Some general info about tuning from Fasterproms, basic to advanced
03-20-2009, 05:54 PM
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Some general info about tuning from Fasterproms, basic to advanced The most basic of upgrades is the induction and exhaust. There are a few things that can be done to optimize the combination such as tuning the spark and fuel curve. Most any modification that alters the way air and fuel enter and exit the motor should be tuned for. Our objective here is to look at the whole picture , how and why spark and fuel mixtures are altered with modifications and how to optimize them.
Take for example a tuned vehicle, the optimal spark and fuel curve and the car is equipped with a good cold air system and a catback muffler system. The car then gets an upgraded intake manifold such as a ported FAST. The intake manifold will now get a much denser charge in heavier throttle 2k rpm on up. Well now our spark and fuel curve must now be revised with our much denser air charge. It takes less time for our denser air fuel mixture to combust because of greater pressure, we need less spark advance or less lead time in order to achieve best power. If we were to leave the spark alone we would encounter preignition or spark knock. With less spark on this combo we are igniting the mixture at the proper time in order to get the most efficient burn and propel the piston back down. Typically the WOT spark curve will be the reciprocal of the torque curve. If you have ever looked at a dyno sheet and the tq curve looks like a hill the optimal spark curve (if plotted out) many times will look like a valley. Where an engine makes best torque is where it builds the most pressure and generally needs the least spark advance. Where the tq is less one can run more spk advance while still steering away from knock.
This is a before and after or an 07 LS2 vette. Going from a full optimized tuned Ported LS2 manifold to a tuned and Ported FAST. We ported and installed both manifolds, tuned each combo. We gained a very significant amount of Tq and thus we had to retard the timing by about 4 degrees to get the best power.
On a side note we encourage people to clean out the oil in the cylinder heads intake ports to allow the tuner to be able to get a bit more aggressive on the tune. With a good portion of our business porting manifolds we want to help those that are purchasing our products. If you have the manifold off clean out the oil. Any oil in the induction lowers the octane rating and thus can lead to spark knock. Remember, more spark does not always translate into more power. Spark is merely a medium of achieving max cylinder pressure for combustion. We often see PCV issues on many cars with breathers. You cannot run the PCV system and have a breather (nor a breather on a catch can, with the PCV system still hooked up) it is a vaccuum leak and will ingest 5x the oil. The PCV system is a closed circuit system it takes measured air post MAF, goes thru the crankcase and then into the vaccuum port on the intake manifold just behind the TB flange. If you interrupt this the fueling will be very far off.
The exhaust system is in many fashions the very opposite of the induction in terms of what must be done with the spark curve. The better the exhaust the more spark advance the vehicle will take in order to achieve best power. The better the exhaust system generally the leaner the WOT mixture will be on an A-B test. A good set of headers usually will take about 2 degrees more spark advance.
I hope this is helpful..
Thank you and God Bless
Jeremy Formato
Take for example a tuned vehicle, the optimal spark and fuel curve and the car is equipped with a good cold air system and a catback muffler system. The car then gets an upgraded intake manifold such as a ported FAST. The intake manifold will now get a much denser charge in heavier throttle 2k rpm on up. Well now our spark and fuel curve must now be revised with our much denser air charge. It takes less time for our denser air fuel mixture to combust because of greater pressure, we need less spark advance or less lead time in order to achieve best power. If we were to leave the spark alone we would encounter preignition or spark knock. With less spark on this combo we are igniting the mixture at the proper time in order to get the most efficient burn and propel the piston back down. Typically the WOT spark curve will be the reciprocal of the torque curve. If you have ever looked at a dyno sheet and the tq curve looks like a hill the optimal spark curve (if plotted out) many times will look like a valley. Where an engine makes best torque is where it builds the most pressure and generally needs the least spark advance. Where the tq is less one can run more spk advance while still steering away from knock.
This is a before and after or an 07 LS2 vette. Going from a full optimized tuned Ported LS2 manifold to a tuned and Ported FAST. We ported and installed both manifolds, tuned each combo. We gained a very significant amount of Tq and thus we had to retard the timing by about 4 degrees to get the best power.
On a side note we encourage people to clean out the oil in the cylinder heads intake ports to allow the tuner to be able to get a bit more aggressive on the tune. With a good portion of our business porting manifolds we want to help those that are purchasing our products. If you have the manifold off clean out the oil. Any oil in the induction lowers the octane rating and thus can lead to spark knock. Remember, more spark does not always translate into more power. Spark is merely a medium of achieving max cylinder pressure for combustion. We often see PCV issues on many cars with breathers. You cannot run the PCV system and have a breather (nor a breather on a catch can, with the PCV system still hooked up) it is a vaccuum leak and will ingest 5x the oil. The PCV system is a closed circuit system it takes measured air post MAF, goes thru the crankcase and then into the vaccuum port on the intake manifold just behind the TB flange. If you interrupt this the fueling will be very far off.
The exhaust system is in many fashions the very opposite of the induction in terms of what must be done with the spark curve. The better the exhaust the more spark advance the vehicle will take in order to achieve best power. The better the exhaust system generally the leaner the WOT mixture will be on an A-B test. A good set of headers usually will take about 2 degrees more spark advance.
I hope this is helpful..
Thank you and God Bless
Jeremy Formato
