968 Supercharger Kit Development
10-07-2010, 09:41 AM
#842
Nordschleife Master
Yes, I'm using hood pins.
Went to the track yesterday. It was a cool morning, in the low 50's when I hit the track. First session was to determine if the car would stop, turn, you know, the important things since this was the maiden voyage. The one thing I noticed was that my heal/toe was way off, I was zigging the engine for too much. At first I thought that maybe something was different ergonomically, but soon realized that that was not the issue. The issue was, the engine just spools up so much quicker that before
For the second session I decided it was time to see what the engine had, mind you I was not going to go above 5500 rpms due to the fueling problem. The acceleration is fantastic, much quicker than in the old car (which was around 50lbs lighter) but very controllable. I could easily break the rear wheels loose coming out of corners but only if is "mashed" the pedal. With a smooth roll on there is no issue other than that good feeling being pushed back into the seat.
An issue that I had was that my wide-band A/F meter crapped out on me during the first run. After the second run, I checked A/F the old fashioned way, by pulling some plugs. Unfortunately, they indicated a far too lean condition for my taste. As I am maxed out on the FMU, I decided the prudent thing to do was to call it quits for the day, no reason to kill my engine. I believe that the car was running even leaner than on the dyno as it was a very cool morning and I'm guessing I was moving a lot of cool dense air!
When I got home I had a package in the mail, my new injectors had arrived, if only they had shown up the day before
I installed them last night and immediately had to back off on the FMU baseline settings as it was running too rich (based on exhaust smell and very lumpy idle). Once that was backed off significantly, the car idled nicely. I'll get the car back to the dyno next week as I have a track weekend a Barber on the 16th.
All-in-all, I'm pleased with the SC at this point. I believe that with the new injectors I'll be able to push this thing to 6500 rpms and find a bit more HP. After my November race, I'll likely start looking into a stand alone system so that I can tweak the power even more
Went to the track yesterday. It was a cool morning, in the low 50's when I hit the track. First session was to determine if the car would stop, turn, you know, the important things since this was the maiden voyage. The one thing I noticed was that my heal/toe was way off, I was zigging the engine for too much. At first I thought that maybe something was different ergonomically, but soon realized that that was not the issue. The issue was, the engine just spools up so much quicker that before
For the second session I decided it was time to see what the engine had, mind you I was not going to go above 5500 rpms due to the fueling problem. The acceleration is fantastic, much quicker than in the old car (which was around 50lbs lighter) but very controllable. I could easily break the rear wheels loose coming out of corners but only if is "mashed" the pedal. With a smooth roll on there is no issue other than that good feeling being pushed back into the seat. An issue that I had was that my wide-band A/F meter crapped out on me during the first run. After the second run, I checked A/F the old fashioned way, by pulling some plugs. Unfortunately, they indicated a far too lean condition for my taste. As I am maxed out on the FMU, I decided the prudent thing to do was to call it quits for the day, no reason to kill my engine. I believe that the car was running even leaner than on the dyno as it was a very cool morning and I'm guessing I was moving a lot of cool dense air!
When I got home I had a package in the mail, my new injectors had arrived, if only they had shown up the day before
I installed them last night and immediately had to back off on the FMU baseline settings as it was running too rich (based on exhaust smell and very lumpy idle). Once that was backed off significantly, the car idled nicely. I'll get the car back to the dyno next week as I have a track weekend a Barber on the 16th. All-in-all, I'm pleased with the SC at this point. I believe that with the new injectors I'll be able to push this thing to 6500 rpms and find a bit more HP. After my November race, I'll likely start looking into a stand alone system so that I can tweak the power even more
10-07-2010, 08:04 PM
#844
Nordschleife Master
10-11-2010, 06:43 PM
#845
Addict
Rennlist Member
Rennlist Member
I installed them last night and immediately had to back off on the FMU baseline settings as it was running too rich (based on exhaust smell and very lumpy idle). Once that was backed off significantly, the car idled nicely. I'll get the car back to the dyno next week as I have a track weekend a Barber on the 16th.
10-12-2010, 01:13 AM
#846
Three Wheelin'
The FMU is an AFPR with adjustable gain and "knee" point. It adjusts the same as an AFPR for idle.
EDIT: incorrect - see post below
EDIT: incorrect - see post below
Last edited by mikey_audiogeek; 10-12-2010 at 09:21 PM. Reason: operator error!
10-12-2010, 08:57 AM
#847
Nordschleife Master
We needed more fuel so we completely closed the FMU while on the dyno and left if closed (remember, I was running way lean). I also closed down my AFPR, we even tried clamping the return hose for a bit 
With the larger injectors I seem to be getting plenty of gas and have both the FMU and AFPR fairly open. I also ordered a higher capacity fuel pump but am wondering whether or not I will need it now. I'll be on the dyno this week, so time will tell. Got to get this thing sorted asap as I'm at Barber Motorsports to instruct and test & tune this weekend
With the larger injectors I seem to be getting plenty of gas and have both the FMU and AFPR fairly open. I also ordered a higher capacity fuel pump but am wondering whether or not I will need it now. I'll be on the dyno this week, so time will tell. Got to get this thing sorted asap as I'm at Barber Motorsports to instruct and test & tune this weekend
10-12-2010, 09:17 AM
#848
Addict
Rennlist Member
Rennlist Member
If however you have an AFPR in place of the stocker and that is set low you would have base fuel pressure control at the FMU. I don't know how Tim is set up, what I would be inclined to do is use an AFPR to set up open-loop off-boost mixture and the RRFPR/FMU for on boost.
For whatever reason my car seems OK with what I assume are the bigger injectors, a touch rich in open loop but that is reassuring.
-Joel.
10-12-2010, 10:07 AM
#849
Nordschleife Master
I don't know how Tim is set up, what I would be inclined to do is use an AFPR to set up open-loop off-boost mixture and the RRFPR/FMU for on boost.
For whatever reason my car seems OK with what I assume are the bigger injectors, a touch rich in open loop but that is reassuring.
-Joel.
For whatever reason my car seems OK with what I assume are the bigger injectors, a touch rich in open loop but that is reassuring.
-Joel.
10-12-2010, 11:35 AM
#850
Developer
Thread Starter
Tuning the FMU
The Fuel Management Unit (FMU) that we use has two adjustment points, the tip in point, and the rising rate. There are only 2 screws to adjust, and it is very easy. (Other brands use springs and shims and its a mess).
The tip in setting is the point at which the FMU will start to raise the fuel pressure. We do not want to raise the fuel pressure at idle - there is no boost so there is no need for extra fuel. Similarly, we don’t need to add fuel to about 2800 rpm as the supercharger has not gotten into its compressor map yet and is not making boost.
The FMU "sees" boost in the manifold via a signal line - a vacuum hose that connects it to the intake manifold. This is how it senses whether you are in boost or not.
When the FMU starts to sense boost (on this kit, about 3200 rpm) THEN we need to add more fuel to match the increase in air.
The large screw at the top of the FMU does this - it sets the initial point where the FMU will start to work.
Then we see the rising rate screw - the little brass needle screw on the side. This controls how fast the FMU advances. That is, once it is activated, how quickly do you want it to increase the fuel pressure - at what rate?
We recommend to start by dialing it gently shut. This gives maximum rising rate.
TUNING the FMU:
If the boost comes in (as seen on a boost gauge) and the A/F has not started to go rich, your tip in screw is too far out - the FMU is lagging behind the boost.
If the A/F ratio is too rich even when the boost is not yet in (below 2800 rpm, for example), the tip in screw is too far in. Your just dumping fuel and fouling spark plugs.
If the A/F gauge starts to move towards richer just as you notice the boost start to come in - The tip in screw is set correctly. Lock it in place with the jam nut provided.
Once the Tip in screw is set, you may now tweak with the rising rate screw.
Start with the rising rate screw gently shut all the way. If you notice you have too much fuel at top end, turn the rising screw out a little and try again.
This does not effect the tip-in point, just the rate the fuel pressure rises with boost.
For gasoline, Stoichiometric tuning for max gas mileage and lowest emissions is 14.7:1
However, maximum HP is produced at 12.5:1 Air/Fuel ratio for gasoline.
For safety (to help prevent detonation and make your head gaskets last longer) we recommend you tune for 12.0:1 A/F under boost if you can get it. Make 12:1 or 12.3:1 A/F under boost your goal and you will have a long and trouble-free life with your engine.
Be aware that some fuel systems cannot supply 12:1 until the computers and injectors are swapped out with new ones.
The tip in setting is the point at which the FMU will start to raise the fuel pressure. We do not want to raise the fuel pressure at idle - there is no boost so there is no need for extra fuel. Similarly, we don’t need to add fuel to about 2800 rpm as the supercharger has not gotten into its compressor map yet and is not making boost.
The FMU "sees" boost in the manifold via a signal line - a vacuum hose that connects it to the intake manifold. This is how it senses whether you are in boost or not.
When the FMU starts to sense boost (on this kit, about 3200 rpm) THEN we need to add more fuel to match the increase in air.
The large screw at the top of the FMU does this - it sets the initial point where the FMU will start to work.
Then we see the rising rate screw - the little brass needle screw on the side. This controls how fast the FMU advances. That is, once it is activated, how quickly do you want it to increase the fuel pressure - at what rate?
We recommend to start by dialing it gently shut. This gives maximum rising rate.
TUNING the FMU:
If the boost comes in (as seen on a boost gauge) and the A/F has not started to go rich, your tip in screw is too far out - the FMU is lagging behind the boost.
If the A/F ratio is too rich even when the boost is not yet in (below 2800 rpm, for example), the tip in screw is too far in. Your just dumping fuel and fouling spark plugs.
If the A/F gauge starts to move towards richer just as you notice the boost start to come in - The tip in screw is set correctly. Lock it in place with the jam nut provided.
Once the Tip in screw is set, you may now tweak with the rising rate screw.
Start with the rising rate screw gently shut all the way. If you notice you have too much fuel at top end, turn the rising screw out a little and try again.
This does not effect the tip-in point, just the rate the fuel pressure rises with boost.
For gasoline, Stoichiometric tuning for max gas mileage and lowest emissions is 14.7:1
However, maximum HP is produced at 12.5:1 Air/Fuel ratio for gasoline.
For safety (to help prevent detonation and make your head gaskets last longer) we recommend you tune for 12.0:1 A/F under boost if you can get it. Make 12:1 or 12.3:1 A/F under boost your goal and you will have a long and trouble-free life with your engine.
Be aware that some fuel systems cannot supply 12:1 until the computers and injectors are swapped out with new ones.
Last edited by Carl Fausett; 10-12-2010 at 11:53 AM.
10-12-2010, 11:59 AM
#851
Developer
Thread Starter
One more note: if you install an Air/Fuel gauge (temporarilly or permanently) you may notice the needle will sweep constantly at partial throttle - like cruising on the interstate for example. This is normal, and demonstartes the feedback loop in your cars computer system and the O2 sensor.
It will sweep over 14.7:1 all the time as it constantly adjusts the tune according to the load (the gear you are in, weight and rolling resistance of the vehicle, incline you are one, engine rpms, and other factors).
You will note as you step into the throttle the moment the "sweep" stops and the needle steadies up - that is the Tip In point where the FMU has now taken over and over-ridden the computer. That moment should correspond with the first increase in boost or your first movement of the gas pedal from cruising to accelerating.
If it does, you have the Tip-in screw adjusted correctly.
It will sweep over 14.7:1 all the time as it constantly adjusts the tune according to the load (the gear you are in, weight and rolling resistance of the vehicle, incline you are one, engine rpms, and other factors).
You will note as you step into the throttle the moment the "sweep" stops and the needle steadies up - that is the Tip In point where the FMU has now taken over and over-ridden the computer. That moment should correspond with the first increase in boost or your first movement of the gas pedal from cruising to accelerating.
If it does, you have the Tip-in screw adjusted correctly.
10-12-2010, 09:17 PM
#852
Three Wheelin'
But it is downstream of the stock FPR so it cannot *lower* idle fuel pressure that is controlled by the stock FPR.
If however you have an AFPR in place of the stocker and that is set low you would have base fuel pressure control at the FMU. I don't know how Tim is set up, what I would be inclined to do is use an AFPR to set up open-loop off-boost mixture and the RRFPR/FMU for on boost.
For whatever reason my car seems OK with what I assume are the bigger injectors, a touch rich in open loop but that is reassuring.
-Joel.
If however you have an AFPR in place of the stocker and that is set low you would have base fuel pressure control at the FMU. I don't know how Tim is set up, what I would be inclined to do is use an AFPR to set up open-loop off-boost mixture and the RRFPR/FMU for on boost.
For whatever reason my car seems OK with what I assume are the bigger injectors, a touch rich in open loop but that is reassuring.
-Joel.
Also to Carl for the writeup on tuning the FMU - very clear and easy to understand.
Cheers,
Mike
10-12-2010, 10:37 PM
#853
Nordschleife Master
i'm off to the dyno again tomorrow night. In addition to the larger injectors, I added a high flow pump (Welbro 392) to make sure the fuel is flowing. While I was back there I put in a new fuel filter, just in case. Welded a bung on the exhaust so that I don't have to remove the supertrapp discs to measure A/F. I'm certainly getting fuel as this point, let's hope that it is not too much
10-13-2010, 10:56 AM
#854
Developer
Thread Starter
You cant have too much fuel supply! Thats a good thing, then you just adjust it at the injector with the tune.
The fuel pump you have installed is a honey. That should be the end to that issue.
The fuel pump you have installed is a honey. That should be the end to that issue.
10-13-2010, 11:41 AM
#855
Nordschleife Master
(other than with fuel pressure) I understand that this is going to need to change, now where did I put that lottery ticket 
The pump looks great and you can't beat the cost at just over $100. Compare that to buying a 944/968 pump for $250. The best thing is that the outflow one-way valve from our pumps is a direct fit!
Last edited by Lemming; 10-13-2010 at 12:19 PM.