View Full Version : Glad they got rid of the SIR...

10-26-2010, 01:42 AM
Ok, so now there's the displacement vs weight, but what about the oe manifold requirement? That doesn't limit certain motors that might have more displacement, but with a crappier intake manifold.

Greg Amy
10-26-2010, 07:01 AM
That's the limiting factor on my GSR engine (B18C1). The factory manifold and t-body are really what differentiates this engine from its banned brother the B18C5 (Type R).

Even with cams you won't get much. Skunk makes a $250 bolt-on manifold that reportedly adds 5-10% to the top end (assuming you have the cams).

I think it's an OK idea. From a prep perspective I'd like to run an intake, but from a rules perspective it makes things a bit more predictable.


10-26-2010, 12:15 PM
Won't a IM allowance blur the difference between a B18C1 and a B18C5? :)

Greg Amy
10-26-2010, 12:19 PM
Won't a IM allowance blur the difference between a B18C1 and a B18C5? :)
Of course! It wouldn't just blur it, it would destroy it*. That's why I'm OK we have this rules restriction...


* The B18C5 cam has more lift than the STL limit, more compression than the C1, and it's already ported and polished from the factory...a built B18C1 with open intake would be making on-par power with the C5...but given the stock manifold it could never match the C5 with common rules.

10-26-2010, 12:33 PM
^^ agreed....

Highlights of B18C Spec R compared to standard B18C GSR

1. Camshaft - Wide-angled, high-lift, high-durability camshaft *
2. Exhaust Valve Spring - High-lift, dual-layered spring *
3. Spark plug - High-heat-type #7 platinum plug *
4. Engine Stiffener - Aluminum die-cast, high-durability, one-piece type *
5. Crankshaft - Full-counterweight, 8-weight, high-output, custom crankshaft
6. Connecting Rod - Custom TypeR rod, high-durability, lightened *
7. Pistons - High-compression, low-friction, custom pistons *
8. Inlet Valves - Lightened inlet valves
9. Intake Manifold - Custom tuning, single-port type. #
10. Throttle Body - 62 mm (2.4 in) wide-mouth throttle body. #
11. Inlet Valve Springs - High-lift, flat-surfaced, dual-layered spring *
12. Port Buffing done by hand
13. Fastening of Connecting Rod done with micrometer.
14. 98spec engine has stainless steel 4-1 exhaust manifold *

* - irrelevant considering current STL rules
# - irrelevant if IM/TB allowance existed

So....crank, lighter valves, "hand" port buffing... that's significant.

10-26-2010, 10:47 PM
What fastrack are the STL rules laid out in? - nevermind. Found it.

So the VW / Audi 1.8t engine is an option.
I see that you must retain the original cylinder head and intake manifold when swapping motors. Can you pull the stock manifold and place a 4->1 header and run it without the turbo? I mean the turbo is part of the exaust no?

I guess cam lift would then be limited to the 4v spec?