16v ITB's, hard brakes

[meadan]

Ok, well Ive finally driven my recently 16v converted ae86. It all runs sweet, except that the brakes feel unusually hard.
They seem to stop ok, but just require more pressure.

I have swapped from a 4age 20v with open trumpets to a 16v with the same itbs and trumpets on it.
The only thing I have changed is that now I have an aluminium manifold hooked up to the stock 20v vacuum ports, which then connects to the map sensor and the brake master.
The vacuum ports from the T3 manifold join together and connect to the FPR.

Also, the 16v has ~290 degree cams, would this affect the vacuum at low revs causing the brake to be hard?

[Stain]

If by "aluminum manifold" you mean a vacuum chamber... and if you're feeding that from the vac ports on the throttle bodies themselves that won't work very well.
Most of the vac ports on the throttle bodies are before the butterfly, not after it. To get a true vac source (certainly strong enough) for the brake booster you need to
use the ports on the T3 manifold (as they are after the butterflies) to feed the vacuum camber - which you can then use for the booster, map and fpr.

[meadan]

Yes a vacuum chamber, had a bit of a brain fart when I wrote that :P

Im using the vac ports which were at the bottom of the throttle bodies on the 20v. These were connected to the microtech map sensor on the previous setup. Now the microtech may be tuned off tps which would explain why it made no difference to the old engine, I will put the map sensor back onto them and use the T3 ports for the brake master and FPR. Ill see tomorrow if that makes a difference.

Here is a pic to show how it is setup...


http://www.ae86drivingclub.com.au/dcimages/9/4/7/231806.jpg

[sundee]

will make a difference having the vacuum source from the engine side of the throttle butterflies. This is where the vacuum source should always be taken from
also your 290' cams will give you less vacuum, but not to adversely affect your brakes that much.

[meadan]

Well I assume they are 290 degrees anyway, unfortunately got no spec sheets when I bought them, so getting the cams done properly is the enxt fun job.

But yeah, I just assumed that the stock vacuum ports were connected after the throttle bodies, so hopefully swapping them over fixes it. Ill keep the map sensor hooked up to them though, I doubt its tuned off the MAP sensor now seeing it wouldnt be getting a good reading anyway.

[TODA AU]

Stain & Sundee are right... It looks like you're running ported vacuum signals off the throttles near the blade to your vac block,
I'd be picking up the vac sources from each runner inboard of the throttles.

[meadan]

OK swapped it all over this morning. Seems to work heaps better :)

Relocating the vacuum chamber also neatened it all up a bit so you cant see the lines running everywhere now.

I also played a little bit with the cams, I retarded the inlet cam 2 degrees and it pulls nice and hard from 4500 on now. Ill leave the rest till it gets on a dyno.