# Thread: Unification Theory of all the exhaust cam info

1. (4th preface) 9/1/08
Why?
stock intake has 195 duration and .354" lift
euro cam has 207 duration and .378" lift
exhaust cam has 215 duration and .402" lift

the exhaust cam phased correctly should yeild a bigger intake charge than the euro cam, if the intake system and exhaust flows enough to not cause a restriction.

this will make a cams set pretty close to the TT street set without spending \$380

(3rd preface)5/19/08
read this and look at the pics, these are pics @ 112*lsa not 110* lsa

this quote of myself (I like quoting myself ) pretty much sums up everything
quote:
because I'm lazy and need to go out and swap my ignition distributor, I'm pasting this pm re-hash for all

weeblebiker (2:17 AM 6-7-2007): hehe
k, first, what's your red line?
second, have you looked at the pics and understand how I'm orienting and referencing the cams?
remeber looking at the pics, the cams are spinning counterclockwise advance is counterclockwise, retard is clockwise
rotating the gear 3.6*counter clockwise (which is rotating the cam clockwise or retarding) puts the cam in phase with the intake cam. the stock cam set has a lobe separation of 107* I origenally was shooting for a lobe separation of 112* 3.6* +(112-107)= 8.6* counterclockwise
or 14.4* (tooth seperation angle) - 8.6*= 5.8* clockwise and found this pulled up to my redline 7500 rev limit.

on further research, I found most cam sets of this duration put the lobe separation @ 110*
rotating the cam gear 3.6*+3*= 6.6* counterclockwise. the diameter is 34mm at the gear; 0.2967mm=1* which is shaving 2mm or 1/2 off the key. this should be pretty damn near best for street and stock rev limit, (but will increase overlap and may effect emissions). for you, cutting a new keyway, all you need to do is take this angle offset and add multiples of 14.4* to put the keyway where you want.

and yes decking it will slightly retard the timing, might but not much. to be noticable

weeblebiker (2:20 AM 6-7-2007): as for the new timing mark, set the cam on the counter with the lobes closest to the gear straight up, count 3 teeth up the bottom left and mark the tooth, just like the intake cam your looking at next to it, remeber the intake cam is the reference. when your done the lobe center on the new cam should be slightly clockwise of the intake lobe center

(second preface)
5/31/07 here's pics

(first preface)
don't read this. check 7 replies down for the simple version
Well ok read this for a brief history of the thoughts on this mod
please exuse some of the posts, I was usually writing these in the middle of the night when I was up with my then few week old son
enjoy

(origenal first post beginning)
Bear with me here,

I'm thinking the old 6* or 7.2* retarded legend was in crank degrees, not cam degrees which corisponds quit nicely to the 3.6* cam degree advance to put the exhaust cam mod in phase with the stock intake.

the exhaust cam has a larger duration 215* verses 195 for the stock cam(I know what that really means now ). 180* is the piston moving from tdc to btc or half a stroke. the mod cam in the stock phase position would make the intake valves open a little sooner in the exhaust stroke which isn't really good. but retard the cam and too much and it leaves the valves open longer during the compression stroke which isn't really good either.

I learned a lot from this graph this morning
Thanks jetta2dr!

according to the TT site
http://techtonicstuning.com/camsspecs.asp
the stock phase angle is 107*

for a refresher of the only seemingly legit info on this mod checky here
http://scirocco16v.com/tech/exhaust_cam.htm
which says to put the mod cam at 106* phase angle, which is crank 1* retarded verses stock, or .5 cam degrees

SO,
the exhaust cam mod advanced 3.6 cam degrees or 7.2 crank degrees would have a phase angle of 107and be in the same position as the stock cam. (this looks right by my eyeball)

to decrease the valve overlap to a reasonable amount and not have the intake valve open too long during compression stroke,phase angle of 106* has been suggested. you would move the cam 6 crank degrees, (sound familier?) or 3.1 cam degrees

since the cam gear has 14.4 degrees per tooth, somebody thought 6 crank degrees was cam degrees and was about half a tooth and lead back to 7.2* only as cam degrees (again a familier number from up above?) leading to the "half a tooth off thing everybody states", although entirely wrong.

so I think,

to get the cam mod entirely right,

I will advance the cam 3.1 cam degrees (as close as I can) by rotating the cam gear 3.1* counter clockwise. this also make 106* phase angle.

to "Install them with a 106 degree peak opening point on both symetrically", I'll advance both cams .5 crank degrees or .25 cam degrees with the timing gear. which makes sense cause you want the overlap centerd over TDC.

or

discuss

Modified by weeblebiker at 6:08 PM 3-19-2006

Modified by weeblebiker at 11:26 AM 3-22-2006

Modified by weeblebiker at 11:43 AM 11-7-2006

Modified by weeblebiker at 3:19 AM 6-1-2007

Modified by weeblebiker at 3:30 AM 6-1-2007

Modified by weeblebiker at 3:33 AM 6-1-2007

Modified by weeblebiker at 1:17 AM 8-11-2007

Modified by weeblebiker at 1:18 AM 8-11-2007

Modified by weeblebiker at 1:49 AM 5-20-2008

Modified by weeblebiker at 1:54 AM 5-20-2008

Modified by weeblebiker at 1:55 AM 5-20-2008

Modified by weeblebiker at 12:15 PM 9-1-2008

Modified by weeblebiker at 12:23 PM 9-1-2008

Modified by weeblebiker at 6:59 PM 9-16-2008

Modified by weeblebiker at 3:43 PM 1-17-2009

Modified by weeblebiker at 4:15 PM 1-17-2009

2. To do the cams like the scirocco16v.com link says with the 106* LSA you need to move both cams since it says to set them up symetrically. There is also the lobe centerline which is where the peak opening occurs, in ATDC for intake and BTDC for exhaust. The LSA is the distance in degrees between each cam's centerline. Stock intake cam has a centerline of 102* ATDC, stock exhaust cam is 112* BTDC, which gives a LSA of 107*. I find, from graphing different timing configurations, that setting the intake cam centerline at 112* ATDC and the exhaust cam stock the cam curves overlap almost exactly with the Techtonic's Street Cams, although with lightly less lift.

3.  Quote, originally posted by Jetta2dr » To do the cams like the scirocco16v.com link says with the 106* LSA you need to move both cams since it says to set them up symetrically. There is also the lobe centerline which is where the peak opening occurs, in ATDC for intake and BTDC for exhaust. The LSA is the distance in degrees between each cam's centerline. Stock intake cam has a centerline of 102* ATDC, stock exhaust cam is 112* BTDC, which gives a LSA of 107*. I find, from graphing different timing configurations, that setting the intake cam centerline at 112* ATDC and the exhaust cam stock the cam curves overlap almost exactly with the Techtonic's Street Cams, although with lightly less lift.

you can advance/retard both cams by moving the timing gear on the exhaust cam.

maybe I meant lobe separation angle instead of phase angle. only been at this since 7 this morning

with that, do you see anything wrong with my analysis?

You throw in an interesting twist at the end. I take it you are talking about setting the modded exhaust cam as an intake at 112* ATDC. so you say retarding the the cam, turning the cam gear 1.4* clockwise from the drivers side. and rotating the whole thing 6 teeth. will give a lobe separation angle similar to TT's?

4. IIRC, the Scirocco16v.com thing says to retard the intake intercam timing slightly, and advance the cams a bunch

5. how do you get that from the info?

and jetta2dr, now I'm at a quandry.

6. I've reread and recalculated things lots, and I'm still kinda confused on all of it. But just recently I got a base for my dial indicator, so hopefully next weekend I can measure up the exhaust cam and figure it all out. But then I dont really know enough about cam theory to know where is good to set it. Thats why I was leaning twords a 112* centerline on it because the curves matche the TT street set which we know works. When in doubt, copy someone else!

7.  Quote, originally posted by Freerevving » IIRC, the Scirocco16v.com thing says to retard the intake intercam timing slightly, and advance the cams a bunch

oh yeah it doesn't say that at all

8. nevermind, my first post was sleep deprived ramblings from staying up with the baby.

simple form:

the exhaust cam is 3.6* advanced from intake cam lobe center.(I trust the sourceand looks right by eyballing)
the lobe center is 5* advanced from where the exhaust cam should open to mimmick the TT cam set. (I trust this source and looks right by eyeballing also)

this is 8.6* advanced or 14.4*(tooth angle)-8.6* is 5.8* retarded (or rounded to 6*)

or
the diameter is 34mm at the gear; 0.2967mm=1*
shave/ buy 1.7mm off set key and turn the gear clockwise relative to the cam and make your mark six teeth (not counting the tooth with the origenal mark and counting the final tooth you will mark ) clockwise from the origenal mark. (this looks right by eyballing also)

by "eyeballing, I mean laying an unmodified exhaust cam, a stock intake, and a modified exhaust an a table with the lobes closest to the gear pointed (as close to) straight up next to each other.

gunna check out the lathes and dial indicators at work....

Modified by weeblebiker at 11:55 AM 3-22-2006

9. so screw ya'll

just put the cams on a degree wheel and mill.centered the cam under the indicator on a bearing surface. set 0.0* to the center of the nearest tooth. moved the indicator over to the nearsest lobe. all angles referenced looking at the distributor side

stock intake: max lift is 0.6* +/- 0.1*counterclockwise from the tooth.
stock exhaust: max lift is 4.0* +/-0.1*counterclockwise from tooth.

maybe 3.6* is right

I did not verify if max lift is lobe center. but I did eyeball the gauge needle was on/near lobe center.

I didn't get a chance to get the opening and closing angle of the cams. maybe later this week. but I trust TT's #'s

hey, I got wife and kids to get home to! (that too!)

actually I'll compare valve opening angle and 0.05mm and 0.1mm lift and 1mm to verify TT's #'s. relative to the same tooth. cause the closing doesn't matter as much, right?

oh by the way. my new job rocks!

Modified by weeblebiker at 12:42 PM 3-23-2006

Modified by weeblebiker at 12:44 PM 3-23-2006

10. so the exhaust cam is 136* opening to close (68* to max lift)and 90* 1.0mm to 1.0mm (45* to max lift).

more to come

hey is someone willing to host a pick of my setp? (I got better things to do besides setting up a pic account)

btw all degrees are cam degrees, 360*= one revolution of the cam

it's 1mm lift, not 0.1mm lift. gotta read the gauge right

Modified by weeblebiker at 3:33 PM 3-25-2006

11. Cool stuff, dude Im glad someone is actually measuring it up and posting what they get. Hopefully I'll get a chance to do so myself one of these days.

12. Take the .sized off the end if you want supersized

13. Thanks powerdubs!

I'm gunna redo the max lift/lobe center to nearest tooth measurements. the gauge only goes down to 0.01mm and is only registering the 0.5* around lobe center(dang dwell). so I guestimated midway of where the gauge topped out and eyeballed it to make sure.

gunna try and get a more accurate gauge mounted up.

14. so, my #'s are not acurate.

I cannot get the cam to run true in the degree wheel. and the dwell around lobe center is giving me problems

I need to fab a holder around the last cam bearing on the end for support and stick the cam in a carrier to get accurate readings.

I'm thinking an aluminium donut bigger than the cam lobe cut in half

15. get yourself one of these handy dandy arms

16. what's that got to do with figuring the angle offset?

well I gust inatalled my first cam again that I thought I buggard. I didn't know what I was doing and retarded it 7.7*ish (from origenal keyway) and tryed running it at 7 teeth.

but at 6 teeth it should be 4.1* ish retarded from the exhaust phased with the intake. according to the theory and my eyeball.

and to think this was sitting in the trash can for 20 minutes before I fished it back out.

it should rip kinda hard I hope. I'm thinking my power should come on a little sooner than 4k. I want the powerband lower for autocross

Modified by weeblebiker at 6:07 AM 3-25-2006

17. so I started it this morning, sounds throaty and had a little trouble idling. gunna open up the bypass a little.
---------
just got back. thought "screw it, the babies asleep in the swing and the older boys are up. so I took it out.

opened up the bypass about a turn and the idle smoothed out nicely. good to know it actually needs more air to idle at the same rpm.

so power comes on about 3200 rpm smooth held up to 6800rpm. any power loss up top was smooth and not really noticable. hit a cut off @7200 not 6800(My tach reads 6800 but my megasquirt reads 7200) then I'll see where the power stops up top. for street driving overall an invisably smooth power increase that is noticable but not incredable no sudden "kick in the pants". well worth the effort for diy'ers . Not something I'd drop more than \$100 on at this point for the increase power, but I'm a freaking tight wad.

gunna do a little more tuning and see if I can squeeze more out of the setup.

so that is my cam that I turned the gear 2.2-2.5mm clockwise at the keyway put in a 2L engine with a 2Lhead running cis-e and fuel mod.

now to decide what to set the next one at. but I may megasquirt before I set the next cam. I think that may give me more top end than a slightly more retarded intake cam phase to reduce the overlap.

maybe we just need to start a thread with settings and reviews of the results for this mod

hey jetta2dr, could you send me some charts? pm sent

Modified by weeblebiker at 2:58 PM 3-25-2006

as of 4/11/07 I have this cam back in my car with megasquirt, Gtech and going to be tuning with a wideband.

Modified by weeblebiker at 12:52 AM 4-13-2007

18. This is what I get by averaging my results of 5 runs. duration #'s very good since I measured from change in displacement. tooth to lobe center not as acurate because of dwell and cam not perfectly true in collet. The intake tooth IS clockwise of lobe center.
by not accurate i mean +/- 0.25*

exhaust: 136* open to close, 90* 1mm to 1mm, tooth about 4* clockwise of lobe center.

intake: 122* open to close, 80* 1mm to 1mm, tooth about 0.5*clockwise of lobe center.

inner diameter of tming gear is 34.0 mm.
1* offset at the woodruff key is 0.2967059728mm.

Also the exhaust has more dwell around lobecenter than the intake.

do with it what you will

Modified by weeblebiker at 4:50 PM 3-25-2006

Modified by weeblebiker at 9:31 AM 3-26-2006

19.  Quote, originally posted by weeblebiker » what's that got to do with figuring the angle offset?

My bad... I guess I misread.. I figured you were having problems with the way you were trying to hold everything and read measurements.. I thought you could just slap a cam in a spare head so it would be stable and use an arm like that to mount the gauge..

20. Powerdubs, sometimes I don't know about you

The thing I'm reading in my pic is the big round thing with the crank the cam is sticking out of. all the dial indicator does is tell me change in displacement from the center of the cam. It really does not matter what the number is on the dial indicator, except for the 1mm lift measurements.

so I took it out before bed time and drove it @ wot. and it kinda rips pretty hard actually. I didn't do any launches but it was struggling to maintain traction on dry pavement all through 2nd and most of 3rd. on my cheap falkins and shim kit 3.95 tranny

21. the car has more torque off idle too. I can work the clutch starting in first like I do when I shift from second to third. I also got going from a stop by just letting out the clutch at idle.

I just used the mill like it was supposed to be used this afternoon and cut 1.72mm off the side of a key.....

22. so now I'm sitting here with a cam advanced 5.8*
shaved the key, pressed it together, brazed the cavity.

just have to drop it in some time soon

23. i got my gear about 2.5mm clockwise and it really rips all the way up to 7500, kick on hard at about 4k

24.  Quote, originally posted by vwgli16vracer » i got my gear about 2.5mm clockwise and it really rips all the way up to 7500, kick on hard at about 4k

25. ok, i have an 88 gli with almost 250k on the original 1.8 16v, ttt exhaust, modified exhaust cam, euro cis, lightened alloy pulleys, right now an 8v knock box wich i don't like but it's all i have till i find a new 16v one. i'm swapping in a 2.0 shortblock and low mileage 1.8 head along with a header, cemterforce clutch and lightened flywheel. here's a pic of where i filed the new ketway in my gear

i put the keyway right between the 2 teeth and now i use the fifth tooth from the dot to line up the cams, i might play with a few more gears to see what happens but it looks like you gaot it under control so i might just wait and see what you end up with

Modified by vwgli16vracer at 1:51 PM 3-29-2006

26. that looks like alot more than 2.5mm. what was the measurement left side of old to left side of new keyway? and how did you figure it was about 2.5?

2.5mm retarded is about the same as 1.7mm advanced minus a tooth

I'm wanting an autocross cam maybe I should go ahead and melt out the brazing and cut another key at 1.5mm.

oh well, I'll just go ahead and cut a new key. and make another cam

then I'll have a 4*, 5* and 6* cam

er retarded from lobe center if placed in phase with the intake cam.

Modified by weeblebiker at 11:44 AM 3-30-2006

27. well i must of had a lucky guess when i cut mine. my car now hangs with my buddy's 200 hp vr6 b3 passat. before he pulled away pretty good.

28. well my 1.72mm advanced cam is going in tonight.

29. Let us know how it runs.

30. it runs very well
idle is good, sounds a little throatier than stock. 1mm open is in the same position as the stock cam so no idle problems.

not quite as much torgue off idle and up through 3k as the other cam with 1* more overlap, but more than the stock cam.

you can feel it come on stronger from 3-4k rpm and stays strong up to 6800 rpm.
feels like it should hold past that also.

so 1.72mm off the side of the key. any machine shop with a digital mill can do it. orient so the gear is twisted clockwise and press it back on. stick it in the oven @ 550* stick it in a vice and heat the gear all the way around with a propane torch for a while untill you get solder to melt in the gap. the solder will braze the gear to the cam plus it is reversable if you want to do something like reduce overlap for boost

put the new timing mark 6 teeth clockwise from the old mark.

31. Ok, I was finally able to degree an exhaust cam on the intake side in the head. I think my figures are fairly accurate, as I was able to reproduce them with a difference of about 2%.
So these are the specs for the exhaust cam at 6 teeth exactly:
-15 BTDC IVO @ .050"
50 ABDC IVC @ .050"
122.5 LC

To get the cam timed with a 112 lobe center (to be symetrical with the exhaust cam, and timed very similarly to the TT street cams) you would have to advance the cam 10.5* from 6 teeth, which is 5.25* at the cam (cause of the whole twice spinny thing, you know.) Not saying this timing is ideal, but from what I can tell it would be a good starting point since its similar (opening and closing times) to the TT street cams, which are proven.

Maybe someday I'll actually do this mod

32. interesting, so the TT set has less overlap than the stock set?

I'm dealing with oil pressure gauge and oil buzzer issues now

33. I guess they do have a little less overlap, but TT says the cams are based off of the ABF cams, so maybe thats why.

Sucks about the oil pressy issues.
I'll see how far I get into trying my cam setup this weekend.

34.  Quote, originally posted by Jetta2dr » Ok, I was finally able to degree an exhaust cam on the intake side in the head. I think my figures are fairly accurate, as I was able to reproduce them with a difference of about 2%.So these are the specs for the exhaust cam at 6 teeth exactly:-15 BTDC IVO @ .050"50 ABDC IVC @ .050"122.5 LCTo get the cam timed with a 112 lobe center (to be symetrical with the exhaust cam, and timed very similarly to the TT street cams) you would have to advance the cam 10.5* from 6 teeth, which is 5.25* at the cam (cause of the whole twice spinny thing, you know.) Not saying this timing is ideal, but from what I can tell it would be a good starting point since its similar (opening and closing times) to the TT street cams, which are proven.Maybe someday I'll actually do this mod

122.5 LC, wouldn't that make it a decent boost cam?
Tightening the lobe center angle produces more overlap around TDC and wider angles mean less overlap.

35. I dont know, it may work well for boost. Since the stock exhaust cam closes at -4.5 BTDC, and the modified exhaust cam as an intake would open -15 BTDC, so there is no overlap at all.

I basically just wanted to get the actual numbers out there so that people can try different setups and actually know what their cam timing is, instead of guessing or making assumptions.

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