Full bolt on with stock turbos you will have a lot of acceptable exhaust options EP stage 1 being one of them. 08957's data when he had stock turbos tuned by Sam was fine on the Stage 1. I wouldn't worry too much, pick the one you like the most on the stock turbo airflow

I also think Europipe modifies the stock tips only their stage 2, could be wrong.

 

I'm somewhat puzzled that the aftermarket exhaust becomes the limiting factor when the backpressure from the turbos themselves are the "weak link". If the restriction point is the turbo then why does the exhaust size have so much effect? I understand that you always want to have low resistance after the turbo but if the turbo is the bottleneck then I'm still a little puzzled, lol. C'mon Maestro - explain!

 

Todd had explained years ago that in order to generate the higher boost on the vtgs the vanes had to be clamped down fairly tightly which increased heat/backpressure in a big way. I know that you can hold 23psi all the way to 7k rpm but has anyone shown that you actually make any more power above 6k rpm with higher boost on vtgs????

 

I agree with the order of highest loss to lowest loss, that's what I would expect. I appreciate you did all the testing, if I was selling exhaust I would have done the same. However with simulation you would have built just one, not 19 LOL. Don't under estimate it. I don't mean that in a bad way, it just the way its done in industry. Its the only way we can do things faster, cheaper, and more accurate to cut down on development (time and cost).

Yeah I'll let everyone know if I measure it. If I DO measure, I'll measure it with piezo rings so its accurate. Just 1 tap per location of interest is not accurate because of dynamics of the flow.

Yet again I'm jumping off the exhaust craziness bus...this may be only 2nd on this platform to freaking intercoolers lol.

Appreciate the discussion no doubt about it but I have to move on.

 

Bogg they are linked not separate, you need to think of these things from a system level not component. It goes back to turbine power. The lower the exhaust restriction the higher turbine power you will be able to achieve. However you will still be limited by the turbine stages efficiency in this case. So I would expect 08957's car, targeting the same boost pressure, would re-balance at a more open vane position with less exhaust restriction. If he wants more boost r then the tuner would re-clamp the vanes to where they are comfortable. However we would NOT be achieving the turbine stages max flow under WOT because to match the power the compressor is requesting we are achieving it by driving higher expansion ratios with clamped vane position. Why because of efficiency as I have said many times. I know because of their experience with fixed geometry/wgt people keep thinking about this in terms of turbine flow...its not turbine flow. This stage flows a lot more than what people realize, its just we can never get there due where the peak turbine power generating capability is.

 

exactly...you can't get there because the vanes have to be clamped down in order to get the higher boost pressure. So effectively the turbine becomes the limiting factor, lol

 

AFTER everything else has been optimized...that is key.

 

I thought friction was related to cross sectional area AND distance. The tips may be the limiting factor for flow but since they are short compared to the entire exhaust I didn't think it would turn a 80mm exhaust into a 60mm effective exhaust. But what do I know, lol.

 

I would consult with Stef at Europipe on the best unit for your needs

My personal opinion is on the stock turbo the EP 1 is the best combination of performance and lack of drone

my 750 whp on the EP 1 shows is clearly is capable of making huge power

 

the back pressure from the tubo is fixed. That can not be changed unless you modify the turbo itself Lets assume 50 psi back pressure at 22 psi of boost on E85 as a rough estimate.

my point if you add an exhuast on the tail end that adds say another 6 psi peak additionsl back pressure on top of what you have before the turbine that is only going to make matters worse

Obviously to the extent that you can free up exhuast flow after the turbo that will help the situation

then perhaps you can lower the boost target one psi and make up the power with timing and fuel adjustments

I will report more as my story unfolds

 

Gotcha...so restriction is additive rather than bottleneck

 

In reality the stock rods are the liniting factor as VTG turbo cars are more than capable to make enough power to exceed the limits of the stock rods

a turbo charged car is like a giant air pump - period

 

Every sharp bend; every neck down, every joint that is not totally smooth all creates friction and turbulence

Obviously a rear engine car creates a significant issue when designing an exhaust system as the direction of flow is being re-directed and changed several times in a very tight area.

Best book I ever read "Maximum Boost" it is like my bible and was my text book when I used to teach a course on tuning ecus back in the day - you have to know the basic foundation before you can master the advanced concepts of course most of this stuff was worked out years and years ago reaching its pinnacle during WWII with the race to win the war in the skys with the fastest and most powerful planes. There is nothing new about any of these concepts, only thing that is new is the wider distribution of E85 at the pump

 

You actually can push them, but as has been mentioned already, backpressure is your enemy #1. As you can see in the following pic, maximum hp can be held like a plateau for a long time. The last 500 revs are not very accurate with the Insoric mesurement device. In reality the power goes quite flat up until 7000 and then decreases.