Anyone ever get hard numbers on 260z SU intake vs. 240?

[Guest bastaad525]

most of us have probably heard the 'rumor' that the N36 intake produces around 10 extra hp over the stock 240z intakes... just wondering if anyone ever tested this? I find it kinda hard to believe and don't want to waste money, but if it's known to be a fact I would take the time to track down a set of these

[Lockjaw]

There was mention of that on the Z therapy video too. I have both sets. Would like to know myself.

[johnc]

Although I don't have any hard numbers, I witnessed most of a series of chassis dyno tests spanning about 5 days the looked at a number of changes for ITS L24 engines. Again, these tests were conducted to determine horsepower and torque gains for engines built to SCCA's restrictive Improved Touring rules. The rules essentially dictate the following for our discussion:

 

1. No internal engine changes from stock (stock cam, valves, ports, pistons, etc.).

2. Stock, unmodified (except for port matching 1" in) intake manifolds.

3. Stock, unmodified (except for needles and jets) SU carbs.

4. Unrestricted headers and exhaust.

 

Within those limits it was found that the N36 manifold was marginally better then the others that were legal for IT. The 10hp number is an exaggeration. Small ignition timing changes to the engine produced more horsepower then the manifold swap.

 

There was also some arguement that the N36 manifold was illegal in ITS on a 240Z so the engine in question ran E88 manifolds - and won the divisional and regional championships 3 years in a row.

[Guest bastaad525]

So probably not worth the $100+ and trouble of doing a swap hm?

[Z-Gad]

$100 !!

I'll sell you a set for $25 + shipping

mike

[katman]

The 10hp number, like most of Rebello's (where the rumour started) hp claims, is exaggerated. On an actual engine dyno in back to back tests for an ITS L24 (as previously described by John C.) the N36 makes no more than 2hp in some parts of the rev band, less than a E88 in others. On a modified engine of some sort I'd be surprised if it ever amounted to more than twice that.

 

In Dynamation simulations at Sunbelt, and what a few years of dyno testing ITS motors has showed us, the short manifold on carburetted L series motors really limits the gains that can be made on either side of the cylinder (exhaust header and intake manifold). Injected motors, depending on the plenum, usually have longer runners and are more successful at intake/exhaust tract tuning, IMHO.

[johnc]

Many times racers will spend hundreds of hours trying to find another 5 horsepower. This seemingly irrational behavior is driven by the requirements of a restrictive ruleset and the advantages that even small gains provide on a racetrack. What I find funny is that a lot of the things racers determine filter out as rumors of some kind of secret "trick" that street racers absolutely need to go fast.

 

There are really no rules when building a street engine. Take the time and figure out why racers are hunting junkyards for some elusive intake manifold, rare cylinder head, "special" camshaft, etc. You'll probably realize that you can accomplish more with less time, effort, and dollars because you don't have to fight some obscure rule about "stock" parts.

[Guest bastaad525]

I hear ya Johnc... that's why I never believe that kind of hype unless someone can back it up with numbers or other important data.

[Guest Anonymous]

I have a set of Scott Bruning's 240 SU's and if he claims the 260 manifold is better than the 240 I'll take his word as gospel. I have yet to come across anyone that builds a better set of SU's than ZTherapy, the guy really knows his stuff.