Polishing Rotors - Pros and Cons

NoDOHC · 07-10-2009, 11:16 PM

Update:

Sorry to resurrect this thread, but I have 4400 miles of driving to discuss.

Short story, Brent is 100% correct. The engine does not like high vacuums at lean mixtures at all. I have to run about 12:1 at idle to make it run. My fuel economy is down too (38 mpg instantaneous at 70 to 34 mpg instantaneous at 70, about 29 mpg on a tank). Most of the loss of economy is the fact that at cruising vacuums (~50kPA) I can't go lean of stoic (I was running 16:1 AFR before).

Long story: Too many other factors involved to discuss power (4-port vs. 6-port, bored-out intake runners, heavily modded UIM, etc.) but the detonation resistance is insane.
The engine will not pre-ignite at all. I have never heard it knock (I am still running NA). I advanced my timing until flooring the gas made the engine deccelerate the car and I still heard no knocking noise (70 degrees BTDC).

After those miles (very few actually, in the grand scheme of things) it pulls 70 kPA of Vacuum at idle, makes 100+ psi on all faces and otherwise appears to be in good condition.

Interrestingly enough, the engine makes more torque at 2,000 rpm than the 6-port before it. (It makes a whole lot more torque at 7500.) All in all, I am very pleased with the 4-port NA (my first). Unfortunately, Idle torque is not very good at all, the torque curve doesn't even start until 1500 rpm.

The car is very hard to drive with a stage 2 clutch, 8lb flywheel and no low end torque.

07-10-2009, 11:16 PM	#26
NoDOHC The quest for more torque Join Date: Sep 2008 Location: Sheboygan, Wisconsin Posts: 855 Rep Power: 17	Update: Sorry to resurrect this thread, but I have 4400 miles of driving to discuss. Short story, Brent is 100% correct. The engine does not like high vacuums at lean mixtures at all. I have to run about 12:1 at idle to make it run. My fuel economy is down too (38 mpg instantaneous at 70 to 34 mpg instantaneous at 70, about 29 mpg on a tank). Most of the loss of economy is the fact that at cruising vacuums (~50kPA) I can't go lean of stoic (I was running 16:1 AFR before). Long story: Too many other factors involved to discuss power (4-port vs. 6-port, bored-out intake runners, heavily modded UIM, etc.) but the detonation resistance is insane. The engine will not pre-ignite at all. I have never heard it knock (I am still running NA). I advanced my timing until flooring the gas made the engine deccelerate the car and I still heard no knocking noise (70 degrees BTDC). After those miles (very few actually, in the grand scheme of things) it pulls 70 kPA of Vacuum at idle, makes 100+ psi on all faces and otherwise appears to be in good condition. Interrestingly enough, the engine makes more torque at 2,000 rpm than the 6-port before it. (It makes a whole lot more torque at 7500.) All in all, I am very pleased with the 4-port NA (my first). Unfortunately, Idle torque is not very good at all, the torque curve doesn't even start until 1500 rpm. The car is very hard to drive with a stage 2 clutch, 8lb flywheel and no low end torque. __________________ 1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers) 1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)