Loss of bhp with a straight through exhaust??
Discussion
I thought i would throw this out to a slightly wider field other than the Corvette forum.....
I managed to get a short ride in a manual Corvette C6 yesterday that had the back boxes removed.Essentially a straight through system.It Sounded awesome. I didn't manage to go any sort of long drive. So was unable to see or hear the effects of droning. What i would want to know is. If i did the same. What would i loose in terms of bhp?
I managed to get a short ride in a manual Corvette C6 yesterday that had the back boxes removed.Essentially a straight through system.It Sounded awesome. I didn't manage to go any sort of long drive. So was unable to see or hear the effects of droning. What i would want to know is. If i did the same. What would i loose in terms of bhp?
slightly cheaper fodder but i've read frequntly that de-catting the e36 m3 evo actually harms power delivery. even more cheaply, i removed the centre boxes from my 24v capri a few years ago, leaving the whole system with just 2 straight through boxes at the back. it lost power and was DEAFENING.
BLUETHUNDER said:
I forgot to mention i will be leaving the cats in place.The only silencing on the Corvette C6 is the rear boxes.There is no mid box.I have smaller rear boxes on there at the moment.A lot smaller than the factory offerings.But they dont release muck of a rumble.
In my experience, & just in case you're thinking, Flowmasters don't flow. I had an exhaust system built for my Camaro some years ago fitted with only the two rear silencers, it ran very well & didn't choke up at all but the sound of the car was very conservative & without the rumble I was looking for. I can't remember the make of the original silencers but I still have them at the workshop somewhere & will have a look if I find them.
I removed them & installed Flowmasters which gave me a terrific noise & the rumble I was looking for, but unfortunately there was a choking or bogging at higher revs because the exhaust gasses simply weren't exiting through the Flowmasters as well as they had done through the original ones I had removed
This may have been partly due to the fact I didn't have a cross or x pipe at the time which they do recommend, but even so it was obvious that they didn't flow as well as the original silences.
The flowmasters remained on the car up until it was put back in the workshop because I never went anywhere in a hurry & the sound was excellent. When the current work is finished, bigger engine & new rear end, I'm not sure what I'm going to use but I wont go back to Flowmasters.
I removed them & installed Flowmasters which gave me a terrific noise & the rumble I was looking for, but unfortunately there was a choking or bogging at higher revs because the exhaust gasses simply weren't exiting through the Flowmasters as well as they had done through the original ones I had removed
This may have been partly due to the fact I didn't have a cross or x pipe at the time which they do recommend, but even so it was obvious that they didn't flow as well as the original silences.
The flowmasters remained on the car up until it was put back in the workshop because I never went anywhere in a hurry & the sound was excellent. When the current work is finished, bigger engine & new rear end, I'm not sure what I'm going to use but I wont go back to Flowmasters.
Edited by Man from UNCLE on Monday 25th April 15:54
If you have the original system but with centre box removed I'm guessing that you still have some sort of cross over pipe installed. These actually do help clear the headers/exhaust manifolds, so I think you may as well try & find out because removing the rear boxes you already have has got to be cheaper than buying a a pair of Flowmasters or decent replacements only to find they do bog it down.
But I will say that I am certainly no expert & would hate to give you the wrong advice, I can only go by my limited knowledge & my own experiences.
But I will say that I am certainly no expert & would hate to give you the wrong advice, I can only go by my limited knowledge & my own experiences.
BLUETHUNDER said:
I wonder if i would get the same kind of choking or bogging at higher revs wiv no back boxes fitted at all?
Absolutely not.Anything that helps the engine breathe is 99% of the time a good thing. But obviously you need to re-tune to make the most of that extra airflow.
In basic terms the orginal exhaust will have been matched and tuned to your engine map / set up as it came from the factory, as with all modifications some work and some don't no matter what the marketing blurbs states, depending on how the car is set up removing the rear boxes could effect both BHP and torque.
For instance on my car which is not similar to yours but this is just for illustration. I removed both the CAT and increased the downpipe diameter on a turbo engine and gained both torque and HP over the standard unit, but I could have had more torque over a wider spread of the rev range if I had used a smaller diamter downtube, strange but true.
My own thoughts would be that you would not lose power in terms of total output but you may find that your engine does not pull cleanly from low revs for instance and could be jerky on small throttle openings and the top end could seem to run of of puff due to a lack of back pressure.
You can find some resources on the web about exhausts and pressure and how they work on a multitude of engines to see what could be the out come.
HTH if only to give and opinion based on my experiences
For instance on my car which is not similar to yours but this is just for illustration. I removed both the CAT and increased the downpipe diameter on a turbo engine and gained both torque and HP over the standard unit, but I could have had more torque over a wider spread of the rev range if I had used a smaller diamter downtube, strange but true.
My own thoughts would be that you would not lose power in terms of total output but you may find that your engine does not pull cleanly from low revs for instance and could be jerky on small throttle openings and the top end could seem to run of of puff due to a lack of back pressure.
You can find some resources on the web about exhausts and pressure and how they work on a multitude of engines to see what could be the out come.
HTH if only to give and opinion based on my experiences
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