Variator on a 124 engine

Road-race engines and ancillaries - general discussion
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wmausbach
Posts: 11
Joined: Sat Jun 24, 2006 3:46 pm
Location: Houston, Texas

Variator on a 124 engine

Post by wmausbach » Thu Jan 27, 2011 5:59 am

I would like to start of a discussion about variable valve timing on the 124 engine. In part of my surfing I ran across discussions about the Variator on later engines. It was first used on the old Alfa TC in the 80's. I was wondering how difficult it would be to fit this to a 124. In looking at it there are two issues.
1) The Variator is attached to the cam shaft and has to have a larger bearing at the nose. This will require some creative modifications to the cam tower. (Machining and welding)
2) The device is accuated by a solenoid thru the ECU. One solution would to use a MegaJolt system which to fire the solenoid.

Both of these are not easy but doable. What this would do is vary overlap up to about 4000 rpm and then retard the cam for high speed. This enhances the torgue in the mid range which is ideal for a street engine. By using standard parts it could be reproduced .

Does anybody have any experience with the more modern Alfa and Fiat engines using this device? Here is an article on the Alfa.
http://home.hccnet.nl/jaap.bouma/PhaseVariator.htm

Ciao
Wayne in Houston

TomLouwrier
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Location: Leiden, The Netherlands
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Re: Variator on a 124 engine

Post by TomLouwrier » Thu Jan 27, 2011 9:15 pm

hi Wayne,

You would certainly have a major task on your hands reconstructing the cam tower in order to house the variator, it's not a very small part. Cutting out the front bearing, welding on a sizeable piece of alloy, machining it, hoping things will stay straight. Machining the original cam shaft to fit onto the variator...
Interesting indeed, but very involved.

I can see the benefits of variable cam timing, but I'm unsure about the amounts of good it will actually do on a 2 valve engine, since these tend to have a better midrange torque than 4-valve ones anyway. That would be the pay off for having much more top end flow.
Guy, what do you think?

If you'd be going to put in this much effort, why not convert to 16v like here?
viewtopic.php?f=13&t=2416

regards
Tom

wmausbach
Posts: 11
Joined: Sat Jun 24, 2006 3:46 pm
Location: Houston, Texas

Re: Variator on a 124 engine

Post by wmausbach » Thu Jan 27, 2011 11:10 pm

Tom,
I am a fan of the two valve engine, especially for street applications. As you said the 4 valve engines are not noted for midrange torque which is the reason they need these tricks. The Alfa first used it on the two valve twin spark. I also have a GM Impala which has a push rod engine with variable timing to give more torque in the midrange where a road car spends it's life. I'm not after hp above 4000 rpm.
I also looked in to the 4 valve head conversion and it is not inexpensive as you have not just the head, cams,manifolds, and carbs or FI.. Here in the states the 4 valve heads are usually sourced from Austraila for about $1,200 for a rebuildable core. My preliminary estimate was about $3,000 for everything. My application is a spider which also involves hacking clearance to clear the extra size of the Fiat 4 valve head..
A friend of mine has an Abarth 4 valve and it is quite a bit smaller and fits the spider well. Here again the price is quite high (He would not tell me what he paid for it).

No, converting to a 4 valve for a NA street engine would mean you still have the midrange problem. The concept of variable cam timing has been proven in all types of engines and would only make a better case for the two valve in a street application. A good machinist could develop a process that would be able to be cloned by DIY guy with the modified parts. All the parts other than the convered cam tower are standard Fiat.
Ciao
Wayne
I

WhizzMan
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Location: Amsterdam, the Netherlands

Re: Variator on a 124 engine

Post by WhizzMan » Sat Feb 05, 2011 2:17 pm

16V engines not having as good midrange torque as 8V engines is a myth. It's all determined by cam profiles, ignition curves, fuel mixtures and such. Actually, most 16V engines have more mid range torque, but the cars they are in just don't give the "kick in the unacceptable" that older 8V engines cars give so the perception is flawed. This is caused by several things. Cars are heavier, due to more safety and luxury being put in. Cars have to emit less "bad fumes" and consume less fuel. This causes the tradeoff of fuel vs. accelration to go towards fuel economy and ecologically more accepted mixture rates. Even tho all these are a factor, the extra valves allow for so much more air to come in, that the engine usually does produce more torque. It's doing it so much smoother through the rpm range, that drivers usually think that a 16V engine is "dead" vs. the 8V feeling "so much more alive".

Cam variators are basically found on almost any modern engine, regardless of the amount of valves per cylinder. Yes, on the Alfa TS 8V they do help, a lot. Keep in mind that the whole engine, cam timing and injection/ignition system is tuned for the variator. The same applies for the 16V Alfa engines. converting a Fiat engine will not only require machining of the head to get it in, but also a complete redesign of the cam profiles to make them work optimally with the variator. If you are going through the trouble of doing this, you may want to investigate into the BMW vanos2 system. The Alfa system has an on/off setting, while vanos2 allows for you to choose the amount of cam advance.

I am not certain MegaJolt will have the proper outputs and software in place to control the solenoids for the Alfa or vanos2 setup. Basically, for the Alfa system, there is a map inside the computer that will switch on the solenoid based on rpm and engine load. There is another map that will switch it off, based on the same, but slightly different numbers. This is to make sure the system will not start to oscillate when you are on a threshold value. The Vanos2 system will probably have a 3D map and has several sensors to measure the current advance of the cam, the oil pressure and some PWM or analog output to regulate oil flow from/to the vanos variator(s) to correct the advance.

TomLouwrier
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Re: Variator on a 124 engine

Post by TomLouwrier » Sat Feb 05, 2011 6:40 pm

Hi guys,

Whizzman, you are right about 4-valve engines giving better absolute torque values. They flow more air, full stop.
Thing is that max torque usually is higher up the rev scale so the engine would be less flexible. Flexibility can be expressed as N_max_torque/N_max_power. The closer together, the more 'peaky' the engine will behave.
Also, early 4-valvers tended to have a pretty steep drop of torque once you got below a certain number of revs. That would make it feel even less tractable.
Finally early 16v engines were fitted to top of the bill models and would be tuned for high power figures rather than flexibility. This is more a marketing thing than good engineering.
Of course with variable valve timing and advanced engine management all these effects have now been overcome.
So I would say it's not quite a myth but no longer valid for current engines, and leave it at that.

Off topic:
As far as emissions and noise tests are concerned: many engines are made to pass the tests by tuning them with one or more lean spots. This can cause an ugly dent in the torque curve. Putting in a 'chip' that does not have this lean spot can improve the situation and is the reason that many people fit 'easy power'.
I don't like this way of 'tuning' since you really don't know what you're setting your engine up with, especially if you change more things (exhaust, intake, filter etc...). Most of the time these chips are sold as 'snake oil'. Beware.

regards
Tom

wmausbach
Posts: 11
Joined: Sat Jun 24, 2006 3:46 pm
Location: Houston, Texas

Re: Variator on a 124 engine

Post by wmausbach » Tue Feb 08, 2011 9:12 pm

WhizzMan,
There is no doubt that a 4 valve has absolutely more torque, the question is how high the rpm. In the real world 4 valves were almost always used with variable cam timing to overcome the compasion with the cheaper models with the two valves. I have many HP plots on the various 2 valves (Guy's first book) but only the Turbo versions of the 4 valve. The 4 valve is simply too expensive here in the States because everything has to come from Europe or Australia. There seems to be a lack of documentation of the NA 4 valve. I think that the two valve has better torque lower down in the rev range which is what I'm looking for. I just can not find any information on the torque curve on the NA 4 valve however. I'm not looking for maximum HP but flexibility.
You are the first person that has said there is a different cam profile??? I understand the significance of advancing or retarding the cam but little on the actual profile differences. Why would duration and lift be different?

The whole point of this discussion was to retrofit a Variator to the earlier engine to enhance driviability and performance lower down in the range. Sure the Vanos system is more advanced but it also requires a lot more computer magic and is way beyond the discussion here. The Variator is attractive because it is simply on or off and rpm dependant. It requires no special mapping as does the Vanos system. It is not the ultimate only something that will be an improvement with relatively stock parts and a switching device like MegaJolt. If the MegaJolt can not pull the solinoid you can always use a set of relays. Machining and welding can be done locally as Houston is blessed with an infastructure to support the Oil and Gas Industry.

Since the Alfa was fitted with and without the Variator, does anybody have any comparative data?
Ciao
Wayne in Houston

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