Advance or Retard the cam?

Advance or Retard the cam?

Author
Discussion

845ste

Original Poster:

577 posts

126 months

Monday 13th March 2017
quotequote all
ciao a tutti,
i have a complete kit Comp-Cam with the Possibility to adjust the advance or retard from a minimum of 6 ° to a maximum of 6 °
Here I would ask you if someone has tried.

I use my GTR on the track and then try more hp biggrin ... with 7000rpm max.

I have already moved to the 1° retard and it seems that the gtr beyond 4500rpm ,rise more rpm faster.

At low rpm I have not noticed any difference.
Researching more hp ... I wanted to push myself to the maximum position: retard 6°.

what do you think please? smile
thank you .
ste

F.C.

3,896 posts

207 months

Monday 13th March 2017
quotequote all
845ste said:
ciao a tutti,
i have a complete kit Comp-Cam with the Possibility to adjust the advance or retard from a minimum of 6 ° to a maximum of 6 °
Here I would ask you if someone has tried.

I use my GTR on the track and then try more hp biggrin ... with 7000rpm max.

I have already moved to the 1° retard and it seems that the gtr beyond 4500rpm ,rise more rpm faster.

At low rpm I have not noticed any difference.
Researching more hp ... I wanted to push myself to the maximum position: retard 6°.

what do you think please? smile
thank you .
ste
The only way you will really know is on a dyno.

BobE

605 posts

180 months

Monday 13th March 2017
quotequote all
F.C. said:
845ste said:
ciao a tutti,
i have a complete kit Comp-Cam with the Possibility to adjust the advance or retard from a minimum of 6 ° to a maximum of 6 °
Here I would ask you if someone has tried.

I use my GTR on the track and then try more hp biggrin ... with 7000rpm max.

I have already moved to the 1° retard and it seems that the gtr beyond 4500rpm ,rise more rpm faster.

At low rpm I have not noticed any difference.
Researching more hp ... I wanted to push myself to the maximum position: retard 6°.

what do you think please? smile
thank you .
ste
The only way you will really know is on a dyno.
I agree only a dyno or rolling road would show the changes. I would have thought the effect wouldn't be that great as you won't be changing the valve lift or overlap. You would hope whoever built the engine fitted the cam at the optimum angle.

humble

88 posts

107 months

Monday 13th March 2017
quotequote all
Please remind me, what is your setup again? Which engine and any mods, exhaust diameter, and intake? What are you trying to accomplish by adjusting the cam, more peak power, or bringing the power curve down?

Will


845ste said:
ciao a tutti,
i have a complete kit Comp-Cam with the Possibility to adjust the advance or retard from a minimum of 6 ° to a maximum of 6 °
Here I would ask you if someone has tried.

I use my GTR on the track and then try more hp biggrin ... with 7000rpm max.

I have already moved to the 1° retard and it seems that the gtr beyond 4500rpm ,rise more rpm faster.

At low rpm I have not noticed any difference.
Researching more hp ... I wanted to push myself to the maximum position: retard 6°.

what do you think please? smile
thank you .
ste

845ste

Original Poster:

577 posts

126 months

Monday 13th March 2017
quotequote all
ciao Will, i have L98: 6000cc (ls2) with head Ls3.



modifies: injector 65lbh, megasquirt, edelbrok intake, comp cam 231/237 .592 / .599 112 (max rpm 7200),exaust inox high.

I seek more hp at high speeds.
I do not care to lose NM at low rpm (the original has already much Nm at lower).

+ Nm at high rpm = + hp tot.

in USA recommended to anticipate the 4/6 ° but they seek NM at low.smile

I want the opposite: so I have to retard.biggrin

But how many degrees?
no one has tried.?

my kit includes an adjustable pulley 6 positions: + 6 ° / -6 °
tks

humble

88 posts

107 months

Monday 13th March 2017
quotequote all
Without getting too much into the nitty gritty you will want to advance the cam for more top end power not retard it. No matter what you do with that cam, you are limited by it's lift/duration and lobe separation angle, all of which determine the behavior of the engine and where it makes power. If you advance the cam (I would start at 4 degrees advance) you should gain top end power, and a little more torque but idle quality will suffer. If your engine is making more power after retarding the cam, it's a sign that your setup will probably benefit from a more aggressive cam, one with higher or split duration. I wouldn't call your cam wild by any stretch so if you were thinking about adjusting timing perhaps a new cam may be in order?

F.C.

3,896 posts

207 months

Monday 13th March 2017
quotequote all
humble said:
Without getting too much into the nitty gritty you will want to advance the cam for more top end power not retard it. No matter what you do with that cam, you are limited by it's lift/duration and lobe separation angle, all of which determine the behavior of the engine and where it makes power. If you advance the cam (I would start at 4 degrees advance) you should gain top end power, and a little more torque but idle quality will suffer. If your engine is making more power after retarding the cam, it's a sign that your setup will probably benefit from a more aggressive cam, one with higher or split duration. I wouldn't call your cam wild by any stretch so if you were thinking about adjusting timing perhaps a new cam may be in order?
That's the problem with single cams no opportunity to play with the separation angle.
So much nicer being able to adjust the intake and exhaust independently.

V8Dom

3,546 posts

201 months

Thursday 16th March 2017
quotequote all
845ste said:
ciao Will, i have L98: 6000cc (ls2) with head Ls3.



modifies: injector 65lbh, megasquirt, edelbrok intake, comp cam 231/237 .592 / .599 112 (max rpm 7200),exaust inox high.

I seek more hp at high speeds.
I do not care to lose NM at low rpm (the original has already much Nm at lower).

+ Nm at high rpm = + hp tot.

in USA recommended to anticipate the 4/6 ° but they seek NM at low.smile

I want the opposite: so I have to retard.biggrin

But how many degrees?
no one has tried.?

my kit includes an adjustable pulley 6 positions: + 6 ° / -6 °
tks
if you want more power at high rpm id replace your exhaust.

1/those headers are killing hp. the factory old headers killed 30-40 hp

2 you have a x pipe with exhaust gases from one bank flowing towards the other gases from the other bank.i would guess all that heat wrap is becuase it gets too hot?

i would replace with proper headers and redesign exhaust so x pipe works with flow in and out at opposite ends.....place x in line with car, not across the car.



845ste

Original Poster:

577 posts

126 months

Thursday 16th March 2017
quotequote all
ciao Dom,
I thought that the high collectors as mine were the best choice.
the bandages are used because there is always Too much heat under the clam.

the muffler that you see it on the inside has a "X" system.

in the past I tried (without muffler) systems with H and X pipes but only changed the sound and not the performance.
I believe that by varying the phase, I can squeeze out the last hp of my engine.
I have felt a big difference performance and sound from +4 to -2.

It is a mathematical formula i believe: NM at +rpm= +hp?

Advance: +NM at low rpm but - hp
retard: -NM but much hp at high rpm

but here, nobody has tried to vary the phase ???

ciao HUMBLE: yes but but if I put a Cam more aggressive, then I have problems with minimal and certainly lose NM at low rpm.
ie in the street is no longer "manageable", because as also says F.C. ,Unfortunately, the cam is only one.

in any case in the USA is a modifie that many do, and I read that may vary thirty hp ,and especially the mode of dispense.



Edited by 845ste on Thursday 16th March 21:06

V8Dom

3,546 posts

201 months

Friday 17th March 2017
quotequote all
imagine water flowing in two pipes towards each other... what happens??

now imagging 2 pipes parrallel with water flowing and they join into one in the same direction.

as you lift on and off the gas its the same as turning water on and off so flow is important... and yes i knew it was an x pipe inside

the headers are not the best im afraid, gail at AS ran dyno runs between my type headers and the standard headers 15 years ago and there is big differencves in hp.... primary length is importantand, along with cone length and secondard lengths..... ls3 will be completely different to sbc

the bigger headers werent used as the canam cars cant fit them

have you blueprinted the headers to head yet.... mine were 5mm offset compared to the exhaust ports

yes cam timing makes a difference.. i used to change mine every race when running bikes trying to find the optimum, but the cam companies find the best of both worlds when they give you setup figures.. there is more hp to be made else where with little effort. changing timing all teh time will be engine out on an engine dyno rather than in the car.

look at light flywheel and gearing.. pointless having a car that can do 190mph if all the tracks you use are 140 max

look at weight. tyres, handling.. all of these will make the difference in a lap time.. and if you want hp... big hp get a turbo or rotrax supercharger

F.C.

3,896 posts

207 months

Friday 17th March 2017
quotequote all

845ste

Original Poster:

577 posts

126 months

Friday 17th March 2017
quotequote all
ok I understand.
very kind of you all and thank you precious advice for the exhaust system. clap
But no one has done tests by varying the phase with an aggressive cam ....frown

Dom can put a picture of your exhaust system please?

I see that Lee (yellow GTR) has built a different system by all, with a single final output.

F.C.

3,896 posts

207 months

Saturday 18th March 2017
quotequote all
V8Dom said:
and if you want hp... big hp get a turbo or rotrax supercharger
Both of which will need a cam change, pointless having aggressive overlap on a pressurised system, you will be blowing your mixture straight through.

Dom, did you blueprint the header on or off the car?
If off did you have the heads flowed as well?

BobE

605 posts

180 months

Saturday 18th March 2017
quotequote all

confusionhunter

448 posts

221 months

Sunday 19th March 2017
quotequote all
Your formula makes sense in that the higher the revs the more power you make. You make less torque but deliver it faster (ie power).
However the way its written in misleading. Advancing timing will give you more power up top and less torque low down. Same applies to ignition, but that is limites by the mechanicals of the engine and flow characteristics of the engine. I set my can at +2 as its a road car so need a balance. No I didn't do any tests just did a bit of reading and look at the cam manufacturers website.

845ste

Original Poster:

577 posts

126 months

Tuesday 21st March 2017
quotequote all

confusionhunter

448 posts

221 months

Wednesday 22nd March 2017
quotequote all
Yea... Bottom line you probably need to try it and see. For us with single cam V8s, Inlet theory cannot be implemented in isolation, ie its always a balance between inlet and exhaust. The disadvantage of a single cam is you cant alter inlet to exhaust timing. Overlap is set and there is sod all you can do about it short of a regrind or new cam.

This article shows a single cam V8 making more power with 4 degrees advance over 0 degrees straight up.
http://www.hotrod.com/articles/mopp-1211-degreeing...
you need to look at the pictures for the results. 'By Advancing The Camshaft Four Degrees, We Ended Up With 329 Hp And 320 Lb Ft Of Torque. That's An Increase Of 8 Hp And 16 Lb Ft Of Torque'

However I agree with the theory of retarding the inlet higher up. For example Audi advances the inlet only at more than 80% throttle and between 1k and 4k revs on their VVC twin cam cars, meaning on a pull at 100% throttle it retards the inlets again above 4k revs.
Oh and also Comp cams do actually generalisethe other way.... retard means more HP up top.... so forget what I saidsmile
http://www.compcams.com/Pages/413/cam-timing-lobe-...

So its all clear as mud smile



Edited by confusionhunter on Wednesday 22 March 13:49

V8Dom

3,546 posts

201 months

Wednesday 22nd March 2017
quotequote all
F.C. said:
V8Dom said:
and if you want hp... big hp get a turbo or rotrax supercharger
Both of which will need a cam change, pointless having aggressive overlap on a pressurised system, you will be blowing your mixture straight through.

Dom, did you blueprint the header on or off the car?
If off did you have the heads flowed as well?
yes i did it with heads off as metal came off headers and heads
heads were already cleaned up, i just matched d shape of head to d of exhaust, they didnt match at all there was a big step down into the exhaust and it was offset too if that makes sense

V8Dom

3,546 posts

201 months

Wednesday 22nd March 2017
quotequote all




mine, sorry not better photos

V8Dom

3,546 posts

201 months

Wednesday 22nd March 2017
quotequote all
845ste said:
ciao Will, i have L98: 6000cc (ls2) with head Ls3.



modifies: injector 65lbh, megasquirt, edelbrok intake, comp cam 231/237 .592 / .599 112 (max rpm 7200),exaust inox high.

I seek more hp at high speeds.
I do not care to lose NM at low rpm (the original has already much Nm at lower).

+ Nm at high rpm = + hp tot.

in USA recommended to anticipate the 4/6 ° but they seek NM at low.smile

I want the opposite: so I have to retard.biggrin

But how many degrees?
no one has tried.?

my kit includes an adjustable pulley 6 positions: + 6 ° / -6 °
tks
sorry to ask a silly question..are those ultima gtr sbc headers on an ls head?