Muffler Gate removal
Discussion
My S4s is outfitted with a gate valve on the muffler so that it warms up the engine quicker to meet the emission specs. I hear people have disabled it so it doesn't spend three minutes at high rpm. A friend also told me that it's not healthy for the engine to choke it with this thing. I would like to disable it. Should I do it? I noticed it's vacuum activated, so it would be easy to disable. Any thoughts or advise on this? Thanks.
I think there is a set screw that can hold it one if it is not rusted in place. Also I think SJ and Moto-Concept sells an adapter piece with the flap removed. If you wire it open or remove the EBPV the vac line will still need to be connected or blocked off to prevent a vac leak that will effect of ther functions.
Calvin 90 SE
Calvin 90 SE
Manuelin,
The proper name for the "gate valve" you're talking about is the Exhaust Back Pressure Valve or EBPV. Disabling it by wiring it open is only part of the equation. If you only do this, the engine will actually rev even higher at startup. This will, in some cases, also cause the Check Engine light to come on with a Code 35 (Idle Speed Error).
As you state, the EBPV is there for emissions purposes. It helps bring the catalytic converter to operating temperature quicker. However, by blocking the exhaust it also makes the engine want to stall (the old "banana in the tailpipe trick"). In order to keep the engine from stalling, there is another device near the top of the engine known as the throttle jacking capsule (TJC). It works in unison with the EBPV and is actually the one responsible for the higher idle.
So, if you disable just the EBPV, the startup RPMs will be higher because the TJC is working against an unrestricted exhaust. If you disable only the TJC, the engine will stall because there aren't enough RPMs to fight against the restricted exhaust.
To properly do the mod, you must disable both the components in the system. To do this, you need to disconnect the vacuum lines to both the TJC and EBPV capsules and cap theme so there are no vacuum leaks. Then you will also need to wire the EBPV open, remove its butterfly valve, or replace it with a spacer from Moto-Concept.
Cheers,
Karl-Franz :-)
www.espritfactfile.com
The proper name for the "gate valve" you're talking about is the Exhaust Back Pressure Valve or EBPV. Disabling it by wiring it open is only part of the equation. If you only do this, the engine will actually rev even higher at startup. This will, in some cases, also cause the Check Engine light to come on with a Code 35 (Idle Speed Error).
As you state, the EBPV is there for emissions purposes. It helps bring the catalytic converter to operating temperature quicker. However, by blocking the exhaust it also makes the engine want to stall (the old "banana in the tailpipe trick"). In order to keep the engine from stalling, there is another device near the top of the engine known as the throttle jacking capsule (TJC). It works in unison with the EBPV and is actually the one responsible for the higher idle.
So, if you disable just the EBPV, the startup RPMs will be higher because the TJC is working against an unrestricted exhaust. If you disable only the TJC, the engine will stall because there aren't enough RPMs to fight against the restricted exhaust.
To properly do the mod, you must disable both the components in the system. To do this, you need to disconnect the vacuum lines to both the TJC and EBPV capsules and cap theme so there are no vacuum leaks. Then you will also need to wire the EBPV open, remove its butterfly valve, or replace it with a spacer from Moto-Concept.
Cheers,
Karl-Franz :-)
www.espritfactfile.com
Hi Manuelin,
Will you be going to the San Luis Obispo meeting for the LA a Bay Area Esprit meeting? I will be there to give you some of my insights on the car and your throttle issue. This is a very simple thing to do if we have the plugs for the hoses. Screws don't always plug to well but not to worry since the vac supply is from a pump and not the engine. You get leaks anyhow since the valves for the heater switches leak also. He heh hee.
One way to look at it is the hose diagram on the boot lid. It shows the hose routing and all. Just plug the hoses that go to the Ebpv and throttle jack. If you can't do this then I can help you and discuss it as we take a leak in the giant clamp urinal in the Madonna Inn. He heh. Well, this should be interesting to learn more about our cars, alot I have learned on the EFF and alot from my own experiences having owned so many exotics and brute hp domestics in the past.
I just hope during the meet that we do learn more and not have to deal with threads such as those in the 1/4 mile issue. None of these guys have ever driven a car that will do 10 sec or even 8 seconds. I have and I can tell you that there is more than step on the gas. I can be sure that if an Indy driver sat in a dragster and a dragster driver in a indy car, they will respect each others craft and not pass criticism. In both sports, people die from trying to be the best they can be and no one and I mean no one should put the other down.
Just a thought, when you go down the lane in a 7.8 sec 1200hp car, your eyeballs shake and you heart loses its beat. You have not time to really look at the red line, you have to shift by feel and if you get everything all right, you get your data aqusitions back and they tell you that there was slippage in the the drivetrain which means you did not launch properly. etc. etc. I love this sport, I love indy, formula 2000, rally, and everything in between.
Til then, I'll see you then.
Dindo
95 s4
Will you be going to the San Luis Obispo meeting for the LA a Bay Area Esprit meeting? I will be there to give you some of my insights on the car and your throttle issue. This is a very simple thing to do if we have the plugs for the hoses. Screws don't always plug to well but not to worry since the vac supply is from a pump and not the engine. You get leaks anyhow since the valves for the heater switches leak also. He heh hee.
One way to look at it is the hose diagram on the boot lid. It shows the hose routing and all. Just plug the hoses that go to the Ebpv and throttle jack. If you can't do this then I can help you and discuss it as we take a leak in the giant clamp urinal in the Madonna Inn. He heh. Well, this should be interesting to learn more about our cars, alot I have learned on the EFF and alot from my own experiences having owned so many exotics and brute hp domestics in the past.
I just hope during the meet that we do learn more and not have to deal with threads such as those in the 1/4 mile issue. None of these guys have ever driven a car that will do 10 sec or even 8 seconds. I have and I can tell you that there is more than step on the gas. I can be sure that if an Indy driver sat in a dragster and a dragster driver in a indy car, they will respect each others craft and not pass criticism. In both sports, people die from trying to be the best they can be and no one and I mean no one should put the other down.
Just a thought, when you go down the lane in a 7.8 sec 1200hp car, your eyeballs shake and you heart loses its beat. You have not time to really look at the red line, you have to shift by feel and if you get everything all right, you get your data aqusitions back and they tell you that there was slippage in the the drivetrain which means you did not launch properly. etc. etc. I love this sport, I love indy, formula 2000, rally, and everything in between.
Til then, I'll see you then.
Dindo
95 s4
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