tjwong

If you are contemplating adding LTx LT headers some day and are using CATs, be aware of potential hazards concerning location of where you install the CATs.

There is a potential fire hazard with CATs if they overheat due to overloading them with fuel. This can occur if there is a o2 sensor failure, engine mis-fire, PCM fault, injector fault to name a few conditions.

See this thread to see the extent of damage to a fellow members 96 LT4 C4.

http://forums.corvetteforum.com/show...14&forum_id=82

The white that you see is whats left of the glass once all the resin was burned away, the extent of the damage goes above the transmission and extends almost from the fire wall back to the shift boot opening. This picture was taken before I removed the transmission. Once it was out further damage was found. You can literally poke your finger through the glass where the damage occured. The carpet padding against the tunnel was also charred and burnt, it was seconds away from flames when it was caught and water applied.

If installing CATs in this area, I would suggest applying a hi-temp insulating mat against the glass, secured by hi-temp RTV. It won't stop it completely but would definitely buy you some time.

cv67

Thanks for the heads up!

sami85L98

Thanks for letting us know this, u r a good tuner and a good man.

aboatguy

Thanks for the heads up. Good thing you guys caught it when you did.

Mike

Strick

I replied to that thread and I just wanted to know what headers and what cats were used. I want to install EM long tubes on my 92 with Random Tech's Cats. Is this the same set up? How about shielding like the original Cats have?

tjwong

The headers that are on this car are TPIS headers. The CATs that were used was a generic brand that were the ceramic substrate CATs. If you use bullet CATs use a Dynatech Headers or a Random Technology's Metallic substrate converter. These tend to run much cooler than the ceramic type. Also the CATs that did the damage did have somewhat of a shield on them. But with the temperatures involved that shielding wasn't enough. And they were just way too close to the glass.

This is where my CATs are located:



Notice where the color goes from greenish to black. Where it is black it is sheet metal and not fiberglass. I am going to add additional heat shielding to that area since I have found a problem such as this. It is very important to know and understand that if you should have any sort of mis-fire issues, all that unburned o2 is going to cause the o2 sensor to think its lean, the PCM/ECM will begin to command more fuel, and the CAT will have to process all that fuel. And when it does, the chemical reaction to convert that fuel causes lots of HEAT Contrary to beleif the o2 sensors do not read anything but o2, it doesn't read HC (gas fumes) or any thing else. That is why it is called an o2 sensor. And when you have a mis-fire that volume of o2 in that cylinder is not burned and will be sensed by the sensor.

MikeC4

TJ, that looks like a sweet setup!!

I like the exhaust spring suspensions. Are they easy to find at any auto supply house?

What is the reason/need for an "X" pipe, besides adding rigidity to the syetem? What's in the "box" at the center of the "X" pipe? Seems this box would increase back pressure..

I don't know squat about setting/tuning exhaust systems

Thanks!

tjwong

Mike the spring hangers are the stock OE hangers from GM. I have a LT1 car, so if you have an earlier L98 car, you can get the LT1 hangers from GM and they just bolt on. Then you can add a LTx style dual exhaust under you car.

The theory behind the X pipe is that it is supose to aid in scavenging the exhaust gases by balancing the exhaust flow pulses between the two banks. In my car there was a noticable difference in noise and resonance between the X and a H pipe. There was also a noticable difference in power between the B&B resonator and the X pipe with the X making more low and mid range power. The box you see is not a box, it is just a reinforcing plate that was welded in place by Dr. Gas when this X pipe was made.

VenkmanP

Thanks for the heads up!

Perfusion

TJ, thanks very much for the tip - I'll go have a look now just to make sure all is well! By the way, those are BEAUTIFUL extensions between the collector the cats. Who made 'em?

STL94LT1

Hmmmm, I need to crawl under my car to see if there is any heat damage from the cats.

bogus

damn... that's scary...

Lichen

If you have an automatic, you have no choice but to put them back behind the tranny. I originally felt that they were too far back, but now you have made me feel much safer.

SJW

Hey, Tom.

Is that x-pipe stainless? Would you or Dr Gas be interested in fabricating another one to be sold? I might be interested in buying one.

TIA.

Be well,

SJW

tjwong

SJW that X pipe is mild steel that is ceramic coated. Call Dr Gas and ask for Neal. He has my CAD Drawing of the muffler demensions that he used to make that unit. He can just make you another. Tell him it was a cad drawing that was sent to him by Tom Wong. If he doesn't have it contact me again and I can fax it to him The cost is about $200 and shipping.

Strick

Okay, can the bullet cats from Random Tech be attached to the EM long tube headers' collector on a 92 6speed? It looks as though there would be room for the cats there. Wouldn't it be close to the original location of the OEM cats? BTW, that is a beautiful looking exhaust and I will be talking to Neal for a X-pipe to replace my B&B resonator. Does he ceramic coat his X-pipes? How exact does the drawing have to be? Thanks

GeosFun

TJ, I looked under my C4 yesterday. It does not look shiny and clean like yours. Where is your road crud, oil leaks, stains, rust, etc?

tjwong

Strick, the cad drawing that Neal has is a drawing depicting the exact demensions of a B&B resonator. So in saying that his X pipe made from my drawing will fit your B&B system exactly My car is a M6 as well. but I choose to install the CATs in the rearward position. Back there the body is sheetmetal. You should also be able to come right off the EM collector tubes as well. Just make sure that if you use the RT CATs that you get their metallic substrate units. The main reason is because the metal CAT runs much cooler. An alternative is the Dynatech Headers 3 inch metal CAT available from Summit for $150 each. Summits part number is: DTC-79-400300

Slalom4me

Hold off on more Dr Gas posts here - I'm interested and am going to
start a new thread.

TJWong's custom 'X'-pipe from Dr. Gas.

.

Slalom4me

If someone has a configuration they worry might be problematic,
they could use crayons or paint that discolours when a designated
temperature is exceeded.

Tempilstik crayons from Tempil are available in various ranges at
welding supply houses. Google for the mfr's site.

Alternatively, consider Tempilaq Temperature Paint. I haven't
used this but I've seen it at Pegasus Auto Racing.

For a one-time use, neither of these choices is particularly cheap.
See if you can find a friendly welder with either of the above
in an appropriate temp range.

.