Just a quick question, I have been chatting to a few people about the advantages and disadvantages of installing a dumpvalve on my stock A4 1.8T. Now, the general feeling is that a dumpvalve will prevent backpressure from destroying my turbo impeller when coming off the power quickly when at top revs.

To be totally honest, I know very little about turbos and hence the question. Is a dumpvalve a good idea or not on a stock car that may be modded with a chip and exhaust shortly? (Chip will increase power output from 110kw to a claimed 140kw)

Bradley

Bradley, when you are referring to a dump valve, do you mean one that vents to the atmosphere? The basic function of a diverter valve or a dump valve is to release boost when you get off the throttle to for instance change gears. The turbo is at that stage pumping a large volume of air into the inlet manifold and if this air was left in the system, the turbo would stall. The diverter valve therefore blow the excess air back into the air system (normally into the pipe between the MAF and the turbo), whereas a dump valve would do the same but blow the air into the atmosphere.

The problem is that your ECU expects the air to be blown back into the system and if you put on a dump valve the air is lost. The ECU knows how much air is in the system from reading the MAF. If your ECU is not modified for a dump valve your fueling will be wrong. I would stick to a diverter valve - a dump valve may sound cool but has no performance benefit.

You can look at fitting a better diverter valve which should last longer (but won't really work any better than the OE Bosch diverter valve). I would only worry about that on a chipped car.

Thank you for the input but would it then not be better to fit a sequential dumpvalve as these close completely during idle?

Rathre buy a diverter valve (same as stock unit - recirculating). Try the Forge od Bailey DV30, you won't regret it.

Audi A3 1.8T
ex "BroSpeed" RXi

Hi
We are the Forge distributors for SA, so hopefully this info helps.
If you are running extra boost with a chip, you should consider running a higher spec. DV. Simply put, they are better equipped to divert under load in higher boost situations. They are similar in design to the Bosch OEM, but have a longer canister and more durable construction, and are also serviceable on most brands.
THEY DO NOT RAISE ENGINE OUTPUT! However, what a good engineered DV will do is respond faster and more efficiently when requested to do so, maintaining boost and therefore a smoother transition of power.
The VAG 1.8T motor is designed to recirculate pressure into the turbo inlet pipe that leads into your turbo based on a momentum principle, especially with the low pressure turbos in the A4. They are not designed to boost atmospherically, so always choose a diverter valve. Some guys like the sound of the boost rushing out which is why they choose these, but they are less efficient even in hybrid form.
There are 2 types, piston and diaphragm, which way you go determined by what changes you have done to the car

Hey guys,

Should I be looking at a different DV on the TDi, or will the stock one be ok - what's the advantages and disadvantages?

From what I understand, the diesels shouldn't have a DV at all, seeing that there is no throttle valve (?), so no protection is necessary - or am I missing something?

Surely my only variable is the amount of boost from the turbo (which is more than stock now with REVO), and the amount of fuel, but the amount of air isn't actually controlled by throttle position.

I'm feeling blonde at the moment, so I'm sure I'm missing some part of the plot here - maybe the groot gat is getting to me...

Rich

Will, how much would I be looking at for a Forge DV purchased from yourselves ? Audi Dornat Braamfontein, quoted me R434 for the Bosch unit !!

from Bradley's thread, am i correct to understand that his car has NO DV ? i was advised that all turbo's have DV's and was looking at replacing mine as well with an original Bosch part from Audi...was also advised that the 1 that fits on a TT fits on mine...'98 1.8T

jammer, knowledge of engines & turbo's are SERVERELY limited

One has to distinguish between a Dump Valve and Diverter Valve like they guys say here. As far as I know, all 1.8T's come with a Bosch Diverter Valve (factory standard)... but I've read that they are prone to failing after a while ... how long I don't know ...

Someone please correct me if I'm wrong ...

Cheers

I got this from the HKS site:

The HKS Super Sequential Blowoff Valve (SSQV) is a dual stage pull type relief valve. Unlike other blow off valves that are push type, the SSQV will not leak under high boost conditions nor under vacuum at idle. Being of a pull type valve structure, the SSQV can not physically leak under any level of boost because boost pressure also keeps the valve closed against its seat. The SSQV is actuated by pressure alterations only, not by the rate of pressure or vacuum in the line, which ensures a quick valve response and complete closure during idle. On typical blow-off valve designs, a large valve is utilized in order to accommodate high boost / high horsepower applications. However, these large valves tend to react slowly and require high activation pressure to open, therefore are not able to activate and prevent compressor surge at light-load conditions. On the other hand, smaller, fast reacting valves do not discharge the airflow capacity required for high horsepower applications and tend to creep open and leak as the boost pressure overpowers the spring on these push type valves. For maximum performance, the HKS SSQV incorporates both a small primary valve for ultra quick activation, along with a larger secondary valve for additional discharge capacity. The SSQV is engineered to initially open the small primary valve at light throttle and load conditions, then sequentially opens the secondary valve for additional relief capacity under high boost and load conditions. The SSQV is constructed of polished billet aluminium, which ensures long-term durability and visual appeal. The triple-fin discharge port design produces a powerful and unique aggressive blow-off sound along with added visual distinction.

While it looks like a very good dump valve, it vents to air which will confuse the ECU if it is not programmed to use such a valve (20VT, Chris or Will help on the programming issue!)

All the 1.8T's have DV's. The stock one is a Bosch unit

Forgot to mention that I ordered a Bailey DV30 and should be receiving it soon.

I will give some feedback once I've installed it but from all the research I've done it seems like one of the best valves out there and it is a direct replacement of the std Bosh unit!

Audi A3 1.8T
ex "BroSpeed" RXi

Hey guys,

Should I be looking at a different DV on the TDi, or will the stock one be ok - what's the advantages and disadvantages?

From what I understand, the diesels shouldn't have a DV at all, seeing that there is no throttle valve (?), so no protection is necessary - or am I missing something?

Surely my only variable is the amount of boost from the turbo (which is more than stock now with REVO), and the amount of fuel, but the amount of air isn't actually controlled by throttle position.

I'm feeling blonde at the moment, so I'm sure I'm missing some part of the plot here - maybe the groot gat is getting to me...

Rich

The groot gat is making himself a little brother right there between your ears buddie,

but a interestign question i would also like answered.

heheh

G

Ok, seeing that everyone is ignoring me, lets try again...

1) do TDi's have DV's?
2) if so, why - there should be no throttle like in a petrol engine, and surely the DV is there to protect the turbo when the throttle is closed...
3) if there is a DV, would one need to upgrade after chipping?
4) if so, then what is the recommendation of our learned members?

Cheers
Rich

Every Audi engine has a DV, petrol or diesel (I think)

Changing your DV to a Forge, GFB etc.. will only improve reliability, as Bosch DV's (the standard in Audi's) are prone to failure, from heat and high boost, and when they fail they could damage your turbo.

A chipped car, which has a higher boost, needs a new DV which can cope with the higher boost. The Bosch DV may be able to cope at first but will not last for long.

My original Bosch DV's on the RS6 lasted for only 3700 km !!! For the S3, if driven hard, after 7500 km most of them fail.

I have replaced the ones on the RS6 with 2 Forge DVR and a special soft spring, and the one on the S3 with GFB for reliability's sake only. Both are diverter valves.

André