My 03 gets sluggish when hot. Help before I get passed by a Vette!

Barrels · May 26, 2011

I have an 03 w/ 30k that I bought a couple months back. I bought it for general enjoyment and the occasional track day. It has no mods other than a K&N intake and stainless brake lines. I had no plans to do anything else, but am considering doing high-flow cats and a Gen IV cat back to help eliminate cabin heat.

I have noticed that I get a distinct loss of power after the car gets warmed up. This is especially noticeable in the low RPM range (below 3.5k) where the loss of power is accompanied by a "pop-pop-pop" sound from the exhaust under hard acceleration. It doesn't sound like a backfire or a knock. It sounds more like the pronounced and labored acceleration of an older and underpowered car. There is no hint of this until the car is completely warm. All gauges read normal and there doesn't appear to be any other symptoms.

I get crazy amounts of cabin heat by the time I start to notice this effect. That leads me to believe that I am experiencing something akin to heat soak. I am hoping that I can improve both the cabin heat and the heat soak effect by switching to the high-flow cats and eliminating the crossover. I would follow that up with a dyno tune that gets the fans on earlier and works in conjunction with a lower thermostat. Hopefully all that would get my engine bay temps lower and lessen or eliminate the problem.

Please let me know if I have correctly diagnosed the problem and what you or others have done to eliminate it in other vipers. I am open to other mods such as coated headers, better plug wires, etc. as long as I know they are worth the money and time.

TowDawg · May 26, 2011

Sounds like you could have a clogged cat as it is. I know a clogged one can rob you of power and get really hot. Then again, I know I'll never have that problem! Striaght from the M&M headers and out the Borla race exhaust. No cats to get in the way!

Paul Hawker · May 26, 2011

Also might be plug wires or Oxygen sensors.

Might be a good idea to take to a dealership for a scan tool to pick up codes.

bluesrt · May 26, 2011

clogged cats chief== or junk motor, pull off the cats cause if you dont u will have a junk motor

Flexx91 · May 26, 2011

Don't make Vettes feel so special. If one does pass you, there will be another one in 7 minutes or less............

Barrels · May 26, 2011

bluesrt said:
clogged cats chief== or junk motor, pull off the cats cause if you dont u will have a junk motor

How did you know I was a chief?

So the consensus opinion seems to be that my cats are the problem. I was planning on replacing those anyway, so that should work out. Is there any other opinion out there?

bluesrt · May 26, 2011

nnnoooooooooooooooooooooooooooooooooooooooooo= chief

georgethedog · May 26, 2011

Barrels said:
How did you know I was a chief?

So the consensus opinion seems to be that my cats are the problem. I was planning on replacing those anyway, so that should work out. Is there any other opinion out there?

Watch what you get for Cats. Ceramic = nice note not to loud, but loud enough. Metallic = very loud. Talk with Jon B at Parts Rack before you buy. He knows what goes best with what, and can match something up with your tastes! Good man that JonB.

Jasone · May 27, 2011

Definitely the cats..

chiefchad · May 27, 2011

Gen III Vipers seem to have a prob with cats failing from what I've noticed. I have mentioned this in other threads - check your headers for cracks. This is the root issue with Gen III which causes the failed cats. If you just replace the cats and still have a cracked header you will just blow out the cats again and be back to square one. The cabin heat is a result of the blocked cats. I would have been in the dark about this problem except for a very knowledgable and helpful Viper mechanic who has seen this numerous times.

TowDawg · May 27, 2011

chiefchad said:
Gen III Vipers seem to have a prob with cats failing from what I've noticed. I have mentioned this in other threads - check your headers for cracks. This is the root issue with Gen III which causes the failed cats. If you just replace the cats and still have a cracked header you will just blow out the cats again and be back to square one. The cabin heat is a result of the blocked cats. I would have been in the dark about this problem except for a very knowledgable and helpful Viper mechanic who has seen this numerous times.

I didn't even thin to mention the headers. When I put my M&M's on, BOTH of my stock manifolds had cracks in them. I've actually been told it's pretty common. I guess the stock cast iron manifolds don't hold up to the heat from these engines very well.

JonB · May 27, 2011

I also believe that after 30K miles you have failed plugs, and/or wires, that have fouled the cats.....and/or the oxy sensors.

the OE crossover-exhaust is hot to begin with.....

Venomiss · May 27, 2011

Barrels said:
I have an 03 w/ 30k that I bought a couple months back. I bought it for general enjoyment and the occasional track day. It has no mods other than a K&N intake and stainless brake lines. I had no plans to do anything else, but am considering doing high-flow cats and a Gen IV cat back to help eliminate cabin heat.

I have noticed that I get a distinct loss of power after the car gets warmed up. This is especially noticeable in the low RPM range (below 3.5k) where the loss of power is accompanied by a "pop-pop-pop" sound from the exhaust under hard acceleration. It doesn't sound like a backfire or a knock. It sounds more like the pronounced and labored acceleration of an older and underpowered car. There is no hint of this until the car is completely warm. All gauges read normal and there doesn't appear to be any other symptoms.

I get crazy amounts of cabin heat by the time I start to notice this effect. That leads me to believe that I am experiencing something akin to heat soak. I am hoping that I can improve both the cabin heat and the heat soak effect by switching to the high-flow cats and eliminating the crossover. I would follow that up with a dyno tune that gets the fans on earlier and works in conjunction with a lower thermostat. Hopefully all that would get my engine bay temps lower and lessen or eliminate the problem.

Please let me know if I have correctly diagnosed the problem and what you or others have done to eliminate it in other vipers. I am open to other mods such as coated headers, better plug wires, etc. as long as I know they are worth the money and time.

If you do not find the solution before June 21st this might be a good question for the Live SRT Engineering Chat.
http://forums.viperclub.org/threads...Chat-HERE-on-June-21st!?p=2973264#post2973264

Barrels · May 27, 2011

So to fix this problem and to make sure I keep it from happening again, I need:

High-Flow Cats
A cat-back that gets rid of the crossover
Headers
Plugs
Plug Wires
Oxygen sensors

Anything else? This is getting expensive.

TowDawg · May 27, 2011

Or just skip the cats and save some money (and heat)!

JonB · May 28, 2011

TowDawg said:
Or just skip the cats and save some money (and heat)!

Dont Do that ! Several reasons NOT to go G-3 catless, especially if trying to solve runabuility issues...

plumcrazy · May 28, 2011

bluesrt said:
clogged cats chief== or junk motor, pull off the cats cause if you dont u will have a junk motor

my money is on this. and i know first hand what clogged cats can do....BOOOM !

Barrels · May 28, 2011

Thanks for all the help guys. I am looking at two options: Random Tech cats from JonB or a cat delete. I have done an intense (seriously intense) amount of forum searching and seem to see two consistent lines of thought on this decision:

1. Cat delete is loud, stinks like balls, and makes your engine throw codes and generally run like crap.
2. Cat delete sounds louder but great, doesn't smell, and only needs a tune to fix any engine/drive-ability issues.

Response #1 almost always comes from people who have chosen to keep their cats or add high-flows. Response #2 almost always comes from people who have chosen to get rid of their cats.

I am going to put my car up on the rack in my shop as soon as my wife decides to stop screwing around and give birth to my son. Well, a few days afterward anyway. Then I will pull off the cats and have my local race shop fashion me a connecting pipe. I will throw on a GenIV cat back from Mark at Woodhouse and see how it sounds/smells/runs. If the volume is bearable I will go get it dyno tuned. If it's too loud or stinks, I'll call JonB. Either way I will post a video and share my results so I can hopefully add something to the community.

plumcrazy · May 28, 2011

i dont like cats but on a gen3 NA car id use them,. not SC though.

try the catless route, its easy enough to throw a set in.

viperjim · May 28, 2011

If your car is running hot you definitely need to remove the cross over pipe and have your computer reflashed by DC Performance. They lower your coolant temp to about 180. Makes a big difference. Plus you will not reach the temps that cause your car to retard your timing thus slowing you down.

TowDawg · May 28, 2011

JonB - PartsRack said:
Dont Do that ! Several reasons NOT to go G-3 catless, especially if trying to solve runabuility issues...

If the cats are clogged, how is removing them causing a problem. There a LOT of people running catless in Gen III's, including me. No drivability issues at all as long you get a proper tune. Yes, you do smell it more, but I hardly even notice it now unless you're sitting still for a long time with the engine running. That, or in the garage with the door closed and it running. And if you were doing that for any period of time, then you're probably wanting every bit of exhaust you can get to come out.

Yes, it does pop and gurgle on decel without cats, but I actually like that.

Zentenk · May 29, 2011

O2 sensor, cats, plugs, wires. Do them, go!

I had a similar problem with a gunked up cat and one day a guy said flames were shooting out my exhaust haha.

Barrels · May 29, 2011

Zentenk said:
O2 sensor, cats, plugs, wires. Do them, go!

Working on it. I haven't found many plug wire options and I have found way too many plug options. I'm open to suggestion on both.

Seems like Qualitywires are the forum consensus. I am not an expert, so what makes these wires better than Granatelli or Magnecor?

As far as plugs, I'll probably go with Bosch (4508 or 4428) because I am a fan of the work that Bosch does.

Barrels · May 29, 2011

If I'm going to bypass the cats (for now) I only need the upstream 02 sensors right? It sounds like the tuner can bypass the downstream and I can just unplug them.

Phun70 · May 30, 2011

Don't go with Bosch plugs!!! They're CRAP!!

plumcrazy · May 30, 2011

stock SRT plugs are just fine

Barrels · May 30, 2011

Phun70 said:
Don't go with Bosch plugs!!! They're CRAP!!

Any particular reason/specifics? I have never heard of failures or poor quality from Bosch products.

Darbgnik · May 31, 2011

Before getting too far into it, get an SCT tune from Roe, Viper Specialy or DC, along with a lower temp thermostat. These cars really pull the timing when they get hot when everything is good.

Try this before dumping a whole pile of money into it.

351carlo · May 31, 2011

Barrels said:
Any particular reason/specifics? I have never heard of failures or poor quality from Bosch products.

Cars like ours want the standard style plug. They're designed to work with them. My opinion with aftermarket plugs is an NGK works best, but that's personal experience.

Bosch seems to have gimmic plugs with dual electrodes etc. Electricity goes to the path of least resistance, if your plugs are in good condition, you want a controlled gap with a good plug. The stock plugs are fine as well.

eucharistos · May 31, 2011

kudos barrels, sounds like you have done some decent research. qualitywires handle the heat, fit perfectly, great customer service, site supporter.....all these can't consistently be said for the other wires you listed

n/a= stock plugs

and like plum said, if you have the option of catless, give it a try, easy to add hiflow if you don't like it

+1 on an sct tune

:drive:

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