Supercharger Exhaust Setup Question

Racer75

Tuner
Points
107
Location
Scotland, Glasgow
Car
BMW 323i (e36)
Hi all, looking for a little input on something I have been thinking about recently.

My car has the original exhaust setup, which is a twin pipe 2" exhaust from the headers to the backbox. I have fitted a supercharger and am running at approx. 0,4-0,6 bar of boost and have noticed an increase in power but have also noticed a slightly hesitancy with the throttle at low revs (1500-2500), however, my question is, if I was to build a custom system and upped the pipe diameter, would this cause any damaging effects to the system on a whole? I understand that is a loaded question and very difficult to answer if you haven't seen or driven the engine/car, but there are so many different forum posts, most with contradictory points, and I was hoping for some clarity.

I haven't yet purchased anything yet, but my plan would be to build the system as below (2 pipes to catalytic converters, then 1 pipe to exit);

Front to back;

2x 3 to 1 Exhaust Manifold, feeding in 2x 2.5" pipes >
2x 2.5" 400cel cats >
2.5" to 3" Y Piece
3" Pipe, with 2 45degree joiners
3" Resonator / backbox

Unfortunately, I don't have access to any Dyno garages or any close tuners, so that is a certain disadvantage, but I was looking over my setup and the only thing I have not touched is the exhaust system and am aware people have fitted 3" pipes to N/A cars and claimed a power increase.

As always, any and all advice is appreciated (I really need to buy that book that Fabia recommended!!!)

Cheers
 

TCJBOLDIE

Moderator
Staff member
Points
697
Location
Brisbane
Car
2011 Honda FN2
Things that come to mind are,

1 Check and clean the AFM and fit new air cleaner.
2 Use V band joints where needed.
3 Fit sports cats.
4 Have the injectors cleaned and flow tested
5 Fit new spark plugs.
6 Fit straight thru resonator and black box

I recommend you carry out #1,4 &5 first to see if they solve the problem
 

Racer75

Tuner
Points
107
Location
Scotland, Glasgow
Car
BMW 323i (e36)
Things that come to mind are,

1 Check and clean the AFM and fit new air cleaner.
2 Use V band joints where needed.
3 Fit sports cats.
4 Have the injectors cleaned and flow tested
5 Fit new spark plugs.
6 Fit straight thru resonator and black box

I recommend you carry out #1,4 &5 first to see if they solve the problem
I have actually carried out 1 & 5, the injectors were bought second hand from a breaker and I was assured that they were checked before I got them.

Thanks though, always worth doing the easy stuff first
 

TCJBOLDIE

Moderator
Staff member
Points
697
Location
Brisbane
Car
2011 Honda FN2
I would venture to think that the breaker checked that they actually worked BUT did he have them properly sonically cleaned and tested?

Injectors will still "work" when partially blocked but won't supply all the fuel needed.

Sorry if I sound a bit a bit skeptical but have been there done that but also do my own tests / checks to confirm things .
 

Racer75

Tuner
Points
107
Location
Scotland, Glasgow
Car
BMW 323i (e36)
I would venture to think that the breaker checked that they actually worked BUT did he have them properly sonically cleaned and tested?

Injectors will still "work" when partially blocked but won't supply all the fuel needed.

Sorry if I sound a bit a bit skeptical but have been there done that but also do my own tests / checks to confirm things .
Very true, might be worth just buying a brand new set seeing as they’re not very expensive
 

TCJBOLDIE

Moderator
Staff member
Points
697
Location
Brisbane
Car
2011 Honda FN2
I bought a set of NEW 1000cc injectors for my old car drove to my tuner fitted them only to find that 1 was faulty.

The supplier reimbursed me for injector testing as well as the dyno time plus labor to remove and refit them and tested the new set before returning them.

Might be 1 in a million for that to happen.

FYI the faulty injector was discovered when on the dyno being retuned.

He called me to check on the injector size as they were larger higher flowing injectors and he was having to ADD FUEL when he should have been tweaking them for LESS fuel due to them being upgraded from 800 cc to 1000cc's

I used the same dyno tuner many times over the years previously to tweak the tune after various mods
 

Fabia17

Torque Junkie
Points
322
Location
Lincoln UK
Car
Fabia Monte Carlo
Hi all, looking for a little input on something I have been thinking about recently.

My car has the original exhaust setup, which is a twin pipe 2" exhaust from the headers to the backbox. I have fitted a supercharger and am running at approx. 0,4-0,6 bar of boost and have noticed an increase in power but have also noticed a slightly hesitancy with the throttle at low revs (1500-2500), however, my question is, if I was to build a custom system and upped the pipe diameter, would this cause any damaging effects to the system on a whole? I understand that is a loaded question and very difficult to answer if you haven't seen or driven the engine/car, but there are so many different forum posts, most with contradictory points, and I was hoping for some clarity.

I haven't yet purchased anything yet, but my plan would be to build the system as below (2 pipes to catalytic converters, then 1 pipe to exit);

Front to back;

2x 3 to 1 Exhaust Manifold, feeding in 2x 2.5" pipes >
2x 2.5" 400cel cats >
2.5" to 3" Y Piece
3" Pipe, with 2 45degree joiners
3" Resonator / backbox

Unfortunately, I don't have access to any Dyno garages or any close tuners, so that is a certain disadvantage, but I was looking over my setup and the only thing I have not touched is the exhaust system and am aware people have fitted 3" pipes to N/A cars and claimed a power increase.

As always, any and all advice is appreciated (I really need to buy that book that Fabia recommended!!!)

Cheers
Hi, you have not told us about the motor? What is it, what charger have you fitted, blow off valve, or dump valve, intercooler? Etc. What car is it?
This hesitation in the throttle : is it a flat spot off idle, or is it always there, like if you feather the throttle at low revs does it heditate.

Does it fall in a hole when you gun it off the line?

Does it do it with no load on the engine?

Is the engine stock or modified?

Has been recently rebuilt or how many miles on it?

Give me a this information and I will give you my thoughts.

Thanks.
 

TCJBOLDIE

Moderator
Staff member
Points
697
Location
Brisbane
Car
2011 Honda FN2
Can the slight hesitation be due to the chargers drive belt slipping due to wear or insufficient tension when the throttle is opened suddenly when accelerating ?
 

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