20v info

[J_D]

Hey i'm pretty much a noob to hachis and was just wondering the difference between the 20v black top and the silver top is a little more grunt due to the black top's higher compression ratio? is that it?

[Gilly]

little more than that

higher compression

bigger throttle bodies (don't know sizing)
internals are a little different from memory BT rods being not as strong as ST ones?!?!?!

Engine management isthe big difference. ST uses air flow meter whereas BT uses a MAP sensor (manifold absolute pressure) sensor as its load reference. meaning ST needs all incoming air to go through the airflow meter and airbox, where the map equipped BT can run open throttles as the map sensor is after the throttles in the intake manifold itself. you would be wise to run either on aftermarket management anyway.

both are just as tricky to mount in a 86, needing water rerouting kit and converting the ignition system to a DLI box firing ciol packs instead of running the Dizzy bot the above foul the firewall. if you want that stuff or want to know more about it pm slydar on these forums. Kaizen Garage where he works manufacture the parts you may need, also good with the info.

$$$ too silvers are heaps cheaper than blacks and just as good on aftermarket ecu's e.g you see more ST 20v's on aftermarket ECU's than blacktops.

[rthy]

I agree will Gilly except that when you put a silvtop on an aftermarket ECu it will beat a blacktop everytime.

Now more specificly the blacktop Vs silver:

- thinner lighter rods
- 11:1 Vs 10.5:1, acheived by higher pistons
- lighter flywheel
- rumored to have a lighter crank
- different oil pump (to suit tensioner)
- hyraulic belt tensioner
- 1 tooth shorter drive belt
- 0.4mm higher lift on the intake cam + offset 10 degrees
- thought to have different movement on the VVT pulley
- heart shaped throttles Vs round throttles
- shallower but wider opening on the intake ports
- smoother ports Vs rough machining marks
- prominant intake port dividers Vs open casting
- bigger exhaust ports
- wider opening on the intake manifold
- built in secondary mini plenum on intake manifold
- more shrouded shape on the intake spacer
- larger air box
- open combustion chamber Vs shrouded design
- and lastly +$$$$ max takumi tax on the black just for 3 kw

thats all I can think oif off the top of my head

- I want to cc both chambers soon and also find out the differences between valves and shims on both heads.

- Even though the blacktop has only 3kw more I beleive that the head has a higher tuning potential with the shape of its intake ports.


So how do I know all this seemingly irrelevant finner details? well lets just say I am building a hybrid engine that has a silver block and blacktop head. Should be fun.

[J_D]

Cheers for the info guys