NosLaser
DSM Wiseman
- 2,209
- 5
- Apr 22, 2002
-
Cape Coral,
Florida
...Semi off topic: I realize everyone's car is different, but isn't 11:1 A/F fairly aggressive on pump gas...you didnt specify. I was thinking more around 10:1 on pump gas, or maybe that's me being conservative....
You bring up a good point, however for pump gas, you would tune closer to the 10.8ish end of the spectrum, while on race gas you would tune towards the 11.1-11.2 area. The reason for this is you still want to be able to run aggressive timing to make horsepower. Again, your point is valid, but 10:1 is a bit on the rich side, even for pump gas.
...Haha, I was going to post about this when I read your above post here, but I guess you beat me to it. What you say makes sense about EGT's and simply retardation of the exhaust cam, but wouldnt your engine worsen if EGT's hit a certain degree even if the AF mixture is correct? I would think there is a point where the temperature is too hot for the aluminum head, and valves to handle, and would begin causing problems. Excuse me if I'm not being exact here it's 3:30, and my roommate downstairs decided to be a dick tonight and be really loud with his drunk ass friends, so I coudlnt sleep and decided to post stuff....
You are correct, and the quality of the parts you use plays a very big role here. This is why things like stainless steel valves become so important for higher HP applicatons and larger turbos that require more heat to spool. You can tune the EGT's to be higher in the exhaust manifold than in the combustion chamber through retarding the exhaust cam or even simply retarding ignition timing; you are going to get SOME explosions in the exhaust manifold but that will be beneficial for turbo spoolup. Those are the kind of EGT's that you want, however can wear down lower quality parts; i.e. it may not be so good for turbine wheel blades or wastegates. This is the reason why some companies will make parts out of inconel (sp.) so they can withstand the high temps sometimes needed to make big power. There is a tradeoff here, and there is definately a learning curve. I can divuldge some tuning secrets (which I do from time to time for those who are paying attention) to give you an idea of what you want in a turbo car. Let's first take a step back to what I mentioned before about cam and ignition timing, and how it affects EGTs and where the explosions occur. With retarding the cam timing, you are going to be reducing valve overlap, and creating a more violent explosion within the combustion chamber (therefore again not forcing cylinder pressure out of an exhaust valve) so in essence, you are going to be increasing combustion chamber temperatures. With retarded IGNITION timing, picture how this works. Mind you that the plug is firing upwards of say 18-20 degrees ATDC so the piston is already on its way down the cylinder, the exhaust valve is already beginning to open, and you are taking this hot mixture of air and fuel, and forcing it to another hot place, and then igniting it just before it gets there. PAY CLOSE ATTENTION HERE. This is exactly what happens in a diesel motor (taking a hot mixture, and bringing it to a hot place; causing it to ignite.) What is going to happen with retarded ignition timing is that you will actually be causing some explosions in the exhaust manifold, causing EGT's in the manifold to potentially be hotter than combustion chamber temps. (keep in mind that combustion chamber temps can vary greatly..they do make temp sensors for the combustion chambers but I'm not sure how accurate they would be on our DOHC motors as they go into the spark plug bung, and the accuracy really depends on how far the plug protrudes into the combustion chamber which on our cars is not very far, etc. but I'm getting off topic here) Here's the part to pay attention to, and the part where I explain another reason why a PMS for instance is SOO much better than an AFC. IF you want to spool a turbo fast, I mean to LIGHT THAT THING UP at low rpms, here is what you do. You want to add fuel, and retard ignition timing so that you DO realize some actual combustion (explosions) in or about the opening of the exhaust manifold. There is a very fine line here. You will come to find it only takes a VERY short period of time, sometimes maybe even only a couple hundred rpm to acheive the desired affect you want, and then you must go back to advancing ignition timing to get proper combustion as of course retarded ignition timing is not ideal for efficient combustion. A sidenote of what's also cool about a PMS is that you can tune the car to do this only under full throttle so that the car is it's normal efficient self under regular driving. See what I wrote about heat energy and you'll understand why this works. Go watch a Pro 5.0 race and watch the turbo cars run. A lot of the time you will hear a loud POP or perhaps a POP POP sound, and then the car will focking RIP off the line. The 'pop' is the sound of combustion in the exhaust manifold (or headers) lighting the turbos up like a focking rocket. I'm sitting here getting goosebumps because of how scientific, and how cool this process is, and how it affects a turbo car and the way it performs. A LOT of people don't know this, and really don't understand what is going on inside the motor, and what's really happening with ignition and cam timing, and how it affects power; they simply think run a bigger turbo to flow more air, and add more fuel, and you make power by proxy. This is not me trying to be a know it all, but these are secrets that a lot of tuners DON'T want to share because that is their competative edge over everyone else. I'm reluctant to share them as well, but I don't know if my financial situation would ever allow me to own my own shop and be successful, so I might as well help you all out for free huh?
If I DO open a shop, then you all better come to me to buy parts and get work done...hehe. Anyway, I think this subject may go even further with the additional questions I'm being asked, so I may go a little deeper into it depending on response. I hope this answers all the questions I've had so far.
Regards,
You bring up a good point, however for pump gas, you would tune closer to the 10.8ish end of the spectrum, while on race gas you would tune towards the 11.1-11.2 area. The reason for this is you still want to be able to run aggressive timing to make horsepower. Again, your point is valid, but 10:1 is a bit on the rich side, even for pump gas.
...Haha, I was going to post about this when I read your above post here, but I guess you beat me to it. What you say makes sense about EGT's and simply retardation of the exhaust cam, but wouldnt your engine worsen if EGT's hit a certain degree even if the AF mixture is correct? I would think there is a point where the temperature is too hot for the aluminum head, and valves to handle, and would begin causing problems. Excuse me if I'm not being exact here it's 3:30, and my roommate downstairs decided to be a dick tonight and be really loud with his drunk ass friends, so I coudlnt sleep and decided to post stuff....
You are correct, and the quality of the parts you use plays a very big role here. This is why things like stainless steel valves become so important for higher HP applicatons and larger turbos that require more heat to spool. You can tune the EGT's to be higher in the exhaust manifold than in the combustion chamber through retarding the exhaust cam or even simply retarding ignition timing; you are going to get SOME explosions in the exhaust manifold but that will be beneficial for turbo spoolup. Those are the kind of EGT's that you want, however can wear down lower quality parts; i.e. it may not be so good for turbine wheel blades or wastegates. This is the reason why some companies will make parts out of inconel (sp.) so they can withstand the high temps sometimes needed to make big power. There is a tradeoff here, and there is definately a learning curve. I can divuldge some tuning secrets (which I do from time to time for those who are paying attention) to give you an idea of what you want in a turbo car. Let's first take a step back to what I mentioned before about cam and ignition timing, and how it affects EGTs and where the explosions occur. With retarding the cam timing, you are going to be reducing valve overlap, and creating a more violent explosion within the combustion chamber (therefore again not forcing cylinder pressure out of an exhaust valve) so in essence, you are going to be increasing combustion chamber temperatures. With retarded IGNITION timing, picture how this works. Mind you that the plug is firing upwards of say 18-20 degrees ATDC so the piston is already on its way down the cylinder, the exhaust valve is already beginning to open, and you are taking this hot mixture of air and fuel, and forcing it to another hot place, and then igniting it just before it gets there. PAY CLOSE ATTENTION HERE. This is exactly what happens in a diesel motor (taking a hot mixture, and bringing it to a hot place; causing it to ignite.) What is going to happen with retarded ignition timing is that you will actually be causing some explosions in the exhaust manifold, causing EGT's in the manifold to potentially be hotter than combustion chamber temps. (keep in mind that combustion chamber temps can vary greatly..they do make temp sensors for the combustion chambers but I'm not sure how accurate they would be on our DOHC motors as they go into the spark plug bung, and the accuracy really depends on how far the plug protrudes into the combustion chamber which on our cars is not very far, etc. but I'm getting off topic here) Here's the part to pay attention to, and the part where I explain another reason why a PMS for instance is SOO much better than an AFC. IF you want to spool a turbo fast, I mean to LIGHT THAT THING UP at low rpms, here is what you do. You want to add fuel, and retard ignition timing so that you DO realize some actual combustion (explosions) in or about the opening of the exhaust manifold. There is a very fine line here. You will come to find it only takes a VERY short period of time, sometimes maybe even only a couple hundred rpm to acheive the desired affect you want, and then you must go back to advancing ignition timing to get proper combustion as of course retarded ignition timing is not ideal for efficient combustion. A sidenote of what's also cool about a PMS is that you can tune the car to do this only under full throttle so that the car is it's normal efficient self under regular driving. See what I wrote about heat energy and you'll understand why this works. Go watch a Pro 5.0 race and watch the turbo cars run. A lot of the time you will hear a loud POP or perhaps a POP POP sound, and then the car will focking RIP off the line. The 'pop' is the sound of combustion in the exhaust manifold (or headers) lighting the turbos up like a focking rocket. I'm sitting here getting goosebumps because of how scientific, and how cool this process is, and how it affects a turbo car and the way it performs. A LOT of people don't know this, and really don't understand what is going on inside the motor, and what's really happening with ignition and cam timing, and how it affects power; they simply think run a bigger turbo to flow more air, and add more fuel, and you make power by proxy. This is not me trying to be a know it all, but these are secrets that a lot of tuners DON'T want to share because that is their competative edge over everyone else. I'm reluctant to share them as well, but I don't know if my financial situation would ever allow me to own my own shop and be successful, so I might as well help you all out for free huh?
If I DO open a shop, then you all better come to me to buy parts and get work done...hehe. Anyway, I think this subject may go even further with the additional questions I'm being asked, so I may go a little deeper into it depending on response. I hope this answers all the questions I've had so far.Regards,
