Need Help with exhaust

[julianmallin]

Hello, i just put straight pipes on my 1997 esprit usa model. I replaces the cats with straight pipes but i can not get the check engine light off. Any ideas????

Thanks Julian

[lotusguy]

Julian,

There isn't necessarily any cause/effect between your engine light and the exhaust work. What codes are you getting?

Be sure to reinspect all points so that you're sure all vacuum/electrical connections are tight and not causing the light. Also, try resetting the ECU by disconnecting the battery and waiting several minutes before reconnecting it. Start the car and expect some erratic running until the ECU relearns. This may take up to 30 miles of driving. Good Luck. Happy Motoring! ...Jim'85TE

[ErnestM]

What did you do with the O2 sensor?

Also, IIRC removing the CATS actually causes a problem because of the engine management system is expecting a certain exhaust composition even if you have located the sensor correctly...

I think Marcus has some "free flow" CATS that might be a better option than straight pipes...

ErnestM

[lotusespritworld]

Removing the CAT doesn't release much power as the exhaust system is pretty free-flowing, not worth the effort apparently.

Also the ECU is looking for different readings from the two sensors and will be running in pre-programmed 'fault' mode, due to the readings, which will reduce power and is probably why you're getting a 'check' light!

I'm not sure of a way around it, but I'm sure someone has come up with something. Would be interested in how this problem has been overcome.

kato
Lotus Esprit World

[julianmallin]

Thanks for your help but i still need to find away to trick the computer to think the 02 sensors are on the car.

[rlearp]

You pulled the O2 sensors and aren't running them? Bad. Anyone that told you that the car would run better without them or advised you to lose them is, IMNSHO, an idiot.

You need these for the car to run properly, otherwise it will have to default to an open loop mode since it can't get O2 content after combustion.

Just weld the O2 bungs into your straight pipes at the same place they were on the catalytic converter. O2 bungs can be purchased from Summitt, Jegs, and other places and are likely available at your local muffler shop. If you can't weld have them do it. Then screw the O2 sensors back and you'll be fine

>> Edited by rlearp on Sunday 7th March 21:46

[JSLoud]

Although I'm new to the Esprit world (and learning as much as I can), here's what I know based on tuning experience with other marques:

Part of OBDII required that O2 sensors be placed after the cats so that a problem with the cats would trigger the on-board diagnostic system with a fault. Removing the cats, therefore causes the check engine light to appear and may affect performance.

On other makes, people have used filters inline with the O2 sensor to trick the ECM into thinking the cats are still in place.

Plug "MIL eliminators" into a search engine to see what I mean.

JSLoud
'95 Esprit S4s

[incautious]

OBD2 works like this. The PCM reads the output of the rear sensor and compares it to the front sensor. If the cat is working there will be a difference in oxygen content because the cat is doing it's job.If there is no difference between the signals the PCM records a fault and sets a DTC(digonastic trouble code)saying your cat is bad. Since you removed your cat you get the same signal and the PCM sets a DTC.You should also see a REDUCTION in power and will now automatically fail a smog test if the check engine light is on. There are two things that will work: put the cats back(or use high flow units like magnaflow)OR you can buy O2 sensor simulators from companies like summit or jegs. These are 4 wire units that will fool the computor into thinking that there is an increase in oxygen and not set a DTC. You would most likly have to try and figure out which output is which(since these are for mustangs and Gm cars)but this could be done with a DST(digonastic scan tool).
A lot of work and you most likly will still see NO benefit by going this route, but it's your call.Good Luck

[julianmallin]

Thanks for all your help this forum is the greatist.

JULIAN

[princecharming]

Hi Julian,

The O2 sensors are very important.

Here's a link to how my friend Johan did the exhaust on his widebody V8:

www.extremeesprit.com/Perf__Mods/Exhaust/exhaust.html

See how he changed the exhaust, but retained the sensors?

By the way, that Esprit is infamous for going over 200MPH (before his tranny failed upon decelleration around 130 or so) and I believe he did it with the O2 sensors in place. No reason to eliminate them.

Roy

P.S. Hi all, I'm back!