andymoraitis
15+ Year Contributor
- 3,241
- 154
- Jan 25, 2004
-
Utica,
Michigan
I'm opening this thread as an advanced discussion to try and figure out why I'm having spool issues on a stroker with only a medium sized turbo. You can review my mod list to see exactky what's in the motor. Trust me it's not all that much.
At the moment, I see full spool at 4400-4600 RPM depending on weather while runniing a 3rd gear pull from 2500 RPM. The turbo has a tendency to struggle to make boost until it hits 10 psi and then it shoots skyward pretty quickly. While running 1-2-3 shifts, it's not an issue since the motor is already spooling and pulling hard, but it's a bit disappointing from a 3rd gear pull. I wouldn't care if I could run the motor to 8000, but I'm shifting at 7000 due to the rod angle. Here's a laundry list of the things I've tried with the suggestion of my fellow wiseman who have been extremely helpful in their PM's.
- Leaned out the A/F to 14:1 at the onset of boost gradually increasing to 11:1 after 4600 RPM. The extra heat should have increased spool, but did nothing.
- Boost leak tests were performed at up to 26 psi. The system held 26 for 20 seconds before starting to slowly bleed down.
- Reduced fuel volume to the rail by lowering base fuel pressure from 43 to 38 psi. All this did was run me into knock on pump. There was a minimal effect on spool, but it was negligible.
- We reduced timing advance in the midrange to once again generate more heat. This just made the motor feel like a turd instead of providing any positive result. The timing were changed back to stock 2G that ramp to a max of 12 degrees of advance under the 4 highest load/airflow maps.
- Compression on all four cylinders with the Comp 200's (straight up) is 175-175-175-180 across the board. The motor does not smoke, eat coolant or behave erratically except for minor idle issues resulting from pulling the lower honeycomb on the 2G MAF.
- A vortex breaker honeycomb was installed between the intake and compressor inlet. This actually hurt spool and made the MAF erratic in the higher RPM's and negatively affected performance across the board.
- There is one small exhaust leak at the wastegate to dump tube connection that can be smelled, but not heard, when the motor is cold. As soon as it warms, the leak disappears and there are no other leaks at the turbine to O2 or manifold to head. The manifold to head gasket was also replaced at the time of installation with an EVO metal gasket.
- Cam timing is correct and I verified that the motor was dead on the timing marks with the motor at TDC. I was hoping it was off by a tooth (retarded but it wasn't)
There are a few things which I think it may be related to and I'll share them here:
- My cams need to be degreed with adjustable gears. I'd likely get the car on a dyno and advance the intake cam a few degrees while retarding the exhaust cam one degree.
- I'm feeding a turbo that has a 3" inlet with a 2.75" dejon intake pipe. While the system has an adapter coupler on it, I'm not sure if this is making a difference or not.
- I'm running a stock intake on a stock head. I'm not sure if these are creating significant flow restrictions but I have plans to at least change the intake manifold. While I know it will increase VE and overall power, I don't think it would do much for my spool condition. I also run a large sidemount (Dejon) and I wouldn't think that this is holding me back as a flow restriction point.
For reference, the motor is tuned with an EPROM ECU only. I have custom A/F maps that are flat across the board at 11:1 and 12 degrees of max timing advance since the leaner maps did nothing for me. Since I have the ability to see knock, I don't use a logger or bother with EGT anymore. I can only guess at the airflow numbers, but at 30 psi and 6000 RPM, I overran the MAF badly hence the removal of the lower honeycomb. Since the 2100 won't hold that much boost, I run 25 on a daily basis.
I'd love to hear some suggestions, but at this point I'm thinking that I need to at least pick up one adjustable cam gear and dial in the cam timing on the intake with a few degrees of advance. Other than the spool issue, the motor runs exceptionally well and I'm pleased with it. I'd just love to bring the power online sooner. Interestingly enough, even the 16G performed in a similar way by spooling 24 psi around 3600-3800 RPM. It's a bit disappointing if you ask me.
Helpful suggestions are encouraged and thanks for reading my novel,
Andy
At the moment, I see full spool at 4400-4600 RPM depending on weather while runniing a 3rd gear pull from 2500 RPM. The turbo has a tendency to struggle to make boost until it hits 10 psi and then it shoots skyward pretty quickly. While running 1-2-3 shifts, it's not an issue since the motor is already spooling and pulling hard, but it's a bit disappointing from a 3rd gear pull. I wouldn't care if I could run the motor to 8000, but I'm shifting at 7000 due to the rod angle. Here's a laundry list of the things I've tried with the suggestion of my fellow wiseman who have been extremely helpful in their PM's.
- Leaned out the A/F to 14:1 at the onset of boost gradually increasing to 11:1 after 4600 RPM. The extra heat should have increased spool, but did nothing.
- Boost leak tests were performed at up to 26 psi. The system held 26 for 20 seconds before starting to slowly bleed down.
- Reduced fuel volume to the rail by lowering base fuel pressure from 43 to 38 psi. All this did was run me into knock on pump. There was a minimal effect on spool, but it was negligible.
- We reduced timing advance in the midrange to once again generate more heat. This just made the motor feel like a turd instead of providing any positive result. The timing were changed back to stock 2G that ramp to a max of 12 degrees of advance under the 4 highest load/airflow maps.
- Compression on all four cylinders with the Comp 200's (straight up) is 175-175-175-180 across the board. The motor does not smoke, eat coolant or behave erratically except for minor idle issues resulting from pulling the lower honeycomb on the 2G MAF.
- A vortex breaker honeycomb was installed between the intake and compressor inlet. This actually hurt spool and made the MAF erratic in the higher RPM's and negatively affected performance across the board.
- There is one small exhaust leak at the wastegate to dump tube connection that can be smelled, but not heard, when the motor is cold. As soon as it warms, the leak disappears and there are no other leaks at the turbine to O2 or manifold to head. The manifold to head gasket was also replaced at the time of installation with an EVO metal gasket.
- Cam timing is correct and I verified that the motor was dead on the timing marks with the motor at TDC. I was hoping it was off by a tooth (retarded but it wasn't)
There are a few things which I think it may be related to and I'll share them here:
- My cams need to be degreed with adjustable gears. I'd likely get the car on a dyno and advance the intake cam a few degrees while retarding the exhaust cam one degree.
- I'm feeding a turbo that has a 3" inlet with a 2.75" dejon intake pipe. While the system has an adapter coupler on it, I'm not sure if this is making a difference or not.
- I'm running a stock intake on a stock head. I'm not sure if these are creating significant flow restrictions but I have plans to at least change the intake manifold. While I know it will increase VE and overall power, I don't think it would do much for my spool condition. I also run a large sidemount (Dejon) and I wouldn't think that this is holding me back as a flow restriction point.
For reference, the motor is tuned with an EPROM ECU only. I have custom A/F maps that are flat across the board at 11:1 and 12 degrees of max timing advance since the leaner maps did nothing for me. Since I have the ability to see knock, I don't use a logger or bother with EGT anymore. I can only guess at the airflow numbers, but at 30 psi and 6000 RPM, I overran the MAF badly hence the removal of the lower honeycomb. Since the 2100 won't hold that much boost, I run 25 on a daily basis.
I'd love to hear some suggestions, but at this point I'm thinking that I need to at least pick up one adjustable cam gear and dial in the cam timing on the intake with a few degrees of advance. Other than the spool issue, the motor runs exceptionally well and I'm pleased with it. I'd just love to bring the power online sooner. Interestingly enough, even the 16G performed in a similar way by spooling 24 psi around 3600-3800 RPM. It's a bit disappointing if you ask me.
Helpful suggestions are encouraged and thanks for reading my novel,
Andy