Nissan L engine exhaust

=Cast Exhaust Manifolds=

The majority of street driven L powered dimes utilize a cast iron exhaust manifold as fitted from the the factory or taken from other OEM Nissan/Datsun applications. Some factory manfiolds come with provisions for air injection and/or EGR fittings, in practice they appear to flow similarly to those without these provisions. The air injection ports on manifolds equipped with them are located along the upward facing surface of the runners, they are threaded BPT (British Pipe Thread and can easily be blocked up with a pipe plug of the apropraite size and thread pitch. There are two main types of factory supplied cast exhaust manifolds for the L-Series nissan engines fitted to the 510.

4 into 1
This design is uses 4 runners from the exhaust flange which then all dump together before joining to a Y-Pipe which seperates the exhaust stream back into two pipes before rejoining them where the Y-Pipe meets the exhaust system under the car. This type of manifold was commonly where a heat sheild would be mounted. This method identification may prove less than accurate though as many people have reported that manifolds sourced from Dastun pickup trucks such as the 720 or 520 may have the distinctive ridges even though they are actually Tri-Y manifolds when inspected more closely.

This design is less than optimal for performance applications as it provides little scavenging effect and may promote exhaust pulse reversion.

Tri-Y or 4-2-1
The Tri-Y design is the most common cast manifold used in performance applications. It is characterized by 4 runners which run from the exhaust port flange which then transitions to two seperate runners at the Y-Pipe flange. This design is far superior to the 4 into 1 design as it promotes higher exhaust gas velocity and utilizes exhaust pulse matching for it's excellent cylinder scavenging and anti-reversion effects. This type of manifold is often preffered over a tubular header for most non-race 510s as it is cheap, flows well, is quieter and more robust than most tubular headers.

Y-Pipe
The Y-pipe runs from the outlet flange of the exhaust manifold to the begining of the exhaust pipe, it consists of two tubular runners which join at the exit. Many people have found that by extending the tubes of the Y-pipe so that it joins after the transmission crossmember low and midrange power can be increased. The size of the tubing used in a factory 510 Y-pipe is 1 5/8", this is an uncommon size for exhaust piping which has led some to instead use electrical conduit for extending the tubes. Others have used sections from a 280zx Y-pipe to extend the factory 510 part, however the 280zx pipe utilizes a 1 3/4" cross-section which may reduce slightly exhaust velocity. On the upside though, the 280zx pipe also utilizes a 2" outlet which is a good step towards upgrading the factory exhaust to a larger size.

=Tubular Headers= The majority of L powered 510s opt not to use a tubular header because they are often loud, they increase underhood temperature, are expensive, and only provide a usuable increase in top end power or with on very large displacement engines. There are no commonly available L-series headers which are of a tri-y design. Stahl and Datsun Comp both make a quality header which is commonly used on ITC race cars, though often with a tri-y collector added in place of the normal 4 into 1 collector. Furthermore, tubular headers do not use a factory Y-pipe type design and as such different parts may be neccessary depending on the block height of the engine; L16 blocks being 3/4" shorther than L20 and 1 1/2" shorter than a Z24 blocks. Failure to use a header of an appropriate length may cause interference with the steering box, firewall, or floor.

=Exhaust Pipe= The factory exhaust pipe on all 510s is 1 7/8" from the Y-pipe to the tail pipe with a single muffler. Common exhaust upgrades include going large tubing in the 2" to 2 1/2" range for street driven cars, another common upgrade is adding a second "resonator" muffler ahead of the factory muffler location to deaden cockpit noise. Exhaust pipe diameter is limited by the hole in the rear suspension crossmember that the pipe has to pass through, some people have had success cutting out the opening to a larger size and welding in a section of larger metal tubing to help reinforce the hole.