GP
Guest
|
|
« on: June 13, 2010, 11:47:18 pm » |
|
I was lucky enough to recently acquire a complete Vortex Exhaust system for a 2.2 Murena which I plan on fitting soon. I intend to carry out before and after power runs on my local rolling road, to see how effective it is and to see if it actually does what it says on the packet? Which is to increase exhaust gas velocity, create a vacuum to scavenge the exhaust gases out faster and thus increase bhp and torque by up to 15%. Plus better fuel economy etc.... I thought this might be of general interest to you all and wondered if anyone actually has some experience of these systems. (Other than my best mate who sold it to me. ) For further sounds too good to be true information see:- http://www.vortexexhausts.thermashieldenergy.com.au/index.htmlhttp://www.vortex-performance-exhausts.co.uk/I do very much hope it is all true and will keep you posted. Cheers, GP
|
|
« Last Edit: June 14, 2010, 08:34:11 am by GP »
|
Logged
|
|
|
|
|
|
michaltalbot
YaBB God
Posts: 566
|
|
« Reply #3 on: June 14, 2010, 11:09:42 am » |
|
Yes, engine needs the back pressure from exhaust and if it isn't there, it doesn't work properly, because part of unburned fuel leaves the cylinder too early. That's why cars with damaged exhaust lose the power... and it's also the reason why 2 engines of my Murena went broken (before I bought it), because somebody put there an 4-1 exhaust and leaved the original carburetors, so the result was that the engined was running on very poor mixture which means higher working temperature and damaging of the engine is "comming soon" So using the 4-1 pipe, or exhaust system like this could be fine, but it's necessary to rich up the inlet side too - bigger carburetors, fuel injection, etc. PS: this seems to be "home made" piece, so first questions are - why the seller have sold it, how it is prooven and which systeme of "feeding" it had.
|
|
« Last Edit: June 14, 2010, 11:12:42 am by michaltalbot »
|
Logged
|
|
|
|
GP
Guest
|
|
« Reply #4 on: June 15, 2010, 07:33:54 am » |
|
Yes, engine needs the back pressure from exhaust and if it isn't there, it doesn't work properly, because part of unburned fuel leaves the cylinder too early. That's why cars with damaged exhaust lose the power... and it's also the reason why 2 engines of my Murena went broken (before I bought it), because somebody put there an 4-1 exhaust and leaved the original carburetors, so the result was that the engined was running on very poor mixture which means higher working temperature and damaging of the engine is "comming soon" So using the 4-1 pipe, or exhaust system like this could be fine, but it's necessary to rich up the inlet side too - bigger carburetors, fuel injection, etc. PS: this seems to be "home made" piece, so first questions are - why the seller have sold it, how it is prooven and which systeme of "feeding" it had. It was sold as part of a package of complete engine, gearbox and gear linkage, as the owner had replaced the complete package with a different engine and gearbox. I don't know how it was proven, other than it was being driven around the U.K. and trips to Europe on a regular basis, with no problems as far as I am aware. It was running on 2 x 40mm Solex sidedraught carburettors. I will be very cautious and have to admit to all the concerns mentioned above. But I will go about this is a planned manner and hopefully come to a definitive conclusion to this “Vortex” technology. GP
|
|
|
Logged
|
|
|
|
Anders Dinsen
Administrator
YaBB God
Posts: 3188
WWW
|
|
« Reply #5 on: June 18, 2010, 12:08:02 pm » |
|
Yes, engine needs the back pressure from exhaust and if it isn't there, it doesn't work properly, because part of unburned fuel leaves the cylinder too early. That's why cars with damaged exhaust lose the power... I have to correct your terminology there Michal - there's no 'back pressure' needed to 'hold in' the fuel on a four stroke engine: The valves are shut during the combustion phase, and during most of the intake phase too. You are correct, however, that the exhaust design can change the way the engine performs, and may also require rejetting of the carburettor, but this is more complex than just 'back pressure' and involves parameters like cam overlap, lift, carburettor type, and the actual construction of the manifold: Is it a 4-1 or a 4-2-1 exhaust. The length of the runners is also important as it is used to tune the exhaust to maximise torque at specific RPM, becasue at resonance frequencies, the exhaust gasses passes more easily through the manifold runners. /Anders
|
|
|
Logged
|
1982 Talbot Matra Murena 2.2 prep 142 2017 BMW i3 "Charged Professional" 94Ah
Used to own: 2001 Renault Matra Grand Espace "The Race" V6 24v 1997 Renault Matra Espace 2.0 8V 1987 Renault Matra Espace J11 2.2
|
|
|
|
|
Anders Dinsen
Administrator
YaBB God
Posts: 3188
WWW
|
|
« Reply #8 on: June 18, 2010, 09:48:32 pm » |
|
I think that there is a smal phase, when inlet valve is opening at the same moment when exhaust one is closing for rinse out the rest of the burnt gas... isn't it?
Indeed, that's the overlap. The S cam has about 50 degrees overlap, but on the Holbay cam as much as 76 degrees. The standard cam only 32 degrees. At low rpm, the overlap can allow a bit of unburned fuel/air mixture to pass directly into the exhaust, but as rpm increases, the overlap ensures that the low pressure, which exist in the combustion chamber during the last phase of the exhaust stroke can aid in accelerating the fuel/air misture even before the piston starts its pumping effect. This is because the "bubble" of exhaust gasses has been accelerated and is still moving inside the exhaust as the piston slows down its upward going movement: The inertia of the bubble now starts working like a pump and by keeping both inlet and exhaust valves open at the same time (overlapping), the pump works on the inlet. On a 2-valve engine, this is very useful because you need high airspeeds around the valves, so they generally like overlap. 4-valve engines don't benefit as much from it since breathing is a lot less restricted than on the 2-valve engine.
|
|
|
Logged
|
1982 Talbot Matra Murena 2.2 prep 142 2017 BMW i3 "Charged Professional" 94Ah
Used to own: 2001 Renault Matra Grand Espace "The Race" V6 24v 1997 Renault Matra Espace 2.0 8V 1987 Renault Matra Espace J11 2.2
|
|
|
|
Anders Dinsen
Administrator
YaBB God
Posts: 3188
WWW
|
|
« Reply #10 on: June 19, 2010, 06:39:23 am » |
|
That's very interesting Anders, I didn't knew all these details... Why the Hollbay cam has it so long? To clean the chamber better?
Well first of all the Holbay is a 296 degree cam whereas the S cam is only 279. Longer inlet/exhaust periods necessitates more overlap "to fit". In this way it's actually more like the Sodemo Gr.4 cam, which I think is similar to the 160 hp cam that Politecnic offers. However, the lift of the Holbay is only 7.06 mm whereas the S cam lifts 7.4 mm. This may seem a small difference, but it does mean a big difference in inlet cross sectional area. The Sodemo cam lifts as much as 7.75 mm. The standard cam 6.5 Because the Holbay is relatively low lift cam (but still more than the standard cam), the inlet pulses on the carburettors have less amplitude, but the overlap and long periods ensure that the pulses are a lot longer. This is probably the reason it works so well on the standard carburettor which it's long narrow intake runners - you don't even need to re-jet it. Roy has told me the Holbay guys had a lot of experience with this engine (in the smaller 1.6 and 2.0 trims), so they probably knew exactly what they were doing, but why they ended on these numbers, I don't know. It's a pity the company has closed their cam profiling section. /Anders
|
|
|
Logged
|
1982 Talbot Matra Murena 2.2 prep 142 2017 BMW i3 "Charged Professional" 94Ah
Used to own: 2001 Renault Matra Grand Espace "The Race" V6 24v 1997 Renault Matra Espace 2.0 8V 1987 Renault Matra Espace J11 2.2
|
|
|
roy4matra
YaBB God
Posts: 1201
|
|
« Reply #11 on: July 13, 2010, 12:45:11 pm » |
|
I was lucky enough to recently acquire a complete Vortex Exhaust system for a 2.2 Murena which I plan on fitting soon. I intend to carry out before and after power runs on my local rolling road, to see how effective it is and to see if it actually does what it says on the packet? Which is to increase exhaust gas velocity, create a vacuum to scavenge the exhaust gases out faster and thus increase bhp and torque by up to 15%. Plus better fuel economy etc.... 15%! More like 1.5% I suspect, unless the exhaust was particularly restrictive in the first place. :-) There is far more to exhausts than realised by many. You get a pulse wave that travels down the exhaust and when it gets to the end (of the tailpipe) reverses back to the valves. If it reaches the valves on the negative pulse of the wave it will aid extraction and improve the power. If however, it arrives on the positive pulse it will obstruct the gases exit and power. So lengths are critical. (Formula 1 teams at one time used to start with a certain length and then cut them back until they got the best figures, such was the crude way then! It will all be done on computers these days) A secondary thing do to with this pulse wave, is that on long exhaust systems, you want to position the exhaust hanging points where the wave crosses from positive to negative or vice versa (in other words where there is least vibration) and the exhaust rubber mounting will last well. If you hang it where the wave is at a peak, the mounting will break far more often. With our short exhausts and the way they are mounted I doubt this mounting feature will be a factor, but it shows just why you cannot just choose any lengths or mounting points at random and expect to get the best. To answer another point, on a naturally aspirated engine, more overlap can help improve combustion chamber filling and therefore more power, but as the overlap increases, the emissions will get worse as some air/fuel goes straight out from inlet to exhaust. This is why you now have variable valve timing on modern engines. No overlap at idle to keep emissions low, and more overlap as revs rise to give you the power you need (no overlap at higher revs and throttle would seriously restrict power). Roy
|
|
« Last Edit: August 03, 2010, 10:47:56 pm by roy4matra »
|
Logged
|
|
|
|
|
|
Bart_Maztra
Sr. Member
Posts: 211
|
|
« Reply #14 on: July 14, 2010, 08:13:49 pm » |
|
There is far more to exhausts than realised by many. You get a pulse wave that travels down the exhaust and when it gets to the end (of the tailpipe) reverses back to the valves. If it reaches the valves on the negative pulse of the wave it will aid extraction and improve the power.
I am sure an exhaust system can be designed to get the wave back at the valve, at the moment the next wave is coming. But only at one specific RPM?? You can compare it with resonance. If the resonance frequency of an object is 20 hertz, you can get the object vibrating big time when applying a small amount of energy of 20 hz. When applying any other amount of hertz, the object will not get into resonance. When not in resonance, the object is easyer to vibrate when the object is as light as possible. Apply this to exhaust. An exhaust tuned to resonate at 6000 RPM, will give a big advantage at 6000RPM, but at any other RPM it will not do anything. For any other RPM it helps to have as less restriction as possible. As we are not allways running our engine's at one speficik RPM, it is better to forget about tuning the exhaust system, and focus on restriction. DISCLAIMER, I am NOT an exhaust expert. This is my personal opinion. It is likely to be wrong.
|
|
|
Logged
|
|
|
|