Exhaust Valves

[PSI NRG]

I’ve read a few different opinions on exhaust valves for these cars. Obviously they are sodium filled and pretty weak. But at what power level should you consider changing them?

Doesn’t seem to be any clear cut path for upgrading exhaust valves as there is rods.

Thanks!


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[Fast4esT]

I have read that stock valves are fine up to the 400hp range, particularly if you are keeping the 7200 rev limit, opening the exhaust manifold up may help keep temps down a bit also

[PSI NRG]

I have read that stock valves are fine up to the 400hp range, particularly if you are keeping the 7200 rev limit, opening the exhaust manifold up may help keep temps down a bit also

I run a long tube equal length header, definitely frees up the exhaust side.

Thanks for the input!


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[BumblebVR6]

Supertech inconel valves are a safe bet at any power level. That’s what I’m going to use on my build soon and keep the stock intake valves along with a Supertech spring/retainer kit.


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[PSI NRG]

Supertech inconel valves are a safe bet at any power level. That’s what I’m going to use on my build soon and keep the stock intake valves along with a Supertech spring/retainer kit.


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Damn that’s big money!


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[BumblebVR6]

Damn that’s big money!


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Gotta pay to play :-)


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[Fast4esT]

Valves and seals are 300ish, can’t be any more work than pulling and cleaning and new seals for stock valves. I’m debating if I should do exhaust valves at this point with head swapping. Guessing maybe not a bad idea if running an eliminator series turbo. Ran pretty hard for 60k so far on stock valves without issue

[Kevin C]

Sodium filled valves run cooler and provide an alternative path for disapting valve heat. Cooler valves can help reduce octane requirements and reduce the thermal load in the combustion chamber. A cooler chamber is less likely to crack.

Sodium filled Inconel:

https://www.supertechperformance.com...-exhaust-valve

[Fast4esT]

Sounds like a good idea when running higher boost

[BumblebVR6]

Sodium filled valves run cooler and provide an alternative path for disapting valve heat. Cooler valves can help reduce octane requirements and reduce the thermal load in the combustion chamber. A cooler chamber is less likely to crack.

Sodium filled Inconel:

https://www.supertechperformance.com...-exhaust-valve

Please note, this is the single groove stem version and will not work with the triple groove oem keepers. Supertech offers that option as well.


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[Fast4esT]

you are replacing all valve springs? are you raising your rev limit? springs add cost up real fast

[PSI NRG]

No plan to go over the factory rev limit. I really only plan on running a gtx2863 eliminator or full frame I haven’t decided. I just did IE rods calico bearings with stock pistons. Put a rebuilt AEB head on that is converted to VVT.


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[Fast4esT]

Using oem springs?

[PSI NRG]

As far as I know yes. AEB head was bought from a friend who said it was rebuilt.

IMG_7511.jpgIMG_7513.jpg


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[EuroxS4]

Ferrea valves for the win!!Supertech valves eat valve guides if you used certain cams. exhaust valves are the weak point anyway. Super alloy ferrea valves should handle it all.

[PSI NRG]

How much power can the stock exhaust valves handle? My motor is already back together and in the car getting broke in. I’m still on a K04 right now but the next turbo should be much bigger. Just sucks wish I would have known ab valve weakness before it was put together. The head will have to come back off. Or I’ll just have to build a spare then swap it.


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[EuroxS4]

Probably 350whpish maybe a tad more. But I dont see them lasting long then again it depends on exhaust temps as well.

[Fast4esT]

Ideally I don’t want to spend the money either but they sound like a good idea.

What’s this about Supertech valves eating up guides? That’s with the triple grove, not single? I haven’t come across this in my readings yet, but only been reading on 1.8 forums

[PSI NRG]

There was a dude I just saw a thread in one of the FB groups made 491whp w just doing rods. And Chinese maxspeeding rods at that. Totally stock head and pistons. Don’t even think he used upgraded head bolts/studs!


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[Stroked1.8t]

I built my engine 10+ years ago and put a stock AEB head on it. Dynoed at 429/411 in a FWD Golf. Motor swapped it into an 04 A4, bigger turbo, e85. Maxed out my 1000cc injectors, recently added staged injection and allowed me to rev to stock redline. I have no proof of power other then what my ecu reports, north of 500 it says. Still on a stock AEB head with stock valves.

The head is the next upgrade.

[PSI NRG]

^^ See that's wild! So many different opinions, it's hard to know what to believe!

[Fast4esT]

I agree. I didn’t factor cost of springs or guides either, seems no real clear consensus

[J_L]

I ran supertech stainless valves with Cat Gold springs on my AEB head for years, no issues whatsoever. Stock cams and redline.

[Kevin C]

Comparison of the heat flow of a sodium filled valve vs a regular exhaust valve. Lower valve temperatures help reduce octane requirements and reduces stress on the valve seat.

[EuroxS4]

I ran supertech stainless valves with Cat Gold springs on my AEB head for years, no issues whatsoever. Stock cams and redline.

This issue only occurs with higher lift cams or performance cams IIRC.

[Fast4esT]

Let’s say I’m going to install a 120k mile AWM head, it’s all stock, if I install supertech exhaust valves, can I reuse my springs and guides? It’s a new to me head, any way of telling if springs or guides need to be replaced? Currently on gt2871 elim with 630cc Uni tune, future plan is Motoza tuning and maybe gtx elim turbo. No plans to raise rev limit

[Stroked1.8t]

I made a call to USRT to ask about the springs on their website. I didn't catch the guys name but he was super helpful and answed all the question I had concerning springs, valves and the head in general.
Basicly these engines don't need to rev higher then stock unless your turbo comes online at 6500. So considering your not trying rev past stock you don't really need springs, but if you are installing cams with more lift then the stock springs can handle then springs should be upgraded.
Most aftermarket springs will require a new retainer as the stock retainer doesn't fit the aftermarket spring well enough.


The rest is mine

If you want to 2 step your car, this creates a massive amount of heat that the exhaust valve is the first to feel. Given enough time this will likely damage the valve and it will retaliate on your engine. If you have no intention of 2 step and can fuel the engine properly, keeping EGTs down then there is no real need to change valves.

If someone decides to change the valves, the stock valve guide can be used if the diameter of the valve stem is the same size or larger then stock. In the event the stem is larger, the guide should be honed to proper size.

I am looking into all this myself as I want a more robust valve train.

[Fast4esT]

Nice research dude! Thank you, this makes the process of upgrading exhaust valves much easier to stomach, or the idea of leaving the head completely stock

[Kevin C]

The only caveat on the springs is if the turbo is creating a high back pressure you may need a bit more spring. This was on a Frankenturbo that has a somewhat restrictive hot side.

On our transversal engine Jetta test car we found an airflow sweet spot of about 240g/s. If we boosted enough to hit 250 the exhaust valve springs couldn't hold the necessary exhaust backpressures, and we got misfires. But that was only in dyno testing. On the street, with a heavier quattro car, I can see how such airflows might make for good results.

Thank you for the information.

Post # 337

https://www.audizine.com/forum/showt...essions/page10

[PSI NRG]

Love all the info!

And cylinder pressure does hold true for upgrading springs. A good friend of mine experienced this with his DSM from our understanding the valve train was upgraded. But that proved to be not the cause because on a 66mm turbo it couldn’t make more than 28psi without misfiring. It wasn’t an ignition misfire from the data but ended up being that the head had factory springs and couldn’t keep up with the demand of the higher cylinder pressure.


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[Stroked1.8t]

Please don't think I'm doubting your story.
A valve opens to the inside of the cylinder, meaning it moves towards the piston when it opens.
If the cylinder pressure where very high this would promote the the valve to shut harder. Peak cylinder pressure is created before the exhaust valve opens. My thinking is high cylinder pressure will not open the valve.
On the other hand, if, exhaust back pressure where high, when the piston is coming up the valve is opening or open and it's pushing the spent exhaust into a very restrictive environment, building more exhaust back pressure, as the exhaust valve is trying to close, I could see the back pressure keeping the exhaust valve open as there may be a lower pressure on the piston side of the valve.
If it was high cylinder pressure opening the valve, it's something that doesn't make sense to me, if it was high exhaust back pressure, springs would fix both situations. Any chance back pressure was monitored?

[Kevin C]

Option #3 The pressure isn't opening the valve it is reducing the seating force since the valve is open after TDC on the exhaust stroke. As the valve closes the exhaust pressure between the valve and the turbo works against the spring pressure. That reduces the effective spring pressure. Or another cylinders exhaust valves just opened as that cylinders valves are just starting to seat. and the pressure pulse causes the valves to hang.

[PSI NRG]

That was the conclusion the tuners at TPG told us. It was due to valve springs not allowing the vehicle to make more boost and causing misfires. So whether the valves were hanging open or being pushed shut it couldn’t keep up with more boost. Literally they would try and turn it up and it just wouldn’t make it it would just misfire. Spark wasn’t getting blown out either.


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[Stroked1.8t]

My experience
I run a 58mm turbo on a homemade 1.5" runner SS T3 flanged manifold. Stock head. Custom 2.5" downpipe that reduced down to join with factory exhaust. At boost levels below 22 there was really no issues. When I would try to turn it up it would misfire in boost. I changed plugs, coils, timing, tune, nothing fixed it. So for a while I lived with boost at 22.
One day I got a bright idea to take my mufflers off. Car picked up spool and boost. Interesting. Then I proceeded to remove the remaining factory exhaust, down to just the downpipe at this point. Car picked up more spool and boost. We are getting somewhere now.
Ordered up 3" exhaust pipe and fabbed a downpipe and full exhaust. I doesn't matter how much boost I throw at this thing now, it doesn't misfire anymore. Currently the boost controller is set to 30psi, doesn't misfire.
My case had nothing to do with valve springs, but data would tell me it had everything to do with back pressure.
I know every case isn't this clear cut, but this was my experience. Still stock head.

[PSI NRG]

Interesting. This vehicle is using a 67mm turbo and full 3 inch exhaust from the turbo back w 44mm external wastegate dumped to atmosphere. As well as an equal length tubular header. Should have plenty of exhaust flow.

In your case it makes sense the amount of air you’re pushing through the tiny factory exhaust on a 58mm turbo would be like blowing through a straw.


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[Gin+]

I built my engine 10+ years ago and put a stock AEB head on it. Dynoed at 429/411 in a FWD Golf. Motor swapped it into an 04 A4, bigger turbo, e85. Maxed out my 1000cc injectors, recently added staged injection and allowed me to rev to stock redline. I have no proof of power other then what my ecu reports, north of 500 it says. Still on a stock AEB head with stock valves.

The head is the next upgrade.

How are you controlling the staged injection? BTW, this thread is awesome!

[Kevin C]

My experience
I run a 58mm turbo on a homemade 1.5" runner SS T3 flanged manifold. Stock head. Custom 2.5" downpipe that reduced down to join with factory exhaust. At boost levels below 22 there was really no issues. When I would try to turn it up it would misfire in boost. I changed plugs, coils, timing, tune, nothing fixed it. So for a while I lived with boost at 22.
One day I got a bright idea to take my mufflers off. Car picked up spool and boost. Interesting. Then I proceeded to remove the remaining factory exhaust, down to just the downpipe at this point. Car picked up more spool and boost. We are getting somewhere now.
Ordered up 3" exhaust pipe and fabbed a downpipe and full exhaust. I doesn't matter how much boost I throw at this thing now, it doesn't misfire anymore. Currently the boost controller is set to 30psi, doesn't misfire.
My case had nothing to do with valve springs, but data would tell me it had everything to do with back pressure.
I know every case isn't this clear cut, but this was my experience. Still stock head.

Reducing the pressure behind the turbine reduces the pressure in front of the turbine, so yes that will affect the pressure the exhaust valves see and fits the pattern of exhaust back pressure causing the exhaust valves not to seat properly.

[PSI NRG]

So in conclusion a restrictive exhaust could cause enough back pressure to hang valves and cause misfires right?

In regards to the boost issue I thought about it more and came up with this why a stronger spring would make sense to hold more boost:

On a turbocharged car the whole intake is pressurized. Even the runners up to the head. The intake valves and spring pressure are whats holding that from opening. Well if the spring cant hold the valve shut the pressure on the other side (intake) will force it open. Which would be like a vacuum leak. Which we all know when we have vacuum leaks we have misfires. Its like running too soft of a spring in a DV the pressurized air will over power the spring thus pushing it open and creating a leak.

So I think that would explain why upgraded springs would be needed. Not necessarily because of cylinder pressure but because the forces are too great behind the intake valve.

[A4SoftWalker]

The simplest way to think of everything is the valve flutter phenomenon at high rpm and high boost.
If the springs have a spring-rate that is not high enough to cope with the speed demanded by the valve-train at high rpm then the valves will not be able to close on time and the motor will run rough.
Also if the spring-rate is not high enough to close the valve at high psi after the lobe that opening it has moved on the same result is a rough running motor.

This cutaway drawing of a valve spring shows whats happening



Here is a link to a good article on the topic.

https://www.aa1car.com/library/valve..._diagnosis.htm