This thread is turning wierd. I think Fly was correct above, there is no dispute regarding terminology.

Engine braking occurs whenever you get off the throttle, remain in gear and allow the engine's load work to slow down the car.

Downshifting occurs when you depress the clutch, change from a higher gear to a lower gear and release the clutch. There will be a dip in revs when the clutch is depressed and the revs will increase to a higher rpm after the clutch is engaged.

By downshifting to a lower gear, the process of the revs dipping down and going back up to a higher rpm has the effect of slowing down the vehicle. Additionally, the car is further slowed as the revs drop. By downshifting from 5th to 4th to 3rd to 2nd and even into 1st, you can slow the stock car from 60 mph to 5 mph without using brakes in a relatively short distance.

What I'm experience with the UR lightweight pulley & JWT lightweight flywheel combination is virtually no engine braking. There is very little braking just by downshifting to a lower gear. And, when in gear, the needle doesn't seem to drop revs, rather it stays put for quite sometime at a constant rpm. Engaging the clutch drops the revs very quickly but that's not the effect I'm concerned with.

Where I find this to be very unhelpful is when you're using the gears to slow the car down in the twisties instead of having to rely upon brakes. At high speeds, downshifting prior to the turn is my favorite way to slow the car down. That effect is now, gone.

Chris, UR pulley and plenum having the same effect to me is just plain weird. The pulley or flywheel would affect the engine braking due to it's link to the drivetrain but, plenum? That's whacky.

 

What I really like with the two mods is being able to blip the gas pedal and have the revs jump up quickly to rev match and make a smooth downshift.

I think there is less engine braking witht the two mods, I wouldn't go as far as saying that there is no engine braking.

 

Physics people? I have a degree in Physics... does that count? The physics is not really what is complex here. Letting off the gas with a lighter flywheel should result in greater engine braking than with a heavier flywheel. However, I believe (based on the information provided in the link I posted above) that we're dealing with the ECU not handling the reduced rotational load correctly. Check out that link. Adanande's post is a bit hard to read, but it makes sense.

 

HFM,

What is occurring in that situation, is when you down shift, the engine with the light weight components, revs back up faster and higher than an engine with the stock flywheel/pulley. Therefore you are getting less effect from each down shift. Because the drive by wire system is not responding to the lifting off the throttle as quickly as it should, it is holding your RPMs from dropping back down longer.

 

I have to agree with what hfm says. Althought I don't have a lightened flywheel, my combo of U/R Pulleys and KINETIX plenum ans dramatically decreased the way the engine slows down when you simply take your foot off the gas. I'm not talking about engaging the clutch or anything, just removing your foot from the accellerator pedal. The car just keeps on going... and going.... and going.... and going some more until you hit the brakes. I guess I'm not really complaining about it at all... just stating the facts in my situation.

-Chris

 

Talk about a thread back from the dead, this must be the new record...haha

Anyway, here are my findings: I've noticed similar behaviour as ChrisMCagle. After doing the plenum spacer and UR pulley, when I let off the throttle, my car also just keeps going, and going, and a couple times I even got a little BOOST. WTF?

This has only happened the last two days, and I've had the pulley on about a week. Makes me think it's definitley something with the ECU.

I saw the other thread this one spawned off, and it turned out to be a dead end. Conclusion was "that's just how it is". Well sorry but I think that's a load of crap, my car should not be surging after I let off the gas!

Is there any updated info on this issue? Is this fixed with reprogram?