4 into 1 exhaust system vs 4-2-1 ?

S

sledghammer

True Classic
I have recently changed my exhaust system to a 4 into 1 set up thinking it would improve gas flow. Its a csc system made in Italy.
Previously had 4 2 1 which produced 115hp
Now at the rolling road its down to 102hp
The mechanic says I may need to get the carbs (twin 40 dcnf) rejetted, which I have booked it in to have done.

Any one else have any similar experiences?
 
Hmmmm, methinks........!

.....you should have stayed with the 4-2-1 system!
It's my understanding that the OE Euro-spec 4-2-1 exhaust manifold is most efficient, and in the US in particular, is highly sought after to replace the asthmatic US-spec system.
Quite some time ago, a very good writeup on this comparison was posted on XWeb - may have been back on N54. I think it was posted by SteveC from Oz (but I may be mistaken on that!)

cheers, Ian - NZ
 
What was the point of ever manufacturing this exhaust system if it underperforms a standard system? I dont get it.
 
Emissions

Euro didn't have emissions to deal with so their cars had more HP due to this fact.

TonyK.

Grimsby Ontario Canada
 
What is your average hp???

4 - 1 Are designed for high rpm horsepower. I will trivialize it a bit and say 4-2-1 are designed for more torque. Unless you have a lofty cam and intake system that will flow at the high rpm you will not really see the benefit from the 4-1. Just curious did you go to the same dyno for both runs to get your numbers. Different dynos have huge swings in numbers. The dyno I go to reads my whp as 100hp but another across town consistently reads 15% higher. It is key to make sure you calibrate the runs too. I read many, many, many posted horsepower numbers that are just not possible and more than once I have found the calibration was not done correctly. Lots of question concerning header length and diameter as well but that info is in the archives somewhere. Do you notice any difference in driving the car? At a 15% ish difference you would certainly notice the difference. Look at the entire hp curve and compare the before and after.
 
Re-jetting

Basically for the reasons stated by Dallarax19 above, the carbs will very likely require re-jetting to compensate for your exhaust change. Everything works in relation to everything else, and a change to one item generally requires changes to the others to match. I also agree with his comments about the dyno numbers...compare apples with apples, even the weather conditions on the day of the test will affect the results. And ditto for his comment to look at the entire power curve, not just the peak HP. For that matter, look at the torque curves as well; horsepower is not the whole story (especially for a street car where you will 'feel' the torque more). Your new exhaust may end up offering better overall performance once you get the rest set up to match it. I will try to find the referenced Xweb threads with exhaust comparisons, that could prove very helpful to see what others have already learned.
 
Thanks for the comments and look forward to reading the link if you can find it.
Its noticeably different to drive.
And the dyno was done at the same place by the same person.
With the stock exhaust system, I road tested it with a passenger in the car and had 0-60 in 8.6 seconds.
With the 4-1 exhaust 0-60 is now 9.5 seconds.
It does want to rev longer though with this new exhaust system, I can get 70mph in third gear.

The specs on my car are, twin 40 dcnf, 40 80 cam with vernier pulley, milled head for higher compression ratio (had to use a 1300 cam belt bearing as 1500 one too thin), lumenition, electric fuel pump, lightened flywheel, 39.5mm inlet valves and a crappy 4-1 exhaust!
If I can get back to the original hp with rejetting I would be happy!
Do you think this is possible?
 
Sounds like you have all the right stuff

Could you please post your before and after dyno curves. I am curious what the torque curve and AFRs look like. Jetting on the DCNFs is also buried in this site too (check Brad Garska) but I would like to know which chokes and emulsion tubes you are using. All key details. 0-60mph times look about right. I range 7.8-8.1 with my set up. Last point what is your advance, static and full? Is the distributor from a FI or carb car? Points or electronic? What 4-1 exhaust are you using? All should help. Lastly make sure the carbs are fully synchronized. After a day of being at the track my carbs will get out of sync the issue is from vibration and the butterfly linkage carb to carb.
 
Last edited:
I noticed a drop on power when I went from a Janspeed exhaust to the same one you're talking about. Just didn't have the same feel. Sadly the Janspeeds are no longer available, and were not without their own issues.

My car is standard 1500 carb but rejected, K&N filter, Lumenition electronic ignition. Timing set around 10 deg BTDC. It goes, but feels more sedate somehow.
 
Full CSC system or just the branch?

Hi Sledghammer,

I have recently fitted fitted the CSC branch, together with a custom fabricated free flow muffler and pipe. This was done at the same time as a full rebuild and upgrade (1600 stroker...soon to get programmable FI!), so too many variables to do a before and after comparison unfortunately. The original setup on my vehicle was a Euro spec 1500 with the 4 into 2 into 1. Also I`m still busy running in the new setup, so there are no dyno numbers yet.

For what its worth, I noticed that the "U" bend at the end of the branch (and presumably also the CSC muffler) appear to have a very restrictive diameter. The end of the 4 into 1 pipe measures around 48 -50mm from memory, but the "U" bend reduces down to around 42mm, which my exhaust guy agreed would likely be too restrictive. On my setup I had the CSC "U" bend re-made from 50mm stainless steel exhaust pipe, into a 50mm free flow muffler. As I said, can`t verify the results yet, but it sure sounds nice! :devil:

Not sure if the above helps you, or what the more experienced Xwebbers will think of this, but I thought I`d put it out there in case it has any merit!
 
Last edited:
i have almost the same setup as sledgehammer and have 117 hp. The exhaust is freeflow. Maybe you should use bigger jets. What are your chokes, mains, emulsiontubes and a/c jets?
 
Sledgehammer,

I have been searching Xweb for some exhaust system data. But so far I have not found any direct comparison with a factory manifold (cast) to a aftermarket header (tube type). Several discussions about the single-outlet vs. double-outlet factory units. And some discussions of various engine builds with various exhausts. But no direct testing results between manifold vs header for the X1/9 (that I find so far). {And by "testing results" I mean controlled dyno data} Maybe other members can assist in finding some. It does not help that there are not many choices on new headers for the X1/9 market any more. In other segments of the automotive industry, most testing of exhaust systems find increased flow capabilities with a purpose built tube-style header than a typical factory cast-manifold. But as we have stated previously there are many factors involved, so it is not a simple answer. The questions asked by DallaraX19 are good ones. I recall that you have scheduled a dyno session to re-jet your carbs. That would be the time to play with timing settings, carb synchronizing, etc. (again, everything needs to be set-up to balance with everything else on/in the engine). As you found on your initial driving impressions, the header will likely raise the power curve to a higher RPM range vs the standard manifold (also a shift from torque levels to horsepower levels). I think you are asking all the right questions and seem to be taking a good approach to finding solutions, please keep us informed.
On a side note. A couple of you UK guys have listed having the "Lumenition" ignition. Isn't that from "Autocar"? I used one of their "NewTronic" motorcycle ignition systems on a vintage bike build with great results. Unfortunately we don't have their products here in the US. Can you please tell me what items they still offer for the X1/9 (part numbers would be great if you can) and where they might be reached? I like their stuff. Thanks.
 
Thanks for the comments thats a bit more encouraging to know martijn is getting 117hp with nearly the same setup.
The exhaust is a csc system, the u bend is 43mm od and goes into the silencer which is 50mm od.
I do not know what jets are in it but will get the dyno tester to make a note of them.
I had some free time this afternoon so thought I would play with it a bit and the new plugs turned up as well (bosch super 4's).
Checked the timing first, when I put the engine together it was set at 5 degrees befor TDC at 850 rpm.
It was set at about 12 degrees befor TDC. Would the dyno tester really be that far out?
I reset it to 5 befor TDC and road tested it.
Three runs from 0-60.
1. 8.1 seconds
2. 8.4 seconds
3. 8.58 seconds
I was pretty pleased with this but it still does not seem right.
Rejetting may be the answer but I am a little concerned that the timing was set way off by the dyno mechanic. Has he set this wrong to get me back in?
Got back home and put the bosch super 4's in.
Right away it does not seem to idle smoothly.
Three runs from 0-60
1. 9.25
2. 8.9
2. 8.45
Missfiring and spluttering on the way home.
Back to the ngk's me thinks. And index them.

DrJeff, there is lumention optronic igntion on ebay, this is what I have. http://www.ebay.co.uk/itm/fiat-x19-...arts_Vehicles_CarParts_SM&hash=item25648a35d3
 
Sledghammer and Martijn

First, thank you to Martijn and Sledghammer for the Lumention Ignition references. I'm glad to see they still offer kits for the X1/9.

Second, Sledghammer, regarding the tech at the dyno shop resetting your timing. I would not necessarily suspect that he was trying to do something under-handed. Setting additional advance on the timing often yields some performance gains, up to a point. The dyno readings can tell the best ignition setting to maximize engine output. And a road test will assure that no detonation (pre-ignition or 'ping') results from too much advancement (occurs most when the engine is fully warm, the ambient temp is hot, and the engine is under heavy load). Other factors like mixture (too lean), fuel octane level (too low), spark plug heat range (too hot), also contribute to detonation. And with the modifications to your engine (increased compression, etc), the 'ideal' timing for you will likely be different from stock. This should be one of the things he determines when he re-jets the carbs. Another critical factor with yours is the dual carbs; they need to be in proper synchronization (with each other)...something else for him to check.
As you can see, there are LOTS of things that need to be sorted out to make everything work together properly. And a good dyno shop should be the place to get that done. But it can take many test runs with a knowledgeable, experienced tech (as well as some 'trial and error') to find it. You might want to take both sets of plugs with you to see what he has to say about them...could be interesting to learn some actual dyno results to compare them. Something else you might want to do before going to see him, take a look at some articles about dyno testing (there are lots of them, just look online). This will help to give you an idea of what to expect from it and may make you better equipped to deal with him should any questions arise.
Edit: I just remembered that you also have an adjustable cam gear. That is yet another thing that can be played with on the dyno. It might help bring the power curve down into a lower RPM range, if you feel it is too 'peaky'.
 
Last edited:
Thanks DrJeff, good advice again. The dyno tester did mention adjusting the vernier pulley as well as rejetting, so I will see what happens on Monday!
 
Following up....

Just a few quick points, 12deg advance is right on. I do not know what your distributor configuration is but you need all the advance you can get You want 34-36deg total at full RPM - I am thinking you are not reaching the full advance. Misfiring and sputtering needs to be clarified. If it is backfiring through the carbs then you are running too lean but if it is backfiring or poping through the exhaust then you have a header leak or you are running too rich (don't think this is the case). Both conditions show on deceleration. A leaky header (manifold or crack) will have a large "BANG" as the revs drop and a rich condition will have a pop, pop, pop on decel. If you are not sure then run it and then pull the plugs. Black/Wet = Rich, Tan/brown = OK, White or Grey = Lean. All plugs should look the same, if not you have something going on in one or another port/cyl. Again check to make sure your carbs are syncronized. In your dyno curve you should have an AFR curve what does it look like? That is key. If you have not done so get Martijn's jetting or PM Brad Garksa, he has a good combo for the DCNFs, Jets, chokes, emulsion tubes. I run DCOEs so can't help that one. I will keep following this post. I hope you get it working right soon.
 
Thanks DallaraX19, I have only been getting the spluttering since I changed the timing to 5 degrees befor TDC. I have reset it to where it was after the Dyno run.
It was through the carbs not the exhaust.
Plugs are all brown, although if I am being picky, three and four cylinder plugs are slighty lighter in shade.
Really appreciate the input guys, it has helped alot.
Can't wait till Monday now to see what the Dyno guy can do!
I'm like a child just befor Christmas! Better not be dissapointed...:excited:
 
please post the results, i'm running rich om 2000-5000 rpm. so i would like to now your jetting after the dyno
 
You must log in or register to reply here.
Back
Top