Does opening the exhaust flaps reduce economy and power at lower rpm?
- Thread starter rajeevx5
- Start date
Since opening mine. About 140 miles ago, I've found.
More noise on over run between idle and 2400rpm
Very slightly more noise on pick up between same rev range.
More responsive and a smoother pick up throughout the rev range, more noticeable at above rev range.
Drone at 80 to 85mph
I did a 50 mile trip on the dual carriageway and drove as I normally would and if anything about 3mpg on the screen more.
More noise on over run between idle and 2400rpm
Very slightly more noise on pick up between same rev range.
More responsive and a smoother pick up throughout the rev range, more noticeable at above rev range.
Drone at 80 to 85mph
I did a 50 mile trip on the dual carriageway and drove as I normally would and if anything about 3mpg on the screen more.
Re: Effect on Power
It's a possibility, but without empirically measuring power with and without flaps mod, you won't know for sure.
One of the most important factors is the overall gas flow velocity throughput - much like boy racers that put on 4" exhaust pipes in the belief that this will improve the breathing of their car - quite the opposite, because of the larger diameter, in most cases, they will have reduced the overall gas flow velocity, and set up all sorts of problems with engine breathing and performance (urban myth = exhaust backpressure (4 stroke) is good).
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i have taken a route today, that i have done a lot and oddly enough, around town i was an almighty 6mpg higher!
never have i seen over 22 mpg in town, today i was averaging over 28!
on the duel carriage way, I've never seen over 28, today, on a run that i take almost every day, i got 30.2!
now I'm not saying it has anything to do with the valves being disconnected, BUT that is the only thing i have done to the vehicle and I'm certainly not driving it any difference.
then again, we all know that there are a lot of other factors to take into consideration, weather wise etc.
i am in no way saying that disconnecting the valves has increased my MPG, this is just my findings over the last 200 miles i have done with the valves disconnected and i know my driving style is still the same ruthless style.
never have i seen over 22 mpg in town, today i was averaging over 28!
on the duel carriage way, I've never seen over 28, today, on a run that i take almost every day, i got 30.2!
now I'm not saying it has anything to do with the valves being disconnected, BUT that is the only thing i have done to the vehicle and I'm certainly not driving it any difference.
then again, we all know that there are a lot of other factors to take into consideration, weather wise etc.
i am in no way saying that disconnecting the valves has increased my MPG, this is just my findings over the last 200 miles i have done with the valves disconnected and i know my driving style is still the same ruthless style.
^ Sorry, should have made clear I was replying more about the power part of the question, rather than the mpg
i wouldn't say its given me more power.
just more responsive, the only reason i say this is because i didn't tell the mrs what i did and we went out to which half way through our journey she said "it seems more responsive lower down, what have you done?"
now if a passenger picks it up, you need to take it on bored.
i personally, agree, i find it has made it VERY slightly more responsive, BUT nothing to write home about. on a torque curve, i highly doubt there would be a noticeable difference.
bit like a decat - people will state that its made a very noticeable difference, but thats subjective and very personal.
VCDS saves you grovelling under the car otherwise you disconnect the electrical connector to the solenoid that operates the valve.
either via VCDS or by disconnecting the valves.
EDIT : Rob beat me to it ^^^
i have disconnected the valves, BUT i don't have VCDS to hand. when i do i will plug them back in and then do it that way.
Normally, when boy racers fit big bore exhausts, it results in less power, not more (wrong gas flow velocity)
I would say that your Mrs. was probably reacting to the change in sounds, rather than actually detecting more response/power!
Normally, when boy racers fit big bore exhausts, it results in less power, not more (wrong gas flow velocity)
so where do you stand on decat pipes?...
opening the valves is different to fitting a cherry bomb to a 12XE...
Normally - subjective and personal. potato potata.
Interesting discussion.
I have a fuel tracker S/S that I've always done not out of monetary interests but to see the effect of mods. For example mpg went down 0.5mpg after the remap and another 0.5mpg after I'd hit 10k miles so fully loosened up I guess but then it dropped 1.5mpg after adding the cold air intake and turbo inlet pipe. I'll disconnect my valves and run it like that for 2 tanks and see what happens.
I have a fuel tracker S/S that I've always done not out of monetary interests but to see the effect of mods. For example mpg went down 0.5mpg after the remap and another 0.5mpg after I'd hit 10k miles so fully loosened up I guess but then it dropped 1.5mpg after adding the cold air intake and turbo inlet pipe. I'll disconnect my valves and run it like that for 2 tanks and see what happens.
now lets argue that your mpg went down after the map and CAI because you like the noise / extra power, so you are heavier on the right foot?
i am just shy of 10k, maybe now its loosened up nicely, this has had the positive effect on my MPG?
i have a thousand mile road trip coming up this year, maybe even a few hundred more. i will have my valves back on before there, to reduce the drone. but i will be interesting to see how my MPG is.
by then i should also have my DTUK fitted - i was going to order it today actually but I'm still debating it an managing to talk myself out of it. fml.
Like I said earlier, you need to empirically measure to be sure of the results.
If the decat pipe diameter matches the gas flow velocity of the cylinders, then all good and well. But more noise does not necessarily equate to more power in many cases.
It has also warmed up considerably since the weekend.
The A3/S3 fuel consumption is considerably affected by ambient temperature, as numerous previous threads have shown.
LOL quite possibly mate certainly after having the map put on but my driving habits after fitting the CAI have changed less so.
Good timing for the box I think DTUK have just launched a new 3 channel system ?
The JB1 box is alleged to look at more than just boost (also tweaks fueling) - but I've not seen any hard evidence of this yet.
i shall have a google! But, i cant be doing with anymore curve balls being thrown in, its taken me ages to decide to get a DTUK box! and then i still go onto the site and then click off it, because I'm not 110% certain! and i cancelled my APR stg1 a few weeks ago!
There is an 8V Facebook group and they are raving about the JB1 box on there. Not sure if any European distributor though so you're probably best sticking with DTUK or MTM if you're feeling flush.
I think AP Automotive are doing the UK distribution for the JB1.
http://www.apautomotive.com/blog/2016/03/burger-motorsport-at-ap-automotive
I'm probably selling my DTUK box in the very near future, if anyone wants one (with the latest v3 software on it)
http://www.apautomotive.com/blog/2016/03/burger-motorsport-at-ap-automotive
I'm probably selling my DTUK box in the very near future, if anyone wants one (with the latest v3 software on it)
I think AP Automotive are doing the UK distribution for the JB1.
http://www.apautomotive.com/blog/2016/03/burger-motorsport-at-ap-automotive
I'm probably selling my DTUK box in the very near future, if anyone wants one (with the latest v3 software on it)
if you sell, soon, drop me a PM.
i keep going on the DTUK site to buy one, and then i click off and chicken out lol. maybe a bargain, would be more easy to persuade myself.
What mpgs on average are you guys seeing on the motorway ? I'm seeing around 29-30mpg at around 75-80 although my cars only covered a 1000 miles. I read an article a few days ago about the cjxc engine and how it's engineered to have some back pressure to allow the turbo to spool quicker so surely the exhaust flaps may have some effect ? I do like the better sound but I'm considering closing them as I have just secured a job at rolls-Royce so will have to commute 60 odd miles a day
there is plenty of back pressure in the downpipe, have you seen the shape of it and how close the CAT is to the turbo?
the valves is not going to cause any issues that i can see, taking the downpipe into consideration, IMO.
as for the milage, well, yours will get better in time, don't worry about that. Engines in general perform better when the miles have been added, 1k miles is still VERY early days.
Although, i get around 25-28 on a good run, but I'm not the slowest of drivers.
as for closing your valves, i assume you haven't disconnected them or opened them on VCDS?
if you place it in comfort, they will stay closed. in Dynamic, its based on RPM and throttle %. under 4k it'll be closed.
For turbo cars,
Upstream of the turbine, you want as much gas velocity as you can get.
Exhaust gas velocity is the primary factor in getting the turbo spooled quickly (not backpressure).
Downstream of the turbine, you want as little back pressure as possible.
Upstream of the turbine, you want as much gas velocity as you can get.
Exhaust gas velocity is the primary factor in getting the turbo spooled quickly (not backpressure).
Downstream of the turbine, you want as little back pressure as possible.
I've opened them using VCDS as soon as I collected the car haha, so I don't even know how the car is with them closed. I'll try it out on a few runs and I'll see if there's a difference.
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Does doing this log faults in the ecu??(worried about warranty etc)
