Riddle Me This - Exhaust headers

[KBabcock]

I have a question. It seems the best header or at least the most versatile type of header for the X would be a 4-2-1 design yet all the bigger vendors only offer the same 4 into 1 design and they all look like the same design. Is there just a single supplier they all buy from?

 

[Dr.Jeff]

I don't think they all come from the same source. But you are correct, they are basically very similar. Their 4-1 design is best suited for high RPM "race" type applications. I agree, a 4-2-1 design would be ideal for a street car. The old ANSA header was a excellent 4-2-1 design with all of the correct dimensions for a good versatile street application. I have commented several times that it surprises me no one has offered a clone ANSA or similar design header for our cars. I've heard the argument that there likely isn't enough demand, yet there seems to be so many 4-1 types I doubt that's the case.....if you build it they will come. There has been a couple 4-2-1 headers offered in Europe (not sure if they are still available). Although most did not offer what has been calculated as the ideal dimensions for a mildly built engine (vs a "race" engine). Also I don't know if the "Allison" header is still available. However I was never convinced with that design. Yes, he had a dyno sheet showing improved performance, but that was compared to a stock US spec single-outlet manifold. ANYTHING will give more performance than that. I think all of the "spaghetti" bends might even reduce flow with so many changes in air-flow direction. Plus the diameter of the tubes were large for these engines, at least for a street header. Sadly, as far as I know there aren't any great options currently available for the typical road going X engine.

 

[dllubin]

I have a question. It seems the best header or at least the most versatile type of header for the X would be a 4-2-1 design yet all the bigger vendors only offer the same 4 into 1 design and they all look like the same design. Is there just a single supplier they all buy from?

I've seen a number of 4-1 headers and they are not all the same design. Some of them manage to squeeze in a bit more length before the collector by taking optimal advantage of the little space available between the back of the engine and rear firewall.

 

[Steve Thomas]

4-2-1 is more work to make... And people see the 4-1 style on real race cars and monkey see monkey do - monkey not big on context There are some pretty ordinary 4-1 around too. That 4 into 1 transition is both critical and hard to do well. Easy to do nasty tho.

 

[carl]

I have had many of the typical long tube 4-1 headers for my street Xs and they are all an improvement over stock. Most of us don't have a full machine shop in our basements so we are held to whatever is out there commercially. The 4-1 is just fine for our street purposes.

 

[Rupunzell]

Previously discussed many times.. primary exhaust pipe length is more important than just type (4-2-1 or 4-1). This is much about preserving the exhaust pressure wave frequency at a given engine RPM range. Too short, low RPM torque suffers, Too long high RPM torque suffers, in-between not quite optimal will produce power band dips (ala PBS header about 19" long with a power dip about 3,000 RPM.. it's too short). Sorta remember the optimal length to be in the 22-23" range for the primary pipes regardless of type.

Best bang for the buck?

So Ive managed to earn a whole $165 for trash cash from selling junk. I have a line on a Euro 4 to 2 1500 exhaust manifold, ($160 shipped) or a Euro spec camshaft at around $140 shipped. Which is the better deal?

xwebforums.com

Bernice

 

[Steve Thomas]

If the lengths are correct for the intent and if we are talking street - then there is no doubt that the 421 config is "better". In other words - if both a 41 and 421 are done well, 421 is "better" for street use and will deliver a broader spread of torque benefit. But - as far as I can see, neither is generally done well and the benefits people see tend to be in comparison to the stock system [there is a good stock manifold but there are a lot of very bad ones too]. People don't just change a header, they change the whole exhaust system and wow, the new one sounds really cool = power. And then of course, if you tune an exhaust to do particular things the you need a cam/carbs/porting/ignition all aligned with the same goals and many hours on the dyno. Most don't.

So, if you're a vendor, you keep a bunch of whatever is fashionable on the shelf and you make various claims about power gain secure in the knowledge that customers don't actually measure and just want something shiny with a cool noise.

If you are choosing from the readily available, then looking at the details is more important than the 41 or 421. Look at the flange the goes to the head - does it actually work with the inlet manifold? Look at how the pipes merge - can you imagine yourself as a pulse of gas flowing smoothly through them or are would you get violently banged around? Wall thickness, provision for hangers, flange to the rest of the system, O2 boss, finish etc.

 

[HaG]

I think that with the much better fuelinjection and injektion system thar are available today compansate for the 41 lack of middle/low rpm power.

 

[fiatfactory]

I have had many of the typical long tube 4-1 headers for my street Xs and they are all an improvement over stock.

That isn't actually much of an endorsement... the stock 4 into 1 cast manifold and "round the houses" single front pipe is absolutely woeful from a performance perspective, so it would not take an awful lot to be "an improvement over stock"...

SteveC

 

[carl]

That may have actually been my point. Remember when the 850s came with a nice stock exhaust, four nice long tube runners into a collector at the muffler? Even the 124 based cars had a nice cast manifold into a 2 pipe downpipe and then into a single pipe. So it's not like Fiat didn't know about good exhaust design.

 

[Steve Thomas]

I think that with the much better fuelinjection and injektion system thar are available today compansate for the 41 lack of middle/low rpm power.

and they would be better in the mid range with 421 - cos physics

 

[Steve Thomas]

That may have actually been my point. Remember when the 850s came with a nice stock exhaust, four nice long tube runners into a collector at the muffler? Even the 124 based cars had a nice cast manifold into a 2 pipe downpipe and then into a single pipe. So it's not like Fiat didn't know about good exhaust design.

there is a good stock cast manifold - for 421.

 

[KBabcock]

I actually took Steves advice and picked up a Euro cast 4-2 header and plan to build the rest from there. I was wondering if a custom header with longer 4 into 2 pipes would make that much a difference.

 

[carl]

We can contact Motor Trend channel and see if their Engine Masters series would do a comparison of various X1/9 exhaust header systems. Their dyno probably doesn't read that low!

 

[Mark_Toro]

Was cruising for parts and stumbled on this:

Of course unobtanium, but it is 4-2-1 for the early 1300s as Dr.Jeff suggests. So much to do before I start thinking seriously about this jewelry (like see if the engine is seized) but it would be fun to build a clone.

 

[Dr.Jeff]

Was cruising for parts and stumbled on this:
View attachment 81631

Of course unobtanium, but it is 4-2-1 for the early 1300s as Dr.Jeff suggests. So much to do before I start thinking seriously about this jewelry (like see if the engine is seized) but it would be fun to build a clone.

That is the ANSA exhaust I referred to earlier in this thread. If you look at the portion from the head flange, down to the red line (in photo below), you will see the 4:2:1 design.

Notice the relative lengths of the three sections (4 pipes, 2 pipes, 1 pipe, as noted in blue). Those were found to be pretty much ideal for the engine used in a street application. There's a old thread where several members - including a couple of engineers - worked all this out mathematically based on proven design principles, specifically for these engines. The length of the last section needs to include the muffler and exhaust tip(s). So if someone wanted to replicate the general design, their choice of muffler and final piping needs to total the same overall length.

 

[Mark_Toro]

Sounds like a good challenge! I built the headers for my GTV6 from a bag of tubes (speedway motors) and two 3-1 collectors, plus a couple of flanges I had made at work. After they were completed, I realized that the design was very much equal length and had alternating pulses entering the collectors (helps with extraction). I was just trying to make it all fit.

It was a lot of fun to build.

 

[Alex(Tenerife)]

That looks really awesome,, question is with the headers like that how ever will you fit it into the back of an exxy?

 

[Mark_Toro]

That's where the "fun" comes in

 

[GregS]

By chance I just happen to be doing some repairs on my headers at the moment. Mine were. the common 4 into 1 long tube headers. But 10 years ago after reading Visard and Guy Croft I cut the pipes off at the collector and converted them to 4-2-1 headers. The primary pipe length was exactly the 26" (from valve head) required for the ideal 4-2-1 for my requirements, good power and torque up to or just over 7,000 rpm for my track X. Would also be great in a road car.