SWB Quattro Project

[Billman]

My turbo seem not to have an issue with the stock wastegate. Running 1.8 bar and having 60% N75 DC on stock spring. Turbo has an 65/75 turbine wheel and 0.70 turbine housing.

So either:

1. That wastegate has a big 44mm opening but can't flow enough.

2. The spring is very strong and cannot open with the current N75 DC

3. My head flows crappy so you have to provide me one for a head to head comparison

[G60Rallye]

Its irrelevant comparing other engines realy. We proved on the dyno the gate is wide open and still it cant bleed enough gas to hold boost.

[nervas]

Same problem I had with tial 44mm. Tial WG have not very big lift, you should first try to modify WG lift to have minimum 25mm ...
Lift is more important then valve diameter

[Jamo]

Maybe this is why I haven't seen this issue with turbosmart wastegates?

[JP]

My turbo seem not to have an issue with the stock wastegate. Running 1.8 bar and having 60% N75 DC on stock spring. Turbo has an 65/75 turbine wheel and 0.70 turbine housing.

So either:

1. That wastegate has a big 44mm opening but can't flow enough.

2. The spring is very strong and cannot open with the current N75 DC

3. My head flows crappy so you have to provide me one for a head to head comparison

1. The valve is 44mm the opening is 42mm
2. We proved on the dyno and on the logs the wastegate was fully open at 3700/3800rpm
3. lol good try

Same problem I had with tial 44mm. Tial WG have not very big lift, you should first try to modify WG lift to have minimum 25mm ...
Lift is more important then valve diameter

Lift becomes irrelevant beyond 15mm due to the design of the seat and valve. A hole will only flow so much before it achieves choke doesn't matter how high you lift it beyond that

As a reference point a 42mm opening has surface area of 1385.622mm2 divide this by circumference of circle (131.964) = 10.5mm

So at 10.5mm the valve has enough lift to allow maximum flow through the hole so even at 15mm it is already overkill.

A 42mm hole with nice valve angles will flow 130cfm @10" pressure drop. The exhaust ports on the head flow 124cfm @10" each if I go back in my records compared to 88cfm @10" of a standard cyl head. Doesn't matter how nice a 44mm wastegate it is it just isn't going to work. Whereas a 60mm wastegate would flow 250cfm @10"

I just wish I'd done these calculations before, worked on the assumption it would be ok because on a ported stock 34mm wastegate there was no problems with the smaller frame gt30 turbo, then again we can only learn from it.

Anyway putting all that aside Mr Hamish the good news is I've done some measuring and a 60mm wastegate dimensionally is no more in height than a stock one and there is enough space diameter wise to mount it. If you wish to plumb it back into the downpipe it would have to be into the top elbow of the downpipe. Alternatively I've got enough space to squeeze a 2.25" pipe through which will either join further down the exhaust rather than the downpipe with a slip joint or just run a separate silencer for it and kick it down to the ground.

[G60Rallye]

The 44mm lifts a good way up, I dont think Tial would have designed it to limit flow due to lack of lift? 60mm is the way forwards I just need to decide how to get back into the downpipe. Could go back into the downpipe higher up or come around the front of the manifold and then under it and join the exhaust just before the driveshaft. I will have to eye it up.

[Jeffer]

Its starting to get a little bit annoying this car!

Keep at it Hamish. I've reached that point several times...

I also changed from a 44 to a 60 mm WG. I wanted the spring pressure to be 0.8 bar just to be sure that if anything fails it would be within limits.
Now it works like a charm.

(btw; I couldnt fit 2 x 44 mm's in my engine setup.... Only 1 x 60 mm)

Good luck!

[G60Rallye]

Thanks for the pick me up JP! Walked away from the car this week to have a break.

I remember you changing to the 60mm but considering the size difference between the gt42 and gt35 I thought a 44 would do be fine. The more I am looking into it the more others are having the same sort of problems. Like you we want to be able to run spring pressure right to the red line.

2 x 44mm's will not fit in mine either the single 60 is the way to go!

[Billman]

1. The valve is 44mm the opening is 42mm
2. We proved on the dyno and on the logs the wastegate was fully open at 3700/3800rpm
3. lol good try

I had to

Lift becomes irrelevant beyond 15mm due to the design of the seat and valve. A hole will only flow so much before it achieves choke doesn't matter how high you lift it beyond that

As a reference point a 42mm opening has surface area of 1385.622mm2 divide this by circumference of circle (131.964) = 10.5mm

So at 10.5mm the valve has enough lift to allow maximum flow through the hole so even at 15mm it is already overkill.

A 42mm hole with nice valve angles will flow 130cfm @10" pressure drop. The exhaust ports on the head flow 124cfm @10" each if I go back in my records compared to 88cfm @10" of a standard cyl head. Doesn't matter how nice a 44mm wastegate it is it just isn't going to work. Whereas a 60mm wastegate would flow 250cfm @10"

I just wish I'd done these calculations before, worked on the assumption it would be ok because on a ported stock 34mm wastegate there was no problems with the smaller frame gt30 turbo, then again we can only learn from it.

Anyway putting all that aside Mr Hamish the good news is I've done some measuring and a 60mm wastegate dimensionally is no more in height than a stock one and there is enough space diameter wise to mount it. If you wish to plumb it back into the downpipe it would have to be into the top elbow of the downpipe. Alternatively I've got enough space to squeeze a 2.25" pipe through which will either join further down the exhaust rather than the downpipe with a slip joint or just run a separate silencer for it and kick it down to the ground.

If it goes off topic and you like make a new thread for it:

How much can the stock WG flow on a stock head/turbo setup and it can hold spring pressure to the redline?

[Jamo]

Thanks for the pick me up JP! Walked away from the car this week to have a break.

I remember you changing to the 60mm but considering the size difference between the gt42 and gt35 I thought a 44 would do be fine. The more I am looking into it the more others are having the same sort of problems. Like you we want to be able to run spring pressure right to the red line.

2 x 44mm's will not fit in mine either the single 60 is the way to go!

Making me nervous that my WG will be too small

[Thuppu]

Making me nervous that my WG will be too small

You're not alone with that feeling.

On the other hand, I shouldn't have problems as my head propably flows like a stock one.

[Jamo]

Well this is it, I have no idea on my head, it's ported but how well I don't know. I've asked a few people and they only want to work on a "fresh" head so for now it's staying

I seriously doubt we will have these issues as these elitest 3 have welded exhaust ports and big extra flow which seems to be the issue.

[europeanme]

You're not alone with that feeling.

make that 3 concerned parties...possibly 4...

would the hotside size effect this over boosting issue or is it the head work?...

[Thuppu]

The smaller hotside the more the WG needs to flow. I had no problems with your CT and stock WG.

[Jamo]

Europeanme your build isn't near this level of concern Thuppu, G60rallye, JP all have potential 700 bhp+ setups. I'm not near that probably 600-650 but stroker flow.

It all seems to do with the extreme head porting which again only JP, G60rallye and Jeffer have