Mythbuster: continuing project thread of my 1303 '75

[Wally]

Originally Posted by judgie

looking good. be intresting to see the dyno results on this set up compered to the old one.

Are you going for more boost or was the swap to the bigger turbo to control the boost better?

Neither actually: this huge turbo was intended for fitting together with an engine upgrade to more cc's. Then a big turbo like this would make more sense. The bigger cc u[pgrade didn't happen however, hence I thought trying it on the current engine I have so much data already from.

The other idea was to decrease exhaust gas back pressure by using an even bigger (compared to the already bigger compressor) turbine wheel.
So, the turbine wheel now is double big so to speak... hence the to be expected huge lag. I think partly due to the twin-scroll set-up, lag is not as terrible as it would have been otherwise.

OTOH, less back pressure will make higher boost settings possible. For example: 20 psi gave me 30psi back pressure(!). You can fill out what this means if you have a (assuming) 1:1 ratio...
Question is will the engine internals withstand the mechanical forces (++torque) of more boost or even same boost but with more power because of the better VE I think I have now?

I tried tuning it on the road, but frankfully, its too tricky on a public road at the boost settings above 15 psi. Tuning is not complete therefore, but close enough
-only one way to find out: drag it to the dyno

[Wally]

Dyno has been booked for coming saturday...

[Steve Arndt]

It will keep on making power until the valve springs float.

[Sandeep]

Fantastic !

Based on your last "seat of the pants" comment, I'm guessing you'll be dynoing to 15 psi then ?

Are you still using the ID1000's ?

Looking forward to the results and the conclusion of your exhaust back pressure / turbine size testing.

Sandeep

[Wally]

Originally Posted by Sandeep

Fantastic !

Based on your last "seat of the pants" comment, I'm guessing you'll be dynoing to 15 psi then ?

Nah, what fun would that be? There is now a 15 psi waste-gate spring in it, so 15 psi will be the lowest boost pressure setting. Waste-gate spring is setting 1 on the EBC. There are 5 settings after that
If the engine will hold (knock on wood), I want to at least test 22 psi (1,5 bar) as well. It looks like this combo holds boost pretty constant across the rpm range.

Are you still using the ID1000's ?

Yep, they might be on the small side by now, we'll just have to see...

[Wally]

Unfortunately, no such luck today: injectors were at 100% IDC already at 1,3 bar boost and ~6500 rpm...
But 398 hp and climbing at 1.3 bar but running at lambda 1.0 and 1.1 at that power level... that probably did the engine no good, but no problems leaving the dyno...but I still did strand on the way back home. Seemed like electrical problems or fuel delivery problems or ?
Not sure what it is yet though...

This was the first run at 15 psi:
http://www.youtube.com/watch?v=9TOIdkF6mbg

[Bad bug]

You made almost 400 whp at 19lbs of boost. You were also lean, need to increase fuel at that level.

[al_kaholik]

Originally Posted by Wally

Unfortunately, no such luck today: But 398 hp and climbing at 1.3 bar

Good Effort Do you have any dyno or track/ 1/4mile times from before you did anything? Would love to see the complete difference in performance from a stocker.