Tuning mis-matched Cams for 4AGE to get the most out of them

[wiso]

ok, I have done alot of searching on tuning aftermarket cams, I have the basic gist of how its done, I did this about 5 months ago setting them to the specs on the cam cards. Now I want to go and try and get the most out of them. I would just leave them as per card settings but the intake and exhaust are both differant manufacturers so I don't think I have them set up optimally. I say this because the car struggles to start, but once running, or light throttle to start its fine. Its only been doing this since changing the cams in, it was worse when I was first running them with the stock non adjustable wheels. It does feel a little laxed and I think it could better.

As said I understand how to find the lobe centres, find the open and close points and adjust in relation to the crank.

What I am having trouble understanding is getting the sweet point. I have attached links for my cam cards (from other threads).

by the exhaust cam (HKS256) it has opening 40thou @38deg BBDC, lobe centre @109deg BTDC and closed 40thou @0deg TDC

by the intake cam (wade872A) it has opening 50thou @0.5deg BTDC, lobe centre @109.5deg ATDC, and closed 50thou @39deg ABDC

Like I said this is how they turned out when set as per the cards.

Is this where I should be starting and just adjusting it degree at a time and see which way it feels better, or should I leave this up to a dyno tuner? or is there a more mathematical approach to it. Some basic tuning guides say you work out the lobe centres and these are the points you set ATDC for the intake and BTDC for the exhaust. by that theory what I have is already correct.

I was reading some info http://www.club4ag.com/faq_and_tech_...haft_story.htm they say that by adjusting the stock cams by 3degrees one way or the other changes the powerband of the motor. Is this the kinda playing I could do with these aftermarket cams aswell, or is this advised against? if I did start adjusting a degree or so here and there could I cause any damage, or would it just run like shit. I know if I go too far I will damage it as my 4a is an interferance motor.

I hope what I am asking is making sense, I am not asking how to adjust them, I am asking how to find the sweet spot for my motor.

oh I rarely get up to high rpm, about the most I go is about 6500-7000. as its a daily. So I would be looking for a more meaty mid range. even lower, I know If I really wanted this I should have kept the stock 240deg bigport cams.

HKS cam card
http://i79.photobucket.com/albums/j1...HKSExhaust.jpg
Wade cam card
http://img80.imageshack.us/i/872a.pdf/

Some links I have been reading up on.

http://www.toymods.org.au/forums/sho...mshaft-Timing&

http://www.toymods.org.au/forums/sho...age+cam+timing

http://www.toymods.org.au/forums/sho...age+cam+timing

http://www.toymods.org.au/forums/sho...age+cam+timing

http://www.rbracing-rsr.com/camshaft.html

http://www.skylinesaustralia.com/for...ing-camshafts/

http://forums.toymods.org.au/index.p...t=0#msg_530672

if the answer is in one of these thread I do apologise, it probably means I didn't understand what they were saying.

maybe this one may hold the answer, I'll read through later http://www.toymods.org.au/forums/sho...age+cam+timing

[oldcorollas]

edit: dammit, i think i got mixed up

doh, didn't... oh well, this summarises it

http://www.nightrider.com/biketech/camlsatable.htm

retard cam and advance exhaust, to reduce overlap.
do intake first, maybe 3deg, then exhaust 3deg, see what happens.

both will reduce cam lift at TDC, but your motor will onyl be interference if timing belt breaks?

easier to set on dyno, since both the overlap and the centreline of the overlap will both affect location of powerband.

109deg on the HKS card says peak power at 8000rpm

edit 11ty: you may onyl need 1 or 2deg change, but also depends on your intake and exhaust setups, and which side needs more "help"

[wiso]

so basically what this is saying is that to get what that site refers to as a wide separation angle (more low end) I need to retard the intake cam and advance the exhaust cam?

so by your theory a good starting point is 3 degrees. this would retard the intake cam from the 109 ATDC it currently is to around 111/112 which is close to the stock points I believe. and maybe start by leaving my exhaust cam at the about 109 BTDC it is and try advanceing it to maybe 111 also? if this is the case I am back to where they were on the stock wheels, and it ran like a dog there

am I understanding this correctly, or am I way off.

Sorry if I am having a little trouble getting this, thanks for your patience

[oldeskewltoy]

Now I want to go and try and get the most out of them.

the intake and exhaust are both differant manufacturers so I don't think I have them set up optimally.

What I am having trouble understanding is getting the sweet point.

Is this where I should be starting and just adjusting it degree at a time and see which way it feels better, or should I leave this up to a dyno tuner?

I was reading some info http://www.club4ag.com/faq_and_tech_...haft_story.htm they say that by adjusting the stock cams by 3degrees one way or the other changes the powerband of the motor. Is this the kinda playing I could do with these aftermarket cams aswell, or is this advised against? if

I hope what I am asking is making sense, I am not asking how to adjust them, I am asking how to find the sweet spot for my motor.

oh I rarely get up to high rpm, about the most I go is about 6500-7000. as its a daily. So I would be looking for a more meaty mid range. even lower, I know If I really wanted this I should have kept the stock 240deg bigport cams.

imho... it is dyno time....



actually the redtop cams will support more low end because of cam timing....



the intake closes sooner on the redtop cams 44 degrees, instead of 51 degrees

[wiso]

OST sweet diagram on the stock cams.

I was having a think about this, so based on the website old corolla put up.

so the general idea, when people say 110/110 or 100/100.

For the 110/110, the more you retard the intake cam to open later and advance the ehxaust to open earlier means you reduce the overlap this moves the power band lower but reduces peak.

Now getting toward the 100/100. advancing the intake maybe around 105 to open earlier and retarding the exhuast to about the same i am increasing the overlap which would essentially move the power band to high rpm and go for peak power.

is that correct?

Sorry for dumming it down and possibly repeating what has been said, I am just trying to fully understand this. It helps by re-writing it

thanks

[wiso]

imho... it is dyno time....

think you may be right, I don't know how accurate my seat of the pants dyno is, anyone got a rough idea of what this kinda tuning would cost on the dyno?

[oldcorollas]

For the 110/110, the more you retard the intake cam to open later and advance the ehxaust to open earlier means you reduce the overlap this moves the power band lower but reduces peak.

Now getting toward the 100/100. advancing the intake maybe around 105 to open earlier and retarding the exhuast to about the same i am increasing the overlap which would essentially move the power band to high rpm and go for peak power.

is that correct?

generally yes, and yes it helps to write it out (also with mispatched cams, you may not ned an equal split, like 110,110, it might be 112,107 or something)

while you may be getting closer to stock cam timing, you still have more overlap due to increased lift and increased duration, and as a few sites remind, it's not the separation angle that is important, but the opening and closing events

it also depends a lot on your ports and intake/exhaust tract etc
for example, on yank sites, you see people running BIG cams on V8's, with peak power at maybe 6000rpm, but a LSA of 104 or 106deg... that means huge overlap, but due to the nature of their ports etc, it is the "best" setting

another way you could do it is to gorrow a Gtech(2?) type thing, OR just log your rpm, and do 2nd gear or third gear pulls and plot rpm vs time, then do some maths in excel to work out acceleration vs rpm (which is same as torque vs rpm, roughly), and then you can compare your changes reasonably well (needs to be same conditions as much as possible tho), or can at least compare the shape of the curves.
(i can help with the maths if you need?)


it is also quite possible that the aftermarket cams are ground at a certain LSA, to work with stock pulleys, OR that they are not, and stock pulleys wll be way out... OR that your adjustables are not marked accurately..

in any case, the best position is found by experimentation, as it changes a lot for each setup.

btw, if you don't have a logging device, or Gtech, a Megasquirt can be used to log RPM

[trdee]

dyno tuning is usually charged by the hour, so the cost depends on how long you reckon it would take....

[wiso]

it is also quite possible that the aftermarket cams are ground at a certain LSA, to work with stock pulleys, OR that they are not, and stock pulleys wll be way out... OR that your adjustables are not marked accurately..

in any case, the best position is found by experimentation, as it changes a lot for each setup.

I am pretty sure both of these cams aren't designed to work with stock pulleys. My adjustables could possibly be marked wrong as they don't have any markings at all, I made them. but when i set them as it was done per card so this wasn't nessesary considering you set the crank to position and adjusted the cam to open, max and close at the desired degree on the crank. but to do this playing it would deffiantly be an idea to degree them out, I may have to make a degree wheel for them like i do the crank.

so experimentation is the answer to find the right spot.

[wiso]

actually the redtop cams will support more low end because of cam timing....

the intake closes sooner on the redtop cams 44 degrees, instead of 51 degrees

I know its been a little while but I had a go at this on the weekend. OST you say the smallport cams support more low end because the close sooner. This is the exact opposite to what OC has said and shown in that link. It states by turning from 109 to 111 deg I should be getting less overlap hence supporting more low end. In order to have the intake close sooner I would need to turn it the other way, from 109 to 108 deg instead, but according to that link this would increase overlap making the intake event earlier. Hence going to higher rpm??????


I bring this up as I had a play, left the exhaust cam at the 109.5deg centerline, but changed the intake from the 109 to 111deg centerline back in the stock position. The engine definitely has more pull down low now. So this is good, but the engine idles like an old v8 brap brap brap brap. Sound really off beat. But revs smoothly.

What do people think could have happened here, have I turned them the wrong way?

[oldeskewltoy]

I'm only talking about the intake valve closing event - not overlap. The sooner the intake valve closes, the more cylinder pressure is built. More cylinder pressure, more low end torque

[wiso]

OST that is interesting. I do believe that is in contradiction to what I believed before. but definitely what you are saying makes sense.

you say by having the intake event close earlier the cylinder will build more pressure. yes I pressure tested my cylinders after changing the intake cam from 109deg to 111deg and I have lost 15psi of cylinder pressure.


so is there 2 ways to build low end torque on the engine with the cam timing? 1 by having the intake close earlier to build more pressure, and 2 to increase the LSA of the cams reducing overlap.

the way I see it these 2 are in direct contradiction to each other...... to increase the LSA you have to make the intake close later. to have it close earlier you have to decrease the LSA giving the opposite effect......

man I am getting confused.

[oldcorollas]

at engine speed, things are different.. need to think about port velocity

before intake valve closes, you already have flow into cylinder, and you can continue to increase cylinder filling after the piston already starts coming up.
how far up the piston goes before cylinder stops filling depends on port speed and engine rpm.

regarding overlap, the energy from the exhaust can help scavenge the cylinder, and also help to start the intake charge flowing.

too much overlap and too little rpm, and the fresh charge goes out the open exhuast valve.
too little overlap, and you don't get much assistance to start the flow, but at lower engine speed there is less acoustic energy to achieve that anyway

it'S better to think of the valve events seperately, but yes, it is a balancing act..
however, i'd venture that the overlap is more important than the intake valve closing.. unless the closign is so late that you are getting reversion

[wiso]

I have had some rather peculiar results after playing with adjustment on the weekend.

decreasing the overlap severely dropped the cylinder compression turning them back to 111, 111 Centrelines. also I noticed that while the car did get power from a lower RPM about 3000rpm onward, below 3000rpm it had virtually nothing, going up a slight incline the car would not be able to accelerate, it would barely hold the speed. it felt like it really ran out of puff early, about 6000 odd rpm.

set back to cam cards settings. it seems to be more consistant in lower RPM being evenly able to accelerate up inclines. power hits in about 4500-5000rpm. I was a little more prescise this time. it starts and runs alot smoother than it did the first time round.


I am a little nervous about increasing the overlap. not sure what results this would herald.

I was hoping to get onto a dyno to get it looked at. but i rang a few places to enquire and nobody want to touch it as its a waste of time since I don't have an aftermarket ECU. these are even places that are endorsed by toymodders. its pointless even having aftermarket cams apparently.