The Exhaust Debate

[ozconnection]

240zman, I think you missed the point of what I was trying to point out here. Many people have claimed that there is little point in adding a performance exhaust to a stock engine. My claim is that this is just not the case.

My original spec L28s (single carb!) engine ran a Hitachi 2 barrel carb from the factory. Rated HP is 139HP at 5200 rpm. This is what Nissan claims for that setup. The figures are also for an automatic trans car where there is about 10% driveline loss over that from an equivalent manual trans car. You do the maths and see what is works out to be.

I can assure you that the engine was running very well at the time of the first dyno run since my father and I had been owning these types of Nissan cars since 1971. Sure, it doesn't make me an expert but at least very familiar as to how these cars should be running.

Naturally, twin su and injected engines are going to make some more power than a stock L28 with a single two barrel.

Cheers,

Mark

[WingZr0]

Back when dirt was new, I installed headers on my '70. They were smogged (couldn't get the other kind then) so I plugged 'em with NPT brass plugs. They're still there. The header was a three-into-two system and I ran dual exhausts out the back, centered, just like the old Jaguar XKE's used to do. Loved the sound. It says "Get ready!"

I've retained the old "mufflers" and installed stackers out the left side. See comparative photos. The sound is still the same, but it now looks better and more complete.

Thats a clean Z Bro

Excellent execution.

Liking the sceanery on the 2nd pic too for sho!

Does the centered exhaust cause any problems with the heat being

to close to the gas tank?

Always wondered bout that and how to pull it off.

The twin stack is the best IMO but I love the slash cut styles.

Did have a Orange ANSA that was similar to yours though.

~http://s170.photobucket.com/albums/u280/Wingzr0/ANSA%20RESONATOR%201970s%20NOS%20%20%20Slash%20Cut%20Twin%20Tip/?start=all

~http://s170.photobucket.com/albums/u280/Wingzr0/Partz%20stuff%202nd/?start=all

~Z~

[xray]

A few years ago I began a series of modifications to my L28S to improve its performance. ...I've included the dyno graph that shows these two mods. ... The other line is the result from changing the exhaust. To say that a performance exhaust is worth very little in extra power on what is, essentially a stock motor, rubbish. ...When it comes time for replacing my exhaust, I'm going to run a similar design on my L28. Mark

snipped, emphasis mine.

Uh, I think the thread is about the exhaust improvements in a stock US-spec L24.

While no one is invalidating your experience with your L28S, or your generalization that an exhaust improvement can increase power in a stock motor (MKIV Supra immediately comes to mind), more than enough anecdotal evidence (and dynosheets, although I have none at the moment to post) exists to support the motion that a performance exhaust in a stock L24 does little to improve its performance.

Steve

[ozconnection]

Steve, I added the dyno sheets to the discussion because I wanted to show people how much potential there was in improving the performance of a

stock l28 engine. I have no personal experience with modifying L24's but how different can they be to what is essentially a fundamental performance upgrade?

If dyno sheets exist for L24's before and after an exhaust upgrade I would love to eat my words!

Cheers,

Mark

[gnosez]

Jim Cook Racing/Sebring Tuning

I have his muffler on my 3.2L L28 w/triples and it sounds dam near like heaven. Jim is an ex-Datsun racer and knows his business, their service is great and the prices are very attractive. When I move up to 3-inch I will get one of his mufflers....

[Arne]

Steve, I added the dyno sheets to the discussion because I wanted to show people how much potential there was in improving the performance of a

stock l28 engine. I have no personal experience with modifying L24's but how different can they be to what is essentially a fundamental performance upgrade?

If dyno sheets exist for L24's before and after an exhaust upgrade I would love to eat my words!

Cheers,

Mark

Mark and all, it's my guess that both opinions are correct, for the situations described. Seems to me that I have seen dyno charts for a SU-equipped L24 with stock and aftermarket exhaust, and the difference was nothing like yours. I suspect that in your engine's case, the stock exhaust was only barely up to handling the two barrel carb. So adding the four barrel alone did little, the exhaust was the bottleneck. It would be interesting to see what the exhaust did with the stock carb. Did your L28 come with a single outlet exhaust manifold?

On the other hand, in the L24 as used in the US 240Z the horsepower bottleneck is not exhaust. Adding a good exhaust alone to an otherwise stock L24 does little. More intake (i.e. triple carbs) is what really wakes up a 240Z.

[ozconnection]

Arne, I hear what you're saying. I can only take your word for it about the "quality" of the standard US spec Z cars you guys have over there. The standard exhaust system on my 280 was of the single outlet variety, so improvements over this was fairly easy to achieve. the pipe diameter was 1 3/4 inch with a small resonator and a large rear muffler. I have owned other Cedrics that had the 'better' dual outlet cast exhaust manifolds with two pipes running along till about the crossmember before they joined back into a single system. When I had this system replaced on another car a long time ago, I found that one of the joining pipes was so badly welded (by the factory I might add since this system was virginal...first time replaced) that three cylinders would have been working a lot harder than the other three to get the exhaust out. As you can see from my own personal experiences with L28's and Cedrics, a good exhaust system is worth its weight in gold in the performance stakes.

Cheers,

Mark

[240Z-Fan]

Great thread!

My 240 is due for a new exhaust system too. While it is mostly stock, (round tops replaced flat tops), I want a deeper throatier exhaust. I would love to find a good system that doesn't sound obnoxious or boy racer.

...

I did want to add that many years ago; my stock 78 280z needed a new front pipe. I bought and installed one from the local car parts places. As soon as i pulled onto the road I knew something was wrong. It was significantly down on power.

I drove it for a couple weeks trying to figure out what it could be. Eventually I pulled the pipe back out and took a close look inside. It turns out the aftermarket pipe was built in such a way it had a significant restriction. The flange that mates with the manifold had two pipes that collect onto one pipe. The way it was constructed resulted in about a 1.25-1.5 inch orifice.

I then went from parts place to parts place and they all had the same construction (probably the same manufacturer). I finally decided to spring for a new Nissan part.

Boy what a difference! The construction was clearly superior, and more importantly, the power was back!

While this doesn't directly apply to higher performance exhaust systems, keep this in mind when shopping for aftermarket 'stock' parts.

Al

[kelman81]

I put the previously mentioned 3-2 double coat header with MSA Dynomax turbo muffler exhaust and was happy with the sound, although louder than what I had hoped for. Replaced the kit msa exhaust with a new pipe for closer bends and a smaller turbo style muffler (maybe 3/4 the size of the MSA Dynomax supplied). Now the car sounds almost raunchy and has crossed the borderline of too loud for me.

Couldn't be happier with the MSA header, very unhappy with the fit and look of the MSA turbo muffler exhaust system although it sounded good, and now the new exhaust system looks and fits better with the smaller muffler and custom bent pipe, but it's too loud and unrefined for my taste. (I tried posting a low res picture of it the other day, but website was slow, will post soon).

[nhoddino]

I had a real problem with the Flowmaster series 40 resonating around 55 to 65 mph (guessing 95 to 115 KMH for those of you on the metric system) so I changed it to a turbo style muffler. It was cheaper sounded fine and didn't resonate so loud in and under the the car. I like it just fine.

[ozconnection]

Here's my exhaust.

[Weasel73240Z]

I had my new exhaust installed last week. I ended up going with a Magnaflow muffler (#14829 I think), and plumbed it in with 2-1/4" all the way from the header back.

The sound is awesome, but the fumes have gotten a bit worse with the new exhaust. :mad: The new muffler is slightly shorter than the original was (i.e. it doesn't stick out much beyond the bumper), so I'm guessing that may be the problem. I guess I'll try screwing around with some tip extenders to try and reduce the fumes again.