12-28-2010, 07:28 PM
When I first put the supercharger kit together, I knew that the header would not be able to be used, due to its need for more fuel. We knew this based on what happened in normally aspirated mode, and how much fuel needed to be added for that application. It would only be worse supercharged. The injectors were already maxxed out up top, and there was no room for more fuel to be added. Adding pressure with an AFPR didn't help, and in fact made things worse, as it was like squeezing off your garden hose. Sure, you get more pressure, but you get less flow, and flow is what it is all about. So, the decision was made that the header could not be used in conjunction with the supercharger kit. It was disappointing and complicated for some of the guys, but I was quite adamant about this, as I wanted to keep within the design parameters, which included no injector change, no fuel system changes, and keeping the price down.
Still, Pete being the nut he is, was determined to see if it could be done. So he stuck in some bigger injectors on one of the cars getting the kit. While they provided more fuel, and after some fiddling, the mapping of one of my chips was fairly close in the midrange, it still left some areas that were real problems.
This painted me into a bit of a corner, as I did not want one of my kits out there having problems, and it was sure to do that. Yes, the car is quite fast, but it still isn't right, and there are very real problems with the tuning of it.
Knowing that I needed to handle this one way or another, I installed the header on my car, and sure enough, not nearly enough fuel, but I could immediately tell that it flowed better, and ran freer up top. More power was clearly available.
This led me to try what Pete was trying, and then get in and see if I could tune it. I plugged in the larger injectors, complete with the mod that Max does to them to make them fit. They however did exactly as I expected, and flooded things too much down low, and at the same time made things too lean off idle when you stabbed it. This was all due to the increased flow of the header, and the velocity of the gasses over the O2 sensor.
The cold start was also insanely fat. So rich in fact that it filled my garage with black smoke. Not good. This would create all kinds of long term problems, especially on a car that was not driven often. Ring wash was certain to happen, and the oil would quickly become fouled with fuel.
Across the board it is too rich, and needs to be cleaned up, but that is manageable, and I would need to spend a couple of days mapping that out.
The bigger and more dangerous issue was the upper end was also still lean. This means having to increase fuel even more, meaning even more clean up down low.
Problems now identified, I moved on to trying to solve them.
The cold start issue persists, and looks like I cannot resolve it with the facilities and resources I have. There are 143 maps to control the fuel and timing of the engine, some of which control the cold start. The problem is that there is no way of knowing which ones interact, and how. I would need to go into a lab to find out.
To tune the rest of this, I will have rework the rest of the part throttle mapping, and then the WOT mapping. When that is done, I get to come back and do a final round of part throttle mapping. Then I get to go and drive it and record the temps and such and make sure it is reasonably safe, before I can then call it "done".
In the end, I think I could get it, but it will not be clean enough to pass any sort of emissions tests. I just don't have the facilities to generate the conditions needed to map for all conditions, which would be needed to pass emissions. It will run fine, but will probably be too rich to pass. The cold start issue would remain though.
The application gets a bit dodgy as this becomes a very real problem for any car that would sit between drives. The rings would contract, and the fuel would end up in the oil while they were warming up to expand again. This would mean more frequent oil changes, and cold-blooded starts. If you drove the car on a very regular basis, this would be lessened, and it would be very much like having an older hot rod. It would be tons of fun to drive, but a bit temperamental. This consequently will really be a track application.
To give you an idea of what would be involved to get more power:
1. It will require the header from RS Barn (see their site for pricing).
2. It will require the AFPR, which will then have to be set to a specific pressure (so you'll need a gauge to do that or have a shop do it).
3. It will require the RS Barn cat-back or very close facsimile (see their site for pricing). A system that is too free flowing will not run right, nor will one that is too choked up. It really needs to flow about the same as the RS Barn system. Big pipes, or twin pipes, or gutted OEM stuff won't work.
4. It will require the modified injectors (see RS Barn for pricing).
5. It will require the new chip for this setup. (likely to be $350)
6. You absolutely have to have a functioning O2 sensor in there.
7. Under no circumstances will this pass the visual inspections or the emissions inspections of any state that has them.
8. You will likely have to sit and warm up the car before you can move, taking about a minute.
9. You will likely not get more than 3000 miles from your oil.
10. Your fuel economy will drop about 20% from what you would get with a chipped car, and about 40% from stock.
If I proceed, I will only be selling the chip, and the rest will come from RS Barn. If you have to buy it all though, you are looking at about $3k.
The one thing I do know is that I will not be responsible for any engine damage as a result of running this setup. I still think it is less than a stellar idea, but I also understand that some people just want more.
Boost will not be increased. I already tried that. The intake temps are already at the safe limits. Increasing boost, even 1 pound, would require an intercooler and a complete remap.
Power increases should be a good 15hp up top and at least 10 ft/lbs across the board from just under 3k on up. It could be a bit more. Of course I would provide dyno charts to show everything.
Before I go any farther with this though, I really need to get a handle on just how many people would even be interested. The time investment and out of pocket cost is significant. I won't be running this on my own car, so my motivation is not there if nobody wants this.
Still, Pete being the nut he is, was determined to see if it could be done. So he stuck in some bigger injectors on one of the cars getting the kit. While they provided more fuel, and after some fiddling, the mapping of one of my chips was fairly close in the midrange, it still left some areas that were real problems.
This painted me into a bit of a corner, as I did not want one of my kits out there having problems, and it was sure to do that. Yes, the car is quite fast, but it still isn't right, and there are very real problems with the tuning of it.
Knowing that I needed to handle this one way or another, I installed the header on my car, and sure enough, not nearly enough fuel, but I could immediately tell that it flowed better, and ran freer up top. More power was clearly available.
This led me to try what Pete was trying, and then get in and see if I could tune it. I plugged in the larger injectors, complete with the mod that Max does to them to make them fit. They however did exactly as I expected, and flooded things too much down low, and at the same time made things too lean off idle when you stabbed it. This was all due to the increased flow of the header, and the velocity of the gasses over the O2 sensor.
The cold start was also insanely fat. So rich in fact that it filled my garage with black smoke. Not good. This would create all kinds of long term problems, especially on a car that was not driven often. Ring wash was certain to happen, and the oil would quickly become fouled with fuel.
Across the board it is too rich, and needs to be cleaned up, but that is manageable, and I would need to spend a couple of days mapping that out.
The bigger and more dangerous issue was the upper end was also still lean. This means having to increase fuel even more, meaning even more clean up down low.
Problems now identified, I moved on to trying to solve them.
The cold start issue persists, and looks like I cannot resolve it with the facilities and resources I have. There are 143 maps to control the fuel and timing of the engine, some of which control the cold start. The problem is that there is no way of knowing which ones interact, and how. I would need to go into a lab to find out.
To tune the rest of this, I will have rework the rest of the part throttle mapping, and then the WOT mapping. When that is done, I get to come back and do a final round of part throttle mapping. Then I get to go and drive it and record the temps and such and make sure it is reasonably safe, before I can then call it "done".
In the end, I think I could get it, but it will not be clean enough to pass any sort of emissions tests. I just don't have the facilities to generate the conditions needed to map for all conditions, which would be needed to pass emissions. It will run fine, but will probably be too rich to pass. The cold start issue would remain though.
The application gets a bit dodgy as this becomes a very real problem for any car that would sit between drives. The rings would contract, and the fuel would end up in the oil while they were warming up to expand again. This would mean more frequent oil changes, and cold-blooded starts. If you drove the car on a very regular basis, this would be lessened, and it would be very much like having an older hot rod. It would be tons of fun to drive, but a bit temperamental. This consequently will really be a track application.
To give you an idea of what would be involved to get more power:
1. It will require the header from RS Barn (see their site for pricing).
2. It will require the AFPR, which will then have to be set to a specific pressure (so you'll need a gauge to do that or have a shop do it).
3. It will require the RS Barn cat-back or very close facsimile (see their site for pricing). A system that is too free flowing will not run right, nor will one that is too choked up. It really needs to flow about the same as the RS Barn system. Big pipes, or twin pipes, or gutted OEM stuff won't work.
4. It will require the modified injectors (see RS Barn for pricing).
5. It will require the new chip for this setup. (likely to be $350)
6. You absolutely have to have a functioning O2 sensor in there.
7. Under no circumstances will this pass the visual inspections or the emissions inspections of any state that has them.
8. You will likely have to sit and warm up the car before you can move, taking about a minute.
9. You will likely not get more than 3000 miles from your oil.
10. Your fuel economy will drop about 20% from what you would get with a chipped car, and about 40% from stock.
If I proceed, I will only be selling the chip, and the rest will come from RS Barn. If you have to buy it all though, you are looking at about $3k.
The one thing I do know is that I will not be responsible for any engine damage as a result of running this setup. I still think it is less than a stellar idea, but I also understand that some people just want more.
Boost will not be increased. I already tried that. The intake temps are already at the safe limits. Increasing boost, even 1 pound, would require an intercooler and a complete remap.
Power increases should be a good 15hp up top and at least 10 ft/lbs across the board from just under 3k on up. It could be a bit more. Of course I would provide dyno charts to show everything.
Before I go any farther with this though, I really need to get a handle on just how many people would even be interested. The time investment and out of pocket cost is significant. I won't be running this on my own car, so my motivation is not there if nobody wants this.
94 Midnight Metallic Blue Cab Porsche 968 w/deviating cashmere/black interior and WAY too many mods to list - thanks to eric for creating www.968forums.com
"It isn't nearly as expensive to do it right as it is to do it wrong."
(This post was last modified: 12-28-2010, 09:11 PM by flash.)
