Where is my top end power?
09-10-2011, 04:17 AM
#1
Junior Member
Thread Starter
iTrader: (2)
Join Date: Sep 2009
Location: singapore
Posts: 228
Total Cats: 2
Where is my top end power?
I just did a 1.8 engine swap with flyin miata manifold and I am short of at least 60bhp at the top end. Here's the dyne chart(every square is 25bhp)
The white line is what my car is doing now and the purple line is another car with the same setup, same engine type. same Garrett turbo (GT2560r), same exhaust, injectors,ecu. The difference are: the exhaust manifold, he is running eBay exhaust manifold and me flyin miata manifold, I am running COP and I am running water injection.
I cannot bring myself to believe that an ebay manifold will make 60bhp more than me!!!
I suspect the following:
- There is something wrong with my exhaust, it collapse or choked
- when rebuilding my head, I got the timing wrong. But my car is idling perfectly and not missing at all, would it still be the case?
- that the eBay manifold is making a lot more power in the top end because it is tubular and the flyin miata ones are log manifold?
Have I missed out anything? Could my engine be fuked? But i am not losing compression, engine oil or coolant and it is holding boost all the way to redline.
Please help.
The white line is what my car is doing now and the purple line is another car with the same setup, same engine type. same Garrett turbo (GT2560r), same exhaust, injectors,ecu. The difference are: the exhaust manifold, he is running eBay exhaust manifold and me flyin miata manifold, I am running COP and I am running water injection.
I cannot bring myself to believe that an ebay manifold will make 60bhp more than me!!!
I suspect the following:
- There is something wrong with my exhaust, it collapse or choked
- when rebuilding my head, I got the timing wrong. But my car is idling perfectly and not missing at all, would it still be the case?
- that the eBay manifold is making a lot more power in the top end because it is tubular and the flyin miata ones are log manifold?
Have I missed out anything? Could my engine be fuked? But i am not losing compression, engine oil or coolant and it is holding boost all the way to redline.
Please help.
Last edited by nismo502; 09-10-2011 at 11:21 AM.
Reply
0
0
09-10-2011, 10:18 AM
#7
Junior Member
Thread Starter
iTrader: (2)
Join Date: Sep 2009
Location: singapore
Posts: 228
Total Cats: 2
It is actually making lesser bhp than my 1.6 prior to the swap.
Reply
0
0
09-10-2011, 11:29 AM
#11
Here are my thoughts for what they are worth:
1. A tubular manifold will flow better than a log, but not this much better. Remember that the main restriction in the exhaust is the turbo.
2. Make sure of the condition of the intake. Even though you are maintaining boost, your turbo may be working really hard to keep that boost if there is a leak.
3. Do a run without WI using the timing that was used on the other car. It is worth it to eliminate the variable.
4. Honestly, aside from a boost leak, this looks like a valve timing or lift thing to me. Your peak is below 5500. You'll also notice that you're making more power (hence more torque) at the lower RPMs than the other guy. Everything lined up? Cams OK? Lifters OK?
Anyway, just thinking out loud and I'm sure there are things I've missed.
1. A tubular manifold will flow better than a log, but not this much better. Remember that the main restriction in the exhaust is the turbo.
2. Make sure of the condition of the intake. Even though you are maintaining boost, your turbo may be working really hard to keep that boost if there is a leak.
3. Do a run without WI using the timing that was used on the other car. It is worth it to eliminate the variable.
4. Honestly, aside from a boost leak, this looks like a valve timing or lift thing to me. Your peak is below 5500. You'll also notice that you're making more power (hence more torque) at the lower RPMs than the other guy. Everything lined up? Cams OK? Lifters OK?
Anyway, just thinking out loud and I'm sure there are things I've missed.
Reply
0
0
09-10-2011, 11:38 AM
#13
Junior Member
Thread Starter
iTrader: (2)
Join Date: Sep 2009
Location: singapore
Posts: 228
Total Cats: 2
1. A tubular manifold will flow better than a log, but not this much better. Remember that the main restriction in the exhaust is the turbo.
Agreed, thats what I thought too
2. Make sure of the condition of the intake. Even though you are maintaining boost, your turbo may be working really hard to keep that boost if there is a leak.
I also made a run without the airfilter, there is not much difference
3. Do a run without WI using the timing that was used on the other car. It is worth it to eliminate the variable.
Ya I will try that
4. Honestly, aside from a boost leak, this looks like a valve timing or lift thing to me. Your peak is below 5500. You'll also notice that you're making more power (hence more torque) at the lower RPMs than the other guy.
I do not think there is a boost leak because it is maintaining boost level throughout the rev range. Here is my boost chart, the 2nd box is the one, it is holding boost till the end.
Everything lined up? Cams OK? Lifters OK?
Ahh, that is what i need to find out now because I had a headgasket change during the swap. Now, if the cams and lifters are problematic or if not lined out properly, wouldnt there be idling problem or misfiring during high rev?
Agreed, thats what I thought too
2. Make sure of the condition of the intake. Even though you are maintaining boost, your turbo may be working really hard to keep that boost if there is a leak.
I also made a run without the airfilter, there is not much difference
3. Do a run without WI using the timing that was used on the other car. It is worth it to eliminate the variable.
Ya I will try that
4. Honestly, aside from a boost leak, this looks like a valve timing or lift thing to me. Your peak is below 5500. You'll also notice that you're making more power (hence more torque) at the lower RPMs than the other guy.
I do not think there is a boost leak because it is maintaining boost level throughout the rev range. Here is my boost chart, the 2nd box is the one, it is holding boost till the end.
Everything lined up? Cams OK? Lifters OK?
Ahh, that is what i need to find out now because I had a headgasket change during the swap. Now, if the cams and lifters are problematic or if not lined out properly, wouldnt there be idling problem or misfiring during high rev?
Reply
0
0
09-10-2011, 11:49 AM
#15
Junior Member
Thread Starter
iTrader: (2)
Join Date: Sep 2009
Location: singapore
Posts: 228
Total Cats: 2
Last edited by nismo502; 09-10-2011 at 12:20 PM.
Reply
0
0
09-10-2011, 12:03 PM
#16
Don't discount a boost leak. Your turbo has a fair amount of residual capacity to overcome a leak. But you'll be making it work much harder. The best way to check for a boost leak is to pressurize your intake and do a blead down test.
You do have boost sag. I'm guessing that your signal line for the wastegate is pre-intercooler? Moving it post-intercooler helps.
On WI, don't forget that WI by itself doesn't necessarilly make power. There are two mechanisms at work with WI:
1. "Chemical Intercooling": If you are injecting a good proportion of methyl alcohol, then you should be seeing a fair amount of temperature drop in the intake. That will increase power. If you are injecting 100% water (as I am), then this effect will not be very drastic (or may not be present at all) because the compressed air in your intake is already near the saturation point.
2. "Octane Boost": Adding WI will change the flame-front/pressure-rise properties in the combustion chamber. In this way, it acts like a high-octane fuel. How much of this happens is inversely proportional to your intake cooling. If you use up the chemical cooling in the intake (as you will with more alcohol), then there is less left over for the combustion chamber -- and vice versa. An "octane boost" by itself does not yield increased power -- in fact it can decrease power as it moves the point of maximum cylinder pressure to later in the combustion stroke. I'll bet that the HP curve Brain was talking about was aggressive WI coupled with no change to the spark map. A WI octane boost coupled with an increase in spark advance will increase power. It has to be tuned.
You do have boost sag. I'm guessing that your signal line for the wastegate is pre-intercooler? Moving it post-intercooler helps.
On WI, don't forget that WI by itself doesn't necessarilly make power. There are two mechanisms at work with WI:
1. "Chemical Intercooling": If you are injecting a good proportion of methyl alcohol, then you should be seeing a fair amount of temperature drop in the intake. That will increase power. If you are injecting 100% water (as I am), then this effect will not be very drastic (or may not be present at all) because the compressed air in your intake is already near the saturation point.
2. "Octane Boost": Adding WI will change the flame-front/pressure-rise properties in the combustion chamber. In this way, it acts like a high-octane fuel. How much of this happens is inversely proportional to your intake cooling. If you use up the chemical cooling in the intake (as you will with more alcohol), then there is less left over for the combustion chamber -- and vice versa. An "octane boost" by itself does not yield increased power -- in fact it can decrease power as it moves the point of maximum cylinder pressure to later in the combustion stroke. I'll bet that the HP curve Brain was talking about was aggressive WI coupled with no change to the spark map. A WI octane boost coupled with an increase in spark advance will increase power. It has to be tuned.
Reply
0
0
09-10-2011, 12:19 PM
#20
Probably not. With a 2-valve per cylinder engine, if you had a cam lobe gone or a lifter compressed, you would definitely see it. With our 4-valve engines, you're just increasing overall flow capacity, but it usually won't result in a noticeable miss. Now, if both intakes or both exhausts on the same cylinder had an issue . . . but the chances of that are pretty remote.
Reply
0
0
