OK, I will admit it: I am going to install stacked pulleys.

The car runs great with the Karmen 62mm. I run 12.3-12.4 with ice, and 12.5-12.7 without. I really want to run in the 11s. I could probably sneak in an 11.99 timeslip with a good tune, but I want to consistently run in the 11s, which is going to take more.

I have read all the threads where others have installed or tried stacked pulleys. The hurdles others have encountered with stacked pulleys seem to be:

• overboost codes (22+ psi)
• lean AFRs
• high intake air temps

Overboost codes:
I am not concerned. I ran 14 psi with the stock pullies, and now run 18 psi with the 62mm. I expect to see 20 psi with stacked 178/65 pulleys. Others have seen higher boost than me. Maybe my full exhaust reduces the pressure. Maybe my supercharger lobes aren't as tight. I don't know.

Lean AFR
I am upgrading the fuel system, again. The final system will be:

• Walbro 255 L/Hr pump
• 8AN check valve
• 8AN line to rail
• "Ultimate Fuel Rail": 168% larger inlet, dual outlets
• Adjustable FPR
• Fuel pressure controlled AFTER the rail rather than before

I am trying to decide whether I even need larger injectors. With the stock system, the fuel pressure is regulated in back by the pump. With all the lines and the tiny restriction at the fuel rail inlet, the actual pressure in the rail could be dramatically lower than the 56 psi setpoint. My new rail has dual 8AN outlets than run to the dual inlets on the adjustable fuel pressure regulator in the engine bay. It will better maintain the desired pressure in the rail, and I can adjust it up for more fuel if needed. I would love to hear opinions on whether I will likely need larger injectors or not.

Intake Air Temp:
I have this under control. Intercooling now is:

• separated cooling systems
• OEM IC, insulated
• Dual OEM heat exchangers, in parallel
• Johnson CM30 pump
• 7 gallon resevoir/ice tank in trunk
• ANOTHER CM30 pump in the rear

With the 62mm pulley and the above cooling upgrades the IAT runs between 105 F and 145 F. Subtract 50 degrees if I am running ice. There will be more heat to remove with stacked pulleys, but it will still be managable.

 

If all you want is that elusive 11.9 then stack them with 100 octane in the tank. My best with a 178 crank pulley is 12.01. My best with a 178 stacked with a 65mm pulley is 11.992. And that was icing the intake and an ambient temperature of 78º so I can't give the credit to the double pulleys. Running stacked, well the power increase in the lower and midrange is noticeable but at the top it slacks off. The over boost code is easy to clear. I have the SL55 Pierburg and saw 13 AFR's at the top of 3rd. down from 14's with the stock pump. It's not sensible for a daily driver but for a night at the track, why not. As I already mentioned, put 100 or 104 in the tank and have fun …. or you could be sorry. The difference between stacked and just a 178 is .01.

Les

Les

 

I don't remember anyone trying a fuel delivery/return system like you are building. I think it would be beneficial to all if you would be able to get afr's on that fuel system with OEM injectors.


How close are you to installing it?


Would you mind listing the mods you have again?

 

Pretty close. I will get the car out of storage and install everything within the next few weeks.

I don't mind sharing at all:

The fuel system and intercooling mods are listed above. Also:

Custom 3" exhaust, version 4

• Magnaflow 3" glasspack muffler & resonator
• flowmaster scavenger series 2-into-1 Y-pipe
• oem headers...
• not so many cats. not many at all in fact

Custom dual 3" intake

• Big K&N filters
• E55 y-pipe
• custom tubes, full 3" throughout

• Wavetrac
• Mike R rear camber arms
• Mickey Thompson ET Street radials
• Innovate OT-2 & LC-1 (datalogging & WBO2)

 

Thank you, so no tune on the ECU or TCU right?

 

While I admire your ingenuity, that fuel rail may be overkill. Robs Adjustable regulator with a second gauge at the end of the fuel rail will give the same information and if it provides enough fuel for good A/F ratios, then anything more is wasted effort. If you were shooting for 600 HP, maybe, but that isn't attainable here.

 

Correct. Not tuned yet. I wanted to get the hardware finalized before getting it tuned.

 

Your proving something I wouldn't touch. How much it can take without blowing up! Please be careful with the 62, no tune and racing. When I got my first tune I didn't know what a good/bad one looked like. I look back on all the retunes as home schooling.

Les

 

Thanks.

I installed the AFPR, Walbro pump, 6AN lines, & FP gauge before installing the 62mm pulley. I did get the pump and gauge adapter fittings from Rob. I got everything else for free from my drag racing sponsors. I wanted to be very certain that I would not run lean with the 62mm.

Now I am being just as cautious about running lean before going stacked. You may be right; it may be overkill. In this round I am upsizing the fuel supply line from 6AN to 8AN, installing the "ultimate fuel rail", and moving the regulator to after the rail.

These upgrades will guarantee enough fuel TO the rail, eliminate the restriction at the rail inlet, and more consistently control fuel pressure.

 

If you datalog the fuel pressure after all of your upgrades then it would paint a better picture for the need of injectors. If the injectors don't have fuel pressure and the volume then it doesn't matter how big they are. I think your fuel rail would eliminate any potential variables in the fuel delivery system.

 

Aftermarket tunes are typically more aggressive than OEM, not more conservative. I AM datalogging my runs with an ODB II scanner and a wide band O2, which is a point I should have included earlier. AFRs are safe, IATs are safe, and timing advance is less than I hear others on here discussing.

 

I wish I had a way to datalog fuel pressure. :/

 

So, what are the AFR numbers? And the timing?

 

I'm curious too. My AFR's are low 12's, my timing is, not telling, you go first.

Les

 

Here is my most recent log snipped from a hard highway run out of a gas station.
Maybe not as relevant since this is from a C32 but it's a data point. I run OEM C32 fuel pump, looped fuel rail with 6AN fittings, 550cc injectors, 164mm crank pulley and 65mm SC pulley, NW 3" dual air intake and a 80mm TB. The interesting part is the readings for the fuel pressure and the injector duty cycle. I tried the 164mm with the 62mm pulley but would "run into the wall" on occasion, and therefore downgraded to the 65mm SC pulley.

 

Oh my goodness! What's up with the EGT's? Or maybe it's where your measuring them? I rarely surpass 1400 and 1375 is usual for me. And the AFR's? And, and, and ….

Les

 

short q to the masters,

I have this setup (not stacked)

64.7 mm sc pulley
DCAI
sl 55 pierburg pump

and am about to make following changes:

61 mm sc pulley
550 ttm injectors
looped fuelrail

any objections? It is equivalent to a 186 cp right?

 

I hear you. This is work in progress. This was recorded on a very cold day of Jan. 15th. I need to see what AFRs would be on a more normal day in a few months. Way too much snow on the ground now. I measure EGTs from one of the runners on the Kleemann header, the closes place to the engine.
There were two points behind posting this log. 1. Show the value of data logging 2. Show the relationship between AFRs, 550cc injector duty cycle and the fuel pressure while using OEM looped fuel rail.

 

Your lean which is why the EGT's are so high. I don't see any spikes in the EGT's that are caused by detonation so that's a good thing. About your tune ... I ask because of the 16º of timing. With a tune I'd see 19º until the IAT's or ECT's got hot. My current race tune is 23º +o-. My EGT's, as I mentioned, rarely surpass 1400º even when I had a leaner tune. Hum.

Les

 

06052013log_zps4e60e42e.jpg

Here is a datalog of a 1/4 mile pass from me [finally]. This is a pretty typical run. You will have to zoom in to see the readings. The vertical line to the left of each readings box shows you where on the graphs it is reporting. The shape of the AFR curve is very typical. Fuel pressure is 59 psi. It always has that dip in AFR between 5800 and 6100 RPM.

The 35 degree F rise in IAT during the course of the 1/4 mile run is also very typical. If I start the run at a lower IAT, it will end at a lower IAT. But the temp rise is fairly consistent.

I don't have timing advance on this one, but the OEM timing curve is a disaster. The advance is all over the place, and is not consistent from run to run.