Fiats original exhaust system comperd to Vendors (Fiat 124)

[Weelan]

You have dual 40idfs? You upped the pistons to higher compression right? I've heard those carbs don't make the big gains until you up the compression too.

[So Cal Mark]

If you like the oem system then you should stay with it. You're already convinced all of the stock stuff is better anyway. If you're sure the stock stuff makes more hp, run your car against a modified car to see which is faster

[Thunberg]

If you like the oem system then you should stay with it. You're already convinced all of the stock stuff is better anyway. If you're sure the stock stuff makes more hp, run your car against a modified car to see which is faster

I´m not sure that "the stock stuff makes more hp", where did you get that from? And "stock stuff" compared to what? Sorry can't follow you.

All I´m asking for is dyno sheets from owner of Fiat twincam engines that have dyno test different systems or vendors that have test different systems, I can not find it.

[131]

I have right now weber 40 idf, but sure weber 44 idf would be better

Do you have dyno sheets to prove that?

[Thunberg]

I have right now weber 40 idf, but sure weber 44 idf would be better

Do you have dyno sheets to prove that?

No prove of that, but if I change to 44 idfs I will certainly dyno test them and compare the dyno sheets to my engine with 40 idfs, so "sure" was perhaps not the correct word, should have written "guess" or "suspect" instead, sorry

[131]

The point I was trying to make is that logic would dictate that getting more air/fuel into an engine and exhaust out will increase performance, replacing 40 with 44s will increase performance, it may lose a bit down low but will breathe better up high in the revs. Trying to find dyno sheets to prove that for a 40 year old car of which there aren't that many around is a tough call. Any dyno sheets for an exhaust system are pretty meaningless anyway, a 10hp increase on one motor may only yield 5hp on another motor, even if with identical specs. It may also produce more HP, but less bottom end, a pain for a road car. And even if it's published on a website, who's to know if it's kosher data anyway.

[BEEK]

My .02

I raced fiats for many years, bigger carburetor, more compression, and better flowing exhaust. All made increases. Never dyno'd any particular configuration; I did dyno 2 engines, both on race exhaust. Logic has to tell you that larger and better flowing will increase performance. There will be a point of diminishing returns. You can use a dyno to find that or just make an educated guess based on past performance and readily available information. Logic tells you that a 4-1 cast manifold with unequal length primaries and a single down pipe into an OEM catalectic converter. Will not make as much power as a header with longer equal length primaries, nice flowing y connections and a larger diameter pipe with a performance cat converter or eliminate it all together. Fiat engines are easy to over carburate and over cam (too large). The basic air pump assy is pretty efficient except for low compression in the US. Raise the compression and these are awesome engines, especially considering the design is over 40 years old

[Thunberg]

I guess my definition of the word ´”performance” perhaps ain't the word that define what "all" define “performance” for.

For me I accept “ performance” if that kind of equipment actually give a higher “performance” against something else “tested against”(, but still it aint perhaps a "performance" for me, depending on what I have).

And if it is for me a true “performance” equipment it must in some way describe the performance in a proper way, otherwise it can be a performance equipment for some but not for all. For some it actually will be “losing performance”.

If you spend a lot of money I think dyno test and comprehension is the best way of show increase of hp in a certain rpm region. Some like increase of hp at some region and some like hp increase in other rpm region. So my question is still the same:

I´m asking for is dyno sheets from owner of Fiat twincam engines that have dyno test different systems or vendors that have test different systems?

But thanks for other comments

[So Cal Mark]

you seem to be under the impression that there is substantial hp at lower rpms. There isn't. No one measures hp at 1500rpm. I can post a dyno sheet from a tc, the graph starts at 2300rpm. At that rpm the motor is making 31hp. Talking about hp loss or gain at that level is just a waste of time.

[Thunberg]

you seem to be under the impression that there is substantial hp at lower rpms. There isn't. No one measures hp at 1500rpm. I can post a dyno sheet from a tc, the graph starts at 2300rpm. At that rpm the motor is making 31hp. Talking about hp loss or gain at that level is just a waste of time.

For me personal I like to know if I´ll find any improvment at 2500-4500 rpm. I use my car for a short time in a town and spend the rest of the time on quite narrow roads more or less alone. I have the 4-2 fiat original manifold and the 2-1 original "downpipes" and no "cat". As I "heard" that system is "quite good" but I actually don´t know.

However, Guy Croft said:

"If you get a system made, go 4-2-1 and with combined py & sy lengths 34" with 24" py matched for length and short secondaries. "

But that system I cant find, perhaps I should be satisfied from what I´ll got

[BEEK]

guy has spent a lot of time perfecting fiat twin cams. he has dyno information to back up his research. guy is an expert in his field and has many years of experience working with fiats. myself i have raced fiats for many years and experimented with different exhausts to fit my particular application. some of what i found was the same, some is different. but it worked for me. as i won 52 races and 2 championships. i know what i would put on my street car. i think it may be a bit excessive to want or demand dyno sheets or to say without that information the systems dont make any gain. factory exhaust was designed for emissions and production purposes. the 4-2-1 fiat factory manifold is a very good oem setup. i have ported those manifolds and made gains there too. sorry cant give you dyno sheets, but results spoke for themselves. a header, performance mid pipe and better rear muffler will make (guessing) about a 5% difference over stock, if you had the single downpipe and a cat, you could gain as much as 10%.

[geno58]

There is a lot to consider before any answer is correct. If you have a stock 2L TC, that came with a water carb, and a 4 into 1 exhaust and cat, resonator and muffler. You may get a small bang for your buck. Now on my car the only mods I have done, is changing to one of Marks Empi carbs, early single plain intake manifold and 4-2-1 exhaust with Cat delete.
Over all the car runs better, more seat of pants power and better milege. Now, if I were to change to any ones header system, there may be a little improvement, but I would think it would be minimal. Now if I went to Dual IDF's Higher compresion, hotter cams and head porting, the benifits of headers would increase proportionatly.
Every thing you do needs to be proportional to each other. The more air you are able to take in, the more you need to get out. Any weak spot on either side, intake or exhaust, will have a direct effect on the benifits of the modifications.

[baltobernie]

I can post a dyno sheet from a tc, the graph starts at 2300rpm. At that rpm the motor is making 31hp.

HA! What a slacker! I'm making 32HP @ 2300 Zoom, zoom

Re: New head

Post by baltobernie on Thu Sep 17, 2009 10:24 am
The numbers are in:

120 HP with a decent idle, good throttle response, a nice flat torque curve, etc. The last (and final!) tweak was adjustable timing gears from Jason Miller. Turns out I was only 1-2° out on one side, but 8-9° on the other. This was enough to wreck the low end and cost power 10% across the board. I guess my advice here is to plan on incorporating the time and expense of "dialing in" the cams when doing a performance rebuild.

Specs:

1792cc
10:1 Persan pistons from Vick, assembly balanced to 2g.
1800 head, stock valves, de-shrouding and smoothing per GC video
single-plane 1800 intake, port matched
one 38DGS, 65 idles, 150 mains, 200 airs, stock air cleaner, K&N element
IAP p/n 92400 cams, 40/80 - 80/40, 0.016", cams set to IAP specs using Millers Mule adjustable gears
single-point distributor, Pertronix module, centrifugal advance, recurved by Advanced Distributors, Bosch blue coil, Champion N6Y @ 0.024"
Ceramic-coated exhaust manifold 4-2 cast iron into 2-1 secondary pipes - (standard 1800) - custom 1.75" pipe back to rear-mount Flowmaster p/n 952060
ignition timing optimized on dyno; I don't have a front cover, but it looks like approximately 10° BTDC. I can put on a cover and use a dial-back light if anyone's interested

102 RWHP @ 5600 RPM, 104 FtLbs @ 4200 RPM

With more carburetor and exhaust, it is conceivable that this curve would keep climbing from 5200, resulting in approximately 110 RWHP (140 SAE net). Power beyond that would probably take a bigger cam and make for a more challenging daily drive.



"Thunberg", why not take your car to a dyno now, and tell us what you have? Maybe then somebody can give you some suggestions.

[So Cal Mark]

Bernie, a good exhaust system would make some impressive numbers on your motor. 1.75" exhaust won't/can't make good top end power

[Thunberg]

"Thunberg", why not take your car to a dyno now, and tell us what you have? Maybe then somebody can give you some suggestions.

Done

Engine:

Fiat original 1995cc (Argenta)
Fiat original camshafts: and I guess : 15/55 57/13 and 9,5mm lift (Argenta)
Fiat original head no 5991740 (Argenta) and I guess 43.5mm intake valve according to SteveC (turbo124)
Fiat original 40 idf Webers
Fiat original waffle intake manifold
Fiat original 4-2-1 exhaust system (4-2 cast iron into 2-1 secondary pipes (short py and long sy)), no catalytic converter
Ignition: Pertronix-Ignitor
Coil: Flame thrower
Fuel pump: Facet "Red top"
Fuel pressure regulator: Adjustable Filter King
Air Filters: Lynx ramflo

Dyno (Sun rolling road) Engine:

116.9 hp (DIN)@ 5480 rpm and 158 Nm @ 4450 rpm

(If you use rolling road stick to the same rolling road when you "upgrade" your engine and for best result use the rolling road just before the "upgrade" and than direcly after your "upgrade" it can differ 15 % between rolling roads see )

http://www.andyforrestperformance.co.uk/26063.html

Why is life so complicated?