Ah - sounds fun.

First thing is that the B202 cams in a B234 don't quite give the timing they would do in a B202. (Relation through the timing chain / sprockets to crank is a little different).

So - this means they just bolting them in is not worth doing unless it so happens to match your goals.

Now - with a smaller turbine with high backpressure you would generally have a slighly larger intake duration VS exhaust cam duration. AND/OR don't retard the exhaust cam too far.

You'll see on the other post you have asked the question, the chap is saying to fit the 254 cam on exhaust only. Careful with that as in this case it's a chasm of a turbine running relatively low boost so I don't think it's comparable with your 19T at all.

I can only speak from my messing but what I did was try to work more to the cam centerline. Assuming they are symmetrical cams, then this would be the point of the peak lift.

For decent power - a start position of 110degrees centerline might work.
ie. peak lift on the intake cam is 110degrees ATDC (after top dead centre)
Peak lift on the exhaust cam is 110 to 112degrees BTDC

Chances of you setting it up and being happy with the first setting are about nil so make it adjustable. Changinig timing on intake had a much bigger effect than anything on the exhaust so get exhaust about right, then mess with the intake. Moving the intake cam 5 degrees had a BIG difference on the drive - way more than I expected. I don't think putting the 254 cam really much difference overall due to the lobe shape but the timing certainly does.

You know if you are pushing theworking rpm range very high if you have moved intake so that the intake valve only starts to open at TDC. (Standard is opening at about 14 degrees)

Here's my effort: These were B202 cams ground to 256 / 9.3mm. This setup is still in the car after 15k miles so works nicely.

http://www.uksaabs.co.uk/UKS/viewtopic.php?f=35&t=29048&start=160

 

b202 cam timing

faero
I was hoping you would reply.
I am trying to get a little better flow at higher rpms, 5500 to 6500 lets say. Maybee reduce backpressure and egt ect.
below 4000 rpm is not an issue for me.
I have the cams in there now and can make some adjustments around 7 deg with some gears I have ground the cogs slightly on.
Where should I start?
It seems from the specs that the exaust cam (61-13 is pretty advanced) and the intake(16-56) is somewhat retarded, thus giving quite a bit of lobe seperation.

 

It seems the answer is in the post that Faero gave, Norman tried the setting and found the car to accept more boost past 5k and accelerated nicely to redline. I would start there and then all you can do is play with try a little more here and a little less there until you find the best results for your car, engine and turbo and gearing.

I would start with his settings, set the intake at 110 degrees and the exhaust at 110 degrees and then see how that does and play with it. Try advancing the intake a few degrees and if it reduces lsa, then go the other way and if it does not change, then your best postion is at 110 degrees. Now move to the exhaust side and do the same, try retarding it 2 degrees and see if the LSA is improved and if not, to the other way and see how that works, you may find 110 degress is optimium.

There is no easy answer for this type of cam dial indicating, you will have to play with them for best results and maybe get it better at the 110 degree starting point.

Having a regrind would not hurt, getting the lift to 9.2 would be nice and that will help, like the maptun cams. If you want it easy, that would be the best thing to do, order up some regrind cams and go with the settings they recommned,

John

 

I just checked the setup with the b202 cams in my 9000 Aero. They are retarded about 7 to 10 degrees as near as I can tell using the v marks as reference.
Would I want to get them lined up at TDC before going any further?

The reference I had says the exaust valve open (EVO) is 61deg BBDC and EVC 13 deg ATCD for duration of 54 deg. Is this correct?

 

MTAero - Thanks but I'm no expert! What I did works nicely but can share my experience. Not many folks mess with cam timing I agree that on paper that the intake Cam is close to what you need. You could retard intake a touch more, and the exhaust is too advanced by a fair bit imho thus why the 1985 only 252 exhaust cam is more a choice for power (it's much more retarded).

Problem: I bet you don't remotely have these specs in the car so that cam timing is out of the window.... If I recall, the B202 cam ended up at about zero lift at TDC (!) due to the B202 VS B234 mismatch.

Time to get the dial depth guage out and start messing....

Can you get the Lift at TDC of what is currently in? That will give us a great starting point. Maybe run the engine a little before you take the first measurement. If you can fish for a point of peak lift too - it will help paint the picture.

Trying to find the centerline reliably is quite tricky - You think you've got it but then you back and decide it's b0llocks. Lift at TDC for me was more repeatable but then it doesnt tell you the timing!


Good point John - I'll ping Norman to see what he had them set at as that's a good reference on the exact same cams and a very similar turbo. My regrinds mean my settings are no use really.

You'll see in my post that the first attempt resulted in the wrong values as the hyraulic buckets had been lying too long and the lift had changed with the new cams. This shouldnt be an issue for you but I'd always go back and check lift at TDC on both cams after a decent run before you decide your next move.

One benefit of regrinds is you can ask the grinder to tell you what lift at TCD should be at 110 degrees. Then you are nicely locked in with a start point. Unfortunately Saab haven't shared this with us for the stock cams.... Unless someone with a C900 T16 did.


PS - I wrote this before your reply above - This confirms the B202 mismatch. The cam cap markers are OK to try and match - to give a direction guide. But still best to get a lift at TDC value too.

 

Thanks guys,
The way I have them in the picture works good, that's out of the box into the car pedal to the metal.
My car runs so good all the time that It is hard to feel improvements until you're at about 200kmph and make the shift into fifth in about the third or fourth lap of a track session.
The settings I want would be the ones that keep the egt's and backpressure from chocking things up after a few laps of hard driving.
I really don't understand the cam thing but I thought these would be worth a try.
I picked up three sets of these b202 cams so They may end up in my Viggen too.
The regrind faero did sounds interesting, so the lifters can actually adapt to the back of the lobes being ground somewhat say .5 to .75mm, that would be nice extra lift, I think one of the local machine shops could do that regrind. Any suggestions?

 

Going back to your pics - and this assumes you found TDC with a piston stop and not the crank pulley marks.

Intake cam: Looks heavily retarded. (i.e. cam is lagging behind the rotation of the crank) This pushes the rpm range up.

Exhaust cam : Slightly retarded.

Given the cam specs - you might be in a good spot on the exhaust cam but I suspect you've lost midrange slam and a bit of spool with the intake cam. It will undoubtedly give you a lovely sparkle up top - but might be overcooked.

(the fact you can see it's off from such a distance in the pic means they are out a lot).
For simplicity - you might get away with moving the intake cam and entire tooth the other side of the marker. It will be too advanced but will let you feel the difference.

Re-grinds: To get my extra 0.63mm lift I think they took about 1mm off the back of the cam lobe and re-shaped on the new lobe shape.
The hydraulic buckets then lift up to take the slack. I'd be wary of going over 9.3mm lift on the regrind as I think you get near the extension of the buckets. If I leave the car for a few weeks they rattle a bit on start and clear completely in a minute or so but they never did that on the T5 cams.

Lobe shape will never be as 'fat' as an aftermarket cam but you pay your money....

 

Hi, i,ll see if I can find any imfo from my previous trials, but if you simple stick them in with the 240 cam sprockets and set them up as per a std cam installment and go try, this is where I found the added sparkle above 5500 rpm ( i,m running with a td04 6cm with a compressor from the GT28rs so we are not miles apart - you,ve got a 19T ?)
as a ref: when the cams were in, the notch is over towards the open end of the V versus the nose
it did make the engine a bit flat up until around 3K, it would make boost no,s but the desire to burn it efficiently just wasn,t there, perfectly drivable with a bit of throttle feathering, but i,m in no doupt via basic seat of pants there was a surge up top

one thing I do recall ref: the 252/254 cams - there is bugger all additional flow from them compared to the 240, the additional degree,s is all in the initial opening ramp which is much softer in these cams

 

I think the appearance that the intake cam is further retarded is because of the camera angle in my picture. They are pretty close to the same in relation to the notch on cam cap.
The amount shown is about 7 degrees of crank rotation, I calculated centers at 107 ex and 117 intake and overlap of 29 deg as they sit.

 

One point is to make sure you find tdc with a piston stop or at least use the screw driver method in hole 1 so you can see the dwell and know what the overlap is, I have had some on the far side of the timing cover mark. That is a good starting point.

John

 

One point is to make sure you find tdc with a piston stop or at least use the screw driver method in hole 1

I used the dial gauge in hole 1, see it in picture of cams I posted
Might be able to take a drive today without rain.
I will drive them for a while with the settings as pictured (about 7 deg retard both cams) and then make some adjustments from there.

 

That allowed you to read the point where the piston reached the top of its travel and then the point where it started to go down again and then you diveded those two numbers and got true tdc?

You then took true tdc and placed the motor at true tdc and then made your mark on the timing cover?

Where did your true tdc mark end up being on the timing cover?

John

 

With both b202 cams, no adjustments, car is running super good. I think I've cleared up some of my back pressure issues with these cams.

 

By no adjustments, do you mean you just plugged them in with the factory timing marks and called it a day? i thought the deck height difference was suppose to screw up the timing and hence the Stripped/adjustable cam gears?

 

That is good news, my buddy Steve is running those in his 9k with Holset HX 35 and he likes them too, says it really helped with the upper midrange.

Now you need to get that GT28RS Disco Potato on there and you should be running very well and be balanced all at the same time !

John

 

and now you have me contemplating stuffing b202T cams into my 9-5!

remove the tentioner spring, ziptie the timing chain to the cam gears, and swap the cams out?
Sounds fun!

 

Its that easy.