I just found out the headers I orderd don't come with an EGR tube.

If I block off the tube, other than throwing a code, what kinds of problems am I going to have, if any.

I blocked off the EGR on another motor I built, but that was a carb motor, not FI.

What could result in this?

Thanks.

 

Your intake will be cleaner, your car will be lighter, and your car will be easier to work on. Your car will not throw a code. Really, your car thanks you.

 

should have no problems.

 

Higher NOx emissions, a greater tendency to knock at advanced part throttle, and reduced fuel mileage.



THAT depends in the year. Some will, and some won't.

RACE ON!!!

 

1990. As I only put 1000 miles a year on the car, I am not too concerned with mileage.

When you say "greater tendency to knock" how much greater. Should I retard the timing. I'm currently running 15 degrees. Should I knock that down? (pun intended)

 

Yes. I remember he is putting in a different cam though. IIRC it has enough overlap to act as the EGR system and prevent the above, do you agree? I do not know a ton about the EGR system, that is why I ask. I did delete it on mine, no codes, no troubles. Stock cam till next season.

 

If emissions and mileage are of no concern, then ping is the only issue. How did you get to 15° BTDC? Trial and error, I would guess. Use the same method to determine if and how much a change is needed with the elimination of the EGR. Remember, it won't make any difference at WOT, because, A) there is no signal from the ECM at WOT, and B) there is no vacuum at WOT to open it, anyhow.



I don't know anything about his cam. In later years, his 1990 for sure, there is an EGR temperature sensor that tells the ECM if the EGR isn't working, such as if it was disconnected. THAT will trigger the Check Engine, or SES, light and set a code. No cam will satisfy that EGR temp sensor.

RACE ON!!!

 

When I was traveling I had Corvettes of Westchester, a local tuner, put in new injectors, tune up the car, and do a little tuning.

He came up with the number. A little knowledge and a little trial and error.

I have the FSM and it may be in there. However, is there a way to "trick" the sensor until I can get it tuned out of the chip?

As far as the cam goes, I settled on the Accel 74219. However, talking to a local engine builder, they are going to put my build into their computer and see if there may be a better cam. So the cam is up in the air right now. However, I am leaning the 219. Here's the specs:



350 – 383 CID SBC Engine with SuperRam Plenum Runner Cam # 74219 219/219 duration @ .050 .560"/.560" with 1.6 rocker

https://ssl12.chi.us.securedata.net/...0b44cbf27c931c

 

Since you will need a chip made for your new combination, just tell your chip tuner that you have deleted EGR, they will take out the Code 32 and EGR functions.

There will be more tendency to knock, particularly when the engine is hot, as EGR functions when the engine is up to temperature at part throttle and its function is to lower combustion chamber temperatures.

 

Any way to deal with the knock? Cooling the engine, retarding the timing?

 

Dont let the engine get too hot, and leave everything else for the chip.

Dont retard your base timing.

 

Only time will tell if it will need to be changed.



None that I am aware of.



All that makes no difference. Like I said, "No cam will satisfy that EGR temp sensor."

RACE ON!!!

 

Does the car knock because the EGR is missing?

Or does the EGR missing make the car run hotter, causing the knock? If this is it, I can do something about that.

I already have the fans coming on at 90*C and a 160* thermostat, The car ran pretty cool before I did the work.

 

What?

 

The exhaust gases introduced by the EGR valve, dilutes the air fuel mixture so it doesn't burn as hot as it otherwise would nor create as much pressure. Lower cylinder temps and pressures are less likely to knock and they also produce lower NOx emissions.



The car doesn't run any cooler with that thermostat than it would with one that promotes quicker warm ups.

RACE ON!!!

 

I am dropping the compression, as my heads are 58CC and I'm going to 64CC heads, that will drop compression by about 3/4 point to 9.5. By lowering the pressure, will that compensate somewhat?

As far as cyl temps, can't I put in a cooler plug. I think the car uses the AC R45 TSX. I can go to something like R43 TSX and lower the temp.

Would those two steps not address some of that?

 

I wouldn't worry about knock yet....if you get a tune from a tuner w/a good rep. he will start conservatively, set initial @6 * and leave it alone. With any real mods, it will require some "playing" w/the tune (fuel, timing etc. etc.) and is part of the territory. As long as it is in controll from the ecm in C loop and the KS is working, even if you get some knock counts, it will be pulling back the timing. Rich or lean areas can also produce K counts, and until fueling/timing is corrected (w/a map car in particular) in the tune you will get some. In this case of a modded motor, teh EGR is very easy to dis-able from the tune, and is the least of the issues. If I can make a suggestion, get to used to using some software (ie. datamaster or tuner pro, whatever flavor), to actually understand what is going on(rich/lean etc.etc.).

 

Hey man.... How's the car running? I wouldn't be concerned about knock or ping until it happens....

I've installed a low temp stat in your car, and turned on the fans earlier in the computer.....If you continue to use 93 octane or better, you should not have any pinging.....

By the way.... I've messed with the timing in the computer, remember to use the timing light numbers as a reference only.......and also remember that the "initial" timing is skewed from stock.....

ALL C4's have a tiny amount of "burst knock" even with stock timing....I wouldn't worry about it....

As far as changing heads...DO NOT put 64CC heads and add a cam... You'll be spending a bunch of money for nothing.... The compression is kinda low even with stock heads and making it a point lower will totally dog the motor.......

The key to making the TPI motor "wake up" is a cam and "big mouth" lower intake manifold.....Lowering the compression will negate those mods.....

If you really want to wake up the car..... Put a PRO TORQUE converter in the trans (for autos) and all vettes NEED a better rear axle ratio....

The rear end is the most cost effective and reliable way to improve the performance of ANY year corvette....

While you can "wake up" the motor in any TPI car.... the real performance comes from the drivetrain mods...... Start with the rear end first and then see how far off you are from where you want to be.....Trying to build a bigger TPI motor before changing the rear will cost much more and surely take away from driveability....

Call me if you have any questions.....
Chuck CoW

 

Your '90 WILL throw a code on occ. Usually during light throttle highway use. I deleted that error code while burning my chip for larger injectors...

 

HEY CHUCK!! Car's running great. That's why I'm taking it apart!

I know.....I know.....but hey, everyone needs something to do.

I picked up a complete Super Ram that I'm going to install. Of course, can't have the Super Ram without the matching cam. Then of course, the heads are the weak spot, then the exhaust......and so it goes on.....

One of two things are going to happen. Either I can't get it to run (which really isn't going to happen) and I'll have to have you correct it.

Or, once I get it to run, I'll bring it up to you for tuning.

Once I decide on heads, I think AFR is a little to proud of their heads. I'm looking at Brodix and Patriot at this point. I hear what you're saying about compression. I can get 62CC heads which will put the compression at 9.5:1, the factory is 10.25. I've done all the math and feel pretty comfortable with that number. 9.5 is where the older L98s run. I can't find heads smaller than 62CC.

As far as the torque converter, that's my next step, after the engine work. Then a shift kit. At which point I take a breather and see what I like or don't. I'll go from there. There's only so much money to go around, so I have to stagger the build.

The issue is, the headers don't have an EGR provision, so I have to eliminate it. I didn't want to, just have to.

So far I have the front of the motor apart, the radiator out, the exhaust is gone, and the air system has been eliminated.

Another advantage to doing heads, is the headers should slip right in.

I got all new ARP bolts and it's being done right. The only two things I am keeping are the lifters and timing chain. They only have 32K miles.