2007 Spec B 467/454 stock location GTX3576r

[BrandonspecB]

Why not just resonator or another high flow muffler after the dp ?

 

I've tried that with previous setups. I had a Magnaflow catback that was way too droney. I tried a 3" resonator in the mid pipe and it helped a bit. The only way to get it liveable was by welding the stock resonator in and using the Magnaflow y and mufflers. The stock resonator wouldn't flow enough for what I need now.

 

Then I tried an Invidia and it was just too loud. It even has a resonator in it from the factory.

 

I'd like to figure something out because speed density is the way to go at this point. But, I already spent a bunch of money experimenting with the rotated setup and I don't feel like spending a bunch more trying to solve my exhaust dilemma. At least not yet.

 

I too have bought and sold my share of catbacks for this car. Why can't you run SD with the cutout?

 

It changes the volumetric efficiency of the engine.

 

MAF sensors measure airflow directly. Any change in VE from higher flowing parts is automatically picked up by the additional air molecules bouncing off the sensor element. The ECU then adds the appropriate amount of fuel to obtain the target air/fuel ratio.

 

Speed density uses a calculation to figure out the amount of air going in to the engine. The tuner goes in and fills out an enormous VE table that tells the ECU how efficient the engine is at different MAP and RPM cells. If you change a part that changes the efficiency of the engine you have to go into the VE table and practically retune the entire thing.

 

So, if I tune the car with the cutout open, then go WOT with it closed it will run really rich. If I tune it with it closed, then go WOT with it open it will be really lean. Right now with a MAF I can go WOT anytime and end up with the same AFR.

[Th3Franz]

I think you are exaggerating the effect on VE the cutout will have from a tuning standpoint. Yes, it will reduce backpressure, but more than a 5% VE change? I just can't see its impact being that great. If you have data to prove otherwise, I'd love to see it. Does your manifold pressure change accordingly also?

[BrandonspecB]

I think you are exaggerating the effect on VE the cutout will have from a tuning standpoint. Yes, it will reduce backpressure, but more than a 5% VE change? I just can't see its impact being that great. If you have data to prove otherwise, I'd love to see it. Does your manifold pressure change accordingly also?

 

Here's a graph comparing cutout open vs cutout closed with my 20g. Same gear, same road, same day.

 

Here's an excerpt from Greg Banish's book Engine Management: Advanced Tuning about cutouts. Here are his credentials: http://www.linkedin.com/pub/gregory-banish/4/52a/191

 

"Mass air systems do not typically experience any trouble with these devices as long as they are installed far enough downstream from the HEGO to avoid detecting the fresh air wash. The increased system airflow is simply measured by the MAF sensor, and the PCM reacts normally. Speed density systems will likely experience a more noticeable change in performance. The reduced backpressure raises engine VE when opened. Without any recalibration, the PCM assumes normal operation and delivers what it considers the proper amount of fuel based on MAP and speed. The result can be a lean condition that may lead to knock.

 

I once had a speed density engine that was calibrated on an engine dynamometer using the normal long tube headers open to the dyno exhaust. In this low backpressure configuration, the engine made about 380 hp. This same engine was later installed in the vehicle with a closed exhaust, catalysts, and mufflers. The added backpressure had reduced total flow to the point where the engine ran rich and would not tolerate the same ignition lead. The VE tables required remapping to take as much as 15% out of the WOT values, and timing needed to be retarded because of the added backpressure. The result was a more disappointing 320 hp, but with a safe, emissions friendly tune. To install a cutout on this vehicle would almost certainly allow the engine to breathe at the 380-hp level, but the PCM would not know to add the appropriate fuel to compensate. The moral of the story is: If a cutout is used with speed density, be prepared to recalibrate or risk engine performance and durability."

[Th3Franz]

Is your boost level the same between using cutout and no cutout? I would expect you may see higher boost level with the same amount of wastegate duty cycle, depending on how your turbo dynamics are set up. Looking at your graph, this may be the case since it is during the ramp up until peak where torque the curves are the most different, and then they merge closer together when the integral dynamics kick in.

 

Good book by the way; I am familiar . I believe Greg is referring to a V8, since he is talking about long tube headers and only 380 hp. On a larger displacement NA car, yes I can believe 15% difference in VE between a cutout and no cutout. On a small displacement turbo car, you have the restriction of the turbine itself that is still present, with or without the cutout. So, I think the change in VE would be less. If you are hitting higher MAP with the cutout, you can incorporate that into your VE table as well.

 

I'll also comment that tuning an engine on an engine dyno and expecting the cal to perform the same way on a chassis dyno does not make sense. Having additional drivetrain losses, different loading, and the car's cooling system introduce conditions not seen during the engine dyno tuning. Engine dyno configuration typically offers a limitless supply of cooling.

[BrandonspecB]

Here's the boost graph from the 20g. I use an MBC and that's with no change to it at all.

 

I used speed density with a cutout on the last car I built. The only way to do it is how you describe; lower boost with cutout closed, higher boost with cutout open.

 

I used a switch that ran both the cutout controller and a solenoid in my wastegate vacuum line. With the cutout closed it would run wastegate boost and I could adjust the VE table at the lower MAP accordingly. Flip the switch and it opened the cutout and solenoid resulting in higher boost where I had the higher MAP VE set accordingly.

 

So you're probably thinking, "Why the hell aren't you doing that now?"

 

Number one, the engine management I used allowed for map switching. By grounding a pin in the ECU you could switch between two different timing and fuel maps. I used the switch that controlled the cutout and boost to control the different ECU maps and arm the meth system. So, switch down = low boost, cutout closed, no meth, pump gas timing and fuel maps. Switch up = high boost, meth armed, cutout opened, meth timing and fuel maps.

 

It worked well and was a lot of fun. If I could rig something up like that on my Legacy I'd love to, but, honestly, I haven't researched all my options to go down that road.

[Th3Franz]

Nice, it's pretty awesome to see the boost curves overlaid like that. Makes the improvement from the cutout stand out more. What's the % difference in your MAF readings between using the cutout and no cutout at 5000+ RPM? You can just give the raw g/s #'s if you like.

 

Just a few general questions about your setup: What is your wastegate spring pressure set at? Are you only running an MBC or are you running a parallel boost control setup with an EBCS also?

 

You are hitting substantially higher MAP in the mid RPM range, so you could definitely adjust a SD tune for this range. From 5000 RPM to red line, it looks like on average you are 1 PSI greater with the cutout vs no cutout. How much control do you have over your AFR with your methanol system?

[BrandonspecB]

I don't have a lot of old logs from my 20g, so I can't get the g/s from cutout closed. I just have a handful of graphs leftover.

 

I'll get some logs with cutout closed vs open with the 35r. It might be a few days because we're getting hammered with snow.

 

Wastegate pressure is 21 psi. I'm using only an MBC.

 

I have a bit of control with the meth. The controller injects based on MAF voltage. It starts injecting at about 3.2 volts. Then it increases pressure linearly until full pressure at 4.8 volts. I can adjust the voltages to whatever I like.

[Th3Franz]

Ok cool I look forward to seeing the log comparison with the 35R

 

Are you running any sort of failsafe? With the MBC and high WG spring pressure, you don't really have a way to electronically cut boost..

[BrandonspecB]

Hopes and prayers count as a failsafe, don't they?

[BrandonspecB]

So, I've been looking into Cobb SD and I think they have the solution I need.

 

MAF/SD hybrid mode. This would let me use SD at low loads where a large MAF housing creates problems with drivability, but lets me keep the MAF for high load. I think I'm going to give it a shot.

[TeriyakiBBS]

did you upgrade your FPR to aftermarket or 04-07 STi? or just running the stock FPR? Thanks

[Th3Franz]

So, I've been looking into Cobb SD and I think they have the solution I need.

 

MAF/SD hybrid mode. This would let me use SD at low loads where a large MAF housing creates problems with drivability, but lets me keep the MAF for high load. I think I'm going to give it a shot.

 

Usually Cobb sets it up so that the MAF is used for low end and SD is used for higher loads. Are you sure you can use hybrid mode the other way around?

[BrandonspecB]

Yeah, you can set it up either way.

 

I got an Accesport yesterday and an IAT sensor on the way. Accesstuner Race is really nice software.

 

did you upgrade your FPR to aftermarket or 04-07 STi? or just running the stock FPR? Thanks

 

Stock FPR.

[Th3Franz]

Good to know about the hybrid mode. You have me contemplating a cutout.. lol

Which MAP sensor are you running?

[BrandonspecB]

It's an Omnipower 4-bar.

[BrandonspecB]

Here's the graph comparing cutout closed and open. These pulls were done on a different road than I normally use. No correction factor applied since they only need to be compared to each other.

 

The cutout closed pull was done first. Then I drove around a bit before doing the cutout open pull.

 

Boost is absolute pressure. Subtract 12.5 psi to get gauge pressure.

[Th3Franz]

Nice comparison. Pretty crazy what 2 PSI difference makes with the cutout.

 

Which MBC do you have? Nice, flat boost curve.

[GEE-OTTO]

Wow nice setup those numbers drew me in like a moth to the flame How is it to drive with that much power?

[BrandonspecB]

Nice comparison. Pretty crazy what 2 PSI difference makes with the cutout.

 

Which MBC do you have? Nice, flat boost curve.

 

I use a Hallman Pro. It's simple and works. I've used them for years and have a hard time breaking old habits.

 

Wow nice setup those numbers drew me in like a moth to the flame How is it to drive with that much power?

 

Not too bad. The AWD tames it quite a bit, but you have to make sure the front wheels are straight before the turbo comes in. I took my brother for a ride and got on it in 2nd and he said he could feel the blood rushing out of his head . I can't wait to get it to the track.

 

Had a few things happen over the past few days. The other night I was out practicing my launches and FFS. When I got home, the reservoir was overflowing with coolant. So, I'm thinking I blew a head gasket or the heads are lifting. The car doesn't overheat at all. But if I go out and get on it pretty good, the overflow will be overflowing with coolant.

 

Anyways, I have to pull the heads to check it out and I'm not putting a 123,000 mile engine back in. Plus, I figure if I just replace the head gaskets and put in some ARP studs, what will break next? More than likely a hard part. With that in my mind I'm going to pick up a forged short block and get the heads done up. Might as well build it to reliably handle this power and not have to worry about a massive smoke cloud every time I romp on it.

[BrandonspecB]

Goodies!

[Th3Franz]

details!

[BrandonspecB]

New case

New heat treated crank

K1 connecting rods

Wiseco 8.9:1 pistons

Arp headstuds

Supertech +0.5mm inconel/ss valves

Gsc s2 cams

Bc valve springs

 

I think that's it as far as the major hardware goes.

 

Got it installed and running last night. Hopefully it'll put down some 11 second time slips when the track opens.

[Rester5350]

What is the lift and duration on those cams ? I ask because there is a thread on nasioc discussing failures on the 264 ish, gsc and kelford lobes.

 

http://forums.nasioc.com/forums/showthread.php?t=2510376

[BrandonspecB]

The S2 is a 272 duration cam. The lift is like 10.8 for the intake and 10.4 for the exhaust.

 

I read that thread when I was researching cams. I almost got BC cams because I was afraid of the GSCs failing. But, my builder recommended GSC cams as did another builder when I was doing research.

 

I've got 200 miles so far. Hopefully I won't have any issues.

 

Here's a vid of a how they sound with the cutout open.

 

https://www.youtube.com/watch?v=A6SbFjY4yXI

[BrandonspecB]

Here's a handful of pics of the engine going together.