Changing just the CAM pulleys / installing adj cam gears

[wozzah1975]

Dann,

I've made my point about why I think it does improve things. You and wozza both give no explanation as to why it doesn't, suffice saying check it on a dyno.

Boosted air is lost on overlap. That is a fact. Every manufacture does it when releasing a turbo version of their engine. That is a fact.

I'm keen to have you clearly explain why no change to overlap doesn't result in lost air and fuel and overall a negative effect compared to what I've done which reduces this loss.

G

i've explained on several occations that boost isn't a measure of power, only a measure of inlet pressure. If you're measuring purely on boost only, then all you have is a measure of how much restriction you have, not how much air is being passed through the the engine, which is what gives you you're power and nothing to do with the boost reading.

Making the lobe centreline wider, or decreasing overlap which you have done in theory stops air being pushed through on the overlap stroke (wasted out the exhaust valve on the overlap) just the same as it does on an NA engine, only it is exaggerated on a boosted application which is why in general you open up the lobe centreline by around 2-4 degrees given every other engine spec the same.

Bottem line, even though you're boost level has increased doesn't automatically mean your power level has, as explained in other posts. Cam timing and specs is a black art, and every engine varies. You should be dialling your cams via a dyno, NOT via a boost gauge. A dyno is and always has been the only place to correctly find what your engine requires for camshaft timing. I can assure you that your car would have less boost but more power with a decent cylinder head and cams fitted to it. Why?, because it is flowing more air and has less restriction.

Cheers,
Woz

[gslender]

i've explained on several occations that boost isn't a measure of power, only a measure of inlet pressure. If you're measuring purely on boost only, then all you have is a measure of how much restriction you have, not how much air is being passed through the the engine, which is what gives you you're power and nothing to do with the boost reading.

I agree and didn't say boost=power. Just that making this change resulted in #1 a measurable increase in boost pressure (which correllates with a reduction in overlap as being a potential area for leaking boost) and #2 a noticeable increase in butt-dyno feeling (which also correlates with a more efficient chamber filling process where fuel/air is being maximised). At no stage did I say "Uggg, more boost equals more power... though I can see many posts around here that make that claim!".

Making the lobe centreline wider, or decreasing overlap which you have done in theory stops air being pushed through on the overlap stroke (wasted out the exhaust valve on the overlap) just the same as it does on an NA engine, only it is exaggerated on a boosted application which is why in general you open up the lobe centreline by around 2-4 degrees given every other engine spec the same.

Which is exactly what I've done. I did what is commonsense for this type of application - if you have a high reving NA engine with healthy overlap it stands to reason that if you FI the engine, you may wish to consider making the lobe centreline wider. I don't dispute the results are hard to predict, other than to say it *might* help. In my case I tried it and have seen two indications to show that it has had an impact. Only my butt-dyno says it was beneficial, the other impact just tells me it at least reduced the "air being pushed through on the overlap stroke" as you say.

Bottem line, even though you're boost level has increased doesn't automatically mean your power level has, as explained in other posts. Cam timing and specs is a black art, and every engine varies. You should be dialling your cams via a dyno, NOT via a boost gauge. A dyno is and always has been the only place to correctly find what your engine requires for camshaft timing. I can assure you that your car would have less boost but more power with a decent cylinder head and cams fitted to it. Why?, because it is flowing more air and has less restriction.

No doubt if I replaced the head, cams and even went as far as stroked the engine this would all change the air flow dynamics. I'm not disputing that.

All that is happening here is a $300 investment on adj cam gear, my time and an approach that says reduce the overlap just a little, and a result that indicates it changed the air flow, and a butt-dyno measurement that says it might have helped.

I'd encourage more people to do more testing. I plan to take the car to the dyno (soon), and I might try and fund some time to play with a couple of cam settings. If I can I will report back my findings as I'd bet there are a lot of standard cam engines with turbos that could benefit from a simple change to the overlap without having to invest in replacement cams AND adj cam gears.

I still stand by the fact that those who have FI their engines might want to look into this. I think it improved things but YMMV.

G

[NitroDann]

Nononono

you are pushing less air through the engine full stop. At whatever rpm the pressure increase occurs.

Im not a hater and all for experimentation, however I need some dyno charts

Dann

[gslender]

you are pushing less air through the engine full stop

Think of it like this...

Imagine you have a silicone pipe T-clamp leak that opens just when the intake valve opens. Would you expect boost to rise or drop?

It drops and you fix it by reducing the amount T-clamp opens (think reduce overlap) and seeing the boost pressure rise once you've fixed it. Why? Because there is more of a closed volume being forced with air, and boost pressure is a measure of that restriction. If you close overlap, you increase boost pressure.

Overlap exists because naturally aspirated engines benefit from the exhaust gas leaving / rushing out and creating a vacuum that helps suck in the fresh incoming charge behind it. In forced induction, that benefit isn't required, and in some situations can actually work against you... Forced air is forced right through during overlap and is wasted energy and work that the engine is doing for no benefit. Even worse, fuel is probably in that charged air, and is being wasted!

The intake valve isn't opening less, it opens for the same amount and the cyclinder is still filling with air - it is just not being wasted as much as before.

I don't understand why you're so against understanding this - where do you think the air is going to go when there is overlap? Think of it another way, what would happen if I increased overlap so significantly, eventually there would be virtually no boost pressure and the VE would drop - in the same way as if I drilled a hole in the intake silicone pipe.... and let the boost pressure vent to atmosphere.

G

[sailaholic]

Yes the valves are open the same time, but with Less overlap means you might be leaving more combusted air in the cylinder if you have had insufficient purging.

Note I'm saying might! In your case maybe that wasn't the case.

Sent from my GT-I9100 using Tapatalk 2

[wozzah1975]

you are pushing less air through the engine full stop

Think of it like this...

Imagine you have a silicone pipe T-clamp leak that opens just when the intake valve opens. Would you expect boost to rise or drop?

It drops and you fix it by reducing the amount T-clamp opens (think reduce overlap) and seeing the boost pressure rise once you've fixed it. Why? Because there is more of a closed volume being forced with air, and boost pressure is a measure of that restriction. If you close overlap, you increase boost pressure.

Overlap exists because naturally aspirated engines benefit from the exhaust gas leaving / rushing out and creating a vacuum that helps suck in the fresh incoming charge behind it. In forced induction, that benefit isn't required, and in some situations can actually work against you... Forced air is forced right through during overlap and is wasted energy and work that the engine is doing for no benefit. Even worse, fuel is probably in that charged air, and is being wasted!

The intake valve isn't opening less, it opens for the same amount and the cyclinder is still filling with air - it is just not being wasted as much as before.

I don't understand why you're so against understanding this - where do you think the air is going to go when there is overlap? Think of it another way, what would happen if I increased overlap so significantly, eventually there would be virtually no boost pressure and the VE would drop - in the same way as if I drilled a hole in the intake silicone pipe.... and let the boost pressure vent to atmosphere.

G

All you are doing by moving the lobe centre line is moving your power band, its that simple. An NA engine would have exactly the same effect, though more exaggerated.

My concern is that you are recommending people play with this without backing it up with any hard evidence which can only be done on an accurate dyno with datalogging. Not only that, due to production tolerances the cam timing between engines is all over the shop, your engine could be 4+ deg different to someone elses of exactly the same make and year, so recommending the settings you have means little, as others could have better cam timing than yours from the factory.

You will find that.
A: you will have increased low end cylinder filling by opening up the lobe centre line, but you will have sacrificed power elsewhere in the process, same as it would have on an NA application.
B: the extra boost you have may be caused by upsetting exhaust scavenging due to the change in your exhaust cam timing, which can be detrimental to power. Alot of times if you create a situation where you have more boost at peak power/torque on a supercharged application by changing cam timing you will find that the power figure has actually gone backwards, not forwards.

You noted earlier about trends in camshaft timing from manufacturers being different for Turbo applications.
Alot of the reasons for this are about drivability, not power. The cams are made smaller to
A: offset the lower compression ratio which makes the engine doughy down low
B: in turbo applications, spool faster down low and increase low end cylinder filling, which is also why the lobe centre line is moved.

In fact, a very common mod for the turbo'd B6/BP engines (before aftermarket cams were available) was to fit the NA cams in a performance application because they work better.

Yes, your car may feel better, but what you will find is that you have just moved the power band. It may suit your application better, it may not. you may have increased power at a given point, but you will have lost out at another given point, or you may have gone backwards everywhere. You won't know until you have accurately back to back dyno'd your car, and accurately logged power and torque curves.

Cheers
Warren

[gslender]

Yes the valves are open the same time, but with Less overlap means you might be leaving more combusted air in the cylinder if you have had insufficient purging.

Note I'm saying might! In your case maybe that wasn't the case.

Sent from my GT-I9100 using Tapatalk 2

I doubt it. Exhaust timing is the same and the remaing overlap under forced air would probably make up for any difference.

G

[gslender]

Interesting post that confirms what I've seen.
http://www.miataturbo.net/diy-turbo-dis ... post189001

Note to all: don't believe the nay sayers!

G

[wozzah1975]

Interesting post that confirms what I've seen.
http://www.miataturbo.net/diy-turbo-dis ... post189001

Note to all: don't believe the nay sayers!

G

What on that forum proves anything? i didnt see any factual results, just a bunch of unfounded statements and opinions.

What you are reading on that forum is typical of people "playing" and giving absolutley no substance in backing up results, and it means absolutely nothing. When you post up factual results proving my previous statements about the subject of camshaft timing wrong i will eat my words and publically bow to you right here.

Answer me this, how have you dialled you camshafts, and how have you determined what timing you have even when your pulleys are set at zero? because I will almost gaurantee that with your pulley's set to zero you won't have the factory quotes specs for camshaft timing. you may just be correctly production tolerance problems........

just to be clear.

What I have stated earlier is,
Cam timing is unique to every engine, n/a or F/I. production tolerances are responsible for this, as is also exhaust and intake tuning.

Moving your lobe centre lines and camshaft timing and changing nothing else will move your power band up and down, and regardless of being n/a of F/i there will be a sweet spot, and the type of power curve you require will be directly related to how you dial them. Eg: a road car would be ideally set with a power/torque curve lower in the rev range, a track/curcuit car would be dialled to give power higher in the rev range. Either side of the 'sweet spot' will be detrimental to the power/torque curve. once again, every engine is unique.

Less over lap doesn't mean more power and less wasted air. on an F/I application the tolerance level is simply narrower, the same principles for making power, and given power curves still apply.

whilst cam timing changes to your engine may work, doesnt mean they will for others.

Something as simple as extractor design and length, and intake runner length effects the camshaft timing majorly, as they are directly related to make the engine scavenge. N/a or forced, no difference, still requires them to be matched.

the statement you are making is that wider lobe centre lines and less overlap makes more overall power, correct?
back up your statements with some factual results, then we'll discuss it further.......

Cheers
Warren

[daffyflyer]

I'll have to poke the ominous stack of IC engineering textbooks I have lurking around on this one.

The way I see it, it could be caused by the fact that the SC is blowing boost against a closed exhaust valve for longer, thus genuinely squeezing more air in. Or it could not.. But if the car feels quicker when its reading these higher boost readings I'd be suspecting it is due to that.


This is something I'm currently doing a LOT of research on as we're engaged in doing engine simulation stuff for the game we're working on. If any of the textbooks we're using mention anything about this I'll drop in and let you know, because I'm honestly not sure at the moment

[gslender]

Interesting post that confirms what I've seen.
http://www.miataturbo.net/diy-turbo-dis ... post189001

Note to all: don't believe the nay sayers!

G

What on that forum proves anything? i didnt see any factual results, just a bunch of unfounded statements and opinions.

What you are reading on that forum is typical of people "playing" and giving absolutley no substance in backing up results, and it means absolutely nothing. When you post up factual results proving my previous statements about the subject of camshaft timing wrong i will eat my words and publically bow to you right here.

Answer me this, how have you dialled you camshafts, and how have you determined what timing you have even when your pulleys are set at zero? because I will almost gaurantee that with your pulley's set to zero you won't have the factory quotes specs for camshaft timing. you may just be correctly production tolerance problems........

just to be clear.

What I have stated earlier is,
Cam timing is unique to every engine, n/a or F/I. production tolerances are responsible for this, as is also exhaust and intake tuning.

Moving your lobe centre lines and camshaft timing and changing nothing else will move your power band up and down, and regardless of being n/a of F/i there will be a sweet spot, and the type of power curve you require will be directly related to how you dial them. Eg: a road car would be ideally set with a power/torque curve lower in the rev range, a track/curcuit car would be dialled to give power higher in the rev range. Either side of the 'sweet spot' will be detrimental to the power/torque curve. once again, every engine is unique.

Less over lap doesn't mean more power and less wasted air. on an F/I application the tolerance level is simply narrower, the same principles for making power, and given power curves still apply.

whilst cam timing changes to your engine may work, doesnt mean they will for others.

Something as simple as extractor design and length, and intake runner length effects the camshaft timing majorly, as they are directly related to make the engine scavenge. N/a or forced, no difference, still requires them to be matched.

the statement you are making is that wider lobe centre lines and less overlap makes more overall power, correct?
back up your statements with some factual results, then we'll discuss it further.......

Cheers
Warren

All I hear is blah, blah, could work and make a difference, blah, blah, can't say without a dyno, blah, blah, tolerances to ridiculous detail, blah, blah, heaps of other stuff impact it, blah, blah, I've got no proof either but I can sound more technical about how scary and impossible the science is, blah, blah....

G

[wozzah1975]

Interesting post that confirms what I've seen.
http://www.miataturbo.net/diy-turbo-dis ... post189001

Note to all: don't believe the nay sayers!

G

What on that forum proves anything? i didnt see any factual results, just a bunch of unfounded statements and opinions.

What you are reading on that forum is typical of people "playing" and giving absolutley no substance in backing up results, and it means absolutely nothing. When you post up factual results proving my previous statements about the subject of camshaft timing wrong i will eat my words and publically bow to you right here.

Answer me this, how have you dialled you camshafts, and how have you determined what timing you have even when your pulleys are set at zero? because I will almost gaurantee that with your pulley's set to zero you won't have the factory quotes specs for camshaft timing. you may just be correctly production tolerance problems........

just to be clear.

What I have stated earlier is,
Cam timing is unique to every engine, n/a or F/I. production tolerances are responsible for this, as is also exhaust and intake tuning.

Moving your lobe centre lines and camshaft timing and changing nothing else will move your power band up and down, and regardless of being n/a of F/i there will be a sweet spot, and the type of power curve you require will be directly related to how you dial them. Eg: a road car would be ideally set with a power/torque curve lower in the rev range, a track/curcuit car would be dialled to give power higher in the rev range. Either side of the 'sweet spot' will be detrimental to the power/torque curve. once again, every engine is unique.

Less over lap doesn't mean more power and less wasted air. on an F/I application the tolerance level is simply narrower, the same principles for making power, and given power curves still apply.

whilst cam timing changes to your engine may work, doesnt mean they will for others.

Something as simple as extractor design and length, and intake runner length effects the camshaft timing majorly, as they are directly related to make the engine scavenge. N/a or forced, no difference, still requires them to be matched.

the statement you are making is that wider lobe centre lines and less overlap makes more overall power, correct?
back up your statements with some factual results, then we'll discuss it further.......

Cheers
Warren

All I hear is blah, blah, could work and make a difference, blah, blah, can't say without a dyno, blah, blah, tolerances to ridiculous detail, blah, blah, heaps of other stuff impact it, blah, blah, I've got no proof either but I can sound more technical about how scary and impossible the science is, blah, blah....

G

You could just answer the simple questions i asked, i haven't been rude to you, and I'd appreciate you did the same back. I am trying to explain the simple fundimentals of what you are trying to achieve, and what effects it has when you change these things.

I've been building and modifying engines a long time, and I'm am by no means the best at it. But unlike you i have been carrying out developement work and backing my results up with facts rather than fiction or sifting through bulls$%t on the internet and the results speak for themselves. I really don't care if you f#*k you car up in the process, or if you turn it into a dog, but you could at least treat anyone that gives you advice and tries to explain things for you with a little respect rather than being rude.

Cheers
Woz

[wozzah1975]

https://www.facebook.com/notes/david-vi ... 5777025249

Have a read of that link, which is a very brief insight as to just how technical what you are playing with is, and how small changes effect the cam timing, and then note what he says at the end of the article about the "Moral" to the story. Unlike alot of authors who just repeat and print what they are told, David Vizard does all his own work, and is well known in the developement world.

Cheers
Warren

[gslender]

You could just answer the simple questions i asked, i haven't been rude to you, and I'd appreciate you did the same back. I am trying to explain the simple fundimentals of what you are trying to achieve, and what effects it has when you change these things.

I've been building and modifying engines a long time, and I'm am by no means the best at it. But unlike you i have been carrying out developement work and backing my results up with facts rather than fiction or sifting through bulls$%t on the internet and the results speak for themselves. I really don't care if you f#*k you car up in the process, or if you turn it into a dog, but you could at least treat anyone that gives you advice and tries to explain things for you with a little respect rather than being rude.

Cheers
Woz

Warren, using your experience and reputation such that you don't have to back up what you are saying and then scolding anyone who makes claims otherwise is being rude. The word condescending comes to mind.

I'm not really interested in hearing your opinion on why you think it makes no difference. In your own previous posts you've intermixed comments that suggest it could work, but might not, that it could be useless but you also appreciate where it might help. Overall, all you've done is spread fear, uncertainty and doubt and essentially said the avg joe should never try such a "black art" (your own words) without the use of a dyno. Thanks, that helps - not.

If you want to help, stay focused on the subject. Don't introduce replacing the head, new cams or any other engine mods. Stay on subject, talk specifically about the NA6 stock cams and the effect related to retarding the intake and advancing the exhaust as it relates to overlap and the impact of forced induction (in my case when using a SC which is very different to the effects when using a Turbo). The lobe separation data is easily available and if you've not actually looked at it and studied it in this context to understand the impacts of what I've done, then perhaps most of your alarmist advice isn't relevant? Good general advice for sure, but still not relevant.

The changes I'm talking about here are slight and within the "factory" tolerances you speak about - so take a chill pill and be positive rather than dumping negatively on someone else's efforts to give it a go, try something and report the results.

If you want me to respect your experience then offer something that I can learn from - dumping on me with "I know what I'm talking about" doesn't work as essentially you are just another one of those faceless internet forum posters that you criticised heavily before. I'll take your advice now and treat what you say with a grain of salt yeah?

G

[wozzah1975]

You could just answer the simple questions i asked, i haven't been rude to you, and I'd appreciate you did the same back. I am trying to explain the simple fundimentals of what you are trying to achieve, and what effects it has when you change these things.

I've been building and modifying engines a long time, and I'm am by no means the best at it. But unlike you i have been carrying out developement work and backing my results up with facts rather than fiction or sifting through bulls$%t on the internet and the results speak for themselves. I really don't care if you f#*k you car up in the process, or if you turn it into a dog, but you could at least treat anyone that gives you advice and tries to explain things for you with a little respect rather than being rude.

Cheers
Woz

Warren, using your experience and reputation such that you don't have to back up what you are saying and then scolding anyone who makes claims otherwise is being rude. The word condescending comes to mind.

I haven't "scolded" anyone including you, at no stage have I said what you are doing is wrong or slagged you out for it. I am simply stating your method of testing is not accurate, and you should check it properly before and after you make the changes, as should anyone else who wants to make such a change. I am all for anyone trying these sorts of changes, but do proplerly. I can back up any of my previous statements with dyno print outs at any point you like. The concept of the subject hasn't changed in 50+years

I'm not really interested in hearing your opinion on why you think it makes no difference. In your own previous posts you've intermixed comments that suggest it could work, but might not, that it could be useless but you also appreciate where it might help. Overall, all you've done is spread fear, uncertainty and doubt and essentially said the avg joe should never try such a "black art" (your own words) without the use of a dyno. Thanks, that helps - not.

I would hardly call advising people to base their testing on facts and doing it properly, and understanding the concept as "spreading fear". I have never said I think it will make "no difference", and I have NEVER said average joe shouldn't try it, more a case of if you are going change things KNOW what you are changing instead of thinking it, and understand it at the same time. Any reputable tuner or engine builder will tell you that this can only be carried out properly on an accurate dyno. Advising people to try these changes is good, but adivising them to try changes without facts or proof, or a form of measurement isn't. If you're not interested in hearing my opinion, thats fine, I really don't care, I will save comments and advice for others who are.

If you want to help, stay focused on the subject. Don't introduce replacing the head, new cams or any other engine mods. Stay on subject, talk specifically about the NA6 stock cams and the effect related to retarding the intake and advancing the exhaust as it relates to overlap and the impact of forced induction (in my case when using a SC which is very different to the effects when using a Turbo). The lobe separation data is easily available and if you've not actually looked at it and studied it in this context to understand the impacts of what I've done, then perhaps most of your alarmist advice isn't relevant? Good general advice for sure, but still not relevant.

I did make the reference about the cyl head and cams to explain about the irrelevance of your boost figure being higher. Anyone reading this topic that saw your post about having more boost after the cam change and it "feeling better" could be disillusioned by thinking its a good thing, when it is possible you have more boost because the engine is passing less air because you have upset the scavenging, and have a worse power curve than before. I'm not saying that it has, I am saying that it is possible because you haven't got the correct data to compare

The changes I'm talking about here are slight and within the "factory" tolerances you speak about - so take a chill pill and be positive rather than dumping negatively on someone else's efforts to give it a go, try something and report the results.

The factory tolerance I refer to are in regard to true top dead centre, changes in block deck height, and changes in cylinder head height. You can't change any of these with what you are doing. That statement was made so you understand every engine is different. Thats why what works on your B6 may not work on another. Slight changes can make big amounts of difference. Once again people reading could be disillusioned by thinking what works for you will automatically work for someone with the same model car, and a similar set up. I have never been negative toward you, your efforts or anyone elses, I have just simply stated that your method of measuring your changes isn't accurate.

If you want me to respect your experience then offer something that I can learn from - dumping on me with "I know what I'm talking about" doesn't work as essentially you are just another one of those faceless internet forum posters that you criticised heavily before. I'll take your advice now and treat what you say with a grain of salt yeah?

I haven't criticised what you have done, I am simply saying that you should measure your changes correctly and I can give plenty of examples of why, not just from me, but from others in the know as well. I am not the "be all end all" expert, and I don't pretend to be, but I do believe I have posted valid points, and information that you and others can learn from. I have been, and always will share my experience and information with anyone, and if you lived closer I would be happy to spend time on a chassis dyno with your car and help you out as I have done for others. If my statements have come accross to you as "I know what I am talking about, fullstop" then you have misunderstood my posts, or I haven't been clear in putting my thoughs in writing. I am happy to start fresh with thoughts and advice if this is the case.

G

Cheers
Warren