Low Boost, Catback questions

[Boostmaniac]

Ok, I have been in the rotary game for a long time, but I have 2 questions I have never really seen asked before.

This is the one that you all are allowed to flame me on. I have an S4 TII that is getting ready to be road worthy again. Something was bothering me though about the turbo. I see absolutely no boost until 4k RPMs. This was in dead stock trim with a ghetto cat back install. I haven't verified this yet, but I assume the twin scroll is still completely functioning. At what RPM do you guys start to see boost in your S4 TII's? (I am swapping the turbo out for an S5 turbo and manifold in very good condition to see if this fixes any of my issues.)

Second, I have an 80mm Corksport DP and MP I just installed (to see if cat clogging was the culprit to my boost woes.) and I was wondering if the RB Rev TII Y pipe and Rev TII dual exhausts would bolt up to my configuration. I love the sound of the RB units and was curious if I could save money by just having them bolt up to my current configuration instead of also having to buy the RB DP and MP also.

Any info would be awesome guys and gals. Thanks again.

-Maniac

[djmtsu]

I think you might be OK with the CS->RB set up. I am using an RB DP and silencer to Apexi N1 EVO catback and it all fits perfect.

And a clogged cat might be your culprit for the spool, but I can't help too much as mine is an S5.

[Boostmaniac]

That's what I am hoping also. If it doesn't fit then I am gonna have a Corksport 80mm DP and MP for sale then lol.

At what RPM do you start to see boost on your S5? (this is the unit I am switching to.)

And where would the cheapest place to pick up some RB stuff be? Or is it only available off of their website?

[djmtsu]

I can't remember. I will let you know when I take her for a spin tomorrow.

And just so you know, I have a stock ported engine, an insanely ported wastegate and no emissions with a cone filter. All that CAN make a difference in spool.

[Boostmaniac]

I have stock ports, stock wastegate, massive DP and free flowing intake. I expect similar results.

[Apac tii]

I think I started to see boost around 2500-2700 RPM when I was still stock can't remember for sure though. I think you might have a clogged cat that might be why you aren't seeing any boost till 4k.

[Rotary_Rocket_87]

I have no cat in my s4 and I see positive pressure starting at about 2500 and full boost before 4000. Stock ports, stock wastegate.

[RETed]

Something was bothering me though about the turbo. I see absolutely no boost until 4k RPMs. This was in dead stock trim with a ghetto cat back install. I haven't verified this yet, but I assume the twin scroll is still completely functioning. At what RPM do you guys start to see boost in your S4 TII's? (I am swapping the turbo out for an S5 turbo and manifold in very good condition to see if this fixes any of my issues.)
I bet that "ghette cat back" was too restrictive.
Boost is also relative to engine load.
1st gear pull is not going to have as much boost as a 5th gear pull.
In general, the turbo starts to make positive pressure in the 2,500RPM range.
The twin scroll acutator kicks in at around 2,800RPM.
It should be making full boost by 4kRPM.
S5 turbo can make positive boost as low as 2,000RPM.

Second, I have an 80mm Corksport DP and MP I just installed (to see if cat clogging was the culprit to my boost woes.) and I was wondering if the RB Rev TII Y pipe and Rev TII dual exhausts would bolt up to my configuration. I love the sound of the RB units and was curious if I could save money by just having them bolt up to my current configuration instead of also having to buy the RB DP and MP also.
I'd be surprised if it does.
The "Rev" spec exhaust is supposed to be proprietary, so it doesn't match with any of the stock "breaks".


-Ted

[Boostmaniac]

I bet that "ghette cat back" was too restrictive.
Boost is also relative to engine load.
1st gear pull is not going to have as much boost as a 5th gear pull.
In general, the turbo starts to make positive pressure in the 2,500RPM range.
The twin scroll acutator kicks in at around 2,800RPM.
It should be making full boost by 4kRPM.
S5 turbo can make positive boost as low as 2,000RPM.


I'd be surprised if it does.
The "Rev" spec exhaust is supposed to be proprietary, so it doesn't match with any of the stock "breaks".


-Ted

Yeah, the ghetto catback was some knockoff N1's.

All of my boost woes happened in any gear at full load. I didn't even start seeing positive pressure until 3800 or above (using a mechanical boost gauge). I do have a dyno from a baseline pull I did and it is a little obvious when you are looking at it. Hopefully this S5 turbo takes care of the issue. Positive pressure in the 2k range would make my year!!!

On the exhaust.... damn. Guess I am gonna have to get the whole thing then :(

[RETed]

Be sure there's no leaks...
Intake leaks can cause loss of boost too. :(
Does the car make loud PSSSSSSSSHHHHHHHH noises when it's boosting?


-Ted

[josh18_2k]

hows your timing? i know retarted timing will spool the turbo super fast, so im guessing the opposite is true?

[J-Rat]

You mean advanced timing?

[RETed]

Yeah, it'll produce boost, but it won't go anywhere...i.e. no power.


-Ted

[Boostmaniac]

Be sure there's no leaks...
Intake leaks can cause loss of boost too. :(
Does the car make loud PSSSSSSSSHHHHHHHH noises when it's boosting?


-Ted

To the best of my knowledge, I have 0 intake leaks. There is no boost leak I can hear while in boost, and I have thoroughly checked for intake leaks since replacing my TID. I should get my new calipers in today and be able to swap out the turbo while I am under there. I just want to have some more low end power than the nothing I have right now. I just picked up an FCD for testing purposes so I guess I'll check it all out if I am lucky enough to get it all in.

Also, I have checked timing and stabbed the CAS appropriately. My timing is literally spot on.

[Phoenix7]

How ghetto was the ghetto catback?

2.5"? 3"? were you using silencers?

Low-end power and RX-7 don't really go together. You can expect it to be quick but you can't really make too much low end power (I assumer you mean full boost >3000RPMs?)


Also, please make ACCURATE, REAL THREAD TITLES. Everyone has questions. You need to be more detailed so future searches yield GOOD results RIGHT AWAY.

[J-Rat]

Low end power is a wide argument.. I make 400 ft/lbs of torque, which is stump pulling power. Its more a question of how usable the available power is.

Chances are if its a stock turbo and its not spooling then the twin scroll is not working or the turbo itself is malfunctioning. A 2.5 inch system wont choke a stock turbo, nor will it choke a big single, since I am still on a 2.5 inch catback.

Rat

[Phoenix7]

Low end power is a wide argument.. I make 400 ft/lbs of torque, which is stump pulling power. Its more a question of how usable the available power is.

Chances are if its a stock turbo and its not spooling then the twin scroll is not working or the turbo itself is malfunctioning. A 2.5 inch system wont choke a stock turbo, nor will it choke a big single, since I am still on a 2.5 inch catback.

Rat
I noticed my boost go down to 10psi on a 2.5" catback (now on our NA) mated to my 3" DP and midpipe from 12psi (with the 3" open cat-back single).

[Boostmaniac]

I was leading more towards the twin scroll not working or the turbo malfunctioning, which sucks seeing as that turbo doesn't leak any oil.

Is there any way to test the twin scroll outside of the car or do you have to actually remove the turbo to do it? I've never really thought about messing around with it before lol.

I do believe that piping was 2.5 on the catback system. I will be removing the turbo either today or tomorrow depending on my situation when I get home. I'll run it through some tests and take some pics.

[djmtsu]

I edited the title of the thread so it is easier for members to see what is in it. Also, it will make a search easier for someone.

[Boostmaniac]

I edited the title of the thread so it is easier for members to see what is in it. Also, it will make a search easier for someone.

Thank you kind sir. I did the title mainly to just get some laughs. I didn't think it would go this long.

[J-Rat]

I noticed my boost go down to 10psi on a 2.5" catback (now on our NA) mated to my 3" DP and midpipe from 12psi (with the 3" open cat-back single).

Did you re-adjust the boost controller to compensate for the difference in pressure differential? As with anything else on this and other forums, its all up to personal experience. I can hold 25 PSI all day long to the redline on my 2.5 inch catback. Is it optimal? HELL NO! At my HP level I should be more on a 4 inch exhaust.


The thing that bothers me is that the car is STOCK. Even a stock turbo with a pre-cat, main cat, and crappy stock exhaust system should spool faster then that. All things being considered, I am not entirely convinced its the exhaust. It sounds like how my car ran years ago when I thought I would be smart and wire the Twin Scroll open.

[Phoenix7]

You're most likely right since he's not boosting when he should be.

No, I didn't change anything, I swapped that catback in to pass visual and have a "modified exhaust" ticket written off.

[J-Rat]

Could be a crappy turbo too.. I am not there to check shaft play, etc.. Course there would be an appreciable increase in oily residue/smoke.

[Phoenix7]

crappy and/or old (high mileage toasty turbo)

[Boostmaniac]

Did you re-adjust the boost controller to compensate for the difference in pressure differential? As with anything else on this and other forums, its all up to personal experience. I can hold 25 PSI all day long to the redline on my 2.5 inch catback. Is it optimal? HELL NO! At my HP level I should be more on a 4 inch exhaust.


The thing that bothers me is that the car is STOCK. Even a stock turbo with a pre-cat, main cat, and crappy stock exhaust system should spool faster then that. All things being considered, I am not entirely convinced its the exhaust. It sounds like how my car ran years ago when I thought I would be smart and wire the Twin Scroll open.

That made me laugh.

Ok, during my general overhaul of my braking system yesterday, we got to the turbo to start removing it and swapping it out with the S5 unit and I made a few notable discoveries.

There seems to be no oil coming out of the turbo, shaft play is minimal to none that I can tell. I'll be able to make a better assessment once it is removed from the car. I did notice something on the compressor wheel, but I need to get a pic to show you, I can't quite explain it on here adequately.

I did see the twin scroll rod and it does seem normal. Maybe it is malfunctioning, maybe it is wired open and I just can't see it. Again, upon further removal, I'll be able to give you all the down low.

If it isn't the exhaust (which should help me out a little bit) then it is either the turbo or my engine. I am praying it is the turbo, I don't want to rebuild just yet. I just want ONE GOOD PULL the way my car is supposed to pull.

The pics should be high quality also, my buddy that is helping me has been bringing over his incredibly awesome camera.

Edit:

Don't laugh at this. I believe in doing baseline pulls on a dead stock car to see where any improvements I make can be found and to also give accurate reports back. This is my baseline pull, dead stock, crappy catback exhaust.

http://i76.photobucket.com/albums/j22/Rotary_cowboy/Dyno/Dyno6-19-06Power.jpg

The car was at WOT at 2500, the target window started at 3000. Boost on this pull didn't really hit positive (maybe 1 psi max) till about 3500 - 3800. Yes I know the AFR is pig rich, that is getting fixed very soon. Yes I also know my power peak is 1k higher than it is supposed to be and I can't explain that at all. Also worth noting, this car has NO acceleration until it gets into boost and it still makes power to 8k or higher and it will hold boost the entire way.

Next time, I'll see if I can datalog boost if I am still having the same problem. There ya go, tell me what you think.

-Maniac

[RETed]

If that black, jagged line is your AFR, it's all over the place... :(
Fix issues like that first, cause that can cause low boost and low power problems.


-Ted

[Boostmaniac]

If that black, jagged line is your AFR, it's all over the place... :(
Fix issues like that first, cause that can cause low boost and low power problems.


-Ted

Oh yeah, that is definitely getting fixed. On one of my runs, it dropped into the NINES. I swapped out the 02 sensor and discovered that someone had been kind enough to have never changed it in 20 years. I have seen thousands of 02 sensors, but never one this bad. It literally came apart in my hands. So I have a new one on there and I am watching it with a narrowband at the moment. I'll be getting the Rtek 2.1 and pull some fuel out while using a real wideband and try to smooth it out all around.

On the low end though, it is sitting around the 13's pre boost which isn't half bad. So unless my timing maps are messed up also then I have no idea.

I'll continue tearing into it today. I'll see if I can get some pics up to let you all see this craptastic issue.

[Boostmaniac]

Ok, after tearing into it and removing the turbo, this is what I found. The turbo was like this when I bought the car.

http://farm3.static.flickr.com/2330/2438986305_dac3c9328c_b.jpg


Yeah, that can't be good in any way.

But the good news is that I already have a replacement.

S5 is on the left.

http://farm3.static.flickr.com/2224/2438987175_f02b243508.jpg?v=0

So, you all think that might have been what was causing me issues?

[Phoenix7]

Take it apart and tell us or send it to BNR and have him tell you

[Boostmaniac]

I'll take the compressor housing off and try to get another pic.

Look at how eaten up the blades are though.

I have no idea how they got bent that way at all.

[Phoenix7]

Holy crap, I didn't even notice, I was looking at your wastegate and oily crap!

[Boostmaniac]

Yeah, we both looked at it and didn't notice it was that bad at first. I have a working theory on how that got that bad, but I think I don't care lol.

This S5 HAS to perform better than that turbo.

Gimme your honest .02 on it.

[J-Rat]

YUMMMM!! Chomp chomp chomp!!!!! Something went through that bad boy! Wonder if it wound up heading out of the engine too.. What does the turbine look like?

Might explain your boosting problem....

[RETed]

So, you all think that might have been what was causing me issues?

I think so... :(


-Ted

[Boostmaniac]

Turbine looks A ok. Now I just have to wrestle this S5 manifold on there followed by the turbo.

Soon enough, we shall be finding out either way.