jimmeh
17-09-2005, 01:03 AM
reference http://www.importbuilders.com/timetotunemycar.htm
Its time to dyno your car, what do you do next?
This topic amazes me, it really does. I am going to spell it out exactly what should be done if you want total success. After you get the motor started for a few minutes, and you made sure the air/fuel ratio is decent you do this. You will need:
Compression tester
Leak Down tester
2 sets of Spark Plugs
Spark plug socket
Ratchet
Allen keys for your cam gears
Pad and Pen
You do this, and you do this exactly. But you have to make sure the motor has already been ran a few minutes to seat the rings.
Step 1: Compression Test all 4 cylinders. This is when the motor has not even be turned on yet. You write down your reading across all 4 cylinders.
Step 2: Leak Down Test all 4 cylinders: You write down your findings.
Step 3: Put in brand new Spark Plugs, properly gapped to your application.
Step 4: Proceed to dyno your motor.
Now here is why this is all important. For me, I do this when it’s a fully built motor to check and make sure what I built started out in perfect condition. If I forgot to give the motor a proper valve adjustment, these tests will tell me that. If the head, I thought was good had a slightly bent valve, this will tell me that. There is rarely a problem with new blocks because you could put the rings in upside down and all wrong and still have decent compression and leak down. This is a general statement, it depends what kind of rings your using. If the head gasket is not right, this will alert you to the problem.
You should do these steps because if there is a problem, you can fix the problem without any further damage to your motor. If you did not check the compression before you dyno’d and you proceed to make pass after pass, you just caused damage that will now probably cost in the near 1 thousand dollar range. Here is an example of why this is important. Say your valve adjustment on one cylinder is really bad. And you have compressions on your cylinders like this:
#1 240 PSI
#2 245 PSI
#3 240 PSI
#4 160 PSI
Well, if you proceed to dyno that motor, that block is going to meet its end soon. Remember, when you hook up your wideband, its averaging all 4 cylinders. So the average there is 221 PSI. So you’re tuning the motor for 221 PSI. So that means that cylinders 1, 2 and 3 are going to run lean, and 4 is going to run rich. Number 4 is way off, and way rich and one of two things will happen. One, number 4 will scuff the cylinder walls from way too much fuel washing out the rings, or one of the other cylinders pistons will expand into the cylinder walls and cause scuffing there. Either case equals burning oil and a need for re-bore and hone, maybe even all 4 new pistons! Because if 1 piston cannot be honed out to work, you have to replace all four.
If you didn’t have a compression tester, or a leak down tester and you think your good and all that and do this all the time, the other thing to search for to see a problem is the first pass on the dyno. If the first pass isn’t within 30 WHP of what you expect and you know the timing is correct and the A/F was 11:1-14:1, then you have a problem and stop. Also, you can look at the graph. Its going to be all jagged if the motor isn’t right, from the get go. Also if the motor doesn’t feel strong, or hesitates, or smokes you know to stop. The dyno graph, if your good at reading them can tell you a lot about the motor. Such as bent valves. Slightly bent valves will run ok up until a certain RPM, depending on how bent they are. You might have a perfect looking graph up to like 7500 RPM, then it just falls up fast. That’s probably bent valves, the higher RPM you go, the worse the compression gets and it exaggerates the slightly bent valve. This is common in motors that fall off very early.
So back to the testing before you dyno. When you test it, and it’s all say 350 PSI across all four cylinders or close to it, you KNOW you have the propensity to make good power. If you have a motor that’s 15:1 and you only get like 280 across all four, you know you did something wrong and should go back and check certain things over, such as the valve adjustment or Cam Gear settings. We did this method on my friend Todd’s motor and it was about 340 all the way across. I see over 300 and I know the motor has the potential to make about 245 WHP or 250. His made 255.9 Dynojet with an intake manifold, so that was what we expected. You get a motor that pegs 350 and you’re looking at a potential 260+ depending on how good your head porting is.
Buying heads and blocks can be expensive, so protect your investments people. When you get a block and a head from a shop and you put the motor together, do these tests right away. You can even do them before the motor even starts and then again after it has ran a few minutes. Check it twice. Make sure its all good and there are no bent valves. Once you put a motor on a dyno, and then have a problem, you can’t come back to the head porter and ask him why his head sucks so badly. But you could of if you pressure tested the head before you ever ran it. This especially applies to fully built race motors because often, they use large cams and they don’t measure clearances. So the split second the motor hits VTEC, the valves may tap the pistons and bend. Or the valves may touch each other. I have seen professionals over motors for HOURS trying to figure out what is wrong, and sure enough, they have put the timing belt on wrong because the aftermarket cam gears they bought were marked strangely or incorrectly. Little things you take for granted are not right. And if you hit VTEC 1 time on something that is put on wrong, such as cam timing, big cams, special pistons, then you could hurt the motor. The moral of the story is that checking the motor before you hit VTEC or run it on a dyno is important because you know what the motor is capable of after you check it. If everything came out good and the dyno graph sucks from the start, then do the tests again right there on the dyno and see how many valves you just bent. This is usually what happens…
Do not take anything for granted. You can’t even run a fistful of different cams at 0.0, stock cam gear setting because the valves will hit each other. Also, the head porter could have done a special valve job on the valves to make the valve to valve contact better, OR worse. You don’t know. Its always a good idea to start up a motor, if you have aftermarket cam gears, with the intake cam gear at 0, and the exhaust cam gear at +2, to give them some more separation in the valves.
You follow these steps when you get a motor started and are at a dyno, and you’re prepared to succeed.
Its time to dyno your car, what do you do next?
This topic amazes me, it really does. I am going to spell it out exactly what should be done if you want total success. After you get the motor started for a few minutes, and you made sure the air/fuel ratio is decent you do this. You will need:
Compression tester
Leak Down tester
2 sets of Spark Plugs
Spark plug socket
Ratchet
Allen keys for your cam gears
Pad and Pen
You do this, and you do this exactly. But you have to make sure the motor has already been ran a few minutes to seat the rings.
Step 1: Compression Test all 4 cylinders. This is when the motor has not even be turned on yet. You write down your reading across all 4 cylinders.
Step 2: Leak Down Test all 4 cylinders: You write down your findings.
Step 3: Put in brand new Spark Plugs, properly gapped to your application.
Step 4: Proceed to dyno your motor.
Now here is why this is all important. For me, I do this when it’s a fully built motor to check and make sure what I built started out in perfect condition. If I forgot to give the motor a proper valve adjustment, these tests will tell me that. If the head, I thought was good had a slightly bent valve, this will tell me that. There is rarely a problem with new blocks because you could put the rings in upside down and all wrong and still have decent compression and leak down. This is a general statement, it depends what kind of rings your using. If the head gasket is not right, this will alert you to the problem.
You should do these steps because if there is a problem, you can fix the problem without any further damage to your motor. If you did not check the compression before you dyno’d and you proceed to make pass after pass, you just caused damage that will now probably cost in the near 1 thousand dollar range. Here is an example of why this is important. Say your valve adjustment on one cylinder is really bad. And you have compressions on your cylinders like this:
#1 240 PSI
#2 245 PSI
#3 240 PSI
#4 160 PSI
Well, if you proceed to dyno that motor, that block is going to meet its end soon. Remember, when you hook up your wideband, its averaging all 4 cylinders. So the average there is 221 PSI. So you’re tuning the motor for 221 PSI. So that means that cylinders 1, 2 and 3 are going to run lean, and 4 is going to run rich. Number 4 is way off, and way rich and one of two things will happen. One, number 4 will scuff the cylinder walls from way too much fuel washing out the rings, or one of the other cylinders pistons will expand into the cylinder walls and cause scuffing there. Either case equals burning oil and a need for re-bore and hone, maybe even all 4 new pistons! Because if 1 piston cannot be honed out to work, you have to replace all four.
If you didn’t have a compression tester, or a leak down tester and you think your good and all that and do this all the time, the other thing to search for to see a problem is the first pass on the dyno. If the first pass isn’t within 30 WHP of what you expect and you know the timing is correct and the A/F was 11:1-14:1, then you have a problem and stop. Also, you can look at the graph. Its going to be all jagged if the motor isn’t right, from the get go. Also if the motor doesn’t feel strong, or hesitates, or smokes you know to stop. The dyno graph, if your good at reading them can tell you a lot about the motor. Such as bent valves. Slightly bent valves will run ok up until a certain RPM, depending on how bent they are. You might have a perfect looking graph up to like 7500 RPM, then it just falls up fast. That’s probably bent valves, the higher RPM you go, the worse the compression gets and it exaggerates the slightly bent valve. This is common in motors that fall off very early.
So back to the testing before you dyno. When you test it, and it’s all say 350 PSI across all four cylinders or close to it, you KNOW you have the propensity to make good power. If you have a motor that’s 15:1 and you only get like 280 across all four, you know you did something wrong and should go back and check certain things over, such as the valve adjustment or Cam Gear settings. We did this method on my friend Todd’s motor and it was about 340 all the way across. I see over 300 and I know the motor has the potential to make about 245 WHP or 250. His made 255.9 Dynojet with an intake manifold, so that was what we expected. You get a motor that pegs 350 and you’re looking at a potential 260+ depending on how good your head porting is.
Buying heads and blocks can be expensive, so protect your investments people. When you get a block and a head from a shop and you put the motor together, do these tests right away. You can even do them before the motor even starts and then again after it has ran a few minutes. Check it twice. Make sure its all good and there are no bent valves. Once you put a motor on a dyno, and then have a problem, you can’t come back to the head porter and ask him why his head sucks so badly. But you could of if you pressure tested the head before you ever ran it. This especially applies to fully built race motors because often, they use large cams and they don’t measure clearances. So the split second the motor hits VTEC, the valves may tap the pistons and bend. Or the valves may touch each other. I have seen professionals over motors for HOURS trying to figure out what is wrong, and sure enough, they have put the timing belt on wrong because the aftermarket cam gears they bought were marked strangely or incorrectly. Little things you take for granted are not right. And if you hit VTEC 1 time on something that is put on wrong, such as cam timing, big cams, special pistons, then you could hurt the motor. The moral of the story is that checking the motor before you hit VTEC or run it on a dyno is important because you know what the motor is capable of after you check it. If everything came out good and the dyno graph sucks from the start, then do the tests again right there on the dyno and see how many valves you just bent. This is usually what happens…
Do not take anything for granted. You can’t even run a fistful of different cams at 0.0, stock cam gear setting because the valves will hit each other. Also, the head porter could have done a special valve job on the valves to make the valve to valve contact better, OR worse. You don’t know. Its always a good idea to start up a motor, if you have aftermarket cam gears, with the intake cam gear at 0, and the exhaust cam gear at +2, to give them some more separation in the valves.
You follow these steps when you get a motor started and are at a dyno, and you’re prepared to succeed.