If you want the boost to hit a stable 20psi to redline, try one of these things:


Works for me.

I am Joe and I approve this message.

 

Until it cracks.

 

i like the RnR unit better, or if David B would offer his cast mani that he has available for his 440BR or 550BR kits to upgrade your stock unit would be best !!!

 

Great thread of information. Awesome!! Thanks David.

 

David how much weight do you shed off the car at Stage 1?

 

"We left the 2.5" downpipe on, added a 2.5" offroad pipe and the 3" catback with the Magnaflow muffler. The horsepower jumped to 313 whp and 292.9 ft lbs. For further comparison we ran an open exhaust system from the back of the offroad pipe, in other words no catback at all, the car only made 1 more whp. The open exhaust numbers were 314.4 whp..."


Dave, Is the following assumption accurate? I believe that 15whp increase is attributable to running the 2.5" DP.

A.
(2.5" DP, 2.5" TP, and 3" catback) makes 313whp (per your dyno)

(2.5"DP, 2.5" stock cat, and 3" catback) ~ 298whp (15whp less than above)

B.
(2.5" DP, 2.5" stock cat, and 2.5" muffler delt. pipe) 289.3whp (per your dyno)

(2.5" DP, 2.5" TP, and 2.5" muffler delt. pipe) ~304.3whp (15whp more than above)

 

Wow. Great results. I just realized I have the equivalent of a BR stage 4 except injectors! Woohoo!

 

Robi,
Between the airbox and the exhaust the Stage 1 ends up knocking an additional 40 pounds of weight off the car. Good point.

DizzyTT,
There is no equivalent

4Bangr,
Depending on which order the parts were done yes, 15 whp. Let me go look at something and I will answer better.

David Buschur
www.buschurracing.com

 

4Bangr.

Check this out. I had to go back and double check. The further down the line you add the exhaust the more HP it actually gains on the car. In other words if you had an EVO making 400 whp through the factory exhaust and you added our full 3" exhaust you would probably gain 150 whp, see what I am saying?

So in another test we did we had the car at full Stage 1, boost up to 20 psi, AFC on the car etc. Just had the 3" catback on the car with the stock downpipe and stock cat. We then pulled the stock cat out and put a 2.5" offroad pipe in, the car gained 21.6 whp. We then put the 2.5" downpipe on and it gained another 19.7 whp.

As you can see, depending on which order you do the parts the gains can be quite substantial. Doing them in the opposite order will gain hardly anything. Start at the back and work towards the front. Always go from the same diameter tubing into the same or larger diameter, never larger to smaller.

David Buschur
www.buschurracing.com

 

Speaking of parts being added in the correct order there is something else I should have tried. I might have to go out and do it now actually. I would like to see the stock airbox back on the car with the complete Stage 1 kit on. I am guessing the gains from the airfilter would be pretty substantial at this point.

David Buschur
www.buschurracing.com

 

David,

I read earlier that you tuned the car for 11.7 AFR, is that through the whole power band? Also would like to know what the timing this car is seeing on peak boost and the 7k. These are some amazing results for your stage 1 car.

 

This would be interesting to see, specially for those who want their car to look stock.

 

The timing wasn't monitored, when we do the flash we will be changing and monitoring the timing curves.

The AFR's from 5,000 rpm and up were 11.7 at the leanest point. Up to 5,000 rpm in order to keep the car from fuel cutting the AFR's were as lean as 12.1:1.

I am really looking forward to getting Al down here to work on the flash for the car. The fuel cut can be eliminated with the flash and we will be able to run the car richer on the way up. I don't feel that on spool up the 12.1:1 ratios are at all dangerous.

The timing control with the flash should also net us some great gains in torque. These AFC numbers were just to get started on the testing. The flash is what I want to use/sell for the kits. The low end torque is just so much higher with them that it makes the cars feel much faster.

David Buschur
www.buschurracing.com

 

This is a 2.5" Dp, 2.5" Tp, 3" Catback exhaust
(Basically "horn shaped"; which is the "optimal exhaust" in many turbo theory books). That is it increases in diameter as it reaches the tail pipe.

SO a 2.5"DP will retain hotter exhaust gasses (at lower rpm) than a 3", thus they will reach the turbo slightly ahead of the 3" DP. (Torque).
Once through the turbo, the goal is to avoid any restriction or minimize any restriction in the exhaust path. I think that torque is optimized (when using the stock turbo) with the 2.5"DP - all things being equal.

As for turbo upgrades it is beneficial to run the 3" DP but maybe with 3.5" or 4" sections after the turbo. Limited by unfabricated parts 3" exhaust are used entirely, for now?

Can you run the 2.5"DP, stock turbo, 3" mid pipe, 3" TP, and 3" cat back. This may require flange fabrication and pipe cutting utilizing slip fittings for mid pipe sections, but I think this exhaust will make the most power of all.

4-BNGR

 

The testing of these theories is done. DONE. The 3" made more power and more torque. The numbers were close though at this low power level of 316 whp. As the HP rises the gains from the 3" downpipe would be increased even more.

Above you wrote: "SO a 2.5"DP will retain hotter exhaust gasses (at lower rpm) than a 3", thus they will reach the turbo slightly ahead of the 3" DP. (Torque)."

You better read what you wrote and I hope you didn't actually mean it. The downpipe would have to be BEFORE the turbo for what you wrote to even apply. The downpipe is AFTER the turbo. Maybe that is why you keep posting the theory of the 2.5" downpipe making more low end torque all the time. In a Subaru they have an UPPIPE that is before the turbo, in the case of that though it also makes more HP increasing it's size.

David Buschur
www.buschurracing.com