VR6 - exhaust silencers and cams and remap question

[matth76 0]

Hi

Please can anyone help me...I have a 1997 OBD2 golf vr6. My car currently has a high flow cat, Milltek cat back 2.25" exhaust. BMC cold air induction kit, and a more free flowing 6 branch exhaust manifold and a remap. On the last rolling road it had 192bhp and 193 lb/ft torque. I have just recently had some Eurospec 268 cams fitted. The car feels stronger but it's hard to tell how much power (if any) has been gained. I am soon to get a remap tweak to get the fuelling spot on plus rolling road session. Is it likely that the remap itself will get slightly more power from the cams (than say if I left the car as it is with just the cams and no remap)?

 

I am getting the remap done as I want the fuelling to be correct with no pinking... however I was just wondering if I would get even more power as a bonus. If so what sort of gains can I expect to achieve (with just the cams on their own, and then after the remap)?

 

Ok, second question... is it a good or bad thing to remove the middle exhaust silencer? Would this drastically reduce backpressure and make it undrivable, or would more power / torque be gained (with a remap tweak too)? I'm definitely keeping the back box/silencer, but wondered about the remaining middle silencer and whether it is benefitial to remove this or not? As already mentioned I have a high flow cat too already. I'm not sure if there are one or two middle silencers plus the backbox on a Milltek system.

 

Thanks for any help or information.

Cheers

Matt

[matth76 0]

Does anyone know? Has anyone removed any of their silencers?

[dr_mat 0]

AFAIK removing the centre silencer just makes the exhaust louder. On a N/A car it's very unlikely to liberate any bhp.

Don't know too much about the pros and cons of remapping for your cams though.

[VRTrickster 0]

Id say that the fuelling would probably need to be adjusted to the extra air coming in. Not sure of how much difference in power it would make though. Id get it done if you have the money! Can I ask where you got your remap done, and how much does it cost for a tweak after say fitting an extra mod?

[matth76 0]

Hi there... thanks for your replies. Stealth are doing all the remapping work. I'll ask them about the removal of the silencer just before the backbox and whether its a bad or good thing ... people on the vwvortex forum have said it should liberate quite a bit of power although it will be fairly noisy.. However I'll see what vince reckons.

 

Cheers

[corradovr6sc 0]

My mate had a straight through exhaust system (with the suitcase silencer removed) on his Jetta vr6 and it was pretty loud. Made a nice burble at the rear silencer though :) Can't tell whether it increased hp and if it did it was only minimal so I'd leave it alone.

[Chris VR6nos 0]

The answer to the cam question is easy!

The reason for a cam change is generally to gain power/performance.

Burning fuel gives you power if you can get the correct amount of air to the point where the fuel is going to be ignited.

The cams will simply let more air into the engine so the fueling needs the essential adjustment of a re=map to make changing the cams worth while else it's a waste of time and money.

 

Let exhaust exit more easily, If air resistance or back-pressure makes it hard for exhaust to exit a cylinder, it robs the engine of power. If the exhaust pipe is too small or the silencer has a lot of air resistance then this can cause back-pressure. High-performance exhaust systems use gasflowed manifolds, big tail pipes and free-flowing silencers to eliminate back-pressure in the exhaust system. So i hear you ask yourself, is maintaning back-pressure a myth or what!

A drag racer with 3500bhp uses pipes 22inches long that exit the cylinder head and look at the sky, where's the back-pressure there? Cut the box out.

Another thing is make everything lighter, Lightweight parts help the engine perform better. Each time a piston changes direction it uses up energy to stop the travel in one direction and start it in another. The lighter the piston, the less energy it takes. Lighter parts also allow the engine to rev faster, giving it more horsepower.

 

 

Chris

[CoxyLaad 0]

3500bhp dragsters dont have to pootle through traffic at just above idle speeds.....although it would be excellent to watch!

back pressure is certainly needed on a road car, how much is debateable. All you are going to do shift your torque curve up the rev range.

 

What you really need is someting akin to an exup valve which yamaha have been using for years. This is just a valve that provides a restriction in the exhaust flow enabling the ecu to modify the back pressure at various engine speeds. Take about having your cake and eating it....wtf does that phrase mean?!

[dr_mat 0]

BMW use similar tech in their exhausts. Twin pipes above 3k rpm, single pipe only at lower revs.

[Kevin Bacon 5]

The engine will self adjust to the cams on part throttle. All the remap will do is knock back the ignition advance a bit and add a little fuel on the full throttle tables. You'll be lucky to get an extra 10hp tbh.