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Cam timing on a TS

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cam timing
4K views 22 replies 7 participants last post by  F156 
#1 ·
Here's one for those amongst you with some insider tecchy data.

I've been trying to find out what the cam timing is on the TS engines fitted to 147's & 156's. :confused:

Obviously the variator will add a certain degree (excuse the pun:rolleyes: ) of advance, but if anyone knows the basic cam timings, and if possible the advance curve of the variator, it would be a big help.

Also, what are the inlet & exhaust valve sizes for the 1.6's and 2.0's?

Ta :p

James
 
#2 ·
Anyone???

Just need a little help so i can determine what mods are worth carrying out, in which combination and what order. Can't do that unless i know the flow through the engine!!

Ta
James
 
#3 ·
I will have these data for you later today or tomorrow. I've asked my mechanic to check out the technical manual for these.

About the variator, i can tell you that the advance it gives is on/off and not gradual and that its activation is closely related to the throttle plate angle among other things.

Stay tuned.:)
 
#4 ·
The valve dimensions for the 1.6 and 2.0 TS (they have the same valves) are:
Inlet valve: 33.7mm
Exhaust valve: 28.2mm

According to these the rpm flow limit is at 9500rpm. Not bad. :cool:

Here are the cam timing angles:

1.6 TS
Inlet cam
opens at 8 (17) degrees BTDC
closes at 46 (21) degrees ABDC​

Exhaust cam
opens at 26 degrees BBDC
closes at 4 degrees ATDC​

2.0 TS
Inlet cam
opens at 3 (22) degrees BTDC
closes at 51 (26) degrees ABDC​

Exhaust cam
opens at 47 degrees BBDC
closes at 4 degrees ATDC​

The values in parentheses are with the variator activated. There seems to be a discrepancy in cam duration with the variator on and off which my mechanic cannot explain. For instance the 2.0 TS inlet cam has a duration of 3+51+180=234 degrees with the variator off and 22+26+180=228 degrees with the variator on which seems impossible. :confused:

By the way, my engine is a 1.6 TS but it has the 2.0 TS cams fitted.
 
#6 ·
Don't forget that the variator only works with the inlet cam.
 
#8 ·
OK, few more questions.

How did you measure the cam timing?

What are your intentions with the car? Are you making any further mods such as changing cams?

If I specify an exhaust it will be to match that 2.0 cam unless i know otherwise.

What kind of driving do you do? Are you more concerned with a wide torque spread, a punchy mid-range or top-end bias?

Do you by any chance have a shadowgraph that can record the inlet valve profile? Just interested to see how flat the tulip is.

Have you ever considered lighter / stronger / higher flow valves?

I’ve got some basic sizes for the exhaust but need the above info to idealise the design.

James
 
#9 ·
i just thought i would share with you that i have fitted piper fast road cams to my 2.0TS, went for an overall torque gain but there is a definet increase in power throughout, although mostly at high revs. i believe the cam duration is about 290deg. idle speeds are a bit erratic but not so much that it cant be used. as for performance, most definetly imporved, although the ecu remap, CAI, bored tb, matched ports and polished internals has helped a lot there too! 187bhp, 219Nm torque. huge improvement over stock!

just wanted to share that
 
#10 ·
JamesG said:
How did you measure the cam timing?
I didn't. I asked my mechanic to look up the technical manual. Is there something strange with the numbers that makes them seem not right? I'll try to cross-check them.

JamesG said:
Are you making any further mods such as changing cams?
Not really.

JamesG said:
If I specify an exhaust it will be to match that 2.0 cam unless i know otherwise.
Yes please. :)

JamesG said:
What kind of driving do you do? Are you more concerned with a wide torque spread, a punchy mid-range or top-end bias?
Mid to top end bias, say 4000 to 7600 rpm will be great, with preference to the high-end. I can live with poor low-end torque as long as i have adequate torque from about 3000-3500rpm so that i do not embarrass myself on the slightest slope. My current curves are quite satisfactory in form.

JamesG said:
Do you by any chance have a shadowgraph that can record the inlet valve profile? Just interested to see how flat the tulip is.
I can get my hands on a block of metal with the 2.0 cam lobe profile engraved on it, used by my mechanic to distinguish 1.6 from 2.0 cams. Will a photo of this do?

JamesG said:
Have you ever considered lighter / stronger / higher flow valves?
Not really. Nor will i change the fuel cutoff rpms. I will probably not mess with the engine itself anymore, the exhaust will be the next and final step after the throttle body and intake manifold.
 
#11 ·
alfasud.ti said:
I didn't. I asked my mechanic to look up the technical manual. Is there something strange with the numbers that makes them seem not right? I'll try to cross-check them.


Not really.


Yes please. :)


Mid to top end bias, say 4000 to 7600 rpm will be great, with preference to the high-end. I can live with poor low-end torque as long as i have adequate torque from about 3000-3500rpm so that i do not embarrass myself on the slightest slope. My current curves are quite satisfactory in form.


I can get my hands on a block of metal with the 2.0 cam lobe profile engraved on it, used by my mechanic to distinguish 1.6 from 2.0 cams. Will a photo of this do?


Not really. Nor will i change the fuel cutoff rpms. I will probably not mess with the engine itself anymore, the exhaust will be the next and final step after the throttle body and intake manifold.
Excellent!
Regarding the cam timings i was just a little concerned with the 6 (19 - 25) degree variation in advance by the variator.

I have to say that's a very mild cam, but for a 1.6 the valves are very big so you're getting plenty of flow at small openings.

On the subject of valves i obviously wasn't clear, sorry! I'm actually interested in the profile of the inlet valve itself, not the cam lobe.

As for the rpm flow limit for max power rpm, this is about 7500rpm for the 1.6 and 6000 for the 2.0! So no point playing with a 2.0 engine unless you fit larger or higher flow valves!!

Of course, doesn't bother you so back to the 1.6.

OK, i'll get on with running the numbers through a couple of models, biased towards your requirements, and see what we get.

Back soon!

James
 
#23 ·
Excellent!
Regarding the cam timings i was just a little concerned with the 6 (19 - 25) degree variation in advance by the variator.
Me too, could anybody please explain? I would say that the advance would be 25 degrees for both opening and closing times...

Who can give me the timings + variator advance and nominal cam heights of an 2.0 JTS engine?

Many thanks
F156
 
#12 ·
JamesG said:
Excellent!
Regarding the cam timings i was just a little concerned with the 6 (19 - 25) degree variation in advance by the variator.
So am i but it is still a mystery. I cross-checked the numbers with those of another technical manual i found on the net. They are slightly different for the 1.6 but the same for the 2.0. Maybe AR changed the timing for the 1.6 some time in the past? WHo knows... :confused:

JamesG said:
On the subject of valves i obviously wasn't clear, sorry! I'm actually interested in the profile of the inlet valve itself, not the cam lobe.
I will try to take a picture of an inlet valve next to a ruler. Will this do?

JamesG said:
As for the rpm flow limit for max power rpm, this is about 7500rpm for the 1.6 and 6000 for the 2.0! So no point playing with a 2.0 engine unless you fit larger or higher flow valves!!
I was hasty with my calculations (forgot to multiply by π/4), you are absolutely right for the 1.6, sorry...

But how come the flow limit is less for the 2.0? It has the same inlet valve diameter. :confused:
 
#13 ·
The formula i gave you was specifically for the 1.6 TS. :;):
The full formula is more complex, with the capacity and head chamber flow characteristics having variables to be accounted for.

Almost there with the exhaust dimensions, just working out primary / secondary length ratios vs torque spread...

James
 
#14 ·
hopefully this confirms the valve details and timings etc that you already have these are for GTV engines either euro 2 [?] or euro 3 but basically the same engine also a sketch of the valve.

hope this helps or at least confirms what you already know.
 
#15 ·
OK, here we go then. The following dimensions relate to the design for an exhaust on a 1.6 TS running a 2.0 exhaust cam.

The lengths for the secondaries include the collector length (tapered section joining 2 pipes).

Primaries:
ID = 1 3/8" (1.375" / 35mm)
Length = 16" (406.4mm)

Secondaries:
ID = 1 3/4" (1.75" / 44.5mm)
Length = 22" (559mm)

Secondaries to tailpipe collector
Length 6"
Outlet to tailpie dia = 2"

A low chrome content stainless steel would be the best material to use. (eg 15-5 rather than 18-8) What is available to you?

Tailpipe length to first expansion box = 32"

This will give you a progressive mid-range that will favor the powerband between max torque and max rpm. You should see a peak in the torque curve and a slight flattening of the power curve towards the max power figure.

Now, this is a 'basic' design, with no provision for emmision control. I'm looking at the options to do something similar to AR's standard design with a pair of small race cats close coupled. Not sure how the flow will work quite yet so hold in there for a bit and just digest the above figures - see how they compare to what you've seen around.

Will be back soon!

James
 
#16 ·
Thank you very much for your time James. Your results will be greatly appreciated in our club (www.alfisti.gr) where we have many members with 1.6TS running 2.0 cams. ;)

JamesG said:
Now, this is a 'basic' design, with no provision for emmision control. I'm looking at the options to do something similar to AR's standard design with a pair of small race cats close coupled. Not sure how the flow will work quite yet so hold in there for a bit and just digest the above figures - see how they compare to what you've seen around.
I've lost you here a little. You mean that there is no catalytic converter in your model?

When you say "close coupled small race cats" you mean that you will put the cats on the secondaries, like AR's preheater cats and completely omit the main cat? Well, our -not very educated- MOT guys will not appreciate this design and we'll have a very hard time convincing them that there actually *is* a cat! :p Or do you mean two race cats in-line somewhere on the secondaries-to-tailpipe collector, where the stock main cat is (if i understand the terms correctly)? :confused:
 
#17 ·
Yep you're spot on. I haven't factored in the catalytic converters yet. There's a lot of 'marketing' hype surrounding their actual performance and flow characteristics and i'm going through a few different cat designs to try and see how i can get the kind of flow i'm after. For example, there are types of cat which behave like an expansion box and types that behave like a section of plain pipe. Then you have restrictive, but ultra low emission devices which the manufacturers use to meet the very tight manufturers type testing regs which are far more stringent than annual MOT's.

I think AR have the right concept in using three cats, and i'm looking at the same, however, matching the right light off and main cat is not proving too simple for this configuration. I'll get there though! The downside is 3 cats would be expensive. Two high flow cats in the downpipes may be enough. Will have to see...

Whatever it ends up as, as long as it will pass the emissions tests, your mechanics should be happy. Hopefully...

I've given you the dimensions for the 'basic' exhaust so you can compare to some of the 'off the shelf' competition stuff available, and to let you know what kind of materials you'd need to source.

Hang in there. The final street legal design will be along soon enough, with full explanation and an ergonomic guide.

James
 
#18 ·
I happen to know the person who imports american cats in Greece. I can ask him for techincal data for several of his cats and of various types (ceramic/metallic, street/race etc) if you want. In his brochure the cats are described with a "maximum horsepower" and number of cells (only for the race ones) indication, either 100 or 200. I suppose that the way cats behave (tube or expansion box) is closely related to their number of cells, right? He is trying to persuade me to try a wild race cat for maximum 450hp but somehow i think that this monster will be too much -or too little in terms of backpressure- for my measly 1.6 TS.

I think that your solution of two cats in the downpipe poses a difficult problem: As you probably know AR's have three lambda sensors, two after the light-off (yes, i looked the term up :p) cats and one after the main cat. I was told that the ECU compares the readings from each of these sensors to deduct if there is a malfunction somewhere in the whole emission control system. If you totally remove the main cat how are you going to achieve the same difference in light-off and main lambda sensor readings? There will probably be an error code from the ECU, "Motor control system failure" i think. Of course there are ways of fooling the ECU by interposing resistors between it and the sensor but i don't like this solution and it is probably illegal as well.

On the other hand, as i may have mentioned before i have already have the light-off cats replaced with plain pipes with a big improvement in low/mid-end torque and throttle response and no error codes or emission problems as long as the main cat is in working temperature. Given this, the fact that a metallic race cat can be heated much faster than a stock ceramic one and the difficulty/cost of manufacturing a downpipe with two cats i believe that keeping the main cat instead is a reasonable and less expensive way to go. Of course you are the expert. :)

I plan to compare your design to the stock one of the 2.0TS exhaust system and maybe a full Supersprint exhaust system from manifold to tailpipe, if i can find its specs. I'll tell you what i find.

PS1: I hope/believe you will benefit from this quest as well, i would not feel good about you spending your time for some stranger over the net. :)

PS2: I think that this topic should be given a more appropriate title by the mods, how about "Modelling an exhaust system for a 1.6TS with 2.0 cams"? ;)
 
#19 ·
JamesG, i hope you are here somewhere reading. :)

A friend of mine has recently entered the "exhaust improvement" loop, he read our conversation and asked me some questions:

- Will the exhaust you specified earlier in this thread work with a single main cat, specifically a metallic one with 400 cells? If not what do you think should be altered in the design? I am not asking you for another series of modelling/tests, your educated guess will be enough.

- Have you been able to find the dimensions of the stock Alfa Romeo exhaust for the 2.0 TS? If so in what way are these different from the design you suggested? To be honest I haven't been able to measure any exhausts yet because of the late hours at work. :(

Thanks in advance and hope to hear from you soon.
 
#20 ·
Sorry it's been a while, my laptop died and i had to wait for our IT bods at work to fix it. (motherboard aparently) All my analysis stuff was on the hard drive :rolleyes: Doh!
Been using the dsektop for posts in the mean time but All is OK now!

As for an answer to your question, yes the cat should work fine if positioned after the required tailpipe length. Problem here is it may have difficulty getting up to temperature. Ceramic coating & heat wrapping would help there. The third HEGO will help here as it will tell you how effective the cat is. If you know the sensors are working and you keep getting the warnings, the cat is too cold. If you have an oscillascope, (got one in my loft somewhere for some unknown reason??!!?) you can test directly.

I have utterly failed to harass my contacts on providing data for cat flow dynamics, so can you please get what you can from your friend and i'll do what i can to get as close to ideal as possible first time. Cheaper that way...

In case i haven't mentioned it previously, the two lambda / HEGO sensors in the downpipes measure the mixture for the two cylinder pairs. This is used for closed loop emmission control. The third sensor further down the exhaust is only there to make sure the cats are working. Doesn't provide any mixture control. Can be replaced with a dummy which will send a nominal 'good' signal to the ECU, but if you're fitting a cat in the exhaust it's best to leave it in as it tells you if it's not working!

James
 
#21 ·
Hello again James. Sorry to hear about your laptop. :(

My friend has just finished sorting out his new exhaust. He kept the stock manifold and replaced the downpipe and the cat. The downpipe is 1.85" dia for the secondary pipes and 2.04" dia for the collector, which is very close to your specs. The cat is of oval shape with 400 cells, no other characteristics known so far. He reports good low-end throttle response and better mid/high-end performance (>3000rpm) wih the stock 1.6 cams, he is planning to replace them with the 2.0 ones like i have.

As for me i haven't been able to measure the stock exhaust as i have been wanting to do, too much work. :( But i will have my intake manifold and TB replaced next week, so i hope i will have the opportunity to measure the exhaust. Then i will start my research as to what needs replacing, according to your specs. :) Meanwhile i'll have a chat with the guy who imports cats and try to see what information i can extract from him. I don't know if these cats are available in the UK, they are called "Americat".

About the HEGO sensor, i am not considering of removing it, i want the car to be able to pass emission tests at any time. My first choice will be to use the 2.0 manifold and replace the downpipe, collector, cat and tailpipe according to your specs.

I'll keep in touch with any new info i get my hands on.

Constantine
 
#22 ·
James, are you here somewhere? :)

Yesterday i went to my repair shop and i finally managed to measure the exhaust of a 147 2.0 TS Selespeed. Due to bad terminology knowledge please excuse my mistakes and correct me or ask me to clarify if necessary:

Exhaust Manifold
Length of pipes 1,4: 41cm
Length of pipes 2,3: 31cm
Inner diameter at engine head: 29mm
Inner diameter at downpipe end: 36mm

Downpipe
Length of dual tubes to collector: <inaccessible, could not measure>
Inner diameter at manifold end: 37mm
Inner diameter of collector (single tube): 43mm

Tailpipe
Inner diameter of pipe from collector to cat: 43mm
Length of pipe from cat to 1st exp.box: 24cm
Inner diameter: 43mm

Length of pipe from 1st exp.box to 2nd exp.box: 3.7m
Inner diameter: 37mm.

Note that i measure the outer diameters and subtracted 3mm to get the inner ones because the exhaust was assembled on the car, so i didn't have access to the inner diameters.
 
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