need help with scr dcr
Veteran
Joined: Oct 2005
Posts: 1,284
Likes: 81
From: Nashville, TN
That difference is probably because ... either ... they expect you to install it 4* advanced at 69* or it is ground w/ 4* advance.
Please state ALL adv/sae cam specs from mfg ... and separately
ALL adv/sae cam specs that you input and were returned from the "good" dcr calculator.
Please state ALL adv/sae cam specs from mfg ... and separately
ALL adv/sae cam specs that you input and were returned from the "good" dcr calculator.
CAM HR-284-2S-12 IG
284/292 adv duration
222/230 duration @.050
.509/.528 lift 1.5 ratio
.543/.563 lift 1.6 ratio(figured for my 1.6 RR)
intake lift @ cam 339
exhaust lift @ cam 352
.004 cam timing
opens closes
intake 31 BTDC 73 ABDC
exhaust 79 BBDC 33 ATDC
@.050 timing
opens closes Max lift(centerline)
intake 4 BTDC 38 ABDC 107 ATDC
exhaust 52 BBDC 2 BTDC 117 BTDC
now the good calc
Cam timing and overlap calc:
284 intake adv dur
292 exhaust adv dur
112 lobe separation
107 intake lobe centerline
Results:
Seat timing
opens closes
intake 35 BTDC 69 ABDC
exhaust 83 BBDC 29 ATDC
Overlap 64 Tot cam adv 5
Dynamic Stroke length calc:
3.75 stroke
5.7 rod
69 adv intake valve closing angle
results:
2.82237741276584 dynamic stroke
0.9276 distance of piston from BDC
compression ratio calc
8 cylinders
4.030 bore diameter
3.75 stroke
60 comb ch CC
.026 gasket thick
4.1 gasket bore
18 dished piston cc
Results:
.042 quench
382.6 displacement ci
6.2 displacement Lt
10.01 static CR
7.78 dynamic CR
Veteran
Joined: Oct 2005
Posts: 1,284
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From: Nashville, TN
Le Mans Master
Joined: Sep 2001
Posts: 7,739
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From: Unreconstructed, South Carolina
Rich:
where's the CORRECT LSA????? ... that's from mfg ... you input LSA ... calc does NOT return it ... you input that.
Also ... what ICL is it ACTUALLY installed at?
Also ... add about 2*-3* to duration when running 1.6:1 RAR.
-edit- AFAIK ... ICL + ECL / 2 = LSA ... so I'd go with 107 + 117 / 2 = 112 OK ...
where's the CORRECT LSA????? ... that's from mfg ... you input LSA ... calc does NOT return it ... you input that.
Also ... what ICL is it ACTUALLY installed at?
Also ... add about 2*-3* to duration when running 1.6:1 RAR.
-edit- AFAIK ... ICL + ECL / 2 = LSA ... so I'd go with 107 + 117 / 2 = 112 OK ...
Last edited by jackson; Feb 16, 2007 at 06:20 PM.
Veteran
Joined: Oct 2005
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From: Nashville, TN
It is installed at ICL 107, LSA is 112. Crane doesn't put ICL on there cam card, it is labeled as 107 max lift but it is the same, I found this out on Cranes tech web site last night. changing to 287/295 duration changed everything. Drops DCR to 7.68. Moved all the seat values 1.5. Using comp cams desktop dyno advanced it gives me an overlap of 67. Also the desktop dyno numbers match the the GOOD DCR calculators cam calculations perfectly. According to the desktop dyno I should hit 524 HP @ 6000 RPM and 507 TQ @ 5000 RPM. Somehow I think that is a bit high myself.
Last edited by King Lear; Feb 16, 2007 at 06:41 PM.
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
@ stock rocker 284/292 returns 69* ICA & 7.7834 ...dcr
the 1.6 rockers lower dcr about 0.6
BTW ... rockers do not change lsa ... but they do change dur
Veteran
Joined: Oct 2005
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From: Nashville, TN
We must have something different in it, I just did it and came up with 7.71 dcr at 286/294. same 70 ICA,
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
Le Mans Master
Joined: Sep 2001
Posts: 7,739
Likes: 630
From: Unreconstructed, South Carolina
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Veteran
Joined: Oct 2005
Posts: 1,284
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From: Nashville, TN
Veteran
Joined: Oct 2005
Posts: 1,284
Likes: 81
From: Nashville, TN
Veteran
Joined: Oct 2005
Posts: 1,284
Likes: 81
From: Nashville, TN
Just for kicks I figured out what my builder has it at right now before he changes heads, gaskets, etc. I am at a power building 9.31 static and DCR of 7.26. This is exactly what you said before Jackson, many a turd motors have been made using the KB figures. He went off of Eagles catalog figures, oh well, at least he is fixing his errors and is going to make it right once the snow goes away!
Racer
Joined: Oct 2004
Posts: 285
Likes: 0
From: Stockholm
I downloaded the DCR Calculator, but there must be something wrong with the code.
If I set all values and then calculate my static comp I get 11.3 (KB 11.2) so far everything is ok.
But when I then checks the box for dyn comp and refresh I always get 9.3 It doesn't matter what IVC timimg I set, and even if I change the cam values totaly, it gives me 9.3 in dyn comp.
There must be a bug in that pgm!
If I set all values and then calculate my static comp I get 11.3 (KB 11.2) so far everything is ok.
But when I then checks the box for dyn comp and refresh I always get 9.3 It doesn't matter what IVC timimg I set, and even if I change the cam values totaly, it gives me 9.3 in dyn comp.
There must be a bug in that pgm!
Last edited by gbak; Feb 17, 2007 at 04:48 PM.
Drifting
Joined: Apr 2002
Posts: 1,716
Likes: 4
From: New Baden Illinois
I cannot seem to get it either. My SCR is 9.971 and when I check the box for dynamic stroke, it only changes it to 9.405. It is with the Crane Powermax 272 (272/284; 107 ICL? and 112 LSA)
Veteran
Joined: Oct 2005
Posts: 1,284
Likes: 81
From: Nashville, TN
I downloaded the DCR Calculator, but there must be something wrong with the code.
If I set all values and then calculate my static comp I get 11.3 (KB 11.2) so far everything is ok.
But when I then checks the box for dyn comp and refresh I always get 9.3 It doesn't matter what IVC timimg I set, and even if I change the cam values totaly, it gives me 9.3 in dyn comp.
There must be a bug in that pgm!
If I set all values and then calculate my static comp I get 11.3 (KB 11.2) so far everything is ok.
But when I then checks the box for dyn comp and refresh I always get 9.3 It doesn't matter what IVC timimg I set, and even if I change the cam values totaly, it gives me 9.3 in dyn comp.
There must be a bug in that pgm!
Veteran
Joined: Oct 2005
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From: Nashville, TN
Melting Slicks
Joined: Jul 2005
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From: winter haven florida
St. Jude Donor '12
i was having the same problem and realized i was putting the wrong numbers in. i was was using .050 numbers instead of the seat to seat numbers. i am comming up with 7.9 dcr now. i was using 44* abdc instead of 69* in mine. also once again if you were to add 15* to the 44* abdc figue at .050 it comes out to 59* so that explains why i was not able to make sense of the other calcs having such high dcrs. that kb calc is crap. thanks to a quick reply from jackson i figured out what my problem was when i looked at my cam card a little closer.
Racer
Joined: Oct 2004
Posts: 285
Likes: 0
From: Stockholm
King Lear can you take a look at my cam to?
I'm using the 0.015 numbers, but is that wrong?
I'm running flat top Probe SRS pistons, with a Trick Flow 64 cc head.
I have a Comp Cams XE274 12-770-8 but I'm looking at a XE280 just to bleed of some dcr.
I'm using the 0.015 numbers, but is that wrong?
I'm running flat top Probe SRS pistons, with a Trick Flow 64 cc head.
I have a Comp Cams XE274 12-770-8 but I'm looking at a XE280 just to bleed of some dcr.
Last edited by gbak; Feb 18, 2007 at 06:03 AM.
Veteran
Joined: Oct 2005
Posts: 1,284
Likes: 81
From: Nashville, TN
My only question is the deck clearance you give is .015. Are you sure this number is correct? The builder should have the deck clearance documented for your build. If you went to a .040 head gasket you will be at 8.8 dcr and 10.9:1 SCR. However, you have a nice trick flow aluminum head. The aluminum head cools much more rapidly then an iron head. Therefore, depending on opinions an aluminum head reads about .5 CR lower internal engine signal then an iron head. So with this in mind your 9.1 dcr is actually reading as a 8.6 dcr in engine signal. So in theory you should be fine!
Racer
Joined: Oct 2004
Posts: 285
Likes: 0
From: Stockholm
I just ran your #'s and came up with a dcr of 9.10889868621097 and static CR of 11.2609317466645.
My only question is the deck clearance you give is .015. Are you sure this number is correct? The builder should have the deck clearance documented for your build. If you went to a .040 head gasket you will be at 8.8 dcr and 10.9:1 SCR. However, you have a nice trick flow aluminum head. The aluminum head cools much more rapidly then an iron head. Therefore, depending on opinions an aluminum head reads about .5 CR lower internal engine signal then an iron head. So with this in mind your 9.1 dcr is actually reading as a 8.6 dcr in engine signal. So in theory you should be fine!
My only question is the deck clearance you give is .015. Are you sure this number is correct? The builder should have the deck clearance documented for your build. If you went to a .040 head gasket you will be at 8.8 dcr and 10.9:1 SCR. However, you have a nice trick flow aluminum head. The aluminum head cools much more rapidly then an iron head. Therefore, depending on opinions an aluminum head reads about .5 CR lower internal engine signal then an iron head. So with this in mind your 9.1 dcr is actually reading as a 8.6 dcr in engine signal. So in theory you should be fine!
I will yse a 0.029 gasket.
Did you use a 0.039 gasket to get these numbers?
If I retard the cam 4*, how will this affect the dcr?
Anyway I have decided to go for the bigger XE280 cam, just to be on the safe side with the dcr.
If I type in the XE280 values, I get the same dcr, very strange!
Should change, as the IVC is different!
Last edited by gbak; Feb 18, 2007 at 02:24 PM.
Race Director
Joined: May 2005
Posts: 10,674
Likes: 122
From: Millington Illinois
St. Jude Donor '08-'09
Ok, Thanks for those that offered to help! Her is my info: Crank Stroke 3.75, Rod length 6", ADV intake closing angle ??????? Intake duration 287, exhaust duration, 293, LSA 114, ICL 110, Int. Open 8, Ex. Open 59, int. closed 48, ex. closed 3, Bore diameter 4.030, stroke 3.75, head CC 74, gasket thickness .040, gasket bore 4.060, deck height 0.00, flat top pistons with 5 cc valve relief, quench .040. If any more info is needed let me know! If possible check advanced 4 and retarded 4. Thanks Kevin