exhaust question

Hello,
#1. I'm wondering if anybody can give me a web site that I can read about the type of computer that is in my 95' Blazer 4.3(CPI).

#2 when removing the catalytic converter what kind of havoc is this going to cause due to loss of backpressure.

I removed the converter on a previous truck* that I owned and seemed to suffer nothing but increased performance/gas mileage.

*no Cat and a Flowmaster muffler single inlet/dual outlet and yes LT it had duals.. :eek: (drove it for 40,000 miles that way)*

Blazer LT i'm looking for your response here cause I know that you have touched on this in the past but I can't seem to find your post where you talked about this.

Thanks to all in advance.

Here you go boss

http://www.automotiveforums.com/vbulletin/showthread.php?p=2499655#post2499655

Hello,
#1. I'm wondering if anybody can give me a web site that I can read about the type of computer that is in my 95' Blazer 4.3(CPI).

#2 when removing the catalytic converter what kind of havoc is this going to cause due to loss of backpressure.

I removed the converter on a previous truck* that I owned and seemed to suffer nothing but increased performance/gas mileage.

*no Cat and a Flowmaster muffler single inlet/dual outlet and yes LT it had duals.. :eek: (drove it for 40,000 miles that way)*

Blazer LT i'm looking for your response here cause I know that you have touched on this in the past but I can't seem to find your post where you talked about this.

Thanks to all in advance.

#1 You have an OBDII computer.

#2 Honestly, removing the cat does nothing for performance and will cause you computer to have long term trouble adjusting the long term fuel mixture which is controlled by the Bank 1 Sensor 2 O2 sensor after the cat. Do what I did, install a carsound Magnaflow universal cat, pass emmisions, have a nice increase in sound, have a properly running emmisions system and have the needed backpressure with a higher flow rate then the stock cat. The stock cat is large and is used as a resonator in the exhaust to take out some of the rumble. The new cat is 1/3 the size and man, does it sound awesome.

#3 a single inlet, dual outlet is not duals, that is a dual tailpipe setup.

Running true duals on a normally aspirated 4.3L is a COMPLETE waste of money. Run single 2.5" pipework and cat to a single inlet, dual outlet flowmaster 40 or Ravin Z33 muffler and you will have all the flow you will ever need and the sound of a small V8.

I will post some soundclips of my new exhaust and show you. It sounds awesome.

Thanks all,I have a book report on vehic. computers now. :eek7:


My 95' Blazer seems to disappoint me in the lower RPM range (idle to around 3000)when floored, after about 3000 it seems to come alive,only till like 4500 then it just seems restricted until it shifts out at 5500. My previous S-10 4.3 was this way till I removed the Cat. and installed the flowmaster (single inlet dual out) and routed duals from there back.

Now I not arguing that removing the Cat. and duals might not get the power that a person might expect,BUT it was very surprising and coincidental! I'm just saying what I did and my results.

#1 My Question is .....what in the heck can I do to help this less than desirable performance in the lower RPM range?

#2 I feel that if I put a nicer muffler in place of the stock that might help the higher RPM issue.

#3 How will the EGR mod help performance?(I plan on doing this if i'm ever in there)

Any comments welcome,
Thanx in advance..





.

#1 My Question is .....what in the heck can I do to help this less than desirable performance in the lower RPM range?

#2 I feel that if I put a nicer muffler in place of the stock that might help the higher RPM issue.

#3 How will the EGR mod help performance?(I plan on doing this if i'm ever in there)

Ok, well, here is the advice you require.

#1: The problem you are having I think is your intake is too restrictive and the engine is choking to get the air it needs. Installing an air intake will really help in that department. But before you install an intake, install an aftermarket muffler. LEAVE THE CAT IN. The cat is not the cause of your problem. The stock blazer muffler is downright HUGE and replacing it will do wonders for sound and for performance.

Remember, exhaust first, then intake.

#2 You bet your ass it will help.

#3 It doesn't help performance, but it does help with responsiveness in some application. But with some, it will cause pinging and detonation seeing the EGR system is there to lower combustion temperatures and reduce ping. If it doesn't work well, ping will occur and the knock sensors will retard the timing and hurt your performance even more.

A fully functional EGR system is the best thing for performance and fuel economy.

At 3000rpms you are seeing the IMTV (Intake Manifold Tuning) valve opening up which moves the torque curve to the higher rpms when you are between 2500-3200rpms and the throttle is over 35%.

Real ingenious system really, allows for torque at low rpm when closed and at higher rpms when open.

Thanks LT,
I will take your advice on this(exhaust b-4 intake).as far as intakes go the K&N looks like a good choice. K&N seems a little steep on the price but whatever,maybe I can find a used one,possibly from a wrecked truck.

I talked to an EX-wrench from a GM dealer he told me to change the fuel filter,it sounded like a textbook description for a cause to change the filter. I also have a pressure tester coming from him to test the backpressure on the exhaust. He told me that I should have no more than 3 PSI from where the O2 sensor screws in.

ALSO i'm getting a fuel pressure guage to test the pressure @ the schrader(sp?) valve. He rattled off the pressures that I should get in the keyed position,but he said he would write them down for me,cause he didnt expect me to remember them.

.....next the fuel milage seems to have gone south lately. I noticed the temp has been lower than usual. The needle ride @ full temp. right where the astricks* is on my little attempt to draw my gauge.I hope it looks the same when I send the message.*S*



210
* \ /
100 250

From what I have read I thinking that my computer is never going into closed loop operation.That would be that cause for horrible gas consump.


anyway just thought I would drop a line.

Thanks to all for your tips and info.

Ok, so what you are saying is you temp when fully warmed up is between 0 and 1/4 on the gauge.

If this is so, your thermostat is stuck open and you need to get it fixed ASAP before you carbon up your engine because of low combustion temperature and rich fuel mixture caused by the engine's computer dumping more and more fuel to try to get the engine up to closed loop minimum.

BlazerLT,
Picked up a thermostat and gasket today,Thanks for the info.

what a funky place for a thermostat,kinda akward to get to.

I will pickup a fuel filter and get that on soon.

I bought a Haynes manual,very informative section on our type of fuel injection.

Also the computer section does a really good job explaining the difference in OBD1 and OBD2 systems.

I take it that the temp was reading below the 1/4 mark seeing you never got back to me.

Remember to reset the computer by pulling the negative battery cable and the ECM fuse to reset the computer completely. This will allow it to learn the proper fuel curve faster.

Yea, our OBDII computer is just the same as the 1996 but just a little simpler.

LT,
Installed the thermostat today.
All is back to norm. now,just some annoying bubbles in the heater core making noise,nothing a little flogging wont take care of in the morning. :naughty:

How long do I need to leave the Neg. cable unhooked to erase the memory? Is there a set length of time,or just momentary.?

Thanks in Advance.

Time to start a new post as the "Exhaust Question" title is getting old.

Hey, while you are at it, I know what is causing your heater core bubbling.

Install a NON ACDELCO rad cap and it will be fine.

The stock AC DELCO caps have a fibrous rubber gasket that fails miserably allowing air into the cooling system when the engine is turned off and the rad and coolant is contracting. What happens is that instead of sucking coolant from the overflow tank it will suck in air through the bad gasket, hence the air in the system.

If you rad cap is stock, replace it with a standard full rubber gasket rad cap rated at 15-16psi and your problems will be gone.