The White Bug (Page 13/46)
wftb MAY 11, 01:30 PM
Use a bigger exhaust pipe and get rid of the muffler. You need more total flow capacity, even if you do everything on your list the 2.5" pipe is still a choke point. I use 2.5" piping on my engine and if I had room I would go bigger. I have a Solstice OEM cat converter and no muffler. Only loud when you build the boost up high, rest of the time it is fairly quiet.

------------------
86 GT built 2.2 ecotec turbo
rear SLA suspension
QA1 coilovers on tube arms

La fiera MAY 11, 02:27 PM
I think you'll need an external wastegate.
ericjon262 MAY 11, 02:40 PM
idea:

the inlet and outlet of your muffler are inline, weld a V band to the inlet and outlet, and in between porting the housing, and installing the larger housing, take an intermediate step of installing a straight pipe. if boost control is improved, it tells you your muffler/exhaust is too restrictive, if it isn't improved, you can re install your muffler, and have an alternate exhaust for track days that is an easy bolt in install.
My thoughts:

if the exhaust is too restrictive, it will drastically reduce turbine and WG efficiency, because the pressure drop across the two components is reduced. reducing pressure downstream of the turbine will make boost control easier and more consistent, as well as reduce "spool" time. while straight through mufflers appear to be very free flowing, some actually choke down engines quite considerably.

------------------
"I am not what you so glibly call to be a civilized man. I have broken with society for reasons which I alone am able to appreciate. I am therefore not subject to it's stupid laws, and I ask you to never allude to them in my presence again."

cognita semper

http://www.fiero.nl/forum/Forum2/HTML/119122.html

pmbrunelle MAY 12, 08:44 AM
Considering my main problem now is that the turbine is generating too much shaft power, I don't think that unrestricting the turbine's exit will help it generate less power.

However, the wastegate would do a better job of stealing flow away from the turbine if it dumped to a short non-restrictive exhaust, such as a screamer pipe.

This is what the wastegate passage looks like for exhaust gas entering the inlet flange:


I think that this Saturday I will go to Princess Auto and purchase an electric die grinder + burrs. I need something more powerful than my Dremel to port this.

Even if porting the wastegate passage doesn't solve my immediate problem, the electric die grinder will be a useful tool to have. I don't have a big enough air compressor to run an air-powered die grinder.

[This message has been edited by pmbrunelle (edited 05-12-2020).]

Will MAY 12, 09:46 AM
If you could add as much radius as possible on the near edge while keeping the far edge sharp, that would help. Not sure if porting the wastegate port can get you where you need to go, but it's worth a shot.
claude dalpe MAY 12, 12:23 PM

quote
Originally posted by La fiera:

I think you'll need an external wastegate.




Your wastegate comes out in your restrictive exhaust which prevents it from operating at full capacity!
pmbrunelle MAY 17, 08:38 PM
I ported the wastegate passage. There is a radius of about 0.4 inches on the inside of the turn. I left a sharp edge on the far side.


Looking into the wastegate hole towards the inlet flange, with a light shining into the inlet flange:


The shape of the turbine housing lent itself to me carving a scoop shape to help divert exhaust gas towards the wastegate passage.

2nd gear pull from 905 RPM to 6131 RPM, followed by a 3rd gear pull:


During WOT, manifold pressure stabilises at about 155 kPa.

To see what would happen without engine acceleration, I brake boosted the car on the highway for a few seconds. Manifold pressure remained stable. I noticed that stock 84-87 brakes heat up quickly!

[This message has been edited by pmbrunelle (edited 05-17-2020).]

La fiera MAY 17, 08:53 PM

quote
. I noticed that stock 84-87 brakes heat up quickly!



Patrick, you being an engineer I thought you have the brakes upgraded for the forecasted HP. How did you spect the stock brakes to keep up with the demands?
Sometimes is a matter of trial and error, I've been there myself! "Keep pounding" like we say here in NC!
pmbrunelle MAY 17, 09:04 PM

quote
Originally posted by La fiera:
How did you spect the stock brakes to keep up with the demands?



I didn't!

I suppose you could build up every system of a project car, and then fire up a finished car and go driving.

In addition to working on the car in the garage, I wanted to drive it even though it's not finished! Driving the car is also how you discover problems.
La fiera MAY 17, 09:31 PM

quote
Originally posted by pmbrunelle:


I didn't!

I suppose you could build up every system of a project car, and then fire up a finished car and go driving.

In addition to working on the car in the garage, I wanted to drive it even though it's not finished! Driving the car is also how you discover problems.



Keep at it!!!! Good job mate!!