Exhaust valve

Is there an exhaust valve on the LP640 that stays closed untill 3500-4000 rpm to keep the exhaust sound lower. I have that system on my DB9 and bypassed it by disconecting the vacuum lines it locks open the valve for better sound at lower rpm. If there is one what has been the experience with the bypass.

Wouldn't mind doing that with mine either - I did the same with my 997, disconnected the vacuum and now the exhaust sounds great all the time

Wouldn't mind doing that with mine either - I did the same with my 997, disconnected the vacuum and now the exhaust sounds great all the time

Yes but does the LP640 have a valve system. With all the talk on the forum about exhaust I haven't read anything about one.

Is there an exhaust valve on the LP640 that stays closed untill 3500-4000 rpm to keep the exhaust sound lower. I have that system on my DB9 and bypassed it by disconecting the vacuum lines it locks open the valve for better sound at lower rpm. If there is one what has been the experience with the bypass.

yes! lp640 has a valve stay closed at low end.

 

thanks

alex

yes! lp640 has a valve stay closed at low end.

 

thanks

alex

 

hi alex,

 

can this be disabled?

hi alex,

 

can this be disabled?

yes! very easy and so, but do not do it, as lp640 gos, already missing the tq at low end from the murcis,keep that valve close will help that little tq you can have at the low end,as fas as when you have the car WOT,IT OPENS up,i will post some dyno info next week.

 

thanks

alex

yes! very easy and so, but do not do it, as lp640 gos, already missing the tq at low end from the murcis,keep that valve close will help that little tq you can have at the low end,as fas as when you have the car WOT,IT OPENS up,i will post some dyno info next week.

 

thanks

alex

 

Ahh, thats very interesting. Thanks for the feedback alex!

 

Ahh, thats very interesting. Thanks for the feedback alex!

 

Hi Guys,

have to beg to differ here - my LP640 has had the valves wired open for the last 3000 miles and had no problems. It sounds much much better than before. The dealers also had it on the laptop and it didnt pick it up on there.

 

Simon

 

Hi Guys,

have to beg to differ here - my LP640 has had the valves wired open for the last 3000 miles and had no problems. It sounds much much better than before. The dealers also had it on the laptop and it didnt pick it up on there.

 

Simon

An easy way to keep them open is pull off the vacuum line from the valve and put a plug in the line to seal it, the pump will still run and the system will not know the difference. The engine idles at about 1000 rpm and the valve opens at 3500-4000 rpm during that 2500-3000 it could have a very small loss of torque maybe a few ftlbs but it could pick up a few HP at the same time in that narrow rpm range. I think the difference will be so small one way or the other if you like the strong sound off of idle it is worth a try. The process should take about 5 minutes. Most car company's that use the valve system do it to pass the drive by noise requirement.

An easy way to keep them open is pull off the vacuum line from the valve and put a plug the line to seal it, the pump will still run and the system will not know the difference. The engine idles at about 1000 rpm and the valve opens at 3500-4000 rpm during that 2500-3000 it could have a very small loss of torque maybe a few ftlbs but it could pick up a few HP at the same time in that narrow rpm range. I think the difference will be so small one way or the other if you like the strong sound off of idle it is worth a try. The process should take about 5 minutes. Most car company's that use the valve system do it to pass the drive by noise requirement.

 

OK I went down to the garage, all you have to do is slip under the back of the car, the vacuum line is on a tee from both valves right at the back of the car. Just take a plier move back the small hose clamp pull off the rubber line and plug it, you can use a machine screw, put back the hose clamp. You can put a rubber end cap over the other end just to keep the dirt out. It is much louder from idle to 3500-4000 Rpm then it is the same because the valves would be open anyway. To me it sounds more high pitched less of a deep sound. If you like it loud it is free noise. Exhaust sound is a subjective thing if you don't like it it can put it back anytime in 5 minutes.

anymore info on this...pics?

It works better on the LP than on the Gallardo. Gallardo throws a CEL most of the time with that done. The LP did not seem to do it as much. I cannot comment on the TQ numbers, Alex is the expert at that. I would not doubt what he said as he has likely put the thing on a dyno and tested it both ways. The Chinaman knows! It is easy to disconnect though, does not take to long from what I understand.

yes! very easy and so, but do not do it, as lp640 gos, already missing the tq at low end from the murcis,keep that valve close will help that little tq you can have at the low end,as fas as when you have the car WOT,IT OPENS up,i will post some dyno info next week.

 

thanks

alex

 

 

This is probly the only way to see the differance in proformace from dissconnecting the bypass valves so they are open at all times. It will be interesting to see how much TQ is lost from doing this mod for sound.

 

Think about guys, if you take away back pressure from a non charged car you will loose some TQ. How much is the question. Will you be able to noticed, well if the car is tuned and balaced correctly and is set up correctly you may feel the differance. The TQ curve is deffently going to change and how it changes will show on the dyno graph. This is when you can say it is for the better or forthe worse. Also diving style will be a factory.

 

To do this mod there is a vaccum line that goes to a hard line around the center of the frame at the back of the car at the bottom. disconnect and pluf the hard line as well as the vaccum line and your done.

This is probly the only way to see the differance in proformace from dissconnecting the bypass valves so they are open at all times. It will be interesting to see how much TQ is lost from doing this mod for sound.

 

Think about guys, if you take away back pressure from a non charged car you will loose some TQ. How much is the question. Will you be able to noticed, well if the car is tuned and balaced correctly and is set up correctly you may feel the differance. The TQ curve is deffently going to change and how it changes will show on the dyno graph. This is when you can say it is for the better or forthe worse. Also diving style will be a factory.

 

To do this mod there is a vaccum line that goes to a hard line around the center of the frame at the back of the car at the bottom. disconnect and pluf the hard line as well as the vaccum line and your done.

 

 

Does the Murcie have this valve?

Does the Murcie have this valve?

 

 

Murci has these two valves as well.

does anyone have a picture exactly where they are located

does anyone have a picture exactly where they are located

 

You really don't need a photo. It is dead nuts in the middle of the car. On the LP640 it has a bit of heat shielding around the lead line to the motor. Might help identify it. both valves feed from a common T. If you can't find the t, just find the valves and move inward from there.

 

Good luck!

 

 

Murci has these two valves as well.

No a Murci dose not have the valve only the LP 640s have the valves and Gallardos.

No a Murci dose not have the valve only the LP 640s have the valves and Gallardos.

 

 

Yes you are right Jeff. I forgot that this was add to just the LP.

I did this mod on my LP ages ago and it works perfectly. The car has a much more musical note at low speeds. No difference in power and no problems at all.