blueflame turbo back fitted

[Cupra Ross]

So your saying that if my car had an OPTIMAL MAP it would have made better torque with the 2.5" than the 3"?? Just for your info my car was mapped with the 2.5" fitted so that kinda blows your theory clean out of the water!

You seem to be taking this very personally mate. I'm not trying to have a dig at you or anybody else. It is a widely accepted reality that an increase in downpipe diameter results in a commensurate decrease in exhaust gas velocity, the force that spins your turbo. This may be fine on a large turbo with great big vanes but you get to a point on a small turbo such as the K03S, where the reduction in velocity starts to effect performance.

Piper are no newbies to the exhaust game. I was simply echoing their findings with information I have previously accumulated. On a turbo such as the K03S, a 2.5 inch downpipe will provide greater performance and efficiency at maximum output than an otherwise identical 3 inch downpipe. If you had a performance gain when moving from a 2.5" DP to a 3" DP with all other things being identical, it would suggest that you were running a very conservative map.

Again, I am NOT having a go at you as a person, your map or anything else on your car.

All I can say is that I have the blueflame turbo back exhaust fitted (inc. 3" downpipe and cat) and I love it.

As far as i'm aware, turbo charged engines are happiest when there is very little back pressure. N/A cars are a bit different but we won't go there now.

Surely a bigger downpipe would reduce back pressure?

Just my 2p's worth.

Blueflame make top quality systems, there is no doubt about that. As above, what you say is broadly true but back-pressure reduction must not be achieved at the expense of exhaust gas velocity. Piper's and many other organisation's extensive research suggests that anything over 2.5" on a K03 size turbo results in exactly this. Milltek do make a 3" downpipe for the Leon but it is recommended for use on K04 and larger turbo setups.

 

[cuprabaz]

I know your not directing this at me or having a dig. I just disagree with what your saying about the 2.5 giving better results as i have proof of the opposite.

 

[SidewaysCupra]

I hope we can have an intelligent discussion about this without resorting to the usuall forum nonsense. As i've said previously i'm no expert and you seem to be a "well read" sort of guy so i'm ready to be corrected.

However you state that "It is a widely accepted reality that an increase in downpipe diameter results in a commensurate decrease in exhaust gas velocity, the force that spins your turbo"

As is my understanding the downpipe comes after the turbo. Surely something being fitted after the turbo would not increase or decrease velocity. Pressure maybe. But velocity (speed)?

 

[Cupra Ross]

I hope we can have an intelligent discussion about this without resorting to the usuall forum nonsense. As i've said previously i'm no expert and you seem to be a "well read" sort of guy so i'm ready to be corrected.

However you state that "It is a widely accepted reality that an increase in downpipe diameter results in a commensurate decrease in exhaust gas velocity, the force that spins your turbo"

As is my understanding the downpipe comes after the turbo. Surely something being fitted after the turbo would not increase or decrease velocity. Pressure maybe. But velocity (speed)?

I've been called many things mate but "well read" is not among the most common. The downpipe does indeed attach itself to the ar*e end of the turbo. Subject to the diameter of the exhaust turbine housing, a larger diameter downpipe allows gas to flow out of the turbo at higher volume and lower pressure than the standard system but it also flows slower which is not a good thing.

This article talks mainly about manifolds but there are some very good points raised about velocity and expansion and the relationship they share with exhaust pipe volume:

http://www.valvoline.com/carcare/articleviewer.asp?pg=pht20020501te&cccid=4&scccid=1


The general consensus that is reached by most studies is that a balance must be struck between alleviating restriction in the exhaust and maintaining sufficient gas velocity to allow a rapid spool of the turbo at low to mid range engine revolutions. This is why we see big turbo/exhaust combinations making big power at high revs but less power than a standard turbo at low revs.

The burning question as far as we are concerned is whether or not 3" DPs are larger than is actually required or desired on a K03S. Some very reputable companies think that this is the case but some owners have numbers that would suggest otherwise. I think there are too many variables to make a black and white statement (ecu mapping, modifications, dyno lottery, fuel quality, ambient temperature, air density, sensor reliability, the list goes on). I'm inclined to believe that a 2.5-2.75" downpipe is optimal for the small K03S turbo and small port head that we have in the AUQ engine. If you have a big turbo conversion or a hybrid, thats a different story. Mapping is a huge factor in any case.

 

[DaNnY_LaD]

Has anyone used the 3'' downpipe and de-cat that bf make?

Im running around 300bhp...got a ths one at the moment..

 

[Riko]

which one have you got danny? Looking on the THS website, it only shows dp's for the diesel and decats for the others?

 

[DaNnY_LaD]

Ive got the Ths 3'' dp for the leon..But its on my ibiza atm...

Works a treat it in the sale section too....

 

[Riko]

yeah just noticed I might be interested, but after this thread I'm a bit confused...!

 

[wilz]

Your not the only one confused.

I'm going hybrid so going to go for the 3" dp seems rhat would be sufficient.

 

[DaNnY_LaD]

I had a this 3'' dp on my stage 1 k03 and it went like stink...Vast improvement compared to my mates 2.5 miltek(Djscorch) as we had the same mods and mine was 2cars a head...

 

[cupramillo]

To all the doubters...Blueflame 3' all the way! Blueflame themselves developed this downpipe for the Ibiza and i dont think they would have designed it if they know it would perform any less than their rivals that use 2.5'

 

[s1l3nc3r]

I tend to agree on both sides of this but the way i understand it is i think 3" into 2.5" would be the choice to have. as said the dp is after the turbo so surely you want the most flow there as the air exit the turbo at high speed and the reduction in pipe size further down the system would give you the needed reduction in flow or "bottleneck" if you like to stop it from loosing torque lower down the rev range...but there are so many fators to take into account to test this theory eg:air temperature, hymidity,feul,air mass at altitude even. I dont see gaining results from individual cars a way of proving any facts...