BDC

Yep. First time to use them. Engine has about 160 miles on it as of now and they seem to be seating somewhat.



B

crispeed

The closing timing of the bridge port can be a lot higher/later for one.!

The closing timing should be very close to that of the main/street port.

GMON

I would think there could be some bennifits to the way he has it. First one that comes to mind would be less total voulume during overlap....???? I dont know if theres anything to that idea but would think that it would make it more streetable.



However, it is on a secondary and may not have that much effect. Just a thought I had.....Anyone????



Gregory

93 R1

Meaning the bridge would extend further towards the bigger side of the port ?

BDC

He means the eyebrow cut would be taller and it would end at the same 'elevation' as the main extend port, i.e. when the edge of the rotor swoops up over it to close the intake port, the bridgeport's intake port would close at the same time the main extend port does.



I'm not sure of the reasoning behind why he said this, though.



B

93 R1

yeah I understand that, but would it go towards the top of the port more or the bottom of the port...If looking at the plate bolted to the motor.



I just don't know the whole port timing thing thats all. My guess is that it needs to go further down to make it close later......

BDC

It's the opposite --



Imagine looking at the front iron housing, viewing the combustion chamber side, where the intake port outlet is on the top right corner. Placing a rotor on this, the rotor would rotate counter-clockwise. Now, imagine that rotor being at TDC (where two apexes are facing "northwest" and "southwest" respectively, where one rotor face is flat against where the spark plugs are, as well as the third apex facing "east" inbetween the exhaust and intake ports) -- In this case, the exhaust and intake ports are separated. Rotating the rotor counter-clockwise will move the apex of the rotor up to and then over the intake port. The degrees (in reference to TDC) when the rotor continues to rotate and then expose/uncover the intake port is called its "opening timing". As the rotor continues to rotate, and when the next apex rolls around and fully closes it (the closing point being the highest, tallest point of the intake port outlet that's lastly exposed), the port "closes", or "closing timing". The same rules apply when measuring the port opening and closing timing of the exhaust port as well.



The term "overlap" is used when both the intake and exhaust ports are open at the same time for any length duration. Because of the physical placement of a bridgeport (where the eyebrow or larger bridgeport cut is made inbetween the main extend port and the inner water jacket o-ring land), when the rotor is at BDC (heh, don't make fun of my name; it actually means Bottom Dead Centre where a rotor apex is facing "west" with the other two respectively facing "northeast" and "southeast"), the intake port open much earlier. During overlap, both scavenging (intake shooting directly into exhaust) and reversion (exhaust via back-pressure being pushed into the intake, diluting the charge) occur.



I'll try and get some pictures taken to show you what I mean. It's real easy.



This help any?



B

93 R1

yeah...kickass man. Thanks alot. I think some pics would be great for reference, and to help others understand too.

87GTR

Well 240 miles on the car now and smoking is all gone but trace. The car is still really rich. BDC upped the map like 12% over the old map until we can tune the car.



I have noticed that with the large parts the car is starting to make boost faster. I have been hittin 2 - 4 psi under normal driving where

BigTurbo74

i find it a lot easier to understand some explainations like bdc just posted after i have seen the actual seperate components of the engine and where things are located such as ports ect... anyway pretty ports. good job