Raising the Bar

Cat-Back exhaust arrived from [no name] and front sway bar from Perrin for the STi. The exhaust looked great out of the box and weighed 23 lb compared to the stock 32.

The good looks didn't make up for poor fit as the downpipe flange was deep enough to swallow the stock gasket. Note how the stock flange leaves a sealing surface protruding while the deep flange on the new unit is actually under-flush.

Below illustrates the joint's function when installed, showing the inadequacy of the recessed gasket when using the new system.

Communication with the vendor is pending, but considering the price a less than helpful response is likely. In that circumstance there are a few options for fitting the new system including:

1. Find a gasket with the same ID and a bigger tapered section to fill out the new flange.
2. Construct shims to sit behind the gasket to allow it to sit deeper in the flange.
3. Procure or manufacture a proper mating flange and cut-weld into the new system.

The sway bar install went smoothly. The new bar is 25mm, 2-position adjustable upgraded from the stock 20mm non-adjustable. Stock end links retained.

Test drive indicates more responsive steering but a retained propensity to oversteer on power.

It was also an opportunity to check out the new camera.

Exhausting

Exhaust fabrication for S13 240sx. The goal was reduced weight and power increase. The single glasspack muffler was selected for weight and flow, not sound deadening, though sound requirements at the track will need to be met. The system is similar to that used in the 'spec e30' exhaust http://grassrootsmotorsports.com/project-cars/1989-bmw-325is/spec-exhaust-excitement/

Parts from Jegs. Good price and quick shipping a plus, but they make you fill out account information in order to get a shipping quote, which in most circumstances is enough to steer me away from a retailer altogether, but supply was scarce and my demand was high. 2 5-foot sections and 2 u-bends. One of each would have sufficed.

Tubing is 2" mild steel 16 gage. Muffler is a simple glasspack. The 180 is a 6" radius.

The previous owner had tha cat replaced and the shop welded in a universal, so there was no joint after the cat to unbolt. Three flanges were machined to match an off-the-shelf gasket from a chevy. The flanges were 3/16 cold rolled steel.


The flanges welded in behind the cat on the stock system. The header-cat piece was deemed too risky to remove with lots of threaded smog-control lines attached and rusting in place for the last 15 years of high heat duty. That meant welding the cat-side flange underneath the car. This was tricky and the weld was not beautiful, but no leaks resulted. Having a flange gave a starting point for the fabrication of the cat-back.

Cutting and fitting was guess and check, tubes were tacked in place under the car and the glasspack was left to float in place until the tailpipe could be located under the old exhaust cutout.

Post-cat section, glasspack and tailpipe compared to stock system.

Tack welds after fitting.

With the tailpipe in place the mufler was tacked under the car and hangers were bent and tacked as well. Hangers made from 1/4" weldable steel rod.

After a final test fit the whole system was welded, hangers were drilled for cotter pins.

The paint was wire-brushed from the glasspack and the welds were brushed prior to a light coat of VHT high temp header paint.

The stock system weighed 30.6 lb while the new one came in at 12.4.

The termination still needs to be sorted out, either with a cut to match the bumper or a tip of some sort.

The sound is not great, but the final verdict will come from the sound meter at Qualcomm.

Post Test-Drive Update:
The sound has been upgraded from 'not great' to 'okay'. Nice deep thrum at idle, light throttle is throaty and low but at load it starts to get loud. Above 4K it's all rice-rasp.