Exhaust backpressure testing . . .

[ColorCode252]

I am trying to figure out if the cat converter is clogged or getting clogged.

Looks like a simple test, see link -

http://www.genuinesaab.com/catalog/product_info.php?cPath=35&products_id=426

Does anybody know a shop in LA or OC that can do this type of test?

thanks!

[Doug242ti]

Seems to me just unbolting the cat (if possible) would tell you almost the same thing and would be free. ;-)

[stevehayes01]

Do you have a stock Down Pipe ??? If so then the gauge testing may be the better way to go. But if not then I would say that Doug's idea would be the best bet.


Why do you think the Cat's clogged? Are you getting egg smells from the exhaust?

[ColorCode252]

Doug and Steve - thanks for the responses . . .

Well, I do not have the stock downpipe anymore so I cannot do that test. Moreover, I can't unbolt the cat converter. It's tempting to run this mule catless but too much of a hassle, he he he.

Just a little bit of a background as to why I am asking about the backpressure . . .

The '96 900, slushbox, is fairly modified with a better flowing intercooler and a 3" exhaust from turbo to tip while the cat converter is magnaflow. The car has 153k miles. :smokem:

I have had the Nordic Stage 3 ECU plugged in but it aint giving the power. Base boost is approximately 6.5 lbs. I have used my spare APC valve to see if that is cutting boost. Result is the same. it's like the ECU senses a knock event and backs off the boost. My tech spent almost three hours going over the car for leaks and loose hoses and whatever (checked plugs, used my new ignition cassette, blah, blah) since after base boost was adjusted from 5 to 6.5, the overall boost is almost 11psi. :confused:

In a way, after base boost was adjusted, the overall boost that I was getting sort of adapted down. :mad:

The wastegate was tested to see if it blows open on boost Guess what, the wastegate held shut at 19 psi. The boost needle went all the way past the red zone and held it with no problem, that was so so so cool! :D

I have been using Shell 91. Changed that to Chevron, Mobil, Exxon, and 76. Still the same. I even got a new PCV check valve thinking that the valve I have is defective. Hence, it is allowing oil into the intake - lowers octane rating, ECU backs off. God knows how many times I reset the ECU . . .

The US distributor of Nordic and my tech talked over the phone. My tech thinks the car is running well inspite of the attained milage while the US distributor thinks I have a hardware problem with the car. By the way, the HG was replaced two months ago, he did a compression and leak down, and all is well with the car.

So, that is the reason why I am asking about the backpressure. I am trying to eliminate the hardware part of the equation.

The wrap-up of this long story is that I will get another ECU from Sweden. :rolleyes:

I am hoping that this is a software issue. If I get the same shit from the 2nd ECU, I am going to throw the towel and get my $$ back since I do not know what else to do.

Just a little bit frustrated. :(

[stevehayes01]

Andrew had this same problem with the Nordic Stage III on a T5 car. He went through everything and could not get the thing to boost to the full potential. Hows your DIC??


Also for the stage III your base boost should be sitting around 8-9PSI and not 6.5 from what I recall Nick posting up about it.


Raise the base boost up and go from there. I would get Nick on the phone and ask him what the next steps are here since your mechanic sorted the car and its all good. Also for the exhaust you can check if its a clogged cat by unbolting the DP from the rear section and checking with a Maglite to see if you see any obstructions in the pipe. Also if its a cheap cat you may find large chunks of ceramic material in the pipe.

oh and for another test try putting a helper spring on the WG to see if it holds pressure longer.

[ColorCode252]

Andrew had this same problem with the Nordic Stage III on a T5 car. He went through everything and could not get the thing to boost to the full potential. Hows your DIC??


Also for the stage III your base boost should be sitting around 8-9PSI and not 6.5 from what I recall Nick posting up about it.


Raise the base boost up and go from there. I would get Nick on the phone and ask him what the next steps are here since your mechanic sorted the car and its all good. Also for the exhaust you can check if its a clogged cat by unbolting the DP from the rear section and checking with a Maglite to see if you see any obstructions in the pipe. Also if its a cheap cat you may find large chunks of ceramic material in the pipe.

oh and for another test try putting a helper spring on the WG to see if it holds pressure longer.

Hey Steve . . .

a) The ignition cassette is new, same thing/result when I had the one that I have been using.

b) With the base boost of 5lbs, the car made 11lbs. My tech had a boost guage and TECH2 all hooked-up. After base boost was cranked to 6.5lbs, the boost dropped to 10.5 something. Boost was consistent all through out the run. My tech noted that he passed a CHP at 70-80. Thankfully, nothing happened. :p

c) The cat is magnaflow. I thought that was good. I have seen pictures of ceramic "chunks" from a cheap cat. Ok, this may be worth checking over. By the way, I don't smell any sulfur or rotten eggs.

d) Wastegate - The boost needle, with the W hose disconnected from APC, plunged into the red after I punched the gas pedal. That was a fun three second acceleration on the freeway. :cool: The needle did not back off while I did not get a fuel cut. So that would tell me that the wastegate held shut. My tech did the same test with a boost guage and TECH2 and got the same result. He recorded 19lbs.

e) I have two APC/BPC valves - no change since the boost needle would touch the red zone then back off at the end of yellow while boost would hold that spot unless I let off the gas.

f) I have thought about the wastegate spring helper and I even the asked my tech if he thinks that I have a weak WG spring since I used the MBC+A for six months. He does not think that the WG spring is weakened since boost is consistent. Boost was not fluttering, no fluctuation. The car feels like I am running the stock ECU.

g) My tech and Nick talked over the phone after my tech did his testing. Nick will send another ECU.

By the way, Drew and I have exchanged emails over this . . . .

More to follow . . .

[ColorCode252]

1

[stevehayes01]

With the MBC in place can you hit red on the gauge???


You may want to put in the MBC and see where it goes on the gauge and compare that with a tech 2 to what the ECU did just to rule out hardware.

[ColorCode252]

With the MBC in place can you hit red on the gauge???


You may want to put in the MBC and see where it goes on the gauge and compare that with a tech 2 to what the ECU did just to rule out hardware.

I sold the MBC+A. :rolleyes:

When I had the MBC+A and the stock ECU, I hit the red consistently about 1/3 in the red zone. That only happens if I flog the car from 60mph and onwards.

The drawback with that set-up is that I get a lot of fuel cuts since I have an autobox.

With a manual tranny, boost can be dumped a bit from shifting then regained after shifting to a higher gear.

You know, maybe this is what I can only get with the stage 3 set-up since I have an autobox with the T25 turbo.

[stevehayes01]

No Abdukteds car (TD04) is hitting 19PSI on an autobox.... You should be hitting 15-19PSI in your car with the T25. IT has to be the tune on the ECU. Thats all I can think of at this point. Especially when you were able hit red on the gauge with the MBC and now all of the sudden you cant.


From the time you had the MBC have you made any h/w changes to the car? or anything different?

[ColorCode252]

Yeah . . I have seen pix and mods of that automagic. :tup:

You know, my car has 153k miles although in good condition for its age. Heck, maybe I'll christen my car - "Mrs. Robinson." ;) I guess, that's the pitfall if you start modding.

I have the same hardware mods - viggen intercooler and the 3" exhaust from turbo to tip.

Oh yeah, a K&N filter (plus airbox DIY CAI) but I really would not call the filter a mod.:p

[stevehayes01]

So anything new with the ECU dilema???