quote Originally posted by ericjon262: you have to manually change the Map sensor values. My main concern right now, is that I have a 3 bar MAP sensor, and I'm told that some of the PCMs similar to what I'm using can only read up to 2 bar... Tiny tuner let me input the values for the 3 bar though, so we will see what happens when I plug everything in and program it... I'll hook the sensor up to my air compressor and run a scan (with the engine off) and see if it stops reading at 2 BAR. if I have to, I'll import the L67 values for it's 2 BAR, and get a 2 BAR MAP sensor.

I find it hard to believe it's that simple, I get the idea of scaling the MAP values which basically requires the natural aspiration portion be condensed into half of the MAP table for a 2 bar, however it stands to reason that you would need to do this for every MAP associated table in the code or risk problems with fueling and spark advance as a result. I've run boost many times in the past with a 1 bar MAP sensor, but I wouldn't dare try it with a 3 bar MAP in non boost related code, the reason being the 3 bar MAP has even less resolution than the 2 bar MAP. Make sure you are working with someone that has succeeded at doing this with the code.

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[This message has been edited by ericjon262 (edited 09-11-2022).]

You really need expansion joints between the logs and the turbo. I did not use them on my first exhaust and each heat/cool cycle would bend the exhaust and turbo until things started breaking.

This is the 2nd attempt. It works great now.


This is how I found them in the junkyard. They are found on crossover pipes on front wheel drive GM cars.

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[This message has been edited by ericjon262 (edited 09-11-2022).]

Buy the size you need, they're available from the same place you purchased your tubing. Aftermarket expansion joints are usually sturdier than OE because they also have a braided steel mesh around the bellows. Although GM has done a better job with them by adding a sheet metal support underneath, the Turbo Grand Prix bellows had a history of cracking and coming apart. If you want to use OE which I've never had a problem with like what's pictured above, get the crossover from the 3500 and up cars as they are larger than what was placed on the 3400, ~1.75-2.00" if needed, I didn't measure it. You may also find the better joint in the exhaust pipe of some imports as they are usually braided also.

It's 4" long, the camera is bending the picture in auto focus, it also has an inner interlocking liner for smooth airflow through it as opposed to exposed louvers.

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quote Originally posted by ericjon262: I am aware that the bellows are available in the aftermarket, the problem I am running into is space, I don' t have a 4" strait run that I can put a flex joint in, on either bank... so I am trying to find a pair in 2" that are under 3" in length. the GM ones look like they may work, and if the do, I'll see if the dealer can get a pair for me.

That's a lot of money to throw away at the dealer for a crossover to cut up as that's the only way you'll be able to get it. Your crossover being as long as it is will probably be fine as it is because the extra length of pipe allows for some flexibility, adding one bellows joint would probably more than suffice. If you look at Hudini's crossover you'll see that it is short and has more of a linear opposing expansion arrangement, where yours is more of a scissor type arrangement.

You don't have to have a perfectly straight section, you can get a bellows one size up that slips over the main pipe with enough room to accomodate a little bit of a curve, cut a small space in the main pipe or better yet make it a slip joint which GM did with some or all of their bellows then weld the bellows ends to the main pipe enclosing the slip/expansion area.

Those joints will be more crucial if you wrap your exhaust, I discourage you from doing that in favor of shielding or some type of heat blanket. I've made a number of mild steel exhaust manifolds using 14 ga steel and they don't do well over the long hall wrapped behind a turbo.

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[This message has been edited by ericjon262 (edited 09-11-2022).]

This is an FYI. You may already know about this but I thought I'd add it in here. I discovered on two transmissions that had exhaust running close to the aluminum casting. One was a stock Fiero with a stainless steel exhaust with no shielding. The other was a turbo setup, again no shielding. In both those cases the aluminum bellhousing had spider cracks all over it. My conclusion was that the heat cycles were too much for the aluminum which is very week at high temperatures. The cracking had not caused a failure but I could only assume that eventually it would have.

This is why manufacturers use double walled tubing on cross overs and a lot of the time on the headers too. To keep the heat away from the aluminum. Especially the transmission which does not have cooling in the bell housing.


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quote Originally posted by Niterrorz: you had me untill the oil filter plumbing

I wish this quote had a like button

Anyway Eric, I do see your reasoning for putting the piping in, but I still think there must be a better/lighter way of doing it. Also you will have to account for the extra volume of oil that will be in there and think about if that might overfill your reservoir.

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[This message has been edited by ericjon262 (edited 09-11-2022).]

The stock crossovers were 1.5" ID same as the stock 2.8L exhaust logs. I wanted high velocity before the turbo so kept everything the same. The exhaust ports on the 2.8L/3.4L iron heads are only about 1" ID stock anyway. How big are those aluminum head exhaust ports?

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[This message has been edited by ericjon262 (edited 09-11-2022).]

I'd stick to something close to your log size to keep the exhaust speed up before the turbo. Could you fit 1.75" ID pipes to your turbo mounting flange? My T3 style mount barely fit's 1.5" pipes.

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[This message has been edited by ericjon262 (edited 09-11-2022).]

LMAO, nerd.

J/K

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[This message has been edited by ericjon262 (edited 09-11-2022).]

man this thing is looking sweet! great job with the car so far!

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[This message has been edited by ericjon262 (edited 09-11-2022).]

Very nice!

thanks, waiting on parts right now, hopefully once they are here I can get some real progress going again...

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[This message has been edited by ericjon262 (edited 09-11-2022).]

RE: Expansion joints.

I had the same trouble with space on my twin scroll mitsu setup with a 3.4. What I figured was that if my front bank had a joint, my wastegate takeoff had an expansion joint, and my downpipe could move (which it can, it's just hung on exhaust hangers, then the rear bank can expand and not cause stress.

In othere words, if you stress relieve all except one, then that one can be free to move.

So far there has been no problems.

I wrapped with DEI titanium and the transaxle is fine so far. Be very carefull with heat around the shift cable ends...they get soft and slip off the ball studs.

Chay

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