Performance is Exhausting !

[Ianmc]

We sometimes forget that the car is designed as a "system", in this case inlet/engine/exhaust. Much goes into designing the best solution, within limitations such as cost/reliability/usability (for the average whoever he is). If we change one aspect, it is likely we will impact the whole, which might be the desire (such as sound) but there is often a downside that may or may not be acceptable. Just a thought.

 

[Pingu]

We sometimes forget that the car is designed as a "system", in this case inlet/engine/exhaust. Much goes into designing the best solution, within limitations such as cost/reliability/usability (for the average whoever he is). If we change one aspect, it is likely we will impact the whole, which might be the desire (such as sound) but there is often a downside that may or may not be acceptable. Just a thought.

Yep. I was hoping to sacrifice "acceptable" noise for increased performance. You only find out these things by trying them - some succeed, some don't.

It sounds so good that I refitted the bypass after the tests yesterday, even though the performance is not as good. It can't be too bad as it out-dragged a Porsche the other night (and I had a 90kg passenger on board).

If the lower performance means that I can't keep up on the Peaks Tour, so be it.

 

[littlefeller]

good effort though, cant beat a good bit of heath Robinson, just invest in some n2o

sometimes performance takes a hit in favor of noise reduction, air boxes being the usual culprit.
everyone old enough will remember the allspeed expansion chambers on two strokes, made your ears bleed but was so much faster @Jack Ratt

 

[Dino D]

For such a small loss in performance I’d be happy with that to have switchable noise. It’s not like you don’t have 300+bhp to play with!
Dropping these passenger off will probably be noticeable!

 

[Dino D]

That’s a lot of work by there way, now I know why I struggled to find a place to even quote for the work.

 

[Ianmc]

I remember drilling holes in my first cars exhaust box (a 1961 triumph herald convertible 1147cc) to increase the sound effect. The rather limited standard performance was made even worse, but it sounded good - or so I thought as a 17 year old!

 

[Pingu]

It's quite easy to record data, but it is very difficult to be consistent in each test.

I've really struggled to find somewhere that I can slow to 20mph and then accelerate hard to 65/70mph. I've found somewhere now and it's somewhere that is already very noisy. The only downside is that it won't be there forever.

I re-tested the standard exhaust system and the bypass exhaust system (3 runs with each system)...

There are a few observations (thinking aloud)...

a) The open bypass system is the fastest, but not by much - so bang for buck (time and effort, not money), it is not the best modification.
b) How can the system with the open bypass be the fastest, yet not have the best air mass flow rate?
c) The increase in air flow rate drops at around 4500rpm - could it be VANOS related?
d) I've always assumed that air flow rate is proportional to speed - this chart shows this is not the case.
e) I've had to delete some tests (due to spurious results), so the averages are only over two runs each. I'll do five tests for each system in future. I will be able to delete the poorest test from each dataset and still have enough data to get some meaningful results.

 

[Althulas]

Good effort and interesting read Pingu, request if you can add some vids of some runs with the difference of close and open bypass.

 

[Pingu]

Good effort and interesting read Pingu, request if you can add some vids of some runs with the difference of close and open bypass.

Prepare your eardrums if we do the tunnel on the Peaks Tour.

 

[harvey210]

Any one know of a stainless cat back for 2002 3.0L??? cheers