New Acquisition: dohc turbo

Shaun41178(2) · Post by **Shaun41178(2)** » Thu Jul 17, 2008 11:28 pm

I pulled 2 codes today to see what was going on. I got a code 23 and a 44. Not sure if they are the same as the fiero 2.8 though.

Its from a wbody 3.1 I think the computer is.

Would the numbers be the same or different?

If they are the same then I get a MAT sensor and a o2 sensor lean condition.

I know that I discod the MAT when working on it and starting it so I am sure thats from me, but if the o2 says the car is lean then I can see why it would dump a bunch of fuel then causing it to run stupid rich because I guess the computer sees it as being lean.

Does that make sense or am I being retarded like most canadians in the toronto area?

I have Sinister working on a new chip for me now, and I will reset the computer and see if the code pops up again.

Shaun41178(2) · Post by **Shaun41178(2)** » Sat Jul 19, 2008 5:07 pm

any help?

Kohburn · Post by **Kohburn** » Mon Jul 21, 2008 9:17 am

codes should be the same - disconnecting the mat would definately cause the one code

definately resent and try again.

if it is infact getting a bad O2 signal you can try using the second set of wide band outputs to run the ecm instead of the stock narrowband sensor. the wideband outputs should all currently be set to output a standard narrowband signal.

Kohburn · Post by **Kohburn** » Mon Jul 21, 2008 9:18 am

oh BTW - I believe i found the stock 3.1 prom if you want it

Shaun41178(2) · Post by **Shaun41178(2)** » Sat Aug 16, 2008 3:57 pm

Pulled the turbo and crossover pipe the otehr day. The crossover had some pinholes and some shoddy welds in some spots. So I am going to grind those down and reweld the bad parts.

Taking the downpipe off and measured it at 2 inches. This was right out of the turbo after that it was 3 inches but 2 inches has got to go on this thing. I am going to try and make it a full 3 inch system from the turbo to the tip.

Shaun41178(2) · Post by **Shaun41178(2)** » Tue Aug 26, 2008 8:44 am

ordered the new turbo today. SC6162E with a .82 Vband exhaust housing. I need that v band since packaging is tight on the trunk firewall since I want to use a 3 inch downpipe. I'll post pics when it arrives but here is a quick shot

Aaron · Post by **Aaron** » Tue Aug 26, 2008 11:41 am

Baby Jesus hates T3s. He told me so.

Shaun41178(2) · Post by **Shaun41178(2)** » Thu Sep 11, 2008 10:04 pm

someone help me here. This tb has a little black rubber nub in what appears to be the iac feed. It has the two zip ties on it. Is this indeed the iac feed?

I think it is and it is plugged up. So you are probably wondering how it is idling? Simple, someone drilled a hole in the tb plate to get it to idle.

http://www.shaun.saturnet.net/pics/dohc ... lebody.JPG

Shaun41178(2) · Post by **Shaun41178(2)** » Thu Sep 11, 2008 10:17 pm

http://www.shaun.saturnet.net/pics/dohc/100_1513.JPG

http://www.shaun.saturnet.net/pics/dohc/100_1515.JPG

http://www.shaun.saturnet.net/pics/dohc/100_1516.JPG

http://www.shaun.saturnet.net/pics/dohc/100_1517.JPG

http://www.shaun.saturnet.net/pics/dohc/100_1523.JPG

http://www.shaun.saturnet.net/pics/dohc/100_1524.JPG

I got the y pipe welded up. There were like 5 pinholes in it. Its all tigged up now good to go. I just have to figure out wastegate placement. The flange for the turbo is slightly warped. Not sure how I am going to tackle that problem. Warped by maybe a mm or so. A gasket just might be enough, if not a little planing should work.

Turbo came in too. They sent me the wrong housing. I wanted the .82 and they sent the .63 so I have to send that back. I gained some room too with the vband right on the exh housing over the previous setup with the internal gate. I might still need to notch out some sheetmetal in the trunk but we will see once its all mounted. Its going to need to be a real tight 90 degree bend. Its actually going to be closer to a 100 degree bend.

The discharge on the new turbo is 2.5 where as the old turbo was 2.25 on the exh side.

Aaron · Post by **Aaron** » Thu Sep 11, 2008 10:45 pm

Shaun41178(2) wrote:someone help me here. This tb has a little black rubber nub in what appears to be the iac feed. It has the two zip ties on it. Is this indeed the iac feed?

I think it is and it is plugged up. So you are probably wondering how it is idling? Simple, someone drilled a hole in the tb plate to get it to idle.

http://www.shaun.saturnet.net/pics/dohc ... lebody.JPG

The IAC feed and return are internal, casted into the TB. That line is for the breather line off the valve cover. Actually, after looking at it, that may be for the PCV system. I'm not familiar enough with the 96-97s to know for sure, but it is merely a vacuum port, doesn't have anything to do with the IAC.

Some GM TBs came stock with a hole in them. I know many of the standard 3-bolt 75mm throttle bodies had holes in them on the V8 applications, since the V8 needs more air than the 4.3 needs to idle (4.3 got the same TB in the Vortec era). I cannot say for sure if the 96-97 3.4 DOHC throttle body had a hole in it. I have one down in the garage laying around....somewhere. I'll look tomorrow.

The Chassis Shop (I believe) sells a real tight radius 2.5" mandrel bent donut, it's what we use on the 3.4 DOHC exhausts to curve and still leave room for the muffler. However it'd expensive, around $50-$60, and it has a slit around the inside, so you need to weld the inside once you cut it to the right angle. But it isn't that hard to do.

Your Y-pipe looks good. I'm not sure if the pinholes will make any difference, that's something I've always been curious about. At any rate, can't hurt to have them plugged, and that's how it should be. Be careful tightening the Y-pipe on, the 3 ears on each flange like to bend. So tighten slowly and evenly, and don't go too tight. Not that bending them hurts...Will the wastegate fit if you put the source right where the Y is? Like mine is? That's the ideal location, however I doubt you'll have a problem running the wastegate off just one bank. Theory says it doesn't work as well, but I've seen a few cars using it in practice with no ill effects (Including one 3.4 DOHC turbo).

Shaun41178(2) · Post by **Shaun41178(2)** » Thu Sep 11, 2008 11:05 pm

I don't get the hole in the tb. The iac should be able to open far enough to give the motor more air should it not? Thats the whole point of having one.

Thanks aaron for the info. I do want to mount the wastegate where you were talking about, but not sure if it will fit yet(tranny clearing). The externals are so big but Tial is coming out with a low profile 38mm here shortly that I might hold out for pending on release date. Its about half the height of the current 38mm.

Aaron · Post by **Aaron** » Thu Sep 11, 2008 11:12 pm

Shaun41178(2) wrote:I don't get the hole in the tb. The iac should be able to open far enough to give the motor more air should it not? Thats the whole point of having one.

Thanks aaron for the info. I do want to mount the wastegate where you were talking about, but not sure if it will fit yet(tranny clearing). The externals are so big but Tial is coming out with a low profile 38mm here shortly that I might hold out for pending on release date. Its about half the height of the current 38mm.

Well GM IACs are generic to most every motor GM has made (Excluding a few, and the newer drive-by-wire). However, every motor has different idle airflow requirements. And for the V8s, the standard IAC couldn't open far enough to sustain an idle in some environments. So they would drill a hole in the plate, then use the IAC for additional air and control. LS1s, 5.7 Vortec, a lot of the V8s had holes in them. But the 91-95 3.4 DOHC did not, so I wouldn't think a 96-97 would, but you never know.

I haven't seen that yet. I'll look around, I could definitely use one on my car, as my wastegate barely fits. Remember also, with a curved piece of pipe, you can bend the wastegate up/down and left/right, it doesn't need to be perpendicular to the exhaust. But try and keep the pipe as short as possible.

Aaron · Post by **Aaron** » Sat Sep 13, 2008 11:34 am

Shaun, I forgot to check my TB, however realized I had pics of it online. This is a bone stock 96-97 TB assembly, which IIRC is the same TB Kohburn used on your car. As you can see, it does indeed have a hole in the throttle body.

Shaun41178(2) · Post by **Shaun41178(2)** » Sat Sep 13, 2008 12:03 pm

i don't see a pic, but if yours has a hole too then it sounds good to me.

Aaron · Post by **Aaron** » Sat Sep 13, 2008 12:44 pm

There's a pic there. I am crazy and confused, but the messages being sent to my brain say there's a pic there. So when I'm out of control, and I'm out of my mind, just remember one thing, I think I'm just fine.

There is a hole in it, so your's is fine.

However, I do need to apologize, seems I was wrong about the 96-97 throttle bodies. The IAC passage is not internal, with an inlet right before the plate. Turns out, that passage goes to the nipple that is blocked off on your's, which then leads to the valve cover breather. The IAC inlet is the nipple on the very top of the TB, and it faces toward the trunk on your car. So that nipple can be left open, or it needs to plumb into the intake tract somewhere before the throttle body if you want it to only get filtered air. It can be before or after the turbo.

Shaun41178(2) · Post by **Shaun41178(2)** » Sat Sep 13, 2008 1:03 pm

so the iac tube is the one that has the zip ties around it then? your description confused me.

Aaron · Post by **Aaron** » Sat Sep 13, 2008 1:15 pm

No, that is a nipple for the breather line that goes from the valve cover to it.

The IAC nipple is the highest one on the throttle body, and points toward the trunk on your car. In my picture, it is the one seen at the very top right of the photo.

Shaun41178(2) · Post by **Shaun41178(2)** » Sat Sep 13, 2008 1:18 pm

I don't know why but I can't see your pic. Post the link maybe I can click on it and see it.

Aaron · Post by **Aaron** » Sat Sep 13, 2008 1:29 pm

http://img.photobucket.com/albums/v336/ ... 96Z344.jpg

Shaun41178(2) · Post by **Shaun41178(2)** » Sat Sep 13, 2008 2:21 pm

http://www.shaun.saturnet.net/pics/dohc/100_1525.JPG

So I am guessing that these are routed wrong then. The one you say is supposed to go to the intake is actually going to the catch can.