Still, I can imagine better atomization from a true mechanical injection nozzle at higher pressures than electronic injectors are capable of running at. Notice how the spray pattern becomes erratic as a few of the injectors reach a max duty cycle or are at l00%. That can easily cause some unequal distribution problems. Something you don't want at peak hp and full boost.
Advancement of fuel delivery?
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Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
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Rusty, At what rpm would you reach 8 psi boost with the 1.32 housing and then at what rpm would you reach 8 psi boost level with the 1.0?
Just saw this.
I reach 8psi after launch.
With the 1.32 I would launch at 4300 and 4# of boost. It would climb from 4# to 15# in 1 second after launch.
With the 1.0 I can launch with 7# at the same 4300 and can make 24# in 1 second if I need.
An interesting quote from a recent turbocharger book I picked up.
'If you can run a large turbine, there may be very high performance gains possible from something called "crossover".'
"Crossover occurs almost exclusively on engines with large turbines."
Crossover involving the short valve overlap period of the camshaft to assist combustion chamber purging of trapped exhaust gases. Basically, when you can run a turbine arrangement that lowers exhaust system back pressure to a point where exhaust back pressure is less than boost pressure, a cam with an appreciable amount of valve overlap will work much better at scavenging trapped exhaust gases from the combustion chamber, increasing VE and powah.
ref. Turbocharging Performance Handbook. by Jeff Hartman. Motorbooks 2007.
'If you can run a large turbine, there may be very high performance gains possible from something called "crossover".'
"Crossover occurs almost exclusively on engines with large turbines."
Crossover involving the short valve overlap period of the camshaft to assist combustion chamber purging of trapped exhaust gases. Basically, when you can run a turbine arrangement that lowers exhaust system back pressure to a point where exhaust back pressure is less than boost pressure, a cam with an appreciable amount of valve overlap will work much better at scavenging trapped exhaust gases from the combustion chamber, increasing VE and powah.
ref. Turbocharging Performance Handbook. by Jeff Hartman. Motorbooks 2007.
An idea popped into my head and I wanted to put it down before I forgot it.
It is well known that alcohol prefers a certain intake temp to 'preheat' the a/f mixture so that vaporization is better achieved for a more complete combustion. Under boost, an excess of intake heat can become a problem, even with alcohol. I won't get into the argument of whether you should run an intercooler or not with an alcohol engine. That decision basically comes down to preference, weight considerations, and the application. What I want to throw around, having made the decision to run an intercooler with an alcohol engine, is the options of how to use the intercooler to control the intake air temp, whether that is to cool the charge or help preheat it.
It's accepted that the optimum intake air temp for a blown alcohol application is around 160 to 180 degrees. Some prefer 220F. The boiling point for methanol is 149F. That is where optimum vaporization occurs. When the engine is under boost, achieving that target air temp is not a problem with the blower heating the air through the air compression process. With more boost, more heat to a point that it's desireable to remove some of the excess heat to control preignition and achieve a higher horsepower tune.
A small alcohol engine with a relatively large turbo requires a lot of exhaust heat energy to get things spinning. Alcohol gives exhaust temps that are quite a bit lower than what you have with gasoline, so when the engine is off boost, it's a problem getting some good exhaust heat energy to help spool the turbo. The one thing going for alcohol is that there is more exhaust mass volume than what you have with gasoline, but heat energy is a high percentage component needed to spool the turbo. Some feel it's 80%.
The idea is, what if you could use the intercooler to preheat the intake air temp to raise exhaust temps while off boost, when trying to spool the turbo, then use the intercooler to control the intake air temp when in high boost.
I'm thinking much the same way that the engine radiator helps to preheat the automatic transmission fluid while the car is warming up and then how the cooler in the radiator controls transmission temp spikes due to the superior heat transfer that occurs with that type of cooler system arrangement.
Isn't it interesting that the cooling system of a properly tuned alcohol engine typically will run between 160 to 180 degrees F. What if one were to include the intercooler in the engine cooling system flow path.
It is well known that alcohol prefers a certain intake temp to 'preheat' the a/f mixture so that vaporization is better achieved for a more complete combustion. Under boost, an excess of intake heat can become a problem, even with alcohol. I won't get into the argument of whether you should run an intercooler or not with an alcohol engine. That decision basically comes down to preference, weight considerations, and the application. What I want to throw around, having made the decision to run an intercooler with an alcohol engine, is the options of how to use the intercooler to control the intake air temp, whether that is to cool the charge or help preheat it.
It's accepted that the optimum intake air temp for a blown alcohol application is around 160 to 180 degrees. Some prefer 220F. The boiling point for methanol is 149F. That is where optimum vaporization occurs. When the engine is under boost, achieving that target air temp is not a problem with the blower heating the air through the air compression process. With more boost, more heat to a point that it's desireable to remove some of the excess heat to control preignition and achieve a higher horsepower tune.
A small alcohol engine with a relatively large turbo requires a lot of exhaust heat energy to get things spinning. Alcohol gives exhaust temps that are quite a bit lower than what you have with gasoline, so when the engine is off boost, it's a problem getting some good exhaust heat energy to help spool the turbo. The one thing going for alcohol is that there is more exhaust mass volume than what you have with gasoline, but heat energy is a high percentage component needed to spool the turbo. Some feel it's 80%.
The idea is, what if you could use the intercooler to preheat the intake air temp to raise exhaust temps while off boost, when trying to spool the turbo, then use the intercooler to control the intake air temp when in high boost.
I'm thinking much the same way that the engine radiator helps to preheat the automatic transmission fluid while the car is warming up and then how the cooler in the radiator controls transmission temp spikes due to the superior heat transfer that occurs with that type of cooler system arrangement.
Isn't it interesting that the cooling system of a properly tuned alcohol engine typically will run between 160 to 180 degrees F. What if one were to include the intercooler in the engine cooling system flow path.
The key to developing the best power from burning methanol is very closely tied to proper atomization and vaporization of the fuel for a more complete burn. Engine temp, fuel temp and intake air temp play a very important role in that end. If the mixture temp is too cold, not enough of the fuel will have vaporized and a loss in power will be experienced.
The preferred intake air temp will be different for each application and is a very important tuning tool. With the boiling point of methanol at 149F, the preferred intake air temp should be at least above that temperature.
There is also a limit to how high you want the engine temp and intake air temp. It is well known that once you've reached a certain intake air temp, engine temp, with an alcohol engine power loss is assured.
So. Intake air temp management of an alcohol engine is a very, very important consideration.
The preferred intake air temp will be different for each application and is a very important tuning tool. With the boiling point of methanol at 149F, the preferred intake air temp should be at least above that temperature.
There is also a limit to how high you want the engine temp and intake air temp. It is well known that once you've reached a certain intake air temp, engine temp, with an alcohol engine power loss is assured.
So. Intake air temp management of an alcohol engine is a very, very important consideration.
How about a bypass valve in the intercooler ductwork that would permit the use of intercooled air when you are under boost OR non-intercooled (hot) air when you need warm air? I guess the big challenge would be the ability to quickly switch from one mode to the other without interrupting the flow of air. With a car as fast as you car, there isn't much time to accomplish the switch.
Conrad
Conrad
I was thinking the same thing. But not switching the air, switching the water source for the intercooler. I would only need, at the most, 2 seconds of heated air until the turbo spooled. Or! Heat the intercooler well before the burnout box and start the switch to cool the intercooler just before the launch. There would be some delay time involved and the intercooler will need some time to start cooling down, even after the switch. Possibly by the time the turbo has spooled the temp of the intercooler would be starting to come down.How about a bypass valve in the intercooler ductwork that would permit the use of intercooled air when you are under boost OR non-intercooled (hot) air when you need warm air? I guess the big challenge would be the ability to quickly switch from one mode to the other without interrupting the flow of air. With a car as fast as you car, there isn't much time to accomplish the switch.
Conrad
The problem I would see with switching the air to bypass the intercooler would be, where would the hot air come from? Off boost, there is no hot air coming from the turbo. Only after the turbo has already started to build boost does it supply heated air. I need the heated air before the turbo has started to build boost and then a switch to intercooled air sometime during the build up of boost. Around 16 to 18 psi I think would be good. The cooling of the intercooler would not be instantaneous, so the timing of the heating/cooling medium switch would have to be timed correctly.
I would think that the air temp would not need to be at 160 F. But it would need to be somewhere between ambient and 160F. Some heat would be supplied by the engine components, head port walls, intake manifold. Good argument for a non air-gap intake manifold, isn't it. The intake design should be such that it will be allowed to warm as the engine does. Some experimenting would need to be done to find the optimum launch intake air temp.
Alcohol engines run best at operating temps above 160F. So the engine should be warmed before pulling to the line. Unless, the cooling system has been cut back, and/or the tuneup is such that you must be cooler at the start of the run to avoid being overheated by the end of the run.
I wonder how much boost and intake heat has been built up by the launch time of a typical supercharged alcohol engine? That would be some good information to use to determine what a target intake air temp might be.
Donnie,
Put a heat exchanger in the downpipe and run the HOT water to the intercooler! EGT has to be 1k degree or so. With methanol, it might be less but would still be much more that coolant temp.
Or, put a box around the headers or use a double-walled down-pipe and divert the hot air into the turbo but doubt there would be enough flow potential there to help. Remember the old air intake preheaters from the 70's that drew air off the exhaust manifold to pre-heat the air to the carbs? Those were the days!!
Conrad
Put a heat exchanger in the downpipe and run the HOT water to the intercooler! EGT has to be 1k degree or so. With methanol, it might be less but would still be much more that coolant temp.
Or, put a box around the headers or use a double-walled down-pipe and divert the hot air into the turbo but doubt there would be enough flow potential there to help. Remember the old air intake preheaters from the 70's that drew air off the exhaust manifold to pre-heat the air to the carbs? Those were the days!!
Conrad
Could the intercooler be used as a way to stabilize engine temperature before a run by circulating the engine cooling water through it and eliminating the need for a radiator? The airflow through the intercooler would help cool the engine coolant as it's heated on it's way to the intake. Then all that's needed is a way to bypass the engine cooling system water and introduce another cooling water source to the intercooler at the start and during the run.
The whole idea here is to maintain a tight temperature range of the intake air to optimize the vaporization of the alcohol at the start of the run, while allowing maximum hp on the top end.
Good input, Conrad. It's keeping the wheels turning.
To effectively cool the intercooler within a short window of time, after engine cooling water has been circulating through it, the other intercooler water system would need to be well iced. I would think a good time to switch the water would be when the transbrake is set during staging. It really would depend on how quickly the iced water could start changing the temperature of the intercooler. It would be best if it could start changing temperature at the point that boost is halfway built up.
The whole idea here is to maintain a tight temperature range of the intake air to optimize the vaporization of the alcohol at the start of the run, while allowing maximum hp on the top end.
Good input, Conrad. It's keeping the wheels turning.
To effectively cool the intercooler within a short window of time, after engine cooling water has been circulating through it, the other intercooler water system would need to be well iced. I would think a good time to switch the water would be when the transbrake is set during staging. It really would depend on how quickly the iced water could start changing the temperature of the intercooler. It would be best if it could start changing temperature at the point that boost is halfway built up.
six shooter
Quiet Member
- Joined
- May 26, 2001
- Messages
- 135
Is your engine water pump on all the time ? How much heat does it build on a pass? Are you able to make a pass with the water pump off and a cold I/C?
Yes, I have the water pump on all the time. I've gotten in the habit of making sure the pump is turned on after start up. If I started turning the pump on and off with the engine running, sure enough I would forget about the pump, I would overheat the engine and the overflow tank would make a nice mess for me to clean up. Been there, done that.Is your engine water pump on all the time ? How much heat does it build on a pass? Are you able to make a pass with the water pump off and a cold I/C?
I have no radiator fan. With my new fueling stradegy, if I sit long enough at an idle the engine temp will climb to 90C and stabilize between 87 and 91C. I use the coolant temp fuel correction and add 5% fuel at 90C to cool the engine.
I'll have to check the datalogs to see how much heat I have at the end of the runs. Since I'm still running a radiator and with the airflow through the radiator during a pass, if there is any increase, it's very small. I'll get the latest IAT temp at start and end of run too. I measure IAT about 18" before the TB. That way, I get a good idea as to whether I need to start throwing some IAT fuel correction at the engine. Back to the engine temp, when I pull back into the pits the engine temp is at 180 F.
I haven't tried to make a pass with the water pump off. I like to keep it on so that hot spots don't develop in the cooling system. Keeps the overall engine temp more uniform. I've found that as long as the engine temp is over 165F at the start of the run, the fuel will burn clean. Colder than that and you can sense that there's some fuel fall out just from blipping the throttle. Engine temp fuel correction has to be used at 60C and below. The correction stabilizes at 70C and then must be added in again at 80C and beyond at a steep ramping rate. The engine heat definitely helps alcohol fuel atomization.
The last time I tried icing the intercooler, I blew up Alky version 1.0 at Carlsbad and left a pretty big mess. I can't blame the icing, the tuneup was way off.
The ECT from start of run to finish, 84 - 89C. Water pump on. No fan.
The IAT from start of run to finish, 32 - 51C. Intercooler with ambient temp water. No circulation.
Judging by the a/f strength throughout the run, it appears that temp correction is necessary soon after the shift to 3rd. Maybe an additional 1% tied to the IAT at 50C.
The IAT from start of run to finish, 32 - 51C. Intercooler with ambient temp water. No circulation.
Judging by the a/f strength throughout the run, it appears that temp correction is necessary soon after the shift to 3rd. Maybe an additional 1% tied to the IAT at 50C.
Comparing the IAT rise from one of the datalogs with the old turbo;
Old turbo: Start of run to finish, 98F to 140F. A rise of 42F. Boost level was 260 kPa.
New turbo: Start of run to finish, 89.6F to 123.8F. A rise of 34.2F. Boost level was 300 kPa through all of second and third gear.
These are 1/8 mile runs.
Old turbo: Start of run to finish, 98F to 140F. A rise of 42F. Boost level was 260 kPa.
New turbo: Start of run to finish, 89.6F to 123.8F. A rise of 34.2F. Boost level was 300 kPa through all of second and third gear.
These are 1/8 mile runs.
Building a shield around the exhaust and drawing heat from it to feed the turbo inlet does sound like a good idea. But, might it be a trade off? Might it cool the exhaust enough to affect turbo spool? The end mission is to spool the turbo as quickly as possible. Exhaust heat is a very important component to that goal.
Ahhh! Around the downpipe. Heat loss at the downpipe is preferred. Good thinking Hot Air.
Ahhh! Around the downpipe. Heat loss at the downpipe is preferred. Good thinking Hot Air.
Time to start tuning in the nitrous hit.
Tuning notes.
The base fuel map has been dialed in. The mixture that I settled on as the best power ratio is 4.82:1. Best engine temp 160 to 180F. At least above 152F.
Nitrous tuning has started. I did some initial hits while on the transbrake that lastest less than one second.
Stall just before the nitrous hit, 2,458 rpm @ 96.8 kPa.
Stall after the nitrous hit at the .256 second mark, 3,520 rpm @ 99.3 kPa.
So the turbo is at least making some boost (1/3 psi) at 3,520 rpm. A glimmer of hope.
Nitrous tune specs.
Jetting: 6@25N, 6@26F.
Fuel pressure: 45 psi.
HP rating: 243. Most likely less, due to the fat mixture.
N/F ratios: 1.53:1 @ 800 psi bottle pressure. 1.75:1 @ 1,050 psi bottle pressure. Bottom line, FAT! No missing encountered during initial tests @ 750 to 800 psi. Cold day.
Jet flow correction factors: 1.0542N, 0.9913F.
Timing retard: 18 degrees of constant retard throughout rpm band while nitrous is on, starting at 2,440 rpm. In the future, look to get back 8 degrees by 5,400 rpm.
Started with 16 degrees of retard, then moved to 18 degrees with no difference in stall speed. If anything, stall increased. But, I did purge first on that particular test. Timing just before nitrous retard, 31 degrees BTDC @ 2,440 rpm, 96.8 kPa.
The delay time for turning off the fuel solenoid, after the nitrous solenoid has shut down, was moved down from .9 to .2 seconds. At .9 the engine was pretty well flooded with fuel. Nothing noticeable on the O2 reading. At .2 the flooding was still there, but much less and manageable. Again, nothing noticeable on the O2 reading. At .1 a lean backfire was experienced just as I came off WOT which also deactivates the nitrous system. Again, nothing noticeable on the O2 reading. Went back with .2 second delay and that's where I'll start the full run testing. May try .150 delay in the future.
Next step, track testing with the nitrous limited to 2.5 seconds on-time. Inspect plugs. If things look good, increase on-time in small steps. Look for missing, which will be a sign that the mixture is too fat. See if the nitrous off point should be moved lower, to say 8 psi, rather than have it stay on until 16 psi. Maybe use the timer alone to limit nitrous on time.
Plugs pre-nitrous show 1/2 thread heat and less than 1/2 groung strap heat.
Plugs did not change with the initial short hits on the transbrake.
Tuning notes.
The base fuel map has been dialed in. The mixture that I settled on as the best power ratio is 4.82:1. Best engine temp 160 to 180F. At least above 152F.
Nitrous tuning has started. I did some initial hits while on the transbrake that lastest less than one second.
Stall just before the nitrous hit, 2,458 rpm @ 96.8 kPa.
Stall after the nitrous hit at the .256 second mark, 3,520 rpm @ 99.3 kPa.
So the turbo is at least making some boost (1/3 psi) at 3,520 rpm. A glimmer of hope.
Nitrous tune specs.
Jetting: 6@25N, 6@26F.
Fuel pressure: 45 psi.
HP rating: 243. Most likely less, due to the fat mixture.
N/F ratios: 1.53:1 @ 800 psi bottle pressure. 1.75:1 @ 1,050 psi bottle pressure. Bottom line, FAT! No missing encountered during initial tests @ 750 to 800 psi. Cold day.
Jet flow correction factors: 1.0542N, 0.9913F.
Timing retard: 18 degrees of constant retard throughout rpm band while nitrous is on, starting at 2,440 rpm. In the future, look to get back 8 degrees by 5,400 rpm.
Started with 16 degrees of retard, then moved to 18 degrees with no difference in stall speed. If anything, stall increased. But, I did purge first on that particular test. Timing just before nitrous retard, 31 degrees BTDC @ 2,440 rpm, 96.8 kPa.
The delay time for turning off the fuel solenoid, after the nitrous solenoid has shut down, was moved down from .9 to .2 seconds. At .9 the engine was pretty well flooded with fuel. Nothing noticeable on the O2 reading. At .2 the flooding was still there, but much less and manageable. Again, nothing noticeable on the O2 reading. At .1 a lean backfire was experienced just as I came off WOT which also deactivates the nitrous system. Again, nothing noticeable on the O2 reading. Went back with .2 second delay and that's where I'll start the full run testing. May try .150 delay in the future.
Next step, track testing with the nitrous limited to 2.5 seconds on-time. Inspect plugs. If things look good, increase on-time in small steps. Look for missing, which will be a sign that the mixture is too fat. See if the nitrous off point should be moved lower, to say 8 psi, rather than have it stay on until 16 psi. Maybe use the timer alone to limit nitrous on time.
Plugs pre-nitrous show 1/2 thread heat and less than 1/2 groung strap heat.
Plugs did not change with the initial short hits on the transbrake.
In an effort to control the size of 'the wall' the aux fuel solenoid has been moved directly to the end of the aux fuel rail at the back of the intake plenum. This cuts out a fair length of -6 line between the aux solenoid and the aux fuel rail. I figure the space volume that needs to be purged of air after the aux solenoid is energized has been cut to around 1/2 from this change.
Before the nitrous test runs, I need to perform some runs off the nitrous and adjust the fuel map ('the wall') for the new aux fuel solenoid location.
Before the nitrous test runs, I need to perform some runs off the nitrous and adjust the fuel map ('the wall') for the new aux fuel solenoid location.
Picking a new T/C stall speed.
I'm getting close to the point of picking a new stall speed for the T/C. Past tests with the open turbine housing gave the impression that a stall speed between 4500 to 5200 rpm would work out well. With the split turbine housing and some more work with fuel mixtures and timing, hopefully the new target stall speed can be brought down a bit. We'll see.
I'm getting close to the point of picking a new stall speed for the T/C. Past tests with the open turbine housing gave the impression that a stall speed between 4500 to 5200 rpm would work out well. With the split turbine housing and some more work with fuel mixtures and timing, hopefully the new target stall speed can be brought down a bit. We'll see.
Dusty Bradford
Well-Known Member
- Joined
- May 24, 2001
- Messages
- 5,802
Do you have variable stall?
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