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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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 Posted: Fri Feb 18, 2011 7:38 am Post subject: |
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| flosho wrote: | Whats the deal on those camshafts... I read all that but do not understand.  |
I just got carried away , simplified and in short:
The valve has got one important dimension - circumference. The cam adds the second dimension - lift. Together they make the curtain area. Add duration and you got the timearea, one of the most important factors to make power.
In a perfect world you want full lift from TDC to BTC. But that is impossible with a rotating mechanical camshaft. It looks more like a half sinewave. With one large valve or several small you can improve the circumference part in the equation. We donīt have that option, but if we can improve the lift capabilities it is almost as good. More duration have itīs disadvantages. Max lift and flow usually occurs at 108°-112° ATDC. Ok, that was the flow of the head.
Now we have to look at what it is that makes the flow. It is the piston going from TDC to BDC creating a vacuum pulling the air into the cylinder.
The flow demand is highest at 75° ATDC. And if the head canīt provide the numbers that the piston demands there is a loss. That is why it is so important to have large area early e.i. larger valve and higher lift.
An advertised camduration doesnīt tell half of the story, same thing with max lift. Old cam profiles tend to look triangular and modern more square, with the same duration and lift. With a completely different timearea and maximum output.
This is why cams with tight LSA makes more power that wide ones. More lift early. (there are other factors as well like overlap and scavenge..). This is why 16V makes more power, this is why bore gives more power than stroke. More valve area. This is why hot cams makes power, more lift early.
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Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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Min
Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada
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| Posted: Fri Feb 18, 2011 10:41 am Post subject: |
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| gegge wrote: | | What I can do is buy one single 39mm follower and send it to one of you guys on my expense to check quality and hardness. |
I'm interested in a set. What kind of material are they made from? surface coatings? finishes?
Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting. |
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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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| Posted: Fri Feb 18, 2011 9:41 pm Post subject: |
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The steel is treated 4340:
http://www.interlloy.com.au/data_sheets/high_tensile_steels/4340.html
He is going to conduct a Vickers Hardness Test and get back to me.
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Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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MikeJinCO
Joined: 08 Jun 2010
Posts: 1245
Location: Maysville, Colorado
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| Posted: Fri Feb 18, 2011 10:50 pm Post subject: |
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I vaguely recall that some of the later motors with similar types of valve arrangements had some type of cam follower rotator designed into them in order to reduce the wear on the follower. Although I have no idea if or how it worked. I know that my old Alfa did not('57). Can anyone expand this a little.
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Mike
'67 MG Midget Dp
'71 Ocelot Dsr Kawasaki 1000(under rebuild) |
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Sat Feb 19, 2011 4:14 am Post subject: |
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I am interested now in any possible cam choices gegge can get us  !
Also, if the 4340 is hard enough for my taste I will likely send out a set for DLC coating as well. Always experimenting....
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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Martijnus
Joined: 29 Dec 2006
Posts: 2019
Location: Netherlands
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| Posted: Sat Feb 19, 2011 10:06 pm Post subject: |
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I'm surely in for a set!
I'll keep contact with you by PM gegge.
Got a few questions:
Will it be based on Min's drawing?
This:
How about the shims? Are those dimensions the same as in the drawing?
I assume those aren't supplied with the lifters. For me it isn't a problem (they look like Alfa Romeo shims, but those are a mm larger in OD) I have access to almost all OEM style shims... it would be great if it is a widely available size (in other words, using shims from a standardized manufacturer instead of custom ones which need to be machined everytime)
Interesting info by gegge anyway about the timings etc.
Remember this is calculated for peak power, that's what tuning is about.
In my case I want the car to be driveable since I'll almost never redline it, but for a true racer you don't give a shit about driveability.
My findings are counterintuitive... I'm focusing on torque and putting in 'thick' valve seats which create a venturi effect at the seat can increase torque a lot. That's what VW applies on 'modern' 8v heads, looks weird and counter intuitive, but it works. Not sure if this is the right move to make when you intend to go red line all the time.
The same with the camshafts... remember that most of the time, the increase you get in some rpm band, will mean a decrease in another rpm area. If it's your daily driver, I wouldn't advise to focus too much on top end power.
Hasn't much to do with the lifters though 
I like where this is all going. I'm still building my turbo engine and still haven't got a car to put the stuff in. When I'm done modifying my pimp ass stock conrods I can finally start putting some parts together.
| MikeJinCO wrote: | | I vaguely recall that some of the later motors with similar types of valve arrangements had some type of cam follower rotator designed into them in order to reduce the wear on the follower. Although I have no idea if or how it worked. I know that my old Alfa did not('57). Can anyone expand this a little. |
You mean some sort of rocker arm with a roller in it? If there's sufficient lubrication, there shouldn't be much trouble/wear with the stock system. I've seen dents, but haven't traced the source of that problem.
I don't like the rocker systems. They seem fragile to me and heavy
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"Rule: Turbo's make torque, and torque makes fun." (C. Bell)
924 "50-jahre", 1981.
MSII/extra, LPG, ITB's, 5lug.
To be turbo'ed in a while.
Killed her at the Nurburgring, Porscheless at the moment  |
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engineer.white
Joined: 19 Aug 2008
Posts: 61
Location: New Bern, North Carolina
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| Posted: Mon Feb 21, 2011 2:28 am Post subject: Set o lifters |
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I would like a set of these solid lifters as well, where do we turn for the lash adjustment pallets? Is the manufacture of these also being discussed? Regardless I am in for a set of lifters.
David
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1981 924 turbo/931
1982 924 turbo/931
1986 911 turbo/930 |
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Min
Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada
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| Posted: Mon Feb 21, 2011 11:03 am Post subject: Re: Set o lifters |
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| engineer.white wrote: | I would like a set of these solid lifters as well, where do we turn for the lash adjustment pallets? Is the manufacture of these also being discussed? Regardless I am in for a set of lifters.
David |
Lash caps should be obtainable locally. I got a set from my local parts store.
Min
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Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting. |
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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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| Posted: Tue Feb 22, 2011 6:33 pm Post subject: |
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I have recieved money from:
* Mike9311 - 2 sets
* tyfighter123 - 2 sets
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Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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Min
Joined: 04 Nov 2002
Posts: 2368
Location: Vernon, British Columbia, Canada
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| Posted: Wed Feb 23, 2011 4:57 am Post subject: |
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Any response on hardness testing yet?
Min
_________________
Custom means it didn't come from a box.
1980 n/a with EDIS and Megasquirt II Injection. 7 different colors and counting. |
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flosho
Joined: 01 Jul 2004
Posts: 3160
Location: Eau Claire, Wisconsin
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| Posted: Fri Feb 25, 2011 7:12 am Post subject: |
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I'll be sending payment tomorrow afternoon.
Now I just need a new camshaft to use these with...
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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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| Posted: Fri Feb 25, 2011 7:47 am Post subject: |
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| Min wrote: | Any response on hardness testing yet?
Min |
He was supposed to conduct the test today, but I havnīt heard from him. Will remind him tomorrow.
EDIT: Called him today but he was busy buying a company. Monday it is.
_________________
Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs
Last edited by gegge on Sat Feb 26, 2011 2:12 am; edited 1 time in total |
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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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| Posted: Fri Feb 25, 2011 10:31 pm Post subject: |
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If you doubt the quality of Sten Parner why not order from Arrow? I made a simple request for 10 sets of specialmade nitrided 924 followers and got this reply(available in different coatings and finish):
Hello Fredrik,
Thank you for contacting us.
The cost to produce an 80 off would be Ģ14.00 GBP per cam follower + carriage and VAT.
I will have to ask if we can use the drawing you have supplied.
If we cannot use your drawing, then it will take a week or two to have a drawing completed.
Once the drawing is approved, we will need a 25% deposit to start production.
Production itself will take up to 6 weeks.
If you have any other questions, please do not hesitate to contact me.
Kind regards
Aaron
Aaron Paul Smith
Technical Sales
Arrow Precision Engineering
Tel:+44 (0)1455 234200
Fax: +44 (0)1455 233545
email: aaron.smith@arrowprecision.com
web: www.arrowprecision.com
Winners of 'Best Technical Innovation' award
Autosport Engineering 2011
I provided the PIPER drawing that Min made, but Arrow prefer a different design similar to the Sten Parner follower. Look and the conical shape of the roof, large radius to the tap and reinforced skirt. These are usually lighter, expect 45g (The picture show a BMW S14 M3 follower from arrow)
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Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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Mike9311
Joined: 14 Dec 2004
Posts: 1798
Location: Chicago-ish
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| Posted: Sat Feb 26, 2011 3:59 am Post subject: |
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Hey Min...Look familiar?!?!
Min and I have been going back and forth via email and I drew this design up in CAD a week ago almost exactly the same using the gegge ring idea and Mins drawing to start. The ring though for me was for stability during hardening given the material choice. Min questioned spring clearance with the ring which I had not thought of and would have had to check.
My version using Mins material choice density was at 47-48g
_________________
1980 931 since 1989
1981 Ideola 931 Club Sport
1982 931 Entwicklungsfahrzeug
1979 924 NA ohne 650 mit 471
1982 931 Red Resurrection - 951 IC
1982 931 parts car / resurrection?
1980 924 NA (R&D lightweight)
1982 931 wana-be GTR race car |
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| Back to top |
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gegge
Joined: 27 Jul 2007
Posts: 1124
Location: Sweden
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| Posted: Sat Feb 26, 2011 7:08 am Post subject: |
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If I remember correct is the outside spring diamter 34mm. The thickness of the ring should be about 1mm making an inside diameter of 36.50mm.
_________________
Carl Fredrik Torkildsen
924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs |
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