Hi, Guest
09-16-2005, 04:55 AM
I've done some fairly in-depth testing with the SPI's IMRC motor, or Intake Manifold Runner Control.
What this system does is give you half of your intake volume capacity below 3200 RPMs. Once the engine's revolutions surpass that threshold, the motor activates and turns the butterflies in the secondary intake tracts (or runners) so that the runners are completely open and available.
What does this mean? You get great gas mileage around town, and when you're wheeling and dealing at the track or on the highway, you get the full performance capability of the engine.
"Can I mod my intake manifold so that the secondaries are always open?" Yes, I've just finished doing that mod. "Does it make a difference?" Yes, it does. It allows you to have a much more seamless power delivery experience and a flatter powerband, but at the expense of a decent amount of gas mileage. The engine was never meant to be run in this fashion for any period of time, especially without a performance tune in the ECU. It doesn't run rough, but the gains don't outweigh the detriments and there's no real benefit to doing this unless the car is a dedicated track car.
I'll be modding mine back to the factory configuration this weekend, as the decrease in city/highway mileage is much greater than I anticipated or calculated earlier. I went from 40-42 MPG (approx 6.15L/100KMs) to 32 MPG (7.1L/100KMs).
ICK.
I sure as hell didn't gain 30-40WHP to offset that chunk of range being lost. :angry:
What this system does is give you half of your intake volume capacity below 3200 RPMs. Once the engine's revolutions surpass that threshold, the motor activates and turns the butterflies in the secondary intake tracts (or runners) so that the runners are completely open and available.
What does this mean? You get great gas mileage around town, and when you're wheeling and dealing at the track or on the highway, you get the full performance capability of the engine.
"Can I mod my intake manifold so that the secondaries are always open?" Yes, I've just finished doing that mod. "Does it make a difference?" Yes, it does. It allows you to have a much more seamless power delivery experience and a flatter powerband, but at the expense of a decent amount of gas mileage. The engine was never meant to be run in this fashion for any period of time, especially without a performance tune in the ECU. It doesn't run rough, but the gains don't outweigh the detriments and there's no real benefit to doing this unless the car is a dedicated track car.
I'll be modding mine back to the factory configuration this weekend, as the decrease in city/highway mileage is much greater than I anticipated or calculated earlier. I went from 40-42 MPG (approx 6.15L/100KMs) to 32 MPG (7.1L/100KMs).
ICK.
I sure as hell didn't gain 30-40WHP to offset that chunk of range being lost. :angry:
Daily driver 1: 2007 Jeep Wrangler Unlimited Sport "S"
33" BFG Mud-Terrain KM2s, lots of Rough Country gear - bumper, 2.5" lift, swaybar disconnects, Superwinch 10,000lb winch, Detroit Locker in rear D44 axle, custom exhaust, K+N filtercharger, Superchips-tuned.
Daily driver 2: 2006 Subaru Legacy GT
COBB Stage 1+ package - AccessPort tuner, COBB intake and airbox. Stage 2 coming shortly - COBB 3" AT stainless DP and race cat, custom 3" Magnaflow-based exhaust and Stage 2 COBB tune.
33" BFG Mud-Terrain KM2s, lots of Rough Country gear - bumper, 2.5" lift, swaybar disconnects, Superwinch 10,000lb winch, Detroit Locker in rear D44 axle, custom exhaust, K+N filtercharger, Superchips-tuned.
Daily driver 2: 2006 Subaru Legacy GT
COBB Stage 1+ package - AccessPort tuner, COBB intake and airbox. Stage 2 coming shortly - COBB 3" AT stainless DP and race cat, custom 3" Magnaflow-based exhaust and Stage 2 COBB tune.