. Since already burnt gasses (co2 and nitrogen mainly) does not burn, your not getting as much fresh air as you would if you had less restrictions in your exhaust, more air/more fuel = more power.

Also the engine does not have to work as hard to push out the exhaust on the exhaust stroke which probably frees up something.

A/F in my mind would be changed a little ( put enphasis on little ) bit depending on if your car was tuned with the cat or with out. However in open loop, the ECU reads off the O2 sensor and will compensate for the little extra bit of air coming in so your back to square 1.

Also, with a SC FI system, your car will be running on the rich side anyways! So leaning it out a little (little) bit is no biggy and will product more power in close loop when the ECU is working blind off the preprogrammed fuel map.

Used test pipes for a long time now, have had no problems. It acturally does not smell like rotten eggs.... more of a gas smell... but definitly no rotten eggs. Cats are there to burn up extra gas left over from the combusion process. The stinky smell is from sulpher in the gas you buy. So if it gets stinky, change a different brand of gas. :tongue:

"With CATS, the pressure in the system is ever so slightly higher in fact it is so slight it is really negligible."

As for the post above... I dont think so. Have you seen a cat.... at least 20% of the passage is blocked by the honey comb material..... so thats at least 20% less back pressure due to the cats ( if i over estimated then something like 10% flow is still pretty big )

Took off the cats on my turbo supra..... it was night and day. Although the SC does not work off exhaust gasses, the removal of the turbo from my supra which lead to much quicker spool times and better HP can be used as a illistration of less back preasure.

btw screw high flow cats. dont do something in life half ass. Your neither saving the envorinment or full HP protential.

Worry about the environment? Ride a bike. If you drive a car, cook with wood, matural gas, electric stove and anything else short of solar power, your killing something. I want dead babie bunnies and cute little beavers to shoot out my exhaust at all times during my driving experience. Less crying about the enviornment and more killing baby animals you hipocrites :biggrin: I cant spel, bite me.