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 1973 96v4 with a modern twist
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 16 Mar 2021 :  11:25:10 Show Profile Reply with Quote
Awesome stuff again Antti! Those drive shafts look the part. I've been messing with a similar size Peugeot 307 fan in front of a 9000 radiator, but your set-up looks to work much better. I'll update my injection thread at some point with some pics.

www.saabv4.com
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AnttiK
V4 Beginner

Finland
64 Posts

Posted - 17 Mar 2021 :  11:56:57 Show Profile Reply with Quote
307 fan might also be a good solution. The 307 fan is probably thicker (85mm?) than Spal 375mm model (51mm) and it might cause some limitations. But in the other hand 307 fan has probably more power.

Last summer when I was tuning the engine parameters I noticed there is always some kind of small ripple in RPM, which will cause some ignition timing ripple and fuel injection pulse ripple. I tried to add some smoothing to the RPM signal, but without significant success. Then I thought that if this has something to do with clearance between balance shaft gear and crankshaft gear. If there is some kind of vibration between the gears it will cause small but noticeable ripple in RPM signal. In that sense the flywheel trigger would be better solution.
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 17 Mar 2021 :  12:07:12 Show Profile Reply with Quote
The timing gears always have a little backlash (otherwise they would lock up), but I wouldn't expect this to cause any issues under load. Not sure what does though. How did you try to stabilise the rpm signal? With the software? I think taking the signal off the flywheel would always be the preferable option, but installing a sensor there is a little more involved than installing a trigger wheel at the balance shaft pulley.

www.saabv4.com
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AnttiK
V4 Beginner

Finland
64 Posts

Posted - 17 Mar 2021 :  12:48:13 Show Profile Reply with Quote
There are smoothing factors in Tunerstudio which make averaging to different sensor readings and those factors can be changed dependent on your system sensor properties. For example if there is noise in the signal, the smoothing can be added to stabilize the values. In the other hand if there is a lot of smoothing in the sensor values the throttle response is not that good.

However the ripple is only about +-30RPM at 2000RPM, so it is not real issue, but it is always interesting to search improvements As a reference I have watched youtube videos of other engine tuners and it looks like they have more stable RPM signal.
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 17 Mar 2021 :  13:10:01 Show Profile Reply with Quote
I hear what you say about throttle response being affected and I agree you want to mess with the signal as little as possible. Would be very interesting indeed to find the cause of the fluctuation, and to separate cause from effect. The issue is apparently only present in a small rpm range, but would it be possible the sensor itself causes it? Or ignition interference perhaps? I'm just shooting from the hip, I'm sure you've already considered my suggestions!

www.saabv4.com
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Derek
V4 Guru

United Kingdom
2019 Posts

Posted - 17 Mar 2021 :  13:31:49 Show Profile Reply with Quote
Can you feel the effects of this ripple when driving the car? I was wondering about the possibility of trigger bracket resonance at that specific speed affecting the signal.
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AnttiK
V4 Beginner

Finland
64 Posts

Posted - 17 Mar 2021 :  13:34:20 Show Profile Reply with Quote
I think the sensor signal is in quite good condition according to toothlogger in tunerstudio. Signal to noise ratio can be seen from it and each individual trigger tooth can be seen from it. But maybe I should look again more deeply about the toothlogger.

Another thing I was thinking that it looks like the balance shaft and pulley are balanced as a pair. At least couple of pulleys, which I have, have different amount of balancing holes drilled. With 1500cc engine I had a pulley from another engine in it, if it makes any difference. And I think adding the weight to pulley with trigger wheel will not improve the balance shaft + pulley -combination balance.
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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 17 Mar 2021 :  14:24:42 Show Profile Reply with Quote
I think you're onto something here. I doubt the balance shaft and the pulley have been balanced together, but it wouldn't be a bad idea to do that. Derek's suggestion also makes sense to me.

www.saabv4.com
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AnttiK
V4 Beginner

Finland
64 Posts

Posted - 17 Mar 2021 :  16:21:40 Show Profile Reply with Quote
quote:
Originally posted by Derek
Can you feel the effects of this ripple when driving the car? I was wondering about the possibility of trigger bracket resonance at that specific speed affecting the signal.



Car is slightly jerking when cruising 40km/h with 3rd gear. I have tried to find the root cause from front brakes and driveshafts. Situation is improved, but I still feel very little jerking.

You are probably right. The trigger bracket is quite solid, but it will probably resonate in some extent. It is definitely worth to try to add some supporting metal to it. Here is an old picture, where structure of the sensor bracket can be seen:



If trigger wheel diameter is about 140mm, then 1 degree step in wheel circle is about 1.22mm. If sensor vibrates i.e. 1.22mm for example in 2000RPM the error caused by vibration is (1/360)*2000RPM = 5.5 RPM.
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Borstlap
V4 Fanatic

Norway
301 Posts

Posted - 19 Mar 2021 :  11:26:50 Show Profile Reply with Quote
Even though the bracket you made looks pretty solid you might get vibrations because it is bolted down quite horizontally. With the shorter fan belt you may not have much of a choice. On the Sonett I have a quite similar setup, but because I haven't shorted the fan belt I was able to attach the bracket vertically. Underneath you'll find the link to my Megajolt project with pictures. On the 96 I put the sensor quite differently as you can see. Bracket as short as possible. Still place for an electric fan. I used a cheapo generic one but I may consider to swap it out for a bigger 9000 fan I have lying about. Don't know yet if that one fits.

Alex
http://www.saab-v4.co.uk/speedball/topic.asp?TOPIC_ID=3795&SearchTerms=megajolt
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AnttiK
V4 Beginner

Finland
64 Posts

Posted - 19 Mar 2021 :  12:58:19 Show Profile Reply with Quote
Thanks Alex, looks like you are using the timing cover fastening bolt closest to the sensor in your installation. If I connect that bolt to bracket with metal flange it will certainly stabilize the vibration. But first I am going to strengthen the existing bracket.
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Borstlap
V4 Fanatic

Norway
301 Posts

Posted - 21 Mar 2021 :  15:58:20 Show Profile Reply with Quote
AnttiK,correct and the next bolt under. I made the positioning of the sensor such that the plate the positioning bolt is screwed into is as short as possible. Not ideal for the electrics connector but less chance for vibrations. The outward connection you used is the dynamo bolt, right? Being on the extreme end of the front plate and connected to a part that is rotating you may have a se source for vibrations there.

Alex
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AnttiK
V4 Beginner

Finland
64 Posts

Posted - 21 Mar 2021 :  17:55:13 Show Profile Reply with Quote
Yes, the alternator bracket fastening bolt closest to the water pump might be the source of vibration. I have now made the current structure much stronger and there should be less vibration to the direction wheel circle tangent, but of course if the alternator bracket bolt vibrates it doesn't much help.

Just to be curious I think I am going to do another sensor bracket using different fastening bolts in a few months. It easy to compare those by monitoring the delta RPM values from log
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AnttiK
V4 Beginner

Finland
64 Posts

Posted - 12 Apr 2021 :  16:52:48 Show Profile Reply with Quote
While waiting the rest of the hub conversion parts to arrive from machine shop I installed the diy rocket shaft spacer with adjusting shims. I think this kind of conversion is quite common with VW bug enthusiasts and also typically used in classic competition cars. And of course there is aluminium body used for rocker shaft strengthening in v4 rally parts, but that is clearly more expensive and complex solution.

Main idea for this was to just reduce some friction and noise caused by middle spring and end springs of the rocker shaft. And maybe little bit more precise operation of valve rockers in high RPM range. When rotating the valve rockers by hand with modified and unmodified shaft there is clear difference in friction.

I have driven 50km with this setup and at least it can be said that performance of the engine is not worse than before

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melle
V4 Guru

United Kingdom
3342 Posts

Posted - 12 Apr 2021 :  17:56:26 Show Profile Reply with Quote
Nice work again! How do you control end float on the shaft? I suppose Ford used springs as a cheap means of making sure the rockers don't bind up when things get hot?

www.saabv4.com
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